This invention provides a system for producing differentiated cells from astem cell population for use wherever a relatively homogenous cell populationis desirable. The cells contain an effector gene under control of atranscriptional control element (such as the TERT promoter) that causes thegene to be expressed in relatively undifferentiated cells in the population.Expression of the effector gene results in depletion of undifferentiatedcells, or expression of a marker that can be used to remove them later.Suitable effector sequences encode a toxin, a protein that induces apoptosis,a cell-surface antigen, or an enzyme (such as thymidine kinase) that convertsa prodrug into a substance that is lethal to the cell. The differentiated cellpopulations produced according to this disclosure are suitable for use intissue regeneration, and non-therapeutic applications such as drug screening.
