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The official name of this gene is “oculocutaneous albinism II.”
OCA2 is the gene's official symbol. The OCA2 gene is also known by other names, listed below.
The OCA2 gene (formerly called the P gene) provides instructions for making a protein called the P protein. This protein is located in melanocytes, which are specialized cells that produce a pigment called melanin. Melanin is the substance that gives skin, hair, and eyes their color. Melanin is also found in the light-sensitive tissue at the back of the eye (the retina), where it plays a role in normal vision.
Although the exact function of the P protein is unknown, it is essential for normal pigmentation and is likely involved in the production of melanin. Within melanocytes, the P protein may transport molecules into and out of structures called melanosomes (where melanin is produced). Researchers believe that this protein may also help regulate the relative acidity (pH) of melanosomes. Tight control of pH is necessary for most biological processes.
More than 80 mutations in the OCA2 gene have been identified in people with oculocutaneous albinism type 2. People with this form of albinism often have light yellow, blond, or light brown hair; creamy white skin; light-colored eyes; and problems with vision. The most common OCA2 mutation is a large deletion in the gene, which is found in many affected individuals of sub-Saharan African heritage. Other OCA2 gene mutations, including changes in single DNA building blocks (base pairs) and small deletions, are more common in other populations. Mutations in the OCA2 gene disrupt the normal production of melanin, which reduces coloring of the hair, skin, and eyes and affects vision.
The OCA2 gene is located in a region of chromosome 15 that is often deleted in individuals with Angelman syndrome. A loss of this gene does not cause the characteristic neurologic features of Angelman syndrome; however, people with this condition who are missing one copy of the OCA2 gene tend to have unusually light-colored hair and fair skin. Cells with only one copy of the OCA2 gene make a reduced amount of P protein compared with cells with two functional copies of this gene, which affects the coloring of the hair and skin.
A small percentage of people with Angelman syndrome also have oculocutaneous albinism type 2. This condition occurs when people have two nonfunctional copies of the OCA2 gene in each cell. In addition to a deletion in chromosome 15 that removes one copy of the OCA2 gene, these individuals have a mutation in the OCA2 gene on the other copy of chromosome 15. As a result, cells make little or no functional P protein. A lack of P protein disrupts the production of melanin, leading to the characteristic features of albinism.
The region of chromosome 15 containing the OCA2 gene is often deleted in individuals with Prader-Willi syndrome. A loss of this gene does not cause intellectual disability and the other characteristic features of Prader-Willi syndrome; however, people with this condition who are missing one copy of the OCA2 gene tend to have unusually light-colored hair and fair skin. Cells missing a copy of the OCA2 gene make less P protein than cells with two functional copies of the gene, which affects the coloring of the hair and skin.
Oculocutaneous albinism type 2 also occurs in a small number of people with Prader-Willi syndrome. This condition occurs when people have two nonfunctional copies of the OCA2 gene in each cell. In addition to a deletion in chromosome 15 that removes one copy of the OCA2 gene, these individuals have a mutation in the OCA2 gene on the other copy of chromosome 15. As a result, cells make little or no functional P protein. A lack of P protein disrupts the production of melanin, leading to the characteristic features of albinism.
Cytogenetic Location: 15q
Molecular Location on chromosome 15: base pairs 27,754,872 to 28,099,339
The OCA2 gene is located on the long (q) arm of chromosome 15.
More precisely, the OCA2 gene is located from base pair 27,754,872 to base pair 28,099,339 on chromosome 15.
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 OCA2 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.
acidity ; albinism ; cell ; chromosome ; deletion ; disability ; DNA ; gene ; melanin ; melanocytes ; mutation ; neurologic ; pH ; pigment ; pigmentation ; protein ; retina ; syndrome ; tissue
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (/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.