EAT-5 AND UNC-7 REPRESENT A MULTIGENE FAMILY IN CAENORHABDITIS-ELEGANS INVOLVED IN CELL-CELL COUPLING

The Drosophila melanogaster genes Passover and I(1)ogre and the Caenor habditis elegans gene unc-7 define a gene family whose function is not known. We have isolated and characterized the C. elegans gene eat-5, which is required for synchronized pharyngeal muscle contractions, and find that it is a new member of this family. Simultaneous electrical and video recordings reveal that in eat-5 mutants, action potentials o f muscles in the anterior and posterior pharynx are unsynchronized. In jection of carboxyfluorescein into muscles of the posterior pharynx de monstrates that all pharyngeal muscles are dye-coupled in wild-type an imals; in eat-5 mutants, however, muscles of the anterior pharynx are no longer dye-coupled to posterior pharyngeal muscles. We show that a gene fusion of eat-5 to the green fluorescent protein is expressed in pharyngeal muscles. unc-7 and eat-5 are two of at least sixteen member s of this family in C. elegans as determined by database searches and PCR-based screens. The amino acid sequences of five of these members i n C. elegans have been deduced from cDNA sequences. Polypeptides of th e family are predicted to have four transmembrane domains with cytopla smic amino and carboxyl termini. We have constructed fusions of one of these polypeptides with P-galactosidase and with green fluorescent pr otein. The fusion proteins appear to be localized in a punctate patter n at or near plasma membranes. We speculate that this gene family is r equired for the formation of gap junctions.