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. Author manuscript; available in PMC: 2011 Sep 14.
Published in final edited form as: Dev Cell. 2010 Sep 14;19(3):402–412. doi: 10.1016/j.devcel.2010.08.014

Figure 4. Actomyosin Dynamics and the Coordination of Protrusion Formation.

Figure 4

A. F-actin dynamics during protrusion formation. Top panel: 3-D projection stills, left side views. Plasma membrane is shown in red F-actin in green (Lifeact::GFP). Arrows point at the anterior and dorsal protrusions of ABpl. Lower panel: As above, however an embryo imaged ventrally. Arrows indicate the lamellipodium of MS during maximal extension (2’) and during disassembly (4’). For details and a schematic see Movie S5 and Figures S3A and B. B. Non-muscle myosin II dynamics during cell movement. 3-D projection stills, left side views. Plasma membrane is shown in red, cortical non-muscle myosin in green (NMY-2::GFP). Arrows point to the EMS furrow. Asterisks (timepoint 4’) indicate NMY-2 accumulation in the growing anterior filopodia of ABpl. C. ABpl forms a ventral protrusion onto MS. Upper panel: Cartoon depicting the embryo’s left side at the time when ABpl has formed its protrusions. Lower panel: 3-D projection stills, left side views showing only the ventral protrusion of ABpl as indicated by the boxed area in the cartoon. Arrows point to the tip of the protrusion. D. ABpl’s ventral protrusion is triggered by EMS cytokinesis. Left panel: 3-D projection stills, left side views with plasma membrane (red) and nuclei (green) fluorescently labeled. In the lower panel, the EMS nucleus in the embryo was irradiated to delay division. Arrows point to the location where ABpl’s ventral protrusion forms. Asterisks point to ABpl’s anterior filopodia. Middle panel: Quantification of ABpl’s displacement in both anterior and ventral directions and of its longest filopodium in wt embryos and embryos where EMS nucleus was irradiated (n=6, respectively, mean +/− SD). Right panel: Impairment of ABpl’s ventral displacement correlates with the degree of EMS division delay. Gray lines indicate the dorsal and ventral boundary of an embryo. Black and red lines represent the position of ABpl’s nucleus over time. Arrows indicate the timepoint when the furrow appears in EMS. Note that when EMS does not divide during the lifetime of ABpl, ABpl essentially does not move ventrally (solid red line). For details on cell-cell contacts see Figure S4.