Fig. 4. Downregulation of ephrin A5 expression in the Pax6 mutant telencephalon. (A-H) Expression patterns of ephrin A5 (A,C,E,G) and Pax6 (B,F) in wild type (A-D) and Pax6 mutant (E-H) telencephalon. In situ hybridization was performed at E11.5 (A,B,E,F) and E12.5 (C,D,G,H) telencephalon. In wild type, ephrin A5 is expressed at the ventral part of the telencephalon (A,C). GFP-labeled cells stop at the PSB, corresponding to the expression border of ephrin A5 (white arrow in D). Open arrows in C,D indicate the PBS. In the Pax6 mutant, expression of ephrin A5 is reduced in the ventral part of the telencephalon (E,G), where the GFP-labeled cells invaded (arrowhead in H). (I-M) EphA receptor expression in the wild type E12.5 telencephalon. Expression of Eph receptors is detected by incubation with soluble-ephrin A5-Fc protein (I). No signal is detected with Fc control protein (J). (K-M) Immunohistochemistry with anti-EphA4 antibody in the embryo labeled by GFP plasmid electroporation. EphA4 is expressed in the dorsal and ventral parts of the telencephalon (K), including GFP-positive cells (L,M). LV, lateral ventricle. Scale bars: 500 µm in A,C,D,J; 200 µm in D; 20 µm in M.