REGULATION OF RENAL EGF RECEPTOR EXPRESSION IS NORMAL IN DENYS-DRASH-SYNDROME

In patients with Denys-Drash syndrome, mutations of the Wilms' tumor s uppressor gene are associated with nephroblastomas and developmental a bnormalities of the genital tract and renal glomerulus. Normally, the Wilms' tumor gene product (WT1) is expressed at high levels in viscera l glomerular epithelial cells (VGEC) of the emerging fetal glomerulus. We demonstrate that WT1 could normally serve to suppress EGF receptor expression in VGEC, since immunoreactive EGF receptor is strikingly a bsent compared to epithelial cells of the emerging proximal and distal tubule, which lack WT1. When HEK293 cells were co-transfected with pl asmids containing EGFR enhancer/promoter elements linked to a CAT repo rter and plasmids containing WT1 cDNA, EGFR enhancer/promoter activity was suppressed by all wild-type WT1 isoforms, but not by deletion mut ants of WT1 lacking normal zinc-finger or N-terminal domains. Surprisi ngly, plasmids expressing a Denys-Drash WT1 mutant (R394W) retained th e ability to suppress EGFR promoter activity in this system. Furthermo re, we found that immunoreactive EGFR was appropriately undetectable i n glomeruli from a three-year-old girl with Denys-Drash syndrome and i n sections of her Wilm's tumor. These data suggest that faulty suppres sion of EGFR cannot account for the abnormalities of glomerulogenesis seen in Denys-Drash patients.