To deepen the study of the relationship between Pin1 and Notch3 in vivo, we utilized the Notch3-IC transgenic mice (N3IC-tg), a mouse model of Notch3-dependent T-ALL we previously generated,7 which overexpress constitutively activated Notch3-IC protein and lack the expression of the activated Notch1 protein (Figure 3b and Pelullo et al.31), thus resembling the leukemic human cell line TALL-1 (Figures 1e–g).21, 22 We generated double mutant mice (N3IC-tg/Pin1−/−) by intercrossing the N3IC-tg mice with the Pin1 knockout mice (Pin1−/−).32 The gene discussed is NOTCH3; the disease is acute lymphoblastic leukemia.