Generation and validation of a human iPSC-derived TDP-43 knockout model for ALS disease modeling.

Nuclear depletion and cytoplasmic aggregation of TDP-43 occur in ~97% of amyotrophic lateral sclerosis (ALS) cases and disrupt RNA processing through aberrant cryptic exon inclusion. Existing cellular models rely on partial knockdown, TARDBP mutations, or pharmacological stress, each with limitations. Here, we generated homozygous TARDBP-knockout human iPSC lines using CRISPR-Cas9 and differentiated them into spinal motor neurons (MNs). Knockout MNs demonstrated ~16-fold lower differentiation efficiency than isogenic controls but retained neuronal marker expression. TDP-43 loss induced widespread cryptic exon inclusion and depletion of STMN2, UNC13A, and G3BP1. Integration of the CUTS splice biosensor yielded up to 4.5-fold cryptic GFP induction in knockout MNs, providing a reporter-based readout of TDP-43 dysfunction. Further, we validated the cardiac glycosides digoxin and ouabain as modulators of bortezomib-induced TDP-43 pathology. This genetically defined iPSC-derived MN model provides a platform for mechanistic and therapeutic interrogation of TDP-43-driven neurodegeneration in ALS.