Cell-pattern disordering during convergent extension inDrosophila

drops from 0.65 to 0.38. The fraction of fourfold vertices (four edges meeting) increases from 2% to 8%. Quantitative analysis of interface orientations reveals that the initial degree of hexatic edge-orientational order essentially disappears during the course of convergent extension. The degree of cell-pattern disordering in the two mutants resembles distinct stages in the wild type and correlates with the extent of axis elongation.