a, b, Co-immunofluorescence for GFP and EdU (a) or phospho-histone H3 (b) in TKO Hes1GFP/+ tumours. c, Weight of tumours formed from freshly sorted GFPneg and GFPhigh tumour cells implanted subcutaneously in immunocompromised NSG mice (n = 6 tumours each; two-tailed unpaired Student’s t-test). d, Flow cytometry of GFP in a tumour formed from freshly sorted GFPneg cells implanted subcutaneously in immunocompromised NSG mice (representative of n = 6 biological replicates). *P < 0.05. Data are represented as mean ± s.d. Scale bars, 50 μm.