Evidence for the expression of four myelin basic protein variants in the developing human spinal cord through cDNA cloning

Abstract

Four human myelin basic protein (MBP) variants with molecular masses of 21.5, 20.2, 18.5, and 17.3 kilodaltons (kDa) have been identified in the developing human spinal cord and their structures determined through an analysis of cDNA clones of their mRNAs. The 20.2-kDa MBP mRNA encoded a novel MBP variant, the structure of which has not been reported in any species. Its amino acid sequence was identical with that of the 21.5-kDa MBP except for a deletion of 11 amino acid residues encoded by exon 5 of the MBP gene. All four human MBP variants were identical except for the insertion of deletion of two peptide fragments corresponding to those encoded by exons 2 and 5 of the MBP gene. In this study, no mature human MBP cDNAs missing exon 6 sequences were identified. This suggests that, unlike the mouse, the four human MBP mRNAs encoding these MBP variants arise by the alternative splicing of only exons 2 and 5 from the primary MBP gene transcript. This indicates that the predominant MBP splicing pathways in human and mouse are different. Immunoblots of human fetal spinal cords (11-21 weeks) indicated that MBP expression turned on abruptly between 14 and 16 weeks. Expression of the 20.2-kDa MBP variant was most evident at 16 weeks and its relative proportion declined thereafter, suggesting that its expression was developmentally regulated.

A study of human T-cell lines generated from multiple sclerosis patients and controls by stimulation with peptides of myelin basic protein

“…We were also able to generate, from 2 MS patients, T-cell lines reactive to a novel MBP epitope (peptide 10B) present in the 20.2 and 17.3 kDa isoforms but not in the 21.5 or 18.5 kDa isoforms. As the 21.5, 20.2 and 17.3 kDa isoforms are expressed in the developing human CNS (Roth et al, 1987), it has been suggested that they may also be expressed by remyelinating oligodendrocytes in MS lesions (Voskuhl et al, 1993a).…”

“…Overlapping synthetic peptides 20 amino acids in length were synthesized by the tea-bag method (Houghten, 1985), using the published sequences of the 18.5 kDa isoform of human MBP (Roth et al, 1987). Additional peptides were prepared to represent sequences from the deleted and inserted regions in the 21.5, 20.2 and 17.3 kDa isoforms of human MBP.…”

“…We used overlapping synthetic peptides representing the entire sequence of the most abundant isoform (18.5 kDa) of MBP and also the sequences of the 21.5, 20.2 and 17.3 kDa isoforms, which are expressed in the developing human CNS (Roth et al, 1987). It has been suggested that the minor isoforms may also be expressed by remyelinating oligodendrocytes and thus be potential T-cell targets in MS (Voskuhl et al, 1993a andVoskuhl et al, 1993b).…”

Increased non-canonical splicing of autoantigen transcripts provides the structural basis for expression of untolerized epitopes

“…Because immune responses to autoantigen epitopes are highly specific, 7 alternative splicing of exons could provide the structural basis for expression of novel untolerized antigen epitopes with altered antigenic properties and hence create the potential to break existing immune tolerance. 8,9 Previously, 19 autoantigens were identified as having alternatively spliced isoforms, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] suggesting that alternative splicing may indeed contribute to the regulated expression of autoantigens. In addition, a recent report showed that intrathymic expression of proteo-lipid protein (PLP) was largely restricted to the shorter splice variant DM20.…”

No evidence for transmission disequilibrium between a new marker at the myelin basic protein locus and multiple sclerosis in French patients

“…The MBP transcription unit consists of seven exons distributed over a length of 30 kb 11 and is part of a complex genetic locus called the Golli (for gene expessed in the oligodendrocyte lineage)-MBP on chromosome 18qter. This locus is over 165 kb in length and contains two transcription start sites, one which gives rise to four alternatively spliced MBP mRNAs 12,13 and another which produces at least three alternatively spliced Golli mRNAs that contain exons from the MBP transcription unit. [14][15][16] Both the Golli and MBP families are under independent developmental regulation.…”