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Fig. 3 Gβγ signaling regulates actin cytoskeleton dynamics through RhoGTPase Rac. (A-D) Snapshots from epifluorescence time-lapse movies taken of embryos at 8-10 hpf, with actin cytoskeleton dynamics revealed using Lifeact-GFP labeling, in wild-type PGCs and PGCs expressing Gαt or Gγ2C68S (supplementary material Movie 3). White arrows indicate actin brushes; arrowheads indicate blebs. Numbers follow the same bleb. Actin labeling is not obvious in newly formed blebs (yellow arrowheads), but becomes prominent when blebs begin to shrink (red arrowheads). (E-I) Rac activity of PGCs expressing a cytosolic RacFRET biosensor, as determined by time-lapse analysis at 8-9 hpf. (E-H) Pseudocolored images of PGCs showing the ratio of emission from yellow fluorescent protein (YFP) to emission from cyan fluorescent protein (CFP). Wild-type PGCs during the run or tumbling phase (E,F; supplementary material Movie 4); PGCs expressing Gγ2C68S or wild-type Gβ1γ2 (G,H; supplementary material Movie 5). Scale bars: 10 μm. (I) Average Rac activity (mean YFP/CFP emission ratio for the whole cell) in control PGCs and in PGCs expressing Gγ2C68S, dnRac or Gβ1γ2. Total number of PGCs analyzed is indicated. *P<0.01 versus control. Data are mean+s.e.m.