Expression of RARs and RXRs in prenatal gonads and germ cells has not been studied in the same detail, for instance, as in adult mouse testis ([Vernet et al., 2006] and references therein). Thus, it is currently unclear which receptor(s) mediate the recently-discovered role of RA as a meiosis-inducing factor in female germ cells during development ([Bowles and Koopman, 2007] for review, and references therein).
