Mechanisms of progenitor maturation are conserved in the striatum and cortex

We recently reported that developmental changes in the expression of epider mal growth factor receptors (EGFRs) by cortical progenitor cells regulate t heir fate and migration. Higher levels of EGFRs are expressed by later embr yonic progenitor cells and are required for several responses to EGF family ligands, including astrocyte differentiation and migration. Progenitor cel ls in the ganglionic eminence (GE), the forerunner of the striatum, also ex hibit a developmental increase in EGFR expression. The striatum differs fro m the cortex in several respects, including cytoarchitecture, the timing of changes in EGFRs, and the level of transforming growth factor-alpha (TGF a lpha) expression. To determine whether signaling mediated by EGFRs in GE pr ogenitors regulates their fate and migration as observed in cortex, we used a retrovirus to increase EGFR expression in embryonic GE progenitor cells prematurely. As in cortex, premature elevation of EGFRs promoted the depart ure of GE progenitors from the ventricular zone and their differentiation i nto astrocytes. Settling patterns of infected cells in the striatum, howeve r, differed from the patterns observed in cortex. In addition, the extent o f premature astrocyte differentiation reached similar levels in striatal ce lls, even in the presence of greater endogenous TGFa, These findings sugges t that additional factors play an important role in modulating EGFR-mediate d changes in cell fate. Together with previous studies in cortex, these obs ervations in the striatum indicate that a conserved mechanism involving dev elopmental changes in EGFR expression regulates cell fate and the timing of migration, Copyright (C) 2000 S. Karger AG, Basel.