Expression of steroidogenic factor-1 in frog embryo and developing gonad

Steroidogenic factor-1 (SF-1), originally identified as an orphan nuclear r eceptor that regulates expression of genes encoding cytochrome P-450 steroi d hydroxylases, is an essential transcriptional factor for adrenal and gona dal development in mammals, Since sex steroid hormones have been shown to p lay important roles in the sex determination of frogs, it is of interest to know how SF-1 gene expression is regulated during the sexual development o f this organism. A previous study isolated the cDNA of the frog Rana rugosa SF-1 (vrSF-1) and found sexual differences in its gene expression in adult frogs; positive in testis and negative in ovary (Kawano et al., 1998). Thi s study examined urSF-1 gene expression in frog embryos and developing and mature gonads by immunohistochemical staining using anti-rrSF-1 protein ant ibody for protein localization and by in situ hybridization analysis for mR NA transcription. The results obtained in this study indicated that cells e xpressing SF-I that originate in the mesoderm and endoderm probably migrate into the developing gonad via the dorsal mesentery, genital ridge, and mes orchium or mesovarium. Thus, SF-1 may play an important role in gonadal dev elopment in amphibians. (C) 2001 Academic Press.