Strategies to test for end-to-end annealing of intermediate filaments. (a) Schematic of the cell fusion strategy. (b) A cell obtained by fusion of SW13 vim⁻ cells coexpressing NFM-mCherry and NFL with SW13 vim⁻ cells coexpressing NFM-GFP and NFL and imaged 3.5 h after fusion. (c) Schematic of the photoactivation and bleaching strategy. (d) An SW13 vim⁻ cell coexpressing mCherry-NFM, PAGFP-NFM, and NFL imaged before bleaching and photoactivation (i), and immediately after bleaching and photoactivation before the filaments had mixed (ii). Bars, 10 µm.