Human iPSC-derived motor neurons as a platform for elucidating TDP-43-related amyotrophic lateral sclerosis pathogenesis: a mini review

TAR DNA-binding protein 43 (TDP-43) is a major pathogenic RNA-binding protein associated with amyotrophic lateral sclerosis (ALS). Heterozygous mutations in TDP-43 cause familial ALS, known as ALS10. TDP-43 is predominantly localized in the nucleus under physiological conditions. Not only ALS patients with TARDBP mutations but also the majority of sporadic ALS patients exhibit TDP-43 pathology, which is defined by nuclear clearance and cytoplasmic aggregation. The inclusion of cryptic exons in genes such as STMN2 and UNC13A has emerged as a hallmark of TDP-43 loss of function, as demonstrated in TDP-43 knockdown models and postmortem analyses. However, it is not yet clear how TDP-43 levels and location change from healthy to pathological conditions in ALS. Motor neurons derived from induced pluripotent stem cells (iPSCs) have been widely used in ALS research and provide a promising platform to investigate early-stage disease mechanisms. However, challenges remain in generating models that faithfully recapitulate ALS pathogenesis. In this review, we summarize recent advances in TDP-43-related iPSC-derived motor neuron models and discuss future perspectives for elucidating ALS pathogenesis. We propose that longitudinal analyses of TDP-43 dynamics and co-culture systems will be essential to better model early ALS pathogenesis.