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Expression of Myelin Proteolipid Protein and Basic Protein in Normal and Dysmyelinating Mutant Mice
Author(s) -
Sorg Barbara J. A.,
Agrawal Daya,
Agrawal Harish C.,
Campagi Anthony T.
Publication year - 1986
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1986.tb12979.x
Subject(s) - proteolipid protein 1 , myelin , mutant , myelin proteolipid protein , myelin basic protein , protein expression , myelin sheath , chemistry , microbiology and biotechnology , biology , biochemistry , neuroscience , central nervous system , gene
Expression of myelin proteins was studied in the brains of 21‐day‐old normal mice and three dysmyelinating mutants—jimpy, quaking, and shiverer. Total brain polyribosomes and poly(A) + mRNA were translated in two cell‐free systems and the levels of synthesis of the myelin basic proteins (MBPs) and proteolipid protein (PLP) were determined. Synthesis of the MBPs in quaking homozygotes was at or above normal levels but PLP synthesis was significantly reduced to approximately 15% of control values, indicating independent effects on the expression of these proteins in this mutant. Immunoblot analysis of 21‐day‐old quaking brain homogenates showed a reduction in the steady‐state levels of MBPs and PLP, suggesting a failure of newly synthesized MBPs to be incorporated into a stable membrane structure such as myelin. In the shiverer mutant very little synthesis of MBPs was observed, whereas greater synthesis of PLP occurred (approximately 50% of control). Almost no MBP, and low levels of PLP, were detected in the immunoblots, suggesting the possibility of a partial failure of PLP to be assembled into myelin in shiverer. In the jimpy mutant, low levels of MBP synthesis were observed in vitro (approximately 26% of controls) and very little synthesis of PLP was evident. The immunoblots of 21‐day jimpy brain homogenates revealed no appreciable steady‐state levels of PLP or MBP, again indicating that most newly synthesized MBPs were not incorporated into a stable membrane structure in this mutant. In sum, the data show that in the three cases examined, the mutation appears to affect the expression of the MBPs and PLP independently. Furthermore, regardless of their absolute levels of synthesis these proteins may or may not be assembled into myelin.