(A) Confocal z-projections of stills from a time-lapse of a WT embryo expressing mGfp starting at 7hpf. Lateral view focused on the margin. Green shaded cells shrink the EVL-YC junction and intercalate into submarginal zones. Orange shaded cells establish new cell-cell contacts following intercalation events (denoted by red dotted line). Circle denotes shared vertex with underlying yolk cell. Scale bar 20 μm (A’) Confocal z-projection time-lapse of WT embryo labeled for F-actin; (Fire-LUT) (Gfp-Utrophin) starting at 7hpf; lateral view; scale bar 20 μm. (B) Confocal z-projection of stills from a confocal time-lapse starting at 7hpf of an MZrab25b embryo expressing membrane-Gfp. Purple shaded cells exit EVL marginal region. Scale bar 20 μm (B’) Confocal z-projection of stills from time-lapse starting at 7hpf of an MZrab25b embryo labeled for F-actin (Fire-LUT) (Gfp-Utrophin); scale bar 20 μm. Shaded cells denote an EVL circumferential stretching event. Scale bar 20 μm. (C–D) EVL-YC mean contact length or shortening rate over time in rearranging EVL marginal cells in WT (N = 5) and MZrab25b embryos (N = 5). Mean:SEM. Each color indicates a separate trial of a single embryo. Each line represents the average of the contact length or junction shrink rate in each trial (n = 2–5). (E) Resolution times following formation of EVL-YC multicellular vertices. Mean: SEM. WT (n = 20,N = 4) and MZrab25b (n = 12,N = 5), unresolved MZrab25b vertices (red) (n = 6,N = 5). Mann-Whitney, *p<0.05.
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