DMRT1 expression during gonadal differentiation and spermatogenesis in therainbow trout, Oncorhynchus mykiss

DMRT1 has been suggested to be the first conserved gene involved in sex dif ferentiation found from invertebrates to human. To gain insight on its impl ication for fish gonadal differentiation, we cloned a DMRT1 homologue in th e rainbow trout, Oncorhychus mykiss (rtDMRT1), and showed that this gene is expressed during testicular differentiation, but not during ovarian differ entiation. After 10 days of steroid treatment, expression was shown to be d ecreased in estrogen-treated male differentiating gonads but not to be rest ored in androgen-treated differentiating female gonads. This clearly reinfo rces the hypothesis of an important implication for DMRT1 in testicular dif ferentiation in all vertebrates. In the adults a single 1.5 kb transcript w as detected by Northern blot analysis in the testis. and its expression was found to be sustained throughout spermatogenesis and declined at the end o f spermatogenesis (stage VI). Along with this expression in the testis we a lso detected by reverse transcriptase-polymerase chain reaction a slight ex pression in the ovary. We also obtained new DM-domain homologous sequences in fish, and their analysis suggest that at least four different genes bear ing 'DM-domain' (DMRT genes) exist in fish just as in all vertebrate genome s. (C) 2000 Elsevier Science B.V. All rights reserved.