Noncoding RNAs induce TDP43 pathology in the ALS-iPSC models

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron (MN) degenerative disease with a major pathological feature of cytoplasmic TDP-43 aggregation. However, the mechanisms underlying TDP-43 proteinopathy are still largely unknown. We performed in vitro differentiation of ALS-induced pluripotent stem cells (ALS-iPSCs; carrying the TDP-43M337V mutation) and isogenic controls and found upregulation of paraspeckle-associated lncRNA NEAT1 isoforms in the ALS-iPSC-derived MNs (ALS-iPSC-MNs). Intriguingly, the upregulated NEAT1 isoforms were mislocalized to the cytoplasm of ALS-iPSC-MNs, and the cytoplasmic NEAT1 provoked TDP-43 and TDP-43M337V liquid-liquid phase separation, generating long-lived protein condensates. These condensates had reduced mobility and were converted into aggregates, finally co-aggregating with phospho-TDP-43. Disruption of NEAT1 expression reduced its cytoplasmic levels and also reduced the levels of TDP-43/TDP-43M337V condensates. In 3D neuromuscular organoids with the TDP-43M337V mutation, treatment with NEAT1-antisense oligonucleotides (NEAT1-ASO) promoted neuromuscular junction formation and function, as well as muscle contractility. Furthermore, treatment of TDP-43Q331K mice with Neat1-ASO attenuated TDP-43 pathology in spinal cord and preserved motor function. These findings suggest that NEAT1 plays an important role in TDP-43-associated pathology, and NEAT1-ASO may attenuate pathological TDP-43 aggregation to prevent motor neuron degeneration and muscle weakness in ALS. GFP+ motor neurons were sorted from in vitro motor neuron differentiation for RNA extraction and hybridization on Affymetrix microarrays. We sought to identify consistent upregulated or downregulated noncoding RNAs in the ALS-iPSC-motor neuron as compared to isogenic counterparts, two pair set of microarray were performed from iTDP#2 and iTDP#3 and the isogenic lines