奶山羊乳蛋白含量关键调控基因的筛选与功能分析

Applying molecular selective breeding strategies to improve the important economic traits for livestock and poultry have become hot topics in animal breeding. However, identification of key genes or causal variations on important economic traits are the preconditions to conduct molecular selective breeding strategies. As an important index to evaluate the nutritional value in goat’s milk, to date, no key genes or causal variations for milk protein concentration were found in dairy goats. A systematic screening strategy for the key regulatory genes on goat milk protein concentration is scarce. Therefore，using Xinong Saanen dairy goats as the experimental animals, this project aims at identifying and screening the functional candidate genes for milk protein concentration. Paired-end RNA-Seq will be used to explore the transcriptome from the biopsied mammary glands of ten Xinong Saanen dairy goats with five extremely high and five low phenotypic values for milk protein percentage during the peak lactation period. Resource population should be established and the genetic parameters of milk protein traits of Xinong Saanen dairy goats will be estimated, and the promising candidate genes will be selected to conduct the genetic effect analysis in a large population. Based on the promising candidate gene determined as having the largest genetic effects on phenotypes, we will investigate the overexpression and interference of the target gene from cellular level to elucidate its specific function, and the regulatory mechanism of milk protein synthesis will be revealed. Our findings will enrich the theoretical evidences and molecular sources for further designing molecular selective breeding strategies to optimize the contents of milk protein and to improve the milk quality, and also provide compacted sound basis for illuminating the molecular mechanism on milk protein synthesis in dairy goats.

利用分子选择育种技术进行畜禽重要经济性状改良是目前畜禽研究的热点。而实施分子育种的前提是鉴定影响重要经济性状的关键基因或致因突变。乳蛋白含量作为评价羊乳营养价值的重要指标，尚未发现控制乳蛋白含量高低的关键基因或致因突变，系统筛选调控奶山羊乳蛋白含量的关键基因研究缺乏。因此，本项目以西农萨能奶山羊为研究对象，通过对处于泌乳高峰期具有极端高和极端低乳蛋白率各5只奶山羊乳腺组织进行转录组测序，鉴定调控乳蛋白含量的功能候选基因；建立资源群体，估计西农萨能奶山羊乳蛋白性状的遗传参数，选取关键候选基因进行大群体遗传效应分析；基于确定的有最大遗传效应的关键基因，从细胞水平开展基因的过表达与干扰研究验证其功能，揭示关键基因对乳蛋白合成的调控机制。研究结果为奶山羊实施分子选择育种提高乳蛋白含量、改善乳品质提供分子素材和理论依据，为深入阐明乳蛋白合成的分子机理奠定基础。

鉴定影响畜禽重要经济性状的关键基因或致因突变是实施分子育种的前提。乳蛋白含量作为评价羊乳营养价值的重要指标，尚缺乏调控其高低的关键基因或致因突变的报道，因此，本研究系统筛选调控奶山羊乳蛋白含量的关键基因：（1）采集了处于泌乳高峰期具有极端高和极端低乳蛋白率各3只西农萨能奶山羊乳腺组织进行了转录组测序，确定了候选功能基因筛选策略，筛选出调控乳蛋白含量的功能候选基因35个；（2）构建了384只奶山羊的资源群体，获得了西农萨能奶山羊的乳蛋白率曲线，并估计乳蛋白率的遗传力为0.204，揭示SLC7A5和SLC5A1基因对奶山羊乳蛋白率有显著影响；（3）从细胞水平揭示了1个关键基因CSN1S1通过JAK2/STAT5a通路抑制CSN2启动子活性进而抑制β-酪蛋白的合成；初步解析了SERPINA1、SLC7A5、SLC5A1等3个关键候选基因对奶山羊乳蛋白合成的影响。研究结果为奶山羊实施分子选择育种提高乳蛋白含量、改善乳品质提供了有价值的基因信息，为深入阐明乳蛋白合成的分子机理奠定了基础。