As expected, 19 of 20 SCLtgLMO1tg T-ALL in Cd3e+/+Heb/Tcf12+/+ mice exhibit Notch1 gain of function mutations (4, 85) which affect the PEST domain whereas Cd3e-deficient SCLtgLMO1tgHeb/Tcf12+/+ T-ALL completely lacked Notch1 mutation as reported (4). The gene discussed is NOTCH1; the disease is acute lymphoblastic leukemia.