CBL and myeloproliferative disorder: We showed that MMTV-driven Cre expression in Cbl-flox/flox, Cbl-b-null mice produced a Cbl/Cbl-b DKO in hematopoietic cell lineages (referred to as Cbl/Cbl-b DKO, or DKO), and these mice developed an expanded HSC pool and severe MPD with an average lifespan of only eight weeks [21].