Fig. 6. Ephrin B2 protein is expressed at the ventral hypothalamic midline in both the Foxg1^-/- mutant and the wild type. (A,B,E,F) Wild type. (A,B) At E13.5, ephrin B2 expression is most widespread in the more dorsal structures in the developing forebrain and eye (e). Ventrally ephrin B2 is detected at the ventral hypothalamic (ht) midline (B shows area boxed in A at higher power). (E,F) At E16.5, ephrin B2 protein is detected at the optic chiasm (oc) where expressing cells contact the optic nerve (on). (F) Higher magnification of the optic chiasm. (C,D,G,H) Mutant. (C,D) At E13.5, ephrin B2 is expressed in the hypoplastic telencephalon (tel^*) and in the developing eye (see Fig. 5). Ephrin B2 is also detected at the hypothalamic midline (D shows area boxed in C at higher power). (G,H) At E16.5 ephrin B2 expression persists at the mutant optic chiasm where it contacts Ephb2-expressing axons (section in H is adjacent to the Ephb2 stained section shown in Fig. 5L). Paired arrows indicate the ventral hypothalamic midline. (A-D,F,G) Coronal sections with dorsal towards the top. (E,H) Horizontal sections with posterior towards the top. cc, cerebral cortex; vtel, ventral telencephalon. Scale bars: 200 µm in A,C,E; 50 µm in B,D,F-H.