short gastrulation Interacts with Integrins during Wing Vein Development

During Drosophila wing morphogenesis a series of cell-cell and cell-extracellular matrix interactiofis define the overall shape of the wing and placement of wing veins, decapentaplegic, a homolog of vertebrate BMP-4, is required for development of wing veinsand is expressed in the vein primordia during early pupal development. The BMP antagonist short gastrulation (sog) is expressed in a complementary pattern to dpp in intervein cells and opposes the vein-promoting activity of dpp. Regulated cleavage of Sog protein by Tolloid, a member of the astacin family of metalloproteases, has been hypothesized to generate forms with differential activities. We have assayed for the interaction of sog with components of the extracellular matrix and their receptors, based on the modification of vein phenotypes of enhancer piracy-sog lines in which sog is overexpressed. This analysis has revealed a genetic interaction between sog and integrins. This interaction involves specifically [Beta]PS and [Alpha]PS1 integrin subunits, in addition to the novel [Alpha]PS3 subunit. We also present evidence of a physical binding of a low-molecular-weight form of Sog to [Alpha]PS1. During pupal wing development, integrins perform the main role of regulating apposition between the dorsal and ventral surfaces of the wing. Our results suggest that, in addition to this role, integrins are important for the formation of wing veins by binding and possibly regulating the activity of Sog during pupal development.