Spatially defined Dsh-Lgl interaction contributes to directional tissue morphogenesis.

The process of epithelial morphogenesis defines the structure of epidermal tissue sheets. One such sheet, the ventral epidermis of the Drosophila embryo, shows both intricate segmental patterning and complex cell organization. Within a segment, cells produce hair-like denticles in a stereotypical and highly organized pattern over the surface of the tissue. To understand the cell biological basis of this process, we examined cell shapes and alignments, and looked for molecules that showed an asymmetric distribution in this tissue. We found that apical polarity determinants and adherens junctions were enriched at the dorsal and ventral borders of cells, whereas basolateral determinants were enriched at the anterior and posterior borders. We report that the basolateral determinant Lgl has a novel function in the planar organization of the embryonic epidermis, and this function depends on Dsh and myosin. We conclude that apical-basal proteins, used to establish polarity within a cell, can be independently co-opted to function in epithelial morphogenesis.