European Molecular Biology Laboratory
Host: Graduate Students
Title: Building bilaterian brains: innovations in molecular machinery, cell types, and nervous system architecture
We study the evolution of animal form at all scales, with a particular focus on the origin and rise of their most fascinating trait, which is the centralized nervous system. For this, we track the evolution of neurons and other constituent cell types across animal phylogeny, focusing on slow-evolving animals. We have chosen the nereid Platynereis dumerilii as a powerful model for comparative studies, with morphologically similar organisms already existing as early as the Cambrian. We take advantage of its highly stereotypic development to establish the link between gene expression, cellular morphology, and organ formation for an entire body.
To exemplify the evolution of form in the bilaterian brain, I will explain how we trace the assembly of conserved synaptic proteins, transmitters and receptors in a basic set of bilaterian neuron types; and how we trace the assembly of these neuron types into a basic set of neural circuits that make up the bilaterian brain. Enabling this, we have constructed a unique cellular atlas for the nereid, the PlatyBrowser, which allows us to combine genome-wide expression profiling with cellular ultrastructure and connectomics for an entire body. To systematically characterize cellular morphologies we have added AI-based recognition of cellular MorphoFeatures to the atlas that we can now align with cell type-specific gene expression modules. I will explain how we use these unique resources to advance our understanding of bilaterian brain evolution, and to find hotspots of cellular variation at the micro- and macroevolutionary scale that drive the evolution of form.