Fig. 2.

The observed proportion of erythrocytes is inconsistent with purely stochastic theory of lineage commitment. According to the stochastic theory of lineage commitment, Tpo affects proportions of committing erythrocytes only through modulation of growth and survival of committing megakaryocytes. Simulation of this model reveals that when Tpo is added to Epo-only medium on day 3, the observed proportion of o-dianisidine-stained cells on day 4 is substantially higher than expected under the stochastic theory.