The frizzled (fz) gene is required for the development of distally pointing hairs on the Drosophila wing. It has been suggested that fz is needed for the propagation of a signal along the proximal distal axis of the wing. The directional domineering non-autonomy of fz clones could be a consequence of a failure in the propagation of this signal. We have tested this hypothesis in two ways. In one set of experiments we used the domineering non-autonomy of fz and Vang Gogh (Vang) clones to assess the direction of planar polarity signaling in the wing. prickle (pk) mutations alter wing hair polarity in a cell autonomous way, so pk cannot be altering a global polarity signal. However, we found that pk mutations altered the direction of the domineering non-autonomy of fz and Vang clones, arguing that this domineering non-autonomy is not due to an alteration in a global signal. In a second series of experiments we ablated cells in the pupal wing. We found that a lack of cells that could be propagating a long-range signal did not alter hair polarity. We suggest that fz and Vang clones result in altered levels of a locally acting signal and the domineering non-autonomy results from wild-type cells responding to this abnormal signal.

Adult Drosophila are decorated with several types of polarized cuticular structures, such as hairs and bristles. The morphogenesis of these takes place in pupal cells and is mediated by the actin and microtubule cytoskeletons. Mutations in flare ( flr) result in grossly abnormal epidermal hairs. We report here that flr encodes the Drosophila actin interacting protein 1 (AIP1). In other systems this protein has been found to promote cofilin-mediated F-actin disassembly. In Drosophila cofilin is encoded by twinstar (tsr). We show that flr mutations result in increased levels of F-actin accumulation and increased F-actin stability in vivo. Further, flr is essential for cell proliferation and viability and for the function of the frizzled planar cell polarity system. All of these phenotypes are similar to those seen for tsr mutations. This differs from the situation in yeast where cofilin is essential while aip1 mutations result in only subtle defects in the actin cytoskeleton. Surprisingly, we found that mutations in flr and tsr also result in greatly increased tubulin staining, suggesting a tight linkage between the actin and microtubule cytoskeleton in these cells.T HE actin cytoskeleton plays conserved and key roles in a variety of cellular activities in eukaryotes, such as cell migration, endocytosis, cytokinesis, and cell shape changes

The glass shrimp, Palaemonetes vulgaris changes to match the color of its background by a rapid, so-called physiological color change and a much slower, morphological color change. Apparently both are controlled by hormones, but the rapid color change is mediated by translocations of pigments within stellate cells called chromatophores, whereas the slow color change is effected by selective increases in certain types of chromatophore pigments. The large, dark chromatophores of the ovary were isolated intact and shown to be polychromatic (perhaps four pigments) by correlating light and electron microscopy. Incubated chromatophores supplied with crude extracts of certain neurosecretory tissues exhibit centripetal movement of pigment equivalent to that observed in vivo when a prawn is transferred from a dark-colored background to a light-colored background. Centripetal translocation of pigment is not inhibited in the chromatophores by preincubation in 10-3 M colchicine or vinblastine sulfate even though the vinblastine treatment elicits production of crystalline complexes of microtubular protein in place of the normal bundles of microtubules. Cytochalasin B (10 pg/ ml) blocks pigment migration reversibly, but does not disrupt microfilaments or other ultrastructural elements. Apparently, normal pigment aggregation depends on some function which is reversibly sensitive to cytochalasin B, and not on the impressive system of microtubules in these cells.Many crustaceans (Brown, '35a, b), fish (Fujii and N o d e s , '69; Green, '68; Spaeth, '13), amphibians (Bagnara et al., '68; Bikle et al., '66), and reptiles (Alexander and Fahrenbach, '69; Taylor and Hadley, '70) are capable of rapid changes in skin color in response to visual stimuli from the background. At the cellular level, rapid color changes are mediated by translocations of pigments within relatively large, dendritically-branched cells, often called chromatophores (Fingerman, '70b; Nicol, '60). Some decapod crustaceans such as the glass shrimp, Palaemonetes vulgaris are capable of changing to match essentially any color. As many as four basic pigments are involved, and the animal's color is determined by which pigment or combination of pigments is dispersed throughout the multibranched arms of its monochromatic and polychromatic chromatophores (Brown, '35a). The animal becomes quite transparent when all pigments are aggregated in the cell centers, leaving the arms of the chromatophores extended but devoid of pigment.The control of color changes in crustaceans involves the production and release of hormones, usually small peptides, by neurosecretory cells (Andrews et al., '71; Brown, '35a,b; Fingerman, '65, '70b; Perkins and Snook, '31, '32). Recently Fernlund and Josefsson ('72) isolated and determined the complete chemical structure of the neurosecreted hormone which effects the centripetal movement of red pigment in the prawn Pandalus borealis. They found that it is active in picogram amounts and demonstrated that it can be synthesized in the lab...