Fig. 4. vnd and the anterior Hox gene labial act independently in tritocerebral neuromere formation. Laser confocal microscopy of stage 15 embryos, reconstructions of optical sections, lateral views. Arrows indicate tritocerebral region. (A) Wild-type embryonic brain immunolabelled with anti-HRP antibody (blue). (B) Wild-type embryonic brain triple-immunolabelled with anti-HRP (blue), anti-LAB (green) and anti-VND (red); co-expression of vnd and lab is seen in part of lab-expressing tritocerebral domain (arrow); A and B are from same section. (C) vnd mutant embryonic brain immunolabelled with anti-HRP (blue). (D) vnd mutant embryonic brain double-immunolabelled anti-HRP (blue) and anti-LAB (green); only a few cells remain in the tritocerebrum and express lab; C and D are from same section. (E) P{ry⁺ 7.31 lab-LacZ};;lab^vd1/lab^vd1: null mutant embryonic brain immunolabelled with anti-HRP (blue); no anti-HRP immunoreactivity is detected in tritocerebral domain. (F) P{ry⁺ 7.31 lab-LacZ};;lab^vd1/lab^vd1: null mutant embryonic brain triple-immunolabelled with anti-HRP (blue), anti-VND (red) and anti-ßGAL, revealing 7.31 lab-LacZ reporter (green). vnd expression is seen in a part of tritocerebral domain mutant for lab and expression overlaps with lab-lacZ specific reporter gene expression; E and F are from same section.