Synaptic abnormalities in iPSC-derived neurons from E200K carriers

Introduction: Genetic Creutzfeldt-Jakob Disease (gCJD) is most commonly caused by the E200K mutation in the PRNP gene. In this study, we used induced pluripotent stem cells (iPSCs) from a multigenerational Israeli family carrying the E200K mutation to investigate synaptic abnormalities associated with gCJD. Objectives: To investigate synaptic abnormalities in iPSC-derived cortical neurons from E200K carriers, with a focus on NMDA receptor (NMDAR) distribution and extrasynaptic excitotoxicity. Methods: Immunofluorescence staining was used to localize NMDARs at postsynaptic terminals. Bulk RNA sequencing of iPSC-derived cortical neurons from E200K carriers and co-isogenic corrected controls assessed transcriptomic changes. Electrophysiological and calcium signaling alterations were evaluated using Multi-Electrode Array (MEA) recordings and calcium influx assays. Results/Discussion: E200K iPSC-derived cortical neurons exhibited significantly elevated levels of extrasynaptic NMDARs compared to their co-isogenic controls. RNA sequencing revealed a marked downregulation of brain-derived neurotrophic factor (BDNF) gene expression in E200K carriers. Preliminary calcium influx experiments demonstrated heightened calcium entry in response to exogenous NMDAR activation. The observed increase in extrasynaptic NMDARs, coupled with reduced BDNF expression—both of which have been interlinked in various neurodegenerative disorders—suggests a potential early disease phenotype in neuronal networks of E200K carriers. Conclusion: The E200K mutation in the PRNP gene promotes the extrasynaptic localization of NMDARs and leads to downregulation of BDNF gene expression. Activation of these extrasynaptic NMDARs triggers a pronounced increase in calcium influx, which disrupts neuronal electrical activity and contributes to excitotoxicity in neuronal cultures.