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 cel l surface heterodimers that function as receptors for extracellular ma trix molecules. In this study-we used time-lapse videomicroscopy to ex amine living embryos lacking both maternal and zygotic expression of t he genes that encode the alpha(PS1), alpha(PS2), and beta(PS) integrin subunits. We demonstrate roles for these molecules as early as gastru lation. Abnormalities in mutant embryos include: separation and twisti ng of the embryonic germband, abnormal shape and migration of midgut p rimordia, irregular visceral mesoderm, detachment of amnioserosa cells , rupture of the cuticle along the dorsal midline, lack of midgut cons triction, and detachment of somatic muscles. These observations sugges t multiple roles for PS integrins in the adhesion of cells and in the formation, organization, and migration of embryonic tissues. We also s how that although alpha(PS1)beta(PS) and alpha(PS2)beta(PS) are often expressed in adjacent embryonic tissues, this distribution does not ne cessarily reflect equivalent requirements. Furthermore, the complete l oss of both alpha subunits does not produce all of the phenotypes obse rved in embryos lacking beta(PS). This suggests that alpha(PS1)beta(PS ) and alpha(PS2)beta(PS) are not required in all embryonic processes u tilizing PS integrins. (C) 1995 Academic Press, Inc.