Fig. 6. Co-transfection of Fgf8b/a with Ras^S17N. (A-F) Dorsal view (A) and lateral view (B), parasagittal section at the line indicated on (A) as (C) and (E) (C,E) of E10.5 brain co-electroporated with Fgf8b and Ras^S17N at the 10-somite stage. (D,F) higher magnification of (C,E, respectively). The swelling in the mesencephalic region and anterior metencephalic region of the experimental side have sulci on the surface, and look like cerebellum (A,B). Histologically, however, the swelling in the mesencephalon and the anterior metencephalon of the experimental side do not have an external granular layer, which is seen in the cerebellum of the control side (C,D), and has tectal architecture (E,F). The posterior part of the metencephalic region consists of cerebellar structure (arrowheads on E). Antero-posterior direction is indicated by the double-headed arrow on (B,E). Dorsal view (G,I) and horizontal section (H) of the brain co-electroporated with Fgf8a and Ras^S17N. The tectum has extended to the diencephalic territory (G,H). Tectum differentiated ectopically in the metencephalon (I, arrow). tel, telencephalon; di, diencephalon; tect, tectum; cer, cerebellum; egl, external granular layer; tect, tectum; ne, neuroepithelial layer; roman numbers on (F) indicate the tectal layers. Scale bars: 4 mm (A,B,C,E,G,H,I); 200 µm (D,F).