4
R. Nusse et al.
COSh)
Gl0:)
@I ZW3 1
Arm
~
.
~ / r pangolin/
~
lTCF
Fig. 1. WntfWg signaling
together with TCF to activate target genes (reviewed in Wodarz and
Nusse 1998).
1.5 Fz Molecules and Planar Polarity
fz and a variety of other genes, including dishevelled (dsh), belong to a
class of mutants with planar polarity (PP) phenotypes (Adler 1992;
Gubb and Garcia Bellido1982; Shulman et al. 1998). Loss of function
for these genes gives a similar phenotype of disoriented bristles and
hairs in the adult epidermis; these defects reflect PP defects in the
cytoskeleton of the epithelial cells that give rise to the overlying cuticular structure (Gubb and Garcia Bellido 1982). In mosaic clones, fz
mutations display both cell-autonomous and nonautonomous phenotypes, supporting the role of Fz protein in cell signaling (Vinson and
Adler 1987), and suggesting that it interacts with an extracellular ligand.
The nature of this ligand during PP signaling is not known, however.
While some overexpression studies have left open the possibility that wg