The first report of genetic variations in the chicken prion protein gene.

Abnormal structural changes of the prion protein (PrP) are the cause of prion disease in a wide range of mammals. However, spontaneous infected cases have not been reported in chicken. Genetic variations of the prion protein gene (PRNP) may impact susceptibility to prion disease but have not been investigated thus far. Because an investigation of the chicken PRNP can improve the understanding of characteristics related to resistance to prion disease, research on the chicken PRNP is highly desirable. In this study, we investigated the genetic characteristics of the chicken PRNP gene. For this, we performed direct sequencing in 106 Dekalb White chickens and analyzed the genotype and allele frequencies of chicken PRNP gene. We found two insertion and deletion polymorphisms in the chicken PRNP: c.163_180delAACCCAGGGTACCCCCAT and c.268_269insC. The former is a U2 hexapeptide deletion polymorphism. Of the 106 samples, 13 (12.26%) were insertion homozygotes, 89 (83.96%) were heterozygotes, and 4 (3.77%) were deletion homozygotes in c.163_180delAACCCAGGGTACCCCCAT. In the c.268_269insC polymorphism, 102 (96.23%) were deletion homozygotes, and 4 (3.77%) were heterozygotes. Insertion homozygotes of c.268_269insC were not detected. Two polymorphisms were in perfect linkage disequilibrium (LD) with a D' value of 1.0, and three haplotypes were identified. Furthermore, PROVEAN evaluates 163_180delAACCCAGGGTACCCCCAT as 'deleterious' with a score of - 13.173. Furthermore, single nucleotide polymorphisms (SNPs) in the open reading frame (ORF) of the PRNP gene were not found in the chicken. To the best of our knowledge, this was the first report on the genetic variations of the chicken PRNP gene.