Extended Data Fig. 4: F-Cell specification is initiated by the tactile bristle.

(a-to-d) Left: diagrams depicting the cell ablations used to assess F-Cell recruitment by tactile bristles cells. The cells that were ablated at 36-38 hAPF are marked by black crosses. Middle: epidermal and tactile bristle cells visualized at 55 hAPF by the expression of Diap1-GFP (green) and neur > RFP. Right: diagrams summarizing the effects of each cellular ablation on F-Cell specification (n = 16 socket cells over 7 pupae; n = 11 shaft cells over 8 pupae; n = 12 neuron and sheath cells over 5 pupae; n = 13 socket and shaft cells over 4 pupae, from three independent experiments. The F-Cell is no longer detectable after simultaneous ablation of the socket and shaft cells (b) or ablation of the shaft cell alone (d). (e) Effect of N activity gain via downregulation of H on Diap1-GFP and neur > RFP expression patterns (neur > H^KD, right) within the bristle compared to control (left). (f) Diagrams depicting the differential N signalling within the differentiating socket and shaft cells (green and light blue) in controls (left), upon N activity gain in the shaft cell (middle) or upon N activity loss in the socket cell (right). (g) Top, left-to-right: brightfield images displaying the adult cuticular socket and hair shafts in controls, two socket-like structures upon N activity gain in the shaft cell, and two hair shaft-like structures upon N activity loss in the socket cell. Bottom, left-to-right: socket and shaft cells visualized by the expression of mCherry in the Diap1-GFP background (green) showing associated F-Cells in controls, lack of F-Cell next to a bristle composed of two socket-like cells, or enhanced Diap1-GFP in two cells next to a bristle composed of two shaft-like cells. Results are representative of three independent experiments. Scale bars: 5 μm. Full genotypes are listed in Supplementary Table 1.