title: Influence of cell polarity on early development of the sea urchin embryo.
abstract: BACKGROUND
  Establishment and maintenance of cell polarity is critical for normal embryonic development. Previously, it was thought that the echinoderm embryo remained relatively unpolarized until the first asymmetric division at the 16-cell stage. Here, we analyzed roles of the cell polarity regulators, the PAR complex proteins, and how their disruption in early development affects later developmental milestones.
  
  
  RESULTS
  We found that PAR6, aPKC, and CDC42 localize to the apical cortex as early as the 2-cell stage and that this localization is retained through the gastrula stage. Of interest, PAR1 also colocalizes with these apical markers through the gastrula stage. Additionally, PAR1 was found to be in complex with aPKC, but not PAR6. PAR6, aPKC, and CDC42 are anchored in the cortical actin cytoskeleton by assembled myosin. Furthermore, assembled myosin was found to be necessary to maintain proper PAR6 localization through subsequent cleavage divisions. Interference with myosin assembly prevented the embryos from reaching the blastula stage, while transient disruptions of either actin or microtubules did not have this effect.
  
  
  CONCLUSIONS
  These observations suggest that disruptions of the polarity in the early embryo can have a significant impact on the ability of the embryo to reach later critical stages in development.
authors: Department of Biology, Boston College, Chestnut Hill, Massachusetts, USA.|Marine Biological Laboratory, Woods Hole, Massachusetts, USA.
authors: Kathleen S
authors: KS
authors: Moorhouse
authors: Department of Biology, Boston College, Chestnut Hill, Massachusetts, USA.|Marine Biological Laboratory, Woods Hole, Massachusetts, USA.
authors: Heather F M
authors: HF
authors: Gudejko
authors: UMR 7009, UPMC Sorbonne Universités, Centre National de la Recherche (CNRS), Observatoire Océanologique, Villefranche-sur-Mer, France.
authors: Alex
authors: A
authors: McDougall
authors: Department of Biology, Boston College, Chestnut Hill, Massachusetts, USA.|Marine Biological Laboratory, Woods Hole, Massachusetts, USA.
authors: David R
authors: DR
authors: Burgess
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology*; D047108:Embryonic Development / Q000502:physiology*; D009218:Myosins / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D012617:Sea Urchins / Q000196:embryology* / Q000378:metabolism
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D011493:Protein Kinase C; D009218:Myosins
keywords: PAR; actin; deuterostome; myosin; polarity; sea urchin