ABSTRACT
Stra8 (stimulated by retinoic acid gene 8) is a specific expression gene in mammalian germ cells' transition from mitosis to meiosis. Stra8 expresses in an anterior to posterior wave from embryonic days 12.5 to 16.5 in germ cells of XX gonads in mice. Meiosis germ cells are observed 1 day after Stra8 expression, which begins in the testis after birth and triggers meiosis entry. Germ cell sex determination is directed by a difference in the timing of entry into meiosis in embryonic gonads. The position of retinoic acid production and CYP26b1 expression that metabolizes RA to an inactive form regulates Stra8 expression. Although cytoplasmic protein Stra8 is necessary for the entry of germ cells into meiotic prophase, the function of the protein remains unknown.