乳房炎是奶牛业最常见、造成损失最严重的疾病。miRNA是一类进化上保守、长度约为22 nt的单链非编码小分子RNA，通过与靶基因相互作用，参与细胞增殖与分化、疾病发生与转移等过程。本研究拟利用分子生物学、生物信息学和基因组学等方法，首先采用两种乳房炎致病菌对荷斯坦牛进行体外感染，利用表达谱芯片、荧光定量PCR、miRNA测序等技术，比较两种致病菌导致奶牛乳房炎在基因和miRNA的表达差异，构建miRNA参与奶牛乳房炎调控网络结构图，并利用TargetScan、PicTar等软件，预测表达差异较大miRNA的靶基因，并进一步验证。最后用荧光素酶双报告基因法验证miRNA的靶位点，同时结合大样本SNP分析及乳房炎抗性记录，验证靶位点突变对乳房炎易感性的影响，揭示miRNA在奶牛乳房炎发病过程中的分子调控机制，为荷斯坦牛乳房炎防治及抗性新品系选育提供科学依据。

Mastitis was the most prevalent and costly diseases affecting dairy production. MicroRNAs (miRNAs), which are evolutionarily well-conserved, 22-nucleotide-long, small non-coding RNAs, are widely involved in the regulation of multiple biological processes, such as development, cell proliferation, diseases occurrence and metastasis interacting with the target gene. The molecular biology, bioinformatics and functional genomics methods were using in this study. Firstly, the mammary gland of Holstein cows were induced by two kinds of mastitis pathogens, and the gland were sampled. The expression of gene and miRNA in mammary gland were compared for healthy and mastitis cows by gene chip ,RT-PCR and miRNA sequencing, and to predict target genes and constructe the network between miRNA and target genes with TargetScan and PicTar softwares. The target site of miRNA were validated by dual luciferase report gene. Finally, the associations between the SNP mutaiton of target sites and mastitis susceptibility of Holstein cows were analyzed and confirmed by statistical method in large population of dairy cows. These results will provide scientific basis for revealing of regulation mechanism of miRNA in the pathogenesis of mastitis, prevention and breeding of Holstein with mastitis resistance.