Sequence analysis of the prion protein gene (PRNP) in Przewalski's wild horse (Equus przewalskii) and Mongolian horse (Equus caballus).

Prion diseases are a group of human and animal neurodegenerative disorders caused by the deposition of an abnormal isoform prion protein (PrPSc) encoded by a single copy prion protein gene (PRNP). To determine the variability of the PRNP gene in Przewalski’s wild horse (Equus przewalskii) and in the Mongolian horse (Equus caballus), the sequence and polymorphisms of PRNP were analyzed. A total of 22 horse PRNP DNA sequences were found to be distributed in 18 haplotypes. Thirty base substitution sites were found, and nine of these variable sites were neutral substitution sites. Amino acid sequence analysis showed high identity within species and close relation to the PRNP of cat, pig and sheep with 93.8–94.5% identity. Polymorphisms of the open reading frame of PRNP as amino acid substitutions were found at 14 amino acid sites in Przewalski’s wild horse and at eight amino acid sites in Mongolian horse. The polymorphisms of PRNP in both species of horse will be useful in the study of prion disease pathogenesis, resistance and cross species transmission.