Fig. 3: Notch1 mutants colonize aging esophageal epithelium.
From: Notch1 mutations drive clonal expansion in normal esophageal epithelium but impair tumor growth
a, YFPCreNotch1+/flox and YFPCreNotch1+/+ mice were induced at a high level and aged for 65 weeks. b, Representative NOTCH1 staining in esophageal epithelium of aging YFPCreNotch1+/+ and YFPCreNotch1+/flox mice at the indicated time points. White dashed lines delineate negative areas and solid lines delineate tissue edges. Images representative of three mice per time point. Scale bars: 500 µm c, Percentage of NOTCH1− area increases with age in Notch1+/+ (Kendall’s tau-b correlation = 0.56, P = 0.0062) and Notch1+/− (Kendall’s tau-b correlation = 0.91, P = 8.3 × 10−6) esophagi (Mean ± s.e.m., n = 3 mice per time point). P values shown are from two-sided Welch’s t test. d, Schematic of Notch1+/− cells (purple cells) showing the spontaneous appearance of expanding NOTCH1− cells (black) with aging, possibly caused by genetic events affecting the Notch1 locus. e, Highly induced YFPCreNotch1+/flox mice were aged 54–78 weeks old, when esophageal epithelium was collected and stained for NOTCH1 (magenta), YFP (green) and DNA (blue). Expanding areas devoid or fully stained with YFP appeared distinct from normal-appearing areas marked with a patchwork of small YFP+ clones. Expanded NOTCH1− (yellow) and NOTCH1+ (orange) areas and normal-appearing areas (blue) were isolated for targeted sequencing (n = 246 biopsies from ten mice). Colored circles show the sampled areas. White dashed lines delineate negative areas. Scale bars: 500 µm. f, Proportion of normal appearing, expanded NOTCH1− and expanded NOTCH1+ biopsies with Notch1 mutations or CNLOH. g, Proportion of NOTCH1− and NOTCH1+ areas carrying a secondary missense, nonsense or indel/splicing Notch1 mutation. For f and g, n samples are shown in brackets, redundant samples, defined as biopsies sharing the same mutation and separated by <1 mm were counted once (n = 227 unique biopsies in total). h, Model of colonization by Notch1 clones. Clonal fitness increases from monoallelic and biallelic Notch1 mutation resulting in a selective pressure (blue arrows) for biallelic gene alterations. p.i., postinduction, w.p.i., weeks postinduction. WT, wild type. KO, knock-out allele lacking Notch1 exon 1. Mut, mutation. ND, none detected. See Supplementary Tables 9–11.
