Glioma epileptiform activity and progression are driven by IGSF3 mediated potassium dysregulation [mouse]

Seizures are a pathophysiological feature of malignant glioma. Recent studies implicate peritumoral synaptic dysregulation as a driver of neuronal hyperactivity and tumor progression, however, the molecular mechanisms that govern these phenomena remain elusive. Using scRNA-seq and intraoperative patient ECoG recordings, we show that tumors from seizure patients are enriched for gene signatures regulating synapse formation. Employing a human-to-mouse in vivo functionalization pipeline to screen these gene sets, we identified IGSF3 as a mediator of glioma progression and dysregulated neural circuitry in the form of spreading depolarization (SD). Mechanistically, we discovered that IGSF3 interacts with Kir4.1 to suppress potassium buffering and found that seizure patients exhibit reduced expression of potassium handlers in proliferating tumor cells. In vivo imaging revealed dysregulated synaptic activity emanates from the tumor-neuron interface, which we confirmed in patients. Our studies reveal that tumor progression and seizures are enabled by ion dyshomeostasis and identify SD as a driver of disease. Overall design: Single-celll RNA-sequencing of piggyBac in utero electroporation tumors