A DROSOPHILA HOMOLOG OF MEMBRANE-SKELETON PROTEIN-4.1 IS ASSOCIATED WITH SEPTATE JUNCTIONS AND IS ENCODED BY THE CORACLE GENE

Protein 4.1 functions to link transmembrane proteins with the underlyi ng spectrin/actin cytoskeleton. To permit a genetic analysis of the de velopmental role and cellular functions of this membrane-skeletal prot ein, we have identified and characterized its Drosophila homologue (te rmed D4.1). D4.1 is localized to the septate junctions of epithelial c ells and is encoded by the coracle gene, a new locus whose primary mut ant phenotype is a failure in dorsal closure. In addition, coracle mut ations dominantly suppress Ellipse, a hypermorphic allele of the Droso phila EGF-receptor homologue. These data indicate that D4.1 is associa ted with the septate junction, and suggest that it may play a role in cell-cell interactions that are essential for normal development.