Molecular analysis of the domains of myelin basic protein involved in myelin compaction.
Item
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Title
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Molecular analysis of the domains of myelin basic protein involved in myelin compaction.
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Identifier
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AAI9807989
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identifier
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9807989
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Creator
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Rickman, David Stuart.
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Contributor
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Adviser: Robert A. Lazzarini
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Date
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1997
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Molecular | Biology, Neuroscience | Biology, Cell
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Abstract
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The myelin basic proteins (MBP) constitute a family of proteins that is found in the compact myelin around axons in the central and peripheral nervous systems (CNS and PNS, respectively). These different proteins result from an alternatively spliced message from a single 32 kb gene, and in mice, have molecular weights ranging from 14 kDa to 21 kDa. They are essential for the formation of compact myelin which is derived from elaborated processes of oligodendroglial cells (CNS) and Schwann cells (PNS), and when absent, as in the naturally occurring null mutant, the shiverer mouse, CNS myelination is blocked. The effects of this mutation have been rescued by expressing, transgenically, either the whole mbp gene (21) or the smallest isoform (8). To determine the domains of MBP that are involved in the compaction of myelin, I have made two truncated, nonnatural MBP cDNAs to be expressed in shiverer mice using an expression vector that is specific oligodendrocytes (44). These cDNAs, one expressing two exons (D2), the other expressing four exons (D4) of mbp were expressed in wild type (wt) mice for initial characterization. A short eleven amino acid tag sequence was appended to the carboxy terminal of each of the proteins, providing an epitope distinguishing them from endogenous MBP. The transgenes were genetically crossed onto the shiverer background, the D4 mini-MBP was able to facilitate myelin compaction and to partially rescue the dysmyelinating phenotype. D2, on the other hand, was unable to facilitate compaction despite robust expression levels and appropriate localization to the sheaths surrounding the axons. A cDNA encoding the endogenous isoform used in the above rescue experiment (8) with the appended tag sequence was employed as a control. Interestingly, one representative transgenic mouse line (on the wt background) for each cDNA developed a dysmyelinating pathology. This dissertation shows that a protein encoded by exons one, three, four and seven of mbp can facilitate the compaction of CNS myelin, while a protein encoded by a subset of these exons (exons one and seven of mbp) cannot. Therefore, the endogenous isoforms of MBP contain information that is not necessary in the compaction of CNS myelin, and thus may be important in other functions of MBP in the oligodendrocyte.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
