First report of novel single nucleotide polymorphisms (SNPs) and genetic characteristics of the prion-like protein gene (PRND) in cynomolgus monkeys.

Transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative diseases caused by misfolded prion protein. The prion-like protein (Doppel), encoded by the prion-like protein gene (PRND), is linked to neurodegeneration and TSE susceptibility. While PRND polymorphisms have been studied in various species, their genetic features in non-human primates remain unexplored. Cynomolgus monkeys (Macaca fascicularis), which are genetically close to humans, are a valuable model to study the role of PRND polymorphisms in prion disease susceptibility. We performed polymerase chain reaction (PCR) to amplify the monkey PRND gene and investigated genetic polymorphisms in cynomolgus monkeys (n = 121). Genotype, allele, and haplotype frequencies, as well as linkage disequilibrium (LD), were analyzed to assess the genetic architecture of the population using Haploview (v4.2). Monkey PRND amino acid sequences were compared with those of several species using ClustalW. The effects of non-synonymous SNPs and the structural analysis of monkey Doppel were evaluated using in silico tools. We identified 15 novel genetic polymorphisms in the monkey PRND gene, including 12 variants located within the open reading frame (ORF), one in the upstream region, and two in the downstream region. In addition, LD analysis revealed several strong LD relationships among PRND polymorphisms in monkeys. ClustalW analysis showed that humans and monkeys shared the same PRND sequence length and exhibited high sequence homology. In silico analyses demonstrated that the non-synonymous SNPs, c.61C>T (L21F) and c.370G>C (D124H), were predicted to have damaging effects. This is the first report on the genetic and structural features of PRND polymorphisms in monkeys, showing that several non-synonymous amino acid substitutions may affect the structural stability of monkey Doppel proteins.