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TitleQuantitative expansion microscopy for the characterization of the spectrin periodic skeleton of axons using fluorescence microscopy.
Publication TypeJournal Article
Year of Publication2020
AuthorsMartínez, Gaby F., Nahir G. Gazal, Gonzalo Quassollo, Alan M. Szalai, Esther Del Cid-Pellitero, Thomas M. Durcan, Edward A. Fon, Mariano Bisbal, Fernando D. Stefani, and Nicolas Unsain
JournalSci Rep
Date Published2020 02 19
KeywordsAnimals, Axons, Calibration, Cell Membrane, Mice, Mice, Inbred C57BL, Microscopy, Fluorescence, NIH 3T3 Cells, Rats, Wistar, Reproducibility of Results, Spectrin

Fluorescent nanoscopy approaches have been used to characterize the periodic organization of actin, spectrin and associated proteins in neuronal axons and dendrites. This membrane-associated periodic skeleton (MPS) is conserved across animals, suggesting it is a fundamental component of neuronal extensions. The nanoscale architecture of the arrangement (190 nm) is below the resolution limit of conventional fluorescent microscopy. Fluorescent nanoscopy, on the other hand, requires costly equipment and special analysis routines, which remain inaccessible to most research groups. This report aims to resolve this issue by using protein-retention expansion microscopy (pro-ExM) to reveal the MPS of axons. ExM uses reagents and equipment that are readily accessible in most neurobiology laboratories. We first explore means to accurately estimate the expansion factors of protein structures within cells. We then describe the protocol that produces an expanded specimen that can be examined with any fluorescent microscopy allowing quantitative nanoscale characterization of the MPS. We validate ExM results by direct comparison to stimulated emission depletion (STED) nanoscopy. We conclude that ExM facilitates three-dimensional, multicolor and quantitative characterization of the MPS using accessible reagents and conventional fluorescent microscopes.

Alternate JournalSci Rep
PubMed ID32076054
PubMed Central IDPMC7031372