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Multiple roles of Id4 in developmental myelination: Predicted outcomes and unexpected findings

Authors

  • Mireya Marin-Husstege,

    1. Department of Neuroscience and Cell Biology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey
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    • M. MH & Y. H. contributed equally to this work.

  • Ye He,

    1. Department of Neuroscience and Cell Biology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey
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    • M. MH & Y. H. contributed equally to this work.

  • Jiadong Li,

    1. Department of Neuroscience and Cell Biology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey
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  • Toru Kondo,

    1. Centre for Brain Repair, University of Cambridge, The E. D. Adrian Building, Cambridge, United Kingdom
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  • Fred Sablitzky,

    Corresponding author
    1. Institute of Genetics, School of Biology, Queen's Medical Centre, The University of Nottingham, Nottingham, United Kingdom
    • Institute of Genetics, School of Biology, Queen's Medical Centre, The University of Nottingham, Nottingham, NG7 2UH, UK
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  • Patrizia Casaccia-Bonnefil

    Corresponding author
    1. Department of Neuroscience and Cell Biology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey
    • Department of Neuroscience and Cell Biology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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Abstract

Myelination in the central nervous system is a complex process requiring the integration of oligodendrocyte progenitor differentiation and the coordinate expression of myelin genes. This study addresses the role of the helix-loop-helix protein Id4 in these two events. Overexpression of Id4 in oligodendrocyte progenitors prevents differentiation and consequently decreases the endogenous expression of all myelin genes. Conversely, progenitors lacking Id4 display precocious differentiation both in vitro and in vivo, and this phenotype is partially compensated by increased apoptosis. Besides this role, Id4 also has the ability to decrease the activity of specific myelin promoters, since Id4 overexpression decreases the activity of luciferase reporter genes driven by the ceramide galactosyltransferase (CGT) or myelin basic protein (MBP) promoter, but not by a myelin proteolipid protein (PLP) promoter. Consistent with these results, the expression levels of MBP and CGT are greater in neonatal Id4 null mice when compared with wild-type siblings and correlate with the early detection of MBP immunoreactive myelinated fibers. In contrast, the levels of other myelin proteins, such as PLP and myelin associated glycoprotein (MAG) are decreased in the Id4 null mice. MAG expression is localized to the soma rather than the fibers of immunoreactive cells in the neonatal brain and compensated at later developmental stages. These data support the role of Id4 as oligodendrocyte differentiation inhibitor with the ability to differentially regulate the expression and subcellular distribution of myelin gene products. © 2006 Wiley-Liss, Inc.

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