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SUBCELLULAR DISTRIBUTION AND STRUCTURAL POLYMORPHISM OF MYELIN BASIC PROTEIN IN NORMAL AND JIMPY MOUSE BRAIN
Author(s) -
Barbarese E.,
Carson J. H.,
Braun P. E.
Publication year - 1979
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.1471-4159.1979.tb11082.x
Subject(s) - myelin , myelin basic protein , chemistry , biochemistry , microbiology and biotechnology , biology , central nervous system , endocrinology
— Brains from 20 day old normal and 20 day old Jimpy mice were fractionated by a modification of the procedure described by E ichberg et al. (1964). Each of the fractions obtained was subjected to radioimmunoassay (RIA) for myelin basic protein (MBP). From both the normal brain and the Jimpy brain MBP was recovered in three separate membrane fractions designated P1A. P2A. and P3A. which differed in their sedimentation properties but which had similar densities (less than 1.08 g'ml). In the Jimpy brain compared to normal brain the amounts of P1A and P2A were greatly reduced but the amount of P3A was increased. During development in the normal brain the amount of MBP in the PIA fraction increased in parallel with the accumulation of myelin. The amount of MBP in P2A increased gradually during active myelination and decreased slightly in the adult. The amount of MBP in P3A increased sharply during the period of most active myelination and decreased approx 10‐fold as the rate of myelination in the brain declined. Electron microscopic examination revealed that the P1A and P2A fractions from normal brain contained myelin fragments while the P1A and P2A fractions from Jimpy brain contained numerous vesicular membranous structures with little if any identifiable myelin. The P3A fraction from both normal and Jimpy brain contained small vesicles of uniform size, some with polyribosomes attached. Each of the fractions was analyzed by a technique combining sodium dodecyl sulfate polyacrylamide gel electrophoresis with RIA for MBP in order to identify and quantitate the four different forms of MBP with molecular weights of 21.5 K. 18.5 K. 17 K and 14 K dalton. The proportions of the four MBPs were characteristic for each fraction. The relative proportions of the four proteins were 14 K > 18.5 K > 17 K > 21.5 K daltons in all the fractions except P1A Jimpy in which 21.5 K dalton protein was the predominant form of MBP present. The cellular origin of the MBP containing fractions from normal and Jimpy brain is discussed.