The elaboration of the PrCR signal [unopposed by CD47] in oligopotent hematopoietic progenitors in at least some myelodysplastic syndrome patients, in whom >95% of their HSC are from the single cell with a chromosomal anomaly such as monosomy 7, demonstrates that the PrCR signal can be elicited in a single differentiation step; the transition from MDS to AML is accompanied with upregulation of CD4759. This evidence concerns the gene CD47 and acute myeloid leukemia.