Defective EV-mediated transport of SHH alters neural fate specification in EPM1 epilepsy
- Andrea Forero
- Veronica Pravata
- Fabrizia Pipicelli
- Elisa Frenna
- Alessandro Soloperto
- Marta Ianni
- Natalia Abate
- Francesco Di Matteo
- Zagorka Bekjarova
- Laura Canafoglia
- Francesca Ragona
- Giuseppina Maccarrone
- Mariano Gonzalez Pisfil
- Christian Whal-Schott
- Filippo M. Cernilogar
- Matthias Eder
- Rossella Di Giaimo
- Silvia Cappello
2026-09-02
The extracellular milieu, including extracellular vesicles (EVs), plays a pivotal role in brain development. In this study, we sought to elucidate the pathogenesis of progressive myoclonus epilepsy type 1 (EPM1), a disease caused by mutations in the CSTB gene, using cerebral organoids (COs) derived from patient cells. The results demonstrate that EPM1 COs display increased electrophysiological activity and disrupted excitatory/inhibitory (E/I) balance. Single-cell RNA sequencing analysis of ventral EPM1-COs revealed an abnormal specification of progenitor fate, with a shift toward dorsal neuron identities. We demonstrated that this misspecification is driven by a functional alteration of the ventral signaling niche, resulting from impaired EV dynamics and altered protein cargo. Mechanistically, we identified Sonic Hedgehog (SHH) as a direct physical interactor of CSTB and demonstrated that CSTB deficiency leads to reduced SHH content and secretion. Our findings establish CSTB as a safeguard of ventral patterning and identify the CSTB-SHH-EV axis as a potential therapeutic target for mitigating the E/I imbalance associated with EPM1.