Ryan Cliona A, Berry Donagh P, Bugno-Poniewierska Monika, Burke Mary-Kate, Raudsepp Terje, Egan Sonja, Doyle Jennifer L
Teagasc, Moorepark, Fermoy, P61 P302 Co. Cork, Ireland.
Department of Animal Reproduction, Anatomy and Genomics, University of Agriculture in Krakow, Mickiewicza 24/28 Av., 30-059 Kraków, Poland.
Animals (Basel). 2025 Jun 22;15(13):1842. doi: 10.3390/ani15131842.
Autosomal trisomy, a genetic disorder characterized by the presence of an extra autosome, is a rare but important chromosomal abnormality in horses, often associated with infertility, developmental abnormalities, and reduced life expectancy. This study represents the largest population-level screening for autosomal trisomy in horses; the analysis used single nucleotide polymorphism (SNP) panel genotype intensity data from 17,078 horses, 6601 of which were juveniles (i.e., ≤12 months of age) when genotyped. Using methodologies adapted from similar screening studies in cattle, the only aneuploidy detected was trisomy 27 in two juvenile male Irish Sport Horses (ISH) (0.03% prevalence among juveniles or 0.01% prevalence in the overall population). One ISH colt was cytogenetically confirmed and displayed no overt external phenotypic abnormalities, while cytogenetics was not undertaken on the other ISH colt, nor was it phenotypically assessed. Parentage analysis revealed that one ISH colt inherited two different copies of chr27 from the sire, demonstrating heterodisomy, likely due to a nondisjunction event during meiosis I in the sire. The other ISH colt inherited two different copies of chr27 from the dam, also indicating heterodisomy; the dam was 23 years of age when the colt was born. Based on the observed prevalence of autosomal trisomy, it can be estimated that at least 3 foals per 10,000 live births are likely to have autosomal trisomy. Though, given that only 74 (i.e., 0.004%) of horses were genotyped within a month of birth, this is likely an underestimate. The economic consequence of undiagnosed trisomy in high-value breeding horses that are potentially infertile could be substantial. As horse genotyping for parentage verification and discovery is transitioning to medium-density single nucleotide polymorphism panels, routine genomic screening for autosomal aneuploidy could be readily undertaken and potentially should form a standard screening prerequisite along with other genetic defects at horse sales. Currently, thoroughbred horses registered for racing are not genotyped, and only a limited number of sport horse studbooks are using SNP genotyping. This highlights an opportunity for those already genotyping to expand their support for breeders through low-cost, high-value chromosomal screening at the time of registration rather than incurring additional costs over the horse's life cycle to determine the root cause of certain phenotypes owing to the undiagnosed trisomy.
常染色体三体是一种以存在一条额外常染色体为特征的遗传疾病，在马中是一种罕见但重要的染色体异常，常与不育、发育异常和预期寿命缩短有关。本研究是马常染色体三体最大规模的群体水平筛查；分析使用了来自17,078匹马的单核苷酸多态性（SNP）面板基因型强度数据，其中6601匹在进行基因分型时为幼年马（即≤12月龄）。采用从牛的类似筛查研究中改编的方法，检测到的唯一非整倍体是两匹幼年雄性爱尔兰运动马（ISH）中的27号染色体三体（在幼年马中的患病率为0.03%，在总体种群中的患病率为0.01%）。一匹ISH雄驹经细胞遗传学证实，未表现出明显的外部表型异常，而另一匹ISH雄驹未进行细胞遗传学检测，也未进行表型评估。亲权分析显示，一匹ISH雄驹从父本继承了两个不同的27号染色体拷贝，表现为异源二体性，可能是由于父本减数分裂I期间的不分离事件。另一匹ISH雄驹从母本继承了两个不同的27号染色体拷贝，也表明是异源二体性；这匹雄驹出生时母本23岁。根据观察到的常染色体三体患病率，可以估计每10,000例活产中至少有3匹驹可能患有常染色体三体。不过，鉴于只有74匹（即0.004%）马在出生后一个月内进行了基因分型，这可能是一个低估。对于可能不育的高价值种马中未诊断出的三体，其经济后果可能很大。随着用于亲权验证和发现的马基因分型正在向中密度单核苷酸多态性面板转变，可以很容易地进行常染色体非整倍体的常规基因组筛查，并且有可能应与马匹销售时的其他遗传缺陷一起形成标准的筛查前提条件。目前，注册参加比赛的纯种马没有进行基因分型，只有少数运动马种马登记簿正在使用SNP基因分型。这凸显了一个机会，即对于那些已经在进行基因分型的人来说，可以通过在注册时进行低成本、高价值的染色体筛查来扩大对育种者的支持，而不是在马的生命周期内产生额外费用来确定某些由于未诊断出的三体导致的表型的根本原因。
