Molecular characterization, expression patterns and polymorphism analysis of porcine Six1 gene.

Six1 belongs to the Six gene family that includes six members in mammals (from Six1 to Six6). It has been demonstrated that Six1 homeodomain transcription factor is implicated in myogenesis. However, the molecular characteristics of Six1 in pigs have not been reported. In this study, we isolated and characterized the porcine Six1 gene full-length cDNA, genomic DNA and proximal promoter sequence. Semi-quantitative RT-PCR results confirmed that porcine Six1 was highly expressed in skeletal muscle. Real-time quantitative PCR results showed that porcine Six1 was highly expressed in embryonic stage and no significant expression differences is observed between Meishan and Yorkshire pigs. Furthermore, Six1 expression was significantly different among different developmental stages in Yorkshire pigs and the expression trend was up-regulated from 3 days to 180 days, reaching its highest expression level at 180 days. In addition, the data of Six1 expression in different muscles demonstrated that Six1 was a fast-twitch muscle high expression gene. PCR-HindII-RFLP was established to detect a C/T mutation and an A/G mutation which were present in promoter and intron, respectively. Meanwhile, their associations with economic traits were assessed in Meishan × Yorkshire F2 reference family. The statistical results revealed that the two HindII polymorphisms of porcine Six1 had significant associations with several meat quality traits (P<0.05). Taken together, these studies suggest that porcine Six1 may play an important role in skeletal muscle growth and meat quality.