鉴别导致大白猪先天性无毛症的致因基因及因果突变

Pig coat is a unique phenotypic feature that formed in the process of evolution. Hair provides thermal regulation for pigs and protects the skin from wounds, bites and ultraviolet (UV) radiation, and is important in adaptation to volatile environments. Hairlessness in pigs have been reported in US Yucatan hairless, Mexican hairless and Iberian black pigs. However, the molecular mechanism of hairlessness remains elusive. Recently, a subpopulation of congenital hairless pigs of Large White have been established in a breeding farm in North of China. We have speculated the genetic model of this hairless population based on pidgree and phenoype records. The purpose of this project is to identify the responsible genes and causative mutations for the unique phenotype using the above hairless cases and normal controls, and using the methods, such as genome-wide association study (GWAS), RNAseq-based transcriptome analysis and whole-genome deep-resequencing, functional analysis of these resonable genes. The results would provide deep insights into genetics basis of pig hairlessness and be benefit to breeding hairless pigs for animal model and meat production.

猪的毛发对于体温调节、防止受伤、避免蚊叮虫咬和紫外线辐射等具有重要作用，是猪进化过程中形成的重要表型外貌特征。猪先天性无毛表型仅报道于美国尤卡坦猪、墨西哥无毛猪和部分西班牙伊比利黑猪，但至目前，猪无毛形成的分子遗传机制尚不清楚。本项目利用所获得的独特先天性无毛大白猪群体，通过表型和系谱分析，初步推断该先天性无毛症的遗传模式应为2个基因共同作用的结果。在此基础上，拟采用基于病例-对照的全基因组关联分析、皮肤转录组重测序、IBD精细定位、全基因组深度重测序等系统策略，定位并鉴别导致大白猪先天性无毛症的致因基因及因果突变，通过基因功能验证和调控网络构建，解析大白猪先天性无毛症的分子遗传机理。预期研究结果将为培育无毛猪实验动物模型和种猪新品种奠定坚实的理论和技术基础，并为哺乳动物和人类的毛发生长发育研究提供参考。

本研究采用一系列的遗传学分析手段，对大白猪先天性全身无毛症进行遗传机制解析，搜寻影响该罕见疾病模型的因果基因及因果突变，为培育新型无毛猪种提供理论和技术支持。.本研究通过表型和系谱分析，推断其是由单个基因内的低频隐性突变所引起的罕见遗传疾病。选取个80无毛个体和69正常个体进行60K SNP芯片GWAS分析，所有无毛个体在15号染色体ASGA0083771附近共享一个14.62Mb单倍型。通过全球猪种共享单倍型分析、连锁不平衡分析和群体遗传分化分析等多种策略进行QTL精细定位因果基因所在的置信区间，最终将因果基因所在的置信区间界定为1.47Mb（113.67 ~ 115.14Mb）区域。.利用60K SNP数据构建GWAS分析的个体进化树，从不同的亚群中选择了3头无毛个体和2头正常纯合子个体开展全基因组深度重测序。针对上述1.47Mb区间，搜寻所有与5头重测序个体歌曲区域单倍型所推断的基因型完全一致的SNP，鉴于此先天性无毛症仅见于该大白猪群体，导致该表型的因果突变应该为低频突变（次等位基因型频率≤0.05），然后针对这些SNP（n=51）在221头中国地方猪的重测序数据中及402头中西方猪种及野猪中搜寻低频突变位点，结果只发现1个低频突变（rs332500639），该突变位于MAIP1基因1号外显子上，将所编码的氨基酸从精氨酸改变为半胱氨酸。.将rs332500639加入GWASG群体的60K数据中进行全基因组关联性分析，发现其为最强关联性SNP（P值=6.17×10-85）。固定其效应之后，所有关联信号消失。这些都进一步支持rs332500639即是因果突变，MAIP1是导致大白猪先天性全身无毛症的致病基因。.