@article{10606,
  abstract     = {Cell division orientation is thought to result from a competition between cell geometry and polarity domains controlling the position of the mitotic spindle during mitosis. Depending on the level of cell shape anisotropy or the strength of the polarity domain, one dominates the other and determines the orientation of the spindle. Whether and how such competition is also at work to determine unequal cell division (UCD), producing daughter cells of different size, remains unclear. Here, we show that cell geometry and polarity domains cooperate, rather than compete, in positioning the cleavage plane during UCDs in early ascidian embryos. We found that the UCDs and their orientation at the ascidian third cleavage rely on the spindle tilting in an anisotropic cell shape, and cortical polarity domains exerting different effects on spindle astral microtubules. By systematically varying mitotic cell shape, we could modulate the effect of attractive and repulsive polarity domains and consequently generate predicted daughter cell size asymmetries and position. We therefore propose that the spindle position during UCD is set by the combined activities of cell geometry and polarity domains, where cell geometry modulates the effect of cortical polarity domain(s).},
  author       = {Godard, Benoit G and Dumollard, Remi and Heisenberg, Carl-Philipp J and Mcdougall, Alex},
  issn         = {2050-084X},
  journal      = {eLife},
  publisher    = {eLife Sciences Publications},
  title        = {{Combined effect of cell geometry and polarity domains determines the orientation of unequal division}},
  doi          = {10.7554/eLife.75639},
  volume       = {10},
  year         = {2021},
}

@article{8957,
  abstract     = {Global tissue tension anisotropy has been shown to trigger stereotypical cell division orientation by elongating mitotic cells along the main tension axis. Yet, how tissue tension elongates mitotic cells despite those cells undergoing mitotic rounding (MR) by globally upregulating cortical actomyosin tension remains unclear. We addressed this question by taking advantage of ascidian embryos, consisting of a small number of interphasic and mitotic blastomeres and displaying an invariant division pattern. We found that blastomeres undergo MR by locally relaxing cortical tension at their apex, thereby allowing extrinsic pulling forces from neighboring interphasic blastomeres to polarize their shape and thus division orientation. Consistently, interfering with extrinsic forces by reducing the contractility of interphasic blastomeres or disrupting the establishment of asynchronous mitotic domains leads to aberrant mitotic cell division orientations. Thus, apical relaxation during MR constitutes a key mechanism by which tissue tension anisotropy controls stereotypical cell division orientation.},
  author       = {Godard, Benoit G and Dumollard, Rémi and Munro, Edwin and Chenevert, Janet and Hebras, Céline and Mcdougall, Alex and Heisenberg, Carl-Philipp J},
  issn         = {18781551},
  journal      = {Developmental Cell},
  number       = {6},
  pages        = {695--706},
  publisher    = {Elsevier},
  title        = {{Apical relaxation during mitotic rounding promotes tension-oriented cell division}},
  doi          = {10.1016/j.devcel.2020.10.016},
  volume       = {55},
  year         = {2020},
}

@article{6631,
  abstract     = {The spatiotemporal organization of cell divisions constitutes an integral part in the development of multicellular organisms, and mis-regulation of cell divisions can lead to severe developmental defects. Cell divisions have an important morphogenetic function in development by regulating growth and shape acquisition of developing tissues, and, conversely, tissue morphogenesis is known to affect both the rate and orientation of cell divisions. Moreover, cell divisions are associated with an extensive reorganization of the cytoskeleton and adhesion apparatus in the dividing cells that in turn can affect large-scale tissue rheological properties. Thus, the interplay between cell divisions and tissue morphogenesis plays a key role in embryo and tissue morphogenesis.},
  author       = {Godard, Benoit G and Heisenberg, Carl-Philipp J},
  issn         = {0955-0674},
  journal      = {Current Opinion in Cell Biology},
  pages        = {114--120},
  publisher    = {Elsevier},
  title        = {{Cell division and tissue mechanics}},
  doi          = {10.1016/j.ceb.2019.05.007},
  volume       = {60},
  year         = {2019},
}

@inbook{6987,
  abstract     = {Cells are arranged into species-specific patterns during early embryogenesis. Such cell division patterns are important since they often reflect the distribution of localized cortical factors from eggs/fertilized eggs to specific cells as well as the emergence of organismal form. However, it has proven difficult to reveal the mechanisms that underlie the emergence of cell positioning patterns that underlie embryonic shape, likely because a systems-level approach is required that integrates cell biological, genetic, developmental, and mechanical parameters. The choice of organism to address such questions is also important. Because ascidians display the most extreme form of invariant cleavage pattern among the metazoans, we have been analyzing the cell biological mechanisms that underpin three aspects of cell division (unequal cell division (UCD), oriented cell division (OCD), and asynchronous cell cycles) which affect the overall shape of the blastula-stage ascidian embryo composed of 64 cells. In ascidians, UCD creates two small cells at the 16-cell stage that in turn undergo two further successive rounds of UCD. Starting at the 16-cell stage, the cell cycle becomes asynchronous, whereby the vegetal half divides before the animal half, thus creating 24-, 32-, 44-, and then 64-cell stages. Perturbing either UCD or the alternate cell division rhythm perturbs cell position. We propose that dynamic cell shape changes propagate throughout the embryo via cell-cell contacts to create the ascidian-specific invariant cleavage pattern.},
  author       = {McDougall, Alex and Chenevert, Janet and Godard, Benoit G and Dumollard, Remi},
  booktitle    = {Evo-Devo: Non-model species in cell and developmental biology},
  editor       = {Tworzydlo, Waclaw and Bilinski, Szczepan M.},
  isbn         = {9783030234584},
  issn         = {1861-0412},
  pages        = {127--154},
  publisher    = {Springer Nature},
  title        = {{Emergence of embryo shape during cleavage divisions}},
  doi          = {10.1007/978-3-030-23459-1_6},
  volume       = {68},
  year         = {2019},
}