Cellular retraction associated with lateral tkvQDclones. (A) Wild type Omb expression pattern. The inset shows the profile of fluorescence intensity in a stripe of cells (orange box) along the A/P axis. (B) Lateral tkvQDclones (arrowheads) up-regulate Omb to a level comparable to central endogenous Omb. (C) CD8-GFP control clones, labelled by anti-GFP staining (green), show normal phalloidin staining. (C') x-z scan through the same disc. (D) Lateral tkvQDclones, labelled by CD8-GFP co-expression (green), either form a fold at the clonal border (arrow) or retract cells toward the basal side within the clone (arrow head) as revealed by phalloidin staining. (D1 and D2) x-z scans through clones marked by arrow and arrowhead, respectively, in (D). The x-z sections presented in C', D1, D1', and D2 are derived from C and D, respectively, but are shown at a 1.5-fold higher magnification. D1 shows the retraction of cells at the clonal border and D1' shows loss of the apical microtubule web in retracted cells (arrow). (E) x-z scan through tkvQDclones. The apical microtubule web, stained by anti-α-tubulin (green), is reduced in the retracting cells (arrowheads). (F) x-z scan of UAS-tkvQDUAS-ombRNAi clone. Cell shape in this lateral clone (arrowhead) which is identified by the lack of Omb appears normal. The x-y position of the clone is shown in Additional File 2B. (G) Model of cell shape changes in clones with peripherally (left) and centrally (right) retracting cells. High local microtubule density (shown in green) is found both in the peripodial membrane (squamous epithelium) and the AMW of the underlying columnar epithelium. Mutant cells are rendered with blue, wild type cells with black outlines. The left cartoon visualizes that cellular retraction at the clone boundary also leads to non-autonomous attenuation of the AMW in the flanking wild type cells. Phalloidin staining is red in all panels.