AbstractBackgroundFirst identified in fruit flies with temperature-sensitive paralysis phenotypes, theDrosophila melanogaster TipElocus encodes four voltage-gated sodium (NaV) channel auxiliary subunits. This cluster ofTipE-like genes on chromosome 3L, and a fifth family member on chromosome 3R, are important for the optional expression and functionality of the Para NaVchannel but appear quite distinct from auxiliary subunits in vertebrates. Here, we exploited available arthropod genomic resources to trace the origin ofTipE-like genes by mapping their evolutionary histories and examining their genomic architectures.ResultsWe identified a remarkably conserved synteny block ofTipE-like orthologues with well-maintained local gene arrangements from 21 insect species. Homologues in the water flea,Daphnia pulex, suggest an ancestral pancrustacean repertoire of fourTipE-like genes; a subsequent gene duplication may have generated functional redundancy allowing gene losses in the silk moth and mosquitoes. Intronic nesting of the insectTipEgene cluster probably occurred following the divergence from crustaceans, but in the flour beetle and silk moth genomes the clusters apparently escaped from nesting. Across Pancrustacea,TipEgene family members have experienced intronic nesting, escape from nesting, retrotransposition, translocation, and gene loss events while generally maintaining their local gene neighbourhoods.D. melanogaster TipE-like genes exhibit coordinated spatial and temporal regulation of expression distinct from their host gene but well-correlated with their regulatory target, the Para NaVchannel, suggesting that functional constraints may preserve theTipEgene cluster. We identified homology between TipE-like NaVchannel regulators and vertebrate Slo-beta auxiliary subunits of big-conductance calcium-activated potassium (BKCa) channels, which suggests that ion channel regulatory partners have evolved distinct lineage-specific characteristics.ConclusionsTipE-like genes form a remarkably conserved genomic cluster across all examined insect genomes. This study reveals likely structural and functional constraints on the genomic evolution of insectTipEgene family members maintained in synteny over hundreds of millions of years of evolution. The likely common origin of these NaVchannel regulators with BKCaauxiliary subunits highlights the evolutionary plasticity of ion channel regulatory mechanisms.