Sammad Abdul, Zhang Hailiang, Shi Rui, Dong Yixin, Luo Hanpeng, Chen Ziwei, Liu Lin, Guo Gang, Liu Aoxing, Wang Yachun
Key Laboratory of Animal Genetics, Breeding and Reproduction, MARA, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China.
Beijing Dairy Cattle Center, Beijing, China.
Front Genet. 2022 Jun 8;13:882951. doi: 10.3389/fgene.2022.882951. eCollection 2022.
In our previous GWAS of Chinese and Nordic dairy cattle, genes , and locating on BTA 13 were suggested as candidate genes for reproduction. In this study, validation of these associations was performed in an independent population with records of nine reproductive traits. More importantly, functions of these genes in the reproductive process were verified by employing the expression data of ovarian follicles. The potential variants within the three genes were firstly detected in 68 Chinese Holstein bulls, and then screened in 1,588 Chinese Holstein cows using the KASP (Kompetitive allele-specific PCR) method. There were nine variants with polymorphisms in , five in and four in , respectively, of which one SNP was in the upstream regulatory region, two in exon region, four in downstream regulatory region, and 11 SNPs in intronic regions. Amongst the 18 variants, g.33267056T/G in explained the largest phenotypic variance for age at first calving (0.011%), interval from first to last insemination (0.004%), and calving ease (0.002%), while g.32751518G/A in contributed the most to stillbirth in heifers (0.038%). Two haplotype blocks were constructed for while one each for and , which were significantly associated with five reproductive traits, including age at the first service, age at the first calving, calving ease in heifers and cows, and the interval from calving to the first insemination. We then studied the profile of gene expression in granulosa cells isolated from four developmental stages of ovarian follicles from eight dairy cows. All three genes were differentially expressed between ovarian follicles with different sizes ( < 0.05), indicating their potential roles in the reproductive process of dairy cows. This study successfully demonstrated the associations of three BTA 13 genes , and with reproduction and further examined their expression levels in ovarian follicles directly. These findings can be beneficial for the ongoing genomic selection program for reproductive traits which have long been considered as traits that are difficult to achieve genetic improvement due to the lack of efficient genetic markers.
在我们之前对中国和北欧奶牛进行的全基因组关联研究（GWAS）中，位于牛13号染色体（BTA 13）上的基因 、 和 被认为是繁殖性状的候选基因。在本研究中，在一个具有9种繁殖性状记录的独立群体中对这些关联进行了验证。更重要的是，通过利用卵泡的表达数据验证了这些基因在繁殖过程中的功能。首先在68头中国荷斯坦公牛中检测了这三个基因内的潜在变异，然后使用竞争性等位基因特异性PCR（KASP）方法在1588头中国荷斯坦母牛中进行筛选。基因 中有9个变异具有多态性，基因 中有5个，基因 中有4个，其中1个单核苷酸多态性（SNP）位于上游调控区，2个位于外显子区，4个位于下游调控区，11个SNP位于内含子区。在这18个变异中，基因 中的g.33267056T/G对首次产犊年龄（0.011%）、首次配种至最后一次配种间隔（0.004%）和产犊难易度（0.002%）的表型变异解释最大，而基因 中的g.32751518G/A对小母牛死产的贡献最大（0.038%）。为基因 构建了两个单倍型块，基因 和 各构建了一个，它们与5种繁殖性状显著相关，包括首次输精年龄、首次产犊年龄、小母牛和母牛的产犊难易度以及产犊至首次配种间隔。然后，我们研究了从8头奶牛卵巢卵泡的四个发育阶段分离的颗粒细胞中的基因表达谱。所有三个基因在不同大小的卵泡之间均有差异表达（ < 0.05），表明它们在奶牛繁殖过程中的潜在作用。本研究成功证明了牛13号染色体上的三个基因 、 和 与繁殖的关联，并进一步直接检测了它们在卵泡中的表达水平。这些发现对于正在进行的繁殖性状基因组选择计划可能有益，长期以来繁殖性状一直被认为是由于缺乏有效的遗传标记而难以实现遗传改良的性状。
