Biology subjects

Refaeli, R.

Publications and source records attributed to Refaeli, R..

4 recordsLinked to original sources

bioRxiv2025

Astrocytic Activation Completely Corrects Memory Performancein an Alzheimer's Disease Model

Neural and glial dysfunction are thought to underlie memory impairments in Alzheimers disease (AD). Conversely, astrocytes are known to play a central role in the healthy brain, and their activation has been shown to enhance memory. To test whether activation of astrocytes can correct memory deficits associated with AD, we expressed hM3Dq in CA1 astrocytes of 7 months old 5XFAD AD model mice, enabling astrocytic chemogenetic Gq pathway activation, following exposure to CNO. We report that astrocytic activation results in complete memory correction, and even memory improvement of AD model mice beyond that of untreated WT levels. We went further to discover the mechanisms underlying this memory improvement in AD mice: First, using 2-photon imaging and electrophysiology, we observed increased neuronal activity (displayed as elevated cFos expression and amplified awake Ca2+ events) as well as augmented in-vivo long term plasticity following astrocytic activation. Subsequently, we observed increased astrocytic endocytosis of A{beta} plaques. Finally, we report that the beneficial effects of astrocytic activation remained stable for an entire year, and persisted beyond the window of astrocytic Gq activation. Our findings that astrocytes correct memory impairments in an AD model could have important clinical implications towards treating this disease.

neuroscience↗

bioRxiv2023

Astrocytes Control Recent and Remote Memory Strength by Affecting the Recruitment of the CA1->ACC Projection to Engrams

Recent and remote memories are encoded throughout the brain in Engrams: cell ensembles formed during acquisition, and upon their reactivation, a specific memory can be recalled. The maturation of engrams from recent to remote time points involves the recruitment of CA1 neurons projecting to the anterior cingulate cortex (CA1[->]ACC). Various modifications to CA1 astrocytes, to the Gq- or Gi-GPCR pathways, during memory acquisition were shown to affect recent and remote recall in seemingly contradictory ways. To address the inconsistency, we applied transgenic approaches for ensemble identification, CLARITY, retro-AAV virus for circuit mapping, and chemogenetics in astrocytes for functional investigation. We manipulated the activity of either Gq- or Gi-pathways in CA1 astrocytes during memory acquisition and tagged cFos+ engram cells and CA1[->]ACC cells during recent and remote recall in the same animals. The behavioral results were coupled with changes in the recruitment of CA1[->]ACC projection cells to the engram, demonstrated by the number of CA1[->]ACC projecting cells in the engram as well as the number of axons projecting from the CA1 engram toward the ACC: Gq pathway activation in astrocytes caused enhancement of recent recall alone and was accompanied by earlier recruitment of CA1[->]ACC projecting cells to the engram. In contrast, when activating the Gi pathway in astrocytes during acquisition, only remote recall was impaired, and CA1[->]ACC projecting cells were not recruited during remote memory. Finally, we provide a simple working model, hypothesizing that astrocytes control behavioral performance by targeting the CA1[->]ACC projection. Specifically, that Gq- and Gi-pathway activation affect memory differently, but do so by modulating the same mechanism. These findings illuminate the importance of astrocytes in the acquisition of fear memory and their implications on recent and remote recall.

neuroscience↗

bioRxiv2022

Engram Stability and Maturation During Systems Consolidation Underlies Remote Memory

Remote memories play an important role in how we perceive the world and are rooted in ensembles in the CA1 and ACC, however the evolution of these components during systems consolidation has not yet been comprehensively addressed. By applying transgenic approaches for ensemble identification, CLARITY, retro-AAV and rabies virus for circuit mapping, and chemogenetics for functional interrogation, we addressed the dynamics of CA1-ACC ensembles and their connectivity as well as the contribution of astrocytes to the process. We found that the CA1 engrams remain stable between recent and remote recall, and, the inhibition of the engram for recent recall during remote recall functionally impairs memory. We also found that the new cells in the remote recall engram in the CA1 are not added randomly, but differ according to their connections: First, the anterograde CA1 [->] ACC engram cell projection grows larger. Second, in the retrograde projections, the ACC reduces input to CA1 engram cells, while input from the entorhinal cortex and paraventricular nucleus of the thalamus increases. Finally, we found that activating CA1 astrocytes during acquisition improves recent but not remote recall, and that CA1 [->] ACC projecting cells are recruited earlier when the astrocytes are stimulated. Our results shine fresh light on systems consolidation by providing a deeper understanding of engram stability and maturation in the transition from recent to remote memory.

neuroscience↗

bioRxiv2020

Features Of Hippocampal Astrocytic Domains And Their Spatial Relation To Excitatory And Inhibitory Neurons

The mounting evidence for the involvement of astrocytes in neuronal circuits function and behavior stands in stark contrast to the lack of detailed anatomical description of these cells and the neurons in their domains. To fill this void, we imaged >30,000 astrocytes in cleared hippocampi, and employed converging genetic, histological and computational tools to determine the elaborate structure, distribution and neuronal content of astrocytic domains. First, we characterized the spatial distribution of >19,000 astrocytes across CA1 lamina, and analyzed the detailed morphology of thousands of reconstructed domains. We then determined the excitatory content of CA1 astrocytes, averaging above 13 pyramidal neurons per domain and increasing towards CA1 midline. Finally, we discovered that somatostatin neurons are found in close proximity to astrocytes, compared to parvalbumin and VIP inhibitory neurons. This resource expands our understanding of fundamental hippocampal design principles, and provides the first quantitative foundation for neuron-astrocyte interactions in this region.

neuroscience↗