The gene responsible for neurofibromatosis type 1 (NF1), a common autosomal dominantly inherited disease, has been isolated. A region of NF1 gene product has been demonstrated to share structural and functional similarities with the mammalian GTPase activating protein (GAP) and the yeast IRA proteins. Thus, the NF1 protein is thought to play a role in signal transduction by stimulating the conversion of the Ras protein from a GTP-bound active form to a GDP-bound inactive form. The increased risk of malignant tumors in neuroectodermal tissues of NF1 patients may be caused by disruption of growth and differentiation regulatory functions of the NF1 gene. A second type of the NF1-GAP related domain (NF1-GRD) transcript, which has an extra 21-amino-acid insert in the center of the previously reported first type transcript, has been described. This insert significantly changes the hydrophilicity and secondary structure of the central region of NF1-GRD, therefore, suggesting it also changes its function. Alternative splicing is the most likely mechanism by which these two types of transcripts arise. The NF1-GRD alternative splicing has been shown to be intimately involved in differentiation of neuroectodermal tissues. Aberrant regulation of the alternative splicing may contribute to tumor formation in neuroectodermal tissue.
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