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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The rat Schwannoma cell line D6P2T constitutively expresses the mRNA encoding the major myelin protein, P0, but only expresses the mRNA encoding myelin basic protein (MBP) after exposure to forskolin or other substances that raise the levels of intracellular cyclic AMP. In this study we have investigated the molecular basis for forskolin induction of MBP transcription in D6P2T cells. We have found that a 9-bp sequence element, CACTTGATC, located between nucleotides −85 and −77 in the MBP promoter, is necessary for forskolin induction of chloramphenicol acetyltransferase (CAT) expression after transient transfection of MBP promoter-CAT fusion constructs into D6P2T cells. Although similar DNase I footprints, one of which is located within the above 9-bp sequence element, are produced by nuclear extracts prepared from both forskolin-treated and untreated cells, this same sequence can be shown to interact with a forskolin-inducible protein complex using an electrophoretic mobility shift assay. In addition, mutation of this 9-bp sequence abolishes both formation of this new protein-DNA complex and forskolin-inducible CAT expression from the heterologous SV40 promoter. Finally, we have shown that the appearance of this forskolin-inducible protein-DNA complex precedes that of MBP mRNA. Taken together, these data strongly support the notion that the induction of MBP transcription by forskolin in D6P2T cells is mediated by the binding of a forskolin-inducible protein complex to the MBP promoter sequence CACTTGATC.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 91 (2004), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Oligodendrocytes and Schwann cells use diverse regulatory elements to transcribe myelin basic protein (Mbp). For example, an enhancer 9.0 kb upstream of Mbp (MbpSCE1) activated either the proximal Mbp or hsp68 promoters only in Schwann cells in transgenic mice. Here, we analyze MbpSCE1 in vitro and in vivo and show that MbpSCE1 also activates another myelin gene, Mpz, specifically in Schwann cells in transgenic mice. Surprisingly, although MbpSCE1 behaves as an enhancer in Schwann cells, we show here for the first time that it also activates transcription robustly in cultured oligodendrocytes, but only from its original genomic position. Diverse nuclear proteins binding at distinct combinations of DNA elements in the two cell types may account for cell-specific MbpSCE1 function. A further surprise is that MbpSCE1 activation does not depend on consensus binding sites for the myelin-associated PPARβ or Krox 20 transcription factors. Finally, chromatin context augments activation of MbpSCE1. Therefore, MbpSCE1 is active in both Schwann cells and oligodendrocytes, but by diverse mechanisms.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Myelination of peripheral nerves by Schwann cells requires a large amount of lipid and cholesterol biosynthesis. To understand the transcriptional coordination of the myelination process, we have investigated the developmental relationship between early growth response 2 (Egr2)/Krox20 – a pivotal regulator of peripheral nerve myelination – and the sterol regulatory element binding protein (SREBP) pathway, which controls expression of cholesterol/lipid biosynthetic genes. During myelination of sciatic nerve, there is a very significant induction of SREBP1 and SREBP2, as well as their target genes, suggesting that the SREBP transactivators are important regulators in the myelination process. Egr2/Krox20 does not appear to directly regulate the levels of SREBP pathway components, but rather, we found that Egr2/Krox20 and SREBP transactivators can synergistically activate promoters of several SREBP target genes, indicating that direct induction of cholesterol/lipid biosynthetic genes by Egr2/Krox20 is a part of the myelination program regulated by this transactivator.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: P0 glycoprotein, the most abundant protein in peripheral nerve, is expressed specifically in the Schwann cell lineage. Upstream of the rat P0 gene 1.1 kb of DNA can activate expression of cDNAs specifically in Schwann cells in transgenic mice. However, the expression of P0 promoter-based transgenes has been inconsistent. As much as 9 kb of 5′ flanking sequence fused to lacZ never yielded detectable levels of β-galactosidase in multiple lines of mice. We describe transgenic mice that express lacZ in peripheral nerve, using the complete mouse P0 gene, including 6 kb of 5′ flanking sequence, all exons and introns, and the natural polyadenylation signal. This vector activated lacZ expression specifically in cultured Schwann cells, and myelin-forming Schwann cells in four out of six transgenic lines. Transgene expression paralleled that of the endogenous P0 gene, both during development and after Wallerian degeneration. lacZ expression was lower than endogenous P0 expression, and was not detected in neural crest or Schwann cell precursors, where low levels of P0 mRNA are present. However, when the same vector contained a small myc tag instead of the 3.2-kb lacZ insert, the resulting transgenic mRNA was expressed at levels comparable to endogenous P0 mRNA. These data suggest that intragenic or 3′ flanking sequences are necessary to generate the remarkable levels of endogenous P0 gene expression.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0533
    Keywords: Key words Interferon-α ; Neuropathy ; Hepatitis C ; HLA-DR antigens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A 44-year-old man developed a peripheral neuropathy during treatment with interferon-α for chronic hepatitis C. The onset was insidious, beginning symmetrically in the hands with paresthesia. Neurophysiological investigation revealed a predominantly sensory axonal neuropathy. A sural nerve biopsy confirmed primary axonal damage. Immunofluorescence studies showed increased expression of HLA-DR molecules prevalently on Schwann cells of non-myelin-forming type.
    Type of Medium: Electronic Resource
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