Figure 2.

Maintaining individual stem cells or stem cell populations

(A) Example of a “neutral drift” adult stem cell model. In the intestinal epithelium, stem cells residing at the crypt bottom divide symmetrically and compete for the limited niche space. Stem cell maintenance is guaranteed at the level of the population, but individual ASC clones are stochastically outcompeted while others gain dominance.

(B) In the fibers of skeletal muscles, satellite cells can divide asymmetrically when the mitotic axis is perpendicular to the muscle fiber. The daughter cell retaining access to the basal lamina will maintain stem cell potential, whereas the other daughter cells commit to differentiation. In this example, the ASC displays asymmetry at the single-cell level, and individual clones are maintained.