The Wilms' tumour suppressor 1 (WT1) gene encodes a DNA- and RNA-binding protein that regulates nephron progenitor differentiation during renal development and that is often inactivated in Wilms' tumour, a childhood kidney malignancy. Now, on p. 1189, Jordan Kreidberg and co-workers provide a comprehensive description of WT1 target genes that are expressed in nephron progenitors in embryonic mouse kidneys. Using chromatin immunoprecipitation coupled to mouse promoter microarray (ChIP-chip) to analyse chromatin prepared from embryonic mouse kidneys, the researchers identify more than 1600 genes to which WT1 binds. These genes include essential kidney development genes, such as Bmp7, and numerous genes not previously studied in developing kidneys. To validate these genes as WT1 targets, the researchers use a WT1 morpholino loss-of-function approach in kidney explants. Low doses of WT1 morpholino reduce WT1 target gene expression in nephron progenitors, they report, whereas high doses arrest kidney development. Collectively, these data provide novel insights into the signalling networks and biological processes that WT1 regulates during kidney development.