Figure 2.

Balancing stem cell divisions with cell fate. (a) Progenitors in the basal layer of the epidermis can divide asymmetrically to yield two cells that are differentially fated to become a progenitor cell (PC) and a differentiating cell (DC). Alternatively, they can divide symmetrically to produce two cells that both either differentiate, as in (b) or maintain their progenitor fate, as in (c). Asymmetric divisions would maintain tissue balance, as in homeostasis, whereas symmetric divisions would alter the stem cell population within the tissue, as in processes such as ageing, wound healing or hyperproliferative disorders, including cancer.