Ultrastructural analysis of glycogen in hippocampal astrocytic processes using 3D virtual reality

Event Abstract Back to Event Ultrastructural analysis of glycogen in hippocampal astrocytic processes using 3D virtual reality Corrado Calì1*, Daniya J. Boges1, Glendon R. Holst1, Anna Kreshuk2, Fred A. Hamprecht2, Madhusudhanan Srinivasan3, Heikki Lehvaslaiho1 and Pierre J. Magistretti1 1 King Abdullah University of Science and Technology, Biomedical and Environmental Sciences and Engineering, Saudi Arabia 2 University of Heidelberg, Heidelberg Collaboratory for Image Processing, Germany 3 King Abdullah University of Science and Technology, Kaust Visualization Lab, Saudi Arabia Glycogen is a major energy store in astrocytes that provides energy support and signals for plasticity to neurons under the form of lactate. While the biochemistry of glycogen is well known, the spatial distribution of glycogen granules within astrocytes remains largely unknown. Recent studies show that glycogen-derived lactate is necessary for synaptic plasticity and memory formation in the hippocampus, but the predominant subcellular target, pre- and post-synaptic profiles, of lactate remains unknown. To this purpose, we imaged a 220 μm3 volume of adult rat hippocampus neuropil using a FIB-SEM microscope. This technique allowed us to automatically acquire very thin serial section micrographs (5 nm) at very high resolution (5 nm). Perfect isotropy of resulting voxels allowed iLastik, a state of art semi-automated software for EM stacks segmentation, to rapidly reconstruct every axon, dendrite, and the astrocytic processes present within the volume. Glycogen granules inside an astrocyte were recognized by morphology, and manually reconstructed using TrakEM2, a widely used tool for manual segmentation of serial section electron micrographs. We then used the fully immersive virtual reality (VR) environment CAVE (cave automatic virtual environment), a room where we are able to project a cellular reconstruction and visualize in 3D, to step into a world created with Blender, a free, fully customizable 3D modeling software. This detailed walk-in made it very clear that the apparently random cloud of glycogen granules in fact appeared in clusters. The DBSCAN algorithm determined the extent and number of glycogen clusters. Compared to other clustering algorithms, DBSCAN allows extraction of irregularly shaped clusters, and is much more sensitive to noise and outliers, making it a perfect choice for our case. We also used the Silhuette coefficient that allowed the optimal initialization parameters for DBSCAN, thus validating the clustering. In order to determine weather the clusters have a spatial relationship with the pre- or post- synaptic elements, we extracted all spines and boutons, as well as their size, using Neuromorph, a scientific package available as addons for Blender, designed for detailed morphological analysis of the neuropil. The use of CAVE was key to observe a nonrandom distribution of glycogen, and led us to develop tools to quantitatively analyze glycogen clustering and proximity to other subcellular features. Preliminary results indicate a regular 3D organization of glycogen granules, and a slight preference for the glycogen granules in astrocytic processes close to presynaptic boutons compared to postsynaptic spines (75% vs 25%, respectively). We are aiming to repeat the approach using samples from animals undergoing learning protocols in order to asses the plasticity of such an arrangement of glycogen granules within perisynaptic astrocytes. Acknowledgements We thank Graham Knott (BioEM facility, Lausanne, EPFL) for providing the image stack. The work was supported by a KAUST grant to Pierre Magistretti for a collaboration between the Blue Brain Project at EPFL and the KAUST-EPFL Alliance for Neuro-inspired High Performance Computing. Keywords: Glycogen, Glycogen spatial distribution, 3D analysis, 3D Reconstruction, Glycogen clustering Conference: 11th National Congress of the Belgian Society for Neuroscience, Mons, Belgium, 22 May - 22 May, 2015. Presentation Type: Oral or Poster presentation Topic: Neuroscience Citation: Calì C, Boges DJ, Holst GR, Kreshuk A, Hamprecht FA, Srinivasan M, Lehvaslaiho H and Magistretti PJ (2015). Ultrastructural analysis of glycogen in hippocampal astrocytic processes using 3D virtual reality. Front. Neurosci. Conference Abstract: 11th National Congress of the Belgian Society for Neuroscience. doi: 10.3389/conf.fnins.2015.89.00005 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 May 2015; Published Online: 05 May 2015. * Correspondence: Dr. Corrado Calì, King Abdullah University of Science and Technology, Biomedical and Environmental Sciences and Engineering, Thuwal, Jeddah, 23955-6900, Saudi Arabia, corrado.cali@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Corrado Calì Daniya J Boges Glendon R Holst Anna Kreshuk Fred A Hamprecht Madhusudhanan Srinivasan Heikki Lehvaslaiho Pierre J Magistretti Google Corrado Calì Daniya J Boges Glendon R Holst Anna Kreshuk Fred A Hamprecht Madhusudhanan Srinivasan Heikki Lehvaslaiho Pierre J Magistretti Google Scholar Corrado Calì Daniya J Boges Glendon R Holst Anna Kreshuk Fred A Hamprecht Madhusudhanan Srinivasan Heikki Lehvaslaiho Pierre J Magistretti PubMed Corrado Calì Daniya J Boges Glendon R Holst Anna Kreshuk Fred A Hamprecht Madhusudhanan Srinivasan Heikki Lehvaslaiho Pierre J Magistretti Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.