Cellular and molecular mechanisms of epileptogenesis in mTORopathies:From interneuron immaturity to RNA regulatory networks

Epilepsy affects approximately 50 million people worldwide, and genetic causes are increasingly recognized, particularly mTORopathies characterized by dysregulation of the mechanistic target of rapamycin pathway. Among these, Tuberous Sclerosis Complex (TSC) and Focal Cortical Dysplasia (FCD) are marked by cortical malformations, early-onset seizures, and frequent neurodevelopmental comorbidities such as autism spectrum disorder and intellectual disability. This thesis investigated how mTOR hyperactivation disrupts cortical development and drives epileptogenesis, focusing on inhibitory circuit formation. Single-nucleus transcriptomics of human tissue revealed that somatostatin-positive (SST⁺) GABAergic interneurons remain transcriptionally immature, retaining developmental markers, a neonatal chloride transporter profile, and immature GABAA receptor subunits. Histological analyses showed mislocalization to deeper cortical layers, indicating combined defects in migration and differentiation. These changes likely sustain depolarizing GABAergic signaling and increase seizure susceptibility. Further analyses identified altered somatostatin receptor expression, particularly SSTR3. Functional validation using Xenopus laevis oocyte microtransplantation demonstrated that SST receptor modulation directly alters human GABA currents, linking transcriptional changes to impaired inhibition. Single-cell ligand–receptor analyses revealed widespread disruptions in neuron–glia communication and extracellular matrix pathways across TSC and FCD, highlighting astrocytes as key contributors to network instability. Finally, circulating microRNAs predicting later neurodevelopmental comorbidities and stress-responsive astrocytic non-coding RNAs revealed translational biomarker opportunities. Together, these findings support a unifying model in which impaired interneuron maturation, disrupted SST signaling, and altered cell–cell communication converge to weaken cortical inhibition. This work provides mechanistic insight into mTORopathies and identifies therapeutic and biomarker strategies aimed at restoring inhibitory balance and improving clinical outcomes.