In our project, we will determine the gene regulatory networks (GRNs) triggered by an injury and that control whole-body regeneration by dissecting the 1) transcriptional dynamics and 2) genome-wide chromatin accessibility at the tissue and single-cell levels. We will also 3) infer and 4) validate the predicted cellular trajectories and regulatory elements using genetic approaches. This study is based on data from the lab obtained over the past five years and will be carried out using the emerging whole-body regeneration model - the sea anemone Nematostella vectensis (Cnidaria, Anthozoa) - developed and mastered by the lab. After injury, the capacity to regenerate varies drastically from poorly regenerating mammals to whole-body regenerating aquatic organisms, such as cnidarians. Determining the gene regulatory networks underlying whole-body regeneration in order to reveal the similarities and in particular the differences with mammals are thus necessary. Yet comprehensive regeneration GRNs especially from non-bilaterian animals with whole-body regenerative capacities (i.e. cnidarians) are in their infancy. So far, establishing whole-body regeneration gene regulatory networks in cnidarians, especially at the single cell levels, has been hampered by a lack of suitable models and sufficiently sensitive techniques. We believe that it is now possible by using the state-of-the-art scRNAseq and (sc)ATACseq approaches mastered by the consortium in combination with Nematostella, a cnidarian whole-body regeneration model that we’re experts in and that is suitable for genetically dissecting gene function. In order to determine the GRNs underlying whole-body regeneration in Nematostella, we have three specific objectives: 1. Determine the transcriptional dynamics and regulatory elements active at the tissue and single-cell levels using scRNA-seq and ATAC-seq approaches. 2. Infer the cellular dynamics and blueprints of the regeneration GRNs and the factors that control them using state-of-the art trajectory reconstruction and motif enrichment analysis. 3. Experimentally validate core elements and wiring of the regeneration gene regulatory network by testing the regeneration specific enhancer elements and gene-specific functional approaches using CRISPR/Cas9. These objectives will enable us to reveal the precise cellular dynamics, i.e. stem cell trajectories that follow injury and the underlying regulatory mechanisms that are involved in the activation of regeneration-specific core modules. This in turn is crucial for evolutionary/comparative studies to gain insight into why some animals regenerate while others don’t (or do less) and to further develop biomedical approaches that foster the re-initiation of regenerative program(s) in organs or tissues that lost this capacity during evolution or during aging.