Fig. 2

First and third cleavages predict the anteroposterior axis in P. miniata sea star embryo. A Representative images of P. miniata embryos injected with a lineage tracer at the 2- or 8-cell stage. One blastomere was injected with a mixture of Dextran-Alexa488 and mRNA coding for Histone-BFP either at the 2- or at the 8-cell stage. At the 8-cell stage, either one animal or one vegetal blastomere was injected, scored according to the position of the polar bodies. Embryos were then raised at 16C and imaged on an epifluorescence microscope at 30, 48 and 72 hpf. Scale bars: 50 μm. B Alignment of the first cleavage with the animal-vegetal axis. Embryos injected at the 2-cell stage were stained with cell mask orange and imaged in toto on a confocal microscope. The images were rendered in 3D and the angle formed between the clone and the animal-vegetal axis was measured. n= 27 embryos. Rayleigh test, ***: p-value < 0.001. C Quantification of the lineage-tracing experiments. One blastomere of P. miniata embryos was injected either at the 2- or 8-cell stages, discriminating between animal and vegetal blastomeres at the 8-cell stage based on the position of the polar bodies. Embryos were raised at 16C and the position of the injected clone scored at 26 hpf. n= 161 embryos, 4 experiments