Fig. 4

Afp18^G blocks cytokinesis leading to multinucleated cells.

(a) Cytoskeleton and cytokinesis analysed by time series of Afp18^G NxN (upper row) or Afp18^G (lower row) mRNA (0.5 pg per embryo each) injected embryos at dome stage (4.3 h.p.f.). Embryos were co-injected with mRNA encoding Lifeact-GFP (green) and H2B-dsRed (magenta; 100 pg per embryo each) labelling the F-actin cytoskeleton and the nuclei. Asterisk marks dividing blastomeres. Afp18^G NxN and Afp18^G mRNA-injected blastomeres complete microtubule mediated mitotic phases including chromosome segregation. Arrows indicate the actin ring contraction during cytokinesis, which is strongly affected in Afp18^G-dividing blastomeres. Confocal z-stack projection of 10-µm depth; scale bar, 10 µm. (b) Quantification of cytoplasmic versus cortical Lifeact-GFP integrated epifluorescence signal density at indicated developmental stages. Confocal image of Afp18^G NxN (left side) and Afp18^G (right side) injected embryo showing an example blastomere with manually defined areas of cortical (region depicted in between red and yellow selection) and cytoplasmic (region outlined by yellow selection) F-actin and analysed using Fiji-ImageJ software measure function (sphere, n=12 each; 30% epiboly n=12 each; 50% epiboly n=12 each). Scale bar, 10 µm. Values are average±s.e.m. Statistical significance was evaluated using Mann–Whitney test.