Originally published as Genetics Published Articles Ahead of Print on April 3, 2007.

Genetics, Vol. 176, 891-903, June 2007, Copyright © 2007
doi:10.1534/genetics.106.069021

The Balance Between the Novel Protein Target of Wingless and the Drosophila Rho-Associated Kinase Pathway Regulates Planar Cell Polarity in the Drosophila Wing

SeYeon Chung*, Sangjoon Kim*,1, Jeongsook Yoon*, Paul N. Adler{dagger},2,3 and Jeongbin Yim*,3

* School of Biological Sciences, Seoul National University, Seoul 151-742, Korea and {dagger} Biology Department, University of Virginia, Charlottesville, Virginia 22903

2 Corresponding author: Biology Department, Gilmer Hall 245, University of Virginia, Charlottesville, VA 22903.
E-mail: pna{at}virginia.edu

Planar cell polarity (PCP) signaling is mediated by the serpentine receptor Frizzled (Fz) and transduced by Dishevelled (Dsh). Wingless (Wg) signaling utilizes Drosophila Frizzled 2 (DFz2) as a receptor and also requires Dsh for transducing signals to regulate cell proliferation and differentiation in many developmental contexts. Distinct pathways are activated downstream of Dsh in Wg- and Fz-signaling pathways. Recently, a number of genes, which have essential roles as downstream components of PCP signaling, have been identified in Drosophila. They include the small GTPase RhoA/Rho1, its downstream effector Drosophila rho-associated kinase (Drok), and a number of genes such as inturned (in) and fuzzy (fy), whose biochemical functions are unclear. RhoA and Drok provide a link from Fz/Dsh signaling to the modulation of actin cytoskeleton. Here we report the identification of the novel gene target of wingless (tow) by enhancer trap screening. tow expression is negatively regulated by Wg signaling in wing imaginal discs, and the balance between tow and the Drok pathway regulates wing-hair morphogenesis. A loss-of-function mutation in tow does not result in a distinct phenotype. Genetic interaction and gain-of-function studies provide evidence that Tow acts downstream of Fz/Dsh and plays a role in restricting the number of hairs that wing cells form.