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The Wilms' tumor suppressor gene (wt1) product regulates Dax-1 gene expression during gonadal differentiation
1Department of Biochemistry, Experimental Medicine, McGill University, Montreal, Quebec, Canada.
Abstract:
Gonadal differentiation is dependent upon a molecular cascade responsible for ovarian or testicular development from the bipotential gonadal ridge. Genetic analysis has implicated a number of gene products essential for this process, which include Sry, WT1, SF-1, and DAX-1. We have sought to better define the role of WT1 in this process by identifying downstream targets of WT1 during normal gonadal development. We have noticed that in the developing murine gonadal ridge, wt1 expression precedes expression of Dax-1, a nuclear receptor gene. We document here that the spatial distribution profiles of both proteins in the developing gonad overlap. We also demonstrate that WT1 can activate the Dax-1 promoter. Footprinting analysis, transient transfections, promoter mutagenesis, and mobility shift assays suggest that WT1 regulates Dax-1 via GC-rich binding sites found upstream of the Dax-1 TATA box. We show that two WT1-interacting proteins, the product of a Denys-Drash syndrome allele of wt1 and prostate apoptosis response-4 protein, inhibit WT1-mediated transactivation of Dax-1. In addition, we demonstrate that WT1 can activate the endogenous Dax-1 promoter. Our results indicate that the WT1-DAX-1 pathway is an early event in the process of mammalian sex determination.
Insights
Wilms tumor 1 (WT1) protein activates the Dax-1 gene promoter, a crucial step in early mammalian sex determination. This WT1-DAX-1 pathway is essential for normal gonadal development, influencing ovarian or testicular differentiation.
Area of Science:
- Developmental Biology
- Genetics
- Molecular Biology
Background:
- Gonadal differentiation relies on a molecular cascade for ovarian or testicular development from the bipotential gonadal ridge.
- Key genes like Sry, WT1, SF-1, and DAX-1 are essential for this process.
Purpose of the Study:
- To elucidate the role of Wilms tumor 1 (WT1) in gonadal development by identifying its downstream targets.
- To investigate the regulatory relationship between WT1 and Dax-1 during mammalian sex determination.
Main Methods:
- Analysis of spatial expression profiles of WT1 and Dax-1 in developing murine gonads.
- WT1 transactivation assays on the Dax-1 promoter, including footprinting, transient transfections, promoter mutagenesis, and mobility shift assays.
- Investigation of WT1-interacting proteins' effect on Dax-1 transactivation.
Main Results:
- WT1 expression precedes Dax-1 expression in the developing murine gonadal ridge, with overlapping spatial distribution.
- WT1 directly activates the Dax-1 promoter, likely through GC-rich binding sites upstream of the TATA box.
- Specific WT1-interacting proteins inhibit WT1-mediated activation of the Dax-1 promoter.
Conclusions:
- The WT1-DAX-1 pathway represents an early molecular event in mammalian sex determination.
- WT1 plays a critical role in regulating Dax-1, thereby influencing gonadal differentiation.