Recent work by the teams of Mark Verheijen and Michel van den Oever, published in Cell Reports, introduces a novel tool called Astro-GRASP to fluorescently label interaction between astrocyte processes and synapses on specific neuronal populations.
This new study builds on their previous reports showing that fear conditioning in mice reduces interaction of perisynaptic astrocyte processes (PAPs) with synapses in the hippocampus and that memory-encoding neurons (so-called engram cells) in the prelimbic cortex mediate expression of remote (one-month-old), but not recent (days-old) fear memories. Here, PhD students Aline Mak (graduated June 2026), Cristina Boers-Escuder, Sandra Parisi and Thomas Blok investigated whether astrocyte retraction also occurs in the prelimbic cortex and whether this differs between synapses on engram cells compared with the remaining population of cortical neurons (i.e., non-engram cells). For the comparison of synapses on distinct neuronal populations, they developed and validated Astro-GRASP, a new technique based on enhanced green fluorescent protein reconstitution across synaptic partners (eGRASP) that allows selective labelling of the interaction of PAPs with postsynaptic spines on genetically defined neuronal populations.
Surprisingly, they found that astrocytic coverage of synapses on both populations initially increases and then selectively decreases at synapses on the non-engram population in the prelimbic cortex. Furthermore, depletion of Ezrin, a structural protein enriched in PAPs, from prelimbic astrocytes reduces astrocyte-synapse coverage and enhances remote memory expression. Together, this indicates that astrocyte-synapse coverage on non-engram cells shapes remote memory strength, which for the first time reveals a role for astrocytes in memory consolidation via long-lasting modulation of cortical circuitry.
Source: Reduced astroglial-synapse coverage on cortical non-engram cells shapes remote memory strength. Cell Reports, Sept. 22, 2026.
https://www.cell.com/cell-reports/fulltext/S2211-1247(26)00906-X