These experiments demonstrated that the estimated transplantable cell frequency of both Mac1+Gr1+ B220+Kit+ and Mac1− Gr1− B220+Kit+ cell populations was ∼1/1,000, demonstrating that Mac1+Gr1+ cells, which are typically regarded as terminally differentiated, can self-renew and transmit MDS. Here, PTPRC is linked to myelodysplastic syndrome.