PRNP gene variation in Pakistani cattle and buffaloes

Abstract

Bovine spongiform encephalopathy (BSE) is a neurodegenerative prion protein misfolding disorder of cattle. BSE is of two types, classical BSE and atypical BSE which in turn is of two types, H-type BSE and L-type BSE. Both H-type BSE and L-type BSE are primarily sporadic prion disorders. However, one case of H-type BSE has recently been associated with E211K polymorphism in the prion protein gene (PRNP). Two polymorphisms in the bovine PRNP are also associated with susceptibility to classical BSE: a 23bp insertion/deletion (indel) in the PRNP promoter region and a 12bp indel in the first intron. No information regarding BSE susceptibility in Pakistani cattle is available. The present study aimed at achieving this information. A total of 236 cattle from 7 breeds and 281 buffaloes from 5 breeds were screened for E211K polymorphism and 23bp and 12bp indels employing triplex PCR. The E211K polymorphism was not detected in any of the animals studied. The 23bp insertion allele was underrepresented in studied cattle breeds while the 12bp insertion allele was overrepresented. Both 23bp and 12bp insertion alleles were overrepresented in studied buffalo breeds. Almost 90% of alleles were insertion alleles across all studied buffalo breeds. The average frequency of 23bp and 12bp insertion alleles across all studied cattle breeds was found to be 0.1822 and 0.9407, respectively. There were significant differences between Pakistani and worldwide cattle in terms of allele, genotype and haplotype frequencies of 23bp and 12bp indels. The higher observed frequency of 12bp insertion allele suggests that Pakistani cattle are relatively more resistant to classical BSE than European cattle. However, the key risk factor for classical BSE is the dietary exposure of cattle to contaminated feedstuffs.