DNA Triplet Repeat Expansion and Mismatch Repair

Iyer, Ravi; Pluciennik, Anna; Напиерала, Марек; Wells, Robert D.

doi:10.1146/annurev-biochem-060614-034010

Cited by 110 publications

(112 citation statements)

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“…In HD, somatic instability is expansion‐biased and age‐ dependent, with larger tracts more susceptible to expansion 11, 12. It occurs in postmitotic neurons and is prominent in striatum and cortex, tissues particularly affected in HD 13.…”

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confidence: 99%

DNA repair pathways underlie a common genetic mechanism modulating onset in polyglutamine diseases

Bettencourt

Hensman-Moss

Flower

et al. 2016

Annals of Neurology

193

186

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ObjectiveThe polyglutamine diseases, including Huntington's disease (HD) and multiple spinocerebellar ataxias (SCAs), are among the commonest hereditary neurodegenerative diseases. They are caused by expanded CAG tracts, encoding glutamine, in different genes. Longer CAG repeat tracts are associated with earlier ages at onset, but this does not account for all of the difference, and the existence of additional genetic modifying factors has been suggested in these diseases. A recent genome‐wide association study (GWAS) in HD found association between age at onset and genetic variants in DNA repair pathways, and we therefore tested whether the modifying effects of variants in DNA repair genes have wider effects in the polyglutamine diseases.MethodsWe assembled an independent cohort of 1,462 subjects with HD and polyglutamine SCAs, and genotyped single‐nucleotide polymorphisms (SNPs) selected from the most significant hits in the HD study.ResultsIn the analysis of DNA repair genes as a group, we found the most significant association with age at onset when grouping all polyglutamine diseases (HD+SCAs; p = 1.43 × 10–5). In individual SNP analysis, we found significant associations for rs3512 in FAN1 with HD+SCAs (p = 1.52 × 10–5) and all SCAs (p = 2.22 × 10–4) and rs1805323 in PMS2 with HD+SCAs (p = 3.14 × 10–5), all in the same direction as in the HD GWAS.InterpretationWe show that DNA repair genes significantly modify age at onset in HD and SCAs, suggesting a common pathogenic mechanism, which could operate through the observed somatic expansion of repeats that can be modulated by genetic manipulation of DNA repair in disease models. This offers novel therapeutic opportunities in multiple diseases. Ann Neurol 2016;79:983–990

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mentioning

confidence: 99%

DNA repair pathways underlie a common genetic mechanism modulating onset in polyglutamine diseases

Bettencourt

Hensman-Moss

Flower

et al. 2016

Annals of Neurology

193

186

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“…Mismatch repair and error leading to mutagenesis is a complex mechanism involving several factors. As this mechanism is not the main focus of this review, we will only discuss a summarised version, since a current review describes the following paragraph in greater detail [28].…”

Section: Mutagenic Mismatch Repairmentioning

confidence: 99%

“…In particular, three proteins are vital in directing and facilitating post-replicative MMR; MutS, MutL and MutH, all with eukaryotic homologs (MSHs) [30]. These proteins generate a single strand break that serves as a gateway for exonuclease and DNA helicase II activity that leads to degradation of the newly synthesised strand, until the mismatch is removed [28]. Error occurs through two proposed models; 1) the MutSβ (MSH2 and MSH3 complex) entrapment/hairpin escape model 2) the dysregulated strand directionality model.…”

Section: Mutagenic Mismatch Repairmentioning

confidence: 99%

Polyglutamine ataxias: From Clinical and Molecular Features to Current Therapeutic Strategies

McIntosh¹,

Htut²,

Fletcher³

et al. 2017

J Genet Syndr Gene Ther

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Spinocerebellar ataxias are a large group of heterogeneous diseases that all involve selective neuronal degeneration and accompanied cerebellar ataxia. These diseases can be further broken down into discrete groups according to their underlying molecular genetic cause. The most common are the polyglutamine ataxias, of which there are six; Spinocerebellar ataxia type 1, 2, 3, 6, 7 and 17. These diseases are characterised by a pathological expanded cytosine-adenine-guanine (CAG) repeat sequence, in the protein coding region of a given gene. Common clinical features include lack of coordination and gait ataxia, speech and swallowing difficulties, as well as impaired hand and motor functions. The polyglutamine spinocerebellar ataxias are typically late onset diseases that are progressive in nature and often lead to premature death, for which there is currently no known cure or effective treatment strategy. Although caused by the same molecular mechanism, the causative gene and associated protein differ for each disease. The exact mechanism by which disease pathogenesis is caused remains elusive. However, the variable (CAG) n repeats are codons that may be translated to an expanded glutamine tract, leading to conformational changes in the protein, giving it a toxic gain of function. Several pathogenic pathways have been implicated in polyglutamine spinocerebellar ataxia diseases, such as the hallmark feature of neuronal nuclear inclusions, protein misfolding and aggregation, as well as transcriptional dysregulation. These pathways are attractive avenues for potential therapeutic interventions, as the potential to treat more than one disease exists. Research is ongoing, and several promising therapies are currently underway in an attempt to provide relief for this devastating class of diseases.. However, mutations can arise de novo, through errors in DNA replication such that two genetically healthy parents can give rise to an affected child.There are currently six characterised polyQ SCAs (1, 2, 3, 6, 7 and 17) (Table 1), and together with three other diseases, namely Huntington's disease, spinal and bulbar muscular atrophy and dentatorubropallidoluysian atrophy (DRPLA), form a larger category of polyQ diseases [7][8][9][10]. Th ere is little relief for individuals suffering from polyQ SCA disorders, with symptomatic treatments the only available option. Long term pharmacological treatment, although admirable, tends to fall short in an effective management strategy, as unwanted complications and low drug efficacy still exist. In addition, none of these diseases have any treatments that slow the progression of the disease; leaving affected individuals with the daunting reality that time may be a severe limiting factor. Several experimental approaches are currently being assessed to overcome these difficulties. This review will focus on the clinical and molecular features of polyQ SCA diseases (which will be referred to as SCA diseases), as well as highlight several promising and emerging therapeutic strategies...

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“…In particular, the ability to move seamlessly between in vivo and in vitro studies confers a tremendous advantage. In the future, the adaptation of reconstituted MMR systems holds great promise to examine other important cellular functions of MMR such as DNA repair and homologous recombination in somatic and meiotic cells (21), cellular responses to DNA damage (22), and triplet repeat expansion (23).…”

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confidence: 99%