Modulations of the cell cycle change mesendodermal cell movements. (A and B) Gastrulation phenotype caused by GemMO. Note the shortened body axis in embryos injected with GemMO. Arrowheads mark the anterior boundary of hypoblast. (C–H) Modulations of the cell cycle change the position of gsc-expressing cells in the 80% epiboly embryos. Arrowheads mark the anterior boundary of the gsc-expressing domain. (I) Schematic representation of the cotransplantation assay. Green and red indicate transplanted green and red fluorescent donor cells, respectively. (J–Q) The cell cycle coordinates mesendodermal cell movements through apoptosis and Snail1a. Similar to the transplanted cells with p21 knocked down (O), GemMO led to delayed movements of transplanted cells (J), which was rescued by mrGem mRNA (K), Cdt1MO (M), and Snail1a mRNA (Q) but not by Gem* mRNA (L). Transplanted cells overexpressing geminin dispersed in the acceptor embryo (N), which was rescued by the coinjection of p53MO in donor embryos (P). Bars, 100 µm.