Fig. 1: Epidermal F-Cells associate with differentiating tactile bristles.

a, Left to right: diagram of the adult fly highlighting the tactile bristles decorating the dorsal body surface, SEM image showing the hairy epidermal cuticle of the abdomen, bright-field image displaying the innervation of the tactile bristles, and close-up view of the cuticular socket and hair shaft structures showing the connection of the dendrite to the base of the tactile organ. PNS neurons are marked by GFP expression under nSyb-GAL4 control (nSyb > GFP, yellow). b, Expression of the nuclear marker H2B::RFP under the control of neur-GAL4 (neur > RFP, magenta) showing the time course of neur expression. Diagrams show each cell type as bristle differentiation progresses. By 55 hAPF, a fifth neur > RFP expressing cell, the F-Cell, is visible next to each organ (arrowhead). c, Left to right: tactile bristle and the F-Cell (arrowhead) marked by the expression of neur > RFP (magenta) and the socket cell-specific reporter Su(H)-ASE5-GFP (green), diagram showing the position of the F-Cell relative to the bristle cells, and morphology of the tactile bristle and epidermis by co-expression of neur > RFP (magenta) and the ubiquitous microtubule marker Jupiter::GFP (green). Note that the F-Cell lies between the socket cell and the shaft cell. d, Simultaneous expression of neur > RFP with the ubiquitous nuclear marker Ubi-GFP.nls (green) shows that the F-Cell is part of the epidermis surrounding the bristle. e, Tactile organ visualized by co-expression of neur > RFP and the membrane-localized GFP mCD8-GFP, revealing association of the F-Cells (arrowhead) with the tactile bristles and the socket cell. Results are representative of three independent experiments. Scale bars, 150 μm, 20 μm, 5 μm (a) and 5 μm (b–e). Full genotypes are listed in Supplementary Table 1.