Allelic variation of ovine MHC class II DQA1 and DQA2 genes

✍ Scribed by K. J. Snibson; J. F. Maddox; S. A. Fabb; M. R. Brandon

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 597 KB
• Volume: 29
• Category: Article
• ISSN: 0268-9146
• DOI: 10.1046/j.1365-2052.1998.295351.x

✦ Synopsis

In the present study we characterize allelic variation of polymorphic OLA‐DQA1 and OLA‐DQA2 genes in sheep. To achieve this, PCR primers were designed to independently amplify the second exons of OLA‐DQA1 and OLA‐DQA2 genes. Single strand conformation polymorphism (SSCP) gel analyses reveals that there are at least 12 distinct OLA‐DQA2 sequences, 10 of which have been characterized by sequencing. Six distinct OLA‐DQA1 alleles have been sequenced in sheep and we can detect at least seven DQA1 alleles, including a null allele, by SSCP analysis. The second exon of the OLA‐DQA2 gene is more polymorphic than the equivalent region of the OLA‐DQA1 gene. Thirty‐two per cent of nucleotide and 49% of amino acid sites showed variation at the DQA2 locus, compared to 20% of nucleotide and 33% of amino acid sites for DQA1. Phylogenetic analysis of DQA sequences from a number of species show that sheep DQA1 sequences group together and are more similar to bovine DQA1 sequences than to sheep DQA2 alleles. The majority of OLA‐DQA2 sequences are on the same main branch of the phylogenetic tree as bovine DQA2 sequences. However, three sheep DQA2 sequences have a tendency to group with putative bovine DQA3 sequences rather than to other ovine DQA2 alleles. A variety of SSCP gel conditions were tried in order to develop a typing system for the OLA‐DQA2 gene. We describe a set of PCR and SSCP conditions which distinguish between all known OLA‐DQA2 alleles.