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Zhang M, Zhang K, Wang J, Liu Y, Liu G, Jin W, Wu S, Zhao X. Immunoprecipitation and mass spectrometry define TET1 interactome during oligodendrocyte differentiation. Cell Biosci 2020; 10:110. [PMID: 32974003 PMCID: PMC7493855 DOI: 10.1186/s13578-020-00473-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 09/08/2020] [Indexed: 12/15/2022] Open
Abstract
Ten-eleven translocation (TET) proteins, encoding dioxygenase for DNA hydroxymethylation, are important players in nervous system development and disease. In addition to their proverbial enzymatic role, TET proteins also possess non-enzymatic activity and function in multiple protein-protein interaction networks, which remains largely unknown during oligodendrocyte differentiation. To identify partners of TET1 in the myelinating cells, we performed proteome-wide analysis using co-immunoprecipitation coupled to mass spectrometry (IP-MS) in purified oligodendrocyte precursor cells (OPCs) and mature oligodendrocytes (mOLs), respectively. Following a stringent selection of MS data based on identification reliability and protein enrichment, we identified a core set of 1211 partners that specifically interact with TET1 within OPCs and OLs. Analysis of the biological process and pathways associated with TET1-interacting proteins indicates a significant enrichment of proteins involved in regulation of cellular protein localization, cofactor metabolic process and regulation of catabolic process, et al. We further validated TET1 interactions with selected partners. Overall, this comprehensive analysis of the endogenous TET1 interactome during oligodendrocyte differentiation suggest its novel mechanism in regulating oligodendrocyte homeostasis and provide comprehensive insight into the molecular pathways associated with TET1.
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Affiliation(s)
- Ming Zhang
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032 Shaanxi China
| | - Kaixiang Zhang
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032 Shaanxi China
| | - Jian Wang
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032 Shaanxi China
| | - Yuming Liu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032 Shaanxi China
| | - Guangxin Liu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032 Shaanxi China
| | - Weilin Jin
- School of Electronic, Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai, 200240 China
| | - Shengxi Wu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032 Shaanxi China
| | - Xianghui Zhao
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032 Shaanxi China
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The Role of Vesicle Trafficking and Release in Oligodendrocyte Biology. Neurochem Res 2019; 45:620-629. [PMID: 31782103 DOI: 10.1007/s11064-019-02913-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/11/2019] [Accepted: 11/16/2019] [Indexed: 12/11/2022]
Abstract
Oligodendrocytes are a subtype of glial cells found within the central nervous system (CNS), responsible for the formation and maintenance of specialized myelin membranes which wrap neuronal axons. The development of myelin requires tight coordination for the cell to deliver lipid and protein building blocks to specific myelin segments at the right time. Both internal and external cues control myelination, thus the reception of these signals also requires precise regulation. In late years, a growing body of evidence indicates that oligodendrocytes, like many other cell types, may use extracellular vesicles (EVs) as a medium for transferring information. The field of EV research has expanded rapidly over the past decade, with new contributions that suggest EVs might have direct involvement in communications with neurons and other glial cells to fine tune oligodendroglial function. This functional role of EVs might also be maladaptive, as it has likewise been implicated in the spreading of toxic molecules within the brain during disease. In this review we will discuss the field's current understanding of extracellular vesicle biology within oligodendrocytes, and their contribution to physiologic and pathologic conditions.
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Myelin Disturbances Produced by Sub-Toxic Concentration of Heavy Metals: The Role of Oligodendrocyte Dysfunction. Int J Mol Sci 2019; 20:ijms20184554. [PMID: 31540019 PMCID: PMC6769910 DOI: 10.3390/ijms20184554] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 09/09/2019] [Accepted: 09/09/2019] [Indexed: 02/07/2023] Open
Abstract
Evidence has been accumulated demonstrating that heavy metals may accumulate in various organs, leading to tissue damage and toxic effects in mammals. In particular, the Central Nervous System (CNS) seems to be particularly vulnerable to cumulative concentrations of heavy metals, though the pathophysiological mechanisms is still to be clarified. In particular, the potential role of oligodendrocyte dysfunction and myelin production after exposure to subtoxic concentration I confirmed. It is ok of heavy metals is to be better assessed. Here we investigated on the effect of sub-toxic concentration of several essential (Cu2 +, Cr3 +, Ni2 +, Co2+) and non-essential (Pb2 +, Cd2+, Al3+) heavy metals on human oligodendrocyte MO3.13 and human neuronal SHSY5Y cell lines (grown individually or in co-culture). MO3.13 cells are an immortal human–human hybrid cell line with the phenotypic characteristics of primary oligodendrocytes but following the differentiation assume the morphological and biochemical features of mature oligodendrocytes. For this reason, we decided to use differentiated MO3.13 cell line. In particular, exposure of both cell lines to heavy metals produced a reduced cell viability of co-cultured cell lines compared to cells grown separately. This effect was more pronounced in neurons that were more sensitive to metals than oligodendrocytes when the cells were grown in co-culture. On the other hand, a significant reduction of lipid component in cells occurred after their exposure to heavy metals, an effect accompanied by substantial reduction of the main protein that makes up myelin (MBP) in co-cultured cells. Finally, the effect of heavy metals in oligodendrocytes were associated to imbalanced intracellular calcium ion concentration as measured through the fluorescent Rhod-2 probe, thus confirming that heavy metals, even used at subtoxic concentrations, lead to dysfunctional oligodendrocytes. In conclusion, our data show, for the first time, that sub-toxic concentrations of several heavy metals lead to dysfunctional oligodendrocytes, an effect highlighted when these cells are co-cultured with neurons. The pathophysiological mechanism(s) underlying this effect is to be better clarified. However, imbalanced intracellular calcium ion regulation, altered lipid formation and, finally, imbalanced myelin formation seem to play a major role in early stages of heavy metal-related oligodendrocyte dysfunction.
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Chen N, Dai L, Jiang Y, Wang J, Hao H, Ren Y, Leng X, Zang L, Wu Y. Endoplasmic reticulum stress intolerance in EIF2B3 mutant oligodendrocytes is modulated by depressed autophagy. Brain Dev 2016; 38:507-15. [PMID: 26625702 DOI: 10.1016/j.braindev.2015.11.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 10/06/2015] [Accepted: 11/06/2015] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Eukaryotic translation initiation factor 2B (eIF2B) is an essential factor for the initiation of protein synthesis. Mutations in eIF2B encoded by EIF2B1-5 cause a lethal leukoencephalopathy--vanishing white matter disease (VWM). Previous studies have suggested that an improper activated unfolded protein response (UPR) after endoplasmic reticulum stress (ERS) contributed to the pathogenesis of the disease. Autophagy, an important compensatory pathway after ERS, was analyzed in this study. METHODS To determine the tolerance differences to ERS, cell viability and apoptosis rates were detected in oligodendrocyte cell lines transfected with EIF2B3-c.1037T>C or the wild type. Autophagy flux was measured between groups. Autophagy inducers and inhibitors were used to identify the role of autophagy in the mutant oligodendrocytes. RESULTS We confirmed that oligodendrocytes with mutant EIF2B3 was less tolerant to ERS than the wild type, with decreased cell viability and increased apoptosis rates. Autophagy flux was depressed in mutant oligodendrocytes under baseline condition and after ERS stimulation. Reduced expression of autophagy related gene (Atg) 3 and Atg 7 were involved in the depression of autophagy flux. The mutant oligodendrocytes pretreated with autophagy inducers showed stable cell viability and decreased apoptosis despite ERS induction, whereas the autophagy inhibitors aggravated cell apoptosis and viability declination. CONCLUSIONS Oligodendrocytes transfected with mutant EIF2B3 was less tolerant to ERS than the wild type. Depressed autophagy flux was observed in the mutant cells at baseline and after ERS stimulation. Improperly depressed autophagy played a role in the susceptibility to ERS in EIF2B3 mutant oligodendrocytes.
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Affiliation(s)
- Na Chen
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Lifang Dai
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Yuwu Jiang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Jingmin Wang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Hongjun Hao
- Department of Neurology, Peking University First Hospital, Beijing 100034, China
| | - Yali Ren
- Lab of Electron Microscopy, Peking University First Hospital, Beijing 100034, China
| | - Xuerong Leng
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Lili Zang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Ye Wu
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China.
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Chen N, Jiang YW, Hao HJ, Ban TT, Gao K, Zhang ZB, Wang JM, Wu Y. Different Eukaryotic Initiation Factor 2Bε Mutations Lead to Various Degrees of Intolerance to the Stress of Endoplasmic Reticulum in Oligodendrocytes. Chin Med J (Engl) 2016; 128:1772-7. [PMID: 26112719 PMCID: PMC4733711 DOI: 10.4103/0366-6999.159353] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Background: Vanishing white matter disease (VWM), a human autosomal recessive inherited leukoencephalopathy, is due to mutations in eukaryotic initiation factor 2B (eIF2B). eIF2B is responsible for the initiation of protein synthesis by its guanine nucleotide exchange factor (GEF) activity. Mutations of eIF2B impair GEF activity at different degree. Previous studies implied improperly activated unfolded protein response (UPR) and endoplasmic reticulum stress (ERS) participated in the pathogenesis of VWM. Autophagy relieves endoplasmic reticulum load by eliminating the unfolded protein. It is still unknown the effects of genotypes on the pathogenesis. In this work, UPR and autophagy flux were analyzed with different mutational types. Methods: ERS tolerance, reflected by apoptosis and cell viability, was detected in human oligodendrocyte cell line transfected with the wild type, or different mutations of p. Arg113His, p. Arg269* or p. Ser610-Asp613del in eIF2Bε. A representative UPR-PERK component of activating transcription factor 4 (ATF4) was measured under the basal condition and ERS induction. Autophagy was analyzed the flux in the presence of lysosomal inhibitors. Results: The degree of ERS tolerance varied in different genotypes. The truncated or deletion mutant showed prominent apoptosis cell viability declination after ERS induction. The most seriously damaged GEF activity of p. Arg269* group underwent spontaneous apoptosis. The truncated or deletion mutant showed elevated ATF4 under basal as well as ERS condition. Decreased expression of LC3-I and LC3-II in the mutants reflected an impaired autophagy flux, which was more obvious in the truncated or deletion mutants after ERS induction. Conclusions: GEF activities in different genotypes could influence the cell ERS tolerance as well as compensatory pathways of UPR and autophagy. Oligodendrocytes with truncated or deletion mutants showed less tolerable to ERS.
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Affiliation(s)
| | | | | | | | | | | | | | - Ye Wu
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
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Differential activation of ER stress pathways in myelinating cerebellar tracts. Int J Dev Neurosci 2015; 47:347-60. [PMID: 26297908 DOI: 10.1016/j.ijdevneu.2015.08.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 08/12/2015] [Accepted: 08/13/2015] [Indexed: 11/22/2022] Open
Abstract
Myelin production during brain development requires an increase in membrane protein and lipid production in oligodendrocytes and this primarily occurs in the endoplasmic reticulum (ER), an organelle which initiates the Unfolded Protein Response (UPR) when under stress. We hypothesise that the UPR is activated in white matter tracts during myelination in order to expand the ER capacity of oligodendrocytes. Using early and late stage markers, critical myelination time points were identified by immunohistochemistry in developing rat cerebellum. These were correlated to peaks in ER stress signalling by staining for activated UPR transducers (pIRE1, ATF6 and pPERK) and associated downstream molecules (peIF2α, PDI, GRP78, GRP94, CHOP and calreticulin) in cerebellar tracts III and IV. Gene expression in developing cerebellum was assessed by qPCR. Actively myelinating tracts were shown to have differential expression of pIRE1, PERK and ATF6 as well as UPR targets GRP94, GRP78 and PDI. Activated pIRE1-positive cells were widespread at P14 and P17 and at significantly higher numbers during myelination than at other stages. Nuclear-localised ATF6 (indicative of the active transcription factor) peaked at P10, concurrent with the initial phase of myelination. The percentage of cells positive for pPERK was less than 1% at postnatal ages but increased significantly in adult tissue. The downstream targets GRP78, GRP94 and PDI were significantly up-regulated at P17 compared to P7 and remained significantly elevated in adults. The majority of cells positive for these markers and ATF6 were oligodendrocytes as confirmed by dual-labelling. Although gene expression in the cerebellum for GRP78, GRP94 and PDI did not change significantly over time, ATF6 and XBP1s both showed significant fold changes between early and late timepoints. This data helps promote understanding of events occurring during developmental myelination and may have implications for the development of reparative treatments in diseases such as multiple sclerosis.
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Transcriptional expression of myelin basic protein in oligodendrocytes depends on functional syntaxin 4: a potential correlation with autocrine signaling. Mol Cell Biol 2014; 35:675-87. [PMID: 25512606 DOI: 10.1128/mcb.01389-14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Myelination of axons by oligodendrocytes is essential for saltatory nerve conduction. To form myelin membranes, a coordinated synthesis and subsequent polarized transport of myelin components are necessary. Here, we show that as part of the mechanism to establish membrane polarity, oligodendrocytes exploit a polarized distribution of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) machinery components syntaxins 3 and 4, localizing to the cell body and the myelin membrane, respectively. Our data further reveal that the expression of myelin basic protein (MBP), a myelin-specific protein that is synthesized "on site" after transport of its mRNA, depends on the correct functioning of the SNARE machinery, which is not required for mRNA granule assembly and transport per se. Thus, downregulation and overexpression of syntaxin 4 but not syntaxin 3 in oligodendrocyte progenitor cells but not immature oligodendrocytes impeded MBP mRNA transcription, thereby preventing MBP protein synthesis. The expression and localization of another myelin-specific protein, proteolipid protein (PLP), was unaltered. Strikingly, conditioned medium obtained from developing oligodendrocytes was able to rescue the block of MBP mRNA transcription in syntaxin 4-downregulated cells. These findings indicate that the initiation of the biosynthesis of MBP mRNA relies on a syntaxin 4-dependent mechanism, which likely involves activation of an autocrine signaling pathway.
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Tanaka M, Izawa T, Yamate J, Franklin RJM, Kuramoto T, Serikawa T, Kuwamura M. The VF rat with abnormal myelinogenesis has a mutation in Dopey1. Glia 2014; 62:1530-42. [PMID: 24863653 DOI: 10.1002/glia.22698] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 04/30/2014] [Accepted: 05/07/2014] [Indexed: 11/09/2022]
Abstract
The vacuole formation (VF) rat is an autosomal recessive myelin mutant characterized by generalized tremor, hypomyelination, and periaxonal vacuole formation of the central nervous system (CNS). Here, we report the most likely causative gene for neurological disease in the VF rat and pursue its roles in the development and maintenance of the CNS myelin. We identified a nonsense mutation in the dopey family member 1 (Dopey1) located on rat chromosome 8. Expression level of Dopey1 mRNA was decreased and DOPEY1 protein was undetectable both in the white and gray matter of the spinal cords in the VF rats. Double immunohistochemistry demonstrated that DOPEY1 was mainly expressed in neurons and oligodendrocytes in the wild-type rats, whereas no positive cells were detected in the VF rats. We also demonstrated a marked reduction in myelin components both at mRNA and protein levels during myelinogenesis in the VF rats. In addition, proteolipid protein and myelin-associated glycoprotein accumulated in oligodendrocyte cell body, suggesting that Dopey1 is likely to be involved in the traffic of myelin components. Our results highlighted the importance of Dopey1 for the development and maintenance of the CNS myelin.
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Affiliation(s)
- Miyuu Tanaka
- Laboratory of Veterinary Pathology, Osaka Prefecture University, Izumisano, Osaka, 598-8531, Japan
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Myelin Proteome Analysis: Methods and Implications for the Myelin Cytoskeleton. THE CYTOSKELETON 2013. [DOI: 10.1007/978-1-62703-266-7_15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Identification of a gene regulatory network necessary for the initiation of oligodendrocyte differentiation. PLoS One 2011; 6:e18088. [PMID: 21490970 PMCID: PMC3072388 DOI: 10.1371/journal.pone.0018088] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 02/20/2011] [Indexed: 11/19/2022] Open
Abstract
Differentiation of oligodendrocyte progenitor cells (OPCs) into mature oligodendrocytes requires extensive changes in gene expression, which are partly mediated by post-translational modifications of nucleosomal histones. An essential modification for oligodendrocyte differentiation is the removal of acetyl groups from lysine residues which is catalyzed by histone deacetylases (HDACs). The transcriptional targets of HDAC activity within OPCs however, have remained elusive and have been identified in this study by interrogating the oligodendrocyte transcriptome. Using a novel algorithm that allows clustering of gene transcripts according to expression kinetics and expression levels, we defined major waves of co-regulated genes. The initial overall decrease in gene expression was followed by the up-regulation of genes involved in lipid metabolism and myelination. Functional annotation of the down-regulated gene clusters identified transcripts involved in cell cycle regulation, transcription, and RNA processing. To define whether these genes were the targets of HDAC activity, we cultured rat OPCs in the presence of trichostatin A (TSA), an HDAC inhibitor previously shown to inhibit oligodendrocyte differentiation. By overlaying the defined oligodendrocyte transcriptome with the list of 'TSA sensitive' genes, we determined that a high percentage of 'TSA sensitive' genes are part of a normal program of oligodendrocyte differentiation. TSA treatment increased the expression of genes whose down-regulation occurs very early after induction of OPC differentiation, but did not affect the expression of genes with a slower kinetic. Among the increased 'TSA sensitive' genes we detected several transcription factors including Id2, Egr1, and Sox11, whose down-regulation is critical for OPC differentiation. Thus, HDAC target genes include clusters of co-regulated genes involved in transcriptional repression. These results support a de-repression model of oligodendrocyte lineage progression that relies on the concurrent down-regulation of several inhibitors of differentiation.
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Myelin Restoration: Progress and Prospects for Human Cell Replacement Therapies. Arch Immunol Ther Exp (Warsz) 2011; 59:179-93. [DOI: 10.1007/s00005-011-0120-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Accepted: 11/17/2010] [Indexed: 12/12/2022]
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Rodriguez-Gabin AG, Ortiz E, Demoliner K, Si Q, Almazan G, Larocca JN. Interaction of Rab31 and OCRL-1 in oligodendrocytes: its role in transport of mannose 6-phosphate receptors. J Neurosci Res 2010; 88:589-604. [PMID: 19795375 DOI: 10.1002/jnr.22236] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Rab31, a protein that we cloned from an oligodendrocyte cDNA library, is required for transport of mannose 6-phosphate receptors (MPRs) from the trans-Golgi network (TGN) to endosomes and for Golgi/TGN organization. Here we extend the knowledge of the mechanism of action of Rab31 by demonstrating its interaction with OCRL-1, a phosphatidylinositol 4,5-diphosphate 5-phosphatase (PI(4,5)P(2) 5-phosphatase) that regulates the levels of PI(4,5)P(2) and PI(4)P, molecules involved in transport and Golgi/TGN organization. We show that Rab31 interacts with OCRL-1 in a yeast two-hybrid system, GST-Rab31 pull-down experiments, and coimmunoprecipitation of OCRL-1 using oligodendrocyte culture lysates. Rab31 and OCRL-1 colocalize in the TGN, post-TGN carriers, and endosomes. Cation-dependent MPR (CD-MPR) is sorted to OCRL-1-containing carriers, but CD63 and vesicular stomatitis virus G (VSVG) are not. siRNA-mediated depletion of endogenous Rab31 causes collapse of the TGN apparatus and markedly decreases the levels of OCRL-1 in the TGN and endosomes. Our observations indicate that the role of Rab31 in the Golgi/TGN structure and transport of MPRs depends on its capability to recruit OCRL-1 to domains of the TGN where the formation of carriers occurs. The importance of our observations is highlighted by the fact that mutation of OCRL-1 causes demyelination in humans.
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Affiliation(s)
- A G Rodriguez-Gabin
- Department of Neurology, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461, USA
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Age- and brain region-specific effects of dietary vitamin K on myelin sulfatides. J Nutr Biochem 2010; 21:1083-8. [PMID: 20092997 DOI: 10.1016/j.jnutbio.2009.09.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Revised: 07/13/2009] [Accepted: 09/17/2009] [Indexed: 02/06/2023]
Abstract
Dysregulation of myelin sulfatides is a risk factor for cognitive decline with age. Vitamin K is present in high concentrations in the brain and has been implicated in the regulation of sulfatide metabolism. Our objective was to investigate the age-related interrelation between dietary vitamin K and sulfatides in myelin fractions isolated from the brain regions of Fischer 344 male rats fed one of two dietary forms of vitamin K: phylloquinone or its hydrogenated form, 2',3'-dihydrophylloquinone (dK), for 28 days. Both dietary forms of vitamin K were converted to menaquinone-4 (MK-4) in the brain. The efficiency of dietary dK conversion to MK-4 compared to dietary phylloquinone was lower in the striatum and cortex, and was similar to that in the hippocampus. There were significant positive correlations between sulfatides and MK-4 in the hippocampus (phylloquinone-supplemented diet, 12 and 24 months; dK-supplemented diet, 12 months) and cortex (phylloquinone-supplemented diet, 12 and 24 months). No significant correlations were observed in the striatum. Furthermore, sulfatides in the hippocampus were significantly positively correlated with MK-4 in serum. This is the first attempt to establish and characterize a novel animal model that exploits the inability of dietary dK to convert to brain MK-4 to study the dietary effects of vitamin K on brain sulfatide in brain regions controlling motor and cognitive functions. Our findings suggest that this animal model may be useful for investigation of the effect of the dietary vitamin K on sulfatide metabolism, myelin structure and behavior functions.
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Harris LW, Lockstone HE, Khaitovich P, Weickert CS, Webster MJ, Bahn S. Gene expression in the prefrontal cortex during adolescence: implications for the onset of schizophrenia. BMC Med Genomics 2009; 2:28. [PMID: 19457239 PMCID: PMC2694209 DOI: 10.1186/1755-8794-2-28] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Accepted: 05/20/2009] [Indexed: 12/25/2022] Open
Abstract
Background Many critical maturational processes take place in the human brain during postnatal development. In particular, the prefrontal cortex does not reach maturation until late adolescence and this stage is associated with substantial white matter volume increases. Patients with schizophrenia and other major psychiatric disorders tend to first present with overt symptoms during late adolescence/early adulthood and it has been proposed that this developmental stage represents a "window of vulnerability". Methods In this study we used whole genome microarrays to measure gene expression in post mortem prefrontal cortex tissue from human individuals ranging in age from 0 to 49 years. To identify genes specifically altered in the late adolescent period, we applied a template matching procedure. Genes were identified which showed a significant correlation to a template showing a peak of expression between ages 15 and 25. Results Approximately 2000 genes displayed an expression pattern that was significantly correlated (positively or negatively) with the template. In the majority of cases, these genes in fact reached a plateau during adolescence with only subtle changes thereafter. These include a number of genes previously associated with schizophrenia including the susceptibility gene neuregulin 1 (NRG1). Functional profiling revealed peak expression in late adolescence for genes associated with energy metabolism and protein and lipid synthesis, together with decreases for genes involved in glutamate and neuropeptide signalling and neuronal development/plasticity. Strikingly, eight myelin-related genes previously found decreased in schizophrenia brain tissue showed a peak in their expression levels in late adolescence, while the single myelin gene reported increased in patients with schizophrenia was decreased in late adolescence. Conclusion The observed changes imply that molecular mechanisms critical for adolescent brain development are disturbed in schizophrenia patients.
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Affiliation(s)
- Laura W Harris
- Institute of Biotechnology, University of Cambridge, Cambridge, UK.
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Regulated release of BDNF by cortical oligodendrocytes is mediated through metabotropic glutamate receptors and the PLC pathway. ASN Neuro 2009; 1:AN20090006. [PMID: 19570026 PMCID: PMC2695578 DOI: 10.1042/an20090006] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A number of studies suggest that OLGs (oligodendrocytes), the myelinating cells of the central nervous system, are also a source of trophic molecules, such as neurotrophins that may influence survival of proximate neurons. What is less clear is how the release of these molecules may be regulated. The present study investigated the effects of BDNF (brain-derived neurotrophic factor) derived from cortical OLGs on proximate neurons, as well as regulatory mechanisms mediating BDNF release. Initial work determined that BDNF derived from cortical OLGs increased the numbers of VGLUT1 (vesicular glutamate transporter 1)-positive glutamatergic cortical neurons. Furthermore, glutamate acting through metabotropic, and not AMPA/kainate or NMDA (N-methyl-d-aspartate), receptors increased BDNF release. The PLC (phospholipase C) pathway is a key mediator of metabotropic actions to release BDNF in astrocytes and neurons. Treatment of OLGs with the PLC activator m-3M3FBS [N-(3-trifluoromethylphenyl)-2,4,6-trimethylbenzenesulfonamide] induced robust release of BDNF. Moreover, release elicited by the metabotropic receptor agonist ACPD [trans-(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid] was inhibited by the PLC antagonist U73122, the IP3 (inositol triphosphate 3) receptor inhibitor 2-APB (2-aminoethoxydiphenylborane) and the intracellular calcium chelator BAPTA/AM [1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid tetrakis(acetoxymethyl ester)]. Taken together, these results suggest that OLG lineage cells release BDNF, a molecule trophic for proximate neurons. BDNF release is regulated by glutamate acting through mGluRs (metabotropic glutamate receptors) and the PLC pathway. Thus glutamate and BDNF may be molecules that support neuron-OLG interactions in the cortex.
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Key Words
- brain-derived neurotrophic factor (bdnf)
- metabotropic glutamate receptor
- oligodendrocyte
- phospholipase c
- acpd, trans-(1s,3r)-1-aminocyclopentane-1,3-dicarboxylic acid
- 2-apb, 2-aminoethoxydiphenylborane
- bapta/am, 1,2-bis-(o-aminophenoxy)ethane-n,n,n′,n′-tetra-acetic acid tetrakis(acetoxymethyl ester
- bdnf, brain-derived neurotrophic factor
- bf, basal forebrain
- cc, corpus callosal
- cns, central nervous system
- dcg-iv, (2s,2′r,3′r)-2-(2′,3′-dicarboxycyclopropyl)glycine
- dhpg, (rs)-3,5-dihydroxyphenylglycine
- dmso, dimethyl sulfoxide
- ecl, enhanced chemiluminescence
- gdnf, glial cell line-derived neurotrophic factor
- igf-1, insulin-like growth factor-1
- ip3, inositol trisphosphate
- mcpg, (s)-α-methyl-4-carboxyphenylglycine
- mem, minimal essential medium
- mglur, metabotropic glutamate receptor
- m-3m3fbs, n-(3-trifluoromethylphenyl)-2,4,6-trimethylbenzenesulfonamide
- nm-15, nutrient medium-15
- nmda, n-methyl-d-aspartate
- nsfm, neuron serum-free medium
- nt, neurotrophin
- ocm, oligodendrocyte-derived conditioned medium
- olg, oligodendrocyte
- osfm, olg serum-free medium
- plc, phospholipase c
- vamp2, vesicle-associated membrane protein 2
- vglut1, vesicular glutamate transporter 1
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16
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Silva JM, Wong A, Carelli V, Cortopassi GA. Inhibition of mitochondrial function induces an integrated stress response in oligodendroglia. Neurobiol Dis 2009; 34:357-65. [PMID: 19233273 DOI: 10.1016/j.nbd.2009.02.005] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 01/26/2009] [Accepted: 02/06/2009] [Indexed: 11/24/2022] Open
Abstract
Maternal inheritance of a pathogenic point mutation within complex I of the mitochondrial genome causes Leber's hereditary optic neuropathy (LHON), resulting in the neurodegeneration and demyelination of the optic nerve. The integrated stress response (ISR), a signaling pathway that responds to various stresses by activating a common set of genes, has been linked to both mitochondrial defects and demyelinating diseases. Therefore, we wanted to determine whether mitochondrial dysfunction induced by complex I inhibition with rotenone can activate the ISR, specifically by the ER kinase PERK, in oligodendroglial cells. Our complex I-deficient oligodendroglial model reproduced similar biochemical defects as in LHON by decreasing ATP synthesis and ATP levels. The same doses of rotenone that reduced ATP production also induced dose-dependent increases in PERK and eIF2alpha phosphorylation as well as activated the ISR stress genes, ATF4 and CHOP. In addition, complex I inhibition at these same concentrations induced a PERK-dependent activation of the cell death kinase, JNK, and inhibited oligodendroglial proliferation. Taken together, our results demonstrate that activation of the ISR may be one example of mitochondrial retrograde signaling in response to complex I deficiency and we suggest that this response mechanism may be relevant to the pathophysiology of LHON.
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Affiliation(s)
- Jillian M Silva
- Department of Molecular Biosciences, University of California, Davis, 95616, USA
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17
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Katsel P, Davis KL, Li C, Tan W, Greenstein E, Kleiner Hoffman LB, Haroutunian V. Abnormal indices of cell cycle activity in schizophrenia and their potential association with oligodendrocytes. Neuropsychopharmacology 2008; 33:2993-3009. [PMID: 18322470 DOI: 10.1038/npp.2008.19] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The goal of this study was to determine what signaling pathways may elicit myelin-specific gene expression deficits in schizophrenia (SZ). Microarray analyses indicated that genes associated with canonical cell cycle pathways were significantly affected in the anterior cingulate gyrus (ACG), the region exhibiting the most profound myelin-specific gene expression changes, in persons with SZ (N=16) as compared with controls (N=19). Detected gene expression changes of key regulators of G1/S phase transition and genes central to oligodendrocyte differentiation were validated using qPCR in the ACG in an independent cohort (Ns=45/34). The relative abundance of phosphorylated retinoblastoma protein (pRb) was increased in the white matter underlying the ACG in SZ subjects (Ns=12). The upregulation of cyclin D1 gene expression and the downregulation of p57(Kip2), accompanied by increased cyclin D/CDK4-dependent phosphorylation of pRb, acting as a checkpoint for G1/S phase transition, suggest abnormal cell cycle re-entry in postmitotic oligodendrocytes in SZ. Furthermore, gene expression profiling of brain samples from myelin mutant animal models, quaking and myelin-associated glycoprotein (MAG) null mice, showed that cell cycle gene expression changes were not a necessary consequence of the reduced gene expression of structural myelin proteins, such as MAG. While, quaking, a known modulator of cell cycle activity during oligodendrocyte differentiation impairs the expression of multiple myelin genes, including those that are affected in SZ. These data suggest that the normal patterns of cell cycle gene and protein expression are disrupted in SZ and that this disruption may contribute to the oligodendroglial deficits observed in SZ.
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Affiliation(s)
- Pavel Katsel
- Department of Psychiatry, The Mount Sinai School of Medicine, New York, NY 10468, USA.
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18
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Li J. Hypothesis of double polarization. J Neurol Sci 2008; 275:33-6. [PMID: 18706661 DOI: 10.1016/j.jns.2008.07.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2008] [Revised: 05/23/2008] [Accepted: 07/07/2008] [Indexed: 10/21/2022]
Abstract
Mutations in a large number of genes that encode ubiquitously expressed proteins have been found to selectively or predominantly cause neurological disorders. Speculation has been that impaired intra-axonal transport along the long-extended axons is responsible for this tissue specificity. However this hypothesis may be insufficient in that it does not account for the potential role of the glial cells that interact with axons. Both Schwann cells and oligodendrocytes are also long and polarized cells with extended membranes that concentrically wrap around the axon to form myelin. The resultant myelin is largely compacted, which prevents the transport of many intracellular materials or organelles from one end of the membrane to the other. However patent, non-compacted spaces in the myelin, such as Schmidt-Lanterman incisures or paranodal loops, are also long-extended cytoplasmic channels that extend from the cell body to the distal membranes and may also be subject to transport problems. The nervous system therefore distinguishes itself by having a double long-polarized cellular system. Both neurons and myelinating glia must transport materials long distances, making them vulnerable to a variety of insults; and both must interact with each other. Thus, vulnerability of the nervous system may derive from additive impairments not only in axonal transport, but also in glial transport and neuronal-glial interactions.
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Affiliation(s)
- Jun Li
- Department of Neurology, John D. Dingell VA Medical Center, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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19
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Tang BL, Chua CEL. SIRT2, tubulin deacetylation, and oligodendroglia differentiation. ACTA ACUST UNITED AC 2008; 65:179-82. [PMID: 18044719 DOI: 10.1002/cm.20253] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The mammalian silent information regulator 2 (SIRT2) is an NAD-dependent histone deacetylase with known roles in the regulation of the cell cycle. SIRT2 is also a tubulin deacetylase functioning as an early mitotic checkpoint, but its roles in regulating cytoplasmic microtubule dynamics were unknown. Novel findings now indicate that SIRT2 is specifically enriched in brain oligodendroglia, where it functions specifically in modulating the oligodendrocyte cytoskeleton during its differentiation and maturation.
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Affiliation(s)
- Bor Luen Tang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 8 Medical Drive, Singapore.
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20
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Winterstein C, Trotter J, Krämer-Albers EM. Distinct endocytic recycling of myelin proteins promotes oligodendroglial membrane remodeling. J Cell Sci 2008; 121:834-42. [DOI: 10.1242/jcs.022731] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The central nervous system myelin sheath is a multilayered specialized membrane with compacted and non-compacted domains of defined protein composition. How oligodendrocytes regulate myelin membrane trafficking and establish membrane domains during myelination is largely unknown. Oligodendroglial cells respond to neuronal signals by adjusting the relative levels of endocytosis and exocytosis of the major myelin protein, proteolipid protein (PLP). We investigated whether endocytic trafficking is common to myelin proteins and analyzed the endocytic fates of proteins with distinct myelin subdomain localization. Interestingly, we found that PLP, myelin-associated glycoprotein (MAG) and myelin-oligodendrocyte glycoprotein (MOG), which localize to compact myelin, periaxonal loops and abaxonal loops, respectively, exhibit distinct endocytic fates. PLP was internalized via clathrin-independent endocytosis, whereas MAG was endocytosed by a clathrin-dependent pathway, although both proteins were targeted to the late-endosomal/lysosomal compartment. MOG was also endocytosed by a clathrin-dependent pathway, but in contrast to MAG, trafficked to the recycling endosome. Endocytic recycling resulted in the association of PLP, MAG and MOG with oligodendroglial membrane domains mimicking the biochemical characteristics of myelin domains. Our results suggest that endocytic sorting and recycling of myelin proteins may assist plasma membrane remodeling, which is necessary for the morphogenesis of myelin subdomains.
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Affiliation(s)
- Christine Winterstein
- Department of Biology, Unit of Molecular Cell Biology, University of Mainz, Bentzelweg 3, 55128 Mainz, Germany
| | - Jacqueline Trotter
- Department of Biology, Unit of Molecular Cell Biology, University of Mainz, Bentzelweg 3, 55128 Mainz, Germany
| | - Eva-Maria Krämer-Albers
- Department of Biology, Unit of Molecular Cell Biology, University of Mainz, Bentzelweg 3, 55128 Mainz, Germany
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21
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Maier O, Hoekstra D, Baron W. Polarity Development in Oligodendrocytes: Sorting and Trafficking of Myelin Components. J Mol Neurosci 2008; 35:35-53. [DOI: 10.1007/s12031-007-9024-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2007] [Accepted: 11/13/2007] [Indexed: 12/15/2022]
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22
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Krämer-Albers EM, Bretz N, Tenzer S, Winterstein C, Möbius W, Berger H, Nave KA, Schild H, Trotter J. Oligodendrocytes secrete exosomes containing major myelin and stress-protective proteins: Trophic support for axons? Proteomics Clin Appl 2007; 1:1446-61. [PMID: 21136642 DOI: 10.1002/prca.200700522] [Citation(s) in RCA: 377] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Indexed: 01/21/2023]
Abstract
Oligodendrocytes synthesize the CNS myelin sheath by enwrapping axonal segments with elongations of their plasma membrane. Spatial and temporal control of membrane traffic is a prerequisite for proper myelin formation. The major myelin proteolipid protein (PLP) accumulates in late endosomal storage compartments and multivesicular bodies (MVBs). Fusion of MVBs with the plasma membrane results in the release of the intralumenal vesicles, termed exosomes, into the extracellular space. Here, we show that cultured oligodendrocytes secrete exosomes carrying major amounts of PLP and 2'3'-cyclic-nucleotide-phosphodiesterase (CNP). These exosomes migrated at the characteristic density of 1.10-1.14 g/mL in sucrose density gradients. Treatment of primary oligodendrocytes with the calcium-ionophore ionomycin markedly increased the release of PLP-containing exosomes, indicating that oligodendroglial exosome secretion is regulated by cytosolic calcium levels. A proteomic analysis of the exosomal fraction isolated by sucrose density centrifugation revealed in addition to PLP and CNP, myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG) as constituents of oligodendroglial exosomes, together with a striking group of proteins with proposed functions in the relief of cell stress. Oligodendroglial exosome secretion may contribute to balanced production of myelin proteins and lipids, but in addition exosomes may embody a signaling moiety involved in glia-mediated trophic support to axons.
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23
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Olkkonen VM, Ikonen E. When intracellular logistics fails--genetic defects in membrane trafficking. J Cell Sci 2007; 119:5031-45. [PMID: 17158910 DOI: 10.1242/jcs.03303] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The number of human genetic disorders shown to be due to defects in membrane trafficking has greatly increased during the past five years. Defects have been identified in components involved in sorting of cargo into transport carriers, vesicle budding and scission, movement of vesicles along cytoskeletal tracks, as well as in vesicle tethering, docking and fusion at the target membrane. The nervous system is extremely sensitive to such disturbances of the membrane trafficking machinery, and the majority of these disorders display neurological defects--particularly diseases affecting the motility of transport carriers along cytoskeletal tracks. In several disorders, defects in a component that represents a fundamental part of the trafficking machinery fail to cause global transport defects but result in symptoms limited to specific cell types and transport events; this apparently reflects the redundancy of the transport apparatus. In groups of closely related diseases such as Hermansky-Pudlak and Griscelli syndromes, identification of the underlying gene defects has revealed groups of genes in which mutations lead to similar phenotypic consequences. New functionally linked trafficking components and regulatory mechanisms have thus been discovered. Studies of the gene defects in trafficking disorders therefore not only open avenues for new therapeutic approaches but also significantly contribute to our knowledge of the fundamental mechanisms of intracellular membrane transport.
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Affiliation(s)
- Vesa M Olkkonen
- Department of Molecular Medicine, National Public Health Institute (KTL), Biomedicum, POBox 104, FI-00251 Helsinki, Finland.
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24
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Thurnherr T, Benninger Y, Wu X, Chrostek A, Krause SM, Nave KA, Franklin RJM, Brakebusch C, Suter U, Relvas JB. Cdc42 and Rac1 signaling are both required for and act synergistically in the correct formation of myelin sheaths in the CNS. J Neurosci 2006; 26:10110-9. [PMID: 17021167 PMCID: PMC6674638 DOI: 10.1523/jneurosci.2158-06.2006] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The formation of myelin sheaths in the CNS is the result of a complex series of events involving oligodendrocyte progenitor cell (OPC) proliferation, directed migration, and the morphological changes associated with axon ensheathment and myelination. To examine the role of Rho GTPases in oligodendrocyte biology, we have used a conditional tissue-specific gene-targeting approach. Ablation of Cdc42 in cells of the oligodendrocyte lineage did not affect OPC proliferation, directed migration, or in vitro differentiation, but it led to the formation of a unique and stage-specific myelination phenotype. This was characterized by the extraordinary enlargement of the inner tongue of the oligodendrocyte process and concomitant formation of a myelin outfolding as a result of abnormal accumulation of cytoplasm in this region. Ablation of Rac1 also resulted in the abnormal accumulation of cytoplasm in the inner tongue of the oligodendrocyte process, and we provide genetic evidence that rac1 synergizes with cdc42 in a gene dosage-dependent way to regulate myelination.
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Affiliation(s)
- Tina Thurnherr
- Institute for Cell Biology, Department of Biology, Federal Institute of Technology (ETH) Zurich, CH-8093 Zurich, Switzerland
| | - Yves Benninger
- Institute for Cell Biology, Department of Biology, Federal Institute of Technology (ETH) Zurich, CH-8093 Zurich, Switzerland
| | - Xunwei Wu
- Department of Molecular Pathology, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Anna Chrostek
- Department of Molecular Medicine, Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany
| | - Sven M. Krause
- Institute for Cell Biology, Department of Biology, Federal Institute of Technology (ETH) Zurich, CH-8093 Zurich, Switzerland
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Goettingen, Germany, and
| | - Robin J. M. Franklin
- Cambridge Centre for Brain Repair and Neuroregeneration Laboratory, Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, United Kingdom
| | - Cord Brakebusch
- Department of Molecular Pathology, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Ueli Suter
- Institute for Cell Biology, Department of Biology, Federal Institute of Technology (ETH) Zurich, CH-8093 Zurich, Switzerland
| | - João B. Relvas
- Institute for Cell Biology, Department of Biology, Federal Institute of Technology (ETH) Zurich, CH-8093 Zurich, Switzerland
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25
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Abstract
Vanishing white matter disease (VWM) is one of the most prevalent inherited childhood leucoencephalopathies. The classical phenotype is characterised by early childhood onset of chronic neurological deterioration, dominated by cerebellar ataxia. VWM is unusual because of its clinically evident sensitivity to febrile infections, minor head trauma, and acute fright, which may cause rapid neurological deterioration and unexplained coma. Most patients die a few years after onset. The phenotypic variation is extremely wide, including antenatal onset and early demise and adult-onset, slowly progressive disease. MRI findings are diagnostic in almost all patients and are indicative of vanishing of the cerebral white matter. The basic defect of this striking disease resides in either one of the five subunits of eukaryotic translation initiation factor eIF2B. eIF2B is essential in all cells of the body for protein synthesis and its regulation under different stress conditions. Although the defect is in housekeeping genes, oligodendrocytes and astrocytes are predominantly affected, whereas other cell types are surprisingly spared. Recently, undue activation of the unfolded-protein response has emerged as important in the pathophysiology of VWM, but the selective vulnerability of glia for defects in eIF2B is poorly understood.
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Affiliation(s)
- Marjo S van der Knaap
- Department of Pediatrics and Child Neurology, VU University Medical Center, Amsterdam, Netherlands.
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26
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Schiffmann R, Elroy-Stein O. Childhood ataxia with CNS hypomyelination/vanishing white matter disease--a common leukodystrophy caused by abnormal control of protein synthesis. Mol Genet Metab 2006; 88:7-15. [PMID: 16378743 DOI: 10.1016/j.ymgme.2005.10.019] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2005] [Revised: 10/28/2005] [Accepted: 10/31/2005] [Indexed: 01/29/2023]
Abstract
Mutations in eukaryotic initiation factor 2B (eIF2B) cause one of the most common leukodystrophies, childhood ataxia with CNS hypomyelination/vanishing white matter disease or CACH/VWM. Patients may develop a wide spectrum of neurological abnormalities from prenatal-onset white matter disease to juvenile or adult-onset ataxia and dementia, sometimes with ovarian insufficiency. The pattern of diffuse white matter abnormalities on MRI of the head is often diagnostic. Neuropathological abnormalities indicate a unique and selective disruption of oligodendrocytes and astrocytes with sparing of neurons. Marked decrease of asialo-transferrin in cerebrospinal fluid is the only biochemical abnormality identified thus far. Eukaryotic translation initiation factor 2B (eIF2B) mutations cause a decrease in guanine nucleotide exchange activity on eIF2-GDP, resulting in increased susceptibility to stress and enhanced ATF4 expression during endoplasmic reticulum stress. eIF2B mutations are speculated to lead to increased susceptibility to various physiological stress conditions. Future research will be directed towards understanding why abnormal control of protein translation predominantly affects brain glial cells.
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Affiliation(s)
- Raphael Schiffmann
- Developmental and Metabolic Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
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27
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Kantor L, Harding HP, Ron D, Schiffmann R, Kaneski CR, Kimball SR, Elroy-Stein O. Heightened stress response in primary fibroblasts expressing mutant eIF2B genes from CACH/VWM leukodystrophy patients. Hum Genet 2005; 118:99-106. [PMID: 16041584 DOI: 10.1007/s00439-005-0024-x] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2005] [Accepted: 06/17/2005] [Indexed: 11/26/2022]
Abstract
Childhood ataxia with central nervous system hypomyelination (CACH), also called vanishing white matter (VWM) leukoencephalopathy, is a fatal genetic disease caused by mutations in eukaryotic initiation factor 2B (eIF2B) genes. The five subunits eIF2B factor is critical for translation initiation under normal conditions and regulates protein synthesis in response to cellular stresses. Primary fibroblasts from CACH/VWM patients and normal individuals were used to measure basal eIF2B activity as well as global protein synthesis and ATF4 induction in response to stress in the endoplasmic reticulum. We show that although the cells expressing mutant eIF2B genes respond normally to stress conditions by reduced global translation rates, they exhibit significantly greater increase in ATF4 induction compared to normal controls despite equal levels of stress and activity of the upstream eIF2alpha kinase. This heightened stress response observed in primary fibroblasts that suffer from minor loss of basal eIF2B activity may be employed as an initial screening tool for CACH/VWM leukodystrophy.
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Affiliation(s)
- Liraz Kantor
- Department of Cell Research & Immunology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, 69978, Israel
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28
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Saher G, Brügger B, Lappe-Siefke C, Möbius W, Tozawa RI, Wehr MC, Wieland F, Ishibashi S, Nave KA. High cholesterol level is essential for myelin membrane growth. Nat Neurosci 2005; 8:468-75. [PMID: 15793579 DOI: 10.1038/nn1426] [Citation(s) in RCA: 494] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Accepted: 02/25/2005] [Indexed: 01/07/2023]
Abstract
Cholesterol in the mammalian brain is a risk factor for certain neurodegenerative diseases, raising the question of its normal function. In the mature brain, the highest cholesterol content is found in myelin. We therefore created mice that lack the ability to synthesize cholesterol in myelin-forming oligodendrocytes. Mutant oligodendrocytes survived, but CNS myelination was severely perturbed, and mutant mice showed ataxia and tremor. CNS myelination continued at a reduced rate for many months, and during this period, the cholesterol-deficient oligodendrocytes actively enriched cholesterol and assembled myelin with >70% of the cholesterol content of wild-type myelin. This shows that cholesterol is an indispensable component of myelin membranes and that cholesterol availability in oligodendrocytes is a rate-limiting factor for brain maturation.
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MESH Headings
- 2',3'-Cyclic-Nucleotide Phosphodiesterases/metabolism
- Age Factors
- Animals
- Animals, Newborn
- Apolipoproteins E/metabolism
- Behavior, Animal
- Blotting, Northern/methods
- Blotting, Southern/methods
- Blotting, Western/methods
- Cell Membrane/metabolism
- Central Nervous System/metabolism
- Cholesterol/deficiency
- Cholesterol/physiology
- Chromatography, Thin Layer/methods
- Cloning, Molecular
- Creatine/metabolism
- Farnesyl-Diphosphate Farnesyltransferase/deficiency
- Farnesyl-Diphosphate Farnesyltransferase/genetics
- Farnesyl-Diphosphate Farnesyltransferase/metabolism
- Gene Expression Regulation, Developmental/physiology
- In Situ Hybridization/methods
- Lipid Metabolism
- Mass Spectrometry/methods
- Mice
- Mice, Inbred C57BL
- Mice, Mutant Strains/physiology
- Microscopy, Electron, Transmission/methods
- Microsomes/metabolism
- Myelin Proteolipid Protein/metabolism
- Myelin Sheath/metabolism
- Myelin Sheath/ultrastructure
- Oligodendroglia/metabolism
- Oligodendroglia/ultrastructure
- Phenotype
- Psychomotor Performance/physiology
- RNA/analysis
- Receptors, LDL/metabolism
- Silver Staining/methods
- Spinal Cord/metabolism
- Spinal Cord/ultrastructure
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Affiliation(s)
- Gesine Saher
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Goettingen, Germany
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29
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Reid SNM, Farber DB. Glial transcytosis of a photoreceptor-secreted signaling protein, retinoschisin. Glia 2005; 49:397-406. [PMID: 15538749 DOI: 10.1002/glia.20131] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In vitro studies have clearly shown that signaling/guidance proteins can diffuse to their targets. However, it is unclear whether they can travel by diffusion in vivo, or if they are distributed in the tissue by an active mechanism. Retinoschisin, a signaling molecule related to neuropilins, is synthesized and secreted by photoreceptor cells in the outer retina; then it interacts with inner retinal cells contributing to synaptic organization and optic nerve fiber integrity. We developed an assay to examine how retinoschisin, which is secreted a distance away, reaches its inner retinal targets. We found that retinoschisin is preferentially taken up and carried into the inner retina from the retinal outer border (the photoreceptor side) by Müller cells (the main glial cells of the vertebrate retina). This transcytosis is disrupted by DL-alpha-aminoadipic acid, a Müller cell/glia-specific toxin. Our results suggest that glial uptake/transcytosis can provide an effective and precise alternative for distributing signaling molecules in the nervous system.
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Affiliation(s)
- Silvia N M Reid
- Jules Stein Eye Institute, UCLA School of Medicine Center for the Health Sciences, 100 Stein Plaza, Los Angeles, CA 90095-7008, USA.
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30
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DeBruin LS, Haines JD, Wellhauser LA, Radeva G, Schonmann V, Bienzle D, Harauz G. Developmental partitioning of myelin basic protein into membrane microdomains. J Neurosci Res 2005; 80:211-25. [PMID: 15772981 DOI: 10.1002/jnr.20452] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Specific membrane microdomains (including lipid rafts) exist in myelin but have not been fully characterized. Myelin basic protein (MBP) maintains the compactness of the myelin sheath and is highly posttranslationally modified. Thus, it has been suggested that MBP might also have other functions, e.g., in signal transduction. Here, the distribution of MBP and its modified forms was studied, spatially and temporally, by detailed characterization of membrane microdomains from developing and mature bovine myelin. Myelin membranes were extracted with three different detergents (Brij 96V, CHAPS, or Triton X-100) at 4 degrees C. The detergent-resistant membranes (DRMs), representing coalesced lipid rafts, were isolated as low-buoyant-density fractions on a sucrose density gradient. These myelin rafts were disrupted when cholesterol was depleted with methyl-beta-cyclodextrin. The use of CHAPS detergent led to enrichment of several myelin proteins, including phospho-Thr97-MBP, in the DRMs from mature myelin. Citrullinated and methylated MBP remained in "nonraft" microdomains. In contrast, the DRMs from early myelin were enriched in Golli-MBP, Fyn, Lyn, and CNP. The localization of various proteins in DRMs was further supported by the colocalization of these lipid raft components in cultured mouse oligodendrocytes. Thus, there is a developmental regulation of posttranslationally modified forms of MBP into specific membrane microdomains.
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Affiliation(s)
- L S DeBruin
- Department of Molecular and Cellular Biology and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada
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