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The official name of this gene is “ATP-binding cassette, sub-family A (ABC1), member 4.”
ABCA4 is the gene's official symbol. The ABCA4 gene is also known by other names, listed below.
The ABCA4 gene provides instructions for making a protein that is found in the retina, the specialized light-sensitive tissue that lines the back of the eye. Specifically, the ABCA4 protein is produced in the retina's specialized light receptor cells (photoreceptors). The ABCA4 protein is active following phototransduction, the process by which light entering the eye is converted into electrical signals that are transmitted to the brain. Phototransduction leads to the formation of potentially toxic substances. The ABCA4 protein removes one of these substances, called N-retinylidene-PE, from photoreceptor cells.
The ABCA4 gene belongs to a family of genes called ABC (ATP-binding cassette transporters).
A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genefamilies) in the Handbook.
More than 500 mutations in the ABCA4 gene have been found to cause Stargardt macular degeneration. Most of these mutations change single protein building blocks (amino acids) in the ABCA4 protein. A malfunctioning ABCA4 protein cannot remove N-retinylidene-PE from photoreceptor cells. As a result, N-retinylidene-PE combines with another substance to produce a fatty yellow pigment called lipofuscin, which builds up in retinal cells. The buildup of lipofuscin is toxic to the cells of the retina and causes progressive vision loss in people with Stargardt macular degeneration. In most cases, Stargardt macular degeneration is caused by mutations in the ABCA4 gene.
Mutations in the ABCA4 gene have also been found to cause a vision disorder called cone-rod dystrophy. The vision problems associated with this condition include a loss of sharpness (reduced acuity), an increased sensitivity to light (photophobia), nearsightedness (myopia), and impaired color vision. These vision problems tend to worsen over time. Most of the ABCA4 gene mutations that cause cone-rod dystrophy change single amino acids in the ABCA4 protein. It is estimated that ABCA4 gene mutations account for 30 to 60 percent of cases of cone-rod dystrophy.
Some studies have suggested that ABCA4 gene mutations are associated with an increased risk for developing age-related macular degeneration. This eye disease is a leading cause of vision loss among older people worldwide. It is characterized by damage to the retina and a loss of visual acuity. While some studies have found an association between ABCA4 gene mutations and age-related macular degeneration, other studies have not found this association. A combination of genetic and environmental factors likely determines the risk of developing this disease.
Cytogenetic Location: 1p22
Molecular Location on chromosome 1: base pairs 93,992,836 to 94,121,148
The ABCA4 gene is located on the short (p) arm of chromosome 1 at position 22.
More precisely, the ABCA4 gene is located from base pair 93,992,836 to base pair 94,121,148 on chromosome 1.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
You and your healthcare professional may find the following resources about ABCA4 helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
acids ; ATP ; gene ; lipofuscin ; myopia ; nearsightedness ; photophobia ; photoreceptor ; pigment ; protein ; receptor ; retina ; sensitivity ; tissue ; toxic ; visual acuity
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://ghr.nlm.nih.gov/glossary).
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.