大肠杆菌F4ac是侵染新生仔猪引发腹泻的主要病原菌。申请人及所在课题组前期通过全基因组连锁定位分析、目的区域的重组断点事件分析和远缘群体高通量SNP标记的关联性分析等严谨的遗传学分析手段，确定了仔猪F4ac腹泻易感基因为MUC13基因，但至今尚未鉴别到因果突变，最大障碍在于该基因编码区存在一个尚未解析的约10 Kb富含GC 的高度串联重复区域。本项目拟在此基础上，借鉴近期高GC含量串联重复区变异位点研究的成功案例，采用PacBio单分子实时测序技术并结合Sanger测序特殊拼接技术对MUC13 基因10 Kb串联重复编码区开展比较测序分析，将鉴别到的变异位点，在已有F4ac黏附表型的15 个中、西方猪种远缘群体292 个仔猪个体中开展多态性检测，通过与黏附表型进行关联性分析，并经大样本验证及功能分析，最终确定因果突变位点，并探究其遗传起源，进而全面揭示猪F4ac侵染腹泻的抗病分子遗传机理。

Enterotoxigenic Escherichia coli (ETEC) F4ac is a major determinant of diarrhea in neonatal and young pigs. We previously identified the F4ac receptor gene,MUC13,by a series of genetics technologies including whole-genome linkage mapping, recombination breakpoint analysis and association studies in a collection of diverse outbred populations. But the causative mutation has not been identified. It was inferred that the mutation might lie in ～10 Kb-long, GC-rich tandem repeat area in the coding region of the MUC13 gene. On the basis of these findings, we would sequence the tandem repeat area in the MUC13 gene by using single molecule sequencing and Sanger capillary sequencing. Then the identified polymorphisms would be genotyped on 292 outbred pigs representing 12 Chinese native pig breeds and 3 Western pig breeds. Association of MUC13 polymorphisms with susceptibility/resistance to ETEC F4ac will be performed to determine the causative mutation, which would be further validated by other pig population and functional analyses. The expected results of this study will provide novel insights into the molecular mechanism of ETEC F4ac disease resistance in pigs.