Expression Of Myelin Oligodendrocyte Glycoprotein Research Articles

Targeted Expression of Myelin Autoantigen in the Periphery Induces Antigen-Specific T and B Cell Tolerance and Ameliorates Autoimmune Disease.

There is a great interest in developing antigen-specific therapeutic approaches for the treatment of autoimmune diseases without compromising normal immune function. The key challenges are to control all antigen-specific lymphocyte populations that contribute to pathogenic inflammatory processes and to provide long-term protection from disease relapses. Here, we show that myelin oligodendrocyte glycoprotein (MOG)-specific tolerance can be established by ectopic expression of MOG in the immune organs. Using transgenic mice expressing MOG-specific CD4, CD8, and B cell receptors, we show that MOG expression in the bone marrow cells results in impaired development of MOG-specific lymphocytes. Ectopic MOG expression has also resulted in long-lasting protection from MOG-induced autoimmunity. This finding raises hope that transplantation of autoantigen-expressing bone marrow cells as a therapeutic strategy for specific autoantigen-driven autoimmune diseases.

Demyelination Occurred as the Secondary Damage Following Diffuse Axonal Loss in a Rat Model of Radiation Myelopathy.

The main purpose of the present study was to examine the time and dose-dependent course of demyelination in the rat radiation myelopathy model in the first 180days after irradiation of the spinal cord. An irradiated cervical spinal cord rat model (C2-T2 segment) was generated using a 60Co irradiator to deliver 50Gy and 100Gy, respectively. The behavioral dysfunction was observed by the forelimb paralysis scoring system. The histological damage in the irradiated spinal cord was examined by hematoxylin/eosin staining, luxol fast blue staining, immunohistochemical analysis, methylene blue/Azure II staining, and uranyl/lead salts staining. The gene expression of oligodendrocyte-related markers were also determined by quantitative real-time PCR. The complete loss of forelimb motor function in all animals was observed at 180days 50Gy post-irradiation and at 120 days 100Gy post-irradiation. We demonstrated that a 50 and 100-Gy single-dose irradiation of the C2-T2 spinal cord segment resulted in diffuse axonal loss and elicited secondary demyelination damage in the spinal cord. We further observed that 100-Gy irradiation reduced the gene expression of myelin oligodendrocyte glycoprotein in irradiated spinal cord. Taken together, our data not only define diffuse axonal loss as the main histological damage but also provide the first evidence that demyelination occurred as the secondary damage in irradiated spinal cord.

Tissue-specific antigens induce dual complementary T cell tolerance mechanisms

Abstract To understand tolerance mechanisms to tissue-specific antigens, we probed the development of polyclonal T cells specific for myelin oligodendrocyte glycoprotein (MOG), a myelin antigen targeted during autoimmune demyelinating disease. We find T cell tolerance occurs via two thymocyte selection processes. First, the presence of tissue-specific antigen intrinsically broadens the TCR repertoire to lower overall reactivity of effector T cells. Second, expression of MOG extrinsically induces a higher frequency of more efficacious antigen-specific Foxp3+ regulatory T cell population that prevents autoimmunity. Interestingly, clonal deletion mediated by thymocyte negative selection of high-affinity T cells was not apparent. Thus, cooperative tolerance exists to prevent autoimmunity towards tissue-specific antigens.

Administration of vitamin D3 induces CNPase and myelin oligodendrocyte glycoprotein expression in the cerebral cortex of the murine model of cuprizone-induced demyelination.

In the central nervous system (CNS) the main proteins of myelin are proteolipid protein (PLP), myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG) and CNPase. Myelin oligodendrocyte glycoprotein is a minor component of the myelin sheath, but is an important autoantigen linked to the pathogenesis of multiple sclerosis (MS). CNPase is expressed exclusively by oligodendrocytes in the CNS, and the appearance of CNPase seems to be one of the earliest events of oligodendrocyte differentiation and myelination. In this study the effects of vitamin D on total protein concentration, CNPase and MOG expression in the cerebral cortex of the murine model of cuprizone-induced demyelination was investigated. The mice were treated by cuprizone for five weeks in order to induce demyelination. The mice were then divided into 3 groups. The first group was injected intraperitoneally (IP) with vitamin D diluted in olive oil in the amount of 5 µg/kg/daily body weight. The second group (SHAM) was injected IP with olive oil and the third group was left without any injection as the control group (n = 11 for each group). After five weeks the mice were killed and the cerebral cortex was collected and the expression of CNPase and MOG was studied by Western blot. Total protein concentration in the vitamin D injected, SHAM and control groups were 0.918 ± 0.003, 0917 ± 0.004 and 0.916 ± 0.004 g/l, respectively (p > 0.05). However, a significant increase in the MOG and CNPase expression was seen in vitamin D injected group as compared to SHAM and control groups. It is concluded that vitamin D plays a role in the process of remyelination by increasing MOG and CNPase expression in the cortex.

Tolerance of activated pathogenic CD4+ T cells by transcriptional targeting of dendritic cells.

We have recently shown that targeted expression of myelin oligodendrocyte glycoprotein (MOG) to dendritic cells with self-inactivating-lentivirus vectors induces antigen-specific tolerance in naive antigen-specific CD4+ T cells and protects mice from experimental autoimmune encephalomyelitis (EAE). In the present study, we demonstrate that this approach also induces tolerance of activated antigen-specific CD4+ T cells and completely protects mice from passive EAE induction. Tolerance induction did not correlate with the depletion of the preactivated antigen-specific CD4+ T cells. However, upon isolation and in vitro re-stimulation at day 6 after adoptive transfer the MOG-specific CD4+ T cells from the non-tolerized mice produced large amounts of inflammatory cytokines, whereas those from tolerized mice did not. This unresponsiveness correlated with the upregulation of regulatory molecules associated with anergy and regulatory T cells (Tregs). The in vivo depletion of Tregs resulted in EAE susceptibility of the tolerized animals, suggesting that these cells have indeed a role in tolerance induction/maintenance.

Administration of embryonic stem cell-derived thymic epithelial progenitors expressing MOG induces antigen-specific tolerance and ameliorates experimental autoimmune encephalomyelitis

Tolerance induction, and thus prevention or treatment of autoimmune disease, is not only associated with the persistent presence of self-antigen in the thymus, but also relies on a functional thymus; however, the thymus undergoes profound age-dependent involution. Thymic epithelial cells (TECs) are the major component of the thymic microenvironment for T cell development. We have reported that mouse embryonic stem cells (mESCs) can be induced in vitro to generate thymic epithelial progenitors (TEPs) that further develop into functional TECs in vivo. We show here that transplantation of mESC-TEPs expressing self-antigen myelin oligodendrocyte glycoprotein (MOG) in mice results in enhanced T cell regeneration, long-term expression of MOG in the thymus, prevention of experimental autoimmune encephalomyelitis (EAE) development, and remission of established EAE. Our findings indicate that transplantation of ESC-TEPs expressing disease-causative self-antigen(s) may provide an effective approach for the prevention and treatment of autoimmune disease.

Ciliary Neurotrophic Factor Role in Myelin Oligodendrocyte Glycoprotein Expression in Cuprizone-Induced Multiple Sclerosis Mice

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system that leads to loss of myelin and oligodendrocytes and damage to axons. Myelin oligodendrocyte glycoprotein (MOG) is a minor component of the myelin sheath, but is an important autoantigen linked to the pathogenesis of MS. Ciliary neurotrophic factor (CNTF) has been shown to enhance the generation, maturation, and survival of oligodendrocytes in culture medium. The aim of this study was to demonstrate the role of CNTF on MOG expression in the cerebral cortex of Cuprizone-induced MS mice. The mice were treated by Cuprizone for five weeks in order to induce MS. The mice were then divided into 3 groups. The first group was injected subcutaneously (SC) by CNTF in the amount of 250μg/kg BW per day. The second group (SHAM) was injected SC by normal saline and the third group was left without injection as the control group. After four weeks the mice were killed and the cerebral cortex was harvested and the expression of MOG was studied by Western blotting. The data from this study show that the MOG expression was significantly increased in the CNTF-injected group as compared to the other groups. It is concluded that CNTF increases the MOG expression and may be important in the pathophysiology of MS. It is also concluded that CNTF may play a role in the process of remyelination by inducing the MOG expression.

Identification of the Myelin Oligodendrocyte Glycoprotein as a Cellular Receptor for Rubella Virus

Rubella virus (RV) is a highly transmissible pathogenic agent that causes the disease rubella. Maternal RV infection during early pregnancy causes the death of the fetus or congenital rubella syndrome in infants. However, the cellular receptor for RV has not yet been identified. In this study, we found that the myelin oligodendrocyte glycoprotein (MOG) specifically bound to the E1 envelope glycoprotein of RV, and an antibody against MOG could block RV infection. Most importantly, we also showed that ectopic expression of MOG on the cell surface of 293T cells rendered this nonpermissive cell line permissive for RV entry and replication. Thus, this study has identified a cellular receptor for RV and suggests that blocking the MOG attachment site of RV may be a strategy for molecular intervention of RV infection.

Resident B cells regulate thymic expression of myelin oligodendrocyte glycoprotein

Thymic B cells represent a numerically minor cell population located primarily at the cortico–medullary junction. Their biological role is unclear. B cell-deficient μMT mice exhibited reduced medullary thymic epithelial cell (mTEC) numbers and reduced MOG and insulin mRNA expression. Lymphotoxin produced by B cells was critical for normal tissue restricted antigen (TRA) expression, suggesting that B cells regulate self-antigens through their production of LT. These results reveal an unexpected role of B cells in mTEC maintenance and expression of TRAs through their production of LT.

Prevention and diminished expression of experimental autoimmune encephalomyelitis by low dose naltrexone (LDN) or opioid growth factor (OGF) for an extended period: Therapeutic implications for multiple sclerosis

Endogenous opioids inhibit the onset and progression of experimental autoimmune encephalomyelitis (EAE) with 30days of treatment. This study examined the long term effects of the opioid growth factor (OGF, [Met5]-enkephalin) and a low dose of the opioid antagonist naltrexone (LDN) on expression of myelin oligodendrocyte glycoprotein (MOG)-induced EAE. C57BL/6 mice began receiving daily injections of 10mg/kg OGF (MOG+OGF), 0.1mg/kg naltrexone (MOG+LDN), or saline (MOG+Vehicle) at the time of EAE induction and continuing for 60days. In contrast to 100% of the MOG+Vehicle group with behavioral symptoms of EAE, 63% and 68% of the MOG+OGF and MOG+LDN mice expressed disease. Both severity and disease indices of EAE in OGF- and LDN-treated mice were notably decreased from MOG+Vehicle cohorts. By day 60, 6- and 3-fold more animals in the MOG+OGF and MOG+LDN groups, respectively, had a remission compared to MOG+Vehicle mice. Neuropathological studies revealed i) astrocyte activation and neuronal damage as early as day 10 (prior to behavioral symptoms) in all MOG-injected groups, ii) a significant reduction of activated astrocytes in MOG+OGF and MOG+LDN groups compared to MOG+Vehicle mice at day 30, and iii) no demyelination on day 60 in mice treated with OGF or LDN and not displaying disease symptoms. These results indicate that treatment with OGF or LDN had no deleterious long-term repercussions and did not exacerbate EAE, but i) halted progression of disease, ii) reversed neurological deficits, and iii) prevented the onset of neurological dysfunction across a considerable span of time.

Cell surface targeting of myelin oligodendrocyte glycoprotein (MOG) in the absence of endoplasmic reticulum molecular chaperones

Myelin oligodendrocyte glycoprotein (MOG) is a type I integral membrane glycoprotein that localizes to myelin sheaths in the central nervous system. MOG has important implications in multiple sclerosis, as pathogenic anti-MOG antibodies have been detected in the sera of multiple sclerosis patients. As a membrane protein, MOG achieves its native structure in the endoplasmic reticulum where its folding is expected to be controlled by endoplasmic reticulum chaperones. Calnexin, calreticulin, and ERp57 are essential components of the endoplasmic reticulum quality control where they assist in the proper folding of newly synthesized glycoproteins. In this study, we show that expression of MOG is not affected by the absence of the endoplasmic reticulum quality control proteins calnexin, calreticulin, or ERp57. We also show that calnexin forms complexes with MOG and these interactions might be glycan-independent. Importantly, we show that cell surface targeting of MOG is not disrupted in the absence of the endoplasmic reticulum chaperones. This article is part of a special issue entitled: 11th European Symposium on Calcium.

Targeting MOG expression to dendritic cells delays onset of experimental autoimmune disease

Haematopoietic stem cell (HSC) transfer coupled with gene therapy is a powerful approach to treating fatal diseases such as X-linked severe combined immunodeficiency. This ability to isolate and genetically manipulate HSCs also offers a strategy for inducing immune tolerance through ectopic expression of autoantigens. We have previously shown that retroviral transduction of bone marrow (BM) with vectors encoding the autoantigen, myelin oligodendrocyte glycoprotein (MOG), can prevent the induction of experimental autoimmune encephalomyelitis (EAE). However, ubiquitous cellular expression of autoantigen driven by retroviral promoters may not be the best approach for clinical translation and a targeted expression approach may be more acceptable. As BM-derived dendritic cells (DCs) play a major role in tolerance induction, we asked whether targeted expression of MOG, a target autoantigen in EAE, to DCs can promote tolerance induction and influence the development of EAE. Self-inactivating retroviral vectors incorporating the mouse CD11c promoter were generated and used to transduce mouse BM cells. Transplantation of gene-modified cells into irradiated recipients resulted in the generation of chimeric mice with transgene expression limited to DCs. Notably, chimeric mice transplanted with MOG-expressing BM cells manifest a significant delay in the development of EAE suggesting that targeted antigen expression to tolerogenic cell types may be a feasible approach to inducing antigen-specific tolerance.

Common variation in the MOG gene influences transcript splicing in humans

Multiple sclerosis (MS) is a complex autoimmune disease characterised by demyelinating lesions in the central nervous system (CNS) and myelin oligodendrocyte glycoprotein (MOG), a CNS-restricted protein expressed on the outer cell membrane of oligodendrocytes, has been linked with disease pathogenesis. We have investigated whether expression of MOG in post-mortem human brain tissue is associated with genetic variations in the MOG gene that have previously been associated with genetic susceptibility to MS (520G>A, rs3130253, V145I and 511G>C, rs2857766, V142L). Using quantitative reverse transcriptase PCR (qPCR), we found that the haplotype containing the 520A (rs3130253A, I145) allele is associated with a 1.7-fold increase in splicing of exon 2 to exon 3, which encodes the extracellular and transmembrane domains of MOG. Using predictive algorithms, we found that the 520G>A variant also alters a putative exonic splicing enhancer (ESE) involving the SC35 and SRp55 RNA-binding proteins, supporting the notion that this variation has a regulatory effect. No consistent differences in allele-specific expression were observed for any of the SNPs using the SNaPshot® method. In this exploratory study we have observed that changes in splicing, but not expression levels, are associated with common genetic variation in the MOG gene. Further work is now required to confirm these data and determine whether this altered MOG expression profile, which is predicted to be over-represented in Northern Europeans with MS, is relevant to the pathophysiology of this debilitating disease.

Inflammatory responses in aggregating rat brain cell cultures subjected to different demyelinating conditions

To study inflammatory reactions occurring in relation to demyelination, aggregating rat brain cell cultures were subjected to three different demyelinating insults, i.e., (i) lysophosphatidylcholine (LPC), (ii) interferon-γ combined with lipopolysaccharide (IFN-γ + LPS), and (iii) anti-MOG antibodies plus complement (α-MOG + C). Demyelination was assessed by measuring the expression of myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG), and the activity of 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNP). The accompanying inflammatory reactions were examined by the quantification of microglia-specific staining, by immunostaining for glial fibrillary acidic protein (GFAP), and by measuring the mRNA expression of a panel of inflammation-related genes. It was found that all three demyelinating insults decreased the expression of MBP and MOG, and induced microglial reactivity. LPC and α-MOG + C, but not IFN-γ + LPS, decreased CNP activity; they also caused the appearance of macrophagic microglia, and increased GFAP staining indicating astrogliosis. LPC affected also the integrity of neurons and astrocytes. LPC and IFN-γ + LPS upregulated the expression of the inflammation-related genes IL-6, TNF-α, Ccl5, Cxcl1, and iNOS, although to different degrees. Other inflammatory markers were upregulated by only one of the three insults, e.g., Cxcl2 by LPC; IL-1β and IL-15 by IFN-γ + LPS; and IFN-γ by α-MOG + C. These findings indicate that each of the three demyelinating insults caused distinct patterns of demyelination and inflammatory reactivity, and that of the demyelinating agents tested only LPC exhibited general toxicity.

Myelin glycoproteins targeted by lead in the rodent model of prolonged exposure

The aim of these experiments was to discern whether prolonged exposure of rats to lead (Pb) in water, as occurs in typical environmental exposure, affects the structure of myelin in the brain, the protein levels of the myelin glycoproteins myelin associated glycoprotein (MAG) and myelin oligodendrocyte glycoprotein (MOG). During chronic lead intoxication, Pb levels in myelin fractions significantly increases. Prolonged lead exposure was found to decrease the expression of both MAG and MOG to a similar degree (80–85% of control values). Additionally, the electron microscopic studies have indicated the existence of structural changes in the axonal myelin sheath by revealing disintegration of its multilamellar structure. These morphological disturbances in Pb-intoxicated rats were paralleled by changes in myelin membrane fluidity as measured by spectrofluorometry and electron paramagnetic resonance (EPR) techniques employing a fatty acid spin label. In Pb-treated rats, enhanced membrane fluidity was observed, as indicated both by decreased anisotropy of the membrane and decreased order parameter. These results suggest that Pb influences the integrity of the myelin sheath in brain of adult rats and decreased level of both glycoproteins may significantly contribute to that effect.

Redox regulation of cytokine-mediated inhibition of myelin gene expression in human primary oligodendrocytes

Multiple sclerosis (MS) is a chronic autoimmune demyelinating disorder of the central nervous system (CNS) of unknown etiology. Several studies have shown that demyelination in MS is caused by proinflammatory mediators which are released by perivascular infiltrates and/or activated glial cells. To understand if proinflammatory mediators such as IL (interleukin)-1β and TNF (tumor necrosis factor)-α are capable of modulating the expression of myelin-specific genes, we investigated the effect of these cytokines on the expression of myelin basic protein (MBP), 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase), myelin oligodendrocyte glycoprotein (MOG), and proteolipid protein (PLP) in human primary oligodendrocytes. Interestingly, both IL-1β and TNF-α markedly inhibited the expression of MOG, CNPase, and PLP but not MBP, the effect that was blocked by antioxidants such as N-acetylcysteine (NAC) and pyrrolidine dithiocarbamate (PDTC). Consistently, oxidants and prooxidants like H 2O 2 and diamide also markedly inhibited the expression of MOG, CNPase, and PLP. Furthermore, both IL-1β and TNF-α induced the production of H 2O 2. Taken together, these studies suggest that proinflammatory cytokines inhibit the expression of myelin genes in human primary oligodendrocytes through the alteration of cellular redox.

Myelin oligodendrocyte glycoprotein is expressed in the peripheral nervous system of rodents and primates

The myelin oligodendrocyte glycoprotein (MOG) is a minor CNS myelin-specific protein that is an important candidate autoantigen in multiple sclerosis. We now report that MOG mRNA transcripts are present in the peripheral nervous system of rodents and primates at levels approximately ten-fold lower than in brain as demonstrated by real time PCR. A major source of this signal are Schwann cells which are also shown to express MOG protein within their cytoplasm in vitro by immunohistochemistry. Expression of MOG by Schwann cells associated with tissue innervation may account for the widespread distribution of low levels of MOG mRNA transcripts, and potentially may provide a source of antigen that can influence the composition and function of the MOG-specific immune repertoire.

Genetic variation in myelin oligodendrocyte glycoprotein expression and susceptibility to experimental autoimmune encephalomyelitis

Myelin oligodendrocyte glycoprotein (MOG) is encoded within the RT1.M region of the rat MHC a susceptibility locus for MOG-induced experimental autoimmune encephalomyelitis (EAE). We report that the enhanced susceptibility of Brown Norway (BN) rats to MOG–EAE is associated with higher expression of MOG mRNA and protein in the nervous system than in the less susceptible Lewis (LEW) strain. MOG mRNA was also detected in the immune system, but there was no correlation with disease susceptibility. These results suggest that differences in the expression of MOG in the target organ, rather than in the immune system may influence susceptibility to MOG–EAE.

Myelin oligodendrocyte glycoprotein-specific T cell receptor transgenic mice develop spontaneous autoimmune optic neuritis.

Multiple sclerosis (MS) is considered to be an autoimmune disease of the central nervous system (CNS) that in many patients first presents clinically as optic neuritis. The relationship of optic neuritis to MS is not well understood. We have generated novel T cell receptor (TCR) transgenic mice specific for myelin oligodendrocyte glycoprotein (MOG). MOG-specific transgenic T cells are not deleted nor tolerized and are functionally competent. A large proportion (>30%) of MOG-specific TCR transgenic mice spontaneously develop isolated optic neuritis without any clinical nor histological evidence of experimental autoimmune encephalomyelitis (EAE). Optic neuritis without EAE could also be induced in these mice by sensitization with suboptimal doses of MOG. The predilection of these mice to develop optic neuritis is associated with higher expression of MOG in the optic nerve than in the spinal cord. These results demonstrate that clinical manifestations of CNS autoimmune disease will vary depending on the identity of the target autoantigen and that MOG-specific T cell responses are involved in the genesis of isolated optic neuritis.

Oligodendrocyte progenitor cells in the adult rat CNS express myelin oligodendrocyte glycoprotein (MOG).

While the effects of high dose X-irradiation on mitotically active progenitor cells and remyelination are well-documented, its effects on myelinating oligodendrocytes are less clear, due in part to divergent views on their mitotic capacity. To examine the effect of X-irradiation on oligodendrocytes, the spinal cord of rats was exposed to 40 Gy of X-irradiation and the number of oligodendrocytes and oligodendrocyte progenitors in the dorsal funiculi at T12 and L1 was determined by in situ hybridization using cRNA-probes for platelet derived growth factor alpha receptor (PDGFRalpha) (to identify oligodendrocyte progenitors), exon 3b of proteolipid protein (PLP) (to identify mature oligodendrocytes) and myelin oligodendrocyte glycoprotein (MOG). X-irradiation resulted in no change in the number of PLP positive cells and no loss of myelin internodes, but caused an almost complete loss of PDGFRalpha-expressing cells, and a reduction in the number of MOG positive cells to a number similar to that found using the PLP exon 3b probe. Importantly, the number of radiation-sensitive MOG-expressing cells was similar to the number of PDGFRalpha positive cells. To determine if the radiation-sensitive MOG positive cells were the same population as the radiation sensitive PDGFRalpha-expressing cells, MOG and PDGFRalpha-expressing cells were isolated from the adult CNS using antibody coated magnetic beads. Twelve to thirteen percent of MOG positive cells were PDGFRalpha positive and nearly all the PDGFRa isolated cells were MOG and galactocerebroside positive. Double immunofluorescence revealed colocalization of NG2 and MOG on cells in the normal adult rat spinal cord. These results show that in situ in the adult rat spinal cord white matter oligodendrocyte progenitors are MOG positive and indicates that expression of MOG cannot be regarded a marker that only identifies mature myelin-supporting oligodendrocytes in tissue.