Identification and expression of Dmrt1 and Sox9 during the gonadal differentiation of Rana chensinensis

Gonadal sex differentiation proceeds by the interplay of various genes including the transcription factors and secretory factors in a complex network. Dmrt1 and Sox9 were considered to be the essential genes involved in the testicular differentiation in mammals, birds, reptiles, and fishes. Here, we have successfully isolated and characterized cDNAs encoding the Rana chensinensis orthologs of Dmrt1 and Sox9, and we have determined patterns of expression during gonadal differentiation and adult tissues. At the molecular level, a clear sexual dimorphism of rcDmrt1 and rcSox9 was observed in the gonad-mesonephros complex or gonads of tadpoles during stages 26-46. The rcDmrt1 transcript was first detected in undifferentiated gonads at stage 30 and became stronger at stages 32-36. Thereafter, the rcDmrt1 transcript was only observed in males and gradually increased from stage 42 to stage 46. By contrast, rcSox9 was observed in the whole gonadal differentiation period (stages 26-46) of males and females. In adult frogs, Dmrt1 was merely detected in testes, while rcSox9 was more highly expressed in the brain, liver, and testes. These results showed that both Dmrt1 and Sox9 participate in gonadal differentiation, and Dmrt1 is more closely implicated in testicular differentiation.