Interestingly, expressing supra-physiological levels of Notch1 ICD, as determined by the elevated levels of Hey1 (Figure 5—figure supplement 1C and D) expression, did not generate a phenotype, which is in contrast to other situations of hyperactivated Notch signaling, for example in acute lymphoblastic T-cell leukemia (Weng et al., 2004). This evidence concerns the gene NOTCH1 and T-cell acute lymphoblastic leukemia.