In addition, the failure to identify polyclonal IgH DJ or TCR rearrangements in ETV6-RUNX1 pre-leukemia make it unlikely that the ETV6-RUNX1 pre-leukemic hierarchy is maintained by a more primitive RAG– hematopoietic stem cell (HSC)-like population (Alpar et al., 2015, Hong et al., 2008). Here, RUNX1 is linked to leukemia.