WT1 and Sox11 regulate synergistically the promoter of the Wnt4 gene that encodes a critical signal for nephrogenesis.

Wnt4, a member of the Wnt superfamily of signaling molecules, is critical for mammalian kidney development, since nephrogenesis fails in its absence, while Wnt4 signaling induces mesenchyme-to-epithelium transition and associated tubulogenesis in the uninduced mesenchymal cells in the classic transfilter model. The factors that promote Wnt4 gene expression during kidney development are largely unknown, however. We addressed the upstream regulators of the Wnt4 gene and describe here the transcription factors WT1 and Sox11 as candidate molecules in the control of gene expression. We found that WT1/Sox11 regulate Wnt4 promoter expression in a synergistic fashion in an embryonic kidney mesenchyme-derived cell line model. The transcription complex containing WT1/Sox11 was immunoprecipitated from embryonic kidney cells with Sox11 antibodies, suggesting their presence in the same complex. Dominant negative forms of WT1, namely P129L and F154S mutants, inhibited Wnt4 expression, but this inhibition was not influenced by the presence of wild-type Sox11. The mutant WT1 forms were similarly incapable of interacting with Sox11, as judged by reporter studies. The spatio-temporal expression pattern of wt1 and sox11 overlaps with that of Wnt4 in the early Xenopus pronephros. Morpholino-mediated knockdown of either wt1 or sox11 inhibited Wnt4 expression in the prospective pronephros of the Xenopus embryos. We propose that Sox11 represents a synergistic factor for WT1 in regulating the Wnt4 gene expression that is critical for nephrogenesis during kidney ontogeny.