Ovine PAPPA2 gene coding variants are linked to decreased fecal egg shedding in native Turkish sheep naturally infected with gastrointestinal nematodes.

In this study, the association between PAPPA2 coding variants and gastrointestinal (GI) nematode fecal egg count (FEC) score in adult Turkish sheep was investigated. For this purpose, the FEC score was determined in adult sheep from six breeds: Karacabey Merino (n = 137), Kivircik (n = 116), Cine capari (n = 109), Karakacan (n = 102), Imroz (n = 73), and Chios (n = 50). Sheep were classified as shedders or non-shedders within breeds and flocks. The first group was the fecal egg shedders (> 50 per gram of feces), and the second group was the no fecal egg shedders (≤ 50 per gram of feces). The exon 1, exon 2, exon 5, exon 7, and a part of 5'UTR of the ovine PAPPA2 gene were genotyped by Sanger sequencing of these two groups. Fourteen synonymous and three non-synonymous single-nucleotide polymorphisms (SNPs) were found. The non-synonymous SNPs, D109N, D391H, and L409R variants, are reported for the first time. Two haplotype blocks were constructed on exon 2 and exon 7. The specific haplotype, C391G424G449T473C515A542 on the exon 2 that carries the 391H variant, was tested against four other common haplotypes. Our results indicate that C391G424G449T473C515A542 haplotype was significantly associated with fecal egg shedding status in adult Turkish sheep (p-value, 0.044).

Documentation of extensive genetic diversity in the Ovar-DRB1 gene in native Turkish sheep.

Indigenous breeds have a high level of genetic diversity that might contribute to develop animal breeds with desired traits such as disease resistance and high productivity. Major histocompatibility complex (MHC) is a key component of adaptive immune system and consists of highly polymorphic genes that take part in adaptive immune response and disease resistance. Exploring and understanding the effect of polymorphisms in MHC could be beneficial to future animal breeding strategies. In this study, we sequenced the highly polymorphic Exon2 of the ovine DRB1 gene using Sanger sequencing to explore the diversity of this gene in six indigenous Turkish sheep breeds and two crossbreeds. In total, 894 haplotypes from 447 sheep were investigated, and 69 different haplotypes including 27 novel ones were identified. Among the identified haplotypes there were common and breed specific haplotypes. There was a relatively high diversity of the alleles within indigenous breeds. Allelic diversity patterns were mostly associated with geographical differences. The results of this study highlight the genetic variation within indigenous breeds which has important implications for biodiversity and the adaptability of breeds to specific environments. There is value to further studies which include other genomic regions and traits, and these could guide breeding strategies.

Association between ovine Toll-like receptor 4 (TLR4) gene coding variants and presence of Eimeria spp. in naturally infected adult Turkish native sheep.

Coccidiosis caused by Eimeria spp. is a protozoan disease prevalent in farm animals, and it is responsible for serious economic losses especially in young animals. It has been popular to breed disease-resistant animals due to the concern about food safety, animal welfare, and public health. Toll-like receptor (TLR) gene family plays a key role in the innate immune system participating in host-antigen interaction, therefore, they are candidate genes for breeding disease-resistant animals. In the present study, possible genetic associations between TLR4 gene coding variants and the presence of Eimeria spp. in adult Turkish sheep were investigated. For this purpose, the presence of Eimeria spp. in fecal samples from six native Turkish sheep were determined, and approximately 1450 bp region in the 3rd exon of the ovine TLR4 gene was sequenced. Ten nonsynonymous and four synonymous single nucleotide polymorphisms (SNPs) were detected in the targeted region. Statistical analyses revealed that the SNP at the codon at 356th position encoding Leucine instead of Phenylalanine (F356L) was significantly associated with the presence of Eimeria spp. It was found that the individuals carrying at least one Leucine amino acid sequence at this position have 2.3-fold more risk for the presence of Eimeria spp.

Detecting fecal egg count (FEC) for gastrointestinal nematodes of adult Turkish sheep with different scrapie related PRNP haplotypes.

Scrapie is a transmissible spongiform encephalopathy caused by prions and leads to neurodegeneration in the Central Nervous System (CNS) of sheep and goats. Genetic resistance/susceptibility to scrapie is well studied and it is known that the variations of 136th, 154th and 171st codons at the ovine PRNP gene have a major effect on the development of the disease. Many studies demonstrated that selection for PRNP genotypes has not influenced other performance traits, nevertheless, there is a knowledge gap about the possible link between the PRNP gene and the status of the other important diseases that affect the sheep population worldwide. In the present study, we tested whether there is an association between scrapie-related PRNP genotypes and fecal egg count (FEC) of gastrointestinal nematodes in seven adult Turkish sheep breeds. For this purpose, FEC scores of studied sheep (n = 253) were determined and the same animals were genotyped for the PRNP gene. Finally, an association analysis was performed for scrapie resistant (ARR), susceptible (VRQ), and wild-type (ARQ) haplotypes. Based on our statistical analysis, it is concluded that PRNP genotypes have no positive or negative effect on the FEC scores of adult sheep.

Evaluation of CD109, PCP4 and SEMA3D genes for their association with Ovine Johne's disease in Turkish sheep.

Johne's disease is a chronic, contagious, zoonotic disease that affects numerous species including livestock and sometimes humans. The disease is globally distributed in sheep populations and caused by Mycobacterium avium Subsp. paratuberculosis (MAP). A previous genome-wide association study identified single nucleotide polymorphism (SNP) markers associated with OJD serostatus in CD109, PCP4, and SEMA3D genes. Our aim was to evaluate the same markers for association with OJD seroprevalence in Turkish sheep in a retrospective matched case-control study. The serological status for OJD in 1801 sheep was determined for four native and four composite breeds from three research flocks. One hundred eleven matched case-control pairs were constructed according to breed type and age from 1750 comingled ewes reared in the same environment. A Single Nucleotide Primer Extension (SNuPE) assay was designed to genotype PCP4-Intron 1, PCP4-3'UTR, SEMA3D, CD109-intron 2 and CD109-intron 8 markers and a McNemar's test was performed on the matched pairs. An association with these five markers was not detected with the OJD serostatus in Turkish sheep (power of detection, 0.95; odds ratio >3; McNemar's p < .05). Thus, a wider search may be needed to identify any major underlying genetic risk factors for OJD in Turkish sheep.

Association of TLR2 haplotypes encoding Q650 with reduced susceptibility to ovine Johne's disease in Turkish sheep.

Ovine Johne's disease (OJD) is caused by Mycobacterium avium subsp. paratuberculosis (MAP) and carries a potential zoonotic risk for humans. Selective breeding strategies for reduced OJD susceptibility would be welcome tools in disease eradication efforts, if available. The Toll-like receptor 2 gene (TLR2) plays an important signaling role in immune response to MAP, and missense variants are associated with mycobacterial infections in mammals. Our aim was to identify and evaluate ovine TLR2 missense variants for association with OJD in Turkish sheep. Eleven TLR2 missense variants and 17 haplotype configurations were identified in genomic sequences of 221 sheep from 61 globally-distributed breeds. The five most frequent haplotypes were tested for OJD association in 102 matched pairs of infected and uninfected ewes identified in 2257 Turkish sheep. Ewes with one or two copies of TLR2 haplotypes encoding glutamine (Q) at position 650 (Q650) in the Tir domain were 6.6-fold more likely to be uninfected compared to ewes with arginine (R650) at that position (CI95 = 2.6 to 16.9, p-value = 3.7 × 10-6). The protective TLR2 Q650 allele was present in at least 25% of breeds tested and thus may facilitate selective breeding for sheep with reduced susceptibility to OJD.

A novel 2 bp deletion variant in Ovine-DRB1 gene is associated with increased Visna/maedi susceptibility in Turkish sheep.

Visna/maedi (VM) is a multisystemic lentivirus infection of sheep that affecting sheep industry across the globe. TMEM154 gene has been identified to be a major VM-associated host gene, nevertheless, a recent study showed that the frequency of the VM-resistant TMEM154 haplotypes was very low or absent in indigenous sheep. Thus, the present study was designed to determine other possible co-receptors associated with VM. For this purpose, DRB1 gene, which is renowned for its role in host immune response against various diseases was targeted. A total number of 151 case-control matched pairs were constructed from 2266 serologically tested sheep. A broad range of DRB1 haplotype diversity was detected by sequence-based genotyping. Moreover, a novel 2 bp deletion (del) in the DRB1 intron 1 was identified. For the final statistic, the sheep carrying VM-resistant TMEM154 diplotypes were removed and a McNemar's test with a matched pairs experimental design was conducted. Consequently, it was identified for the first time that the 2 bp del variant is a genetic risk factor for VM (p value 0.002; chi-square 8.31; odds ratio 2.9; statistical power 0.90) in the dominant model. Thus, negative selection for 2 bp del variant could decrease VM infection risk in Turkish sheep.