Several surface glycoproteins have been implicated in cell-cell adhesion of Dictyostelium discoideum. Antibodies reactive with these molecules have been shown to block adhesion at different stages in development. Further confidence in their essential roles would come from genetic and molecular manipulations that result in cells that specifically fail to synthesize one of these glycoproteins and give rise to a concomitant loss of the pertinent adhesion mechanism. The consequence of loss of cell-cell adhesion could then be directly assessed with regards to morphogenesis, cell-sorting and late gene expression. It is becoming increasingly clear that cell-cell adhesion is a basic aspect of integration and pattern formation of multicellular organisms. We have uncovered a developmentally regulated, EDTA-sensitive adhesion mechanism by genetically inactivating the EDTA-resistant adhesion mechanism that appears during the aggregation stage. Both genetic and immunological approaches have implicated a glycoprotein of 80,000 daltons, gp80, in the EDTA-resistant mechanism. We inactivated this mechanism by mutations in the modB locus that is responsible for glycosylation of gp80. We have isolated genomic clones of the bp80 gene and propose to characterize them fully as well as to use them to inactivate endogenous gp80 mRNA by transcription of the antistrand from transformed constructs. Furthermore, we propose to analyze the EDTA-sensitive adhesion mechanism in a similar manner using our adhesion blocking antibodies to lead us to the pertinent cell surface molecules and their genes. Cells lacking both adhesion mechanisms would be expected to be completely non-adhesive and unable to form multicellular aggregates. The signals normally generated in the multicellular state will then be open to detailed analysis.
NIH ExPorter
NIH ExPorter