FUNCTION AND DISTRIBUTION OF A STEROIDOGENIC CELL-SPECIFIC TRANSCRIPTION FACTOR, AD4BP

Ad4BP was identified as an essential transcription factor regulating s teroidogenic cell-specific and cAMP-dependent transcription of the gen es of steroidogenic P450s. The Ad4BP transcript was detected in steroi dogenic tissues such as adrenal gland, testis, ovary, placenta and bra in by RT-PCR, and showed good correlation with the expression of stero idogenic P450s. The genes of steroidogenic P450s, which are transcribe d only in steroidogenic cells, were transcribed in non-steroidogenic c ells when an Ad4BP expression vector was introduced into the cells. To study the function of Ad4BP in the differentiation of the steroidogen ic tissues, immunochemical and immunohistochemical studies were perfor med with the tissues prepared from various developmental stages of rat s. Adrenal cortex expressed Ad4BP since the tissue was detected in the dorsal wall of the fetus. Gonadal tissues expressed Ad4BP in a sex-de pendent manner. High levels of Ad4BP expression were detected in fetal and prepubertal testes and in prepubertal and adult ovaries, whereas low level expressions were observed in the adult testes and in the fet al ovaries. The expression of Ad4BP in the gonads correlates well with the expression of the Mullerian inhibiting substance gene as well as the steroidogenic P450 gene for both sexes. These observations indicat e that Ad4BF plays an important role in the development and differenti ation of the steroidogenic tissues including sexual differentiation of the gonadal tissues through activation of the transcription of its ta rget genes.