Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE.
Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY.
J Hered. 2020 Apr 2;111(2):182-193. doi: 10.1093/jhered/esz070.
Small numbers of domestic yak (Bos grunniens) were imported to North America in the late 19th century indirectly from the Qinghai-Tibetan Plateau. Coat color of yak is of interest for fiber production, aesthetics, and as a potential indicator of recent hybridization with cattle. North American yak are classified into 3 major coat color patterns depending upon the presence and extent of white markings. They are further classified by nose pigmentation (black or gray). The aim of this study was to identify loci involved in white patterning and nose pigmentation of North American yak. Genotyping by mass spectrometry of markers identified through Sanger and whole-genome sequencing revealed a 388 kb haplotype of KIT associated in a semi-dominant manner with white coloration in this population of yak. This KIT haplotype is similar to both a haplotype found in white-faced Chinese yak and to haplotypes found in cattle but is divergent from other Bos species such as bison, gaur, and banteng. Melanocortin 1 receptor (MC1R) was implicated as a dominant determinant of black nose color with a single haplotype containing 2 missense mutations perfectly associated with the phenotype. The MC1R haplotype associated with black nose pigment is also similar to cattle haplotypes. No cattle studied, however, shared either of the 2 haplotypes associated with color in yak, suggesting these alleles were introgressed into yak before they were imported to North America. These results provide molecular insight into the history of North American yak and information from which breeders can determine possible color outcomes of matings.
少量的家养牦牛（Bos grunniens）于 19 世纪末从青藏高原间接引入北美。牦牛的毛色对于纤维生产、美观以及作为与牛最近杂交的潜在指标很重要。北美牦牛根据白色标记的存在和程度分为 3 种主要毛色模式。它们进一步根据鼻色素（黑色或灰色）进行分类。本研究旨在鉴定与北美牦牛白色图案和鼻色素相关的基因座。通过桑格测序和全基因组测序鉴定的标记的质谱基因分型显示，KIT 存在一个 388 kb 的单倍型，与该牦牛群体中的白色着色呈半显性相关。该 KIT 单倍型与白面中国牦牛的单倍型以及牛的单倍型相似，但与其他牛科物种（如野牛、白肢野牛和野水牛）不同。黑素皮质素 1 受体（MC1R）被认为是黑色鼻色的显性决定因素，一个包含 2 个错义突变的单倍型与表型完全相关。与黑色鼻色素相关的 MC1R 单倍型也与牛的单倍型相似。然而，没有一头研究过的牛与牦牛毛色相关的 2 个单倍型中的任何一个共享，这表明这些等位基因在被引入北美之前就已经进入了牦牛。这些结果为北美牦牛的历史提供了分子见解，并为饲养员提供了确定交配可能产生的颜色结果的信息。
