TDP-43 mislocalization disrupts potassium channel RNA splicing in patient-derived ALS neurons, producing hyperexcitability correctable by antisense oligonucleotide

Kiskinis lab staff differentiated stem cells from multiple sporadic ALS donors and introduced TDP-43 knockdown or cytoplasmic mislocalization. Whole-cell patch-clamp recordings showed increased action-potential firing frequency and loss of the slow after-hyperpolarization current carried by the affected potassium channel. RNA-seq and splicing assays identified a single cryptic exon inclusion event that introduced a premature stop codon, confirmed in post-mortem motor cortex from the same patients.

The finding links three previously separate observations: early cortical hyperexcitability on TMS, TDP-43 nuclear clearance, and faster progression in patients with prominent excitability changes. Because the same channel defect is absent in C9orf72 or SOD1 models, the mechanism is selective for sporadic disease, which accounts for 90 percent of cases and lacks approved disease-modifying therapies.

An 18-mer antisense oligonucleotide designed to sterically block the cryptic splice site restored the canonical transcript, normalized channel current density, and lowered firing rates to control levels within 72 hours. The molecule is chemically identical in backbone to the approved SMA drug nusinersen, allowing reuse of established intrathecal delivery and safety data packages.

The group has completed rodent toxicology and begun large-animal biodistribution studies; first-in-human dosing is projected inside 24 months if GLP safety margins are met. Parallel banking of 200 sporadic ALS iPSC lines is intended to test whether the same splicing defect appears in additional genetic backgrounds.