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Vol. 17, Issue 9, 3930-3939, September 2006
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*Department of Biology, Washington University, St. Louis, MO 63130; and
Laboratory of Developmental Biology, Institute of General and Molecular Biology, Nicolaus Copernicus University, 87-100 Torun, Poland
Submitted September 21, 2005;
Accepted June 27, 2006
Monitoring Editor: David Drubin
Drosophila melanogaster bristle development is dependent on actin assembly, and prominent actin bundles form against the elongating cell membrane, giving the adult bristle its characteristic grooved pattern. Previous work has demonstrated that several actin-regulating proteins are required to generate normal actin bundles. Here we have addressed how two actin regulators, capping protein, a barbed end binding protein, and the Arp2/3 complex, a potent actin assembly nucleator, function to generate properly organized bundles. As predicted from studies in motile cells, we find that capping protein and the Arp2/3 complex act antagonistically to one another during bristle development. However, these proteins do not primarily act directly on bundles, but rather on a dynamic population of actin filaments that are not part of the bundles. These nonbundle filaments, termed snarls, play an important role in determining the number and spacing of the actin bundles. Reduction of capping protein leads to an increase in snarls, which prevents actin bundles from properly attaching to the membrane. Conversely, loss of an Arp2/3 complex component leads to a loss of snarls and accumulation of excess membrane-attached bundles. These results indicate that in nonmotile cells dynamic actin filaments can function to regulate the positioning of stable actin structures. In addition, our results suggest that the Arpc1 subunit may have an additional function, independent of the rest of the Arp2/3 complex.
This article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E06-06-0500) on July 5, 2006.
Address correspondence to: Kathryn G. Miller (miller{at}biology.wustl.edu)
Abbreviations used: APF, after puparium formation; Arp2/3, actin-related protein 2/3; cpb, capping protein beta; SEM, scanning electron microscopy; WASp, Wiscott Aldrich Syndrome protein.
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