Loss of myosin VIII enhances actin filament formation. (A) A WT cell expressing Lifeact-mEGFP. White arrows point to the apical actin cluster. (B) A Δmyo8 mutant cell expressing Lifeact-mEGFP. White arrows point to an actin cluster forming and increasing in size over time. Green arrowheads indicate long actin bundles, which are more prevalent in Δmyo8 cells. Yellow arrows point to a group of long actin bundles migrating toward the cell apex. Images are maximum projections of z-stack acquired every 20 s. Bars, 5 µm. (C) From time-lapse acquisitions shown in A and B, a 7-µm diameter circle near the cell apex was tracked using TrackMate, and the mean intensity of Lifeact-mEGFP signal was plotted over time. A.U., arbitrary units. See also Video 9, Fig. S3, and Fig. S4.