Identification and Screening of Gene(s) Related to Susceptibility to Enterotoxigenic Escherichia coli F4ab/ac in Piglets

In 2004, Jørgensen and coworkers proposed the MUC4 gene as a candidate gene of enterotoxigenic Escherichia coli (ETEC) F4ab/ac receptor in piglets and a mutation of G→C in intron 7 of MUC4 was identified to be associated with the ETEC F4ab/ac adhesion phenotypes. In this study, we used 310 piglets of three breeds (Landrace, Large White and Chinese Songliao Black) to analyze the relationship between this mutation and the F4ab/ac adhesion phenotype. The results show that the genotypes at this site and the ETEC F4ab/ac adhesion phenotypes were not completely consistent, although they are very strongly associated. Among the individuals with genotype CC, which was identified as a resistant genotype to F4ab/ac adhesion, only 72.1% (124/172) were non-adhesive to ETEC F4ab and 77.9% (134/172) were non-adhesive to ETEC F4ac infections. This suggests that this mutation may not be the causative mutation for ETEC F4ab/ac adhesion, rather, the actual causative mutation may be in another gene closely linked to MUC4, or at aother site within the MUC4 gene. Our results also suggest that the receptors of F4ab and F4ac may be determined by two different but closely linked loci. In order to screen other genes related to F4ab/ac adhesion in piglets, the mRNA profiles from six full sib piglets, of which three were adhesive to ETEC F4ab/ac and three non-adhesive, were analyzed by suppression subtractive hybridization (SSH). One upregulated gene, Ep-CAM, was selected for further analysis based on its role in the intestinal epithelial cells adhesion. Using real-time RTPCR, we found that the Ep-CAM gene was significantly up-regulated in the piglets adhesive to F4ab/ac. It was mapped to SSC3q11-q14 by radiation hybrid mapping. (