Chapter 19: Gap Junction Communication in Invertebrates: The Innexin Gene Family

Publisher Summary Given the extent of genetic conservation through evolution, it is paradoxical that the structural components of gap junctions do not appear to be conserved throughout the animal kingdom. Electrical synapses in the escape systems of the crayfish ventral nerve cord and the goldfish spinal cord play the same basic role and, apart from subtle differences, are ultrastructurally alike; hence, they are formed from homologous proteins. Yet, despite much effort, connexins, the molecules that form gap junctions in vertebrates, have not been identified unequivocally in any invertebrate. In the wake of the sequencing of the Caenorhabditis (C.) elegans genome, this chapter discusses the evidence that intercellular channels in the nematode and the other model genetic invertebrate, Drosophila melanogaster , are formed from an apparently separate family of proteins that have been named innexins. There are still more to come in Drosophila, and there is no end of work ahead to characterize the individual proteins. Antibodies will be vital for cellular localization at LM and EM levels, and the proteins must be expressed in heterologous systems to establish their competency to form intercellular channels. As with the studies of connexins, the ultimate aim is to elucidate the functions of gap junctions in the diverse systems in which they are found.