Characterization and evolution analysis of Wt1 and StAR genes in Andrias davidianus

Wt1 and StAR are two multifunctional genes that play an important role in sexual differentiation, especially in development of testicles and spermatogenesis, but the studies of amphibians are rare. In this study, we have cloned and characterized the complete cDNA of Wt1 and StAR in Andrias davidianus. The Wt1 has two isoforms, encoding 416 aa or 419 aa protein with a conserved zinc finger structure region. The StAR encodes 287 aa protein with a conserved domain containing putative lipid binding sites. The two genes showed high homology among amphibians by phylogenetic analysis. Molecular evolution analysis indicated that Wt1 gene underwent positive selection, while StAR gene showed no positive selection. Tissue expression patterns revealed that Wt1 expression was higher in liver, moderate in testis and kidney, low in the rest of the tissues, while StAR expression was higher in testis, moderate in kidney and brain, low in the rest of the tissues. Moreover, compared to female and reversal-female, Wt1 and StAR both showed higher expression level in male and reversal-male. Our results suggest the important role of Wt1 and StAR in sexual development of Andrias davidianus, and also provide information for functional study of amphibian Wt1 and StAR.