Strategies to test for subunit incorporation along intermediate filaments. (a) Schematic of the cell fusion and photoactivation strategy. (b) A cell obtained by fusion of SW13 vim⁻ cells coexpressing NFL-PAGFP and NFM with SW13 vim⁻ cells coexpressing NFL-mCherry and NFM and imaged before photoactivation (4.5 h after fusion; i) and immediately after photoactivation (ii). (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 (ii). Bars, 10 µm.