Cell division and hematopoietic stem cells: not always exhausting.

Pluripotent hematopoietic stem cells (HSCs) sustain blood cell production throughout an individual's lifespan through complex processes supported by self-renewal, differentiation, senescence or cell death decisions of the HSCs. These decisions are tightly regulated under homeostatic conditions, allowing both the continuous generation of progenitors and mature cells in addition to the maintenance and replenishment of the HSC pool. Several recent studies have provided insights into some of the key molecular mechanisms regulating these different cell fate decisions. One of the emerging themes of these studies is that of the importance of cell cycle regulators in the maintenance of HSCs.