Fig. 3.
BMP signaling promotes growth, delamination and migration of secondary cells. (A–D) Images of accessory glands from 6- to 7-d-old virgin males expressing nuclear GFP with (B and D) or without (A and C) an activated form of the BMP type I receptor Tkv (Tkv*) under the control of esgts F/O after a temperature shift at eclosion. Preparations were stained with TRITC-phalloidin (red), DAPI (blue), and an antibody to the septate junction protein Fas3 (yellow). Secondary cells with increased BMP signaling are enlarged and have much larger nuclei than their neighbors (compare nuclei marked by arrows in B vs. A); some cells detach from the basement membrane (cell marked in D is almost completely detached). (E) Relative size (± 2× SEM) of secondary cell nuclei versus surrounding main cell nuclei was determined for 6-d-old normal males and males with altered BMP signaling in secondary cells, expressing activated Tkv, Dad, or an RNAi against Med. *P < 0.001, n = 5 glands, one-way ANOVA. (F–I) A subset of adult secondary cells overexpressing activated Tkv under esgts F/O control in an 11-d-old virgin male delaminates and migrates proximally (green arrow). (G–I) High-magnification view of the gland marked in F, showing asymmetric actin accumulation at the cell surface in apical section (arrows in G) and basal contact with the glandular epithelium (I) [see also confocal z-section (H) along the line drawn in G and I; the epithelium is at the bottom of each panel in H). [Scale bars: 20 μm (A and B), 10 μm (C and D), 200 μm (F), and 25 μm (G–I).]