利用多个实验群体解析猪7号染色体上影响脂肪沉积的因果基因

Fat deposition trait is a major trait to determine the economic efficiency of the world pig industry. Depositing too much fat is the limiting factor to commercialize the Chinese indigenous pig breeds. Although many researchers have tried to decode the genetic mechanism, there are few causative genes having been identified so far. The applicants have mapped a quantitative trait locus (QTL) of fat deposition on chromosome 7 by genome-wide QTL mapping and genome-wide association analysis (GWAS) in an F2 resource population, and the QTL is versified by GWAS in other two indigenous pig breeds (Erhualian and Bamaxiang). This project aims to fine mapping the QTL by meta-analysis and identical by descent (IBD) analysis in the three populations. Furthermore, the QTL genotype of F1 boars and the found boars of the Erhualian and Bamaxiang populations will be inferred by marker-assisted regression analysis, and the target region of the F1 boars with known QTL genotype will be sequenced to obtain all polymorphic loci in the region. The polymorphic loci, of which genotypes are coincident with the QTL genotypes, will be genotyped in the three populations. The polymorphic loci associated with fat deposition strongly in the three populations will be pick out, and the IBD block of those loci is constructed. According to the physical location of IBD block on chromosome 7, the causative gene can be anchored, and its functions will be verified by constructing a relevant expression vector in a fat cell line. This project will uncover the causative gene for fat deposition trait on chromosome 7, and pave a way for gene breeding of fat deposition trait in pigs.

脂肪沉积性状直接影响养猪业的经济效益。脂肪沉积过多是我国地方猪种商业化的限制因素。虽然国内外众多学者对脂肪沉积进行了遗传解析，但是目前所鉴别的因果基因十分有限。项目组构建了一个F2资源群体，通过QTL定位和GWAS分析，在猪7号染色体上检测到一个极显著影响脂肪沉积的QTL。此外，我们还在二花脸和巴马香群体中验证了该QTL。本项目利用上述3个实验群体，拟通过荟萃分析和IBD分析，对该QTL进行精细定位。然后通过标记辅助分离分析，推测F1公猪及二花脸和巴马香群体始祖公猪的QTL基因型，并对基因型已知的个体进行目标区域测序，获取该区域内的所有多态位点。把与QTL基因型吻合的位点在这3个群体进行检验，筛选出强关联的位点。根据这些位点所在单倍型框的物理位置，锚定因果基因，并在脂肪细胞系中构建相应的表达载体，对其功能进行验证。最终鉴别7号染色体控制脂肪沉积的因果基因，为脂肪沉积性状的基因育种奠定基础。

背膘太厚是我国地方猪种和培育猪种商业化的限制因素。虽然国内外众多学者对背膘厚进行了遗传解析，但是目前为止背膘厚的遗传机理还不是很清楚。本项目测定了近3000个个体的背膘厚和SNP芯片，并通过多群体的GWAS，对7号染色体的QTL进行精细定位。然后通过标记辅助分离分析，推导F1公猪及二花脸和巴马香群体始祖公猪的QTL基因型。由于二花脸和巴马香群体始祖公猪的后代数较少，无法判断其QTL基因型。19头F1公猪中，推导出9头公猪的QTL基因型，并对这9头猪的目标区域进行测序，获取该区域内的所有多态位点。一共鉴别到274个SNP，其中有15个SNP的基因型与QTL基因型吻合。利用基因填充方法，获取这些位点在这些群体的基因型，筛选出强关联的位点。本研究鉴别的分子标记和积累的数据，为背膘厚的分子育种奠定基础。