VAV1 and juvenile myelomonocytic leukemia: Since an incidental CBL/CBL-B DKO in a minority of HSCs in these mice led to a model that recapitulated the aggressiveness of JMML but nonetheless with a delayed onset, we engineered a model in which CBL deletion was initiated in HSCs of CBL-B-null mice using VAV1-Cre, which is known to direct gene deletion during both fetal and adult hematopoiesis [25, 26].