Oligophrenin 1 (OPHN1)

Oligophrenin 1 has 25 exons and encodes a Rho-GTPase-activating protein. The Rho proteins are important mediators of intracellular signal transduction, which affects cell migration and cell morphogenesis. Mutations in this gene are responsible for non-specific X-linked mental retardation. The protein contains a domain typical of RhoGAPs, which modulate cytoskeletal changes. Northern blot analysis demonstrated greatest abundance of the 7.5-kb oligophrenin-1 transcript in RNA from human fetal brain. Fluorescence in situ hybridization indicated that the X;12 translocation breakpoint identified in the patient mapped within the second intron of the OPHN1 gene, resulting in a displacement on the derivative 12 of the first 2 exons, 1 of which contained a putative translation initiation codon.