Fig. 7

Ectopic zOtx1-GR expression causes cell adhesion when activated with dexamethasone. Embryos were co-injected at the 16-cell stage with GFP and zOtx1-GR RNAs and allowed to develop until 8 hpf at which time dexamethasone was added to the embryo medium at a final concentration of 20 μm. The positions of fluorescent cells in these embryos were then followed over the next 5.25 h. The images show the time course of a single embryo photographed at 9.5 (A), 10.25 (B), 11.0 (C), 11.75 (D), 12.5 (E), and 13.25 (F) hpf. Small islets of loose aggregates were formed from dispersed fluorescent cells in the first 2 h after dexamethasone activation (A, B). Later, the aggregates merged into larger arrays of cells that showed a more tightly packed organization (C–F). The embryo is shown in lateral view with animal pole to the top and dorsal side to the right. Time lapse studies of six embryos examined during this interval all showed a similar time course of the activation of aggregation. Some of the aggregates and cells from which they were formed are indicated with arrowheads and asterisks. Rates of convergence of the aggregates (see text) were determined from positions at 11.75 and 12.5 hpf. Scale bar, 100 μm (all at same magnification).