Concept

Neurofibromine 1

Résumé
neurofibromatosis 1 (NF1) is a gene in humans that is located on chromosome 17. NF1 codes for neurofibromin, a GTPase-activating protein that negatively regulates RAS/MAPK pathway activity by accelerating the hydrolysis of Ras-bound GTP. NF1 has a high mutation rate and mutations in NF1 can alter cellular growth control, and neural development, resulting in neurofibromatosis type 1 (NF1, also known as von Recklinghausen syndrome). Symptoms of NF1 include disfiguring cutaneous neurofibromas (CNF), café au lait pigment spots, plexiform neurofibromas (PN), skeletal defects, optic nerve gliomas, life-threatening malignant peripheral nerve sheath tumors (MPNST), pheochromocytoma, attention deficits, learning deficits and other cognitive disabilities. NF1 was cloned in 1990 and its gene product neurofibromin was identified in 1992. Neurofibromin, a GTPase-activating protein, primarily regulates the protein Ras. NF1 is located on the long arm of chromosome 17, position q11.2 NF1 spans over 350-kb of genomic DNA and contains 62 exons. 58 of these exons are constitutive and 4 exhibit alternative splicing ( 9a, 10a-2, 23a, and 28a). The genomic sequence starts 4,951-bp upstream of the transcription start site and 5,334-bp upstream of the translation initiation codon, with the length of the 5' UTR being 484-bp long. There are three genes that are present within intron 27b of NF1. These genes are EVI2B, EVI2A and OMG, which are encoded on the opposite strand and are transcribed in the opposite direction of NF1. EVI2A and EVI2B are human homologs of the Evi-2A and Evi-2B genes in mice that encode proteins related to leukemia in mice. OMG is a membrane glycoprotein that is expressed in the human central nervous system during myelination of nerve cells. Early studies of the NF1 promoter found that there is great homology between the human and mouse NF1 promoters. The major transcription start site has been confirmed, as well as two minor transcription start sites in both the human and mouse gene.
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