P Protein

The P protein is believed to be an integral membrane protein involved in small molecule transport, specifically of tyrosine—a precursor of melanin. Certain mutations in OCA2 result in type 2 oculocutaneous albinism. OCA2 encodes the human homologue of the mouse p (pink-eyed dilution) gene.

OCA2
Identifiers
Aliases	OCA2, BEY, BEY1, BEY2, BOCA, D15S12, EYCL, EYCL2, EYCL3, HCL3, PED, SHEP1, OCA2 melanosomal transmembrane protein, P
External IDs	OMIM: 611409 MGI: 97454 HomoloGene: 37281 GeneCards: OCA2
Gene location (Human) Chr. Chromosome 15 (human) Band 15q12-q13.1 Start 27,754,875 bp End 28,099,315 bp
Gene location (Mouse) Chr. Chromosome 7 (mouse) Band 7 B5|7 33.44 cM Start 55,889,508 bp End 56,186,266 bp
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in retinal pigment epithelium secondary oocyte hair follicle sperm vulva human penis epithelium of esophagus nipple popliteal artery superior vestibular nucleus Top expressed in iris retinal pigment epithelium ciliary body hair follicle barrel cortex corneal stroma adrenal gland lateral ventricle visual cortex right ventricle More reference expression data BioGPS More reference expression data
Gene ontology Molecular function transporter activity L-tyrosine transmembrane transporter activity protein binding Cellular component endoplasmic reticulum membrane lysosomal membrane endosome membrane membrane cytoplasm melanosome membrane integral component of membrane Biological process eye pigment biosynthetic process pigmentation developmental pigmentation melanin biosynthetic process cell population proliferation transmembrane transport spermatid development melanocyte differentiation tyrosine transport Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 4948 18431 Ensembl ENSG00000104044 ENSG00000277361 ENSMUSG00000030450 UniProt Q04671 Q62052 RefSeq (mRNA) NM_000275 NM_001300984 NM_021879 RefSeq (protein) NP_000266 NP_001287913 NP_068679 Location (UCSC) Chr 15: 27.75 – 28.1 Mb Chr 7: 55.89 – 56.19 Mb PubMed search
Wikidata
View/Edit Human View/Edit Mouse

The human OCA2 gene is located on the long arm (q) of chromosome 15, specifically from base pair 28,000,020 to base pair 28,344,457 on chromosome 15.

OCA2 provides instructions for making the protein called P protein which is located in melanocytes which are specialized cells that produce melanin, and in the cells of the retinal pigment epithelium. Melanin is responsible for giving color to the skin, hair, and eyes. Moreover, melanin is found in the light-sensitive tissue of the retina of the eye which plays a role in normal vision.

The exact function of protein P is unknown, but it has been found that it is essential for the normal coloring of skin, eyes, and hair; and likely involved in melanin production. This gene seems to be the main determinant of eye color depending on the amount of melanin production in the iris stroma (large amounts giving rise to brown eyes; little to no melanin giving rise to blue eyes).

This gene is mutated in Astyanax mexicanus, a Mexican fish which is characterized by a chronic Albinism in cave's individuals. It exists as a deletion in Pachón and Molino's caves fish that produces the albinism.

Mutations in the OCA2 gene cause a disruption in the normal production of melanin; therefore, causing vision problems and reductions in hair, skin, and eye color. Oculocutaneous albinism caused by mutations in the OCA2 gene is called oculocutaneous albinism type 2. The prevalence of OCA type 2 is estimated at 1/38,000-1/40,000 in most populations throughout the world, with a higher prevalence in the African population of 1/3,900–1/1,500. Other diseases associated with the deletion of the OCA2 gene are Angelman syndrome (light-colored hair and fair skin) and Prader–Willi syndrome (unusually light-colored hair and fair skin). With both these syndromes, the deletion often occurs in individuals with either syndrome.

A mutation in the HERC2 gene adjacent to OCA2, affecting OCA2's expression in the human iris, is found common to nearly all people with blue eyes. It has been hypothesized that all blue-eyed humans share a single common ancestor with whom the mutation originated.

The His615Arg allele of OCA2 is involved in the light skin tone and the derived allele is restricted to East Asia with high frequencies, with highest frequencies in Eastern East Asia (49-63%), midrange frequencies in Southeast Asia, and the lowest frequencies in Western China and some Eastern European populations.

External links

 

Wiki Commons has media related to OCA2.

• GeneReviews/NCBI/NIH/UW entry on Oculocutaneous Albinism Type 2