Myelin/oligodendrocyte glycoprotein (MOG) is a primary target autoantigen in experimental autoimmune encephalomyelitis, a widely used animal model for autoimmune demyelinating diseases such as multiple sclerosis. We have isolated several rat MOG cDNAs and confirmed their identity by comparison with MOG N-terminal peptide sequence. As expected, MOG mRNA expression is CNS-specific and peaks during active myelination. Our studies show that full length MOG mRNA is approximately 1.6 kb and encodes a signal peptide of 27 amino acids, followed by 218 residues for mature MOG (24,962 MW). A single site for N-glycosylation is found at Asn-31. Rather than the ubiquitous AAUAAA polyadenylation signal, a series of three overlapping, rare poly A signals were identified. The N-terminal half of mature MOG shares 52% identity with bovine butyrophilin, a possible lipid receptor. This same region has 39% identity with chicken B-G antigen, a major histocompatibility complex antigen involved in B cell selection and immune repertoire development. We show that both MOG and butyrophilin, each exhibiting a single Ig-like variable region domain, meet criteria for inclusion in the immunoglobulin superfamily. Moreover, MOG appears to represent a unique member of this superfamily in that it possesses two potential transmembrane domains, in contrast to a single membrane-spanning domain or glycophospholipid anchor found in all other members of Ig superfamily members.

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This study addressed the possibility that proto-myb (also called c-myb), the cellular homolog of a retroviral transforming gene, plays a role in hemopoiesis, particularly during maturation of T cells. By gel blot hybridization, we confirmed previous reports that proto-myb transcripts are found at much higher levels in thymic lymphocytes and cells of the erythroid lineage than in other tissue sources. Using dot blot hybridizations, we demonstrated further that similar levels of proto-myb expression are found in thymic lymphocytes taken from young mice with active thymuses and from old mice whose thymuses have undergone involution and that the extent of proto-myb expression decreases at least 10-fold as T cells progress from immature cortical thymocytes to the mature, resting T cells taken from lymph nodes. These results suggest that the protein product of proto-myb functions during T-cell differentiation.

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The gene for the mouse myelin proteolipid protein has been isolated and the seven exons have been sequenced. Since the sequence of a rat proteolipid protein cDNA and partial sequence of the human proteolipid protein gene have been determined, it was possible to demonstrate a very high degree of conservation for the protelipid protein gene exons among species. While there are some nucleotide changes, the protein coding region of the mouse gene encodes protein that is totally conserved relative to both rat and human prteolipid proteins. The regulatory and noncoding regions of the proteolipid protein gene are also highly conserved. The upstream regulatory and 5′‐noncoding region of the gene is 92% homologous to the comparable region of the human proteolipid protein gene, and the 3′‐noncoding region of the mouse gene is approximately 90% homologous to a rat proteolipid protein cDNA through 2,200 nucleotides of 3′‐noncoding DNA.S1 nuclease protection experiments indicated that the major 5′‐end for proteolipid protein mRNAs from mouse, rat human, ro baboon is approximately 147–160 nucleotides upstream from the initial methionine codon of the protein coding region. Other S1 nuclease protection experiments indicated the possible existence of an alernative splice site within exon 3, which may produce mRNA for DM20. This mRNA is approximately 100 nucleotides shorter than that for the protelipid protein, and it is missing the latter half of exon 3, that is, amino acids 116–150 of the proteolipid protein sequence.

A clone specific for the rat myelin proteolipid protein (PLP) was isolated from a cDNA library made in pUC18 from 17-day-old rat brain stem mRNA. This clone corresponded to the carboxyl-terminal third of the PLP-coding region. The clone was used to identify PLP-specific mRNAs in mouse brain and to establish the time course of PLP mRNA expression during mouse brain development. Three PLP-specific mRNAs were seen, approximately 1,500, 2,400, and 3,200 bases in length, of which the largest was the most abundant. During brain development, the maximal period of PLP mRNA expression was from 14 to 25 days of age, and this was a similar time course to that for myelin basic protein mRNA expression. When the jimpy mouse, an X-linked dysmyelination mutant, was studied for PLP mRNA expression, low levels of PLP mRNA were seen which were approximately 5% of wild-type levels at 20 days of age. When jimpy brain RNA was analyzed by Northern blotting, the PLP-specific mRNA was shown to be 100 to 200 bases shorter than the wild-type PLP-specific mRNA. This size difference was seen in the two major PLP mRNAs, and it did not result from a loss of polyadenylation of these mRNAs.The biosynthesis of the myelin sheath is a crucial part of nervous system development, and as a result, the developmental expression of the myelin protein genes is highly regulated. The normal pattern of myelin protein expression in rodents indicates that little myelin protein expression occurs prenatally or in neonatal animals (2,5,6,8,23,26,28) and that myelin protein synthesis and accumulation increase significantly in the brain at about 10 days after birth, reaching a peak between 15 and 22 days after birth (2,5,6,8,23).Central nervous system myelin contains two major classes of proteins, myelin basic protein (MBP) and proteolipid protein (PLP), which together constitute as much as 80% of the total myelin protein (15,30). The four MBPs that are present in rodent myelin have homologous amino acid sequences, including identical amino-and carboxyl-terminal sequences but internal segments of unique amino acid sequence (3). They are translated from four different mRNAs (50), and the four MBP mRNAs can be produced from a single MBP gene by alternative mRNA splicing (12,44). Two PLPs are present in myelin, the major PLP, which has an apparent molecular weight of 25,000, and the closely related proteolipid DM20 (1), which has an apparent molecular weight of 20,000. PLP and DM20 may have a relationship similar to that found among the four MBPs, since they have identical amino-and carboxyl-terminal sequences (46), and they are very closely related by amino acid composition and by antigenic characteristics. The expression of these myelin proteins correlates closely with the formation of myelin in the developing rat brain, and mouse mutants that are defective in myelin formation show lowered levels of these myelin proteins (4,14,20,25 expression and the genetic deficiency in the shiverer mouse myelination mutant (12,34,44). Several groups have recently isolated cDNA ...

The myelin/oligodendrocyte glycoprotein (MOG) is found exclusively in the CNS, where it is localized on the surface of myelin and oligodendrocyte cytoplasmic membranes. The monoclonal antibody 8-18C5 identifies MOG. Several studies have shown that anti-MOG antibodies can induce demyelination, thus inferring an important role in myelin stability. In this study, we demonstrate that MOG consists of two polypeptides, with molecular masses of 26 and 28 kDa. This doublet becomes a single 25-kDa band after deglycosylation with trifluoromethanesulfonic acid or peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase, indicating that there are no or few O-linked sugars and that the doublet band represents differential glycosylation. Partial trypsin cleavage, which also gave a doublet band of lower molecular weight, confirmed this idea. MOG was purified by polyacrylamide gel electrophoresis, followed by electroelution. Three N-terminal sequences of eight to 26 amino acids were obtained. By western blot analysis, no binding was found between MOG and cerebellar soluble lectin. MOG does not seem to belong to the signal-transducing GTP-binding proteins. Reduced MOG concentrations were observed in jimpy and quaking dysmyelinating mutant mice, giving further support to its localization in compact myelin of the CNS.

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