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.
Adaptor Proteins, Signal Transducing ; Animals ; Cytochrome P-450 Enzyme System ; metabolism ; Female ; Gene Expression ; Germ Cells ; cytology ; physiology ; Male ; Meiosis ; Mice ; Proteins ; genetics ; physiology ; Retinoic Acid 4-Hydroxylase ; Spermatogenesis ; genetics ; Tretinoin ; metabolism

AIMTo study the expression pattern of the retinoic acid metabolizing enzymes RALDH2 and CYP26b1 during mouse postnatal testis development at both mRNA and protein levels.

METHODSReal-time polymerase chain reaction and Western blot analysis were performed to determine the relative quantity of RALDH2 and CYP26b1 at both mRNA and protein levels at postnatal day 1, 5, 10, 20, and in adult mice (70 days testes). Testicular localization of RALDH2 and CYP26b1 during mouse postnatal development was examined using immunohistochemistry assay.

RESULTSAldh1a2 transcripts and its protein RALDH2 began to increase at postnatal day 10, and remained at a high level through postnatal day 20 to adulthood. Cyp26b1 transcripts and CYP26b1 protein did not change significantly during mouse postnatal testis development. RALDH2 was undetectable in the postnatal 1, 5 and 10 day testes using immunohistochemistry assay. At postnatal day 20 it was detected in pachytene spermatocytes. Robust expression of RALDH2 was restricted in round spermatids in the adult mouse testis. In the developing and adult testis, CYP26b1 protein was confined to the peritubular myoepithelial cells.

CONCLUSIONOur results indicate that following birth, the level of retinoic acid in the seminiferous tubules might begin to increase at postnatal day 10, and maintain a high level through postnatal day 20 to adulthood.

Aldehyde Oxidoreductases ; genetics ; metabolism ; Animals ; Cytochrome P-450 Enzyme System ; genetics ; metabolism ; Gene Expression Regulation, Developmental ; Male ; Mice ; Mice, Inbred BALB C ; RNA, Messenger ; metabolism ; Rabbits ; Retinoic Acid 4-Hydroxylase ; Seminiferous Epithelium ; cytology ; metabolism ; Sensitivity and Specificity ; Spermatids ; cytology ; metabolism ; Testis ; cytology ; growth & development ; metabolism