Population Genomics Group, Department of Veterinary Sciences, Ludwig Maximillians University Munich, Munich, Germany.
Tierzuchtforschung e.V. Munich, Grub, Germany.
Anim Genet. 2024 Feb;55(1):123-133. doi: 10.1111/age.13387. Epub 2023 Dec 8.
Ear length in sheep (Ovis aries) shows a wide range of natural variation, from the absence of an outer ear structure (anotia), to small outer ears (microtia), to regular ear length. Up until now, the underlying genetics of this phenotype has been studied in four sheep breeds from China, Jordan and Italy. These studies revealed a broad range of genes significantly associated with ear length, potentially indicating genetic heterogeneity across breeds or geographic regions. In the current study, we performed genome-wide SNP genotyping and haplotype-based mapping, in a population of 340 individuals, to identify loci influencing ear length variation in additional sheep breeds from Slovenia, Croatia, Cyprus and Greece. Additionally, two previously described candidate variants were also genotyped in our mapping population. The mapping model without candidate variant genotypes revealed only one genome-wide significant signal, which was located next to HMX1 on OAR6. This region was previously described as being associated with ear length variation in the Altay and Awassi sheep breeds. The mapping model including the candidate duplication genotype near HMX1 as a fixed effect explained the phenotypic variance on OAR6 and revealed an additional genome-wide significant locus on OAR13 associated with ear length. Our results, combined with published evidence, suggest that a duplication in the evolutionarily conserved region near HMX1 is the major regulator of ear length in sheep breeds descended from a larger region from Central Asia, to the Middle East, Cyprus, Greece and to the Alps. This distribution suggests an ancient origin of the derived allele.
绵羊（Ovis aries）的耳朵长度存在广泛的自然变异，从没有外耳结构（无耳）到小的外耳（小耳）再到正常的耳朵长度。到目前为止，已经在中国、约旦和意大利的四个绵羊品种中研究了这种表型的潜在遗传基础。这些研究表明，与耳朵长度显著相关的基因范围很广，这可能表明不同品种或地理区域存在遗传异质性。在当前的研究中，我们对来自斯洛文尼亚、克罗地亚、塞浦路斯和希腊的 340 只个体进行了全基因组 SNP 基因分型和基于单倍型的映射，以确定影响耳朵长度变异的基因座。此外，我们还在映射群体中对两个先前描述的候选变体进行了基因分型。在没有候选变异基因型的映射模型中，只发现了一个全基因组显著信号，该信号位于 OAR6 上的 HMX1 附近。该区域先前被描述为与阿尔泰羊和阿瓦什羊的耳朵长度变异有关。包括 HMX1 附近候选重复基因型的映射模型作为固定效应解释了 OAR6 上的表型方差，并揭示了与耳朵长度相关的 OAR13 上的另一个全基因组显著位置。我们的研究结果结合已发表的证据表明，HMX1 附近进化上保守区域的重复是从中亚到中东、塞浦路斯、希腊和阿尔卑斯山的更大区域衍生的绵羊品种耳朵长度的主要调节因子。这种分布表明衍生等位基因的古老起源。
