Figure 1. Dynamics of EFF-1 and the Actin Cytoskeleton during the Epithelial seam-
hyp7 Cell Fusion in C. elegans Larvae(A) Time-lapse images of nuclear localization signal (NLS) in the
hyp7 cell (upper) and the plasma membrane in seam cells during seam-
hyp7 cell fusion (bottom).0 min, fusion pore formation. The white arrowheads show the fusing cells. The yellow asterisks show the non-fusing seam cells. A schematic cartoon is shown onthe left.(B) GFP fluorescence intensity ratio of the cytoplasm between V.a and
hyp7 (left) or of the plasma membrane between V.a and V.p (right).(C) Quantification of the diffusion time of NLS-GFP in
hyp7 or of GFP-tagged membrane and histone in seam cells. n = 13. SE, seam cells.(D) Schematics of intercellular fusion between the anterior daughter cell of the seam cell (V.a) and the
hyp7 cell. 0 min: the birth of V.a or the completion of V cellcytokinesis.(E-G) Fluorescence time-lapse images of GFP-tagged EFF-1 (E), F-actin (F), and VAB-10A (G) during the seam-
hyp7 cell fusion. Asterisks, V.a.(H and I) Quantification of the EFF-1 and VAB-10A fluorescence ratios during seam-
hyp7 cell fusion. Birth: the completion of V cell cytokinesis; enrichment in (H)and (I): the outline fluorescence intensity on the V.a membrane is >1.5 times higher than that of the sister non-fusing V.p cell; fusion: fusion pore formationindicated by the loss of mCherry::PH fluorescence in V.a. The fluorescence intensity ratio is quantified between V.a and V.p. n = 15. (I) Quantification of F-actin,VAB-10A, and EFF-1 enrichment times after V cell cytokinesis. n = 11-27.(J) A cross-sectional view of seam cells (red), the
hyp7 cell (blue), and F-actin (green) in a larva. D, dorsal; V, ventral; L, left; R, right. Based on the Worm Atlas
(http://www.wormatlas.org, chapter: Epithelial System Seam Cells).(K) Left: still images of GFP-tagged moesinABD and mCherry-tagged plasma membrane in the seam cell. Upper, lateral view; bottom, cross-sectional view.Schematic cartoon is shown on the right. Arrowhead shows the enrichment of F-actin in cross-sectional view. Scale bar, 5 um.(L) Time-lapse images of F-actin (GFP::moesinABD) and mCherry::PH in seam cell, and the F-actin sheath (TagBFP::actin) in
hyp7 cell. 0 min, fusion poreformation.(M) Duration time of EFF-1 and F-actin in
hyp7 or seam cell on the cell cortex. n = 11-30.Scale bars, 5 mm in (A), (E) to (G), and (L). Error bars indicate the mean +- SD. *p < 0.05, **p < 0.01, ***p < 0.001 based on Student's t test; n.s., not significant. Seealso Figure S1; Movies S2 and S3.