Effect of tumor necrosis factor alpha locus on biometric traits of Makoei sheep

Tumor Necrosis Factor Alpha (TNFα) is a proinflammatory cytokine that plays critical roles in the regulation of immune responses including macrophages activity and apoptosis. In the present study, polymorphism of TNFα gene in Makoei sheep was investigated and its association with biometric traits was analyzed. Genomic DNA of 90 sheep was extracted from blood. A 273bp fragment in the regions of the exon 4 and 3´ un-translated region (3´ UTR) was amplified by standard PCR, using locus-specific primer. The single stranded conformation polymorphism (SSCP) of PCR products were studied using 8% Polyacrilamid gel and silver staining method. Finally, three genotypes EE, OE and RE were obtained with frequencies of 0.4667, 0.3556 and 0.1777, respectively. The frequencies of E, O and R alleles were calculated as 0.7333, 0.1778 and 0.0889, respectively. The chi-square test showed significant deviation from Hardy-Weinberg equilibrium for this locus in studied population (P<0.05). The evaluation of association between genotypes with body length, heart girth, height at withers, height at back and leg girth using a GLM procedure of SAS program, showed a significant association between TNFα genotypes with leg girth (P<0.05). The genotype of EE had a superior leg girth (35.76±0.6 cm) than the other genotypes. These results suggest that polymorphism at TNFα gene may be as a potential genetic marker to improve growth related traits in sheep breeding programs. Further studies with various markers and breeds will be needed in order to clarify the genetic background for immunological influences on growth traits.