STAT5 gene (6853C>T) polymorphism and its influence on the carcass quality in beef cattle

Abstract

Signal transducer and activator of transcription 5 (STAT5) is known as a main mediator of growth hormone (GH) action on target genes [1]. The STAT5 transcription factors are members of the somatotropic axis. They initiate the growth process in the target cells, a process mediated by the pituitary growth hormone [2]. Owing to its mediator role in the effects of the prolactin and growth hormones, it is suggested that the STAT5A gene is a potential quantitative trait locus for the quantitative traits of livestock, such as meat yield [3, 4]. The aim of this study was to investigate the prevalence of STAT5 gene (6853C>T) polymorphism and to determine its influence on the carcass quality in beef cattle. Samples of cattle hair follicles were collected from 85 bulls consisting of Angus (41), Limousin (19), Galloway (19) and Simmental (6) cattle. Hair samples and the data on carcass quality records were obtained from Šilutė control bulls feeding station. Bovine genomic DNA was extracted from hair follicles using Chelex DNA extraction method. Polymorphism of STAT5 locus was identified using a PCR-RFLP method. PCR product of STAT5 gene was digested with AvaI (Eco88I) restriction nuclease. Both C and T alleles of the STAT5 gene were detected in Lithuanian beef cattle population. Frequency of C allele was found the highest and that of T allele the lowest. The C and T allele frequencies were 0.959 and 0.041, respectively. The STAT5 gene CC genotype was the most common in the studied population (91–92%) followed by the CT genotype (9–8%), while the TT genotype was not found in the analyzed population. Evaluation of the observed and expected heterozygosity in the investigated group of animals demonstrated that the observed heterozygosity was found to be lower than expected, indicating an insufficient amount of genetic diversity in the loci studied; the difference was not statistically significant. According to SEUROP carcass classification system, most of the CT and CC genotypes bovine carcasses were classified as R (good) carcass conformation class and the 3rd (average) fat coverage class. However, results were not statistically significant (P value – 0.334, P > 0.05); thus, STAT5 gene polymorphism has no influence on bovine carcass conformation and fat coverage. In conclusion, after evaluating the polymorphism of the STAT5 gene (6853C> T) in the studied population of beef bulls bred in Lithuania, it was found that the frequencies of alleles and genotypes are unevenly distributed. Therefore, the low frequency of some of the obtained genotypes of polymorphism makes it difficult to determine the influence on the carcass quality traits of cattle. An increased sample size is required to obtain more confident results.