The Genes for Myelin Basic Protein in Normal and Shiverer Mutant Mice

Citation

Roach, Arthur Henry (1985) The Genes for Myelin Basic Protein in Normal and Shiverer Mutant Mice. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/4d7s-zs52. https://resolver.caltech.edu/CaltechTHESIS:01312019-172314851

Abstract

A cDNA library was constructed from the brains of 18 day old rats, and was screened with a synthetic DNA probe to yield clones representing myelin basic protein (MBP). One 1.9 kb clone was sequenced and found to encode the 14 kd MBP. Using this clone as a hybridization probe, cosmid clones from a library of wild type mouse DNA were selected and characterized. One clone was shown to carry five exons which encode 14 kd MBP, distributed over a 32 kb region. A sixth exon was detected with a synthetic DNA probe, and was found to encode the 41 amino acids which distinguish 18.5 kd from 14 kd MBP. The 5' end ot the gene was mapped with S1 nuclease protection and primer extension experiments to a position 47 bp 5' of the initator codon for MBP synthesis. It was shown that the gene cloned is probably the only MBP gene in the mouse genome.

Cloned DNAs were used to analyze the MBP gene and its expression in the myelin deficient mutant mouse shiverer. It was shown that a deletion has removed five out of six MBP exons, leaving only the 5'-most exon and 13 kb of the first intervening sequence. The deletion completely prevents expression of normal 2.1 kb MBP mRNAs, but a 16-fold lower number of transcripts are observed which initiate correctly at the 5' end of the first exon, are not correctly spliced, and are rarely polyadenylated. If translated, they would direct synthesis of a 61 amino acid peptide containing the first 56 amino acids of MBP. The MBP gene was mapped to mouse chromosome 18 by hybridization of MBP probes with DNA from Chinese hamster-mouse hybrid cell lines, showing it to be linked to the shiverer mutation. It is proposed that the partial deletion of the MBP gene is the primary lesion of the shiverer mutation.

Thesis Files