The PCR typing of MHC‐DRB genes in the sheep using primers for an intronic microsatellite: Application to nematode parasite resistance

Abstract

SummaryThe strong association between polymorphisms in an intronic microsatellite and the coding sequences for (BoLA)-/)/^5i genes, previously described for demonstrating alleles of class II major histocompatibility complex (MHC) in the cow, was examined in sheep to see if similar polymorphisms could be demonstrated in the DRB region of the MHC. The bovine primers LA53 and LA54, previously used to amplify the bovine DRB3 microsatellites. were used with DNA from Australian sheep, eight DRB alleles were identified by length polymorphisms of poiymerase chain reaction (PCR) products amplified from the DRB microsatellite region. Incomplete amplification of both aileles was sometimes found for sheep DNA samples using bovine primers, so a modified primer (LA53b) was used, and found to amplify the microsatellite next to intron 2 of the MHC more reliably than the LA53 primer. Two additional primers {LA31 and LA32), used in amplification of the exon 2 region of bovine DRB3, were used in the sheep, and the PCR products were analysed by single-stranded conformation polymorphism (SSCP). These primers successfully amplified the variable region of the ovine DRB region coded by exon 2, and the SSCP technique demonstrated polymorphisms with sheep DNA. Family studies demonstrated the segregation of alleles, by amplification both of intronic microsatellites and of the exon 2 variable region. Close correspondence was found between the two regions for several alleles. suggesting that the intronic microsatellites were closely linked to DRB-\av\ab\e region alleles. Three families of Merino sheep with ditferent antibody responses to intestinal nematode parasites were examined. The sire group with the highest antibody levels possessed two mierosatellite alleles of closely similar length (alleles 3 and 4) inherited from the sire and present in high frequency in the lambs. In contrast, the other two sires did not possess these two alleles and the alleles were in low frequency in their progeny. Further studies are required in unrelated sheep to confirm whether these two alleles are associated with resistance to nematode parasites.

The distribution of SNP marker effects for faecal worm egg count in sheep, and the feasibility of using these markers to predict genetic merit for resistance to worm infections

“…Thus, replicating results in a second family where the polymorphism is not segregating is not possible. Polymorphisms may not be segregating in families due to low allele frequencies in the breed, or because the polymorphism is (Schwaiger et al, 1995 ;Outteridge et al, 1996;Paterson et al, 1998 ;Coltman et al, 2001 ;Patterson et al, 2001;Davies et al, 2006). However, this study found no validated SNP in these regions.…”

Microsatellite-based genotyping of MHC class II DRB1 gene in Iberian and Alpine ibex

“…In humans and Rhesus macaques, genotyping of large samples resulted in the definition of DRB-STR patterns that were characteristic for a certain haplotype (Doxiadis et al 2007). Associations between polymorphisms in an intronic microsatellite and the coding sequences for class II MHC genes were also reported in bovids (e.g., Sigurdardottir et al 1991;Ellegren et al 1993) and domestic and wild sheep (Schwaiger et al 1993;Outteridge et al 1996;Paterson 1998). To our knowledge, it has not yet been investigated whether similar patterns hold true in wild goats (genus Capra).…”

Quantitative trait loci associated with parasitic infection in Scottish blackface sheep

“…The primary immunological function of MHC molecules is to bind and 'present' antigenic peptides on the surfaces of cells for recognition by the antigen-specific T-cell receptors of lymphocytes. Several studies including Buitkamp et al (1996), Outteridge et al (1996), Paterson et al (1998) and Charon et al (2002) have implicated both regions of the MHC as QTL for nematode resistance. Schwaiger et al (1995) reported a QTL close to DRB1 in Scottish Blackface sheep facing a T. circumcincta natural challenge.…”