The growth ofDrosophilabristles and laterals is not restricted to the tip or base

Abstract

The highly elongated bristles of Drosophila have proven to be a valuable model system for studying cellular morphogenesis. Extending bristles contain a series of large bundles of actin filaments juxtaposed to the plasma membrane and centrally located microtubules. Models to explain the extension of the bristle have principally focused on the assembly of actin filaments at the distal tip of the bristle. We have used time-lapse observations of wild-type and mutant bristles and the related arista laterals and come to the conclusion that growth takes place throughout the growing cellular extension. This distributed growth can explain the behavior of split laterals and the shape changes seen at the tip during bristle and lateral outgrowth. Inhibitor studies suggest that the microtubule cytoskeleton is essential for maintaining the highly biased axial growth of these structures. We have used fluorescence recovery after photo-bleaching to study the dynamics of the cytoskeleton during bristle growth. Our experiments show that actin bundles in growing bristles are quite stable and move in a retrograde fashion. The bristle microtubules are less stable. The retrograde movement of the peripheral actin appears to be counterbalanced by the distally directed movement of cytoplasm in the center of the bristle.

spn-Fencodes a novel protein that affects oocyte patterning and bristle morphology inDrosophila

“…Whereas actin assembly is crucial for bristle cell elongation, MTs must provide other functions, such as providing bulk to the bristle cytoplasm, as well as playing a role in vesicle transport. It has also been shown that MT antagonists such as vinblastine and colchicine resulted in a decreased axial length and a compensatory increase in width, so that the volume of the bristle was not significantly changed (Fei et al, 2002). These data suggest that the MT cytoskeleton is of central importance for growth to be polarized in the axial direction (Fei et al, 2002).…”

“…It has also been shown that MT antagonists such as vinblastine and colchicine resulted in a decreased axial length and a compensatory increase in width, so that the volume of the bristle was not significantly changed (Fei et al, 2002). These data suggest that the MT cytoskeleton is of central importance for growth to be polarized in the axial direction (Fei et al, 2002). Mutations in the Dynein heavy chain resulted in shorter and thicker bristles (Gepner et al, 1996); mutations in kinesin also resulted in shorter and thicker bristles, and the tips of bristles were often contorted, exhibiting flattened, flared or twisted tips (Brendza et al, 2000).…”

Cytoskeletal dynamics and cell signaling during planar polarity establishment in theDrosophilaembryonic denticle

“…Studies of cytoskeletal regulation in the larger adult sensory bristles may guide this. EM studies, the use of cytoskeletal inhibitors, and FRAP, which proved informative in studies of wing hairs and bristles (Fei et al, 2002;Tilney et al, 1995;Tilney et al, 1996;Tilney et al, 2000a;Turner and Adler, 1998), may reveal how actin in denticles is assembled. Finally, it will be important to study in denticles additional actin regulators that regulate bristle development (Hopmann and Miller, 2003;Wahlstrom et al, 2001).…”

Dusky-like functions as a Rab11 effector for the deposition of cuticle duringDrosophilabristle development

“…Polarized extensions of epidermal cells, such as the sensory bristles, arista laterals and wing hairs of Drosophila melanogaster, are good model cell types for studying the processes that govern cytoskeleton-mediated morphogenesis (Fei et al, 2002;Guild et al, 2005;Tilney et al, 2004;Tilney et al, 1995;Tilney and DeRosier, 2005;Turner and Adler, 1998). However, little is known about the mechanisms that mediate membrane and protein transport during the growth of these structures.…”

“…Time-lapse studies have shown that, except for the initial stages of bristle development when growth is primarily isotropic, bristle growth is highly polarized in the axial direction (Fei et al, 2002). A variety of genetic and inhibitor studies argue that actin and microtubules play different roles in bristle growth (Cant et al, 1994;Fei et al, 2002;He and Adler, 2001;Petersen et al, 1994;Tilney et al, 2000a;Turner and Adler, 1998).…”