An E Box Element Is Required for the Expression of the ad4bp Gene, a Mammalian Homologue of ftz-f1 Gene, Which Is Essential for Adrenal and Gonadal Development

Abstract

Ad4BP, also known as SF-1, is a cell type-specific transcription factor regulating all the steroidogenic P-450 genes. Recently, the targeted disruption of the mouse ftz-f1 gene encoding Ad4BP/SF-1 has established its essential function in both adrenal and gonadal development and sexual differentiation. As an initial step toward understanding its role in the cascade of gene activations necessary for the differentiation of the steroidogenic tissues and the sex differentiation of the gonads, we isolated and characterized the rat ad4bp gene. A sequence analysis of the ad4bp gene revealed that another nuclear factor ELP was also transcribed from the same gene by alternative promoter usage and splicing. The promoter of the ad4bp gene showed activities in the steroidogenic cells such as Y-1 adrenocortical cells and I-10 testicular Leydig cells when examined by transient transfection assays. Using deletion analysis and site-directed mutagenesis, we identified a cis-element at the position from -82 bp to -77 bp in the 5'-upstream region. The cis-element was identical to the consensus E box element, which is the binding site for the basic-helix-loop-helix proteins. Gel mobility shift analyses revealed the amount of a binding factor to this E box in the nuclear extract prepared from the rat testes attained a maximal level 1 week after birth and then decreased dramatically thereafter, and only trace amounts were detected in adult rats. In contrast, the binding factor in the ovaries attained a maximal level just after birth and kept its level thereafter. These dimorphic expressions of the binding factor to the E box correlated well with those of Ad4BP, and thus suggested that the expression of Ad4BP, and thus suggested that the expression of Ad4BP is transcriptionally regulated through this E box element.

Gene dosage effects and transcriptional regulation of early mammalian adrenal cortex development

“…At later stages Pod1 expression becomes sexually dimorphic and it is found in the testis interstitium but not within the ovary [65]. Pod1 was shown to repress Sf-1 expression in tissue culture experiments [65][66][67]. Consistent with this, Pod1 deficient embryos showed an expanded Sf-1 expression domain at the boundary between the gonad and mesonephros.…”

Adrenocortical development and cancer: focus on SF-1

“…An E-box-binding site within the basal promoter of the gene is critical for SF-1 expression (Nomura et al 1995), and the transcription factor POD1/capsulin was shown to suppress SF-1 expression in the gonad through binding to the E-box (Tamura et al 2001, Cui et al 2004, while WT1 has a positive role in SF-1 expression in the developing gonad (Wilhelm & Englert 2002), similarly to the LIM homeobox gene Lhx9 (Birk et al 2000). In addition, a conserved distal enhancer in intron 6 of the Sf-1 gene is important for its VMH-specific expression (Shima et al 2005).…”

The ontogenesis of the steroidogenic tissues

“…Alternatively, an investigation of the upstream regions of these genes encoding the factors is also necessary to understand the process. Regarding the study for the upstream direction, promoter analyses have been performed so far with the WT1 (Rupprecht et al 1994), mFtz-F1 (Nomura et al 1995, and DAX1 (Burris et al 1995;Ikeda et al 1996). The onset of the gene transcription and the sex-dependent transcription occurring in the processes of adrenal and gonadal differentiation are critical events which should be elucidated by the promoter analyses.…”