Fig. 4. Branch integrity defects are not due to cell death or tracheal misspecification. (A) Single confocal section of a stage 14 embryo showing a few tracheal cells stained for caspase-3 (in red) and displaying an apoptotic shape (arrow). (B-D) When cell death is prevented under Egfr downregulation conditions, branch breaks (arrowheads) and cells attached by cytoplasmic extensions (arrows) are still detected. (E) Projection of several confocal sections showing the expression of DSRF at the tip of primary branches (arrows) and the visceral branch. (F) Under Egfr downregulation conditions, kni is normally expressed.