Xenbase Image ID: 149557

Fig. 5. Activated Daam1 rescues defective cell behavior responsible for impaired convergent extension movements. (A) Extension of activin (Act)-treated animal caps is inhibited by expression of dominant negative Dsh (Xdd1) (1 ng of RNA), but this inhibition is rescued by C-Daam (100 pg of DNA) or DaamδDAD (100 pg of DNA) coinjection but not Daam1 (1 ng of RNA) coinjection in convergent extension assays. (B) Quantitation of the extension of animal cap explants in A; the number of caps scored (n) is shown at the top of each bar. (C) Expression of dominant negative Dishevelled (Xdd1) (1 ng of RNA) impairs polarization, elongation, and mediolateral alignment of dorsal mesodermal cells undergoing convergent extension movements. These induced defects in cell behaviors are rescued by coexpression of Xdd1 with C-Daam (100 pg of DNA) or DaamδDAD (100 pg of DNA) but not Daam1 (1 ng of RNA). Expression of C-Daam, DaamδDAD, or Daam1 does not interfere with cell polarization, elongation, or mediolateral alignment at these injected doses. Orientation of the explants is shown in the upper right: A, anterior; P, posterior; L, lateral; M, midline. (D and E) Quantitation of cell polarization and mediolateral orientation of cells from the studies of C; the numbers of cells examined are shown at the top of each bar. *, statistically significant value (P < 0.005). (F) A model for how Daam1 is activated. Daam1 exists in the cytoplasm as an autoinhibited protein via intramolecular interactions between the GBD and the DAD. Wnt stimulation induces a complex formation between Dvl and Daam1, and Dvl binds to the DAD, disrupting interactions between the amino and carboxyl regions of Daam1. The binding of Dvl thus relieves Daam1's autoinhibition, and Daam1 with its downstream effectors triggers Rho activation and cytoskeletal changes to regulate gastrulation. Image published in: Liu W et al. (2008) Copyright © 2008. Image reproduced with permission of the publisher and the copyright holder. This is an Open Access article distributed under the terms of the Creative Commons Attribution License. Larger Image Printer Friendly View

Return to previous page