ASO-enhancement of TARDBP exitron splicing mitigates TDP-43 proteinopathies

Abstract

Amyotrophic lateral sclerosis and frontotemporal lobar degeneration are fatal neurodegenerative diseases characterized by pathological aggregation and nuclear functional loss of TDP-43^1,2. Current therapies inadequately address this core pathology^3,4, necessitating innovative approaches that target aggregation while preserving TDP-43’s essential functions. Here we demonstrate that enhancing the splicing of the TARDBP exitron—a cryptic intron encoding the aggregation-prone intrinsically disordered region (IDR) of TDP-43^5,6— effectively mitigates TDP-43 pathology. This exitron splicing event, directly regulated by nuclear TDP-43^7–9, suppresses the expression of IDR-containing TDP-43 isoforms and generates IDR-spliced-out TDP-43 isoforms^7,9,10 (which we term “IDRsTDP”). Our findings reveal that IDRsTDP, known to heterodimerize with full-length TDP-43¹⁰, inhibits TDP-43 aggregation by suppressing IDR-mediated clustering and enhances TDP-43 clearance via chaperone-mediated autophagy. In disease states, however, impaired nuclear TDP-43 function disrupts exitron splicing, leading to increased levels of IDR-containing TDP-43^9,11 and reduced levels of IDRsTDP, exacerbating aggregation and nuclear dysfunction^6,12–17. By identifying HNRNPA1 and HNRNPC as key repressors of TARDBP exitron splicing, we designed antisense oligonucleotides (ASOs) to block their binding and restore splicing. These ASOs suppressed TDP-43 pathology and neurodegeneration in both neuronal cell models with impaired nuclear transport and a mouse model of proteasome dysfunction-induced TDP-43 proteinopathy. Our strategy, by rescuing the impaired autoregulatory pathway, inhibits the pathological cycle of TDP-43 aggregation and nuclear dysfunction, offering a promising avenue for treating these currently intractable neurodegenerative diseases.