Fig. 3: ER-associated actin is present at the site of mitochondrial fusion.

a, b Quantification of fission (Fis.) and fusion (Fus.) events associated with ER. Cells were transfected with mCherry-ER and mito-GFP. Each point represents an individual cell, with 15 cells quantified in 4 independent experiments. a ER-Positive events (%), (b) Total events per cell. Bars show the average ± SD. c Representative fusion event showing the enrichment of AC-ER at the fusion site (arrowhead). Cells were transfected with mCherry-mito (mitochondria, magenta) and AC-ER (actin, green). Scale bar 2 µm. d, e Quantification of fission (Fis.) and fusion (Fus.) events positive for AC-mito. Each point represents an individual cell, with 13 cells quantified in 3 independent experiments. d ER-Positive events (%), (e) Total events per cell. f AC-ER signal enrichment at fusion (Left) and fission (Right) sites in cells transfected as in (c). Signal intensity at the event site relative to an adjacent site on the ER network was quantified for AC-ER (AC) and mCherry-ER (mCh). Each point represents an individual cell, with 13 cells quantified in 3 independent experiments. Bars show the average ± SD. two-sided t-test. g Quantification of AC-ER signal associated with each of the fusing mitochondria (the stationary mitochondrion (Rec) and the mobile mitochondrion (Fus)) as well as with the fusion site one frame post-fusion (Post). Each point represents an individual cell, with 13 cells quantified in 3 independent experiments. Bars show the average ± SD. One-way ANOVA. h, i Kinetics of recruitment of AC-mito and AC-ER at the fusion site showing AC-ER recruitment relative to AC-mito (g) and recruitment of either marker relative to the time of fusion (h). Each point represents an individual event (20 events total in 4 cells within 3 independent experiments). two-sided t-test.