Self-Renewal and Differentiation

Stem cells are defined by their dual capacity for self-renewal and multipotent differentiation. Because most mature cells have a limited life span, the capacity of stem cells to both replenish aged mature cells and perpetuate themselves through self-renewal is crucial to the maintenance of tissue homeostasis. Cell-intrinsic networks cooperate with signals from the microenvironment to fine-tune the self-renewal capacity of stem cells. Understanding precisely how stem cell self-renewal is regulated is crucial to our understanding of normal development, stem cell homeostasis, [Page 1007]and oncogenesis, and will lay the foundation for new therapeutic strategies. Increasing evidence suggests that most stem cells divide either symmetrically or asymmetrically and that this balance is controlled by developmental and environmental signals guiding the production of the appropriate numbers of stem ...