Fig. 5. Disruption and cell mixing at the chick MHB following HH blockade. (A,B) Unlike EGFP controls (A), bilateral electroporation of Ptc1^loop2 (blue; B) disrupts WNT1 (brown, arrowhead) expression at the MHB. (C,D) Unlike controls (C), HH blockade (D) results in the broadening of FGF8 expression at the MHB (blue; compare the length of the double-headed arrows in C and D). (D) Note the ectopic mixing of FGF8+ (white arrowhead) and OTX2+ (brown, black arrowhead) cells. C and D were photographed at the same magnification. (E,F) Increased cyclin D1 expression within the MHB following bilateral Ptc1^loop2 electroporations. E and F are photographs of the same embryo demonstrating that all FGF8+ cells (arrows, brown) are also cyclin D1+. However, all ectopic cyclin D1+ (arrowhead) cells are not FGF8+ (see Fig. 2A, left side, for normal cyclin D1+ expression). bi, bilateral electroporation; EP, electroporated; HB, hindbrain; MHB, midbrain-hindbrain boundary; rFP, rostral floor plate.