Regeneration in sponge Sycon ciliatum partly mimics postlarval development

Somatic cells dissociated from an adult sponge can re-organize and develop into a juvenile-like sponge, a remarkable phenomenon of regeneration. However, the extent to which regeneration recapitulates embryonic developmental pathways has remained enigmatic. We have standardized and established a sponge Sycon ciliatum regeneration protocol from dissociated cells. From the morphological analysis, we demonstrated that dissociated sponge cells follow a series of morphological events resembling postembryonic development. We performed high-throughput sequencing on regenerating samples and compared the data with regular postlarval development. Our comparative transcriptomic analysis illuminates that sponge regeneration is equally as dynamic as embryogenesis. We find that sponge regeneration is orchestrated by recruiting pathways like those utilized in embryonic development. We further demonstrated that sponge regeneration is accompanied by cell death at early stages, revealing the importance of apoptosis in remodelling the primmorphs to initiate re-development. Since sponges are likely to be the first branch of extant multicellular animals, we suggest that this system can be explored to study the genetic features underlying the evolution of multicellularity and regeneration.