Gamma secretase inhibition of Notch ameliorates early Wilms’ tumor 1 (Wt1) glomerulopathy. (a–c) Shown are representative micrographs of periodic acid–Schiff–stained sections of glomeruli of CAGG-CreERTM−/−;Wt1f/f (a), vehicle (dimethylsulfoxide)-treated CAGG-CreERTM+/–;Wt1f/f (b), and gamma secretase inhibitor (GSI-IX)-treated CAGG-CreERTM+/−;Wt1f/f transgenic mice (c) isolated late on day 5 postinduction. Bars = 50 μm. (b) Vehicle-treated mice exhibit glomerulosclerosis with hyaline material in the tubules that was not seen in control mice (a). Glomeruli of GSI-IX–treated mutants (c) do not show the same extent of glomerulosclerosis as vehicle-treated mutants. (d) Quantitative graphs of a proportion of glomeruli per genotype revealing the extent of intraglomerulosclerosis (score 0: <25% glomerulus sclerosed; score 1: 25%–50% sclerosis; score 2: 50%–75% sclerosis; score 3: >75% sclerosis). Bars represent the mean percentage of each score per genotype. Error bars represent the SEMs. At day 5 postinduction, a higher proportion of GSI-IX–treated CAGG-CreER+/−;Wt1f/f transgenic mice (n = 52 glomeruli, n = 5 mice) exhibited normal glomerular morphology compared with vehicle-treated CAGG-CreER+/−;Wt1f/f (mutants) (n = 52 glomeruli, n = 4 mice): vehicle-treated CAGG-CreER+/−;Wt1f/f versus GSI-IX–treated CAGG-CreER+/−;Wt1f/f mutant transgenic mice: score 0: 18 ± 0.9% versus 59 ± 1.0%, *P < 0.02, Student t-test; score 2: 39 ± 5% versus 8 ± 3%, **P < 0.008, Student t-test. (e) Quantitative graph showing reduced mean relative Rbpsuh, Hes1, Hes3, and Hes5 mRNA expression in podocytes from GSI-IX–treated and untreated mutant mice: CAGG-CreER+/−;Wt1f/f versus GSI-IX–treated CAGG-CreER+/−;Wt1f/f mice: Rbpsuh: 1.2 ± 0.2 versus 0.6 ± 0.03, *P = 0.01; Hes1: 1.1 ± 0.1 versus 0.6 ± 0.01, P = 0.05; Hes3: 1.4 ± 0.3 versus 0.5 ± 0.1, P = 0.05; Hes5: 3.1 ± 0.9 versus 2.0 ± 0.4, P = 0.1. Bars represent means and error bars represent SEMs. (f) Quantitative graph showing median urine albumin-creatinine ratio in vehicle-treated versus GSI-IX–treated mutant mice. Bars represent the median of each group. Error bars represent the interquartile ranges (IQRs): CAGG-CreER+/−;Wt1f/f versus GSI-IX–treated CAGG-CreER+/−;Wt1f/f mice: 35,836 (IQR: 21,304, 46,371) versus 6657 (IQR: 1337, 10,565), *P = 0.02, Mann-Whitney U test. (g) Western blot analysis demonstrates albumin in urine samples of vehicle-treated versus GSI-IX–treated mutant mice (molecular weight of albumin: 66.5 kDa). To optimize viewing of this image, please see the online version of this article at www.kidney-international.org.