GNAQ gene
The GNAQ gene provides instructions for a protein subunit that regulates blood vessel development, and its mutation is linked to vascular disorders and certain eye cancers.
Normal Function
The GNAQ gene provides instructions for making the guanine nucleotide-binding protein G(q) subunit alpha (Gαq). This protein is part of a trimeric G protein complex that binds to G protein-coupled receptors. When activated by binding to a molecule called GTP, the Gαq protein separates from the complex to trigger signaling pathways that regulate blood vessel development and function. It is inactivated when it converts GTP to GDP.
Health Conditions Related to Genetic Changes
Sturge-Weber syndrome
A specific somatic mutation in the GNAQ gene (Arg183Gln or R183Q) causes Sturge-Weber syndrome. This mutation prevents the Gαq protein from converting GTP to GDP, leaving the protein in a permanently active state. This constant signaling disrupts blood vessel development, leading to:
- A red or pink port-wine birthmark
- Brain abnormalities
- Increased pressure in the eye (glaucoma)
Other disorders
The R183Q mutation can also cause isolated port-wine birthmarks without the associated brain or eye abnormalities. Additionally, somatic mutations in the GNAQ gene are found in uveal melanoma, a cancer of the middle layer of the eye. In these cases, the overactive protein leads to excessive signaling that contributes to the overgrowth of cells and tumor formation.