Characteristics of miRNAs present in bovine sperm and associations with differences in fertility.

Small non-coding RNAs have been linked to different phenotypes in bovine sperm, however attempts to identify sperm-borne molecular biomarkers of male fertility have thus far failed to identify a robust profile of expressed miRNAs related to fertility. To explore differences in fertility that are not apparent using standard visible metrics of sperm quality, we employed Next Generation Sequencing to compare the miRNA populations in Bos taurus sperm from bulls with comparablemotility and morphology but varying Sire Conception Rates. We identified the most abundant miRNAs in both populations and evaluated differences in the overall levels and specific patterns of isomiR expression. We also explored correlations between specific pairs of miRNAs in each population and identified 10 distinct pairs of miRNAs that were positively correlated in bulls with higher fertility and negatively correlated in comparatively less fertile individuals. Furthermore, 8 additional miRNA pairs demonstrated the opposite trend; negatively correlated in high fertility animals and positively correlated in less fertile bulls. Finally, we performed pathway analysis to identify potential roles of miRNAs present in bull sperm in the regulation of specific genes that impact spermatogenesis and embryo development. Together, these results present a comprehensive picture of the bovine sperm miRNAome that suggests multiple potential roles in fertility.

已有研究证实，小型非编码RNA与牛精子的多种表型密切相关。然而，此前针对精子源性雄性生育力分子生物标志物的鉴定尝试，均未能筛选出与生育力相关的、表达稳定的微小RNA（miRNA）表达谱。
为了探究通过标准精子质量可视指标无法显现的生育力差异，本研究采用下一代测序（Next Generation Sequencing）技术，对具有相似运动能力与形态学特征，但公牛受胎率（Sire Conception Rates）存在差异的肉牛（Bos taurus）精子中的miRNA群体开展比较分析。
本研究首先鉴定了两组样本中丰度最高的miRNA，并评估了其整体表达水平以及同工miRNA（isomiR）的特异性表达模式差异。此外，我们还分析了两组样本中特定miRNA对之间的表达相关性，鉴定出10组特异性miRNA对：在高生育力公牛中呈正相关，而在生育力相对较低的个体中呈负相关。另有8组miRNA对则呈现相反趋势：在高生育力个体中呈负相关，而在生育力较低的公牛中呈正相关。
最后，本研究通过通路分析，探究了公牛精子中存在的miRNA在调控影响精子发生与胚胎发育的特定基因方面的潜在功能。综上，本研究结果全面描绘了牛精子miRNA组（miRNAome）的特征，表明其在生育调控中存在多种潜在作用。