Baduel, L. | Search bioRxiv

bioRxiv2023

Antero-posterior gradients of cell plasticity and proliferation modulate posterior regeneration in the annelid Platynereis

Regenerative abilities are extremely variable among animals and may be substantial in some phyla, such as the annelids. So far, the cellular mechanisms underlying regeneration in annelids remain elusive. To precisely determine the origin(s), plasticity and fate of the cells participating in the blastema formation during posterior regeneration in the annelid Platynereis dumerilii, we developed specific tools to track proliferative cells as well as gut epithelial cells. We showed that two populations of progenitors are at play during regeneration and that, among them, gut progenitors from differentiated tissues are lineage-restricted. Strikingly, gut progenitors from less differentiated and more proliferative tissues are much more plastic and can produce ectodermal and mesodermal derivatives, in addition to gut cells. However, their plasticity is de facto limited as exemplified by their inability to regenerate populations of stem cells responsible for the constant growth of the worms. We evidenced that those stem cells are from local origin (i.e. from the segment abutting the amputation plan) as most of the blastema cells. Our results are in favour of a hybrid and flexible cellular model for posterior regeneration in Platynereis relying on a gradient of cell plasticity along the antero-posterior axis of the animal.

developmental biology↗

bioRxiv2023

Transcriptomic landscape of posterior regeneration in the annelid Platynereis dumerilii

Background: Restorative regeneration, the capacity to reform a lost body part following amputation or injury, is an important and still poorly understood process in animals. Annelids, or segmented worms, show amazing regenerative capabilities, and as such are a crucial group to investigate. Elucidating the molecular mechanisms that underpin regeneration in this major group remains a key goal. Among annelids, the nereididae Platynereis dumerilii (re)emerged recently as a front-line regeneration model. Following amputation of its posterior part, Platynereis worms can regenerate both differentiated tissues of their terminal part as well as a growth zone that contains putative stem cells. While this regeneration process follows specific and reproducible stages that have been well characterized, the transcriptomic landscape of these stages remains to be uncovered. Results: We generated a high quality de novo Reference transcriptome for the annelid Platynereis dumerilii. To do so, we produced and analyzed three RNA-sequencing datasets, encompassing five stages of posterior regeneration, along with blastema stages and non-amputated tissues as controls. We included these regeneration RNA-seq datasets, as well as embryonic and tissue-specific datasets from the literature to produce a Reference transcriptome. We used this Reference transcriptome to perform in depth analyzes of RNA-seq data during the course of regeneration to reveal the important dynamics of the gene expression, process with thousands of genes differentially expressed between stages, as well as unique and specific genes expression at each regeneration stage. The study of these genes highlighted the importance of the nervous system at both early and late stages of regeneration, as well as the enrichment of RNA-binding proteins (RBPs) during almost the entire regeneration process. Conclusions: In this study, we provided a high-quality de novo Reference transcriptome for the annelid Platynereis that is useful for investigating various developmental processes, including regeneration. Our extensive stage-specific transcriptional analysis during the course of posterior regeneration shed light upon major molecular mechanisms and pathways, and will foster many specific studies in the future.

genomics↗