Loss ofdmrt1restores female fates in the absence ofcyp19a1abut notrbpms2

Abstract

Sex determination and differentiation is a complex process regulated by multiple factors, including factors from the germline or surrounding somatic tissue. In zebrafish, sexdetermination 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 SummaryWe 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. IntroductionAlthough sex-determination is a common biological process critical to reproduction and thus species survival in sexually reproducing organisms, the mechanisms controlling this process vary extensively among animal species. The decision to develop as one sex or the other is triggered in different species by many environmental factors including temperature and nutrition status, presence of sex chromosomes, and the function of many sex-associated genetic factors that converge upon regulation of downstream sexual differentiation factors, for example, Sox9 (SRYbox 9), FoxL2 (Forkhead box L2), Dmrt1 (Doublesex and mab-3 related transcription factor 1), and Cyp19a1a (Aromatase; Cytochrome P450, family 19, subfamily a) [1][2][3][4]. In domesticated lab strains of zebrafish, sex determination appears to be polygenic [5][6][7][8], being influenced by numerous genetic factors. Like most teleost fish, zebrafish are a gonochoristic species, eventually differentiating into one of two sexes, that do not switch sex as adults [9]. However, the early zebrafish gonad is bipotential and thus is poised to develop as either an ovary or a testis [10]. This plasticity provides an excellent model for studying genetic factors and interactions between essential regulators of sex-specific differentiation among vertebrates.Factors regulating sex differentiation and maintenance vary in function, from transcription factors regulating sex-specific programs, to regulators of signaling molecules, and even signaling molecules themselves. Doublesex and mab-3 relate...