Cooperative Research Centre for Sheep Industry Innovation, Armidale, NSW, 2351, Australia.
School of Environmental and Rural Science, University of New England, Armidale, NSW, 2351, Australia.
Genet Sel Evol. 2019 Jul 3;51(1):37. doi: 10.1186/s12711-019-0479-1.
This study aimed at identifying genomic regions that underlie genetic variation of worm egg count, as an indicator trait for parasite resistance in a large population of Australian sheep, which was genotyped with the high-density 600 K Ovine single nucleotide polymorphism array. This study included 7539 sheep from different locations across Australia that underwent a field challenge with mixed gastrointestinal parasite species. Faecal samples were collected and worm egg counts for three strongyle species, i.e. Teladorsagia circumcincta, Haemonchus contortus and Trichostrongylus colubriformis were determined. Data were analysed using genome-wide association studies (GWAS) and regional heritability mapping (RHM).
Both RHM and GWAS detected a region on Ovis aries (OAR) chromosome 2 that was highly significantly associated with parasite resistance at a genome-wise false discovery rate of 5%. RHM revealed additional significant regions on OAR6, 18, and 24. Pathway analysis revealed 13 genes within these significant regions (SH3RF1, HERC2, MAP3K, CYFIP1, PTPN1, BIN1, HERC3, HERC5, HERC6, IBSP, SPP1, ISG20, and DET1), which have various roles in innate and acquired immune response mechanisms, as well as cytokine signalling. Other genes involved in haemostasis regulation and mucosal defence were also detected, which are important for protection of sheep against invading parasites.
This study identified significant genomic regions on OAR2, 6, 18, and 24 that are associated with parasite resistance in sheep. RHM was more powerful in detecting regions that affect parasite resistance than GWAS. Our results support the hypothesis that parasite resistance is a complex trait and is determined by a large number of genes with small effects, rather than by a few major genes with large effects.
本研究旨在鉴定与澳大利亚绵羊大群体中蠕虫卵计数遗传变异相关的基因组区域，作为寄生虫抗性的指示性状，该群体使用高密度 600K 绵羊单核苷酸多态性阵列进行了基因分型。本研究包括来自澳大利亚不同地点的 7539 只绵羊，这些绵羊在野外混合胃肠道寄生虫物种中进行了挑战。采集粪便样本，并确定了三种 Strongyle 物种（即 Teladorsagia circumcincta、Haemonchus contortus 和 Trichostrongylus colubriformis）的蠕虫卵计数。使用全基因组关联研究（GWAS）和区域遗传力映射（RHM）对数据进行分析。
RHM 和 GWAS 均检测到 Ovis aries（OAR）染色体 2 上的一个区域，该区域与寄生虫抗性高度显著相关，基因组假发现率为 5%。RHM 揭示了 OAR6、18 和 24 上的其他显著区域。途径分析显示，这些显著区域内有 13 个基因（SH3RF1、HERC2、MAP3K、CYFIP1、PTPN1、BIN1、HERC3、HERC5、HERC6、IBSP、SPP1、ISG20 和 DET1），它们在先天和获得性免疫反应机制以及细胞因子信号传导中具有各种作用。还检测到参与止血调节和粘膜防御的其他基因，这些基因对绵羊抵御入侵寄生虫的保护很重要。
本研究鉴定了 OAR2、6、18 和 24 上与绵羊寄生虫抗性相关的显著基因组区域。RHM 在检测影响寄生虫抗性的区域方面比 GWAS 更有效。我们的研究结果支持寄生虫抗性是一种复杂性状的假设，由大量具有小效应的基因决定，而不是由少数具有大效应的主要基因决定。
