Abstract

Specification of cell fate identity during development of multicellular organisms is a fundamental process underlying differentiation. The organism must integrate genomically encoded information at the level of the gene regulatory network in order to direct the differentiation of distinct cell-type specific developmental programs. We utilize the sea anemone Nematostella vectensis as a model for cell fate specification and study this process within the context of embryonic and regenerative neurogenesis. Using single cell sequencing as a read-out for cell identity, we have generated a complete atlas of sea anemone cell types across the developmental time course as well as during the regenerative process. Using this approach, we find a diversity of cell types in the nervous system with over 30 distinct cell states represented. We utilize transgenic reporter constructs driving cell-type specific expression via neural promoters which have been identified in our single cell studies to label and track cell populations over embryogenesis and regeneration. By utilizing these novel reporter lines to sort specific neural sub-populations, we are able to perform chromatin accessibility studies using ATAC -seq to identify and link regulatory elements to the expression of key genes in the network. In this way, we are assembling gene regulatory networks for developmental and regenerative neurogenesis using a candidate-gene independent approach. This approach is particularly suited to the investigation of non-Bilaterian neuron specification as it allows for the discovery of lineage-specific innovations in cell type specification.