Saturday, February 17, 2007

One variant of TYRP1 controls all coat color variation in sheep

According to this paper, a variant in TYRP1 controls most, if not all the variation in coat color in Soay sheep...this is pretty cool because this gene is one of the handful that is known to influence skin color in humans (albinism) and several animals, and has been shown to be under positive selection (Voight PloS paper and recent AHG Lao paper, via Dienenkes) in humans.
...also see this post and Razib's corresponding post. The color of these sheep (see pictures) remind me of human skin color variation.

Compelling evidence that a single nucleotide substitution in TYRP1 is responsible for coat-colour polymorphism in a free-living population of Soay sheep

J. Gratten, D. Beraldi, B.V. Lowder, A.F. McRae, P.M. Visscher, J.M. Pemberton, J. Slate

Proceedings of the Royal Society B: Biological Sciences Volume 274, Number 1610 / March 07, 2007 Pages: 619 - 626

Abstract: Identifying the genes that underlie phenotypic variation in natural populations is a central objective of evolutionary genetics. Here, we report the identification of the gene and causal mutation underlying coat colour variation in a free-living population of Soay sheep (Ovis aries). We targeted tyrosinase-related protein 1 (TYRP1), a positional candidate gene based on previous work that mapped the Coat colour locus to an approximately 15cM window on chromosome 2. We identified a non-synonymous substitution in exon IV that was perfectly associated with coat colour. This polymorphism is predicted to cause the loss of a cysteine residue that is highly evolutionarily conserved and likely to be of functional significance. We eliminated the possibility that this association is due to the presence of strong linkage disequilibrium with an unknown regulatory mutation by demonstrating that there is no difference in relative TYRP1 expression between colour morphs. Analysis of this putative causal mutation in a complex pedigree of more than 500 sheep revealed almost perfect co-segregation with coat colour (χ2-test, p<0.0001, lod="110.20)," lod="29.50).

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