ABSTRACT
The aim of this study was to identify the PRNP polymorphisms outside the standard codons 136, 154 and 171 in 1110 sheep with no clinical sign of scrapie from all 18 Turkish native sheep breeds and compare our results with published data on ovine PRNP polymorphism from other regions of the world. Among the 22 amino acid polymorphisms and three silent mutations, 10 were novel for ovine PRNP: p.Gly94Gly, p.Leu128Ile, p.Met132Leu, p.Ser135Arg, p.Met137Val, p.Asn146Lys, p.Arg159Arg, p.Tyr160Asn, p.Gln163His and p.Thr193Ser. These data reveal that sheep breeds close to the historic center of small ruminant domestication have remained highly diverse in the prion gene locus, with distinctive genetic similarities to both Asian and European sheep breeds.
Subject(s)
Polymorphism, Genetic , Prions/genetics , Sheep, Domestic/genetics , Amino Acids/genetics , Animals , Prions/metabolism , Sheep, Domestic/classification , Sheep, Domestic/metabolism , TurkeyABSTRACT
The aim of this study was to identify the prion protein (PrP) gene polymorphism in a total of 1,110 healthy sheep from 18 Turkish native sheep breeds. There were nine alleles and 22 genotypes observed based on codons 136, 154, and 171 of the PrP gene. The ARQ allele was predominant for all breeds. The most resistant allele to scrapie, ARR, was present in all breeds. The VRQ allele, associated with the highest susceptibility to scrapie, was detected at low frequencies in Ivesi (0.06), Kivircik (0.021), Sakiz (0.010), Karayaka (0.011), Çine Çapari (0.012), and Güneykaraman (0.017). In general, the ARQ/ARQ genotype was predominant in all breeds. The most resistant genotype to scrapie, ARR/ARR, was found with the frequency lower than 0.180. The most susceptible genotype, VRQ/VRQ, was found in only Kivircik. The TRR and TRH alleles and the genotypes of ARR/TRR, ARR/ARK, and ARH/TRH have been found for the first time in Turkish native sheep breeds. According to these results, all breeds belong to risk group R3 followed by R2. It is propounded that the susceptibility to scrapie increased from eastern to western part of Turkey. Our findings of Turkish native sheep breeds with PrP gene polymorphisms will assist the sheep breeding program for selection of scrapie resistance genotypes to reduce the risk of scrapie.
Subject(s)
Genetic Predisposition to Disease , Polymorphism, Genetic , Prions/genetics , Scrapie/genetics , Sheep, Domestic/genetics , Alleles , Animals , Breeding , Gene Frequency , Genotype , Molecular Sequence Data , Prions/pathogenicity , Scrapie/prevention & control , Sequence Analysis, DNA , Sheep, Domestic/metabolism , TurkeyABSTRACT
Marek's disease (MD) is a T cell lymphoma disease of domestic chickens induced by the Marek's disease virus (MDV), a highly infectious and naturally oncogenic alphaherpesvirus. Enhancing genetic resistance to MD in poultry is an attractive method to augment MD vaccines, which protect against MD but do not prevent MDV replication and horizontal spread. Previous work integrating QTL scans, transcript profiling, and MDV-chicken protein-protein interaction screens revealed 3 MD resistance genes; however, a major challenge continues to be the identification of the other contributing genes. To aid in this search, we screened for allele-specific expression (ASE) in response to MDV infection, a simple and novel method for identifying polymorphic cis-acting regulatory elements, which may contain strong candidate genes with specific alleles that confer MD genetic resistance. In this initial study, we focused on immunoglobulin ß (CD79B) because it plays a critical role in the immune response and, more important, is transcriptionally coupled with growth hormone (GH1), one of the previously identified MD resistance genes. Using a coding SNP in CD79B and pyrosequencing to track the relative expression of each allele, we monitored ASE in uninfected and MDV-infected F(1) progeny from reciprocal intermatings of highly inbred chicken lines 6(3) (MD resistant) and 7(2) (MD susceptible). Upon screening 3 tissues (bursa, thymus, and spleen) at 5 time points (1, 4, 7, 11, and 15 d postinfection), we observed that MDV infection alters the CD79B allelic ratios in bursa and thymus tissues at 4 and 15 d postinfection in both mating directions. Our results suggest that CD79B has a cis-acting regulatory element that responds to MDV infection and probably cooperates with GH1 in conferring genetic resistance to MD. This result helps validates the use of ASE screens to identify specific candidate genes for complex traits such as genetic resistance to MD.
