In Abe's lab, we have been investigating the molecular mechanism of spermatogenesis using culture of amphibian testis as a model system. Amphibian testis has advantages that culture is easy and structure of the testis is simple compared with mammalianﾕs one. We have established organ culture in which addition of follicle-stimulating hormone (FSH) alone induces differentiation of spermatogonia to primary spermatocytes. Stem cell factor (SCF) and insulin-like growth factor (IGF)-I are shown to play important roles as growth factors in proliferation of spermatogonia. Furthermore, we recently clarified that concentration ratio of FSH/prolactin determines whether spermatogonia enter meiosis or go to die (checkpoint mechanism for entrance into meiosis).
In addition, we have been investigating the molecular mechanism of sex differentiation and sex reversal, using Japanese flounder of which genetic females can be sex-reversed to phenotypic males by rearing the larvae at high or low water temperature or by treatment with sex steroid hormones during the sex differentiation period.