The role of Wt1 in regulating mesenchyme in cancer, development, and tissue homeostasis.

From both the fundamental and clinical perspectives, there is growing interest in mesenchymal cells and the mechanisms that regulate the two-way switch between mesenchymal and epithelial states. Here, we review recent findings showing that the Wilms' tumor gene (Wt1) is a key regulator of mesenchyme maintenance and the mesenchyme to epithelial balance in the development of certain mesodermal organs. We summarize recent experiments demonstrating, unexpectedly, that Wt1 is also essential for the integrity or function of multiple adult tissues, mainly, we argue, through regulating mesenchymal cells. We also discuss growing evidence that implicates Wt1 in tissue repair and regeneration. Drawing on these findings, we highlight the similarities between Wt1-expressing cells in different tissues. We believe that future studies aimed at elucidating the mechanisms underlying the functions of Wt1 in adult cells will reveal key cell types, pathways, and molecules regulating adult tissue homeostasis and repair.