Sci. Signal., 23 September 2008
Developmental Biology Creating Force from Destruction
Annalisa M. VanHook
Science Signaling, AAAS, Washington, DC 20005, USA
Dorsal closure in the fruit fly Drosophila melanogaster is the morphogenetic process by which the embryonic epidermis migrates dorsally over the extraembryonic amnioserosa to enclose the embryo in a continuous sheet of epidermis. Cells throughout each of these epithelial tissues participate in generating the mechanical forces that drive closure. As the epidermis spreads, the amnioserosa contracts, with most amnioserosal cells becoming internalized and some undergoing apoptosis. Toyama et al. (see commentary by Davidson) investigated the effect of apoptosis in the amnioserosa on closure. Transgenic expression of the antiapoptotic protein p35 in the amnioserosa slowed dorsal closure, whereas expression of the proapoptotic protein grim hastened the pace of closure. The authors examined the mechanical consequences of apoptosis in the amnioserosa and found that, as amnioserosal cells die, neighboring cells stretch to maintain the integrity of the sheet. These cell shape distortions generate tension that can contribute to contraction of the amnioserosa, thus identifying force generation as an unexpected consequence of apoptosis. The observation that inhibiting apoptosis slowed, but did not prevent, closure is consistent with the idea that no single process is entirely responsible for driving closure; rather, the required forces are generated by multiple processes distributed throughout the tissues.
Citation: A. M. VanHook, Creating Force from Destruction. Sci. Signal. 1, ec334 (2008).
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