DIPROVAL, Sezione di Allevamenti Zootecnici, Faculty of Agriculture, University of Bologna, Via F.lli Rosselli 107, 42123 Reggio Emilia, Italy.
Anim Genet. 2010 Jun;41(3):295-303. doi: 10.1111/j.1365-2052.2009.02007.x. Epub 2009 Nov 26.
According to classical genetic studies, piebaldism in cattle is largely influenced by the allelic series at the spotting locus (S), which includes the S(H) (Hereford pattern), S(+) (non-spotted) and s (spotted) alleles. The S locus was mapped on bovine chromosome 6 in the region containing the KIT gene. We investigated the KIT gene, analysing its variability and haplotype distribution in cattle of three breeds (Angus, Hereford and Holstein) with different putative alleles (S(+), S(H) and s respectively) at the S locus. Resequencing of a whole of 0.485 Mb revealed 111 polymorphisms. The global nucleotide diversity was 0.087%. Tajima's D-values were negative for all breeds, indicating putative directional selection. Of the 28 inferred haplotypes, only five were observed in the Hereford breed, in which one was the most frequent. Coalescent simulation showed that it is highly unlikely (P < 10E-6) to obtain this low number of haplotypes conditionally on the observed number of segregating SNPs. Therefore, the neutral model could be rejected for the Hereford breed, suggesting that a selection sweep occurred at the KIT locus. Twelve haplotypes were inferred in Holstein and Angus. For these two breeds, the neutral model could not be rejected. High heterogeneity of the KIT gene was confirmed from a phylogenetic analysis. Our results suggest a role of the KIT gene in determining the S(H) allele(s) in the Hereford, but no evidence of selective sweep was obtained in Holstein, suggesting that complex mechanisms (or other genes) might be the cause of the spotted phenotype in this breed.
根据经典遗传学研究，牛的斑驳病主要受斑点（S）基因座等位基因系列的影响，该系列包括 S(H)（海弗德图案）、S(+)（无斑点）和 s（斑点）等位基因。S 基因座定位于牛 6 号染色体，包含 KIT 基因。我们研究了 KIT 基因，分析了其在三个不同 S 基因座假定等位基因（S(+)、S(H)和 s）的牛品种（安格斯牛、海弗德牛和荷斯坦牛）中的变异性和单倍型分布。对整个 0.485 Mb 的重测序揭示了 111 个多态性。所有品种的核苷酸多样性均为 0.087%。Tajima 的 D 值均为负值，表明存在潜在的定向选择。在推断的 28 个单倍型中，仅在海弗德牛中观察到 5 个单倍型，其中一个最为常见。合并模拟表明，根据观察到的分离 SNP 数量，获得如此少的单倍型的可能性非常小（P < 10E-6）。因此，海弗德牛的中性模型可以被拒绝，表明 KIT 基因座发生了选择清扫。在荷斯坦牛和安格斯牛中推断出 12 个单倍型。对于这两个品种，中性模型不能被拒绝。系统发育分析证实 KIT 基因高度异质。我们的结果表明 KIT 基因在决定海弗德牛的 S(H)等位基因方面发挥了作用，但在荷斯坦牛中未获得选择清扫的证据，这表明复杂的机制（或其他基因）可能是导致该品种出现斑点表型的原因。
