CDNA Cloning And Expression Of Dmrt1 In Clarias Fuscus

Sex of fish is determined by both genetic substance and environment. The studies on the relationship between the sex and sex-related genes expression not only can reveal the mechanisms of sex determination, but also can provide the theoretical basis to control the sex differentiation in artificial propagation in the fish. Catfish (Clarias fuscus) is a common freshwater fish in China. The Dmrt1 cDNA sequences were isolated from the testes of Clarias fuscus by RT-PCR and SMARTer RACE. Structure and function of the predicted Dmrt1 protein were analyzed by bioinformatics. Expression of Dmrt1 were examined using semi-quantitative RT-PCR in ten tissues (testes, ovaries, muscles, intestine, livers, heart, head kidney, gills, brains and eyes) and the testes from stageⅡto stageⅤ. Results showed that the Dmrt1 complete cDNA was 1417 bp in length, and the 5'un-translated region (5'UTR) and the 3'un-translated region (3'UTR) were 35 bp and 516 bp, respectively. The open reading frame (ORF) was 864 bp, and a sequence of predicted 287 amino acids recidues were encoded. A highly conserved DM domain was found in the DMRT1 protein, which was a common characteristic in DMRT clusters. The C. fuscus DMRT1 shared a highest amino acid identity of 100% with Rainbow trout and zebra fish, and 99% with Takifugu rubripes. The DM domain sequence alignment showed that the similarity was over 80% among fish, Xenopus, chicken, rat, pig and human. In addition, the DM domain of C. fuscus had a typical"C2H2C4"zinc finger structure, which bound with the downstream DNA and control the gene transcription.The expression of Dmrt1 was found only in the testes, but not in the ovaries, muscles, intestine, liver, heart, head kidney, gills, brain and eyes, which suggested that Dmrt1 was a testis-specific gene in C. fuscus. The expression of Dmrt1 in testes stageⅡ(spermatogenesis) was significantly higher compared with the testes from stageⅢto stageⅤ(P<0.05), which indicated that Dmrt1 was related to the spermatogenesis and the testes development in C. fuscus.