Three-dimensional epithelial morphogenesis in developing eggshells. Miriam Osterfield¹, XinXin Du¹, Trudi Schüpbach^1,2, Eric Wieschaus^1,2, Stanislav Shvartsman¹. 1) Princeton University, Princeton, NJ; 2) Howard Hughes Medical Institute, Princeton, NJ.

   Morphogenesis of the respiratory appendages on eggshells of Drosophila species provides a powerful experimental system for studying how cell sheets give rise to complex three-dimensional structures. In Drosophila melanogaster, each of the two tubular eggshell appendages is derived from a primordium comprising a patch of "roof" cells bordered by a row of "floor" cells, which form the upper and lower surfaces of the appendage, respectively. We previously demonstrated that the transformation of this two-dimensional primordium into a tubular appendage involves out-of-plane bending followed by a sequence of spatially ordered cell intercalations. These morphological transformations correlate with the developmental of complementary distributions of myosin and Bazooka. The observed distributions suggest a temporally varying pattern of line tensions on the apical side of the appendage primordium. Computational modeling shows that these patterns of tension could explain the main features of both tissue deformation and cell rearrangements observed during three-dimensional morphogenesis. We are further testing this model by examining the patterns of myosin distribution and the accompanying morphogenetic movements in mutants and in different Drosophila species with morphologically distinct eggshell appendages.