MICROINJECTED ANTISERA AGAINST DUCTIN AFFECT GASTRULATION IN DROSOPHILA-MELANOGASTER

Ductin is a putative connexon-forming protein in gap junctions of arth ropods. To analyze the role of gap-junction mediated cell-cell communi cation during Drosophila embryogenesis, we used two different polyclon al anti-ductin sera. One antiserum was directed against ductin isolate d from gap junctions of the lobster Nephrops whilst the other was rais ed against a nonapeptide at the N-terminus of ductin from Drosophila. Both antisera were found to inhibit, when microinjected into Drosophil a ovarian follicles, the intercellular exchange of fluorescent tracer molecules between oocyte and follicle epithelium. This result indicate s that Drosophila ductin plays a decisive role in gap-junctional commu nication and confirms the cytoplasmic location of the ductin N-terminu s in gap junctions. On immunofluorescence preparations and immunoblots , the antiductin sera specifically recognized ovarian as well as embry onic antigens. Following microinjections of the antisera into embryos prior to gastrulation, significantly reduced rates of hatching larvae were obtained. Moreover, microinjections into the mid-ventral region o f the embryos resulted in specific ventral defects that depended on th e concentration of the ductin antibodies. In particular, larvae with v entral holes in their cuticles occurred with high frequency. During ga strulation, antiserum-injected embryos often developed defects in the middle region of their ventral furrow. Here, mesodermal cells failed t o invaginate correctly and, thus, no cuticle was formed. We conclude t hat, during Drosophila embryogenesis, gap-junctional communication is required for epithelial integrity and morphogenetic events.