Showcase Symposium 2020 Project Talk Q&A: Electron Microscopy Pipeline and Discoveries

At our virtual Showcase Symposium 2020, Allen Institute for Brain Science teams present project talks highlighting their work. Please use this forum thread to ask questions for the speakers of the Electron Microscopy Pipeline and Discoveries talk with @nunod, Wenjing Yin, @fcollman, Russel Torres, Nick Turner (Princeton University), @sharmishtaa, Agnes Bodor, Clare Gamlin, and Joann Buchanan. Please see the full list of Showcase 2020 forum threads to ask questions about other talks.

Beautiful EM work - you mentioned that these analyses were also performed on human in addition to mouse. For many of the core structural components (cilia, mitochondria, post-synaptic shape) did you notice any differences between mouse and human, or are they basically the same?

Thank you Abhaduri, The data acquisition was also performed in human tissue but not the analysis yet. Those are great questions, so stay tuned.

Question from Zoom: The L5IT cell that you zoomed in on appears to have a lot of side-spine boutons. Is that typical for that cell type. Are postsynaptic sites dendritic shafts of excitatory cells?
@nunod replies: The side-spine boutons are more common in other cell types than the layer 5 IT (as for example some layer 6 pyramidal neurons) We have not quantified the shape of the boutons in this cell types, so we don’t know if it is higher than the ~20% that is expected from previous studies on cortical neurons. We have also not quantified if they are targeting more spines or dendritic shafts yet. The results that Sharmi presented will allow us to do that in an automatic matter.

Thank you for presenting interesting works. I would like to ask questions to Sharmishtaa Seshamani. It was fascinating to analyze postsynaptic shapes using autoencoder. What implications data-driven postsynaptic types(classification?) could have comparing with already-known postsynaptic shapes?

Thank you EunjiLee. These post synaptic shapes obtained with data driven modelling definitely help us see large populations of shapes together and one thing we can already see is that there is a continuous space representing them. For example, spines seem to have an appearance change that involve many factors, length, size, size of head relative to neck, etc and this lies on a continuous scale. Therefore hard classifications into known shape types may need to be reconsidered/restructured to incorporate these findings. Secondly, representing post synaptic shapes with these fine differences can enable us to do better differentiations between cells as well as their targets.

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