Meeting Abstract
Innexin proteins facilitate cell-cell communication by forming gap junctions or non-junctional hemichannels. These channels have a range of important cell physiological roles. To date, the complement of innexin genes in ctenophores (comb jellies) has not been characterized in any detail. In this study, we have identified and phylogenetically characterized the full complement of innexins in the genomes of three ctenophores: Mnemiopsis leidyi, Pleurobrachia bachei, and Beroe ovata. We identified nine innexin genes in P. bachei and twelve in both M. leidyi and B. ovata. The last common ancestor was determined to have at least twelve innexins with a cluster of three. We show evidence from single-cell RNA-Seq and developmental time-course RNA-Seq that expression within this cluster is co-regulated. Using MEME and TOMTOM we identified highly conserved non-coding motifs upstream of these clustered genes. We predict that these motifs are regulatory elements important for the gene co-regulation that we observe and have contributed to the maintenance of this cluster over hundreds of millions of years. Lastly, we show that one innexin in the M. leidyi cluster is expressed exclusively in colloblasts, adhesive cells used to capture prey. This colloblast-specific innexin that is present in the transcriptomes of other ctenophores has been lost in both B. ovata (which lacks colloblasts) and P. bachei (which has colloblasts). Our results provide insight into gene regulation, ancient gene clustering, and the potential for cell-cell communication via gap junctions in ctenophores.
