Inheritance of the F4ab, F4ac and F4ad E. coli receptors in swine and examination of four candidate genes for F4acR

Abstract

Susceptibility to enterotoxigenic Escherichia coli with fimbriae F4ac is dominantly inherited in the pig. A three-generation pedigree was created to refine the position of F4acR on chromosome 13 comprising 202 pigs: eight parents, 18 F1 and 176 F2 pigs. The 17-point analysis indicates that F4acR lies between Sw207 and S0283. Recombinant offspring specify that the most probable order is Sw207-S0075-F4acR-Sw225-S0283. We observed six phenotypes for the three fimbrial variants F4ab, F4ac and F4ad. The two missing phenotypes F4abR-/F4acR+/F4adR+ and F4abR-/F4acR+/F4adR- indicate that pigs susceptible to F4ac are always susceptible to F4ab. Furthermore, a weak and a strong adhesion of F4ab and F4ad bacteria was observed. The weak receptor F4abR (F4abRw) was present only in pigs devoid of the receptor F4acR (F4abR+/F4acR-). In contrast, in pigs with the phenotype F4abR+/F4acR+, F4ab bacteria adhered to the majority of enterocytes. F4abRw constitutes a frequently observed phenotype whose inheritance is still unclear. Strong adhesion of F4ab and F4ac bacteria is most likely influenced by the same receptor that we name F4bcR. The number of F4ad bacteria that adhered to enterocytes was very variable in the adhesion test. Moreover, expression of F4adR was independent of age. Our segregation analyses indicated a dominant inheritance of F4adR, although the number of susceptible pigs was smaller than expected. We examined four genes as candidates for the F4acR locus: the transferrin receptor gene (TFRC) and three genes members of the glucosyl/galactosyltransferase family (B3GnT5, B3GALT3 and B4GALT4). Comparison of sequences from resistant and homozygous susceptible F4ac pigs did not reveal any causative single nucleotide polymorphism in the four genes. Two silent mutations at the positions 295 (C/T) and 313 (T/C) in B3GALT3 were found. Using the somatic cell hybrid panel, B3GnT5 and B3GALT3 were assigned to the chromosomal region SSC13q23-q41. No mutations were found in the cDNA sequences of these genes associated with the F4acR genotypes.

Inheritance of porcine receptors for enterotoxigenic Escherichia coli with fimbriae F4ad and their relation to other F4 receptors

“…To test this hypothesis we performed repetitive and targeted matings in which the same pig was mated to different phenotypes (Table 6), for example, sire 2674 was mated to four different resistant dams and sire 2831 was mated to five different dams which were resistant, FA or PA. Dam 2842 was mated to R and FA sires. Although we increased the number of intestinal sites for the adhesion test to four compared with only one site used in previous studies (Python et al, 2002 and2005) it cannot be excluded that we mistyped PA pigs by chance as resistant pigs. A separate χ 2 was calculated in litters with expected FA phenotype to test the two gene inheritance model for the FA receptor.…”

“…A (Python et al, 2005;Yan et al, 2009;Schroyen et al, 2012). Ren et al (2012) showed evidence that MUC13 is a good candidate for the F4ac receptor.…”

“…The two variants of the fimbriae F18 bind to the same host receptor, whereas the three F4 variants F4ab, F4ac and F4ad each exhibit a specific binding pattern including variation in binding strength (Bijlsma et al, 1982;Billey et al, 1998). The fully adhesive receptor(s) for F4ab and F4ac is/are either controlled by one gene (F4bcR) or by two closely linked genes (Python et al, 2005;Yan et al, 2009;Schroyen et al, 2012).…”

“…The PA receptor was found in adult pigs as well. The high standard deviations in the percentage of enterocytes expressing F4adR led to confusion and did not allow any conclusion regarding the mode of inheritance (Python et al, 2005).…”

Detection of quantitative trait loci for porcine susceptibility to enterotoxigenic Escherichia coli F41 in a White Duroc × Chinese Erhualian resource population

“…Susceptibility to E. coli K88ab/ac has been firmly established as a dominant monogenetic trait (Python et al, 2005). In this study, F41 adhesion phenotypes were recorded only for F 2 animals.…”