Nanoscale imaging of the functional anatomy of the brain

Abstract

Progress in microscopy technology has a long history of triggering major advances in neuroscience. Super-resolution microscopy (SRM), famous for shattering the diffraction barrier of light microscopy, is no exception. SRM gives access to anatomical designs and dynamics of nanostructures, which are impossible to resolve using conventional light microscopy, from the elaborate anatomy of neurons and glial cells, to the organelles and molecules inside of them. In this review, we will mainly focus on a particular SRM technique (STED microscopy), and explain a series of technical developments we have made over the years to make it practical and viable in the field of neuroscience. We will also highlight several neurobiological findings on the dynamic structure-function relationship of neurons and glia cells, which illustrate the value of live-cell STED microscopy, especially when combined with other modern approaches to investigate the nanoscale behavior of brain cells.

The endoplasmic reticulum in perisynaptic astrocytic processes: shape, distribution and effect on calcium activity

“…Further quantification of the Ca 2+ channels expressed in PAPs, their density, location and remodeling in live tissue under (patho-)physiological conditions is thus essential to better understand astrocyte activity at synapses. The recent advances in super-resolution techniques, notably single particle tracking methods, provide a promising avenue to overcome current limitations in obtaining such data ( 21 , 71 ).…”

“…The recent advances in super-resolution techniques, notably single particle tracking methods, provide a promising avenue to overcome current limitations in obtaining such data [33,6].…”

Control of Ca2+ signals by astrocyte nanoscale morphology at tripartite synapses

“…To validate the role of thin shafts suggested by our model’s predictions, we tried to recreate the widening of shaft width in experimental conditions. Coincidentally, our recent super-resolution study revealed that the nano-architecture of fine processes is remodeled in hypo-osmotic conditions, where shaft width increased while node width remained unaltered (see Fig 3 in Arizono, Inavalli, et al (2021)). While hypo-osmotic conditions undoubtedly cause many physiological changes to astrocytes, it is the closest experimentally available model to test our model predictions.…”

“…Furthermore, aberrant Ca 2+ signals ( Shigetomi et al, 2019 ) and changes in astrocytic morphology, such as “astrocytic swelling”, occur in pathological conditions such as brain injury, including ischemic, traumatic, hemorrhagic and metabolic injuries, stroke and epilepsy ( Lafrenaye and Simard, 2019 ). Interestingly, our recent STED study reported that swelling can also occur at the level of fine astrocytic processes ( Arizono et al, 2021a ). The effect of such a remodeling of astrocytic nano-morphology on the local Ca 2+ signals involved in regulating synapses yet remains unclear.…”

“…Importantly, pathological changes in astrocytic morphology (Lafrenaye and Simard, 2019), such as "astrocytic swelling", are paired with aberrant Ca 2+ signals (Shigetomi et al, 2019). We have recently reported that swelling can also occur at the level of fine astrocytic processes (Arizono et al, 2021a). The effect of such a remodeling of astrocytic nano-morphology on the local Ca 2+ signals involved in regulating synapses remains yet unclear.…”