WIBBELS, T.; MURDOCK, C.A.; University of Alabama at Birmingham; USDA/ARS: Dmrt1 expression in response to exogenous estrogen treatment in a reptile with temperature-dependent sex determination

Early embryonic expression of Dmrt1 appears to be essential for normal testicular development in all classes of vertebrates, including reptiles with temperature-dependent sex determination (TSD). Recent TSD studies have suggested Dmrt1 expression may represent the temperature-sensitive event during the TSD cascade. In fact, Dmrt1 expression increases at male-producing temperatures during the thermosensitive period (TSP) of several TSD reptiles. An interesting finding, in reference to Dmrt1 expression, has been that in species where exogenous steroids can stimulate sex reversal (e.g., fish and amphibians), Dmrt1 expression can also be altered. In the current study we looked at the effects of exogenous 17&beta-estradiol treatments on Dmrt1 expression at male-producing temperature (26&degC) in a reptile with TSD, the red-eared slider turtle, Trachemys scripta. Previous studies have demonstrated that exogenous estrogens can stimulate sex reversal (at male-producing temperatures) in this species of turtle. The current study showed that those T. scripta embryos that received exogenous estradiol treatments displayed significant decreases in Dmrt1 expression during the TSP, while embryos for the control group (no estradiol treatments) showed elevated Dmrt1 expression levels during the TSP. These findings indicate that exogenous estrogen treatments inhibit the upregulation of T. scripta Dmrt1 expression at male-producing incubation temperatures.