Numerous genes required for adrenocortical steroidogenesis are activated by the nuclear hormone receptor steroidogenic factor 1 (SF-1) (NR5A1). Dax-1 (NR0B1), another nuclear hormone receptor, represses SF-1-dependent activation. Glucocorticoid products of the adrenal cortex provide negative feedback to the production of hypothalamic CRH and pituitary ACTH. We hypothesized that glucocorticoids stimulate an intraadrenal negative feedback loop via activation of Dax-1 expression. Reporter constructs show glucocorticoid-dependent synergy between SF-1 and glucocorticoid receptor (GR) in the activation of Dax-1, which is antagonized by ACTH signaling. We map the functional glucocorticoid response element between -718 and -704 bp, required for activation by GR and synergy with SF-1. Of three SF-1 response elements, only the -128-bp SF-1 response element is required for synergy with GR. Chromatin immunoprecipitation (ChIP) assays demonstrate that dexamethasone treatment increases GR and SF-1 binding to the endogenous murine Dax-1 promoter 10- and 3.5-fold over baseline. Serial ChIP assays reveal that that GR and SF-1 are part of the same complex on the Dax-1 promoter, whereas coimmunoprecipitation assay confirms the presence of a protein complex that contains both GR and SF-1. ACTH stimulation disrupts the formation of this complex by abrogating SF-1 binding to the Dax-1 promoter, while promoting SF-1 binding to the melanocortin-2 receptor (Mc2r) and steroidogenic acute regulatory protein (StAR) promoters. Finally, dexamethasone treatment increases endogenous Dax-1 expression and concordantly decreases StAR expression. ACTH signaling antagonizes the increase in Dax-1 yet strongly activates StAR transcription. These data indicate that GR provides feedback regulation of adrenocortical steroid production through synergistic activation of Dax-1 with SF-1, which is antagonized by ACTH activation of the adrenal cortex.

The action of a variety of peptide hormones is critical for proper growth and differentiation of the urogenital ridge, which ultimately gives rise to the kidney, adrenal cortex, and gonad. One such class of peptides is the Wnt family of secreted glycoproteins that is classically involved in development of cell polarity and cell fate determination. Notably, alterations in Wnt-4 expression in mice and humans result in profound defects in urogenital ridge development, including dysregulation of kidney, gonadal, and adrenal growth. The nuclear receptor steroidogenic factor-1 (SF-1) has been implicated as a downstream effector of peptide hormone signaling during urogenital ridge development as evidenced by both the activation of SF-1-dependent transcription in the adrenal cortex by signaling molecules such as protein kinase A and by the adrenal and gonadal agenesis in mice with null mutations in SF-1. We hypothesized that Wnt-dependent signaling cascades regulate SF-1-dependent transcription of genes required for adrenogonadal development. Specifically, the data demonstrate that ␤-catenin synergizes with SF-1 to activate the ␣-inhibin promoter through formation of a transcriptional complex. The activation requires an intact SF-1 RE and is independent of TCF/Lef. These data support the recent observation that ␤-catenin can participate in nuclear receptor-mediated transcriptional activation and extend the findings to the monomer binding class of orphan nuclear receptors.

We have cloned T-cell factor 4N (TCF-4N