Institute for Animal Breeding and Genetics, University of Veterinary Medicine Hannover Foundation, Hannover, 30559, Germany.
Department of Pathology, University of Veterinary Medicine Hannover Foundation, Hannover, 30559, Germany.
Sci Rep. 2018 Apr 23;8(1):6374. doi: 10.1038/s41598-018-24865-3.
Curly coat represents an extraordinary type of coat in horses, particularly seen in American Bashkir Curly Horses and Missouri Foxtrotters. In some horses with curly coat, a hypotrichosis of variable extent was observed, making the phenotype appear more complex. In our study, we aimed at investigating the genetic background of curly coat with and without hypotrichosis using high density bead chip genotype and next generation sequencing data. Genome-wide association analysis detected significant signals (p = 1.412 × 10-1.102 × 10) on horse chromosome 11 at 22-35 Mb. In this significantly associated region, six missense variants were filtered out from whole-genome sequencing data of three curly coated horses of which two variants within KRT25 and SP6 could explain all hair phenotypes. Horses heterozygous or homozygous only for KRT25 variant showed curly coat and hypotrichosis, whereas horses with SP6 variant only, exhibited curly coat without hypotrichosis. Horses with mutant alleles in both variants developed curly hair and hypotrichosis. Thus, mutant KRT25 allele is masking SP6 allele effect, indicative for epistasis of KRT25 variant over SP6 variant. In summary, genetic variants in two different genes, KRT25 and SP6, are responsible for curly hair. All horses with KRT25 variant are additionally hypotrichotic due to the KRT25 epistatic effect on SP6.
卷毛是马的一种特殊被毛类型，尤其可见于美国阿肯色卷毛马和密苏里走马。在一些卷毛马中，观察到程度不同的少毛症，使表型看起来更加复杂。在我们的研究中，我们使用高密度珠芯片基因型和下一代测序数据，旨在研究有少毛症和无少毛症的卷毛被毛的遗传背景。全基因组关联分析在马 11 号染色体上 22-35Mb 处检测到显著信号（p=1.412×10-11 至 1.002×10-11）。在这个显著相关的区域，从三头卷毛马的全基因组测序数据中筛选出六个错义变异，其中两个变异位于 KRT25 和 SP6 内，可以解释所有的毛发表型。KRT25 变异杂合或纯合的马表现为卷毛和少毛症，而只有 SP6 变异的马表现为卷毛而无少毛症。两种变异均为突变等位基因的马表现为卷毛和少毛症。因此，KRT25 等位基因的突变掩盖了 SP6 等位基因的效应，表明 KRT25 变异对 SP6 变异存在上位性。总之，两个不同基因，KRT25 和 SP6，的遗传变异导致了卷毛。由于 KRT25 对 SP6 的上位性效应，所有具有 KRT25 变异的马都额外具有少毛症。
