Functions for PS Integrins in Tissue Adhesion, Migration, and Shape Changes during Early Embryonic Development in Drosophila

The position-specific (PS) integrins of Drosophila are a family of cell surface heterodimers that function as receptors for extracellular matrix molecules. In this study we used time-lapse videomicroscopy to examine living embryos lacking both maternal and zygotic expression of the genes that encode the α PS1, α PS2, and β PS integrin subunits. We demonstrate roles for these molecules as early as gastrulation. Abnormalities in mutant embryos include: separation and twisting of the embryonic germband, abnormal shape and migration of midgut primordia, irregular visceral mesoderm, detachment or amnioserosa cells, rupture of the cuticle along the dorsal midline, lack of midgut constriction, and detachment of somatic muscles. These observations suggest multiple roles for PS integrins in the adhesion of cells and in the formation, organization, and migration of embryonic tissues. We also show that although α PS1β PS and α PS2β PS are often expressed in adjacent embryonic tissues, this distribution does not necessarily reflect equivalent requirements. Furthermore, the complete loss of both α subunits does not produce all of the phenotypes observed in embryos lacking β PS. This suggests that α PS1β PS and α PS2β PS are not required in all embryonic processes utilizing PS integrins.