engleski

Sequencing of prion protein gene (PRNP) in East Adriatic sheep populations revealed new nonsynonymous polymorphisms linked to ARQ allele

Polymorphisms of PRNP are known for scrapie susceptibility in sheep populations. The genotypes of 780 sheep, sampled along all Eastern Adriatic, were determined for a 628 bp long fragment in PrP exon 3 gene. In the scrapie susceptible locus (codons 136-154-171), alleles ARQ (0.566±0.013), ARR (0.260±0.012), AHQ (0.106±0.008), VRQ (0.057±0.006), ARH (0.011±0.003) and ARK (0.001±0.001) were found. Overall, the frequencies of ARR/ARR, VRQ/VRQ and ARQ/VRQ were 0.097±0.007, 0.051±0.002 and 0.064±0.003, respectively. We also observed three new non-synonymous alleles caused by mutations at codons 145 (G145GGC→V145GTC), 160 (Y160TAC→D160GAC) and 185 (I185ATC→T185ACC) as well as at previously reported mutations at codons 101 (Q101CAG→R101CGG), 112 (M112ATG→T112ACG), 127 (G127GGC→S127AGC), 137 (M137ATG→T137ACG), 141 (L141CTT→F141TTT), 143 (H143CAT→R143CGT), 175 (Q175CAG→Q175CAA), 180 (H180CAT→Y180TAT), 231 (R231AGG→R231CGG) and 237 (L237CTC→L237CTG). The most frequent were alleles R231CGG (0.159), L237CTG (0.159) and T112ACG (0.041), while other mutations were rare (<0.040). All three new mutations were confirmed by cloning. Linkage disequilibrium, composite genotypes and cloning suggested that additional non-synonymous polymorphisms are linked only to ARQ allele. Thus, decrease of ARQ alleles would lead to elimination of non-synonymous variability at PRNP (exon 3) which potentially might be beneficial.

PRNP; East Adriatic sheep; nonsynonymous polymorphisms; ARQ

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