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SUMMARY:The evolutionary origin of neuronal signalling machinery and anima
 l cell differentiation - Dr Pawel Burkhardt (Sars Centre\, University of B
 ergen)
DTSTART:20230426T120000Z
DTEND:20230426T130000Z
UID:TALK199213@talks.cam.ac.uk
CONTACT:Nadine Randel
DESCRIPTION:Multicellularity evolved multiple times independently in eukar
 yotes. Choanoflagellates are the closest single-celled relatives of animal
 s. Strikingly\, these tiny protists can not only alternate between unicell
 ular and multicellular states\, but also express many genes previously tho
 ught to be animal specific (e.g.\, cadherins\, tyrosine kinases\, synaptic
  proteins)\, making choanoflagellates powerful models to investigate the o
 rigin of animal multicellularity\, the mechanisms underlying cell differen
 tiation and the ancestry of the neuronal protein machinery. In the first p
 art of my talk\, I will show that both\, temporal and spatial cell type di
 fferentiation was likely present in the stem lineage leading to animals. W
 e have reconstructed entire choanoflagellates and sponge choanocyte cells 
 in 3D through transmission electron microscopy on serial ultrathin section
 s. Our work has revealed several surprises about cell differentiation in c
 hoanoflagellates and constitute an important step in reconstructing the ce
 ll biology of the last common ancestor of animals. In the second part of m
 y talk\, I will present our recent discoveries on neuronal protein homolog
 s found in choanoflagellates and ctenophores. We have biochemically and st
 ructurally characterized several neuronal protein complexes from choanofla
 gellates and gained insights into their molecular mechanism. In the last p
 art of my talk\, I will present ultrastructural data on the ctenophore ner
 vous system. Our analysis indicates that the ctenophore nerve net is wired
  in a different way to what is known from other animals. These results cha
 llenge the paradigm of neuronal network activity emerging through cellular
  diversification and provide insights into how many ways to build a neural
  network. Together\, our work highlights the importance to include the clo
 sest unicellular relatives of animals to understand the evolutionary origi
 n of animal cell differentiation and demonstrates that choanoflagellates a
 nd ctenophores are at the center stage to understand the evolution of neur
 onal machinery and first neurons. 
LOCATION:Online
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