ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: To ascertain the mechanistic relevance of the SOS1 and SOS 2 GEFs in the development of CML, here, we compared the various hematological parameters of the WT, SOS1-KO, and SOS2-KO transgenic (p210BCR/ABL) and non-transgenic mice (Figure 3).