A network of genes is recruited in developing oligodendrocytes to coordinate the production of myelin, a deficiency of which can drastically impair neuronal function in the central nervous system. Mechanisms operative in regulating myelin gene expression can be revealed by defining the set of transcription factors that are selectively and temporally activated in developing oligodendrocytes and by establishing the function of key transcription factors. Our progress in deciphering the transcriptional controls exerted on developing oligodendrocytes covers five areas. First, we characterized individual transcription factors expressed in oligodendrocytes (Myt1, MYT2, YY1, PPAR and rKr2), four of which we discovered based on their specific binding to the myelin PLP promoter. Oligodendrocytes initiate their myelin program several developmental stages prior to myelin synthesis, and Myt1 and MYT2 are each structurally novel DNA-binding proteins present during the progenitor stage when their target gene (PLP) first becomes transcriptionally active. Second, we carried out the first molecular examination of nuclear structure in oligodendrocytes, in which we documented the spatial organization of myelin transcription factors, splicing factors and myelin genes. Third, we defined an interaction between the Myt1 transcription factor and a transcriptional co-repressor, Sin3, that may locally modify chromatin structure to regulate myelin gene transcription. Fourth, we established several in vivo experimental paradigms for evaluating the regulation of transcription factors during development and following injury, including demyelinating lesions and a transgenic mouse featuring tagged oligodendrocytes that can be tracked during development and following transplantation. Lastly, we set up a reliable system to examine the changing pattern of transcription factors expressed by oligodendrocytes through microarray analysis. These studies form the basis for devising strategies to promote remyelination in diseases such as multiple sclerosis, Pelizaeus-Merzbacher disease and spinal cord injury, either by directly supplying normal progenitors or by stimulating endogenous oligodendrocyte progenitors to proliferate, migrate and differentiate.
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