Misa Arizono et al in Nature Communications

Structural basis of astrocytic Ca2+ signals at tripartite synapses

Astrocytic Ca2+ signals can be fast and local, supporting the idea that astrocytes have the ability to regulate single synapses. However, the anatomical basis of such specific signaling remains unclear, owing to difficulties in resolving the spongiform domain of astrocytes where most tripartite synapses are located. Using 3D-STED microscopy in living organotypic brain slices, we imaged the spongiform domain of astrocytes and observed a reticular meshwork of nodes and shafts that often formed loop-like structures. These anatomical features were also observed in acute hippocampal slices and in barrel cortex in vivo. The majority of dendritic spines were contacted by nodes and their sizes were correlated. FRAP experiments and Ca2+ imaging showed that nodes were biochemical compartments and Ca2+ microdomains. Mapping astrocytic Ca2+ signals onto STED images of nodes and dendritic spines showed they were associated with individual synapses. Here, we report on living nanoscale organization of astrocytes, identifying nodes as a functional astrocytic component of tripartite synapses that may enable synapse-specific communication between neurons and astrocytes.

Figure: STED imaging reveals astrocytic processes infiltrating neuropil (left) and exhibiting local Ca2+ signals at individual synapses (right).

The study (Arizono et al, Nature Communications 2020), which was spearheaded by Misa Arizono in the Nägerl team, was supported by a long-standing and fruitful collaboration with the Bordeaux Neurocampus teams of Marsicano and Oliet, which received funding from the Labex Brain and ANR.

Article

Structural basis of astrocytic Ca2+ signals at tripartite synapses
Misa Arizono, V. V. G. Krishna Inavalli, Aude Panatier, Thomas Pfeiffer, Julie Angibaud, Florian Levet, Mirelle J. T. Ter Veer, Jillian Stobart, Luigi Bellocchio, Katsuhiko Mikoshiba, Giovanni Marsicano, Bruno Weber, Stéphane H. R. Oliet & U. Valentin Nägerl
Nat Commun 11, 1906 (2020).
https://www.nature.com/articles/s41467-020-15648-4