Precocious Expression of the Wilms' Tumor GenexWT1Inhibits Embryonic Kidney Development inXenopus laevis

AbstractThe tumor suppressor WT1 has been demonstrated to have a wide variety of activitiesin vitroand is required for metanephric developmentin vivo.In the experiments presented here, theXenopuspronephros was used as a simple model system to examine the activity ofXenopus WT1(xWT1) during kidney development.xWT1was ectopically expressed inXenopusembryos by mRNA injection and found to inhibit pronephric tubule development. Confocal microscopy confirmed this observation and revealed that the inhibition was the result of a failure to form a pronephric anlage of appropriate size rather than a defect in epithelialization. Examination ofXlim-1expression, an early molecular marker of pronephric specification, in tailbud embryos indicated that injectedxWT1mRNA inhibited pronephric specification prior to any overt sign of morphogenesis (Xenopusstage 21). These results suggest that xWT1 may act to repress tubule-specific gene expression in the portion of the pronephros fated to form its vascular structure, the glomus