Could be involved in the transport of tyrosine, the precursor to melanin synthesis, within the melanocyte. Regulates the pH of melanosome and the melanosome maturation. One of the components of the mammalian pigmentary system. Seems to regulate the post-translational processing of tyrosinase, which catalyzes the limiting reaction in melanin synthesis. May serve as a key control point at which ethnic skin color variation is determined. Major determinant of brown and/or blue eye color. Expression is under the control of an enhancer element that is encoded in an intron of the close-by HERC2 gene. The enhancer element containing the T-allele of the polymorphism rs12913832 mediates binding of the transcription factors HLTF, LEF1 and MITF and increases OCA2 expression. In contrast, transcription factor binding and OCA2 expression are reduced in carriers of the C-allele of polymorphism rs12913832. Thus, people homozygous for the C-allele have light-colored eyes, while people homozygous for the T-allele of polymorphism rs12913832 most often have brown eyes. Genetic variants in OCA2 define the skin/hair/eye pigmentation variation locus 1 (SHEP1) [MIM:227220]; also known as skin/hair/eye pigmentation type 1, blue/nonblue eyes or skin/hair/eye pigmentation type 1, blue/brown eyes or skin/hair/eye pigmentation type 1, blond/brown hair or eye color, brown/blue or eye color, blue/nonblue or eye color type 3 (EYCL3) or brown eye color type 2 (BEY2) or hair color type 3 (HCL3). Hair, eye and skin pigmentation are among the most visible examples of human phenotypic variation, with a broad normal range that is subject to substantial geographic stratification. In the case of skin, individuals tend to have lighter pigmentation with increasing distance from the equator. By contrast, the majority of variation in human eye and hair color is found among individuals of European ancestry, with most other human populations fixed for brown eyes and black hair. OCA2 polymorphisms may act as a penetrance modifier of the risk of malignant melanoma. The disease is caused by variants affecting the gene represented in this entry. Belongs to the CitM (TC 2.A.11) transporter family. Retina International's Scientific Newsletter P mutations Questioning colour - Issue 54 of January 2005