Development

Ratcheting Toward Closure

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Science  28 May 2010:
Vol. 328, Issue 5982, pp. 1079
DOI: 10.1126/science.328.5982.1079-a

During Drosophila embryogenesis, there are many movements and rearrangements of cells, leading ultimately to the formation of tissues and organs. One such major morphogenetic event involves the retraction of the germ band, leaving a hole in the embryo that must be covered. Epithelial cells from both sides pull themselves up over the underlying amnioserosal layer to cover the exposed tissue in a process called dorsal closure. Because of the genetic tractability of the fly, the molecular mechanics of this event can be elucidated.

Cables consisting of actin and nonmuscle myosin participate in dorsal closure, and David et al. have probed the mechanics of cable assembly and its regulation. Apical constriction of the amnioserosa is seen to involve cyclic assembly and disassembly of apical actomyosin networks. The phase of the cycle is regulated by several PAR cell-polarity proteins; PAR complexes localized to the apical domain of the amnioserosa transiently associate with the pulsing actomyosin network. Specifically, the polarity protein Bazooka is involved in the timing of the actomyosin pulse and Par-6 and aPKC govern the interpulse periods. This work shows how polarity factors regulate actomyosin dynamics during morphological change in the developing fly.

Development 137, 1645 (2010).

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