Fig. 3. Expression of EGFRs changes during development. At E13 (A,C) EGFR immunostaining is relatively low, but increases by E16 (B,D) in mouse telencephalon. The distribution of cells expressing a high level of EGFR immunoreactivity was graded in the E16 cortex (B),with more cells expressing a high level of staining in lateral regions (L) than in medial regions (M). Asterisk indicates corticostriatal sulcus. The distribution of EGFRs on the cell surface also changes. At E13, EGFR immunostaining was concentrated at the apical surfaces of cells lining the lateral ventricle (A,C), but at E16 it was distributed more uniformly over the cell surface (B,D). C,D are higher magnifications A,B, respectively. The cells that expressed a high level of EGFRs were seen in proliferative zones (B,D) and in migration pathways, including the intermediate zone (B,D), the lateral cortical stream (LCS) (F-I) and the rostral migratory stream (RMS) (E,J). E illustrates the RMS in a sagittal view, with the letter J indicating the approximate position of the image in J. OB, olfactory bulb. F illustrates the LCS migration route, with letters indicating the approximate positions of images in panels G-I (M and L refer to medial and lateral). G shows EGFR expression at the beginning of the pathway, near the lateral ventricle (corticostriatal sulcus), as the pathway curves around the lateral ganglionic eminence (LGE). H shows the LCS in the ventrolateral cortex, with EGFR-positive cells leaving to migrate radially to the cortical plate. I shows the LCS leading into the piriform cortex (P). J shows EGFR-positive cells in the RMS posterior to the olfactory bulb in a parasagittal section. All other sections are transverse.
