Of note, hematopoietic progenitor colony hypersensitivity to GM-CSF, an established hallmark of JMML, has also been depicted in CMML, especially in RAS mutant pCMML15,32 and was also seen in progenitor cells obtained from the Vav-Cre-NrasG12D pCMML mouse model in this study. Here, CSF2 is linked to juvenile myelomonocytic leukemia.