title: Genomic organization of a voltage-gated Na+ channel in a hydrozoan jellyfish: insights into the evolution of voltage-gated Na+ channel genes.
abstract: Voltage-gated Na+ channels are responsible for fast propagating action potentials. The structurally simplest animals known to contain rapid, transient, voltage-gated currents carried exclusively by Na+ ions are the Cnidaria. The Cnidaria are thought to be close to the origin of the metazoan radiation and thus are pivotal organisms for studying the evolution of the Na+ channel gene. Here we describe the genomic organization of the Na+ channel alpha subunit, PpSCN1, from the hydrozoan jellyfish, Polyorchis penicillatus. We show that most of the 20 intron sites in this diploblast are conserved in mammalian Na+ channel genes, with some even shared by Ca2+ channels. One of these conserved introns is spliced by a rare U 12-type spliceosome. Such conservation places the origin of the primary exon arrangement of Na+ channels and different intron splicing mechanisms to at least the common ancestors of diploblasts and triploblasts, approximately 600 million-1 billion years ago.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Canada.
authors.forename: J D
authors.initials: JD
authors.lastname: Spafford
authors.forename: A N
authors.initials: AN
authors.lastname: Spencer
authors.forename: W J
authors.initials: WJ
authors.lastname: Gallin
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D015220:Calcium Channels / Q000235:genetics; D019143:Evolution, Molecular; D005091:Exons; D015698:Genomic Library; D006829:Hydra / Q000235:genetics*; D007438:Introns; D015640:Ion Channel Gating; D008969:Molecular Sequence Data; D010802:Phylogeny; D012342:RNA, Small Nuclear / Q000235:genetics; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000235:genetics; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D015222:Sodium Channels / Q000145:classification / Q000235:genetics*; D017381:Spliceosomes / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D012342:RNA, Small Nuclear; D017413:Ribonucleoprotein, U2 Small Nuclear; D015222:Sodium Channels; C096986:U12 small nuclear RNA