The frizzled/stan Pathway and Planar Cell Polarity in the Drosophila Wing

Abstract

Drosophila has been the key model system for studies on Planar Cell Polarity (PCP). The rich morphology of the insect exoskeleton contains many structures that display PCP. Among these are the trichomes (cuticular hairs) that cover much of the exoskeleton, sensory bristles and ommatidia. Many genes have been identified that must function for the development of normal PCP. Among these are the genes that comprise the frizzled/starry night (fz/stan) and dachsous/fat pathways. The mechanisms that underlie the function of the fz/stan pathway are best understood. All of the protein products of these genes accumulate asymmetrically in wing cells and there is good evidence that this involves local intercellular signaling between protein complexes on the distal edge of one cell and the juxtaposed proximal edge of its neighbor. It is thought that a feedback system, directed transport and stabilizing protein-protein interactions mediate the formation of distal and proximal protein complexes. These complexes appear to recruit downstream proteins that function to spatially restrict the activation of the cytoskeleton in wing cells. This leads to the formation of the array of distally pointing hairs found on wings.

Cooperative functions of the two F-BAR proteins Cip4 and Nostrin in regulating E-cadherin in epithelial morphogenesis

“…Loss of nostrin alone does not affect wing hair formation, whereas overexpression of Nostrin results in a strong multiple wing hair phenotype, as recently found for Cip4 gain-offunction ( Fig. 2G,H ;Fricke et al, 2009). core proteins that define the position and number of emerging wing hairs (Adler, 2012). A key mechanism in the establishment of polarity along the distal-proximal axis is the asymmetric localization of the core PCP proteins, including Frizzled, Flamingo or Van Gogh at the apical surface of the wing cells, shortly before wing hair formation was initiated, ,26-28 h after …”

Planar cell polarity in development and disease

“…The robust readout of these bristles provided the foundation for genetic screens identifying PCP proteins that direct assembly of these structures through control of the actin cytoskeleton 2 . These structures also facilitated the use of mutant clones to explore signalling mechanisms, for example in the discovery of directional non-autonomy, which refers to directional non-autonomous effects of specific PCP mutations 70,71 .…”

The Atypical Cadherin Dachsous Controls Left-Right Asymmetry in Drosophila

“…In Drosophila, PCP is involved in the polarity of hair-like structures in many organs, including the wing, eye, abdomen, and notum (Adler, 2012;Lawrence et al, 2007;Lawrence and Casal, 2013;Matis and Axelrod, 2013;Singh and Mlodzik, 2012). The well-studied Drosophila PCP genes are known to belong to two major pathways: the ''core system'' and the ''global system'' (Axelrod, 2009;Goodrich and Strutt, 2011;Lawrence and Casal, 2013;Matis and Axelrod, 2013).…”