Intermediate filaments undergo end-to-end annealing. Sites of end-to-end annealing (red/green junctions) are marked with white arrowheads. Two examples (i and ii) are shown for each experiment. For clarity, we selected isolated filaments for most of the images. (a) Obtained by fusion of SW13 vim⁻ cells coexpressing mCherry-NFM and NFL with SW13 vim⁻ cells coexpressing GFP-NFM and NFL. (b) Obtained by fusion of SW13 vim⁻ cells coexpressing NFM-mCherry and NFL with SW13 vim⁻ cells coexpressing NFM-GFP and NFL. (c) Obtained by fusion of SW13 vim⁻ cells coexpressing mCherry-vimentin and untagged vimentin with SW13 vim⁻ cells coexpressing GFP-vimentin and untagged vimentin. (d) Obtained by photoactivation and bleaching of SW13 vim⁻ cells coexpressing mCherry-NFM, PAGFP-NFM, and NFL. (e) Excerpts from a video of a neurofilament in a cell formed by the fusion of an SW13 vim⁻ cell coexpressing NFM-GFP and NFL with an SW13 vim⁻ cell coexpressing NFM-mCherry and NFL (Video 1). (f) Obtained by fusion of SW13 vim⁻ cells coexpressing NFM and NFL with SW13 vim⁻ cells coexpressing NFH and NFL. 5 h after fusion, the cells were fixed and immunostained for NFH and NFM. (g) Obtained by fusion of SW13 vim⁺ cells stably expressing mCherry-vimentin with SW13 vim⁺ cells stably expressing GFP-vimentin. (h) The edge of a cell obtained by fusion of SW13 vim⁺ cells stably expressing mCherry-vimentin with SW13 vim⁺ cells stably expressing GFP-vimentin. (i) Frequency distribution of the number of annealing events per filament 2–5 h after fusion of SW13 vim⁻ cells coexpressing NFM-GFP and NFL with SW13 vim⁻ cells coexpressing NFM-mCherry and NFL (991 filaments counted in five cells). NF, neurofilament. Bars, 2 µm.