The regulation of expression of the genes coding for myelin proteins is an important problem about which relatively little is known. The overall goal of this project is to examine the structural organization of these genes, beginning with those coding for the myelin basic proteins. In mice, four structurally-related myelin basic proteins exist and, although it is clear that four separate mRNAs code for these proteins, it is not yet known whether or not these proteins are specified by separate genes. With the availability of a cDNA probe to a part of the mouse myelin basic protein common to all four species, it is now possible to isolate MBP genes from a mouse genomic library and study their structure and organization. Two MBP clones have already been obtained which appear to be different from each other, suggesting that the mouse MBPs are coded for by more than one gene. These clones and the original cDNA clone will be used to determine the number of MBP genes in the mouse genome. Each gene will then be isolated from a genomic library and characterized by restriction enzyme analysis and sequencing of selected regions. The sequence information will be used to classify the MBP genes according to the type of MBP protein each codes for. The sequences will also be examined to identify potential regulatory sequences and splice sites and correlated with R-looping results and sequence data from cloned hybrid selected MBP mRNAs to identify introns. In the process of isolating and sequencing these genes, fragments of the genes will be subcloned and these fragments may prove to contain unique sequences which might be used as probes to discriminate the various MBP genes. The MBP cDNA probe will also permit the examination of the structure of the MBP genes in the dysmyelinating mutant mice, jimpy and shiverer. These two dysmyelinating mutants are defective in their ability to synthesize normal levels of the myelin basic proteins. Southern blots will be used to determine whether gross alterations exist in the structures of the MBP genes in these mutants. In addition, genomic libraries of the mutants will be prepared and the MBP genes will be isolated from these libraries and studied for sequence differences which may account for the mutant phenotype. In this way, structural alterations in the MBP genes or their controlling elements will be identified.
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