Metanephric mesenchyme epithelializes upon induction by the invading ureter tips. Using in situ hybridization, high level of paired-box transcription factor 2 (Pax2) expression is visualized at the periphery of the developing kidney where nephron differentiation is taking place. Pax2 is responsible for the regulation of a number of target genes, among them CnABP, a Calcineurin A-binding protein. Deregulation of Pax2 and its target genes are thought to be involved in Wilms' tumorigenesis. For details, see the article by Nguyen and colleagues on page 821.