A model for the regulation of myelopoiesis by specific factors

Hematopoietic cells originate from stem cells that generate progenitor cells programmed to differentiate along specific cell lineages. Recently, a number of factors have been identified that are involved in regulating the proliferation of myeloid lineage cells. We propose a model in which a hierarchy of specific factors acts sequentially during defined stages of maturation to regulate myelopoiesis. The role of these factors as competence or progression factors in causing cells to enter and traverse the cell cycle is discussed. Experimental evidence supports the model.