NF-1 is a microdeletion syndrome caused by a mutation of a gene located on chromosomal segment 17q11. 2 on the long arm of chromosome 17 which encodes a protein known as neurofibromin (not to be confused with the disorder itself) which plays a role in cell signaling. The Neurofibromin 1 gene is a negative regulator of the Ras oncogene signal transduction pathway. It stimulates the GTPase activity of Ras. It shows greater affinity for RAS p21 protein activator 1, but lower specific activity. The mRNA for this gene is subject to RNA editing (CGA->UGA->Arg1306Term) resulting in premature translation termination. Alternatively spliced transcript variants encoding different isoforms have also been described for this gene.