Fig. 2: PG cells extend actin- and tubulin-based filopodia.

a Flip-out clones randomly expressing the fluorescent marker RFP in PG cells extend membrane protrusions (see arrowheads in the inset). The image corresponds to a maximum projection of a Z-stack. b Flip-out clone expressing the membrane marker myr-GFP. Long filopodia are observed on the sub-BM side (arrowheads), while fewer and shorter filopodia are observed in a lateral plane. The YZ section reveals a long filopodium present in the sub-BM region (arrowhead). c Flip-out clone expressing the membrane marker PLC-GFP shows filopodia in the sub-BM region (arrowheads) but not in the lateral plane. d myr-GFP (left) or PLC-GFP (right) flip-out clones induced in the fat body. No filopodia are observed. e Two neighboring cells (RFP positive due to CoinFLP) express complementary GFP fragments (spGFP^1–10 or spGFP¹¹) using the GRASP technique. Reconstructed GFP signal is detected on the sub-BM side, revealing filopodia contact between the two neighboring cells (arrowheads). A GFP signal is also observed in the lateral plane, appearing as a thin stripe. f Flip-out clones expressing an RNAi against mys (RFP positive) in a PG stained for βPS (green). In the sub-BM plane, βPS-decorated endogenous filopodia appear as punctate signals resembling projections in two WT cells (RFP negative, arrowheads in the zoomed image). No filopodia are detected in the lateral plane. g Flip-out PLC-GFP clone expressing cofilin RNAi. In the sub-BM plane, long filopodia containing F-actin are observed (arrowheads). In contrast, no actin-based filopodia are detected in the lateral plane despite F-actin stabilization. h Flip-out clone marked by PLC-GFP and the actin reporter Lifeact-Ruby, which label filopodia (arrowheads). i Flip-out clone expressing RFP in a PG stained against αTub85E. Microtubules are present in the filopodia (arrowheads in the zoomed images). j ex vivo experiment showing filopodia tracking through myr-GFP expression. Blue, white, and red arrowheads indicate different filopodia over time. Pictures are representative (n = 276 filopodia across 15 PG). White scale bars: 20 μm; yellow scale bars: 5 μm. k Schematic representation of filopodia distribution in PG cells, showing the presence of F-actin, tubulin, and βPS.