ROLE OF NEURONAL DNA DOUBLE-STRAND BREAK SIGNALING IN ENGRAM REACTIVATION DURING MEMORY RECALL

​​​​Background: Neuronal DNA double-strand breaks (DSBs) exhibit a dual function in cognitive processes. Physiologically, transient DSBs are essential for the expression of immediate-early genes governing learning (Suberbielle et al., 2013; Madabhushi et al., 2015). Conversely, in Alzheimer’s disease (AD), chronic neuroinflammation exacerbates DSB accumulation, and the associated H2A.X signaling drives cognitive deficits (Belloy et al., 2025). While ablating H2ax prevents inflammation-induced spatial consolidation deficits, our preliminary data suggest it may also compromise long-lasting memory. We hypothesize that H2A.X signaling is critical for the accurate reactivation of the memory trace during recall.

Methods: We employed a viral "tag-and-manipulate" strategy in mice. We used a cFos-dependent Tet-Off system to tag active hippocampal neurons with an excitatory DREADD-mCherry reporter.

Experimental Design: H2ax neuron KO vs WT mice were taken off Doxycycline shortly prior to the encoding phase of a Novel Object Recognition task. This window allows the historic tagging of the "encoding engram" (mCherry+). Doxycycline was immediately restored post-encoding. Memory retention was assessed at several points. Brains were collected to immunolabel endogenous cFos (retrieval activity). We calculated the engram reactivation index by quantifying the overlap between the encoding (mCherry+) and retrieval (cFos+) ensembles.

Conclusion: These ongoing experiments aim to determine if DSB signaling is required for the stability and natural accessibility of memory engrams.

Bibliography:

M. Belloy … E. Suberbielle https://doi.org/10.1038/s41593-025-02041-x

R. Madabhushi … L.-H. Tsai https://doi.org/10.1016/j.cell.2015.05.032

E. Suberbielle … L. Mucke https://doi.org/10.1038/nn.3356