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  • Title: Loss of NF1 results in activation of the Ras signaling pathway and leads to aberrant growth in haematopoietic cells.
    Author: Bollag G, Clapp DW, Shih S, Adler F, Zhang YY, Thompson P, Lange BJ, Freedman MH, McCormick F, Jacks T, Shannon K.
    Journal: Nat Genet; 1996 Feb; 12(2):144-8. PubMed ID: 8563751.
    Abstract:
    Individuals with neurofibromatosis type 1 (NF1) are predisposed to certain cancers including juvenile chronic myelogenous leukaemia (JCML). The NF1 tumour-suppressor gene encodes a protein (neurofibromin) that accelerates GTP hydrolysis on Ras proteins. Here we show that primary leukaemic cells from children with NF1 show a selective decrease in NF1-like GTPase activating protein (GAP) activity for Ras but retain normal cellular GAP activity. Leukaemic cells also show an elevated percentage of Ras in the GTP-bound conformation. JCML cells are hypersensitive to granulocyte-macrophage colony stimulating factor (GM-CSF), and we observed a similar pattern of aberrant growth in haematopoietic cells from Nf1-/- mouse embryos. These data define a specific role for neurofibromin in negatively regulating GM-CSF signaling through Ras in haematopoietic cells and they suggest that hypersensitivity to GM-CSF may be a primary event in the development of JCML.
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