Association and expression analyses of the Ucp2 and Ucp3 gene polymorphisms with body measurement and meat quality traits in Qinchuan cattle.

The uncoupling proteins (UCPs) belong to the mitochondrial inner membrane anion carrier superfamily and play an important role in energy homeostasis. Genetic studies have demonstrated that Ucp2 and Ucp3 gene variants are involved in obesity and metabolic syndrome. The aim of this study was to identify associations between polymorphisms of Ucp2 and Ucp3 genes and economically-important traits in Qinchuan cattle. In the present study, one single-nucleotide polymorphism (SNP) in the 5'UTR region (SNP1:g.C-754G) of the Ucp2 gene was identified by direct sequencing of 441 Qinchuan cattle. Two SNPs in exon 3 (SNP2: g.G4877A: SNP3: g.C4902T) of the Ucp3 gene were identified by sequencing and polymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP) among 441 Qinchuan cattle. Association analysis showed that SNP1 and SNP2 were associated with the meat quality traits (MQTs) including back fat thickness, loin muscle area and intramuscular fat content. SNP3 was found to be associated with part of the body measurement traits (BMTs) which referred to withers height and chest depth. In addition, QTL pyramiding analysis showed that individuals with diplotype P3P3 (GG-GG-CC) exhibited the best performance in terms of back fat thickness, loin muscle area, intramuscular fat content, rump length, hip width, chest depth and chest circumference. With regard to the G4877A mutation, real time PCR analysis revealed that individuals with AA genotype of the Ucp3 gene expressed higher mRNA levels than those with GG genotype. These results suggest that the diplotype P3P3 (GG-GG-CC) could be used as a molecular marker of the combined genotypes for future selection of body measurement traits and meat quality traits in Qinchuan cattle.