Erythroid cell development and leukemic transformation: interplay between signal transduction, cell cycle control and...

Studies using genetically modified mice and ex vivo tissue culture of erythroid progenitors converge to show that generation of mature erythroid cells depends on the interplay between specific transcriptional regulators and intracellular signals controlled by cytokines and growth factors. These studies also show that terminal differentiation in the erythroid lineage is unusual since the acquisition of the phenotypic traits of mature cells occurs while the cells are still actively dividing. Furthermore, under specific stress conditions, a massive and sustained self-renewal of committed erythroid progenitors can take place to replenish the pool of terminally differentiated cells. We review here how the erythroid genetic program and its interplay with specific cytokines, growth factors and hormones controls survival, proliferation and differentiation of erythroid progenitors both in normal and stress conditions. Special emphasis is laid on our present understanding of the differences in cell cycle control, which result either in self-renewal of erythroid progenitors or in the particular cell divisions which accompany terminal differentiation. Finally, we discuss how deregulation of the various aspects of the physiological control of erythroid progenitor survival, proliferation and differentiation can lead to erythroblast transformation and erythroleukemia.