Data from: A major gene for bovine ovulation rate

Half-sib daughters sired by a bull believed to be a carrier of a major gene for high ovulation rate were evaluated for ovulation rate and genotyped in an effort to both test the hypothesis of segregation of a major gene and to map the gene’s location. A total of 131 daughters were produced over four consecutive years at a University of Wisconsin-Madison research farm. All were evaluated for ovulation rate over an average of four estrous cycles using transrectal ultrasonography. The sire and all daughters were genotyped using a 3K SNP chip and the genotype and phenotype data were used in a linkage analysis. Subsequently, daughters recombinant within the QTL region and the sire were genotyped successively with 50K and 777K SNP chips to refine the location of the causative polymorphism. Positional candidate genes within the fine-mapped region were examined for polymorphism by Sanger sequencing of PCR amplicons encompassing coding and 5’ and 3’ flanking regions of the genes. Sire DNA was used as template in the PCR reactions. Strong evidence of a major gene for ovulation rate was observed (p<1x10-28) with the gene localized to bovine chromosome 10. Fine-mapping subsequently reduced the location to a 1.2 Mb region between 13.6 and 14.8 Mb on chromosome 10. The location identified does not correspond to that for any previously identified major gene for ovulation rate. This region contains three candidate genes, SMAD3, SMAD6 and IQCH. While candidate gene screening failed to identify the causative polymorphism, three polymorphisms were identified that can be used as a haplotype to track inheritance of the high ovulation rate allele in descendants of the carrier sire.本研究针对一头被推测携带高排卵率主效基因的公牛所繁育的半同胞子代母牛群体，开展排卵率表型测定与基因分型实验，旨在验证主效基因分离假说并定位该基因的染色体位置。共计131头子代母牛于连续四年间在威斯康星大学麦迪逊分校的实验牧场繁育获得，所有子代母牛均通过直肠超声检查，在平均4个发情周期内完成排卵率表型测定。该种公牛与所有子代母牛均采用3K单核苷酸多态性（Single Nucleotide Polymorphism, SNP）芯片完成基因分型，随后将基因型与表型数据用于连锁分析。针对数量性状基因座（Quantitative Trait Locus, QTL）区域内发生重组的子代母牛与该种公牛，研究团队依次采用50K与777K SNP芯片进行基因分型，以精准定位致病多态性位点的位置。针对精细定位后的区域内的位置候选基因，研究人员通过对包含基因编码区及5'、3'侧翼区域的聚合酶链式反应（Polymerase Chain Reaction, PCR）扩增产物进行桑格测序（Sanger sequencing），筛查其多态性位点，实验以该种公牛的DNA作为PCR反应的模板。本研究观测到高排卵率主效基因存在的强显著性证据（p<1×10^-28），并将该基因定位至牛10号染色体；后续的精细定位将该基因的位置缩小至10号染色体上13.6 Mb至14.8 Mb之间的1.2 Mb区域内。本次定位的区域与此前已报道的所有高排卵率主效基因的位置均不重合，该区域包含三个候选基因：SMAD3、SMAD6与IQCH。尽管候选基因筛查未直接找到致病多态性位点，但本研究鉴定出三个多态性位点，可用于构建单倍型以追踪该高排卵率等位基因在携带公牛后代中的遗传传递情况。