Localization of zipper is dependent on Cdc42 activity. (A–C) Shown are still frames from time-lapse movies of embryos of the indicated genotypes. CB-specific expression of Zipper^GFP and Cdc42 overexpression using tinCΔ4-Gal4. The midline is indicated by the white vertical lines. Note that overexpressed Zip^GFP can form aggregates (intense blobs) that are absent in wild-type tissue. (D–F) Endogenous Zipper localized in fixed heart tissues of the indicated genotypes. (A and D) In wild-type embryos, Zipper concentrates at the CB leading edge in a dynamic, cyclical pattern (arrowheads). It accumulates into a single focus at the leading edge (90–150 s) that dissolves later on. (B and E) Expression of Cdc42^N17 prevents correct localization of Zipper and inhibits foci formation. Asterisks mark positions of selected CB nuclei. (C and F) Upon overexpression of Cdc42^V12, Zipper still accumulates toward the leading edge but is less concentrated (arrows).