Pannexin 1 ohnologs in the teleost lineage

Advances in genomic analysis indicate that the early chordate lineage underwent two whole-genome duplication events in fairly rapid succession around 400-600 million years ago, and that a third duplication event punctuated the radiation of ray-finned fishes (teleosts) around 320-350 million years ago. Connexin ohnologs have been disproportionately well maintained in the teleost genome following this third event, implying that gap junction proteins are amenable to neofunctionalization. A second family of gap junction-like proteins, the pannexins, is also present in chordates, but expansion of this family following the teleost whole-genome duplication has not been addressed in the literature. In the current study we report that ohnologs of panx1 are expressed by zebrafish, and orthologs of these two genes can be found in various other teleost species. The genomic locality of each gene is described, along with sequence alignments that reveal conservation of classic pannexin-specific features/motifs. The transcripts were then cloned from cDNA for in vitro analysis, and both are shown to traffic to the plasma membrane when exogenously expressed. Furthermore, electrophysiological recordings show differences in the biophysical properties between the channels formed by these two proteins. Our results indicate that both copies of the ancestral teleost panx1 gene were conserved following the last whole-genome duplication event and, following conventional zebrafish nomenclature, should now be referred to as panx1a and panx1b.