Absence of proteinase K-resistant PrP in Korean Holstein cattle carrying potential bovine spongiform encephalopathy-related E211K somatic mutation

Bovine spongiform encephalopathy (BSE) is a kind of prion disease caused by proteinase K-resistant prion protein (PrP^Sc) in cattle. Although BSE has been reported worldwide, BSE-infected cases have never been reported in Korea. In a previous study, we identified BSE-related somatic mutation E211K in 3 Korean Holstein cattle. In Korea, the BSE surveillance system has been established. However, several genetic factors have not been controlled simultaneously thus far. In the present study, we performed enhanced surveillance of prion disease-related factors in Korean cattle, including Holstein cattle and Hanwoo (Korean native cattle), which is widely raised for meat. We investigated the germline mutation E211K at codon 211 of the PRNP gene and analysed genotype, allele and haplotype frequencies of the 23- and 12-bp insertion/deletion polymorphisms of the PRNP gene using direct DNA sequencing. In addition, we investigated linkage disequilibrium (LD) and compared haplotype distributions of polymorphisms among cattle breeds. Furthermore, we carried out BSE diagnosis in the medulla oblongata (MO) of Korean cattle including 3 Korean Holstein cattle carrying somatic mutation E211K using Western blotting analysis. We did not find the E211K mutation in the PRNP gene in any of the Korean cattle and found significantly different genotype, allele and haplotype distributions of the 23- and 12-bp insertion/deletion polymorphisms of the PRNP gene in male Holstein compared with male Hanwoo, female Hanwoo and total Hanwoo. In addition, only male Holstein showed weak LD between 23- and 12-bp insertion/deletion polymorphisms. Furthermore, the PrP^Sc bands were not detected in all Korean cattle tested. To the best of our knowledge, the enhanced surveillance system of BSE was conducted for the first time in Korean cattle.