Abstract
BackgroundParaspeckles are subnuclear bodies assembled on a long non-coding RNA (lncRNA) NEAT1. Their enhanced formation in spinal neurons of sporadic amyotrophic lateral sclerosis (ALS) patients has been reported but underlying mechanisms are unknown. The majority of ALS cases are characterized by TDP-43 proteinopathy. In current study we aimed to establish whether and how TDP-43 pathology may augment paraspeckle assembly.MethodsParaspeckle formation in human samples was analysed by RNA-FISH and laser capture microdissection followed by qRT-PCR. Mechanistic studies were performed in stable cell lines, mouse primary neurons and human embryonic stem cell-derived neurons. Loss and gain of function for TDP-43 and other microRNA pathway factors were modelled by siRNA-mediated knockdown and protein overexpression.ResultsWe show that de novo paraspeckle assembly in spinal neurons and glial cells is a hallmark of both sporadic and familial ALS with TDP-43 pathology. Mechanistically, loss of TDP-43 but not its cytoplasmic accumulation or aggregation augments paraspeckle assembly in cultured cells. TDP-43 is a component of the microRNA machinery, and recently, paraspeckles have been shown to regulate pri-miRNA processing. Consistently, downregulation of core protein components of the miRNA pathway also promotes paraspeckle assembly. In addition, depletion of these proteins or TDP-43 results in accumulation of endogenous dsRNA and activation of type I interferon response which also stimulates paraspeckle formation. We demonstrate that human or mouse neurons in vitro lack paraspeckles, but a synthetic dsRNA is able to trigger their de novo formation. Finally, paraspeckles are protective in cells with compromised microRNA/dsRNA metabolism, and their assembly can be promoted by a small-molecule microRNA enhancer.ConclusionsOur study establishes possible mechanisms behind paraspeckle hyper-assembly in ALS and suggests their utility as therapeutic targets in ALS and other diseases with abnormal metabolism of microRNA and dsRNA.
Highlights
Paraspeckles are subnuclear bodies assembled on a long non-coding RNA Nuclear enriched abundant transcript 1 (NEAT1)
A multifunctional RNA-binding protein TAR DNA-binding protein 43 (TDP-43) encoded by TARDBP gene is believed to be the main culprit in amyotrophic lateral sclerosis (ALS): TDP-43 pathology is typical for ~ 95% of sALS cases and for fALS cases caused by C9ORF72 gene mutation [2]; in addition, dozens of mutations in TARDBP have been identified in fALS and sALS patients
Presence of paraspeckles in the spinal cord neurons is a hallmark of sALS and fALS Augmented paraspeckle assembly has been previously reported in sALS spinal cord neurons as compared to non-ALS controls [20]
Summary
Paraspeckles are subnuclear bodies assembled on a long non-coding RNA (lncRNA) NEAT1. Their enhanced formation in spinal neurons of sporadic amyotrophic lateral sclerosis (ALS) patients has been reported but underlying mechanisms are unknown. [3, 4] Hallmarks of all these ALS cases include protein clearance from the nucleus, its cytoplasmic accumulation and aggregation [5, 6]. Both loss and gain of TDP-43 function are implicated in ALS the relative contribution of these two mechanisms is still debated. Functions of paraspeckles described so far include nuclear retention of specific RNAs, including inverted Alu repeat-containing transcripts; regulation of gene expression by sequestration of transcription factors; and modulation of miRNA biogenesis [13,14,15,16]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
