Fig. 3

The position of smaller cells at 16-cell stage is biased toward the ventral side in P. miniata sea star embryos. A–D First and third cleavage in relation to the dorsoventral axis. Representative confocal image of a sea star larvae injected at the 2-cell stage (A) or 8-cell stage (C). One blastomere was injected with a mixture of Dextran-Alexa488 and mRNA coding for Histone-BFP at the 2-cell stage, raised at 16C, fixed at 72 hpf, stained with Draq5 to visualize all nuclei and imaged in toto on a confocal microscope. Quantification of the angles formed by the injected clone and the sagittal plane of the larva at 72 hpf is shown in B (2-cell; n= 30 embryos) and D (8-cell; n= 24 embryos). E–L Position of small cells in relation to the dorsoventral axis. (E) Representative confocal image of a sea star larva showing the clone derived by a small cell at the 16-cell stage. Oocytes were injected with mRNA coding for the photoconvertible protein Kaede ( ) and incubated ON at 16C. Oocytes were subsequently activated, fertilized and incubated until the 16-cell stage, when one of the 16-cell was photoconverted ( ) on a confocal microscope (405 nm laser). Embryos were raised at 16C for 72 hpf and then imaged live in toto on a confocal microscope. F Schematic representation of the clone shown in (E). Several views of the same embryo are drawn, to fully represent the position of the labelled clone in 3D. G–J Quantification of the positions of clones observed after the photoconversion of a random cell (G) or a small cell (I) at 16-cell stage and the angles of the same clones formed with the sagittal plane at 72 hpf (H, J). Random cells: n= 32 embryos; Small cells: n=29 embryos. Rayleigh test, *: p-value < 0.05; ns, not significant. Scale bars: 100 μm