小尾寒羊泌乳性状关键circRNAs筛选及其功能研究

泌乳性能直接决定了多羔绵羊后代的成活率和生长速度，但其调控机制尚不完全清楚。我们前期已采集高泌乳性能和低泌乳性能小尾寒羊泌乳期的乳腺，获得了全转录组数据和32个差异表达circRNAs。本项目从中筛选出真实存在且表达量较高的差异circRNAs，基于靶向预测及前期测序数据，构建circRNA-miRNA-mRNA网络，研究circRNAs对乳腺上皮细胞的影响，确定2个关键circRNAs，开展以下研究：①研究关键circRNAs在乳腺上皮细胞中的定位、成环机制和半衰期；②研究过表达和沉默circRNA对靶miRNA，及miRNA对mRNA的影响，分析3类RNA的细胞共定位；③研究过表达circRNA是否能拮抗miRNA对mRNA的抑制作用，建立ceRNA通路，分析其对下游基因的影响。项目将阐明关键circRNAs调控乳腺上皮细胞和泌乳性状的分子机制，为改良舍饲多羔绵羊泌乳性能提供理论基础。

Although milk performance traits directly determine survival rates and growth rates of multiple-born lambs, little is known about molecular mechanism regulating the traits. In our previous study, the whole transcriptome and 32 differentially expressed circular RNAs (circRNAs) were obtained in mammary gland at peak-lactation period from high-lactating performance and low-lactating performance of Small-Tailed Han ewes. In the study, reliable differentially expressed circRNAs with high expression levels will be screened from 32 differentially expressed circRNAs. Based on the targeted prediction results and whole transcriptome sequencing data obtained from previous study, the interaction network of circRNA-miRNA-mRNA will be constructed. The effect of circRNAs on mammary epithelial cells will be investigated and two key circRNAs will then be ascertained. The study of the following three parts for the two key circRNAs will be carried out. Firstly, the location on mammary epithelial cells, circle formation mechanism and half-life of the two key circRNAs will be studied. Secondly, the effect of over-expressed and silenced circRNAs on microRNAs (miRNAs), and over-expressed and silenced miRNAs on mRNAs will be analysed. The location of circRNAs, their target miRNAs and mRNAs on mammary epithelial cells will also be located. Finally, the antagonistic effect of circRNAs on the inhibition of miRNAs on mRNAs will be explored. The competing endogenous RNA (ceRNA) pathways for the two circRNAs will be established and the effect of these circRNAs on functional genes in downstream of the pathways will be studied. The results will identify the possible molecular mechanisms underlying mammary epithelial cells activity and milk performance traits for the two key circRNAs and give us the theoretical basis about genetic improvement for milk performance traits in house-fed multiple-born-lambs sheep breeds.