As a low level of PU.1 is a prerequisite for the differentiation of common myeloid progenitors (CMPs) to megakaryocyte/erythroid progenitors (MEPs) [12], it is reasonable that PU.1 levels would be lower in the M6 (acute erythroleukemia) and M7 (acute megakaryocytic leukemia) subtypes. This evidence concerns the gene SPI1 and acute erythroid leukemia.