Zhang M-Q, Xu X, Luo S-J
College of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China.
Anim Genet. 2014 Oct;45(5):652-9. doi: 10.1111/age.12191. Epub 2014 Jul 3.
Domestic yaks (Bos grunniens) exhibit two major coat color variations: a brown vs. wild-type black pigmentation and a white spotting vs. wild-type solid color pattern. The genetic basis for these variations in color and distribution remains largely unknown and may be complicated by a breeding history involving hybridization between yaks and cattle. Here, we investigated 92 domestic yaks from China using a candidate gene approach. Sequence variations in MC1R, PMEL and TYRP1 were surveyed in brown yaks; TYRP1 was unassociated with the coloration and excluded. Recessive mutations from MC1R, or p.Gln34*, p.Met73Leu and possibly p.Arg142Pro, are reported in bovids for the first time and accounted for approximately 40% of the brown yaks in this study. The remaining 60% of brown individuals correlated with a cattle-derived deletion mutation from PMEL (p.Leu18del) in a dominant manner. Degrees of white spotting found in yaks vary from color sidedness and white face, to completely white. After examining the candidate gene KIT, we suggest that color-sided and all-white yaks are caused by the serial translations of KIT (Cs6 or Cs29 ) as reported for cattle. The white-faced phenotype in yaks is associated with the KIT haplotype S(wf) . All KIT mutations underlying the serial phenotypes of white spotting in yaks are identical to those in cattle, indicating that cattle are the likely source of white spotting in yaks. Our results reveal the complex genetic origins of domestic yak coat color as either native in yaks through evolution and domestication or as introduced from cattle through interspecific hybridization.
家养牦牛（Bos grunniens）表现出两种主要的毛色变异：棕色与野生型黑色色素沉着，以及白色斑点与野生型纯色图案。这些毛色及其分布变异的遗传基础在很大程度上仍然未知，并且可能因牦牛与牛之间杂交的繁殖历史而变得复杂。在这里，我们采用候选基因方法对来自中国的92头家养牦牛进行了研究。在棕色牦牛中检测了MC1R、PMEL和TYRP1的序列变异；TYRP1与毛色无关，被排除在外。首次在牛科动物中报道了MC1R的隐性突变，即p.Gln34*、p.Met73Leu以及可能的p.Arg142Pro，在本研究中约占棕色牦牛的40%。其余60%的棕色个体与PMEL基因中源自牛的缺失突变（p.Leu18del）呈显性相关。牦牛身上发现的白色斑点程度各不相同，从毛色偏白和白脸到完全白色。在检测了候选基因KIT后，我们认为毛色偏白和全白的牦牛是由KIT（Cs6或Cs29）的串联重复导致的，这与牛的情况一致。牦牛的白脸表型与KIT单倍型S(wf)相关。牦牛白色斑点串联表型的所有KIT突变都与牛的相同，这表明牛可能是牦牛白色斑点的来源。我们的结果揭示了家养牦牛毛色复杂的遗传起源，要么是通过进化和驯化在牦牛中自然形成的，要么是通过种间杂交从牛引入的。
