["Wilms' tumor suppressor gene (WT1) is essential for normal podocyte function, and transforming growth factor (TGF)-beta contributes to focal segmental glomerulosclerosis (FSGS). We aimed to address whether TGF-beta affects WT1 expression in podocytes.", 'A human podocyte cell line treated with TGF-beta1 and kidneys in Alb/TGF-beta1-transgenic mice were analyzed for WT1 expression.', "In cultured podocytes, TGF-beta1 reduced WT1 protein expression determined by western blotting beginning at 8 h and decreased WT1 messenger RNA (mRNA) expression measured by quantitative reverse transcription-polymerase chain reaction beginning at 3 h. Knockdown of Smad4 by small hairpin (sh) RNA partially rescued the TGF-beta1-induced reduction of both WT1 protein and mRNA expressions in the cultured podocytes. TGF-beta1 did not alter luciferase activity of the reporter construct for a human WT1 promoter but reduced that for a human WT1 5' enhancer construct, suggesting that TGF-beta1 may regulate WT1 expression by altering the 5' enhancer activity. In the transgenic mice, WT1 protein expression in podocytes was decreased at 1 and 3 weeks of age, while glomeruloclerosis developed after 3 weeks."] Does tGF-beta1 reduce Wilms ' tumor suppressor gene expression in podocytes?