Figure 6.

Feedback on the cell cycle length of stem cells induces transient peaks of stem cell density. (A) Time course of stem cell distribution from the basal (z = 0) to apical direction is presented at four time points: 14, 21, 28, and 45 (cell cycles/ln 2). In each figure, the green-colored curve represents the stem cell density without any feedback on the cell cycle lengths (β = 0). The density of stem cells is graded monotonically from the basal lamina, with the stem cell niche established at T = 14. The red-colored curve is the stem cell density with molecule A regulating the cell cycle length of stem cells (β = 3). Two local maxima of stem cell density, one at the basal lamina, and the other at the apical surface, appear by T = 14, and the peak at the apical surface vanishes eventually, after T = 45. (B) Stem cell distributions at time points T = 14, 21, 28, and 45.