Array tomography: 15 years of synaptic analysis

Abstract

Synapses are minuscule, intricate structures crucial for the correct communication between neurons. In the 125 years since the term synapse was first coined, we have advanced a long way when it comes to our understanding of how they work and what they do. Most of the fundamental discoveries have been invariably linked to advances in technology. However, due to their size, delicate structural integrity and their sheer number, our knowledge of synaptic biology has remained somewhat elusive and their role in neurodegenerative diseases still remains largely unknown. Here, we briefly discuss some of the imaging technologies used to study synapses and focus on the utility of the high-resolution imaging technique array tomography. We introduce the array tomography technique and highlight some of the ways it is utilised with a particular focus on its power for analysing synaptic composition and pathology in human post-mortem tissue. We also discuss some of the benefits and drawbacks of techniques for imaging synapses and highlight some recent advances in the study of form and function by combining physiology and high-resolution synaptic imaging.

P2Y6Receptor-Dependent Microglial Phagocytosis of Synapses during Development Regulates Synapse Density and Memory

“…We measured synapse density as the density of Vglut1-staining puncta, Homer1staining puncta, and their co-localization (<200 nm) within the Z-stack of 25 μm thick brain sections using confocal microscopy. Thick sections have limitations with confocal microscopy, especially in relation to the z-plane (Avila and Henstridge, 2022), so ideally our data should be verified using array tomography of ultrathin sections. Vglut1 and Homer1 puncta density is high in the hippocampal stratum radiatum and molecular layer, as well as the somatosensory cortex, due to the high density of glutamatergic synapses.…”

P2Y6 receptor‐dependent microglial phagocytosis of synapses mediates synaptic and memory loss in aging

“…Thus, it may be informative to test the role of P2Y 6 R in phagocytosis in other culture conditions, particularly those relevant to aging. Note that the aging-induced synapse loss that we found here was quantified using confocal microscopy on 25 μm sections, which has limitations due to the thickness of these sections (Avila & Henstridge, 2022), and ideally would be checked using array tomography of ultrathin sections. Our in vivo data showed that aging induced a large increase in synaptic markers within CD68+ lysosomes, and this was prevented by P2Y 6 R knockout (Figure 5f).…”

Bringing synapses into focus: Recent advances in synaptic imaging and mass-spectrometry for studying synaptopathy

“…Array tomography (AT) is one imaging approach that can overcome some of the difficulties faced with EM ( Sanchez Avila and Henstridge, 2022 ). Developed in 2007, ( Micheva and Smith, 2007 ) and later adapted for human post-mortem tissue ( Kay et al, 2013 ), this high-resolution imaging technique allows a detailed study of the synapse at both a density and protein composition level.…”