Isolation, sequence characterization, expression pattern analysis of porcine Pitx2c gene

Pitx2 is a bicoid-related homeobox gene, which has been demonstrated to play a critical role in muscle cell proliferation and muscle formation. However, the molecular characteristics of Pitx2c in pigs have not been investigated. In the present study, 2316 bp full-length cDNA of porcine Pitx2c, which contains a 981 bp open reading frame (ORF) encoding 326 amino acids, was isolated. Multiple sequence alignment results showed that porcine Pitx2c full-length cDNA and Pitx2c protein sequences were highly conserved, sharing 91.80% and 86.58% nucleotide identities to human and mouse Pitx2c respectively, while amino acid identities reached 99.11% and 97.03% respectively. However, the identities are relatively lower compared with other isoforms, and phylogenic analysis also indicated that Pitx2c was distinguished from other isoforms. The Pitx2a, Pitx2b and Pitx2c were formed three independent branches respectively. Furthermore, we examined the expression levels and distribution of porcine Pitx2c in different tissues using semi-quantitative RT-PCR method and the result proved that it was most highly expressed in the skeletal muscle. In addition, real-time quantitative PCR was employed to assay the expression patterns of porcine Pitx2c in muscle development. Our results showed that porcine Pitx2c was expressed higher in Yorkshire pigs than that in Meishan and the expression levels were remarkably different at 60 d and 120 d (P < 0.05). Further analysis indicated that Pitx2c expression was up-regulated from 3 d to 120 d reaching its peak at 120 d, thereafter down-regulated from 120 d to 180 d and Pitx2c expression levels at 120 d were significantly higher than other stages except at 150 d (P < 0.05). While the data of Pitx2c expression in different muscles revealed that its expression levels in biceps femoris were obviously higher as compared with soleus, masseter and semitendinosus (P < 0.05). Taken together, our data provide fundamental evidence for Pitx2c as a functional candidate gene affecting pig meat quality.