A High-Resolution Method for Quantitative Molecular Analysis of Functionally Characterized Individual Synapses

Cell Rep. 2020 Jul 28;32(4):107968. doi: 10.1016/j.celrep.2020.107968.

Abstract

Elucidating the molecular mechanisms underlying the functional diversity of synapses requires a high-resolution, sensitive, diffusion-free, quantitative localization method that allows the determination of many proteins in functionally characterized individual synapses. Array tomography permits the quantitative analysis of single synapses but has limited sensitivity, and its application to functionally characterized synapses is challenging. Here, we aim to overcome these limitations by searching the parameter space of different fixation, resin, embedding, etching, retrieval, and elution conditions. Our optimizations reveal that etching epoxy-resin-embedded ultrathin sections with Na-ethanolate and treating them with SDS dramatically increase the labeling efficiency of synaptic proteins. We also demonstrate that this method is ideal for the molecular characterization of individual synapses following paired recordings, two-photon [Ca2+] or glutamate-sensor (iGluSnFR) imaging. This method fills a missing gap in the toolbox of molecular and cellular neuroscience, helping us to reveal how molecular heterogeneity leads to diversity in function.

Keywords: STED imaging; active zone; confocal imaging; molecular composition of the synapse; multiplexed immunolabeling; synapse diversity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Epoxy Resins / chemistry
  • Glutamic Acid / chemistry
  • Humans
  • Immunohistochemistry / methods*
  • Microscopy, Confocal / methods
  • Synapses / metabolism*
  • Synapses / physiology*

Substances

  • Epoxy Resins
  • Glutamic Acid