Influence of cell polarity on early development of the sea urchin embryo. Issue 12 (25th September 2015)

• Record Type: Journal Article
• Authors: Moorhouse, Kathleen S.; Gudejko, Heather F.M.; McDougall, Alex; Burgess, David R.
• Is Part Of: Developmental dynamics. Volume 244:Issue 12(2015:Dec.)
• Page Start: 1469
• Page End: 1484
• Publication Date: 2015-09-25
• Subjects: deuterostome -- polarity -- PAR -- myosin -- actin -- sea urchin; Morphogenesis -- Periodicals; Anatomy -- Periodicals; Anatomie -- Périodiques; Biologie du développement -- Périodiques; 571.833
• DOI: 10.1002/dvdy.24337
• Languages: English
• ISSNs: 1058-8388

Abstract

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. Developmental Dynamics 244:1469–1484, 2015 . © 2015 Wiley Periodicals, Inc. Key Findings: PAR6, aPKC, CDC42, and PAR1 remain apical through the gastrula stage. aPKC is in complex with PAR6 and PAR1 and does not regulate micromere formation. The PAR complex is anchored in the cortex by myosin assembly. Disruption of early polarity impeded blastula formation. Inhibition of myosin light chain kinase affects actin localization and is mediated by Arp 2/3 nucleation.