Relationship between the insertion/deletion polymorphism within the promoter and the intron 1 sequence of the PRNP gene and milk performance traits in cattle

摘要

Current studies on the prion protein ( PRNP ) gene polymorphism focus primarily on the causative mutations that influence BSE susceptibility in cattle. The specific genetic structure determined by the insertion/deletion ( indel ) polymorphism within the 23 bp promoter sequence and the 12 bp intron 1 sequence of the PRNP gene, and its genomic location suggest that this polymorphism can be a potential QTL marker. The objective of the present study was to determine whether the indel polymorphism within the promoter sequence (23 bp) and the intron 1 sequence (12 bp) of the PRNP gene can be used as a factor differentiating the values of milk performance traits. The experimental materials comprised 285 primiparous Polish Holstein-Friesian cows, daughters of two dihybrid (23 ins -12i ns /23 del -12 del ) sires (progeny of sire 1 – 149 cows, progeny of sire 2 – 136 cows). The following milk performance traits were analysed: milk yield, milk fat yield, milk protein yield, fat and protein contents of milk during the first 305-day lactation. The polymorphism in the promoter region (23 bp) was found to have a significant ( P = 0.040) effect on protein yield and a highly significant ( P = 0.007) effect on the protein content of milk. The highest values of these traits were noted in 23 ins/del heterozygotes and the lowest in 23 del/del homozygotes. There was an interrelation between diplotype variants and the concentrations of milk components. The protein content of milk was highly significantly ( P = 0.007) higher in 23 ins -12 ins /23 del -12 del heterozygotes and significantly ( P = 0.028) higher in 23 ins -12 ins /23 ins -12 ins homozygotes, compared to 23 del -12 ins /23 del -12 del cows. 23 ins -12 ins /23 del -12 del heterozygotes were also characterized by a significantly ( P = 0.046) higher fat content of milk, in comparison with 23 del -12 del /23 del -12 del homozygotes.