Departamento de Mejora Genética Animal, INIA, 28040 Madrid, Spain.
IRIAF-CERSYRA, Valdepeñas 13300, Ciudad Real, Spain.
Animal. 2021 Feb;15(2):100065. doi: 10.1016/j.animal.2020.100065. Epub 2020 Dec 27.
Sperm quality traits routinely collected by artificial insemination (AI) center for rams progeny test are related with the capacity to produce sperm doses for AI and, in more or less grade, with males' fertility. Low-quality ejaculates are unuseful to perform AI sperm doses, which suppose high economic loses for the AI center. Moreover, sperm quality traits have low heritability values which make traditional genetic selection little efficient to its improvement. In this work, a genome-wide association study (GWAS) was conducted by using sperm quality traits data and 50 K Affymetrix custom chip genotypes of 429 rams of Assaf breed from OVIGEN AI centre. Furthermore, 47 of these rams were also genotyped with the Illumina HD Ovine BeadChip, and therefore HD genotypes were imputed for all rams with phenotype data. Previous to the GWAS, a linear regression model was fitted including sperm traits as dependent variables; the flock of origin, date of sperm collection, and jump number as fixed effects; rams age at collection in months as covariate; and ram permanent effect as random. Pseudo-phenotypes obtained from this model were used as input for GWAS. Associations at the chromosome-wise level (FDR 10%) of 76 single-nucleotide polymorphisms (SNPs) in 4 chromosomes for ejaculate concentration (CON), 20 SNPs in 3 chromosomes for ejaculate volume (VOL), 32 SNPs in 1 chromosome for ejaculate number of spermatozoa (SPZ), and 23 SNPs for spermatozoa mass motility (MOT) in 17 chromosomes were found. Only SNPs associated with MOT overcame the genome-wide significance level. Some candidate genes for sperm traits variability were SLC9C1 (OAR1), TSN (OAR2), and FUT10 (OAR26) for MOT;. DOCK2, CPLANE1, SPEF2, and RAI14 (OAR16) for CON; SCAPER and PSMA4 (OAR18) for VOL; and PARM1 and LOC101110593 (OAR6) for SPZ. SNPs associated with sperm traits were not found to be correlated with milk production genetic variation; however, the high frequencies of some SNPs with negative effect over sperm traits found in animals at the top milk yield estimated breeding values (EBVs) ranking would allow to exert some selective presure to improve rams sperm performances. Effects and frequencies of some of the SNPs detected over sperm quality traits make these variants good candidates to be used in marker-assisted selection to improve sperm characteristics of Assaf rams and AI center efficiency to produce sperm doses.
精子质量特征通常由人工授精（AI）中心收集，用于公羊后代测试，与产生 AI 精子剂量的能力有关，在不同程度上与雄性的生育能力有关。低质量的精液不适用于进行 AI 精子剂量，这会给 AI 中心带来巨大的经济损失。此外，精子质量特征的遗传力值较低，使得传统的遗传选择对其改善效果不大。在这项工作中，我们对来自 OVIGEN AI 中心的 429 只 Assaf 品种公羊的精子质量特征数据和 50K Affymetrix 定制芯片基因型进行了全基因组关联研究（GWAS）。此外，其中 47 只公羊还使用 Illumina HD 绵羊珠芯片进行了基因分型，因此所有具有表型数据的公羊的 HD 基因型都进行了推断。在 GWAS 之前，我们拟合了一个线性回归模型，将精子特征作为因变量；原始羊群、精子采集日期和跳跃次数作为固定效应；公羊在采集时的月龄作为协变量；公羊的永久效应作为随机效应。从该模型中获得的拟表型被用作 GWAS 的输入。在 4 号染色体上与精子浓度（CON）相关的 76 个单核苷酸多态性（SNP）、3 号染色体上与精液量（VOL）相关的 20 个 SNP、1 号染色体上与精子数（SPZ）相关的 32 个 SNP，以及在 17 号染色体上与精子质量运动性（MOT）相关的 23 个 SNP 中，发现了在染色体水平上（FDR 10%）的关联。只有与 MOT 相关的 SNP 超过了全基因组显著性水平。一些与精子特征变异性相关的候选基因有 SLC9C1（OAR1）、TSN（OAR2）和 FUT10（OAR26）与 MOT 有关；DOCK2、CPLANE1、SPEF2 和 RAI14（OAR16）与 CON 有关；SCAPER 和 PSMA4（OAR18）与 VOL 有关；PARM1 和 LOC101110593（OAR6）与 SPZ 有关。与精子特征相关的 SNP 并未发现与牛奶生产遗传变异相关；然而，在估计的繁殖值（EBV）排名中处于牛奶产量最高的动物中发现的一些 SNP 具有负效应对精子特征的高频，这将允许对提高公羊精子性能施加一些选择性压力。在精子质量特征上检测到的一些 SNP 的效应和频率使得这些变体成为标记辅助选择的良好候选物，以提高 Assaf 公羊和 AI 中心生产精子剂量的效率。
