Novel Isoforms of Mouse Myelin Basic Protein Predominantly Expressed in Embryonic Stage

Authors

  • Kazunori Nakajima,

    1. Division of Regulation of Macromolecular Function, Institute for Protein Research, Osaka University, Osaka, Japan
    2. Department of Molecular Neurobiology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
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  • Kazuhiro Ikenaka,

    Corresponding author
    1. Division of Regulation of Macromolecular Function, Institute for Protein Research, Osaka University, Osaka, Japan
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  • Tetsushi Kagawa,

    1. Division of Regulation of Macromolecular Function, Institute for Protein Research, Osaka University, Osaka, Japan
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  • Jun Aruga,

    1. Department of Molecular Neurobiology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
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  • Junji Nakao,

    1. Division of Regulation of Macromolecular Function, Institute for Protein Research, Osaka University, Osaka, Japan
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  • Kensuke Nakahira,

    1. Division of Regulation of Macromolecular Function, Institute for Protein Research, Osaka University, Osaka, Japan
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  • Chiyo Shiota,

    1. Division of Regulation of Macromolecular Function, Institute for Protein Research, Osaka University, Osaka, Japan
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    • Dr. C. Shiota is Department of Pathology, Wakayama Medical School, Wakayama, Japan.

  • Seung U. Kim,

    1. Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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  • Katsuhiko Mikoshiba

    1. Department of Molecular Neurobiology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
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Address correspondence and reprint requests to Dr. K. Ikenaka at Division of Regulation of Macromolecular Function, Institute for Protein Research, Osaka University, 3–2 Yamada-Oka, Suita, Osaka, 565, Japan.

Abstract

Abstract: Myelin basic protein (MBP), a major protein of myelin, is thought to play an important role in myelination, which occurs postnatally in mouse. Here we report that the MBP gene is expressed from the 12th embryonic day in mouse brain and that most of the predominant embryonic isoforms are not those reported previously. These isoforms have a deletion of a sequence encoded by exon 5 from the well-known isoforms. These isoforms show a unique developmental profile, i.e., they peak in the embryonic stage and decrease thereafter. In jimpy, a dysmyelinating mutant, the level of these isoforms remains high even in the older ages. These results suggest that MBPs have heretofore unknown functions unrelated to myelination before myelinogenesis begins. The possible presence of 18 isoforms of MBP mRNA, which are classified into at least three groups with different developmental profiles, is also reported here.

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