Li Cong, Cai Wentao, Liu Shuli, Zhou Chenghao, Cao Mingyue, Yin Hongwei, Sun Dongxiao, Zhang Shengli, Loor Juan J
Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China.
College of Animal Science and Technology, Key Laboratory of Animal Genetics and Breeding of Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, China Agricultural University, Beijing 100193, China.
Asian-Australas J Anim Sci. 2020 Nov;33(11):1725-1731. doi: 10.5713/ajas.19.0549. Epub 2020 Feb 25.
An initial RNA-Sequencing study revealed that UDP-galactose-4-epimerase (GALE) was one of the most promising candidates for milk protein concentration in Chinese Holstein cattle. This enzyme catalyzes the interconversion of UDP-galactose and UDP-glucose, an important step in galactose catabolism. To further validate the genetic effect of GALE on milk protein traits, genetic variations were identified, and genotypes-phenotypes associations were performed.
The entire coding region and the 5'-regulatory region (5'-UTR) of GALE were re-sequenced using pooled DNA of 17 unrelated sires. Association studies for five milk production traits were performed using a mixed linear animal model with a population encompassing 1,027 Chinese Holstein cows.
A total of three variants in GALE were identified, including two novel variants (g.2114 A>G and g.2037 G>A) in the 5'-UTR and one previously reported variant (g.3836 G>C) in an intron. All three single nucleotide polymorphisms (SNPs) were associated with milk yield (p<0.0001), fat yield (p = 0.0006 to <0.0001), protein yield (p = 0.0232 to <0.0001) and protein percentage (p<0.0001), while no significant associations were detected between the SNPs and fat percentage. A strong linkage disequilibrium (D' = 0.96 to 1.00) was observed among all three SNPs, and a 5 Kb haplotype block involving three main haplotypes with GAG, AGC, and AGG was formed. The results of haplotype association analyses were consistent with the results of single locus association analysis (p<0.0001). The phenotypic variance ratio above 3.00% was observed for milk protein yield that was explained by SNP-g.3836G >C.
Overall, our findings provided new insights into the polymorphic variations in bovine GALE gene and their associations with milk protein concentration. The data indicate their potential uses for marker-assisted breeding or genetic selection schemes.
一项初步的RNA测序研究表明，尿苷二磷酸半乳糖-4-表异构酶（GALE）是中国荷斯坦奶牛乳蛋白含量最具潜力的候选基因之一。该酶催化尿苷二磷酸半乳糖和尿苷二磷酸葡萄糖的相互转化，这是半乳糖分解代谢中的重要一步。为了进一步验证GALE对乳蛋白性状的遗传效应，我们鉴定了其遗传变异，并进行了基因型与表型的关联分析。
利用17头无亲缘关系公牛的混合DNA对GALE的整个编码区和5'-调控区（5'-UTR）进行重测序。使用混合线性动物模型对1027头中国荷斯坦奶牛群体的五个产奶性状进行关联研究。
在GALE中共鉴定出三个变异，包括5'-UTR中的两个新变异（g.2114 A>G和g.2037 G>A）和一个内含子中先前报道的变异（g.3836 G>C）。所有三个单核苷酸多态性（SNP）均与产奶量（p<0.0001）、乳脂产量（p = 0.0006至<0.0001）、乳蛋白产量（p = 0.0232至<0.0001）和乳蛋白率（p<0.0001）相关，而未检测到SNP与乳脂率之间的显著关联。在所有三个SNP之间观察到很强的连锁不平衡（D' = 0.96至1.00），并形成了一个包含GAG、AGC和AGG三种主要单倍型的5 Kb单倍型块。单倍型关联分析结果与单基因座关联分析结果一致（p<0.0001）。SNP-g.3836G >C解释的乳蛋白产量的表型方差比高于3.00%。
总体而言，我们的研究结果为牛GALE基因的多态性变异及其与乳蛋白含量的关联提供了新的见解。数据表明它们在标记辅助育种或遗传选择方案中的潜在用途。
