Department of Animal Sciences, UF Genetics Institute, University of Florida, Gainesville, FL, 32611-0910, USA.
American Paint Horse Association, Fort Worth, TX, 76161-0023, USA.
Anim Genet. 2020 Oct;51(5):707-715. doi: 10.1111/age.12960. Epub 2020 Jul 20.
The American Paint Horse Association (APHA) records pedigree and performance information for their breed, a stock-type horse valued as a working farm or ranch horse and as a pleasure horse. As the name implies, the breed is also valued for its attractive white-spotting patterns on the coat. The APHA utilizes visual inspections of photographs to determine if coat spotting exceeds threshold anatomical landmarks considered characteristic of desirable patterns. Horses with sufficient white patterning enter the 'Regular' registry, rather than the 'Solid Paint-Bred' division, providing a threshold modeled phenotype. Genetic studies previously defined sequence variants corresponding to 35 alleles for white spotting in the horse. Here, we calculate the allele frequencies for nine common white-spotting alleles in the American Paint Horse using a sample of 1054 registered animals. The APHA spotting phenotype is altered by additive interactions among spotting loci, and epistatically by the MC1R and ASIP genes controlling pigment production. The W20 allele within the KIT gene, independent of other known spotting alleles, was strongly associated with the APHA-defined white-spotting phenotype (P = 1.86 × 10 ), refuting reports that W20 acts only as a modifier of other underlying white-spotting patterns. The parentage of an individual horse, either American Paint or American Quarter Horse, did not alter the likelihood of its entering the APHA Regular Registry. An empirical definition of the action of these genetic loci on the APHA-defined white-spotting phenotype will allow more accurate application of genome-assisted selection for improving color production and the marketability of APHA horses.
美国花马协会 (APHA) 记录了其品种的血统和性能信息，该品种是一种具有股票型特征的马，被视为工作农场或牧场的马和休闲马。顾名思义，该品种还因其在皮毛上具有吸引人的白色斑点图案而受到重视。APHA 利用对照片的视觉检查来确定皮毛斑点是否超过了被认为是理想图案特征的解剖学标志的阈值。具有足够白色图案的马进入“常规”登记册，而不是“纯色花马”分部，提供了一个阈值模型表型。之前的遗传研究定义了马的白色斑点的 35 个等位基因的序列变体。在这里，我们使用 1054 只注册动物的样本计算了美国花马中九个常见白色斑点等位基因的等位基因频率。APHA 的斑点表型是由斑点基因座之间的加性相互作用以及控制色素生成的 MC1R 和 ASIP 基因的上位性相互作用改变的。KIT 基因内的 W20 等位基因与其他已知的斑点等位基因无关，与 APHA 定义的白色斑点表型强烈相关（P = 1.86 × 10 -16 ），驳斥了 W20 仅作为其他潜在的白色斑点模式的修饰因子的报道。马的父母是美国花马还是美国夸特马并不改变其进入 APHA 常规登记册的可能性。这些遗传基因座对 APHA 定义的白色斑点表型的作用的经验定义将允许更准确地应用基因组辅助选择，以提高颜色生产和 APHA 马的市场价值。
