Figure 1.

Proliferation diagram of a stem cell. Red nodes indicate events with stochastic outcome (e.g. division or transformation; symmetric or asymmetric division), blue nodes describe the outcome of particular events using chemical reaction notation (S, stem cell, P, neural progenitor, A, astrocyte). θ₁ denotes the probability of stem cell division, p₁ denotes the proliferation rate; a₁ reflects the probability that a daughter cell has the same fate as its parent cell (self-renewal takes place) and κ is the probability that a neural progenitor is produced in an asymmetric division rather than an astrocyte.