RESPONSE DIVERSITY AND THE TIMING OF PROGENITOR-CELL MATURATION ARE REGULATED BY DEVELOPMENTAL-CHANGES IN EGFR EXPRESSION IN THE CORTEX

Early cortical progenitor cells of the ventricular zone (VZ) differ fr om later progenitor cells of the subventricular zone (SVZ) in cell-typ e generation and their level of epidermal growth factor receptors (EGF Rs). To determine whether differences in their behavior are causally r elated to EGFR number/density, we introduced extra EGFRs into VZ cells with a retrovirus in vivo and in vitro. This results in premature exp ression of traits characteristic of late SVZ progenitor cells, includi ng migration patterns, differentiation into astrocytes, and proliferat ion of multipotential cells to form spheres. The choice between prolif eration and differentiation depends on ligand concentration and progen itor cell age and may reflect different thresholds of stimulation. The level of EGFRs expressed by progenitor cells in the cortex may theref ore contribute to the timing of their maturation and choice of respons e to pleiotropic environmental signals.