Fig. 3.

The developmental change in responsiveness to BMP4 does not depend on EGFRs. Explants of E16–E17 cortex from EGFR-null mice (−/−) and wild-type littermates (+/+) were infected with a control virus, and the proportion of cells that expressed the late astrocyte marker GFAP was determined after 3 d in the absence (−) or presence (+) of BMP4. *p = 0.009, comparing BMP4 with untreated −/− cells.