CDNA Cloning Of The Porcine ITGB5 Gene And Its Association With Susceptibility To ETEC F4ac

Enterotoxigenic Escherichia coli F4ac (ETEC F4ac) is the major pathogens resulting in neonatal and young piglet diarrhea. F4ac bacteria adhere to specific receptors of enterocytes with adhesins and produce enterotoxins which stimulate the secretion of water and electrolytes into the gut lumen of small intestines and then lead to diarrhea. So susceptibility to ETEC F4ac is correlated with specific receptors on brush borders of pig intestinal villous enterocyte. Susceptibility to ETEC F4ac is dominantly inherited in Mendelian way and is controlled by a single gene. It is hence important to identify and isolate the ETEC F4ac receptor gene for ETEC F4ac diarrhea resistant breeding. Using a large scale white Duroc×Erhualian intercross resource population, we have mapped the locus for the ETEC F4ac intestinal receptor (F4acR) to a region of 3.0 Mb between UMNP997 and S0283 on pig chromosome 13 (SSC13). In the paper, ITGB5 was studied as a candidate gene for F4acR based on the results of comparative genomics, receptor biochemistry, tissue expression analysis and previous results of suppression subtractive hybridization reported by Ruhai et al. The cDNA of ITGB5 was cloned by the method of 5'-, 3'-RACE assays. SNPs were identified by comparative sequencing and were genotyped by PCR-SNaPShot in a total of 144 pigs from western commercial including Duroc, Large White and Landrace. The association of SNP genotypes with in vitro ETEC F4ac adhesion phenotypes was evaluated by SAS software. The result showed that the complete cDNA of ITGB5 was isolated and six SNPs including c.1580G>A, c.1715C>T, c.2744G>A, c.920C>T, g.31420C>A and g.31487G>A, were identified. The association of six SNP genotypes showed significant association with susceptibility to ETEC F4ac (P<0.01). However, the significance levels of ITGB5 SNPs were remarkably lower than the previously characterized MUC13 markers. On the basis of all findings, we concluded that MUC13 is the responsible gene encoding F4acR, and ITGB5 is closely linked with the MUC13 gene. This study enriched the understanding of the ETEC F4ac receptor gene in porcine small intestine, and benefit the dissection of the genetic mechanism of resistance to diarrhea caused by ETEC F4ac in pigs.