Identification of genes in toxicity pathways of trinucleotide-repeat RNA in C. elegans

Garcia, Susana M. D. A.; Tabach, Yuval; Lourenco, Guinevere F.; Armakola, Maria; Ruvkun, Gary

doi:10.1038/nsmb.2858

Cited by 24 publications

(42 citation statements)

References 47 publications

(52 reference statements)

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“…levels, unbiased screens expedite the discovery of new compounds and can identify unanticipated cellular targets. Small-molecule and genetic screens have been employed in the search for therapeutics as well as to inform interesting new biology associated with the CTG repeat expansion (13,(31)(32)(33)(34)(35)(36). However, a CTG repeat-selective screen targeting r(CUG) EXP production and/or stability in cells has not been reported.…”

Section: Significancementioning

confidence: 99%

A CTG repeat-selective chemical screen identifies microtubule inhibitors as selective modulators of toxic CUG RNA levels

Reddy

Jenquin

McConnell

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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A CTG repeat expansion in the DMPK gene is the causative mutation of myotonic dystrophy type 1 (DM1). Transcription of the expanded CTG repeat produces toxic gain-of-function CUG RNA, leading to disease symptoms. A screening platform that targets production or stability of the toxic CUG RNA in a selective manner has the potential to provide new biological and therapeutic insights. A DM1 HeLa cell model was generated that stably expresses a toxic r(CUG)480 and an analogous r(CUG)0 control from DMPK and was used to measure the ratio-metric level of r(CUG)480 versus r(CUG)0. This DM1 HeLa model recapitulates pathogenic hallmarks of DM1, including CUG ribonuclear foci and missplicing of pre-mRNA targets of the muscleblind (MBNL) alternative splicing factors. Repeat-selective screening using this cell line led to the unexpected identification of multiple microtubule inhibitors as hits that selectively reduce r(CUG)480 levels and partially rescue MBNL-dependent missplicing. These results were validated by using the Food and Drug Administration-approved clinical microtubule inhibitor colchicine in DM1 mouse and primary patient cell models. The mechanism of action was found to involve selective reduced transcription of the CTG expansion that we hypothesize to involve the LINC (linker of nucleoskeleton and cytoskeleton) complex. The unanticipated identification of microtubule inhibitors as selective modulators of toxic CUG RNA opens research directions for this form of muscular dystrophy and may shed light on the biology of CTG repeat expansion and inform therapeutic avenues. This approach has the potential to identify modulators of expanded repeat-containing gene expression for over 30 microsatellite expansion disorders.

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Section: Significancementioning

confidence: 99%

A CTG repeat-selective chemical screen identifies microtubule inhibitors as selective modulators of toxic CUG RNA levels

Reddy

Jenquin

McConnell

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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“…While direct evidence for what drives these transcript level changes is missing, several attractive hypotheses exist including depletion of other MBNL paralogues and increase in CELF1 activity. CUG exp RNA also disrupts other cellular processes including “leaching” of transcription factors (Ebralidze et al, ), abnormal DNA methylation (Lopez Castel et al, ), processing of repeats into small RNAs that produce unwanted gene silencing (Krol et al, ), activation of PKC‐dependent signaling pathways (Kuyumcu‐Martinez et al, ), bidirectional transcription (Nakamori et al, ), repeat associated non‐ATG translation (Zu et al, ), microRNA deregulation (Perbellini et al, ; Rau et al, ; Fernandez‐Costa et al, ; Kalsotra et al, ), and nonsense‐mediated decay pathway (Garcia et al, ). Some of these splicing‐independent abnormalities are discussed below.…”

Section: Pathology Beyond Splicingmentioning

confidence: 99%

“…The nonsense‐mediated decay (NMD) pathway is a surveillance mechanism that detects mRNA with premature stop codons and targets them for degradation to prevent the expression of potentially toxic truncated proteins (Chang et al, ). RNAi silencing of smg‐2, an RNA helicase component of the NMD pathway, in a DM1 C. elegans model causes an increase in CUG repeat containing mRNA (Garcia et al, ). Mutations in other NMD pathway genes, specifically smg‐1 and smg‐6, also resulted in a similar increase in CUG repeat RNA.…”

Section: Pathology Beyond Splicingmentioning

confidence: 99%

Developmental insights into the pathology of and therapeutic strategies for DM1: Back to the basics

Chau

Kalsotra

2015

Developmental Dynamics

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Myotonic Dystrophy type 1 (DM1), the most prevalent adult onset muscular dystrophy, is a trinucleotide repeat expansion disease caused by CTG expansion in the 3 0 -UTR of DMPK gene. This expansion results in the expression of toxic gain-of-function RNA that forms ribonuclear foci and disrupts normal activities of RNA-binding proteins belonging to the MBNL and CELF families. Changes in alternative splicing, translation, localization, and mRNA stability due to sequestration of MBNL proteins and up-regulation of CELF1 are key to DM1 pathology. However, recent discoveries indicate that pathogenic mechanisms of DM1 involves many other factors as well, including repeat associated translation, activation of PKC-dependent signaling pathway, aberrant polyadenylation, and microRNA deregulation. Expression of the toxic repeat RNA culminates in the developmental remodeling of the transcriptome, which produces fetal isoforms of proteins that are unable to fulfill the physiological requirements of adult tissues. This review will describe advances in the understanding of DM1 pathogenesis as well as current therapeutic developments for DM1. Developmental Dynamics 244:377-390, 2015. V C 2014 Wiley Periodicals, Inc.

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“…Collectively the data argue in favor of the temperature-sensitive dose-dependent proteotoxicity model involving the depletion of the chaperone system capacity required to buffer the combined load of the aggregation-prone cargo. Given the preliminary nature of our report, presently we can not conclusively exclude the other pathogenesis mediators, such us postulated RNA-repeat toxicity pathways (Nalavade et al 2013;Garcia et al 2014;Marti 2016), imposes on and contributes to the overall combined proteopathy phenotype (Li et al 2008). We note however, that overall length of expanded polyQ encoding (CAG) repeats used in our model might not suffice for significant RNArepeat toxicity (Finkbeiner 2011).…”

Section: Discussionmentioning

confidence: 84%

Caenorhabditis elegansmodel for admixed proteinopathy of Huntington’s and Alzheimer-type

Kapulkin

2019

Preprint

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Abbreviations: HD -Huntington disease; AD -Alzheimer disease; HTT -huntingtin; APPamyloid precursor protein; Aß42 -ß-amyloid peptide; ER -endoplasmic reticulum; HSP -heat shock protein; YFP -yellow fluorescent protein; co-IP -co-immunoprecipitation; RNAi -RNA interference; polyQ -polyglutamine ABSTRACT Formation of proteinaceous deposits composed of abnormally aggregated proteins characterizes a range of pathological conditions. Proteinaceous inclusions detected in the neurodegenerative conditions such Huntington's chorea (HD) and Alzheimer's disease (AD) are often referred as pathognomic and regarded as causally implicated. Despite of differences in aetiology and underlying genetics, rare cases of combined HD and AD were reported and described as admixed proteinopathies. Mixed proteopathies are characterized by the co-occurrence of at least two types of abnormal aggregation-prone variants; pathological deposition of proteinaceous inclusions might however, affect different cell populations. Here, combining plaques derived from human ß-amyloid with mutant HTT-like polyglutamine inclusions in a cell-autonomous manner, we report on the Caenorhabditis elegans model for admixed proteinopathy of Alzheimer's and Huntington's type. We show both types of intracellular foci are formed in vivo: non-amyloidic extended polyglutamine derived inclusions and distinguish those from the presence of mature ßamyloid fibers. We found that polyglutamines expanded above pathogenic threshold and ß-amyloid act synergistically to promote the progression of proteotoxicity in a temperature dependent manner.We further, implicate the hsp-1 (the predominant C. elegans chaperone interacting with ER-routed Aß42) modulate the proteotoxic insults observed in combined proteopathy model. Our results demonstrate how the in vivo model of admixed proteopathy could be utilized to probe for human pathogenic variants confined to the same cellular type. In that perspective expanded aggregationprone polyglutamines appended with fluorescent proteins could be regarded as 'pathogenic probes' useful in the proteotoxicity assays i.e. involving ß-amyloid and possibly other comparable models of disease-associated aggregation prone variants.We anticipate models of combined proteopathies will be informative regarding the underlying pathogenesis and provide the sensitized background

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Identification of genes in toxicity pathways of trinucleotide-repeat RNA in C. elegans

Cited by 24 publications

References 47 publications

A CTG repeat-selective chemical screen identifies microtubule inhibitors as selective modulators of toxic CUG RNA levels

A CTG repeat-selective chemical screen identifies microtubule inhibitors as selective modulators of toxic CUG RNA levels

Developmental insights into the pathology of and therapeutic strategies for DM1: Back to the basics

Caenorhabditis elegansmodel for admixed proteinopathy of Huntington’s and Alzheimer-type

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