ABCA4

ABCA4 (ATP-binding cassette, sub-family A (ABC1), member 4) is a gene that in humans is encoded by the ABCA4 gene. The protein encoded by this gene is a member of the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intra-cellular membranes. ABC genes are divided into seven distinct subfamilies (ABC1, MDR/TAP, MRP, ALD, OABP, GCN20, and White). This protein is a member of the ABC1 subfamily. Members of the ABC1 subfamily comprise the only major ABC subfamily found exclusively in multicellular eukaryotes. This protein is a retina-specific ABC transporter with N-retinylidene-PE as a substrate. It is expressed exclusively in retina photoreceptor cells, indicating the gene product mediates the transport of an essential molecule across the photoreceptor cell membrane. Mutations in this gene are found in patients with Stargardt disease, a form of juvenile or early onset macular degeneration. Mutations in this gene are also associated with retinitis pigmentosa-19, cone-rod dystrophy type 3, early-onset severe retinal dystrophy, fundus flavimaculatus, and macular degeneration age-related 2.

Function

The ABCA4 gene provides instructions for making a protein that is found in the retina, the specialized tissue at the back of the eye that detects light and color. This protein is embedded in the membrane of specialized light receptor cells called photoreceptors. Within these cells, the ABCA4 protein is involved in the transport of molecules called retinoids, which are forms of vitamin A. Retinoids are necessary for the conversion of light into electrical signals that are sent to the brain, where they are interpreted as vision.

Clinical significance

Mutations in the ABCA4 gene have been associated with several related retinal disorders, including Stargardt disease, cone-rod dystrophy, and a form of retinitis pigmentosa. These conditions are characterized by vision loss that worsens over time. The vision loss is caused by the death of photoreceptor cells in the retina. Mutations in the ABCA4 gene disrupt the function of the ABCA4 protein, impairing the transport of retinoids in photoreceptor cells. This disruption leads to a toxic buildup of retinoids, which can damage photoreceptor cells and lead to vision loss.

See also

• ATP-binding cassette transporter
• Stargardt disease
• Cone-rod dystrophy
• Retinitis pigmentosa

References

ABCA4 Resources
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