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Transmembrane protein 108 inhibits the proliferation and myelination of oligodendrocyte lineage cells in the corpus callosum

Transmembrane protein 108 inhibits the proliferation and myelination of oligodendrocyte lineage... Background: Abnormal white matter is a common neurobiological change in bipolar disorder, and dysregulation of myelination in oligodendrocytes (OLs) is the cause. Transmembrane protein 108 (Tmem108), as a susceptible gene of bipolar disorder, is expressed higher in OL lineage cells than any other lineage cells in the central nervous system. Moreover, Tmem108 mutant mice exhibit mania-like behaviors, belonging to one of the signs of bipolar disorder. However, it is unknown whether Tmem108 regulates the myelination of the OLs. Results: Tmem108 expression in the corpus callosum decreased with the development, and OL progenitor cell proliferation and OL myelination were enhanced in the mutant mice. Moreover, the mutant mice exhibited mania-like behavior after acute restraint stress and were susceptible to drug-induced epilepsy. Conclusions: Tmem108 inhibited OL progenitor cell proliferation and mitigated OL maturation in the corpus cal- losum, which may also provide a new role of Tmem108 involving bipolar disorder pathogenesis. Keywords: Tmem108, Oligodendrocyte (OL), Myelination, Corpus callosum (CC), Bipolar disorder (BD) Introduction radial diffusivity [3–5]. Abnormal white matter connec - Bipolar disorder (BD) is a severe mental disease charac- tivity may be associated with BD pathophysiology [4, 6], terized by manic states being usually interspersed with and elevated rates of white matter hyperintensities are periods of depression [1], affecting 1–1.5% of the popu - widely observed in BD [3–5]. lation [1, 2]. Aberrant white matter microstructure is The corpus callosum (CC) is the brain’s major white proposed as a mechanism underlying BD, including the matter fiber tract [6, 7], containing most axonal trans- dimension of irritability and widespread increases in missions between the two cerebral hemispheres. The CC is among the last brain structures to complete myelina- tion [8], which is also a period accompanying the peak *Correspondence: hailipan@qq.com; wsqi@ncu.edu.cn onset of BD [9]. Anatomical abnormalities in the CC have Yongqiang Wu and Yanzi Zhong have contributed equally to this been reported in magnetic resonance imaging studies research Institute of Life Science, Nanchang University, Nanchang 330031, in BD patients, possibly because of altered myelination Jiangxi, China leading to impaired interhemispheric communication Neurological Institute of Jiangxi Province and Department of Neurology, [10]. Changes in area and thickness in the CC have been Jiangxi Provincial People’s Hospital, The First Affiliated Hospital of Nanchang Medical College, Nanchang 330006, Jiangxi, China reported in BD, and neuropathological data and imaging Full list of author information is available at the end of the article © The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. The Creative Commons Public Domain Dedication waiver (http:// creat iveco mmons. org/ publi cdoma in/ zero/1. 0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Wu et al. Molecular Brain (2022) 15:33 Page 2 of 13 suggest possible abnormalities in myelination and glial with the β-galactosidase/neomycin cassette. Tmem108 function [2, 9]. Given the strong genetic underpinnings mutant mice in the paper were Tmem108-LacZ homozy- of both BD and white matter microstructure, such white gous (Tmem108 –/–). Mice were fed in a room 12-h matter aberrations may be a disease marker and an endo- light/dark cycle, at 22–25℃, with ad  libitum access to phenotype of BD [3, 11]. rodent chow diet and clean water. The experimental pro - Several genome-wide association studies (GWAS) sug- tocols were performed according to the "guidelines for gest that Tmem108 is a susceptible gene of BD [12–14], the care and use of experimental animals" issued by Nan- and the relevant single nucleotide polymorphism (SNP) chang University for research about vertebrate animals. site is not in the coding region of Tmem108, which is For in  vivo experiment, surgery was performed with speculated that the SNP may affect its expression [14, sodium pentobarbital anesthesia (50  mg/kg, intraperi- 15]. Strikingly, the recent GWAS screened BD risk loci in toneal injection), and efforts were executed to minimize the Han Chinese population, covering 1822 BD patients suffering and reduce the animal number. After the termi - and 4650 control individuals, and the data was replicated nal experiments, mice were euthanized by carbon dioxide analysis. After finally multiple analyses between Han Chi - inhalation. nese and European populations, a new SNP (rs9863544) in BD patients were found, locating in the upstream Reagents regulatory region of the Tmem108 gene [14]. Tmem108 X-gal (5-Bromo-4-chloro-3-indolyl-β-d -galactopyranoside) expression change may be one of the onset reasons for was purchased from Sigma-Aldrich (B4252, 30  mg/ml BD. for staining); Pilocarpine hydrochloride and scopolamine Our previous research found that adult neurogenesis is methyl-bromide were also purchased from Sigma-Aldrich; impaired in Tmem108 null mice, and manic behavior is Other chemicals were purchased from Sangon Biotech found in the mutant mice [16], indicating that Tmem108 (BBI Life Sciences CO. China). also is related to BD. Furthermore, RNA sequencing Antibodies information as follows: Rabbit anti-β- showed that Tmem108 expression is much higher in Actin antibody (Santa Cruz Biotechnology, sc-1616-R; newly formed OLs than in other cells in the central nerv- 1:2000 for blotting); Rat anti-MBP antibody (Millipore, ous system (CNS) [17]. Therefore, these studies indicate MAB386; 1:2000 for blotting; 1:1000 for staining); Rabbit that Tmem108 may play a role in OL development and anti-TMEM108 antibody (1:1000 for blotting) was kindly myelination. presented by Dr. J. Liu [20]; Goat anti-rabbit IgG poly- In this study, Tmem108 expression in the CC was HRP secondary antibody (32260) and Goat anti-rat IgG higher in young mice than in adult mice and colocal- poly-HRP secondary antibody (31471) were purchased ized with OLs in young mice CC, implying promising from Thermo Fisher Scientific (1:2000 for blotting); function in myelination with the development. Intrigu- Mouse anti-Ki67 (BD Biosciences, 550609; 1:1000 for ingly, myelin basic protein (MBP) was highly expressed in staining); Rabbit anti-Olig2 antibody (Millipore, AB9610, Tmem108 mutant mice in immunohistochemistry (IHC) 1:1000 for staining); Rabbit anti-PDGFRα antibody staining and western blots (WB) assay, and electron (Cell Signaling Technology; 3174; 1:500 for staining); microscopes revealed hypermyelination in the CC of the Rat anti-PDGFRα antibody (BD Biosciences; 558774; mutant mice, especially early-onset myelination in small 1:200 for staining); Mouse anti-APC antibody (CC1, axons. Consistently, the cytological experiment showed Millipore Sigma, MABC200, 1:800 for staining); Rab- that Tmem108 inhibited OL progenitor cell (OPC) pro- bit anti-Caspase3 antibody (Cell Signaling Tech, 9662; liferation and mitigated the maturation of CC OLs by 1:1000 for staining); Alexa Fluor 488/568 goat anti-rabbit preventing the myelination of small-diameter axons. lgG (Thermo Fisher Scientific, A32731, A11011; 1:1000 Moreover, Tmem108 mutant mice exhibited manic for staining), Alexa Fluor 488/568 goat anti-mouse lgG behavior after acute restraint stress and were susceptible (Thermo Fisher Scientific, A-11029, A-11031; 1:1000 for to drug-induced epilepsy. This study disclosed the func - staining). tion of Tmem108 in CC, which may also provide a new role of Tmem108 involving BD pathogenesis via regulat- Behavioral analysis ing the myelination. For the forced swimming test (FST), mice were forced to swim in a two-liter beaker filled with about fifteen- Materials and methods centimeter-height water for 6  min. A camera monitored Animals mice movements with tracking software (Video freeze Tmem108 mutant (Tmem108-LacZ; MMRRC: 032633- version 2.5.5.0, Med Associate Inc.). The immobility in UCD) mice were described previously [16, 18, 19]. In the last four min was obtained for statistical analysis. brief, the first coding exon of Tmem108 was replaced Wu  et al. Molecular Brain (2022) 15:33 Page 3 of 13 According to the previous study, the pilocarpine model 30  min in PBS with 0.5% Triton X-100. After another 3 was conducted [21, 22]. In order to minimize the periph- washes in PBS, the brain sections were incubated in a eral side effects, mice were injected with scopolamine freshly-made EdU development cocktail (100  mM Tris- methyl-bromide (2  mg/kg mice weight, intraperitoneal buffered saline pH 7.4, 2  mM CuSO4 (Sangon Biotech injection) 30  min before pilocarpine hydrochloride (dis- A600063, CAS #7758-99-8), 2  μM 6-FAM Azide (Lumi- solved in 0.9% saline, 200  mg/kg mice weight, intraperi- probe #35130) and 100  mM Sodium Ascorbate (Sigma- toneal injection) treatment. Then, mice were injected Aldrich A7631, CAS#134-03-2). Following DAPI staining with pilocarpine (100 mg/kg mice weight) every 30 min. for 10  min, the brain sections were washed 3 times in Behavioral seizure score was according to the criteria by PBS and mounted for imaging. Racine [21]: stage 0, no seizure; stage 1, head nodding; stage 2, sporadic full-body shaking and spasms; stage 3, Quantitative real‑time PCR (qPCR) chronic full-body spasms; stage 4, jumping, shrieking, Total RNA was isolated from mice brains accord- and falling over; stage 5, violent convulsions, falling over ing to the manufacturer’s instructions of TRIzol Rea- and dying. gent (Invitrogen), and complementary DNA (cDNA) was synthesized following the manufacturer’s proto- Western blots (WB) col of High-Capacity cDNA Reverse Transcription Kit WB was conducted as our previous research, and white (Thermo Fisher Scientific, 4368814). The qPCR primer matter (CC and medulla) and gray matter (top layers of sets as below: Tmem108 (5′-CCT GAG CTA CTG GAA cortex) separation were according to the previous study CAA TGCC-3′ and 5′-CAG TGT CTC GAT AGT CGC [23]. We homogenized the tissues in lysis buffer (0.1% CAT TG-3′), and Gapdh (5′-CAT CAC TGC CAC CCA SDS, 0.5% sodium deoxycholate, 1% NP-40, 1 mM EDTA, GAA GACTG-3′ and 5′-ATG CCA GTG AGC TTC CCG 1 mM PMSF, 1 mg/ml aprotinin, leupeptin, and pepstatin TTCAG-3′). qPCR was carried out by the StepOnePlus A protease inhibitors, in 1 × DPBS). The protein was sep - Real‐Time PCR system (Applied Biosystems) using the arated by SDS-PAGE and then transferred to a nitrocellu- mix. qPCR was performed as described previously [25]. lose membrane. After being blocked, the membrane was mRNA expression levels were normalized to the refer- incubated with primary antibody and HRP-coupled sec- ence gene Gapdh using a ΔCT method. ondary antibody in turn. In the last, the immunoreacted bands were captured by an enhanced chemiluminescence X‑gal staining system (Bio RAD), and the band intensities were per- X-gal is an inert chromogenic substrate for β-gal, and formed with ImageJ software. β-gal hydrolyzes X-gal into colorless galactose and 4-chloro-3-brom-indigo, forming an intense blue pre- Immunohistochemistry (IHC) staining cipitate. X-gal staining was carried out as our previous The mice brain’s coronal setions  (30  µm) were prepared study [16, 26]. In brief, the coronal sections of Tmem108 by microtome (Leica CM1950) for IHC. After incubated mutant mice were prepared by microtome (Leica in a citrate buffer for antigen repair, sections were per - CM1950) and permeabilized with a detergent solution meabilized with a 20% tween for 20  min. Next, the sec- (0.01% sodium deoxycholate, 0.02% NP-40, 2 mM MgCl2 tions were blocked for 1  h at room temperature and in 0.1  M pH 7.4 phosphate buffer) at 4  °C. After incu - then incubated with primary antibody at 4 °C overnight. bated in staining solution (5 mM potassium ferricyanide, Afterward, sections were exposed to the secondary anti- 5  mM potassium ferrocyanide, 2  mg/ml X-gal in deter- body for 2 h in the dark at room temperature. Finally, the gent solution) overnight at 37 °C, the sections were trans- sections were transferred to the slides and mounted with ferred to the slides and mounted with coverslips. Finally, coverslips. The images were captured with an inverted the images were captured with an inverted fluorescence fluorescence microscope (Olympus FSX100). DAPI was microscope (Olympus FSX100). used to identify the cellular nuclei. Electron microscopy EdU labeling For electron microscopy, young (P14) and adult (P60) According to the previous study, the EdU labeling was male mice were perfused through the heart with phos- conducted with minor modified [24]. Daily intraperi - phate buffer (PB 0.1 M, pH 7.4) followed by 2% paraform - toneal injection of 3  mg EdU (Carbosynth, NE08701) aldehyde with 0.5% glutaraldehyde in PB. After carefully per gram body weight (P8 mice) was performed to dissecting the brain, the CC was immediately put into label dividing cells for 1  week. 24  h after the last injec- 2.5% glutaraldehyde incubating overnight at 4  °C and tion, brain sections were collected, rinsed 3 times in PBS rinsed in PB 5  min triple times. Then at room tempera - (phosphate-buffered saline), and then permeabilized for ture, the CC was postfixed in1% osmium tetroxide for Wu et al. Molecular Brain (2022) 15:33 Page 4 of 13 1  h, dehydrated through 30% and 50% ethanol 15  min g-ratio of a myelinated axon was calculated as the axonal in turn, and immersed in 70% uranyl acetate saturat- diameter and fiber diameter ratio. ing ethanol overnight. Afterward, the sample was dehy- drated through 80% and 95% ethanol 15  min, in turn, Statistical analysis followed by incubation of 100% ethanol 40  min twice. Values of all data are mean ± SEM (standard error of The dehydrated sample was infiltrated in epoxypro - the mean). Statistical analysis was carried out by Graph- pane (30  min), epoxypropane:ethoxyline resin (1:1, 2  h), Pad Prism 6.01. The statistical significance between the epoxypropane:ethoxyline resin (1:2, 1  h), and ethoxyline mutant and control mice was calculated by two‐way resin (Ephon812, 2  h) in a gelatin capsule in turn. Then, ANOVA (analysis of variance) and a two-tailed student the sample was polymerized in an oven at 45  °C 12  h t-test. The difference was defined as significant if the and 65  °C 48  h. Next, ultra-thin Sects.  (70  nm) of the p-value < 0.05. transversal cut CC axons were prepared on an ultrami- crotome (LKB-Nova, Sweden). The sections were trans - Results ferred onto 100 mesh copper grids followed rinsed with Higher Tmem108 expression of CC OLs in young mice ddH O 15  min triple times and stained in lead citrate than in adult mice 15 min followed with ddH O 10 min triple times. Finally, Tmem108 expression was verified by qPCR and WB the sections on the grids were examined on a transmis- (Fig.  1). For the whole brain of wild-type mice, qPCR sion electron microscope (JEOL, JEM-2100, Japan). The results showed that Tmem108 had a high expression B C 2.0 2.0 P0 P7 P14 P21 P30 P40 P60 130- 1.5 1.5 TMEM108 90- 1.0 1.0 46- β-ACTIN 0.5 0.5 P0 P7 P14 P21 P30 P40 P60 CB THY HP CC CT STR PFC OB D E F Tmem108 -/-. Young 1.5 CB THY HP CC CT STR PFC OB n.s. 1.0 130- TMEM108 90- Tmem108 -/-. Adult 0.5 ** 46- β-ACTIN P0 P7 P14 P30 P60 X-gal Olig2 DPAI Merge Fig. 1 Tmem108 expression profile in several areas of the brain. A Relative expression of Tmem108 in postnatal mice brain was quantified by qPCR. Gapdh was used as an internal control (Internal control of the below is same in qPCR assay), and Tmem108 expression in P0 mice was defined as 1; Wild-type male mice per group, n = 5. B Representative image of TMEM108 level in postnatal mice brains verified by western blotting. β-ACTIN was used as an internal control (Internal control of the below is the same in western blotting). C Tmem108 relative expression in the different areas of the adult mice brain. Tmem108 expression in CB was defined as 1; Wild-type male mice, n = 3; CB cerebellum, THY thalamus, HP hippocampus, CC corpus callosum, CT cerebral cortex, STR striatum, PFC prefrontal cortex, OB olfactory bulb. D Representative image of TMEM108 level in different areas of adult mice brain verified by western blotting. E Tmem108 relative expression of CC decreased in postnatal mice development. Tmem108 expression in P0 mice CC was defined as 1; Wild-type male mice per group, n = 3 (Unpaired T-test were made to compare with P0 data, n.s., not significant, * p < 0.05, ** p < 0.01). F Tmem108 expression in young mice CC was higher than in adult mice CC by X-gal staining. Tmem108 −/− mice per group, n = 3. G Co-staining indicated Tmem108 expression mostly colocalized with OLs in the corpus callosum of young mice. X-gal staining represented β-gal expression downstream of the Tmem108 promoter, and the arrows showed the X-gal staining dots in Tmem108 mutant mice (P14, Tmem108 −/− mice n = 3, scale bar = 20 μm) Tmem108 mRNA level Tmem108 mRNA level Tmem108 mRNA level Wu  et al. Molecular Brain (2022) 15:33 Page 5 of 13 in the young mice (Fig.  1A), and the protein level of the g-ratio value of CC in the young mutant mice was Tmem108 was similar to the mRNA level (Fig. 1B). qPCR lower than the control mice (Fig.  2C), implying hyper- and WB were utilized to check Tmem108 expression in myelination in the mutant mice. In line with expectation, different brain areas (Fig.  1C, D), including cerebellum hypermyelination of the CC in the adult mutant mice (CB), thalamus (THY), hippocampus (HP), corpus callo- was observed (Fig.  2G), and myelinated axon percent in sum (CC), cerebral cortex (CT), striatum (STR), prefron- the adult mutant mice was higher than the control mice tal cortex (PFC) and olfactory bulb (OB). Though CC and (Fig. 2F). Furthermore, the mean g-ratio values of the CC STR seemed to like having a low expression of Tmem108, axons with different diameters in the mice were counted the results supported Tmem108 expression in both areas. and statistically analyzed (Fig.  2D, H). Notably, thin fib - The highest expression cell type in the mice brain was ers in the myelinated axons of adult mice CC processed a newly formed OLs (Additional file  1: Fig. S1) [13]. CC small value of g-ratio (Fig. 2H). was considered an area with high myelinated axons, and therefore, CC was recruited to explore the role Preferred myelination of thin axons in Tmem108 mutant of Tmem108 in the OL lineage cells. Focusing on CC, mice + + Tmem108 was mainly expressed in PDGFRα Olig2 Electron microscopy also demonstrated the enhancement cells (OPCs) in P7 mice (Additional file  1: Fig. S2A-B), of OL maturation in the mutant mice. In the adult mice, and its expression profiles changed in P14 mice (Addi - myelin sheath was not different between the mutant and tional file  1: Fig. S2C-D), without difference among the control mice (Fig. 2E, K), though their g-ratio was dis- + + OPCs (PDGFRα ), OLs (C C1 ) and the double negative tinct (Fig. 2G). The percentage of diverse diameter fibers − − (PDGFRα CC1 ) cells. Considering Tmem108 being in total myelinated axons was investigated (Fig. 2I). Strik- highly expressed in newly formed OLs (Additional file  1: ingly, nearly half myelinated axons in the mutant mice Fig. S1), the double negative cells in the CC may repre- were thin fibers, with the axon diameter no more than sent premyelinating OLs. 600  nm (Fig.  2I), and the diameter of myelinated OLs Tmem108 expression decreased in postnatal develop- in the mutant mice was smaller than that in the control ment by qPCR assay, and Tmem108 mRNA relative level mice (Fig. 2J). in P7 mice CC was about two times that in P60 mice CC (Fig.  1E). Meanwhile, X-gal staining confirmed that High expression of Mbp in Tmem108 mutant mice Tmem108 expression was higher in young mice CC than Mbp mRNA levels and MBP protein were examined in in adult mice CC (Fig.  1F). Co-staining assay suggested the postnatal mice brain (Fig.  3A, D), in gray matter and that X-gal was remarkably co-stained with OL marker white matter of adult mice (Fig.  3B, E), and CC of adult Olig2 of CC in the young mice (Fig. 1G). mice (Fig.  3C, F). Mbp mRNA level seemed consistent with MBP protein level in the mutant mice (Fig.  3A–F). Hypermyelination of the CC in Tmem108 mutant mice Whole-brain MBP level in postnatal mice was quanti- Myelin sheath can be observed by transmission electron fied by WB (Fig.  3D), and MBP expression was higher microscopy, presenting thick, dark closed curves around in Tmem108 mutant mice than in the control mice after myelinated axons. In this research, the myelinated axons birth. According to the previous study [23], gray mat- of the CC from young and adult perfused male mice were ter and white matter were separated, and the latter were examined under an electron microscope. The myelinated considered brain areas with plenty of myelinated axons. axons’ ultrastructure was obtained for statistics, and the WB indicated that white matter in the mutant mice brain percentage of the myelinated axons in the total axons was had more MBP protein than in the control brain (Fig. 3E). reported. Littermate male mice were used to minimize Consistent with anticipation, MBP in CC of the mutant the background effect from other genes between the mice brain was higher than the control brain (Fig. 3F). mutant mice and the control mice. Although Tmem108 mutant did not alter the CC area Because myelination increases with mice’s develop- (Fig. 3G, H), cerebral cortex structure, and the hippocam- ment, it was not surprising that the percentage of the pus construction (Additional file  1: Fig. S3), MBP fluores - myelinated axons in the adult mice was 10–30% higher cence intensity of the brain CC in Tmem108 mutant mice than in the young mice (Fig.  2B, F). The g-ratio value of elevated (Fig. 3G, I). a myelinated axon is defined as the ratio of the axonal diameter and myelinated fiber diameter, considered a The proliferation of OL increased in the CC of the young typical myelination indicator. Accordingly, a high value of mutant mice g-ratio indicates a low value of relative myelin thickness. Myelination begins relatively late in the development of Myelinated axon percent in Tmem108 young mutant mice until after birth, and myelin sheaths are first seen mice CC resembled the control mice CC (Fig.  2B), but at P11. Increased myelination occurs during neonatal Wu et al. Molecular Brain (2022) 15:33 Page 6 of 13 A BC D 1.0 1.0 Tmem108 +/+ Tmem108 -/- 0.9 0.9 n.s. 0.85 0.8 0.8 *** 0.80 0.7 0.7 0.75 0.70 0.6 0.6 0.65 0.5 0.5 <0.6 0.6-0.7 0.7-0.8 0.8-0.9 0.9-1 1-1.2 1.2-1.4 >1.4 0 0.5 1.0 1.5 2.0 2.5 Axonal diameter(μm) Axonal diameter(μm) EF GH 1.0 Tmem108 +/+ Tmem108 -/- 1.0 0.9 0.9 0.85 0.8 0.8 *** *** 0.80 *** 0.7 0.7 0.75 0.70 0.6 0.6 0.65 0.5 20 0.5 0 0.5 1 1.5 2 2.5 3 <0.4 0.4-0.6 0.6-0.7 0.7-0. 0.8-0.9 0.9-1 1-1.2 1.2-1.4 >1.4 Axonal diameter(μm) Axonal diameter(μm) I J 0.8 0.6 Tmem108 +/+ 0.4 Tmem108 -/- 0.2 <0.4 0.4-0.6 0.6-0.8 0.8-1.0 1.0-1.2 1.2-1.4 >1.4 Myelinated axon diameter (μm) Fig. 2 Hypermyelination of the corpus callosum in Tmem108 mutant mice. A Representative electron microscopy of axons in the CC of young animals at P14. Same littermate male mice were used. B Percentages of CC myelinated axons were quantified in the young mice(P14). C Scatter plot of g-ratio values and g-ratio mean in the CC of the young mice(P14). D Mean g-ratio values of CC myelinated axons with different diameters in the young mice(P14). E Representative electron microscopy of axons in the CC of adult mice (2 M). Same littermate male mice were used. F Percentages of CC myelinated axons were quantified in the adult mice. G Scatter plot of g-ratio values and g-ratio mean in the CC of the adult mice. H Mean g-ratio values of CC myelinated axons with different diameters in the adult mice. (Red scale bar = 2 μm, white scale bar = 200 nm; Male mice per group n = 3, over 200 fibers per each type of animal were analyzed; Values were means ± SEM; Unpaired T-test were made between the groups; n.s., not significant, * p < 0.05, *** p < 0.001). I–K Small-diameter CC axons in Tmem108 mutant mice were readily myelinated. I Percentage of myelinated axons with different diameters in the total myelinated axons. J Diameter of myelinated axons in the adult mice. K Myelin thickness of CC axons in the adult mice (Tmem108 + / + mice n = 3, axon fiber n = 684; Tmem108 −/− mice n = 3, axon fiber n = 757; Unpaired T-test were made between the groups; n.s., not significant) development of the mice [27]. We speculated that young adult mice (Fig.  5B). Therefore, Caspase3, as an apopto - mice before P11 might have a high proliferation of OPCs sis marker, was engaged in assessing the apoptosis con- or newly formed OLs. EdU was injected into P8 mice dition in the Tmem108 mutant CC area. The mutant once a day for 7 days. CC of the P15 mice was co-stained mice displayed hyperapoptosis conditions in the CC area + + in EdU with Olig2 (Fig.  4A). EdU Olig2 cell density (Fig. 6). Intriguingly, mature OL lineage cells represented increased in the mutant mice (Fig.  4B), which indicated by Olig2 and CC1 double-positive cells increased in the high proliferation of the OPCs or newly formed OLs in mutant mice (Fig. 5C), implying that Tmem108 mitigated the mutant mice. Moreover, in other words, the result the maturation of CC OLs. suggested that Tmem108 inhibited OPC and newly formed OLs proliferation. Mania‑like behavior and easily induced epilepsy in Tmem108 mutant mice The maturation of CC OLs in Tmem108 mutant mice Tmem108 mutant mice display anti-depression behavior was enhanced (mania-like) behavior in the previous study [16]. In this To investigate the OLs maturation in the Tmem108 study, 24-h restraint stress worsened the mania behav- mutant mice, we utilized CC1 staining to evaluate the ior in FST (Fig.  7). Over half of Tmem108 mutant mice maturation of CC OL lineage cells in adult mice (Fig.  5). exhibited severe mania-like behavior during the restraint OL lineage cells proliferation increased in the mutant stress and died of physical exertion (Fig.  7C). Further- mice, but OL lineage cells density did not change in more, after the restraint stress, the remaining mutant Young Adult % of myelinated axons % of myelinated axons % of myelinated axons g-ratio g-ratio Axon diameter (μm) g-ratio g-ratio Myelin thickness (μm) g-ratio g-ratio Wu  et al. Molecular Brain (2022) 15:33 Page 7 of 13 AB C 2.0 3 Tmem108 +/+ *** n.s. 6 1.5 Tmem108 -/- ** 1.0 n.s. n.s. n.s. n.s. 1 n.s. 2 0.5 0 0 Gray matter White matter Corpus callosum P0 P7 P14 P21 P30 P40 P60 P0 P7 P14 P21 P30 P40 P60 *** +/+ -/-+/+ -/-+/+ -/-+/+ -/-+/+ -/- +/+ -/- +/+ -/- Tmem108 TMEM108 ** *** *** 90- n.s. n.s. 4 * 33- MBP 46- β-ACTIN 0 P0 P7 P14 P21 P30 P40 P60 E F Gray matter White matter TMEM108 TMEM108 * 90- 90- 33- n.s. 33- MBP MBP 46- 46- β-ACTIN β-ACTIN Gray matter White matter GH I 50 n.s. * MBP DAPI Merge MBP DAPI Merge * n.s. 0 0 Young Adult Young Adult YoungAdult Fig. 3 High expression of Mbp in Tmem108 mutant mice. A Quantified relative mRNA expression of Mbp by qPCR in the whole brain (Male mice per group n = 3; Two-way ANOVA analysis, postnatal day P-value < 0.001, genotype P-value < 0.01, interaction P-value < 0.001, and Sidak’s multiple comparisons test was conducted on indicated postnatal day). B, C Relative mRNA expression of Mbp by qPCR in gray matter, white matter (B) or corpus callosum (C) (Adult male mice, Tmem108 + / + mice n = 3, Tmem108 −/− mice n = 3; Unpaired T-test were made between the groups). D Representative image of MBP level in postnatal mice brain by western blotting (left panel); Quantification of MBP level in the western blotting (Tmem108 + / + mice n = 3, Tmem108 −/− mice n = 3; Two-way ANOVA analysis, postnatal day P-value = 0.0441, genotype P-value = 0.0122, interaction P-value = 0.0024, and Sidak’s multiple comparisons test was conducted at each postnatal day). E–F Representative image of MBP level in different areas of adult mice brain by western blotting (left panel); Quantification of MBP level in the western blotting (right panel), including gray matter, white matter (E), and CC (F) ( T-test analysis, Tmem108 + / + mice n = 5, Tmem108 −/− mice n = 5; Two-way ANOVA and unpaired T-test analysis were used). G–I High MBP fluorescence intensity in the corpus callosum of Tmem108 mutant mice. G Representative images of MBP staining in mice CC. H MBP fluorescence area of CC in Tmem108 mutant mice (Tmem108 −/−) was not different from the control mice (Tmem108 + / +). I MBP fluorescence intensity of CC in Tmem108 mutant mice was higher than the control mice (Scale bar = 200 μm; Male mice per group, n = 3, unpaired T-test analysis). ( Values are means ± SEM; n.s., not significant, *p < 0.05, **p < 0.01, **p < 0.001) mice struggled desperately without rest in FST (Fig.  7B), considered a classic experimental protocol to mimick indicating severe mania-like behavior in the mutant mice. human temporal lobe epilepsy [28]. The pilocarpine Meanwhile, the control mice could be separated into the model was utilized to evaluate the potential epilepsy of mania-like group, depressive group, and resistant group the mutant mice. In order to avoid the peripheral side (Fig. 7B). effects, scopolamine block was injected before the pilo - Due to the similarities and the behavioral manifes- carpine treatment (Fig.  7D). The mice were observed tation between pathophysiological mechanisms and continuously for behavioral seizures after each pilocar- the chronic seizures for their spontaneous and recur- pine injection. Tmem108 mutant mice quickly reached rent characteristics, the pilocarpine injection model is seizure stage 5 compared with the control mice (Fig. 7E, Tmem108 Mbp mRNA level -/-+/+ MBP relative level Mbp mRNA level MBP fluorescence area (mm ) MBP relative level Mbp mRNA level MBP fluorescence intensity MBP relative level Wu et al. Molecular Brain (2022) 15:33 Page 8 of 13 A B EdU OLIG2 DAPI Merge 0.4 0.3 0.2 0.1 Tmem108 +/+ Tmem108 -/- Fig. 4 The proliferation of OL increased in the CC of the young mutant mice. A Representative CC images in young mice at P15 co-staining EdU with Olig2, EdU injection once a day from P8 to P14. The last-right panel was signified the white rectangular area in the Merge panel. B Quantified + + double-positive (EdU Olig2 ) ratio in the young mice CC. (Scale bar = 20 μm; Mice per group n = 3; Values are means ± SEM; Unpaired T-test were made between the groups; *p < 0.05) AB C Tmem108 +/+ Olig2 CC1 Merge Tmem108 -/- 4 4 n.s. *** 3 3 Fig. 5 Maturation of CC oligodendrocytes in Tmem108 mutant mice increased. A Representative images of CC in the adult mice co-staining CC1 with Olig2. The dotted areas in the left panel were enlarged and shown on the right panel. B Quantified Olig2 positive cell density of CC in the adult mice. C Quantified double-positive (Olig2 + and CC1 +) cell density of CC in the adult mice. (Red scale bar = 50 μm, white scale bar = 10 μm; Male mice per group n = 5; Values are means ± SEM; Unpaired T-test were made between the groups; n.s., not significant, *** p < 0.001) AB Caspase3 DAPI Merge ** 0.06 0.04 0.02 Tmem108 +/+ Tmem108 -/- Fig. 6 High-level apoptosis of CC cells in Tmem108 mutant mice. A Representative images of CC in the adult mice staining apoptosis marker (Caspase3). The arrows showed the positive dot of Caspase3 staining. B Quantified Caspase3 positive cell density of CC in the adult mice. (Scale bar = 20 μm; Mice per group n = 6; Values are means ± SEM; Unpaired T-test were made between the groups; **p < 0.01) Tmem108 -/- Tmem108 +/+ Tmem108 -/- Tmem108 +/+ Tmem108 -/- Tmem108 +/+ 3 -2 Olig2+ cell density (x 10 mm ) Caspase3 cell ratio EdU+ Olig2+/DAPI cell ratio 3 -2 Olig2+ CC1+ cell density (x 10 mm ) Wu  et al. Molecular Brain (2022) 15:33 Page 9 of 13 A B C 100 *** 0 h 72 h Tmem108 +/+ Tmem108 -/- 10/18 Restraint stress Rest 48 h 24 h 2/22 Tmem108 +/+ -/-+/+ -/- Tmem108 +/+ -/- FST FST 0 h 72 h DE F Tmem108 +/+ Time (min) Tmem108 -/- -1 Inject scopolamine (2mg kg ) -1 Inject pilocarpine (200mg kg ) 30 IV III 8 -1 60 Inject pilocarpine (100mg kg ) II ... One injection of pilocarpine -1 I (100mg kg ) every 30min 6 ... ... ... 1 2 3 4 5 6 7 8 9 10 Stop injection until stage V Tmem108 +/+ -/- Number of pilocarpine injection Fig. 7 Tmem108 mutant mice exhibited mania-like behavior and were easily induced epilepsy. A Schematic of forced swimming test (FST ) with restraint stress; FST were recorded before restraint stress and two-day interval after restraint stress. B Comparing the immobility with the control mice before and after restrain stress, Tmem108 mutant (Tmem108 −/−) mice exhibited mania-like behavior in the tests (Tmem108 + / + mice n = 22, Tmem108 −/− mice n = 18). C Tmem108 mutant mice had serious mortality in the restraint stress. D Schematic of seizure inducement. Scopolamine was injected 30 min before applying pilocarpine to minimize the peripheral side effects. E Representative time courses of seizure development by repeated pilocarpine injection. Mice of two genotypes were subjected to pilocarpine injection every 30 min and scored for the seizure stage. F An increased number of pilocarpine injections were needed to reach stage 5 seizure for Tmem108 mutant mice (Tmem108 + / + mice n = 7, Tmem108 −/− mice n = 8). (Unpaired T-test analysis; * p < 0.05, *** p < 0.001) F), indicating Tmem108 involved the occurrence of of the total myelin protein in the CNS and is critical for induced epilepsy. myelination [33, 34]. MBP expression was enhanced in Tmem108 mutant mice via WB and IHC staining, and Discussion the mutant mice also exhibited hypermyelination by elec- Abnormal myelin development and the mental diseases tron microscopy. Although SCZ and BD account for 2–4% of the world The myelin sheath in mature OL acts as an external population, the pathogenesis and treatment of SCZ and insulator for current conduction, facilitating rapid salta- BD are unclear and unsatisfied [29, 30]. Strikingly, imag- tory impulse conduction with reduced axonal diameters. ing and autopsy studies not only show that abnormal Moreover, myelin also provides essential nutritional sup- white matter is a common neurobiological change in BD port for myelinated neurons. Myelinated fibers are widely and SCZ patients [4] but also reveal that SCZ patients are distributed in the brain, and myelin sheath is essential for accompanied with dysregulation of OL related processes, maintaining neural circuits. Accordingly, hypomyelina- such as myelination developmental disorder, abnormal tion or hypermyelination of OL deriving from abnormal expression of myelination gene and number changes of myelination may be one of the bases of cognitive impair- OLs [31, 32]. However, the molecule linking abnormal ment in SCZ and BD, also relating to poor prognosis [31, myelination with mental diseases is unclear. 35]. The myelin sheath is composed of bilayer lipids as the The cause of abnormal behaviors in Tmem108 mutant frame, with proteins embedded as one of the plasma mice is complicated. Tmem108 mutant mice in this membranes. Most of the proteins in the myelin sheath research were Tmem108 null mice. In the previous stud- are transmembrane proteins, such as MBP and prote- ies, Tmem108 knockout leads to a decrease of adult neu- olipid protein. In these proteins, MBP accounts for 30% rogenesis in the dentate gyrus [16] and impairs spine Immobility (%) seizure stage Injection number Mortality (%) to seizure stage V Wu et al. Molecular Brain (2022) 15:33 Page 10 of 13 development and glutamate transmission [18]. So, neu- Researchers have debated whether severe, chronic irri- ronal deficits in the mutant mice may also induce manic tability without episodic mania constitutes a develop- behavior and easily be induced epilepsy. Therefore, single mental phenotype of BD [5]. Neurobiological models of or both neuronal and oligodendrocyte loss of TMEM108 BD emphasize white matter aberrant development, and in the brain may contribute to abnormal behaviors. Con- white matter microstructure is often described as frac- dition knockout Tmem108 in OLs or neurons will pro- tional anisotropy, which is positively associated with the vide direct evidence for the behavior change. smaller axon diameter and increased axon packing den- sity [5]. Potential multiple functions of Tmem108 in the CNS The potential molecular mechanism of Tmem108 Tmem108, also known as Retrolinkin [20, 36, 37], is regulating myelination located on human chromosome 3q21. GWAS found In 2014, Zhang et  al. purified eight representative cell that TMEM108 is not only related to substance addic- populations from the cortex and generated the RNA tion [38], smoking withdrawal [39], and alcohol addiction transcriptome database for the different types of cells [40–43], but also is a susceptibility gene of SCZ [12, 13, [17] (Additional file  1: Fig. S1), which indicates Tmem108 15] and BD [12–14]. is expressed much higher in newly formed OLs than in O’Donovan et al. found that the SNP (rs7624858) muta- other OL lineage cells or neurons. Intriguingly in previ- tion in the intron of Tmem108 is related to SCZ [15, 44] ous research, Tmem108 was found highly expressed in and speculated that the site caused Tmem108 to become the granular cells of the dentate gyrus [16, 18]. In this a susceptibility gene of SCZ by affecting gene expres - research, OL lineage cells exhibited higher Tmem108 sion. Jiao et al. disclosed that Tmem108 mutant mice are expression than other cells in mice CC. Tmem108 mutant impaired in spatial memory, and fear startles contextual mice had manic-like behavior and were more active than memory and is more sensitive in PPI performance [18], the control group in forced swimming and tail suspen- a classic and plausible psychophysiological measurement sion experiments [16]. Moreover, 24-h restraint exacer- of sensorimotor gating for SCZ in rodents and humans bated the manic-like behavior of the mutant mice, and [45, 46]. the mutant mice were easily induced epilepsy by pilo- The nature of the severe mental illness has been carpine, which may be partially related to the abnormal debated for more than one century. According to the pre- myelination. vailing manuals, International Classification of Diseases, Although Tmem108 expression was low in the CC of BD, and schizophrenia reveal striking similarities, and adult mice without X-gal staining detection, its expres- the difference is that sensory gating and cognitive impair - sion was detectable in young wild-type mice and could be ments are less pronounced in BD patients [47]. BD and colocalized with Olig2 positive cells by utilizing the gene schizophrenia consistently ranked among the leading reporter mice. Tmem108 was highly expressed in the cer- causes of disability worldwide [48, 49], with similarities ebral cortex and hippocampus, with low expression in the across multiple levels, such as overlapping brain struc- CC; no alteration was found in the CC area, the cerebral tural [50, 51] and shared genetic risk factors [52–55]. BD cortex and the hippocampus construction in Tmem108 and schizophrenia are severe psychiatric disorders with mutant mice. However, MBP staining suggested no dif- high heritability, but to date, unknown etiology, sharing ference between Tmem108 mutant mice and the control genetic risk factors, and a possible illness mechanism is mice (Additional file  1: Fig. S4), which was inconsistent abnormal myelination [11, 56, 57]. with high MBP in the mutant mice CC. The main reason Although Tmem108 mutant impairs adult neurogenesis may be the lower density of the OLs in the cerebral cor- of the mice, it does not induce depression-like behavior tex than CC. but stirs manic-like behavior, suggesting Tmem108 is To explore how Tmem108 inhibited proliferation and higher correlating with BD than depression [16]. Strik- myelination of OL cells, gene expression with myelina- ingly, one recent GWAS screened BD risk loci in the Han tion regulation [58] was detected by qPCR. Intriguingly, Chinese population, covering 1822 BD patients and 4650 Tcf4 was also expressed highly besides myelin regulatory control individuals, and the data was replicated analy- factor (Myrf) in all three brain areas of Tmem108 mutant sis. After finally multiple analyses between Han Chinese mice (Additional file  1: Fig. S5). In previous research, and European populations, a new SNP (rs9863544) in BD Tmem108 was reported to involve adult neurogenesis patients were found, locating in the upstream regulatory by the Wnt signaling pathway. In CC, most genes with region of the Tmem108 gene [14]. Tmem108 expression significantly altering expression were downstream of change may be one of the onset reasons of the related the Wnt signaling pathway, such as ID2, ID4 and TCF4/ psychiatry diseases. TCF7L2. Wu  et al. Molecular Brain (2022) 15:33 Page 11 of 13 Wnt signaling plays a complicated role in the OL mye- Supplementary Information lination, depending on the final effector in the signaling The online version contains supplementary material available at https:// doi. org/ 10. 1186/ s13041- 022- 00918-7. pathway. Canonical Wnt/β-Catenin signaling pathway strongly inhibits differentiation [59–61]. Under Wnt3a Additional file 1: Fig. S1. Tmem108 expression profiles by cell type in treatment, differentiation of OPC is strongly delayed or the mice brain from RNA sequencing [13]. Fig. S2 Tmem108 expression blocked [61], recruiting TCF4/TCF7L2 to β-Catenin tar- in CC was mainly related to OPCs in P7 mice, and the expression profiles get genes to promote proliferation [60, 62]. ID2 and ID4 changed in P14 mice. A. Representative images of CC area of Tmem108 mutant P7 mice. The arrows showed the X-gal staining dots, which are the potential targets of Wnt/β-Catenin/TCF4 signals indicated the potential areas of Tmem108 expression. The right-below in OL development. panel was signified the white rectangular area in the middle-below panel. + + + Not surprisingly, β-Catenin decrease leads to enhanc- B. Quantify of PDGFRα X-gal cells percent in total X-gal cells in CC area (Tmem108 −/− mice, n = 4; Unpaired T-test analysis; * p < 0.05). C. ing the premyelinating OL. However, OL differentiation Representative images of CC area of Tmem108 mutant mice. The red arrow is not enhanced but reduced in Tcf7l2 knockout mice [59, showed the X-gal staining dot relating to PDGFRα OL. The white arrows 62], and differentiation is delayed in β-Catenin inacti - showed the X-gal staining dots associated with the CC1 cell, and the yellow arrows indicated the X-gal staining dots connecting with double vated mice [63], indicating the complexity of β-Catenin − − negative (PDGFRα CC1 ) cells. The right-below panel was signified the /TCF7L2. The potential mechanism is TCF7L2 interact - white rectangular area in the middle-below panel. D. Quantify different ing with HDAC1 (Histone deacetylases 1) and HDAC2, types of X-gal cells percent in total X-gal positive cells in the CC area (Tmem108 −/− mice, n = 4; One-way ANOVA analysis; n.s., not signifi- which repress the expression of differentiation inhibi - cant). (Scale bar = 20 μm; Values are means ± SEM). Fig. S3 No structural tors [59]. Thereby, TCF7L2 acts like a molecular switch, change of the cerebral cortex and the hippocampus in Tmem108 mutant blocking or promoting OL differentiation by associating mice. A. No structural alteration of cerebral cortex in the mutant mice. B. No structural change of the hippocampus in the mutant mice. (Scale with the different binding partners [64]. We speculated bar = 200 μm; Male adult mice per group n = 3). Fig. S4 MBP expression in that Tmem108 regulated proliferation and myelination Tmem108 mutant mouse cerebral cortex. A. Representative images of MBP via the Wnt signaling pathway depending on different staining in mice cerebral cortex. B-C. Quantified MBP fluorescence area (B) and fluorescence intensity of cerebral cortex in Tmem108 mutant mice. effectors. There was no difference between the mutant mice and the control mice. The potential molecular mechanism of TMEM108 (Scale bar = 200 μm; Male mice per group, n = 4, unpaired T-test analysis, regulating myelination was complicated. Interac- n.s., not significant). Fig. S5 Expression of myelination regulated genes in Tmem108 mutant mice. A. Myelination regulated gene expression in the tion between TMEM108 and Wnt signaling pathway CC. B. Myelination regulated gene expression in the cerebral cortex. A. increased its functional complexity and diversity. In Myelination regulated gene expression in the striatum. D. Venn diagram OPCs, TMEM108 may inhibit proliferation via restrict- of myelination regulated gene expression from CC, cerebral cortex, and striatum in Tmem108 mutant mice. (Gapdh was used as an internal con- ing β-Catenin/TCF7L2, and simultaneously, TMEM108 trol, and gene expression in wild-type mice was defined as 1; Male adult may also modulate differentiation via limiting HDAC/ mice per group n = 5; Unpaired T-test were made between the groups; * TCF4 interaction. In premyelinating OLs, TMEM108 p < 0.05). Table S1. Sequences of qPCR primers. may mitigate OL maturation through confining Myrf expression. The hypotheses need further research to ver - Acknowledgements ify them via in vivo and in vitro assays. We thank Dr. Baoming Li (Institute of Psychological Sciences, Hangzhou Normal University), Dr. Bingxing Pan, Dr. Erkang Fei, and Dr. Suqi Zou (Institute of Life Science, Nanchang University) for assisting in this project. Thanks to Dr. Jiajia Liu (Institute of Genetics and Developmental Biology, Chinese Academy Conclusion of Sciences) for providing the TMEM108 antibody and Dr. Shiwen Luo (Medical This study disclosed that Tmem108 inhibited OPC prolif- School of Jiangxi, Nanchang University) and Dr. Huifeng Jiao (School of Basic eration and mitigated the maturation of CC OLs, which Medical Science, Nanchang University) for suggestions in Tmem108 research. may also provide a new role of Tmem108 as a BD risk Author contributions gene via regulating myelination. SW initiated and designed the study. YZ performed WB, electron microscopy, qPCR and behavior tests. YW performed X-gal staining, EdU labeling and IHC. XL and XM helped the analysis in WB and IHC. JY, YZ, and XL assisted in the Abbreviations animal test and the electron microscopy. CM and HP advised on the project ANOVA: Analysis of variance; BD: Bipolar disorder; CB: Cerebellum; CC: Corpus and provided support. SW wrote the manuscript with input from all coauthors. callosum; CNS: Central nervous system; CT: Cerebral cortex; GWAS: Genome- All authors read and approved the final manuscript. wide association study; FST: Forced swimming test; HP: Hippocampus; IHC: Immunohistochemistry; MBP: Myelin basic protein; OB: Olfactory bulb; OL: Funding Oligodendrocyte; OPC: OL progenitor cell; PFC: Prefrontal cortex; PPI: Pre-pulse This work was supported partly by grants from China’s National Natural inhibition test; qPCR: Quantitative real-time PCR; SEM: Standard error of the Science Foundation (82071245, 31960171, 31760276, 31460260) and the mean; SNP: Single nucleotide polymorphism; STR: Striatum; SCZ: Schizophre- Jiangxi Natural Science Foundation (20202ACB215003, 20192ACB20022, nia; Tmem108: Transmembrane protein 108; THY: Thalamus; WB: Western blots; 20171BAB204019). X-gal: 5-Bromo-4-chloro-3-indolyl-β-d -galactopyranoside. Wu et al. Molecular Brain (2022) 15:33 Page 12 of 13 Availability of data and materials 12. Gonzalez-Mantilla AJ, Moreno-De-Luca A, Ledbetterand DH, Martin CL. A The datasets used or analyzed in our study are available from the correspond- cross-disorder method to identify novel candidate genes for develop- ing author on reasonable request. mental brain disorders. JAMA Psychiat. 2016;73(3):275–83. 13. Moskvina V, Craddock N, Holmans P, Nikolov I, Pahwa JS, Green E, et al. Gene-wide analyses of genome-wide association data sets: evidence for Declarations multiple common risk alleles for schizophrenia and bipolar disorder and for overlap in genetic risk. Mol Psychiatry. 2009;14(3):252–60. Ethics approval and consent to participate 14. Li HJ, Zhang C, Hui L, Zhou DS, Li Y, Zhang CY, et al. Novel risk loci All experiments involving animals were conducted according to the "guide- associated with genetic risk for bipolar disorder among Han Chinese lines for the care and use of experimental animals" issued by Nanchang Uni- individuals: a genome-wide association study and meta-analysis. JAMA versity. The Committee on the Ethics of Animal Experiments of the University Psychiat. 2021;78(3):320–30. of Nanchang approved the protocol. 15. O’Donovan MC, Craddock N, Norton N, Williams H, Peirce T, Moskvina V, et al. Identification of loci associated with schizophrenia by genome- Consent for publication wide association and follow-up. Nat Genet. 2008;40(9):1053–5. Not applicable. 16. Yu Z, Lin D, Zhong Y, Luo B, Liu S, Fei E, et al. Transmembrane protein 108 involves in adult neurogenesis in the hippocampal dentate gyrus. Competing interests Cell Biosci. 2019;9:9. The authors have no conflicts of interest to declare. 17. Zhang Y, Chen KN, Sloan SA, Bennett ML, Scholze AR, O’Keeffe S, et al. An RNA-sequencing transcriptome and splicing database of Author details glia, neurons, and vascular cells of the cerebral cortex. J Neurosci. Institute of Life Science, Nanchang University, Nanchang 330031, Jiangxi, 2014;34(36):11929–47. China. School of Life Sciences, Nanchang University, Nanchang 330031, 18. Jiao HF, Sun XD, Bates R, Xiong L, Zhang L, Liu F, et al. Transmembrane Jiangxi, China. School of Basic Medical Sciences, Nanchang University, Nan- protein 108 is required for glutamatergic transmission in dentate gyrus. chang 330031, Jiangxi, China. Senior Middle School of Yongfeng, Ji’an 343001, Proc Natl Acad Sci U S A. 2017;114(5):1177–82. Jiangxi, China. Queen Mary School, Nanchang University, Nanchang 330031, 19. Tang T, Li L, Tang J, Li Y, Lin WY, Martin F, et al. A mouse knockout Jiangxi, China. Neurological Institute of Jiangxi Province and Department library for secreted and transmembrane proteins. Nat Biotechnol. of Neurology, Jiangxi Provincial People’s Hospital, The First Affiliated Hospital 2010;28(7):749–55. of Nanchang Medical College, Nanchang 330006, Jiangxi, China. 20. Liu JJ, Ding J, Wu C, Bhagavatula P, Cui B, Chu S, et al. Retrolinkin, a membrane protein, plays an important role in retrograde axonal trans- Received: 27 September 2021 Accepted: 31 March 2022 port. Proc Natl Acad Sci U S A. 2007;104(7):2223–8. 21. Sun XD, Li L, Liu F, Huang ZH, Bean JC, Jiao HF, et al. Lrp4 in astrocytes modulates glutamatergic transmission. Nat Neurosci. 2016;19(8):1010–8. 22. Tan G-H, Liu Y-Y, Hu X-L, Yin D-M, Mei L, Xiong Z-Q. Neuregulin 1 References represses limbic epileptogenesis through ErbB4 in parvalbumin- 1. Mahon K, Burdickand KE, Szeszko PR. A role for white matter abnormali- expressing interneurons. Nat Neurosci. 2012;15(2):258–66. ties in the pathophysiology of bipolar disorder. Neurosci Biobehav Rev. 23. Tao Y, Dai P, Liu Y, Marchetto S, Xiong W-C, Borg J-P, et al. Erbin 2010;34(4):533–54. regulates NRG1 signaling and myelination. Proc Natl Acad Sci U S A. 2. Marlinge E, Bellivierand F, Houenou J. White matter alterations in bipolar 2009;106(23):9477–82. disorder: potential for drug discovery and development. Bipolar Disord. 24. Men Y, Wang Y, Yi Y, Jing D, Luo W, Shen B, et al. Gli1+ periodontium 2014;16(2):97–112. stem cells are regulated by osteocytes and occlusal force. Dev Cell. 3. Hu R, Stavish C, Leibenluftand E, Linke JO. white matter microstructure in 2020;54(5):639-654 e6. individuals with and at risk for bipolar disorder: evidence for an endophe- 25. Wang S, Huang S, Zhao X, Zhang Q, Wu M, Sun F, et al. Enrichment of notype from a voxel-based meta-analysis. Biol Psychiatry Cogn Neurosci prostate cancer stem cells from primary prostate cancer cultures of Neuroimaging. 2020;5(12):1104–13. biopsy samples. Int J Clin Exp Pathol. 2014;7(1):184–93. 4. Sehmbi M, Rowley CD, Minuzzi L, Kapczinski F, Kwiecien JM, Bock NA, 26. Yan M, Guo A, Chen P, Jing H, Ren D, Zhong Y, et al. LRP4 LDLalpha et al. Age-related deficits in intracortical myelination in young adults with repeats of astrocyte enhance dendrite arborization of the neuron. Mol bipolar disorder type I. J Psychiatry Neurosci. 2019;44(2):79–88. Brain. 2020;13(1):166. 5. Linke JO, Adleman NE, Sarlls J, Ross A, Perlstein S, Frank HR, et al. White 27. Khanbabaei M, Hughes E, Ellegood J, Qiu LR, Yip R, Dobry J, et al. matter microstructure in pediatric bipolar disorder and disruptive Precocious myelination in a mouse model of autism. Transl Psychiatry. mood dysregulation disorder. J Am Acad Child Adolesc Psychiatry. 2019;9(1):251. 2020;59(10):1135–45. 28. de Oliveira JC, Medeiros Ode C, de Souza ERGH, Moraesand MF, Cota 6. Bearden CE, van Erp TG, Dutton RA, Boyle C, Madsen S, Luders E, et al. VR. Temporally unstructured electrical stimulation to the amygdala Mapping corpus callosum morphology in twin pairs discordant for bipo- suppresses behavioral chronic seizures of the pilocarpine animal lar disorder. Cereb Cortex. 2011;21(10):2415–24. model. Epilepsy Behav. 2014;36:159–64. 7. Caetano SC, Silveira CM, Kaur S, Nicoletti M, Hatch JP, Brambilla P, et al. 29. Van Rheenen TE, Lewandowski KE, Bauer IE, Kapczinski F, Miskowiak K, Abnormal corpus callosum myelination in pediatric bipolar patients. J Burdick KE, et al. Current understandings of the trajectory and emerg- Aec ff t Disord. 2008;108(3):297–301. ing correlates of cognitive impairment in bipolar disorder: an overview 8. Keshavan MS, Diwadkar VA, DeBellis M, Dick E, Kotwal R, Rosenberg DR, of evidence. Bipolar Disord. 2020;22(1):13–27. et al. Development of the corpus callosum in childhood, adolescence 30. Fullerton JM, Nurnberger JI. Polygenic risk scores in psychiatry: will and early adulthood. Life Sci. 2002;70(16):1909–22. they be useful for clinicians? F1000Res. 2019;8(F1000 Faculty Rev):1293. 9. Lloyd AJ, Ali HE, Nesbitt D, Moore PB, Young AH, Ferrier IN. Corpus cal- 31. Raabe FJ, Slapakova L, Rossner MJ, Cantuti-Castelvetri L, Simons M, losum changes in euthymic bipolar affective disorder. Br J Psychiatry. Falkai PG, et al. Oligodendrocytes as a new therapeutic target in 2014;204(2):129–36. schizophrenia: from histopathological findings to neuron–oligoden- 10. Brambilla P, Nicoletti M, Sassi RB, Mallinger AG, Frank E, Keshavan MS, et al. drocyte interaction. Cells. 2019;8(12):1496. Corpus callosum signal intensity in patients with bipolar and unipolar 32. Jiang W, Kingand TZ, Turner JA. Imaging genetics towards a refined disorder. J Neurol Neurosurg Psychiatry. 2004;75(2):221–5. diagnosis of schizophrenia. Front Psychiatry. 2019;10:494. 11. Tkachev D, Mimmack ML, Ryan MM, Wayland M, Freeman T, Jones PB, 33. Voineskos AN, Felsky D, Kovacevic N, Tiwari AK, Zai C, Chakravarty MM, et al. Oligodendrocyte dysfunction in schizophrenia and bipolar disorder. et al. Oligodendrocyte genes, white matter tract integrity, and cogni- Lancet. 2003;362(9386):798–805. tion in schizophrenia. Cereb Cortex. 2013;23(9):2044–57. Wu  et al. Molecular Brain (2022) 15:33 Page 13 of 13 34. Boggs JM. Myelin basic protein: a multifunctional protein. Cell Mol Life 56. Ji E, Lejuste F, Sarrazinand S, Houenou J. From the microscope to the Sci. 2006;63(17):1945–61. magnet: disconnection in schizophrenia and bipolar disorder. Neurosci 35. Gouvea-Junqueira D, Falvella ACB, Antunes A, Seabra G, Brandao-Teles Biobehav Rev. 2019;98:47–57. C, Martins-de-Souza D, et al. Novel treatment strategies targeting 57. Jorgensen KN, Nerland S, Norbom LB, Doan NT, Nesvag R, Morch-Johnsen myelin and oligodendrocyte dysfunction in schizophrenia. Front L, et al. Increased MRI-based cortical grey/white-matter contrast in Psychiatry. 2020;11:379. sensory and motor regions in schizophrenia and bipolar disorder. Psychol 36. Xu C, Fu X, Zhuand S, Liu JJ. Retrolinkin recruits the WAVE1 protein Med. 2016;46(9):1971–85. complex to facilitate BDNF-induced TrkB endocytosis and dendrite 58. Santos AK, Vieira MS, Vasconcellos R, Goulart VAM, Kiharaand AH, Resende outgrowth. Mol Biol Cell. 2016;27(21):3342–56. RR. Decoding cell signalling and regulation of oligodendrocyte differen- 37. Fu X, Yang Y, Xu C, Niu Y, Chen T, Zhou Q, et al. Retrolinkin cooperates tiation. Semin Cell Dev Biol. 2019;95:54–73. with endophilin A1 to mediate BDNF-TrkB early endocytic trafficking and 59. Ye F, Chen Y, Hoang T, Montgomery RL, Zhao XH, Bu H, et al. HDAC1 and signaling from early endosomes. Mol Biol Cell. 2011;22(19):3684–98. HDAC2 regulate oligodendrocyte differentiation by disrupting the beta- 38. Johnson C, Drgon T, Liu QR, Zhang PW, Walther D, Li CY, et al. Genome catenin–TCF interaction. Nat Neurosci. 2009;12(7):829–38. wide association for substance dependence: convergent results from epi- 60. Fancy SP, Baranzini SE, Zhao C, Yuk DI, Irvine KA, Kaing S, et al. Dysregula- demiologic and research volunteer samples. BMC Med Genet. 2008;9:113. tion of the Wnt pathway inhibits timely myelination and remyelination in 39. Uhl GR, Liu Q-R, Drgon T, Johnson C, Walther D, Rose JE, et al. Molecular the mammalian CNS. Genes Dev. 2009;23(13):1571–85. genetics of successful smoking cessation convergent genome-wide 61. Shimizu T, Kagawa T, Wada T, Muroyama Y, Takadaand S, Ikenaka K. Wnt association study results. Arch Gen Psychiatry. 2008;65(6):683–93. signaling controls the timing of oligodendrocyte development in the 40. Heath AC, Whitfield JB, Martin NG, Pergadia ML, Goate AM, Lind PA, spinal cord. Dev Biol. 2005;282(2):397–410. et al. A quantitative-trait genome-wide association study of alcohol- 62. Fu H, Kesariand S, Cai J. Tcf7l2 is tightly controlled during myelin forma- ism risk in the community: findings and implications. Biol Psychiatry. tion. Cell Mol Neurobiol. 2012;32(3):345–52. 2011;70(6):513–8. 63. Dai J, Bercuryand KK, Macklin WB. Interaction of mTOR and 41. Zuo L, Gelernter J, Zhang CK, Zhao H, Lu L, Kranzler HR, et al. Genome- Erk1/2 signaling to regulate oligodendrocyte differentiation. Glia. wide association study of alcohol dependence implicates KIAA0040 on 2014;62(12):2096–109. chromosome 1q. Neuropsychopharmacology. 2012;37(2):557–66. 64. Mitew S, Hay CM, Peckham H, Xiao J, Koenningand M, Emery B. Mecha- 42. Pei YF, Zhang L, Yang TL, Han Y, Hai R, Ran S, et al. Genome-wide associa- nisms regulating the development of oligodendrocytes and central tion study of copy number variants suggests LTBP1 and FGD4 are impor- nervous system myelin. Neuroscience. 2014;276:29–47. tant for alcohol drinking. PLoS ONE. 2012;7(1): e30860. 43. Agrawal A, Bierut LJ. Identifying genetic variation for alcohol depend- Publisher’s Note ence. Alcohol Res. 2012;34(3):274–81. Springer Nature remains neutral with regard to jurisdictional claims in pub- 44. Yu J, Liao X, Zhong Y, Wu Y, Lai X, Jiao H, et al. The candidate schizophre- lished maps and institutional affiliations. nia risk gene Tmem108 regulates glucose metabolism homeostasis. Front Endocrinol (Lausanne). 2021;12: 770145. 45. Hiroi N, Nishi A. Dimensional deconstruction and reconstruction of CNV-associated neuropsychiatric disorders. Handb Behav Neurosci. 2016;23:285–302. 46. Halberstadt A, Geyer M. Hallucinogens. Encyclopedia of behavioral neu- roscience. 2010; pp 12–20. 47. Maier W, Zobeland A, Wagner M. Schizophrenia and bipolar disorder: differences and overlaps. Curr Opin Psychiatry. 2006;19(2):165–70. 48. Whiteford HA, Degenhardt L, Rehm J, Baxter AJ, Ferrari AJ, Erskine HE, et al. Global burden of disease attributable to mental and substance use disorders: findings from the Global Burden of Disease Study 2010. Lancet. 2013;382(9904):1575–86. 49. Schafer M, Kim JW, Joseph J, Xu J, Frangouand S, Doucet GE. Imaging habenula volume in schizophrenia and bipolar disorder. Front Psychiatry. 2018;9:456. 50. International Schizophrenia C, Purcell SM, Wray NR, Stone JL, Visscher PM, O’Donovan MC, et al. Common polygenic variation contributes to risk of schizophrenia and bipolar disorder. Nature. 2009; 460(7256):748–752. 51. Lichtenstein P, Yip BH, Björk C, Pawitan Y, Cannon TD, Sullivan PF, et al. Common genetic determinants of schizophrenia and bipo- lar disorder in Swedish families: a population-based study. Lancet. 2009;373(9659):234–9. 52. van Erp TGM, Walton E, Hibar DP, Schmaal L, Jiang W, Glahn DC, et al. Cortical brain abnormalities in 4474 individuals with schizophrenia and 5098 control subjects via the enhancing neuro imaging genetics through Re Read ady y to to submit y submit your our re researc search h ? Choose BMC and benefit fr ? Choose BMC and benefit from om: : meta analysis (ENIGMA) consortium. Biol Psychiatry. 2018;84(9):644–54. 53. Hibar DP, Westlye LT, Doan NT, Jahanshad N, Cheung JW, Ching CRK, et al. fast, convenient online submission Cortical abnormalities in bipolar disorder: an MRI analysis of 6503 indi- thorough peer review by experienced researchers in your field viduals from the ENIGMA Bipolar Disorder Working Group. Mol Psychiatry. 2018;23(4):932–42. rapid publication on acceptance 54. van Erp TG, Hibar DP, Rasmussen JM, Glahn DC, Pearlson GD, Andreassen support for research data, including large and complex data types OA, et al. Subcortical brain volume abnormalities in 2028 individuals with • gold Open Access which fosters wider collaboration and increased citations schizophrenia and 2540 healthy controls via the ENIGMA consortium. Mol Psychiatry. 2016;21(4):547–53. maximum visibility for your research: over 100M website views per year 55. Hibar DP, Westlye LT, van Erp TG, Rasmussen J, Leonardo CD, Faskowitz J, et al. Subcortical volumetric abnormalities in bipolar disorder. Mol At BMC, research is always in progress. Psychiatry. 2016;21(12):1710–6. Learn more biomedcentral.com/submissions http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Molecular Brain Springer Journals

Transmembrane protein 108 inhibits the proliferation and myelination of oligodendrocyte lineage cells in the corpus callosum

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Copyright © The Author(s) 2022
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10.1186/s13041-022-00918-7
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Abstract

Background: Abnormal white matter is a common neurobiological change in bipolar disorder, and dysregulation of myelination in oligodendrocytes (OLs) is the cause. Transmembrane protein 108 (Tmem108), as a susceptible gene of bipolar disorder, is expressed higher in OL lineage cells than any other lineage cells in the central nervous system. Moreover, Tmem108 mutant mice exhibit mania-like behaviors, belonging to one of the signs of bipolar disorder. However, it is unknown whether Tmem108 regulates the myelination of the OLs. Results: Tmem108 expression in the corpus callosum decreased with the development, and OL progenitor cell proliferation and OL myelination were enhanced in the mutant mice. Moreover, the mutant mice exhibited mania-like behavior after acute restraint stress and were susceptible to drug-induced epilepsy. Conclusions: Tmem108 inhibited OL progenitor cell proliferation and mitigated OL maturation in the corpus cal- losum, which may also provide a new role of Tmem108 involving bipolar disorder pathogenesis. Keywords: Tmem108, Oligodendrocyte (OL), Myelination, Corpus callosum (CC), Bipolar disorder (BD) Introduction radial diffusivity [3–5]. Abnormal white matter connec - Bipolar disorder (BD) is a severe mental disease charac- tivity may be associated with BD pathophysiology [4, 6], terized by manic states being usually interspersed with and elevated rates of white matter hyperintensities are periods of depression [1], affecting 1–1.5% of the popu - widely observed in BD [3–5]. lation [1, 2]. Aberrant white matter microstructure is The corpus callosum (CC) is the brain’s major white proposed as a mechanism underlying BD, including the matter fiber tract [6, 7], containing most axonal trans- dimension of irritability and widespread increases in missions between the two cerebral hemispheres. The CC is among the last brain structures to complete myelina- tion [8], which is also a period accompanying the peak *Correspondence: hailipan@qq.com; wsqi@ncu.edu.cn onset of BD [9]. Anatomical abnormalities in the CC have Yongqiang Wu and Yanzi Zhong have contributed equally to this been reported in magnetic resonance imaging studies research Institute of Life Science, Nanchang University, Nanchang 330031, in BD patients, possibly because of altered myelination Jiangxi, China leading to impaired interhemispheric communication Neurological Institute of Jiangxi Province and Department of Neurology, [10]. Changes in area and thickness in the CC have been Jiangxi Provincial People’s Hospital, The First Affiliated Hospital of Nanchang Medical College, Nanchang 330006, Jiangxi, China reported in BD, and neuropathological data and imaging Full list of author information is available at the end of the article © The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. The Creative Commons Public Domain Dedication waiver (http:// creat iveco mmons. org/ publi cdoma in/ zero/1. 0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Wu et al. Molecular Brain (2022) 15:33 Page 2 of 13 suggest possible abnormalities in myelination and glial with the β-galactosidase/neomycin cassette. Tmem108 function [2, 9]. Given the strong genetic underpinnings mutant mice in the paper were Tmem108-LacZ homozy- of both BD and white matter microstructure, such white gous (Tmem108 –/–). Mice were fed in a room 12-h matter aberrations may be a disease marker and an endo- light/dark cycle, at 22–25℃, with ad  libitum access to phenotype of BD [3, 11]. rodent chow diet and clean water. The experimental pro - Several genome-wide association studies (GWAS) sug- tocols were performed according to the "guidelines for gest that Tmem108 is a susceptible gene of BD [12–14], the care and use of experimental animals" issued by Nan- and the relevant single nucleotide polymorphism (SNP) chang University for research about vertebrate animals. site is not in the coding region of Tmem108, which is For in  vivo experiment, surgery was performed with speculated that the SNP may affect its expression [14, sodium pentobarbital anesthesia (50  mg/kg, intraperi- 15]. Strikingly, the recent GWAS screened BD risk loci in toneal injection), and efforts were executed to minimize the Han Chinese population, covering 1822 BD patients suffering and reduce the animal number. After the termi - and 4650 control individuals, and the data was replicated nal experiments, mice were euthanized by carbon dioxide analysis. After finally multiple analyses between Han Chi - inhalation. nese and European populations, a new SNP (rs9863544) in BD patients were found, locating in the upstream Reagents regulatory region of the Tmem108 gene [14]. Tmem108 X-gal (5-Bromo-4-chloro-3-indolyl-β-d -galactopyranoside) expression change may be one of the onset reasons for was purchased from Sigma-Aldrich (B4252, 30  mg/ml BD. for staining); Pilocarpine hydrochloride and scopolamine Our previous research found that adult neurogenesis is methyl-bromide were also purchased from Sigma-Aldrich; impaired in Tmem108 null mice, and manic behavior is Other chemicals were purchased from Sangon Biotech found in the mutant mice [16], indicating that Tmem108 (BBI Life Sciences CO. China). also is related to BD. Furthermore, RNA sequencing Antibodies information as follows: Rabbit anti-β- showed that Tmem108 expression is much higher in Actin antibody (Santa Cruz Biotechnology, sc-1616-R; newly formed OLs than in other cells in the central nerv- 1:2000 for blotting); Rat anti-MBP antibody (Millipore, ous system (CNS) [17]. Therefore, these studies indicate MAB386; 1:2000 for blotting; 1:1000 for staining); Rabbit that Tmem108 may play a role in OL development and anti-TMEM108 antibody (1:1000 for blotting) was kindly myelination. presented by Dr. J. Liu [20]; Goat anti-rabbit IgG poly- In this study, Tmem108 expression in the CC was HRP secondary antibody (32260) and Goat anti-rat IgG higher in young mice than in adult mice and colocal- poly-HRP secondary antibody (31471) were purchased ized with OLs in young mice CC, implying promising from Thermo Fisher Scientific (1:2000 for blotting); function in myelination with the development. Intrigu- Mouse anti-Ki67 (BD Biosciences, 550609; 1:1000 for ingly, myelin basic protein (MBP) was highly expressed in staining); Rabbit anti-Olig2 antibody (Millipore, AB9610, Tmem108 mutant mice in immunohistochemistry (IHC) 1:1000 for staining); Rabbit anti-PDGFRα antibody staining and western blots (WB) assay, and electron (Cell Signaling Technology; 3174; 1:500 for staining); microscopes revealed hypermyelination in the CC of the Rat anti-PDGFRα antibody (BD Biosciences; 558774; mutant mice, especially early-onset myelination in small 1:200 for staining); Mouse anti-APC antibody (CC1, axons. Consistently, the cytological experiment showed Millipore Sigma, MABC200, 1:800 for staining); Rab- that Tmem108 inhibited OL progenitor cell (OPC) pro- bit anti-Caspase3 antibody (Cell Signaling Tech, 9662; liferation and mitigated the maturation of CC OLs by 1:1000 for staining); Alexa Fluor 488/568 goat anti-rabbit preventing the myelination of small-diameter axons. lgG (Thermo Fisher Scientific, A32731, A11011; 1:1000 Moreover, Tmem108 mutant mice exhibited manic for staining), Alexa Fluor 488/568 goat anti-mouse lgG behavior after acute restraint stress and were susceptible (Thermo Fisher Scientific, A-11029, A-11031; 1:1000 for to drug-induced epilepsy. This study disclosed the func - staining). tion of Tmem108 in CC, which may also provide a new role of Tmem108 involving BD pathogenesis via regulat- Behavioral analysis ing the myelination. For the forced swimming test (FST), mice were forced to swim in a two-liter beaker filled with about fifteen- Materials and methods centimeter-height water for 6  min. A camera monitored Animals mice movements with tracking software (Video freeze Tmem108 mutant (Tmem108-LacZ; MMRRC: 032633- version 2.5.5.0, Med Associate Inc.). The immobility in UCD) mice were described previously [16, 18, 19]. In the last four min was obtained for statistical analysis. brief, the first coding exon of Tmem108 was replaced Wu  et al. Molecular Brain (2022) 15:33 Page 3 of 13 According to the previous study, the pilocarpine model 30  min in PBS with 0.5% Triton X-100. After another 3 was conducted [21, 22]. In order to minimize the periph- washes in PBS, the brain sections were incubated in a eral side effects, mice were injected with scopolamine freshly-made EdU development cocktail (100  mM Tris- methyl-bromide (2  mg/kg mice weight, intraperitoneal buffered saline pH 7.4, 2  mM CuSO4 (Sangon Biotech injection) 30  min before pilocarpine hydrochloride (dis- A600063, CAS #7758-99-8), 2  μM 6-FAM Azide (Lumi- solved in 0.9% saline, 200  mg/kg mice weight, intraperi- probe #35130) and 100  mM Sodium Ascorbate (Sigma- toneal injection) treatment. Then, mice were injected Aldrich A7631, CAS#134-03-2). Following DAPI staining with pilocarpine (100 mg/kg mice weight) every 30 min. for 10  min, the brain sections were washed 3 times in Behavioral seizure score was according to the criteria by PBS and mounted for imaging. Racine [21]: stage 0, no seizure; stage 1, head nodding; stage 2, sporadic full-body shaking and spasms; stage 3, Quantitative real‑time PCR (qPCR) chronic full-body spasms; stage 4, jumping, shrieking, Total RNA was isolated from mice brains accord- and falling over; stage 5, violent convulsions, falling over ing to the manufacturer’s instructions of TRIzol Rea- and dying. gent (Invitrogen), and complementary DNA (cDNA) was synthesized following the manufacturer’s proto- Western blots (WB) col of High-Capacity cDNA Reverse Transcription Kit WB was conducted as our previous research, and white (Thermo Fisher Scientific, 4368814). The qPCR primer matter (CC and medulla) and gray matter (top layers of sets as below: Tmem108 (5′-CCT GAG CTA CTG GAA cortex) separation were according to the previous study CAA TGCC-3′ and 5′-CAG TGT CTC GAT AGT CGC [23]. We homogenized the tissues in lysis buffer (0.1% CAT TG-3′), and Gapdh (5′-CAT CAC TGC CAC CCA SDS, 0.5% sodium deoxycholate, 1% NP-40, 1 mM EDTA, GAA GACTG-3′ and 5′-ATG CCA GTG AGC TTC CCG 1 mM PMSF, 1 mg/ml aprotinin, leupeptin, and pepstatin TTCAG-3′). qPCR was carried out by the StepOnePlus A protease inhibitors, in 1 × DPBS). The protein was sep - Real‐Time PCR system (Applied Biosystems) using the arated by SDS-PAGE and then transferred to a nitrocellu- mix. qPCR was performed as described previously [25]. lose membrane. After being blocked, the membrane was mRNA expression levels were normalized to the refer- incubated with primary antibody and HRP-coupled sec- ence gene Gapdh using a ΔCT method. ondary antibody in turn. In the last, the immunoreacted bands were captured by an enhanced chemiluminescence X‑gal staining system (Bio RAD), and the band intensities were per- X-gal is an inert chromogenic substrate for β-gal, and formed with ImageJ software. β-gal hydrolyzes X-gal into colorless galactose and 4-chloro-3-brom-indigo, forming an intense blue pre- Immunohistochemistry (IHC) staining cipitate. X-gal staining was carried out as our previous The mice brain’s coronal setions  (30  µm) were prepared study [16, 26]. In brief, the coronal sections of Tmem108 by microtome (Leica CM1950) for IHC. After incubated mutant mice were prepared by microtome (Leica in a citrate buffer for antigen repair, sections were per - CM1950) and permeabilized with a detergent solution meabilized with a 20% tween for 20  min. Next, the sec- (0.01% sodium deoxycholate, 0.02% NP-40, 2 mM MgCl2 tions were blocked for 1  h at room temperature and in 0.1  M pH 7.4 phosphate buffer) at 4  °C. After incu - then incubated with primary antibody at 4 °C overnight. bated in staining solution (5 mM potassium ferricyanide, Afterward, sections were exposed to the secondary anti- 5  mM potassium ferrocyanide, 2  mg/ml X-gal in deter- body for 2 h in the dark at room temperature. Finally, the gent solution) overnight at 37 °C, the sections were trans- sections were transferred to the slides and mounted with ferred to the slides and mounted with coverslips. Finally, coverslips. The images were captured with an inverted the images were captured with an inverted fluorescence fluorescence microscope (Olympus FSX100). DAPI was microscope (Olympus FSX100). used to identify the cellular nuclei. Electron microscopy EdU labeling For electron microscopy, young (P14) and adult (P60) According to the previous study, the EdU labeling was male mice were perfused through the heart with phos- conducted with minor modified [24]. Daily intraperi - phate buffer (PB 0.1 M, pH 7.4) followed by 2% paraform - toneal injection of 3  mg EdU (Carbosynth, NE08701) aldehyde with 0.5% glutaraldehyde in PB. After carefully per gram body weight (P8 mice) was performed to dissecting the brain, the CC was immediately put into label dividing cells for 1  week. 24  h after the last injec- 2.5% glutaraldehyde incubating overnight at 4  °C and tion, brain sections were collected, rinsed 3 times in PBS rinsed in PB 5  min triple times. Then at room tempera - (phosphate-buffered saline), and then permeabilized for ture, the CC was postfixed in1% osmium tetroxide for Wu et al. Molecular Brain (2022) 15:33 Page 4 of 13 1  h, dehydrated through 30% and 50% ethanol 15  min g-ratio of a myelinated axon was calculated as the axonal in turn, and immersed in 70% uranyl acetate saturat- diameter and fiber diameter ratio. ing ethanol overnight. Afterward, the sample was dehy- drated through 80% and 95% ethanol 15  min, in turn, Statistical analysis followed by incubation of 100% ethanol 40  min twice. Values of all data are mean ± SEM (standard error of The dehydrated sample was infiltrated in epoxypro - the mean). Statistical analysis was carried out by Graph- pane (30  min), epoxypropane:ethoxyline resin (1:1, 2  h), Pad Prism 6.01. The statistical significance between the epoxypropane:ethoxyline resin (1:2, 1  h), and ethoxyline mutant and control mice was calculated by two‐way resin (Ephon812, 2  h) in a gelatin capsule in turn. Then, ANOVA (analysis of variance) and a two-tailed student the sample was polymerized in an oven at 45  °C 12  h t-test. The difference was defined as significant if the and 65  °C 48  h. Next, ultra-thin Sects.  (70  nm) of the p-value < 0.05. transversal cut CC axons were prepared on an ultrami- crotome (LKB-Nova, Sweden). The sections were trans - Results ferred onto 100 mesh copper grids followed rinsed with Higher Tmem108 expression of CC OLs in young mice ddH O 15  min triple times and stained in lead citrate than in adult mice 15 min followed with ddH O 10 min triple times. Finally, Tmem108 expression was verified by qPCR and WB the sections on the grids were examined on a transmis- (Fig.  1). For the whole brain of wild-type mice, qPCR sion electron microscope (JEOL, JEM-2100, Japan). The results showed that Tmem108 had a high expression B C 2.0 2.0 P0 P7 P14 P21 P30 P40 P60 130- 1.5 1.5 TMEM108 90- 1.0 1.0 46- β-ACTIN 0.5 0.5 P0 P7 P14 P21 P30 P40 P60 CB THY HP CC CT STR PFC OB D E F Tmem108 -/-. Young 1.5 CB THY HP CC CT STR PFC OB n.s. 1.0 130- TMEM108 90- Tmem108 -/-. Adult 0.5 ** 46- β-ACTIN P0 P7 P14 P30 P60 X-gal Olig2 DPAI Merge Fig. 1 Tmem108 expression profile in several areas of the brain. A Relative expression of Tmem108 in postnatal mice brain was quantified by qPCR. Gapdh was used as an internal control (Internal control of the below is same in qPCR assay), and Tmem108 expression in P0 mice was defined as 1; Wild-type male mice per group, n = 5. B Representative image of TMEM108 level in postnatal mice brains verified by western blotting. β-ACTIN was used as an internal control (Internal control of the below is the same in western blotting). C Tmem108 relative expression in the different areas of the adult mice brain. Tmem108 expression in CB was defined as 1; Wild-type male mice, n = 3; CB cerebellum, THY thalamus, HP hippocampus, CC corpus callosum, CT cerebral cortex, STR striatum, PFC prefrontal cortex, OB olfactory bulb. D Representative image of TMEM108 level in different areas of adult mice brain verified by western blotting. E Tmem108 relative expression of CC decreased in postnatal mice development. Tmem108 expression in P0 mice CC was defined as 1; Wild-type male mice per group, n = 3 (Unpaired T-test were made to compare with P0 data, n.s., not significant, * p < 0.05, ** p < 0.01). F Tmem108 expression in young mice CC was higher than in adult mice CC by X-gal staining. Tmem108 −/− mice per group, n = 3. G Co-staining indicated Tmem108 expression mostly colocalized with OLs in the corpus callosum of young mice. X-gal staining represented β-gal expression downstream of the Tmem108 promoter, and the arrows showed the X-gal staining dots in Tmem108 mutant mice (P14, Tmem108 −/− mice n = 3, scale bar = 20 μm) Tmem108 mRNA level Tmem108 mRNA level Tmem108 mRNA level Wu  et al. Molecular Brain (2022) 15:33 Page 5 of 13 in the young mice (Fig.  1A), and the protein level of the g-ratio value of CC in the young mutant mice was Tmem108 was similar to the mRNA level (Fig. 1B). qPCR lower than the control mice (Fig.  2C), implying hyper- and WB were utilized to check Tmem108 expression in myelination in the mutant mice. In line with expectation, different brain areas (Fig.  1C, D), including cerebellum hypermyelination of the CC in the adult mutant mice (CB), thalamus (THY), hippocampus (HP), corpus callo- was observed (Fig.  2G), and myelinated axon percent in sum (CC), cerebral cortex (CT), striatum (STR), prefron- the adult mutant mice was higher than the control mice tal cortex (PFC) and olfactory bulb (OB). Though CC and (Fig. 2F). Furthermore, the mean g-ratio values of the CC STR seemed to like having a low expression of Tmem108, axons with different diameters in the mice were counted the results supported Tmem108 expression in both areas. and statistically analyzed (Fig.  2D, H). Notably, thin fib - The highest expression cell type in the mice brain was ers in the myelinated axons of adult mice CC processed a newly formed OLs (Additional file  1: Fig. S1) [13]. CC small value of g-ratio (Fig. 2H). was considered an area with high myelinated axons, and therefore, CC was recruited to explore the role Preferred myelination of thin axons in Tmem108 mutant of Tmem108 in the OL lineage cells. Focusing on CC, mice + + Tmem108 was mainly expressed in PDGFRα Olig2 Electron microscopy also demonstrated the enhancement cells (OPCs) in P7 mice (Additional file  1: Fig. S2A-B), of OL maturation in the mutant mice. In the adult mice, and its expression profiles changed in P14 mice (Addi - myelin sheath was not different between the mutant and tional file  1: Fig. S2C-D), without difference among the control mice (Fig. 2E, K), though their g-ratio was dis- + + OPCs (PDGFRα ), OLs (C C1 ) and the double negative tinct (Fig. 2G). The percentage of diverse diameter fibers − − (PDGFRα CC1 ) cells. Considering Tmem108 being in total myelinated axons was investigated (Fig. 2I). Strik- highly expressed in newly formed OLs (Additional file  1: ingly, nearly half myelinated axons in the mutant mice Fig. S1), the double negative cells in the CC may repre- were thin fibers, with the axon diameter no more than sent premyelinating OLs. 600  nm (Fig.  2I), and the diameter of myelinated OLs Tmem108 expression decreased in postnatal develop- in the mutant mice was smaller than that in the control ment by qPCR assay, and Tmem108 mRNA relative level mice (Fig. 2J). in P7 mice CC was about two times that in P60 mice CC (Fig.  1E). Meanwhile, X-gal staining confirmed that High expression of Mbp in Tmem108 mutant mice Tmem108 expression was higher in young mice CC than Mbp mRNA levels and MBP protein were examined in in adult mice CC (Fig.  1F). Co-staining assay suggested the postnatal mice brain (Fig.  3A, D), in gray matter and that X-gal was remarkably co-stained with OL marker white matter of adult mice (Fig.  3B, E), and CC of adult Olig2 of CC in the young mice (Fig. 1G). mice (Fig.  3C, F). Mbp mRNA level seemed consistent with MBP protein level in the mutant mice (Fig.  3A–F). Hypermyelination of the CC in Tmem108 mutant mice Whole-brain MBP level in postnatal mice was quanti- Myelin sheath can be observed by transmission electron fied by WB (Fig.  3D), and MBP expression was higher microscopy, presenting thick, dark closed curves around in Tmem108 mutant mice than in the control mice after myelinated axons. In this research, the myelinated axons birth. According to the previous study [23], gray mat- of the CC from young and adult perfused male mice were ter and white matter were separated, and the latter were examined under an electron microscope. The myelinated considered brain areas with plenty of myelinated axons. axons’ ultrastructure was obtained for statistics, and the WB indicated that white matter in the mutant mice brain percentage of the myelinated axons in the total axons was had more MBP protein than in the control brain (Fig. 3E). reported. Littermate male mice were used to minimize Consistent with anticipation, MBP in CC of the mutant the background effect from other genes between the mice brain was higher than the control brain (Fig. 3F). mutant mice and the control mice. Although Tmem108 mutant did not alter the CC area Because myelination increases with mice’s develop- (Fig. 3G, H), cerebral cortex structure, and the hippocam- ment, it was not surprising that the percentage of the pus construction (Additional file  1: Fig. S3), MBP fluores - myelinated axons in the adult mice was 10–30% higher cence intensity of the brain CC in Tmem108 mutant mice than in the young mice (Fig.  2B, F). The g-ratio value of elevated (Fig. 3G, I). a myelinated axon is defined as the ratio of the axonal diameter and myelinated fiber diameter, considered a The proliferation of OL increased in the CC of the young typical myelination indicator. Accordingly, a high value of mutant mice g-ratio indicates a low value of relative myelin thickness. Myelination begins relatively late in the development of Myelinated axon percent in Tmem108 young mutant mice until after birth, and myelin sheaths are first seen mice CC resembled the control mice CC (Fig.  2B), but at P11. Increased myelination occurs during neonatal Wu et al. Molecular Brain (2022) 15:33 Page 6 of 13 A BC D 1.0 1.0 Tmem108 +/+ Tmem108 -/- 0.9 0.9 n.s. 0.85 0.8 0.8 *** 0.80 0.7 0.7 0.75 0.70 0.6 0.6 0.65 0.5 0.5 <0.6 0.6-0.7 0.7-0.8 0.8-0.9 0.9-1 1-1.2 1.2-1.4 >1.4 0 0.5 1.0 1.5 2.0 2.5 Axonal diameter(μm) Axonal diameter(μm) EF GH 1.0 Tmem108 +/+ Tmem108 -/- 1.0 0.9 0.9 0.85 0.8 0.8 *** *** 0.80 *** 0.7 0.7 0.75 0.70 0.6 0.6 0.65 0.5 20 0.5 0 0.5 1 1.5 2 2.5 3 <0.4 0.4-0.6 0.6-0.7 0.7-0. 0.8-0.9 0.9-1 1-1.2 1.2-1.4 >1.4 Axonal diameter(μm) Axonal diameter(μm) I J 0.8 0.6 Tmem108 +/+ 0.4 Tmem108 -/- 0.2 <0.4 0.4-0.6 0.6-0.8 0.8-1.0 1.0-1.2 1.2-1.4 >1.4 Myelinated axon diameter (μm) Fig. 2 Hypermyelination of the corpus callosum in Tmem108 mutant mice. A Representative electron microscopy of axons in the CC of young animals at P14. Same littermate male mice were used. B Percentages of CC myelinated axons were quantified in the young mice(P14). C Scatter plot of g-ratio values and g-ratio mean in the CC of the young mice(P14). D Mean g-ratio values of CC myelinated axons with different diameters in the young mice(P14). E Representative electron microscopy of axons in the CC of adult mice (2 M). Same littermate male mice were used. F Percentages of CC myelinated axons were quantified in the adult mice. G Scatter plot of g-ratio values and g-ratio mean in the CC of the adult mice. H Mean g-ratio values of CC myelinated axons with different diameters in the adult mice. (Red scale bar = 2 μm, white scale bar = 200 nm; Male mice per group n = 3, over 200 fibers per each type of animal were analyzed; Values were means ± SEM; Unpaired T-test were made between the groups; n.s., not significant, * p < 0.05, *** p < 0.001). I–K Small-diameter CC axons in Tmem108 mutant mice were readily myelinated. I Percentage of myelinated axons with different diameters in the total myelinated axons. J Diameter of myelinated axons in the adult mice. K Myelin thickness of CC axons in the adult mice (Tmem108 + / + mice n = 3, axon fiber n = 684; Tmem108 −/− mice n = 3, axon fiber n = 757; Unpaired T-test were made between the groups; n.s., not significant) development of the mice [27]. We speculated that young adult mice (Fig.  5B). Therefore, Caspase3, as an apopto - mice before P11 might have a high proliferation of OPCs sis marker, was engaged in assessing the apoptosis con- or newly formed OLs. EdU was injected into P8 mice dition in the Tmem108 mutant CC area. The mutant once a day for 7 days. CC of the P15 mice was co-stained mice displayed hyperapoptosis conditions in the CC area + + in EdU with Olig2 (Fig.  4A). EdU Olig2 cell density (Fig. 6). Intriguingly, mature OL lineage cells represented increased in the mutant mice (Fig.  4B), which indicated by Olig2 and CC1 double-positive cells increased in the high proliferation of the OPCs or newly formed OLs in mutant mice (Fig. 5C), implying that Tmem108 mitigated the mutant mice. Moreover, in other words, the result the maturation of CC OLs. suggested that Tmem108 inhibited OPC and newly formed OLs proliferation. Mania‑like behavior and easily induced epilepsy in Tmem108 mutant mice The maturation of CC OLs in Tmem108 mutant mice Tmem108 mutant mice display anti-depression behavior was enhanced (mania-like) behavior in the previous study [16]. In this To investigate the OLs maturation in the Tmem108 study, 24-h restraint stress worsened the mania behav- mutant mice, we utilized CC1 staining to evaluate the ior in FST (Fig.  7). Over half of Tmem108 mutant mice maturation of CC OL lineage cells in adult mice (Fig.  5). exhibited severe mania-like behavior during the restraint OL lineage cells proliferation increased in the mutant stress and died of physical exertion (Fig.  7C). Further- mice, but OL lineage cells density did not change in more, after the restraint stress, the remaining mutant Young Adult % of myelinated axons % of myelinated axons % of myelinated axons g-ratio g-ratio Axon diameter (μm) g-ratio g-ratio Myelin thickness (μm) g-ratio g-ratio Wu  et al. Molecular Brain (2022) 15:33 Page 7 of 13 AB C 2.0 3 Tmem108 +/+ *** n.s. 6 1.5 Tmem108 -/- ** 1.0 n.s. n.s. n.s. n.s. 1 n.s. 2 0.5 0 0 Gray matter White matter Corpus callosum P0 P7 P14 P21 P30 P40 P60 P0 P7 P14 P21 P30 P40 P60 *** +/+ -/-+/+ -/-+/+ -/-+/+ -/-+/+ -/- +/+ -/- +/+ -/- Tmem108 TMEM108 ** *** *** 90- n.s. n.s. 4 * 33- MBP 46- β-ACTIN 0 P0 P7 P14 P21 P30 P40 P60 E F Gray matter White matter TMEM108 TMEM108 * 90- 90- 33- n.s. 33- MBP MBP 46- 46- β-ACTIN β-ACTIN Gray matter White matter GH I 50 n.s. * MBP DAPI Merge MBP DAPI Merge * n.s. 0 0 Young Adult Young Adult YoungAdult Fig. 3 High expression of Mbp in Tmem108 mutant mice. A Quantified relative mRNA expression of Mbp by qPCR in the whole brain (Male mice per group n = 3; Two-way ANOVA analysis, postnatal day P-value < 0.001, genotype P-value < 0.01, interaction P-value < 0.001, and Sidak’s multiple comparisons test was conducted on indicated postnatal day). B, C Relative mRNA expression of Mbp by qPCR in gray matter, white matter (B) or corpus callosum (C) (Adult male mice, Tmem108 + / + mice n = 3, Tmem108 −/− mice n = 3; Unpaired T-test were made between the groups). D Representative image of MBP level in postnatal mice brain by western blotting (left panel); Quantification of MBP level in the western blotting (Tmem108 + / + mice n = 3, Tmem108 −/− mice n = 3; Two-way ANOVA analysis, postnatal day P-value = 0.0441, genotype P-value = 0.0122, interaction P-value = 0.0024, and Sidak’s multiple comparisons test was conducted at each postnatal day). E–F Representative image of MBP level in different areas of adult mice brain by western blotting (left panel); Quantification of MBP level in the western blotting (right panel), including gray matter, white matter (E), and CC (F) ( T-test analysis, Tmem108 + / + mice n = 5, Tmem108 −/− mice n = 5; Two-way ANOVA and unpaired T-test analysis were used). G–I High MBP fluorescence intensity in the corpus callosum of Tmem108 mutant mice. G Representative images of MBP staining in mice CC. H MBP fluorescence area of CC in Tmem108 mutant mice (Tmem108 −/−) was not different from the control mice (Tmem108 + / +). I MBP fluorescence intensity of CC in Tmem108 mutant mice was higher than the control mice (Scale bar = 200 μm; Male mice per group, n = 3, unpaired T-test analysis). ( Values are means ± SEM; n.s., not significant, *p < 0.05, **p < 0.01, **p < 0.001) mice struggled desperately without rest in FST (Fig.  7B), considered a classic experimental protocol to mimick indicating severe mania-like behavior in the mutant mice. human temporal lobe epilepsy [28]. The pilocarpine Meanwhile, the control mice could be separated into the model was utilized to evaluate the potential epilepsy of mania-like group, depressive group, and resistant group the mutant mice. In order to avoid the peripheral side (Fig. 7B). effects, scopolamine block was injected before the pilo - Due to the similarities and the behavioral manifes- carpine treatment (Fig.  7D). The mice were observed tation between pathophysiological mechanisms and continuously for behavioral seizures after each pilocar- the chronic seizures for their spontaneous and recur- pine injection. Tmem108 mutant mice quickly reached rent characteristics, the pilocarpine injection model is seizure stage 5 compared with the control mice (Fig. 7E, Tmem108 Mbp mRNA level -/-+/+ MBP relative level Mbp mRNA level MBP fluorescence area (mm ) MBP relative level Mbp mRNA level MBP fluorescence intensity MBP relative level Wu et al. Molecular Brain (2022) 15:33 Page 8 of 13 A B EdU OLIG2 DAPI Merge 0.4 0.3 0.2 0.1 Tmem108 +/+ Tmem108 -/- Fig. 4 The proliferation of OL increased in the CC of the young mutant mice. A Representative CC images in young mice at P15 co-staining EdU with Olig2, EdU injection once a day from P8 to P14. The last-right panel was signified the white rectangular area in the Merge panel. B Quantified + + double-positive (EdU Olig2 ) ratio in the young mice CC. (Scale bar = 20 μm; Mice per group n = 3; Values are means ± SEM; Unpaired T-test were made between the groups; *p < 0.05) AB C Tmem108 +/+ Olig2 CC1 Merge Tmem108 -/- 4 4 n.s. *** 3 3 Fig. 5 Maturation of CC oligodendrocytes in Tmem108 mutant mice increased. A Representative images of CC in the adult mice co-staining CC1 with Olig2. The dotted areas in the left panel were enlarged and shown on the right panel. B Quantified Olig2 positive cell density of CC in the adult mice. C Quantified double-positive (Olig2 + and CC1 +) cell density of CC in the adult mice. (Red scale bar = 50 μm, white scale bar = 10 μm; Male mice per group n = 5; Values are means ± SEM; Unpaired T-test were made between the groups; n.s., not significant, *** p < 0.001) AB Caspase3 DAPI Merge ** 0.06 0.04 0.02 Tmem108 +/+ Tmem108 -/- Fig. 6 High-level apoptosis of CC cells in Tmem108 mutant mice. A Representative images of CC in the adult mice staining apoptosis marker (Caspase3). The arrows showed the positive dot of Caspase3 staining. B Quantified Caspase3 positive cell density of CC in the adult mice. (Scale bar = 20 μm; Mice per group n = 6; Values are means ± SEM; Unpaired T-test were made between the groups; **p < 0.01) Tmem108 -/- Tmem108 +/+ Tmem108 -/- Tmem108 +/+ Tmem108 -/- Tmem108 +/+ 3 -2 Olig2+ cell density (x 10 mm ) Caspase3 cell ratio EdU+ Olig2+/DAPI cell ratio 3 -2 Olig2+ CC1+ cell density (x 10 mm ) Wu  et al. Molecular Brain (2022) 15:33 Page 9 of 13 A B C 100 *** 0 h 72 h Tmem108 +/+ Tmem108 -/- 10/18 Restraint stress Rest 48 h 24 h 2/22 Tmem108 +/+ -/-+/+ -/- Tmem108 +/+ -/- FST FST 0 h 72 h DE F Tmem108 +/+ Time (min) Tmem108 -/- -1 Inject scopolamine (2mg kg ) -1 Inject pilocarpine (200mg kg ) 30 IV III 8 -1 60 Inject pilocarpine (100mg kg ) II ... One injection of pilocarpine -1 I (100mg kg ) every 30min 6 ... ... ... 1 2 3 4 5 6 7 8 9 10 Stop injection until stage V Tmem108 +/+ -/- Number of pilocarpine injection Fig. 7 Tmem108 mutant mice exhibited mania-like behavior and were easily induced epilepsy. A Schematic of forced swimming test (FST ) with restraint stress; FST were recorded before restraint stress and two-day interval after restraint stress. B Comparing the immobility with the control mice before and after restrain stress, Tmem108 mutant (Tmem108 −/−) mice exhibited mania-like behavior in the tests (Tmem108 + / + mice n = 22, Tmem108 −/− mice n = 18). C Tmem108 mutant mice had serious mortality in the restraint stress. D Schematic of seizure inducement. Scopolamine was injected 30 min before applying pilocarpine to minimize the peripheral side effects. E Representative time courses of seizure development by repeated pilocarpine injection. Mice of two genotypes were subjected to pilocarpine injection every 30 min and scored for the seizure stage. F An increased number of pilocarpine injections were needed to reach stage 5 seizure for Tmem108 mutant mice (Tmem108 + / + mice n = 7, Tmem108 −/− mice n = 8). (Unpaired T-test analysis; * p < 0.05, *** p < 0.001) F), indicating Tmem108 involved the occurrence of of the total myelin protein in the CNS and is critical for induced epilepsy. myelination [33, 34]. MBP expression was enhanced in Tmem108 mutant mice via WB and IHC staining, and Discussion the mutant mice also exhibited hypermyelination by elec- Abnormal myelin development and the mental diseases tron microscopy. Although SCZ and BD account for 2–4% of the world The myelin sheath in mature OL acts as an external population, the pathogenesis and treatment of SCZ and insulator for current conduction, facilitating rapid salta- BD are unclear and unsatisfied [29, 30]. Strikingly, imag- tory impulse conduction with reduced axonal diameters. ing and autopsy studies not only show that abnormal Moreover, myelin also provides essential nutritional sup- white matter is a common neurobiological change in BD port for myelinated neurons. Myelinated fibers are widely and SCZ patients [4] but also reveal that SCZ patients are distributed in the brain, and myelin sheath is essential for accompanied with dysregulation of OL related processes, maintaining neural circuits. Accordingly, hypomyelina- such as myelination developmental disorder, abnormal tion or hypermyelination of OL deriving from abnormal expression of myelination gene and number changes of myelination may be one of the bases of cognitive impair- OLs [31, 32]. However, the molecule linking abnormal ment in SCZ and BD, also relating to poor prognosis [31, myelination with mental diseases is unclear. 35]. The myelin sheath is composed of bilayer lipids as the The cause of abnormal behaviors in Tmem108 mutant frame, with proteins embedded as one of the plasma mice is complicated. Tmem108 mutant mice in this membranes. Most of the proteins in the myelin sheath research were Tmem108 null mice. In the previous stud- are transmembrane proteins, such as MBP and prote- ies, Tmem108 knockout leads to a decrease of adult neu- olipid protein. In these proteins, MBP accounts for 30% rogenesis in the dentate gyrus [16] and impairs spine Immobility (%) seizure stage Injection number Mortality (%) to seizure stage V Wu et al. Molecular Brain (2022) 15:33 Page 10 of 13 development and glutamate transmission [18]. So, neu- Researchers have debated whether severe, chronic irri- ronal deficits in the mutant mice may also induce manic tability without episodic mania constitutes a develop- behavior and easily be induced epilepsy. Therefore, single mental phenotype of BD [5]. Neurobiological models of or both neuronal and oligodendrocyte loss of TMEM108 BD emphasize white matter aberrant development, and in the brain may contribute to abnormal behaviors. Con- white matter microstructure is often described as frac- dition knockout Tmem108 in OLs or neurons will pro- tional anisotropy, which is positively associated with the vide direct evidence for the behavior change. smaller axon diameter and increased axon packing den- sity [5]. Potential multiple functions of Tmem108 in the CNS The potential molecular mechanism of Tmem108 Tmem108, also known as Retrolinkin [20, 36, 37], is regulating myelination located on human chromosome 3q21. GWAS found In 2014, Zhang et  al. purified eight representative cell that TMEM108 is not only related to substance addic- populations from the cortex and generated the RNA tion [38], smoking withdrawal [39], and alcohol addiction transcriptome database for the different types of cells [40–43], but also is a susceptibility gene of SCZ [12, 13, [17] (Additional file  1: Fig. S1), which indicates Tmem108 15] and BD [12–14]. is expressed much higher in newly formed OLs than in O’Donovan et al. found that the SNP (rs7624858) muta- other OL lineage cells or neurons. Intriguingly in previ- tion in the intron of Tmem108 is related to SCZ [15, 44] ous research, Tmem108 was found highly expressed in and speculated that the site caused Tmem108 to become the granular cells of the dentate gyrus [16, 18]. In this a susceptibility gene of SCZ by affecting gene expres - research, OL lineage cells exhibited higher Tmem108 sion. Jiao et al. disclosed that Tmem108 mutant mice are expression than other cells in mice CC. Tmem108 mutant impaired in spatial memory, and fear startles contextual mice had manic-like behavior and were more active than memory and is more sensitive in PPI performance [18], the control group in forced swimming and tail suspen- a classic and plausible psychophysiological measurement sion experiments [16]. Moreover, 24-h restraint exacer- of sensorimotor gating for SCZ in rodents and humans bated the manic-like behavior of the mutant mice, and [45, 46]. the mutant mice were easily induced epilepsy by pilo- The nature of the severe mental illness has been carpine, which may be partially related to the abnormal debated for more than one century. According to the pre- myelination. vailing manuals, International Classification of Diseases, Although Tmem108 expression was low in the CC of BD, and schizophrenia reveal striking similarities, and adult mice without X-gal staining detection, its expres- the difference is that sensory gating and cognitive impair - sion was detectable in young wild-type mice and could be ments are less pronounced in BD patients [47]. BD and colocalized with Olig2 positive cells by utilizing the gene schizophrenia consistently ranked among the leading reporter mice. Tmem108 was highly expressed in the cer- causes of disability worldwide [48, 49], with similarities ebral cortex and hippocampus, with low expression in the across multiple levels, such as overlapping brain struc- CC; no alteration was found in the CC area, the cerebral tural [50, 51] and shared genetic risk factors [52–55]. BD cortex and the hippocampus construction in Tmem108 and schizophrenia are severe psychiatric disorders with mutant mice. However, MBP staining suggested no dif- high heritability, but to date, unknown etiology, sharing ference between Tmem108 mutant mice and the control genetic risk factors, and a possible illness mechanism is mice (Additional file  1: Fig. S4), which was inconsistent abnormal myelination [11, 56, 57]. with high MBP in the mutant mice CC. The main reason Although Tmem108 mutant impairs adult neurogenesis may be the lower density of the OLs in the cerebral cor- of the mice, it does not induce depression-like behavior tex than CC. but stirs manic-like behavior, suggesting Tmem108 is To explore how Tmem108 inhibited proliferation and higher correlating with BD than depression [16]. Strik- myelination of OL cells, gene expression with myelina- ingly, one recent GWAS screened BD risk loci in the Han tion regulation [58] was detected by qPCR. Intriguingly, Chinese population, covering 1822 BD patients and 4650 Tcf4 was also expressed highly besides myelin regulatory control individuals, and the data was replicated analy- factor (Myrf) in all three brain areas of Tmem108 mutant sis. After finally multiple analyses between Han Chinese mice (Additional file  1: Fig. S5). In previous research, and European populations, a new SNP (rs9863544) in BD Tmem108 was reported to involve adult neurogenesis patients were found, locating in the upstream regulatory by the Wnt signaling pathway. In CC, most genes with region of the Tmem108 gene [14]. Tmem108 expression significantly altering expression were downstream of change may be one of the onset reasons of the related the Wnt signaling pathway, such as ID2, ID4 and TCF4/ psychiatry diseases. TCF7L2. Wu  et al. Molecular Brain (2022) 15:33 Page 11 of 13 Wnt signaling plays a complicated role in the OL mye- Supplementary Information lination, depending on the final effector in the signaling The online version contains supplementary material available at https:// doi. org/ 10. 1186/ s13041- 022- 00918-7. pathway. Canonical Wnt/β-Catenin signaling pathway strongly inhibits differentiation [59–61]. Under Wnt3a Additional file 1: Fig. S1. Tmem108 expression profiles by cell type in treatment, differentiation of OPC is strongly delayed or the mice brain from RNA sequencing [13]. Fig. S2 Tmem108 expression blocked [61], recruiting TCF4/TCF7L2 to β-Catenin tar- in CC was mainly related to OPCs in P7 mice, and the expression profiles get genes to promote proliferation [60, 62]. ID2 and ID4 changed in P14 mice. A. Representative images of CC area of Tmem108 mutant P7 mice. The arrows showed the X-gal staining dots, which are the potential targets of Wnt/β-Catenin/TCF4 signals indicated the potential areas of Tmem108 expression. The right-below in OL development. panel was signified the white rectangular area in the middle-below panel. + + + Not surprisingly, β-Catenin decrease leads to enhanc- B. Quantify of PDGFRα X-gal cells percent in total X-gal cells in CC area (Tmem108 −/− mice, n = 4; Unpaired T-test analysis; * p < 0.05). C. ing the premyelinating OL. However, OL differentiation Representative images of CC area of Tmem108 mutant mice. The red arrow is not enhanced but reduced in Tcf7l2 knockout mice [59, showed the X-gal staining dot relating to PDGFRα OL. The white arrows 62], and differentiation is delayed in β-Catenin inacti - showed the X-gal staining dots associated with the CC1 cell, and the yellow arrows indicated the X-gal staining dots connecting with double vated mice [63], indicating the complexity of β-Catenin − − negative (PDGFRα CC1 ) cells. The right-below panel was signified the /TCF7L2. The potential mechanism is TCF7L2 interact - white rectangular area in the middle-below panel. D. Quantify different ing with HDAC1 (Histone deacetylases 1) and HDAC2, types of X-gal cells percent in total X-gal positive cells in the CC area (Tmem108 −/− mice, n = 4; One-way ANOVA analysis; n.s., not signifi- which repress the expression of differentiation inhibi - cant). (Scale bar = 20 μm; Values are means ± SEM). Fig. S3 No structural tors [59]. Thereby, TCF7L2 acts like a molecular switch, change of the cerebral cortex and the hippocampus in Tmem108 mutant blocking or promoting OL differentiation by associating mice. A. No structural alteration of cerebral cortex in the mutant mice. B. No structural change of the hippocampus in the mutant mice. (Scale with the different binding partners [64]. We speculated bar = 200 μm; Male adult mice per group n = 3). Fig. S4 MBP expression in that Tmem108 regulated proliferation and myelination Tmem108 mutant mouse cerebral cortex. A. Representative images of MBP via the Wnt signaling pathway depending on different staining in mice cerebral cortex. B-C. Quantified MBP fluorescence area (B) and fluorescence intensity of cerebral cortex in Tmem108 mutant mice. effectors. There was no difference between the mutant mice and the control mice. The potential molecular mechanism of TMEM108 (Scale bar = 200 μm; Male mice per group, n = 4, unpaired T-test analysis, regulating myelination was complicated. Interac- n.s., not significant). Fig. S5 Expression of myelination regulated genes in Tmem108 mutant mice. A. Myelination regulated gene expression in the tion between TMEM108 and Wnt signaling pathway CC. B. Myelination regulated gene expression in the cerebral cortex. A. increased its functional complexity and diversity. In Myelination regulated gene expression in the striatum. D. Venn diagram OPCs, TMEM108 may inhibit proliferation via restrict- of myelination regulated gene expression from CC, cerebral cortex, and striatum in Tmem108 mutant mice. (Gapdh was used as an internal con- ing β-Catenin/TCF7L2, and simultaneously, TMEM108 trol, and gene expression in wild-type mice was defined as 1; Male adult may also modulate differentiation via limiting HDAC/ mice per group n = 5; Unpaired T-test were made between the groups; * TCF4 interaction. In premyelinating OLs, TMEM108 p < 0.05). Table S1. Sequences of qPCR primers. may mitigate OL maturation through confining Myrf expression. The hypotheses need further research to ver - Acknowledgements ify them via in vivo and in vitro assays. We thank Dr. Baoming Li (Institute of Psychological Sciences, Hangzhou Normal University), Dr. Bingxing Pan, Dr. Erkang Fei, and Dr. Suqi Zou (Institute of Life Science, Nanchang University) for assisting in this project. Thanks to Dr. Jiajia Liu (Institute of Genetics and Developmental Biology, Chinese Academy Conclusion of Sciences) for providing the TMEM108 antibody and Dr. Shiwen Luo (Medical This study disclosed that Tmem108 inhibited OPC prolif- School of Jiangxi, Nanchang University) and Dr. Huifeng Jiao (School of Basic eration and mitigated the maturation of CC OLs, which Medical Science, Nanchang University) for suggestions in Tmem108 research. may also provide a new role of Tmem108 as a BD risk Author contributions gene via regulating myelination. SW initiated and designed the study. YZ performed WB, electron microscopy, qPCR and behavior tests. YW performed X-gal staining, EdU labeling and IHC. XL and XM helped the analysis in WB and IHC. JY, YZ, and XL assisted in the Abbreviations animal test and the electron microscopy. CM and HP advised on the project ANOVA: Analysis of variance; BD: Bipolar disorder; CB: Cerebellum; CC: Corpus and provided support. SW wrote the manuscript with input from all coauthors. callosum; CNS: Central nervous system; CT: Cerebral cortex; GWAS: Genome- All authors read and approved the final manuscript. wide association study; FST: Forced swimming test; HP: Hippocampus; IHC: Immunohistochemistry; MBP: Myelin basic protein; OB: Olfactory bulb; OL: Funding Oligodendrocyte; OPC: OL progenitor cell; PFC: Prefrontal cortex; PPI: Pre-pulse This work was supported partly by grants from China’s National Natural inhibition test; qPCR: Quantitative real-time PCR; SEM: Standard error of the Science Foundation (82071245, 31960171, 31760276, 31460260) and the mean; SNP: Single nucleotide polymorphism; STR: Striatum; SCZ: Schizophre- Jiangxi Natural Science Foundation (20202ACB215003, 20192ACB20022, nia; Tmem108: Transmembrane protein 108; THY: Thalamus; WB: Western blots; 20171BAB204019). X-gal: 5-Bromo-4-chloro-3-indolyl-β-d -galactopyranoside. Wu et al. Molecular Brain (2022) 15:33 Page 12 of 13 Availability of data and materials 12. Gonzalez-Mantilla AJ, Moreno-De-Luca A, Ledbetterand DH, Martin CL. A The datasets used or analyzed in our study are available from the correspond- cross-disorder method to identify novel candidate genes for develop- ing author on reasonable request. mental brain disorders. JAMA Psychiat. 2016;73(3):275–83. 13. Moskvina V, Craddock N, Holmans P, Nikolov I, Pahwa JS, Green E, et al. Gene-wide analyses of genome-wide association data sets: evidence for Declarations multiple common risk alleles for schizophrenia and bipolar disorder and for overlap in genetic risk. Mol Psychiatry. 2009;14(3):252–60. Ethics approval and consent to participate 14. Li HJ, Zhang C, Hui L, Zhou DS, Li Y, Zhang CY, et al. Novel risk loci All experiments involving animals were conducted according to the "guide- associated with genetic risk for bipolar disorder among Han Chinese lines for the care and use of experimental animals" issued by Nanchang Uni- individuals: a genome-wide association study and meta-analysis. JAMA versity. The Committee on the Ethics of Animal Experiments of the University Psychiat. 2021;78(3):320–30. of Nanchang approved the protocol. 15. O’Donovan MC, Craddock N, Norton N, Williams H, Peirce T, Moskvina V, et al. Identification of loci associated with schizophrenia by genome- Consent for publication wide association and follow-up. Nat Genet. 2008;40(9):1053–5. Not applicable. 16. Yu Z, Lin D, Zhong Y, Luo B, Liu S, Fei E, et al. Transmembrane protein 108 involves in adult neurogenesis in the hippocampal dentate gyrus. Competing interests Cell Biosci. 2019;9:9. The authors have no conflicts of interest to declare. 17. Zhang Y, Chen KN, Sloan SA, Bennett ML, Scholze AR, O’Keeffe S, et al. An RNA-sequencing transcriptome and splicing database of Author details glia, neurons, and vascular cells of the cerebral cortex. J Neurosci. Institute of Life Science, Nanchang University, Nanchang 330031, Jiangxi, 2014;34(36):11929–47. China. School of Life Sciences, Nanchang University, Nanchang 330031, 18. Jiao HF, Sun XD, Bates R, Xiong L, Zhang L, Liu F, et al. Transmembrane Jiangxi, China. School of Basic Medical Sciences, Nanchang University, Nan- protein 108 is required for glutamatergic transmission in dentate gyrus. chang 330031, Jiangxi, China. Senior Middle School of Yongfeng, Ji’an 343001, Proc Natl Acad Sci U S A. 2017;114(5):1177–82. Jiangxi, China. Queen Mary School, Nanchang University, Nanchang 330031, 19. Tang T, Li L, Tang J, Li Y, Lin WY, Martin F, et al. A mouse knockout Jiangxi, China. Neurological Institute of Jiangxi Province and Department library for secreted and transmembrane proteins. Nat Biotechnol. of Neurology, Jiangxi Provincial People’s Hospital, The First Affiliated Hospital 2010;28(7):749–55. of Nanchang Medical College, Nanchang 330006, Jiangxi, China. 20. Liu JJ, Ding J, Wu C, Bhagavatula P, Cui B, Chu S, et al. Retrolinkin, a membrane protein, plays an important role in retrograde axonal trans- Received: 27 September 2021 Accepted: 31 March 2022 port. Proc Natl Acad Sci U S A. 2007;104(7):2223–8. 21. Sun XD, Li L, Liu F, Huang ZH, Bean JC, Jiao HF, et al. Lrp4 in astrocytes modulates glutamatergic transmission. Nat Neurosci. 2016;19(8):1010–8. 22. Tan G-H, Liu Y-Y, Hu X-L, Yin D-M, Mei L, Xiong Z-Q. Neuregulin 1 References represses limbic epileptogenesis through ErbB4 in parvalbumin- 1. Mahon K, Burdickand KE, Szeszko PR. A role for white matter abnormali- expressing interneurons. Nat Neurosci. 2012;15(2):258–66. ties in the pathophysiology of bipolar disorder. Neurosci Biobehav Rev. 23. Tao Y, Dai P, Liu Y, Marchetto S, Xiong W-C, Borg J-P, et al. Erbin 2010;34(4):533–54. regulates NRG1 signaling and myelination. Proc Natl Acad Sci U S A. 2. Marlinge E, Bellivierand F, Houenou J. White matter alterations in bipolar 2009;106(23):9477–82. disorder: potential for drug discovery and development. Bipolar Disord. 24. Men Y, Wang Y, Yi Y, Jing D, Luo W, Shen B, et al. Gli1+ periodontium 2014;16(2):97–112. stem cells are regulated by osteocytes and occlusal force. Dev Cell. 3. Hu R, Stavish C, Leibenluftand E, Linke JO. white matter microstructure in 2020;54(5):639-654 e6. individuals with and at risk for bipolar disorder: evidence for an endophe- 25. Wang S, Huang S, Zhao X, Zhang Q, Wu M, Sun F, et al. Enrichment of notype from a voxel-based meta-analysis. Biol Psychiatry Cogn Neurosci prostate cancer stem cells from primary prostate cancer cultures of Neuroimaging. 2020;5(12):1104–13. biopsy samples. Int J Clin Exp Pathol. 2014;7(1):184–93. 4. Sehmbi M, Rowley CD, Minuzzi L, Kapczinski F, Kwiecien JM, Bock NA, 26. Yan M, Guo A, Chen P, Jing H, Ren D, Zhong Y, et al. LRP4 LDLalpha et al. Age-related deficits in intracortical myelination in young adults with repeats of astrocyte enhance dendrite arborization of the neuron. Mol bipolar disorder type I. J Psychiatry Neurosci. 2019;44(2):79–88. Brain. 2020;13(1):166. 5. Linke JO, Adleman NE, Sarlls J, Ross A, Perlstein S, Frank HR, et al. White 27. Khanbabaei M, Hughes E, Ellegood J, Qiu LR, Yip R, Dobry J, et al. matter microstructure in pediatric bipolar disorder and disruptive Precocious myelination in a mouse model of autism. Transl Psychiatry. mood dysregulation disorder. J Am Acad Child Adolesc Psychiatry. 2019;9(1):251. 2020;59(10):1135–45. 28. de Oliveira JC, Medeiros Ode C, de Souza ERGH, Moraesand MF, Cota 6. Bearden CE, van Erp TG, Dutton RA, Boyle C, Madsen S, Luders E, et al. VR. Temporally unstructured electrical stimulation to the amygdala Mapping corpus callosum morphology in twin pairs discordant for bipo- suppresses behavioral chronic seizures of the pilocarpine animal lar disorder. Cereb Cortex. 2011;21(10):2415–24. model. Epilepsy Behav. 2014;36:159–64. 7. Caetano SC, Silveira CM, Kaur S, Nicoletti M, Hatch JP, Brambilla P, et al. 29. Van Rheenen TE, Lewandowski KE, Bauer IE, Kapczinski F, Miskowiak K, Abnormal corpus callosum myelination in pediatric bipolar patients. J Burdick KE, et al. Current understandings of the trajectory and emerg- Aec ff t Disord. 2008;108(3):297–301. ing correlates of cognitive impairment in bipolar disorder: an overview 8. Keshavan MS, Diwadkar VA, DeBellis M, Dick E, Kotwal R, Rosenberg DR, of evidence. Bipolar Disord. 2020;22(1):13–27. et al. Development of the corpus callosum in childhood, adolescence 30. Fullerton JM, Nurnberger JI. Polygenic risk scores in psychiatry: will and early adulthood. Life Sci. 2002;70(16):1909–22. they be useful for clinicians? F1000Res. 2019;8(F1000 Faculty Rev):1293. 9. Lloyd AJ, Ali HE, Nesbitt D, Moore PB, Young AH, Ferrier IN. Corpus cal- 31. Raabe FJ, Slapakova L, Rossner MJ, Cantuti-Castelvetri L, Simons M, losum changes in euthymic bipolar affective disorder. Br J Psychiatry. Falkai PG, et al. Oligodendrocytes as a new therapeutic target in 2014;204(2):129–36. schizophrenia: from histopathological findings to neuron–oligoden- 10. Brambilla P, Nicoletti M, Sassi RB, Mallinger AG, Frank E, Keshavan MS, et al. drocyte interaction. Cells. 2019;8(12):1496. Corpus callosum signal intensity in patients with bipolar and unipolar 32. Jiang W, Kingand TZ, Turner JA. Imaging genetics towards a refined disorder. J Neurol Neurosurg Psychiatry. 2004;75(2):221–5. diagnosis of schizophrenia. Front Psychiatry. 2019;10:494. 11. Tkachev D, Mimmack ML, Ryan MM, Wayland M, Freeman T, Jones PB, 33. Voineskos AN, Felsky D, Kovacevic N, Tiwari AK, Zai C, Chakravarty MM, et al. Oligodendrocyte dysfunction in schizophrenia and bipolar disorder. et al. Oligodendrocyte genes, white matter tract integrity, and cogni- Lancet. 2003;362(9386):798–805. tion in schizophrenia. Cereb Cortex. 2013;23(9):2044–57. Wu  et al. Molecular Brain (2022) 15:33 Page 13 of 13 34. Boggs JM. Myelin basic protein: a multifunctional protein. Cell Mol Life 56. Ji E, Lejuste F, Sarrazinand S, Houenou J. From the microscope to the Sci. 2006;63(17):1945–61. magnet: disconnection in schizophrenia and bipolar disorder. Neurosci 35. Gouvea-Junqueira D, Falvella ACB, Antunes A, Seabra G, Brandao-Teles Biobehav Rev. 2019;98:47–57. C, Martins-de-Souza D, et al. Novel treatment strategies targeting 57. Jorgensen KN, Nerland S, Norbom LB, Doan NT, Nesvag R, Morch-Johnsen myelin and oligodendrocyte dysfunction in schizophrenia. Front L, et al. Increased MRI-based cortical grey/white-matter contrast in Psychiatry. 2020;11:379. sensory and motor regions in schizophrenia and bipolar disorder. Psychol 36. Xu C, Fu X, Zhuand S, Liu JJ. Retrolinkin recruits the WAVE1 protein Med. 2016;46(9):1971–85. complex to facilitate BDNF-induced TrkB endocytosis and dendrite 58. Santos AK, Vieira MS, Vasconcellos R, Goulart VAM, Kiharaand AH, Resende outgrowth. Mol Biol Cell. 2016;27(21):3342–56. RR. Decoding cell signalling and regulation of oligodendrocyte differen- 37. Fu X, Yang Y, Xu C, Niu Y, Chen T, Zhou Q, et al. Retrolinkin cooperates tiation. Semin Cell Dev Biol. 2019;95:54–73. with endophilin A1 to mediate BDNF-TrkB early endocytic trafficking and 59. Ye F, Chen Y, Hoang T, Montgomery RL, Zhao XH, Bu H, et al. HDAC1 and signaling from early endosomes. Mol Biol Cell. 2011;22(19):3684–98. HDAC2 regulate oligodendrocyte differentiation by disrupting the beta- 38. Johnson C, Drgon T, Liu QR, Zhang PW, Walther D, Li CY, et al. Genome catenin–TCF interaction. Nat Neurosci. 2009;12(7):829–38. wide association for substance dependence: convergent results from epi- 60. Fancy SP, Baranzini SE, Zhao C, Yuk DI, Irvine KA, Kaing S, et al. Dysregula- demiologic and research volunteer samples. BMC Med Genet. 2008;9:113. tion of the Wnt pathway inhibits timely myelination and remyelination in 39. Uhl GR, Liu Q-R, Drgon T, Johnson C, Walther D, Rose JE, et al. Molecular the mammalian CNS. Genes Dev. 2009;23(13):1571–85. genetics of successful smoking cessation convergent genome-wide 61. Shimizu T, Kagawa T, Wada T, Muroyama Y, Takadaand S, Ikenaka K. Wnt association study results. Arch Gen Psychiatry. 2008;65(6):683–93. signaling controls the timing of oligodendrocyte development in the 40. Heath AC, Whitfield JB, Martin NG, Pergadia ML, Goate AM, Lind PA, spinal cord. Dev Biol. 2005;282(2):397–410. et al. A quantitative-trait genome-wide association study of alcohol- 62. Fu H, Kesariand S, Cai J. Tcf7l2 is tightly controlled during myelin forma- ism risk in the community: findings and implications. Biol Psychiatry. tion. Cell Mol Neurobiol. 2012;32(3):345–52. 2011;70(6):513–8. 63. Dai J, Bercuryand KK, Macklin WB. Interaction of mTOR and 41. Zuo L, Gelernter J, Zhang CK, Zhao H, Lu L, Kranzler HR, et al. Genome- Erk1/2 signaling to regulate oligodendrocyte differentiation. Glia. wide association study of alcohol dependence implicates KIAA0040 on 2014;62(12):2096–109. chromosome 1q. Neuropsychopharmacology. 2012;37(2):557–66. 64. Mitew S, Hay CM, Peckham H, Xiao J, Koenningand M, Emery B. Mecha- 42. Pei YF, Zhang L, Yang TL, Han Y, Hai R, Ran S, et al. Genome-wide associa- nisms regulating the development of oligodendrocytes and central tion study of copy number variants suggests LTBP1 and FGD4 are impor- nervous system myelin. Neuroscience. 2014;276:29–47. tant for alcohol drinking. PLoS ONE. 2012;7(1): e30860. 43. Agrawal A, Bierut LJ. Identifying genetic variation for alcohol depend- Publisher’s Note ence. Alcohol Res. 2012;34(3):274–81. Springer Nature remains neutral with regard to jurisdictional claims in pub- 44. Yu J, Liao X, Zhong Y, Wu Y, Lai X, Jiao H, et al. The candidate schizophre- lished maps and institutional affiliations. nia risk gene Tmem108 regulates glucose metabolism homeostasis. Front Endocrinol (Lausanne). 2021;12: 770145. 45. Hiroi N, Nishi A. Dimensional deconstruction and reconstruction of CNV-associated neuropsychiatric disorders. Handb Behav Neurosci. 2016;23:285–302. 46. Halberstadt A, Geyer M. Hallucinogens. Encyclopedia of behavioral neu- roscience. 2010; pp 12–20. 47. Maier W, Zobeland A, Wagner M. Schizophrenia and bipolar disorder: differences and overlaps. Curr Opin Psychiatry. 2006;19(2):165–70. 48. Whiteford HA, Degenhardt L, Rehm J, Baxter AJ, Ferrari AJ, Erskine HE, et al. Global burden of disease attributable to mental and substance use disorders: findings from the Global Burden of Disease Study 2010. Lancet. 2013;382(9904):1575–86. 49. Schafer M, Kim JW, Joseph J, Xu J, Frangouand S, Doucet GE. Imaging habenula volume in schizophrenia and bipolar disorder. Front Psychiatry. 2018;9:456. 50. International Schizophrenia C, Purcell SM, Wray NR, Stone JL, Visscher PM, O’Donovan MC, et al. Common polygenic variation contributes to risk of schizophrenia and bipolar disorder. Nature. 2009; 460(7256):748–752. 51. Lichtenstein P, Yip BH, Björk C, Pawitan Y, Cannon TD, Sullivan PF, et al. Common genetic determinants of schizophrenia and bipo- lar disorder in Swedish families: a population-based study. Lancet. 2009;373(9659):234–9. 52. van Erp TGM, Walton E, Hibar DP, Schmaal L, Jiang W, Glahn DC, et al. Cortical brain abnormalities in 4474 individuals with schizophrenia and 5098 control subjects via the enhancing neuro imaging genetics through Re Read ady y to to submit y submit your our re researc search h ? Choose BMC and benefit fr ? Choose BMC and benefit from om: : meta analysis (ENIGMA) consortium. Biol Psychiatry. 2018;84(9):644–54. 53. Hibar DP, Westlye LT, Doan NT, Jahanshad N, Cheung JW, Ching CRK, et al. fast, convenient online submission Cortical abnormalities in bipolar disorder: an MRI analysis of 6503 indi- thorough peer review by experienced researchers in your field viduals from the ENIGMA Bipolar Disorder Working Group. Mol Psychiatry. 2018;23(4):932–42. rapid publication on acceptance 54. van Erp TG, Hibar DP, Rasmussen JM, Glahn DC, Pearlson GD, Andreassen support for research data, including large and complex data types OA, et al. 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Journal

Molecular BrainSpringer Journals

Published: Apr 11, 2022

Keywords: Tmem108; Oligodendrocyte (OL); Myelination; Corpus callosum (CC); Bipolar disorder (BD)

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