World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0014756569
Reproduction Date:

Title: Oca2  
Author: World Heritage Encyclopedia
Language: English
Subject: Human skin color, HERC2, Allele, Albinism
Publisher: World Heritage Encyclopedia


Oculocutaneous albinism II
Symbols  ; BEY; BEY1; BEY2; BOCA; D15S12; EYCL; EYCL2; EYCL3; HCL3; P; PED; SHEP1
External IDs GeneCards:
RNA expression pattern
Species Human Mouse
RefSeq (mRNA)
RefSeq (protein)
Location (UCSC)
PubMed search

P protein, also known as melanocyte-specific transporter protein or pink-eyed dilution protein homolog, is a protein that in humans is encoded by the oculocutaneous albinism II (OCA2) gene.[1] The P protein is believed to be an integral membrane protein involved in small molecule transport, specifically tyrosine - a precursor of melanin. Certain mutations in OCA2 result in type 2 oculocutaneous albinism.[1] OCA2 encodes the human homologue of the mouse p (pink-eyed dilution) gene.

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.


Frequencies of the derived His615Arg (rs1800414) allele of OCA2 in Asia.

OCA2 provides instructions for making the protein called P protein which is located in melanocytes which are specialized cells that produce melanin. 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).

Clinical significance

Global frequency distribution of the OCA2 gene's ancestral allele (blue) and derived His615Arg allele (yellow).

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 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.[2]

Other diseases associated with the deletion of 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.[3][4]

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.[5][6][7]

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.[8][9]


  1. ^ a b "Entrez Gene: OCA2 oculocutaneous albinism II (pink-eye dilution homolog, mouse)". 
  2. ^ Hayashi, Masahiro; Suzuki, Tamio (2013-04). "Oculocutaneous albinism type 2".  
  3. ^ "OCA2 - oculocutaneous albinism II". Genetics Home Reference - Your guide to understanding genetic conditions. U.S. National Library of Medicine. Retrieved 30 March 2013. 
  4. ^ "Don't it make your brown eyes blue?". Understanding Genetics. Understanding Genetics. Retrieved 30 March 2013. 
  5. ^ Bryner J (2008-01-31). "Here's what made those brown eyes blue". Health News. MSNBC. Retrieved 2008-11-06. ; Bryner J (2008-01-31). "One Common Ancestor Behind Blue Eyes". LiveScience. Imaginova Corp. Retrieved 2008-11-06. ; "Blue-eyed humans have a single, common ancestor". News. University of Copenhagen. 2008-01-30. Retrieved 2008-11-06. 
  6. ^ Eiberg H, Troelsen J, Nielsen M, Mikkelsen A, Mengel-From J, Kjaer KW, Hansen L (March 2008). "Blue eye color in humans may be caused by a perfectly associated founder mutation in a regulatory element located within the HERC2 gene inhibiting OCA2 expression". Human Genetics 123 (2): 177–87.  
  7. ^ Sturm RA, Duffy DL, Zhao ZZ, Leite FP, Stark MS, Hayward NK, Martin NG, Montgomery GW (February 2008). "A Single SNP in an Evolutionary Conserved Region within Intron 86 of the HERC2 Gene Determines Human Blue-Brown Eye Color". American Journal of Human Genetics 82 (2): 424–31.  
  8. ^ Donnelly MP, Paschou P, Grigorenko E, Gurwitz D, Barta C, Lu RB, Zhukova OV, Kim JJ, Siniscalco M, New M, Li H, Kajuna SL, Manolopoulos VG, Speed WC, Pakstis AJ, Kidd JR, Kidd KK (May 2012). "A global view of the OCA2-HERC2 region and pigmentation". Hum. Genet. 131 (5): 683–96.  
  9. ^ Edwards M, Bigham A, Tan J, Li S, Gozdzik A, Ross K, Jin L, Parra EJ (March 2010). "Association of the OCA2 polymorphism His615Arg with melanin content in east Asian populations: further evidence of convergent evolution of skin pigmentation". PLoS Genet. 6 (3): e1000867.  

Further reading

External links

  • GeneReviews/NCBI/NIH/UW entry on Oculocutaneous Albinism Type 2
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from World Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.