Models for Fz mediated activation of the cytoskeleton. Shown two different models for how the distal accumulation of Fz and other proteins could serve to activate the cytoskeleton to produce a hair or lateral. In panel A a Fz receptor complex accumulates at the distal side of the cell. The complex includes transmembrane proteins (such as Fz – filled black), known (such as Dsh – filled green) and unknown (filled red) cytoplasmic proteins. This receptor complex interacts with activators of the cytoskeleton (filled blue) leading to the production of a hair in the region where Fz preferentially accumulates. In panel B is an alternative model that can account for our results with laterals. As in A, a Fz receptor complex accumulates along the distal edge of the cell. This complex activates a signal transduction pathway (filled purple), which leads to the production of a diffusible signal. At some distance away this signal stimulates activators of the actin cytoskeleton promoting the formation of a lateral.