Opto-CLIP reveals dynamic FMRP regulation of mRNAs upon CA1 neuronal activation.

Neuronal diversity and function are intricately linked to the dynamic regulation of RNA metabolism. Electrophysiologic studies of synaptic plasticity, models for learning and memory, are disrupted in Fragile X Syndrome (FXS). FXS is characterized by the loss of FMRP, an RNA-binding protein (RBP) known to suppress translation of specific neuronal RNAs. Synaptic plasticity in CA1 excitatory hippocampal neurons is protein-synthesis dependent, suggesting a role for FMRP in FXS-related synaptic deficits. To explore this model, we developed Opto-CLIP, integrating optogenetics with cell-type specific FMRP-CLIP and RiboTag in CA1 neurons, allowing investigation of activity-induced FMRP regulation. We tracked changes in FMRP binding and ribosome-associated RNA profiles 30 minutes after neuronal activation. Our findings reveal distinct temporal dynamics for FMRP transcript regulation in the cell body versus the synapse. In the cell body, FMRP binding to transcripts encoding nuclear functions is relieved, potentially allowing rapid transcriptional responses to neuronal activation. At the synapse, FMRP binding to transcripts encoding synaptic targets was relatively stable, with variability in translational control across target categories. These results offer fresh insights into the dynamic regulation of RNA by FMRP in response to neuronal activation and provide a foundation for future research into the mechanisms of RBP-mediated synaptic plasticity.