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Sars International Centre for Marine Molecular Biology
Evolutionary Origin of Synapses and Neurons

Burkhardt Group

Our group utilizes marine organisms to reveal the molecular and cellular mechanisms that underlie the evolutionary origin of synapses and neurons.

Ctenophore Facility
Photo:
Sars Centre

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When and how did the first neurons evolve? How did this key event led to the vast marine biodiversity we see in today’s oceans? Neurons, synapses, and the proteins required for their function are critical to the biology and behaviour of animals, but little is known about how they first evolved. Our research has the primary focus to utilize marine organisms to understand the molecular and cellular mechanisms that underlie the origin of synapses and neurons.

We are particularly interested in:

  • The origin and functional evolution of synaptic proteins
  • Co-option of these proteins into ancient synaptic scaffolds
  • Evolution of the first neuron-like cell type in animals

Animal phylogeny and diversity

Animal phylogeny and possible scenarios of nervous system origin(s).

Photo:
Pawel Burkhardt

In neurons, the transmission of chemical signals (called neuropeptides or neurotransmitters) from the presynapse to the postsynapse requires distinct sets of pre- and postsynaptic protein networks. The goal of our laboratory is to reconstruct the origin and evolution of these synaptic proteins. We use a comparative approach and work with choanoflagellates, the closest living relatives of animals, sponges, basal animals with no synapses and neurons, and ctenophores, basal animals with synapses and neurons, as model organisms. We aim to understand when the proteins required for synaptic activity first evolved, how they functioned at a molecular level and which combinations of synaptic proteins resulted in the origin of the synapse. Our approach is to use a variety of techniques, ranging from marine invertebrate sampling, volume electron microscopy, super-resolution imaging, quantitative live cell imaging, state-of-the-art molecular biology, single cell RNA sequencing, novel compound identifications, behavioural experiments to X-ray crystallography to study synaptic protein homologs in choanoflagellates, sponges and ctenophores. By understanding when the proteins required for synaptic activity first evolved and how they functioned in the first animals we will be able to reconstruct the evolutionary history of these proteins and understand the evolution of the first synapses and neurons.

Ctenophore nerve net

(A) 3D reconstruction of SBF-SEM data showing two comb rows underlaid by the epithelial nerve net of the ctenophore Mnemiopsis leidyi. (B) Single neuron with several highly branching interconnected neurites (purple). (C-E) 3D reconstruction and TEM micrograph of a ctenophore synapse showing the synaptic triad.

Photo:
Pawel Burkhardt