The TDP-43I383V heterozygous mutation results in increased TDP-43 expression and altered neuronal activity in ALS patient-derived iPSC motor neurons

TAR-binding protein 43 (TDP-43) is a pathogenic RNA-binding protein associated with amyotrophic lateral sclerosis (ALS). To elucidate the pathogenesis of ALS, we generated induced pluripotent stem cells (iPSCs) from lymphoblastoid cell line (LCL) cells of an ALS patient with the TDP-43^I383V heterozygous mutation. Furthermore, we generated isogenic wild-type iPSCs from wild-type LCL cells using scarless genome editing with CRISPR/Cas9. A modified iPSC-derived motor neuron culture method utilizing BrainPhys neuronal medium and rat astrocyte co-culture effectively promoted and maintained neuronal activity. Under these conditions, the TDP-43^I383V heterozygous mutation resulted in increased TDP-43 protein expression through prolonged stabilization. Moreover, mutant iPSC-derived motor neurons showed increased numbers of pre-synapses and altered neuronal activity. These results suggest that the modified motor neuron culture method can help elucidate abnormalities in TDP-43 expression, synapse formation, and neuronal activity caused by the heterozygous TDP-43^I383V mutation. The model developed in this study has the potential to facilitate the analysis of the early pathological phenotype of ALS.