Fig. 6. HH blockade leads to a disruption of the DV boundary. (A) Ectopic PAX7 expression in the ventral midbrain after HH blockade. (B) Serrate 1 expression (blue), which is normally confined to the dorsal midbrain (tec) and to a thickening at the DV boundary (arrowhead), is perturbed in Ptc1^loop2 electroporations. (C) Absence of PAX7+ (blue) cells in the ventral midbrain of EGFP (brown)-electroporated explants. Note the presence of PAX7 (blue) expression in the tectum (tec). (D) Bilateral Ptc1^loop2 electroporation induces ectopic PAX7 expression in ventral midbrain explants with no associated tectal tissue. (E) EGFP misexpression (blue) near the DV boundary (broken line) fails to perturb PAX7 expression (brown). (F) Ptc1^loop2 misexpression (blue) near the DV boundary (broken line) induces ectopic PAX7+ (brown) cells, some non-autonomously (arrowhead). Arrow points to the upregulation of PAX7 in association with Ptc1^loop2 misexpression. III, third ventricle; bi, bilateral electroporation; EP, electroporated; HB, hindbrain; MHB, midbrain-hindbrain boundary; rFP, rostral floor plate; tec, tectum.