Identifying genetic markers for nematode resistance in Blackface Scottish Sheep of Scotland

Nematode infections are a major problem in the sheep of Scotland, United Kingdom. There is about £84M/year losses occurring due to parasites in the UK, comprising costs of anthelmintics, labour, pasture and sheep management and production losses. Among nematode parasites, the genus Nematodirus causes heavy losses in the growing lambs particularly 3 to 6 weeks of the ages. It has been hypothesized that the Interferon regulatory factor 3 (IRF3) may be associated with the Nematodirus resistance in sheep. Therefore, the present study was undertaken to characterize the full coding region, as well as the 5’and 3’UTR regions, of the IRF3 gene in Scottish blackface sheep, phenotyped for infestation by Nematodirus. A total of six individuals of blackface sheep with high or low estimated breeding values (EBV) for Nematodirus resistance in the region containing the IRF3 gene were selected for this study. Primers for the IRF3 exons 2, 3 & 4, 5, 6, 7, 8 and the 5’and 3’UTR were designed and amplified from the sheep DNA samples. The PCR products from high EBV and low EBV animals were sequenced and analyzed. IRF3 coding sequence was found to be 1237 bp long, and coded for 412 amino acids. The ORF sequence of the IRF3 was found to be the same as in Texel sheep IRF3. However, there was little difference in the 5’and 3’UTR of the IRF3 gene of high EBV vs. low EBV animals. None of the SNPs were found to be correlated with High EBV vs. Low EBV. It is suggested that if the IRF3 gene is implicated in genetic differences in resistance, then changes in the promoter region may cause up regulation and down regulation of the expression of IRF3 gene which may trigger immune response differences.