奶牛乳成分性状形成的调控通路研究及关键基因鉴定

It has been shown that adding molecular information of functional genes with large genetic effects on objective traits into the SNP chip could increase the accuracy for prediction of genomic breeding values in dairy cattle. Thus, the purpose of this study is aimed to identify key genes and pathways affecting milk protein and fat traits. First, using RNA-seq，small RNA-seq and antibody chip technologies, we will analyze the complex transcriptome and protenome profiles of 32 liver and mammary gland samples collected from two lactation status (dry period and lactation peak) and cows with extremly high and low milk protein and fat percentages during lactation peak (high and low groups). Further, significantly expressed genes, miRNAs, lncRNAs and proteins between dry period and lactation peak but also between high and low groups will be identified. Subsequently, candidate key genes, miRNAs and lncRNAs for milk protein and fat traits and corresponding ceRNAs will be determined using integrated analysis. Finally, we will validate the genetic effects of such candidate genes in Chinese Holstein population in Beijing region, and then investigate the biological functions of the candidates with large effects based on liver and mammary gland cell lines in order to determine the ture major genes and mutations that can be applied in genetic improvement program of dairy cattle, elucidate the pathways and regulatory mechanims for milk protein and fat formation, and investigate cross-talks between liver and mammary gland during these processes, providing valuble molecular information for breeding of new dairy cattle strains with high quality milk composition.

研究表明，在SNP标记数据中加入目标性状遗传效应较大的已知功能基因信息，可提高奶牛基因组育种值预测准确性，本项目旨在鉴定奶牛乳蛋白、乳脂性状关键基因及通路。研究内容包括：1）利用转录组测序和抗体芯片技术，分析中国荷斯坦牛两个泌乳阶段（干奶期、泌乳高峰期）及泌乳高峰期极端表型个体（高/低乳蛋白率、乳脂率）的肝脏、乳腺上皮的完整转录组和蛋白质组图谱；2）鉴定泌乳阶段间、表型高/低组间的差异表达mRNAs/ miRNAs/ lncRNAs /蛋白质，经整合分析，发掘乳蛋白、乳脂性状关键基因、非编码RNAs及其ceRNAs；3）基于北京地区奶牛群体、肝脏和乳腺上皮细胞系及模式动物，进行基因遗传效应分析和功能验证，最终鉴定具有重要育种价值的关键基因及突变位点，解析性状形成的调控通路，探究肝脏和乳腺上皮在乳蛋白、乳脂合成过程的cross-talk协同机制，为选育优质乳成分奶牛新品系提供有效的分子信息。

2008年以来，我国奶牛生产水平稳步提高，但产量、品质及生产效率等仍与国际先进水平存在不同程度的差距，核心优质种源进口依赖度高。提升品种改良和种质创新能力是首要问题，具有重要育种价值的功能基因挖掘与验证工作严重不足，亟需加快破解遗传基础科学问题，全面提升我国奶牛高产优质高效性状新基因资源自主创制能力。. 本项目在国内率先完成了荷斯坦奶牛3个泌乳阶段肝脏组织、极端高/低乳蛋白率和乳脂率荷斯坦奶牛肝脏与乳腺上皮组织的全转录组、蛋白质组、染色质开放、全基因组甲基化图谱；通过生物信息学分析，挖掘到乳蛋白、乳脂性状关键基因40个、ceRNAs41个及一些miRNA、lncRNA；构建了乳蛋白、乳脂性状形成的调控网络1个及相关转录因子和甲基化对靶基因调控网络1个；初步阐明了肝脏和乳腺上皮组织在乳蛋白、乳脂合成过程中的协同作用；对EEF1D、COL6A1等3个基因进行了大群体遗传效应分析及系统功能解析。.. 研究结果为奶牛重要性状遗传机制解析提供了重要数据和理论依据、为我国自主研发奶牛全基因组育种SNP芯片提供了重要的基因信息，具有重要的科学意义和应用前景。