Genetic variation of the prion protein gene (PRNP) in alpaca (Vicugna pacos)

• Sequence determination of the alpaca prion protein gene (PRNP) open reading frame.
• PRNP length polymorphisms and heterozygosity exist within the alpaca population.
• High (> 87%) PRNP sequence homology when compared to that of TSE-susceptible species.

Transmissible spongiform encephalopathies (TSE) are caused by accumulation of a misfolded form of the prion protein (PrP). The normal cellular isoform of PrP is produced by the prion gene (PRNP) and is highly expressed in the central nervous system. Currently, there is an absence of information regarding the genetic sequence of alpaca PRNP and the potential susceptibility of this species to TSE. The objective of this study was to sequence the open reading frame of the alpaca prion gene and analyze this sequence for variation within the alpaca population and for homology to TSE-susceptible species. We sequenced the open reading frame of the prion gene of 40 alpacas of Huacaya or Suri descent. Length polymorphisms were identified within the sampled population. A subset (15%) of animals contained an additional 24 base pairs within the putative octapeptide repeat region. This polymorphism was independent of breed and sex. The majority (52.5%) of animals were heterozygous, possessing both longer and shorter alleles. Comparison with proven TSE-susceptible species (sheep, cattle, deer) revealed the following amino acid sequence variations: I6M, A16V, M17T, G92del, Q95_G96insG, N111S, R167K, N/T177S, I206V, S225Y, Y228S, Q230G, and L237del. Sequence alignment showed high homology compared to camel (> 95%), sheep (> 88%), cattle (> 87%) and deer (> 88%) PRNP sequence. This study demonstrates intraspecies variability within the PRNP open reading frame in alpacas and overall high sequence homology to TSE-susceptible species, providing foundational data for further research on the potential susceptibility of alpacas to TSE.