Fig. 5. Increased apoptosis in vnd-null mutant embryos at embryonic stage 12. Laser confocal microscopy, reconstructions of optical sections, lateral views. (A-C,G,H) Embryos at early stage 12; average maximal extent of lab-expressing domain in wild-type embryos is outlined (white line, arrow) and projected onto each figure in top row. (D-F,I,J) Embryos at late stage 12; average maximal extent of lab-expressing domain in wild-type embryos is outlined (white line, arrow) and projected onto each figure in bottom row. (A,D) Wild type double-immunolabelled with anti-NRT (green) and anti-LAB (red) showing lab-expression domain (arrow). (B,E) P{ry⁺ 7.31 lab-LacZ} in wild-type background. Double-immunolabelling using anti-NRT (green) and anti-ßGAL shows that 7.31 lab-LacZ reporter construct mimics endogenous lab expression. (C,F) P{ry⁺ 7.31 lab-lacZ} in vnd-null background. Double-immunolabelling using anti-NRT (green) and anti-ßGAL reveals extent of lab expression domain, as assayed by 7.31 lab-lacZ reporter construct. (G,I) Wild-type double-immunolabelled with anti-LAB (red) and TUNEL staining (green) showing low level of apoptotic activity in lab domain. (H,J) vnd-null mutant; anti-LAB immunolabelling (red) and TUNEL staining (green) showing increased level of apoptotic activity in lab expression domain at early stage 12. (K) Quantitation of TUNEL-positive cells and of ß-galpositive 7.31 lab-lacZ-expressing cells detectable in wild-type and vnd mutant background. Values are means of n=17 preparations counted in each case: wt TUNEL=10, vnd TUNEL=20; wt cells=43, vnd cells=27. Standard deviations are indicated as bars (P<0.000005 each) of Student's t-test are indicated as stars (^**). By early stage 12, the number of TUNEL-positive apoptotic cells in vnd mutant tritocerebrum are significantly increased; by late stage 12, number of lab-lacZ expressing cells in vnd mutant tritocerebrum are significantly reduced.