Emergence of novel cephalopod gene regulation and expression through large-scale genome reorganization

Cephalopods are an enigmatic animal group with complex and adaptive behaviors such as camouflage; however the genetic basis for these traits is not well understood. Here the authors reveal a set of cephalopod-restricted rearranged genomic loci, involving known neuronal regulators but also unexpected gene families, that confer topological organization and gene regulation. Coleoid cephalopods (squid, cuttlefish, octopus) have the largest nervous system among invertebrates that together with many lineage-specific morphological traits enables complex behaviors. The genomic basis underlying these innovations remains unknown. Using comparative and functional genomics in the model squid Euprymna scolopes, we reveal the unique genomic, topological, and regulatory organization of cephalopod genomes. We show that coleoid cephalopod genomes have been extensively restructured compared to other animals, leading to the emergence of hundreds of tightly linked and evolutionary unique gene clusters (microsyntenies). Such novel microsyntenies correspond to topological compartments with a distinct regulatory structure and contribute to complex expression patterns. In particular, we identify a set of microsyntenies associated with cephalopod innovations (MACIs) broadly enriched in cephalopod nervous system expression. We posit that the emergence of MACIs was instrumental to cephalopod nervous system evolution and propose that microsyntenic profiling will be central to understanding cephalopod innovations.

Automated summary

This study reveals the unique genomic, topological, and regulatory organization of cephalopod genomes, identifies microsyntenies associated with cephalopod nervous system evolution, and suggests that microsyntenic profiling will be central to understanding cephalopod innovations.