Impact of the CYFIP2 R87C variant in a human neuronal model in vitro.

Mutations in the CYFIP2 gene, particularly the R87C variant, are associated with severe epileptic encephalopathy, and present challenges for therapeutic development. This study utilized CRISPR/Cas9-edited human pluripotent stem cell (hPSC) lines to investigate the impact of R87C variant on neuronal morphology and function. hPSCs were differentiated into neural progenitor cells (NPCs), cortical neurons (CNs), and cortical organoids. Phenotypic characterization included immunofluorescence, scanning electron microscopy (SEM), high-throughput scanning (HTS), multi-electrode array (MEA) recordings, and Western blotting. Edited hPSC lines maintained pluripotency, and neurogenic differentiation yielded NPCs and CNs without significant differences in neural progenitor marker expression. However, mutated NPCs exhibited reduced motility in cell tracking assays, and SEM revealed altered cell morphology, suggesting an impact on lamellipodia formation. While both mutant and wild-type CNs expressed appropriate neuronal and glial markers and showed similar electrophysiological properties, R87C/R87C cortical organoids displayed decreased CYFIP2 protein levels and, by day 30, showed increased size alongside an absence of SOX2 + cells, suggesting premature depletion of the progenitor pool. These findings highlight a marked divergence between 2D and 3D models, with organoids revealing neurodevelopmental abnormalities not evident in monolayer cultures. Together, our results suggest that the CYFIP2 R87C variant impacts NPC cytoskeletal dynamics and early cortical development, warranting further investigation into its role in epileptic encephalopathy.