Adrenocortical and Gonadal Expression of the Mammalian Ftz-F1 Gene Encoding Ad4BP/SF-1 Is Independent of Pituitary Control

Abstract

Ad4BP/SF-1 is a transcription factor essential for the development of the adrenal gland and the gonads as well as for the maintenance of their functions through regulating tissue-specific gene transcription. In the whole body, hypothalamo-pituitary-gonadal and -adrenal axes are known to play prominent roles in mediating the function of the gonads and adrenal. In this study, the effects of the tropic peptide hormones secreted by the pituitary on the regulation of the rat Ftz-F1 (rFtz-F1) gene encoding Ad4BP/SF-1 were investigated. Immunochemical studies revealed that Ad4BP/SF-1 was expressed even in the adrenal cortex of hypophysectomized rats. Such persistent expression of Ad4BP/SF-1 was also observed in the testes and ovaries of the hypophysectomized animals. In contrast to Ad4BP/SF-1, the expressions of steroidogenic P450s were reduced significantly. The transcriptional activities of the endogenous and transfected rFtz-F1 genes were examined with Y-1 and I-10 cells derived from mouse adrenocortical and testicular Leydig cell tumors, respectively. Neither gene appeared to be activated significantly by cAMP, whereas both endogenous and exogenous CYP11A genes encoding P450(SCC) were activated. Taken together, these observations indicate that the expression of the rFtz-F1 gene is mainly regulated by a mechanism independent of the neuroendocrine axes.