Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853, USA.
Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, New York, 14853, USA.
Genes Immun. 2019 Nov;20(8):660-670. doi: 10.1038/s41435-019-0075-y. Epub 2019 May 9.
The Icelandic horse has been maintained as a closed population in its eponymous homeland for many generations, with no recorded introductions of new horses of any breed since the year 1000 CE. Here we determined the diversity of major histocompatibility complex (MHC) haplotypes in 156 Icelandic horses from two groups, based on a panel of 12 polymorphic intra-MHC microsatellites tested in families of various composition. We identified a total of 79 MHC haplotypes in these two groups, including one documented intra-MHC recombination event from a total of 147 observed meioses. None of these MHC haplotypes have been previously described in any other horse breed. Only one MHC homozygote was found in the entire population studied. These results indicate a very high level of MHC heterozygosity and haplotype diversity in the Icelandic horse. The environment in Iceland is remarkable for its lack of common agents of equine infectious disease, including equine herpesvirus type 1, influenza virus, and streptococcus equi. The driving forces for maintenance of MHC heterozygosity in Icelandic horses must thus be sought outside of these major horse pathogens. Based on our results, we propose that intra-MHC recombination may play a major role in the generation of novel haplotypes.
冰岛马在其同名的家乡已经作为一个封闭的种群被维持了许多代，自公元 1000 年以来，没有记录到任何新的马种的引入。在这里，我们基于在不同组成的家庭中测试的 12 个多态性 MHC 内微卫星，确定了来自两个群体的 156 匹冰岛马的主要组织相容性复合体 (MHC) 单倍型的多样性。我们在这两个群体中总共鉴定出了 79 个 MHC 单倍型，其中包括总共 147 个观察到的减数分裂中的一个记录的 MHC 内重组事件。这些 MHC 单倍型在任何其他马品种中都没有被描述过。在整个研究的群体中只发现了一个 MHC 纯合子。这些结果表明，冰岛马的 MHC 杂合性和单倍型多样性非常高。冰岛的环境以缺乏马属动物传染病的常见病原体为特点，包括马疱疹病毒 1 型、流感病毒和马链球菌。因此，维持冰岛马 MHC 杂合性的驱动力必须在这些主要的马病原体之外寻找。基于我们的结果，我们提出 MHC 内重组可能在新单倍型的产生中起主要作用。
