Project description: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.
Project description:Mislocalization of the nuclear protein TDP43 is a hallmark of ALS and FTD and leads to de-repression and inclusion of cryptic exons, which represent promising biomarkers of TDP43 pathology. However, most cryptic exons to date have been identified from in vitro models, limiting our understanding of any tissue and/or cell-specific splices. We meta-analyzed published bulk RNA-Seq datasets representing 1,778 RNAseq profiles of ALS and FTD post mortem tissue, and in vitro models with experimentally depleted TDP43. We identified novel cryptic splices and mapped out their tissue-specificity, demonstrating subsets with distinct cortical and spinal cord enrichment. Novel events were validated by RNA-Seq and RT-qPCR in a new spinal cord cohort, and analysis of single-nucleus datasets localized cortical splices to layer-specific neuronal populations. This catalog of cryptic splices is the first step towards the development of biomarkers for cell type-specific TDP43 pathology.
Project description:TDP43 inclusion bodies are widely present in the majority of patients with familial and sporadic amyotrophic lateral sclerosis (ALS). The mechanisms regulating TDP43 solubility remain incompletely understood. Here, we report that TDP43 undergoes S-acylation primarily at the Cys244 residue by the S-acyltransferase zDHHC23. This S-acylation maintains the liquid-like properties of TDP43 by reducing the aberrant interaction with poly(ADP-ribose) polymerase 1 (PARP1) and PARylated proteins, thereby countering the pathological condensation of TDP43. S-acylation-deficient TDP43 inclusions sequester the translational machinery and inhibit cytoplasmic protein translation, ultimately resulting in neurotoxicity. Importantly, TDP43 S-acylation is decreased in the familial ALS-associated TDP43 mutants as well as in SOD1-G93A mice and C9orf72-ALS induced pluripotent stem cell (iPSC)-derived neurons, suggesting the widespread involvement of TDP43 S-acylation in ALS pathogenesis. Our findings reveal an undescribed modification of TDP43 and provide deeper insight into the regulation of TDP43 pathological condensation in ALS.
Project description:TDP43 is involved in microRNA biogenesis and found in cytoplasmic aggregates in amyotrophic lateral sclerosis (ALS), and microRNAs are important for regulation of gene expression and represent potential biomarkers and therapeutic targets. Therefore, we examined microRNAs that preferentially bind cytoplasmic TDP43 using cellular models expressing TDP43 variants and NanoString miRNA profiling analyses. We identified cytoplasmic TDP43-associated miRNAs and predicted genes and pathways to gain insights into potentially relevant disease pathways, biomarkers, and reversible therapeutic targets for ALS.
Project description:The majority of individuals with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) exhibit neuronal cytoplasmic inclusions rich in the RNA binding protein TDP43. Even so, the relationship between TDP43’s RNA binding properties and neurodegeneration remain obscure. Here we show that engineered mutations disrupting a salt bridge between TDP43’s RNA recognition motifs interfere with nucleic acid binding and eliminate recognition of native TDP43 substrates. The accumulation of WT TDP43, but not RNA binding-deficient variants, disproportionately affected the abundance and splicing of encoding ribosome and oxidative phosphorylation components.
Project description:Amyotrophic lateral sclerosis is the most common and fatal motor neuron disease. Approximately 90% of ALS patients exhibit pathology of the master RNA regulator, Transactive Response DNA Binding protein (TDP-43). Despite the prevalence TDP-43 pathology in ALS motor neurons, recent findings suggest immune dysfunction is a determinant of disease progression in patients. Whether TDP-43 aggregates elicit immune responses remains underexplored. In this study, we demonstrate that TDP-43 aggregates are internalized by antigen presenting cell populations, cause vesicle rupture, and drive innate and adaptive immune cell activation by way of antigen presentation. Using a multiplex imaging platform, we observed enrichment of activated microglia/macrophages in ALS white matter that correlated with phosphorylated TDP-43 accumulation, CD8 T-cell infiltration, and major histocompatibility complex expression. Taken together, this study sheds light on a novel cellular response to TDP43 aggregates through an immunological lens.
Project description:Amyotrophic lateral sclerosis is the most common and fatal motor neuron disease. Approximately 90% of ALS patients exhibit pathology of the master RNA regulator, Transactive Response DNA Binding protein (TDP-43). Despite the prevalence TDP-43 pathology in ALS motor neurons, recent findings suggest immune dysfunction is a determinant of disease progression in patients. Whether TDP-43 aggregates elicit immune responses remains underexplored. In this study, we demonstrate that TDP-43 aggregates are internalized by antigen presenting cell populations, cause vesicle rupture, and drive innate and adaptive immune cell activation by way of antigen presentation. Using a multiplex imaging platform, we observed enrichment of activated microglia/macrophages in ALS white matter that correlated with phosphorylated TDP-43 accumulation, CD8 T-cell infiltration, and major histocompatibility complex expression. Taken together, this study sheds light on a novel cellular response to TDP43 aggregates through an immunological lens.
Project description:Aggregation of proteins under cellular stress plays key roles in age-related degenerative diseases, but how different proteins coalesce to form inclusions that vary in composition, morphology, molecular dynamics and physiological consequences is poorly understood. We employed a general reporter to identify proteins forming aggregates under proteotoxic stress in human cells. Over 300 proteins were identified, forming different inclusions containing subsets of aggregating proteins. In particular, TDP43, implicated in Amyotrophic Lateral Sclerosis (ALS), partitions dynamically between two distinct types of aggregates: stress granule (SG) and a previously unknown solid inclusion containing components of the ER exit sites (ERES), such as SEC16A. TDP43 accumulation at ERES is antagonized by SG assembly, but enhanced by certain ALS-associated mutations. TDP43-ERES aggregation biases toward nascent TDP43 and, unlike SG, does not contain RNA. Such aggregation causes defects in ER-to-Golgi protein transport, providing a link between TDP43 aggregation and compromised cellular function in ALS patient neurons.