Combined effect of cell geometry and polarity domains determines the orientation of unequal division
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, France
- Institute of Science and Technology Austria, Austria
Figures
Figure 1
Unequal cell division at the third cleavage of ascidian embryos creates larger vegetal blastomeres which inherit the centrosome-attracting-body (CAB).
(A) Brightfield images of vegetal view of an embryo from 8- to 64-cell stage. The double black arrows on the left side of the embryo mark sister cells and the dashed lines on the right side of the …
Figure 2 with 1 supplement
The spindles tilt at anaphase onset during unequal cell divisions (UCDs).
(A) Sagittal views showing spindle position at metaphase and anaphase onset at the 4-cell stage. Schematic illustration (left panel) of a 4-cell stage embryo with the imaging plane in a sagittal …
Figure 2—figure supplement 1
Spindle dynamics in anterior blastomeres in sagittal view.
(A) Plot of the spindle angle with the AV axis in anterior blastomere A3 measured on sagittal views (see Figure 3A) in metaphase and anaphase. Positive angle means that the mitotic spindles point …
Figure 3
Spindle tilting in an anisotropic cell geometry induces unequal cell division (UCD) by displacing the cleavage plane from the cell center of mass.
(A) Simulation of the effect of a tilted but centered spindle on the bisection of the cell. Schematic illustration of the simulations realized using real cell contour of anterior blastomeres from …
Figure 4 with 2 supplements
The vegetal cortex is a polarity domain lacking microtubule cortical pulling forces and is necessary for making larger vegetal blastomeres.
(A) Cortical pulling sites on astral microtubules at mitosis during the 4-cell stage observed as plasma membrane invaginations in embryos with a weakened cortex. Maximum projection (26 µm thick) of …
Figure 4—figure supplement 1
Membrane invaginations are abolished by depolymerizing microtubules.
Cortical pulling sites on astral microtubules at mitosis are abolished when microtubules are depolymerized during the 4-cell stage. Maximum projection (26µm thick) of confocal images of 4-cell stage …
Figure 4—figure supplement 2
Yolk distribution in oocyte and 4-cell stage; gastrulation phenotypes after zygote microsurgeries.
(A) Confocal fluorescence image showing section across an oocyte (animal on top) with the yolk granules stained with Bodipy 493/503 (1µg/µl, green). Scale bars, 20µm. (B) Confocal fluorescence image …
Figure 5 with 1 supplement
Decreasing cell shape anisotropy of the mitotic blastomeres changes the unequal cell divisions (UCDs).
(A) Left panel: brightfield images and corresponding 3D reconstruction (anterior blastomeres [A3] in blue, posterior blastomeres [B3] in red) of 4-cell stage embryos in mitosis either whole or after …
Figure 5—figure supplement 1
Cell sphericity during 4-cell stage; Blastomere identification and morphometric analysis of isolated blastomeres.
(A) Bright field images of vegetal view of an embryo during the 4-cell stage with anterior to the left (top left panel) and the corresponding 3D reconstructions with anterior blastomeres (A3) in …
Figure 6
Anisotropic cell shape influences the spindle interaction with polarity domains and together determines the orientation of unequal cell division (UCD).
(A) Schematic illustration (left panel) of a 4-cell stage embryo in sagittal view (anterior to the left, animal on top) showing the spindle interaction with the different cortical polarity domains. …
