Sarova N, Ahlawat S, Grewal A, Sharma R, Arora R
ICAR-National Bureau of Animal Genetic Resources, Karnal, India.
University Institute of Engineering and Technology, Kurukshetra, India.
Reprod Domest Anim. 2018 Aug;53(4):914-920. doi: 10.1111/rda.13187. Epub 2018 Mar 31.
In India, cross-breeding of indigenous cattle with exotic cattle such as Holstein Friesian and Jersey has been going on since last four decades to improve milk production. Although it has led to increased milk yield, the subfertility in male cross-bred progeny has remained a significant problem. Epigenetic modifications (DNA methylation, histone modifications and chromatin remodelling) are regarded as key players influencing gene expression. DAZL gene plays an important role in germline development and gametogenesis. The methylation and mRNA expression level of this gene have been significantly negatively correlated in the testes of cattle-yak hybrids and their parents. This study analysed the methylation profile of DAZL gene promoter in bull spermatozoa in an attempt to speculate its role in cross-bred cattle subfertility. Semen samples from Sahiwal, Holstein Friesian and Frieswal bulls (Sahiwal X Holstein Friesian) with varying semen motility parameters were collected, and DNA was isolated. Methylation-specific primers were used to amplify part of promoter and exon 1 of DAZL gene using bisulphite-converted DNA. The amplified products were sequenced after cloning in pTZ57R/T vector. Sequence analysis revealed significantly higher DNA methylation of DAZL gene in Frieswal bulls with poor motility (28.26%) as compared to medium (15.21%) and high motility phenotype (6.52%). In pure-bred counterparts, Sahiwal and Holstein Friesian, epigenetic marks were more in the former (15.21%) than the latter (4.34%), but in both cases, the values were lower as compared to the poor motility Frieswal bulls. This suggests that differential hypermethylation of the CpG islands could possibly influence reproductive parameters in bovines.
在印度，本地牛与诸如荷斯坦弗里生牛和泽西牛等外来牛种的杂交已经持续了四十年，目的是提高牛奶产量。尽管这导致了牛奶产量的增加，但杂交雄性后代的生育力低下仍然是一个重大问题。表观遗传修饰（DNA甲基化、组蛋白修饰和染色质重塑）被认为是影响基因表达的关键因素。DAZL基因在生殖细胞发育和配子发生中起着重要作用。该基因的甲基化和mRNA表达水平在牦牛杂交牛及其亲本的睾丸中呈显著负相关。本研究分析了公牛精子中DAZL基因启动子的甲基化谱，试图推测其在杂交牛生育力低下中的作用。收集了具有不同精液活力参数的萨希瓦尔牛、荷斯坦弗里生牛和弗里瓦尔牛（萨希瓦尔牛×荷斯坦弗里生牛）的精液样本，并提取了DNA。使用甲基化特异性引物，以亚硫酸氢盐转化的DNA扩增DAZL基因启动子的一部分和外显子1。扩增产物在pTZ57R/T载体中克隆后进行测序。序列分析显示，活力差的弗里瓦尔牛中DAZL基因的DNA甲基化水平（28.26%）显著高于中等活力（15.21%）和高活力表型（6.52%）。在纯种对应物萨希瓦尔牛和荷斯坦弗里生牛中，前者（15.21%）的表观遗传标记比后者（4.34%）更多，但在这两种情况下，与活力差的弗里瓦尔牛相比，该值都较低。这表明CpG岛的差异高甲基化可能会影响牛的繁殖参数。
