We initially showed that Crlf2 and mutant Jak2 alone (Jak2R683G and Jak2P933R) were insufficient for B-ALL induction using the fetal liver transplantation approach, congruent with previous findings using transgenic Eμ-JAK2R683G mouse models (Lane et al. 2014). Here, JAK2 is linked to precursor B-cell acute lymphoblastic leukemia.