Fig. 2: Ultrastructure of tunneling nanotubes (TNTs).

a The workflow of serial section CLEM tomography used to visualize 3D ultrastructure of stromal TNTs. b Correlative light and c electron microscopy (CLEM) of the same area from 300 nm sections were imaged by bright field b (upper) and fluorescence microscopy (lower; WGA—stained). View of corresponding tomography stack visible of marked ROI (purple and green frames) showing the presence of TNTs with open ends providing continuity with the cell body (yellow arrows). Possibly closed TNT is indicated with black arrow. Scale bar = 20 μm (b), 2 μm (c—upper left), 500 nm (c—bottom left and right). d Fluorescence image of one thick TNT (left) and tomography of ROI (green frame) showing the bunches of single TNTs. Scale bar = 2 μm (left image), 500 nm (middle and right images). e Transmission electron microscopy (left) of the TNT with visible bulge (left, blue frame) with corresponding electron tomography view show cellular vesicles present inside a TNT. Scale bar = 500 nm