Project description:ATAC-seq was utilized to profile the chromatin status in ALS/FTD patient cells carrying the hexanuleotide repeat expansion in C9orf72.
Project description:Dysregulation of RNA processing contributes to neurodegenerative diseases, especially amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Expansion of an intronic (GGGGCC)n repeat within the C9ORF72 gene is the most common cause of both FTD and ALS (C9-FTD/ALS), characterized with aberrant repeat RNA foci in the nucleus and noncanonical translation-produced dipeptide repeat (DPR) protein inclusions in the cytoplasm. Here we elucidate that the (GGGGCC)n repeat RNA co-localizes with nuclear speckles and alters their phase separation properties and granule dynamics. Moreover, the essential nuclear speckle scaffold protein SRRM2 is sequestered into the poly-GR cytoplasmic inclusions in C9-FTD/ALS mouse model and patient postmortem tissues, exacerbating the nuclear speckle dysfunction. Impaired nuclear speckle integrity induces global exon-skipping and intron retention in human iPSC-derived neurons. Similar alternative splicing changes can be found in patient postmortem tissues. This work identified novel molecular mechanism of global RNA splicing defects by impaired nuclear speckle function in C9-FTD/ALS and revealed novel potential biomarkers or therapeutic targets.
Project description:A hexanucleotide repeat expansion (HRE) in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Human imaging and experimental studies hint at early changes in the brain in C9-ALS/FTD, which remain poorly understood. To define these changes, we used cerebral organoid models derived from C9-ALS/FTD patients and controls to create a single cell RNA sequencing dataset at day 90. Together, these dataset will help to shed light on initial pathologies crucial for understanding disease onset and the design of therapeutic strategies.
Project description:We report a conserved transcriptomic signature of reduced fatty acid and lipid metabolism gene expression in human post-mortem ALS spinal cord and a Drosophila model of the most common genetic cause of FTD/ALS, a repeat expansion in C9orf72. To investigate lipid alterations, we performed lipidomics on C9FTD/ALS iPSC-neurons and post-mortem FTLD brain tissue. This revealed a common and specific reduction in phospholipid species containing polyunsaturated fatty acids (PUFAs). To determine whether this PUFA deficit contributes to neurodegeneration, we fed C9FTD/ALS flies PUFAs, which yielded a modest increase in survival. However, increasing PUFA levels specifically in neurons of the C9orf72 flies, by overexpressing fatty acid desaturase enzymes, led to a substantial extension of lifespan. Neuronal overexpression of fatty acid desaturases also suppressed stressor induced neuronal death in C9FTD/ALS patient iPSC-neurons. These data implicate neuronal fatty acid saturation in the pathogenesis of FTD/ALS and suggest that interventions to increase PUFA levels specifically within neurons will be beneficial.
Project description:Single cell RNA sequencing data was collected from 150 day old human cortical organoid slice cultures grown at the air-liquid interface (ALI-COs) from control and ALS/FTD patient-specific induced pluripotent stem cell (iPSC) lines harbouring the C9ORF72 hexanucleotide repeat expansion mutation. Data collection included ALI-COs derived from the following iPSC lines: WTSli042-B (WTS42b) and A18945 (EpiC) for healthy controls, CS30iALS-C9nxx (CS30) and CS29iALS-C9nxx (CS29) for ALS/FTD, and CS29iALS-C9n1.ISOxx (ISO29), a mutation-corrected isogenic line. A total of 148,223 cells were processed over two batches.
Project description:While deleterious mutations are responsible for the vast majority of TBK1-linked ALS/FTD cases, the ALS/FTD causing missense mutation p.E696K leads to a selective loss of TBK1/optineurin binding. Knock-in of this specific missense mutation causes progressive autophagolysosomal dysfunction and an ALS/FTD-like phenotype in mice, while, as opposed to TBK1 deletion, RIPK/TNF-α-dependent necroptosis or overt inflammation are absent. Our results highlight the role of autophagolysosomal dysfunction as a therapeutic target in TBK1-ALS/FTD.
