Loss ofdmrt1restores female fates in the absence ofcyp19a1abut notrbpms2

Sex determination and differentiation is a complex process regulated by multiple factors, including factors from the germline or surrounding somatic tissue. In zebrafish, sex-determination begins with establishment of a bipotential gonad that undergoes sex-specific differentiation and maintenance to form the functional adult gonad. However, the relationships among these factors are not fully understood. Here we identify potential Rbpms2 targets and apply genetic epistasis experiments to decipher the genetic hierarchy of regulators of sex-specific differentiation. We provide evidence that the critical female factor, rbpms2 is epistatic to the male factor dmrt1 in terms of adult sex. Moreover, Rbpms2’s role in promoting female fates extends beyond repression of Dmrt1, as Rbpms2 is essential for female differentiation even in the absence of Dmrt1. In contrast, female fates can be restored in mutants lacking cyp19a1a in the absence of dmrt1. Taken together this work indicates that Cyp19a1a-mediated suppression of Dmrt1 is key to establish a bipotential gonad and initiate female fate acquisition, possibly by promoting rbpms2 . Then, after female fate specification, Cyp19a1a regulates subsequent oocyte maturation and sustains female fates independent of Dmrt1 repression. Author Summary We show that cyp19a1a -mediated suppression of dmrt1 establishes a bipotential gonad and female fate acquisition, possibly through rbpms2 which is required for female fates, even in the absence of Dmrt1.