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Rajan-Babu IS, Dolzhenko E, Eberle MA, Friedman JM. Sequence composition changes in short tandem repeats: heterogeneity, detection, mechanisms and clinical implications. Nat Rev Genet 2024; 25:476-499. [PMID: 38467784 DOI: 10.1038/s41576-024-00696-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2024] [Indexed: 03/13/2024]
Abstract
Short tandem repeats (STRs) are a class of repetitive elements, composed of tandem arrays of 1-6 base pair sequence motifs, that comprise a substantial fraction of the human genome. STR expansions can cause a wide range of neurological and neuromuscular conditions, known as repeat expansion disorders, whose age of onset, severity, penetrance and/or clinical phenotype are influenced by the length of the repeats and their sequence composition. The presence of non-canonical motifs, depending on the type, frequency and position within the repeat tract, can alter clinical outcomes by modifying somatic and intergenerational repeat stability, gene expression and mutant transcript-mediated and/or protein-mediated toxicities. Here, we review the diverse structural conformations of repeat expansions, technological advances for the characterization of changes in sequence composition, their clinical correlations and the impact on disease mechanisms.
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Affiliation(s)
- Indhu-Shree Rajan-Babu
- Department of Medical Genetics, The University of British Columbia, and Children's & Women's Hospital, Vancouver, British Columbia, Canada.
| | | | | | - Jan M Friedman
- Department of Medical Genetics, The University of British Columbia, and Children's & Women's Hospital, Vancouver, British Columbia, Canada
- BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
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2
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Shao YR, Yu JY, Ma Y, Dong Y, Wu ZY. CAT Interruption as a Protective Factor in Chinese Patients with Spinocerebellar Ataxia Type 1. CEREBELLUM (LONDON, ENGLAND) 2024; 23:1211-1214. [PMID: 37491649 DOI: 10.1007/s12311-023-01586-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/06/2023] [Indexed: 07/27/2023]
Abstract
Spinocerebellar ataxia type 1 (SCA1) is the third most common type of spinocerebellar ataxias in China. CAT interruptions in the pathogenic alleles of SCA1 patients had only been reported by limited documents and there was a lack of data based on the Chinese population. In this study, we detected CAT interrupted pathogenic alleles in SCA1 patients from 4 out of 79 (5.1%) Chinese families. Their total CAG repeats were larger (median 58 vs. 47, p < 0.001) but ages at onset were later (median 46 vs. 38, p = 0.020). The longest uninterrupted CAG repeats could explain 65.4% of the AAO variance, making an increase of 28.0% compared to the total CAG repeats. The interruption pattern was greatly different between Chinese cohort and Caucasian cohort, indicating the effect of race.
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Affiliation(s)
- Ya-Ru Shao
- Department of Neurology and Department of Medical Genetics in the Second Affiliated Hospital and Key Laboratory of Medical Neurobiology of Zhejiang Province, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China
| | - Jin-Yang Yu
- Department of Neurology and Department of Medical Genetics in the Second Affiliated Hospital and Key Laboratory of Medical Neurobiology of Zhejiang Province, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China
| | - Yin Ma
- Department of Neurology and Department of Medical Genetics in the Second Affiliated Hospital and Key Laboratory of Medical Neurobiology of Zhejiang Province, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China
| | - Yi Dong
- Department of Neurology and Department of Medical Genetics in the Second Affiliated Hospital and Key Laboratory of Medical Neurobiology of Zhejiang Province, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Zhi-Ying Wu
- Department of Neurology and Department of Medical Genetics in the Second Affiliated Hospital and Key Laboratory of Medical Neurobiology of Zhejiang Province, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China.
- MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, China.
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3
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Kacher R, Lejeune FX, David I, Boluda S, Coarelli G, Leclere-Turbant S, Heinzmann A, Marelli C, Charles P, Goizet C, Kabir N, Hilab R, Jornea L, Six J, Dommergues M, Fauret AL, Brice A, Humbert S, Durr A. CAG repeat mosaicism is gene specific in spinocerebellar ataxias. Am J Hum Genet 2024; 111:913-926. [PMID: 38626762 PMCID: PMC11080609 DOI: 10.1016/j.ajhg.2024.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 03/25/2024] [Accepted: 03/25/2024] [Indexed: 04/18/2024] Open
Abstract
Expanded CAG repeats in coding regions of different genes are the most common cause of dominantly inherited spinocerebellar ataxias (SCAs). These repeats are unstable through the germline, and larger repeats lead to earlier onset. We measured somatic expansion in blood samples collected from 30 SCA1, 50 SCA2, 74 SCA3, and 30 SCA7 individuals over a mean interval of 8.5 years, along with postmortem tissues and fetal tissues from SCA1, SCA3, and SCA7 individuals to examine somatic expansion at different stages of life. We showed that somatic mosaicism in the blood increases over time. Expansion levels are significantly different among SCAs and correlate with CAG repeat lengths. The level of expansion is greater in individuals with SCA7 who manifest disease compared to that of those who do not yet display symptoms. Brain tissues from SCA individuals have larger expansions compared to the blood. The cerebellum has the lowest mosaicism among the studied brain regions, along with a high expression of ATXNs and DNA repair genes. This was the opposite in cortices, with the highest mosaicism and lower expression of ATXNs and DNA repair genes. Fetal cortices did not show repeat instability. This study shows that CAG repeats are increasingly unstable during life in the blood and the brain of SCA individuals, with gene- and tissue-specific patterns.
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Affiliation(s)
- Radhia Kacher
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - François-Xavier Lejeune
- Sorbonne Université, Paris Brain Institute's Data Analysis Core Facility, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Isabelle David
- Sorbonne Université, Department of Genetics, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Susana Boluda
- Sorbonne Université, Department of Neuropathology Raymond Escourolle, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Giulia Coarelli
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Sabrina Leclere-Turbant
- Sorbonne Université, Biobank Neuro-CEB Biological Resource Platform, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Anna Heinzmann
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Cecilia Marelli
- MMDN, Université Montpellier, EPHE, INSERM, Montpellier, France; Expert Center for Neurogenetic Diseases, CHU, Montpellier, France
| | - Perrine Charles
- Sorbonne Université, Department of Genetics, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Cyril Goizet
- Université Bordeaux, Equipe « Neurogénétique Translationnelle - NRGEN », INCIA CNRS UMR5287 Université Bordeaux and Centre de Reference Maladies Rares « Neurogénétique », Service de Génétique Médicale, Bordeaux University Hospital (CHU Bordeaux), Bordeaux, France
| | - Nisha Kabir
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Rania Hilab
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Ludmila Jornea
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Julie Six
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Marc Dommergues
- Sorbonne Université, Service de Gynécologie Obstetrique, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Anne-Laure Fauret
- Sorbonne Université, Department of Genetics, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Alexis Brice
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Sandrine Humbert
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France
| | - Alexandra Durr
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, APHP, Hopital de la Pitié-Salpêtrière, Paris, France.
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TR-FRET-Based Immunoassay to Measure Ataxin-2 as a Target Engagement Marker in Spinocerebellar Ataxia Type 2. Mol Neurobiol 2023; 60:3553-3567. [PMID: 36894829 PMCID: PMC10122633 DOI: 10.1007/s12035-023-03294-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 02/22/2023] [Indexed: 03/11/2023]
Abstract
Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominantly inherited neurodegenerative disease, which belongs to the trinucleotide repeat disease group with a CAG repeat expansion in exon 1 of the ATXN2 gene resulting in an ataxin-2 protein with an expanded polyglutamine (polyQ)-stretch. The disease is late manifesting leading to early death. Today, therapeutic interventions to cure the disease or even to decelerate disease progression are not available yet. Furthermore, primary readout parameter for disease progression and therapeutic intervention studies are limited. Thus, there is an urgent need for quantifiable molecular biomarkers such as ataxin-2 becoming even more important due to numerous potential protein-lowering therapeutic intervention strategies. The aim of this study was to establish a sensitive technique to measure the amount of soluble polyQ-expanded ataxin-2 in human biofluids to evaluate ataxin-2 protein levels as prognostic and/or therapeutic biomarker in SCA2. Time-resolved fluorescence energy transfer (TR-FRET) was used to establish a polyQ-expanded ataxin-2-specific immunoassay. Two different ataxin-2 antibodies and two different polyQ-binding antibodies were validated in three different concentrations and tested in cellular and animal tissue as well as in human cell lines, comparing different buffer conditions to evaluate the best assay conditions. We established a TR-FRET-based immunoassay for soluble polyQ-expanded ataxin-2 and validated measurements in human cell lines including iPSC-derived cortical neurons. Additionally, our immunoassay was sensitive enough to monitor small ataxin-2 expression changes by siRNA or starvation treatment. We successfully established the first sensitive ataxin-2 immunoassay to measure specifically soluble polyQ-expanded ataxin-2 in human biomaterials.
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Taylor A, Barros D, Gobet N, Schuepbach T, McAllister B, Aeschbach L, Randall E, Trofimenko E, Heuchan E, Barszcz P, Ciosi M, Morgan J, Hafford-Tear N, Davidson A, Massey T, Monckton D, Jones L, network REGISTRYH, Xenarios I, Dion V. Repeat Detector: versatile sizing of expanded tandem repeats and identification of interrupted alleles from targeted DNA sequencing. NAR Genom Bioinform 2022; 4:lqac089. [PMID: 36478959 PMCID: PMC9719798 DOI: 10.1093/nargab/lqac089] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 10/25/2022] [Accepted: 11/08/2022] [Indexed: 12/07/2022] Open
Abstract
Targeted DNA sequencing approaches will improve how the size of short tandem repeats is measured for diagnostic tests and preclinical studies. The expansion of these sequences causes dozens of disorders, with longer tracts generally leading to a more severe disease. Interrupted alleles are sometimes present within repeats and can alter disease manifestation. Determining repeat size mosaicism and identifying interruptions in targeted sequencing datasets remains a major challenge. This is in part because standard alignment tools are ill-suited for repetitive and unstable sequences. To address this, we have developed Repeat Detector (RD), a deterministic profile weighting algorithm for counting repeats in targeted sequencing data. We tested RD using blood-derived DNA samples from Huntington's disease and Fuchs endothelial corneal dystrophy patients sequenced using either Illumina MiSeq or Pacific Biosciences single-molecule, real-time sequencing platforms. RD was highly accurate in determining repeat sizes of 609 blood-derived samples from Huntington's disease individuals and did not require prior knowledge of the flanking sequences. Furthermore, RD can be used to identify alleles with interruptions and provide a measure of repeat instability within an individual. RD is therefore highly versatile and may find applications in the diagnosis of expanded repeat disorders and in the development of novel therapies.
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Affiliation(s)
- Alysha S Taylor
- UK Dementia Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ, UK
| | - Dinis Barros
- Centre for Integrative Genomics, University of Lausanne, Bâtiment Génopode, 1015 Lausanne, Switzerland
| | - Nastassia Gobet
- Centre for Integrative Genomics, University of Lausanne, Bâtiment Génopode, 1015 Lausanne, Switzerland
| | - Thierry Schuepbach
- Vital-IT Group, Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
- Newbiologix, Ch. De la corniche 6-8, 1066 Epalinges, Switzerland
| | - Branduff McAllister
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff CF24 4HQ, UK
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Lorene Aeschbach
- Centre for Integrative Genomics, University of Lausanne, Bâtiment Génopode, 1015 Lausanne, Switzerland
| | - Emma L Randall
- UK Dementia Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ, UK
| | - Evgeniya Trofimenko
- Centre for Integrative Genomics, University of Lausanne, Bâtiment Génopode, 1015 Lausanne, Switzerland
- Sorbonne Université, École normale supérieure, PSL University, CNRS, Laboratoire des biomolécules, LBM, 75005 Paris, France
| | - Eleanor R Heuchan
- UK Dementia Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ, UK
| | - Paula Barszcz
- Centre for Integrative Genomics, University of Lausanne, Bâtiment Génopode, 1015 Lausanne, Switzerland
| | - Marc Ciosi
- School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, Davidson Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Joanne Morgan
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff CF24 4HQ, UK
| | | | - Alice E Davidson
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL UK
| | - Thomas H Massey
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff CF24 4HQ, UK
| | - Darren G Monckton
- School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, Davidson Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Lesley Jones
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff CF24 4HQ, UK
| | | | - Ioannis Xenarios
- Centre for Integrative Genomics, University of Lausanne, Bâtiment Génopode, 1015 Lausanne, Switzerland
- Health2030 Genome Center, Ch des Mines 14, 1202 Genève, Switzerland
| | - Vincent Dion
- UK Dementia Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ, UK
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Donaldson J, Powell S, Rickards N, Holmans P, Jones L. What is the Pathogenic CAG Expansion Length in Huntington's Disease? J Huntingtons Dis 2021; 10:175-202. [PMID: 33579866 PMCID: PMC7990448 DOI: 10.3233/jhd-200445] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Huntington's disease (HD) (OMIM 143100) is caused by an expanded CAG repeat tract in the HTT gene. The inherited CAG length is known to expand further in somatic and germline cells in HD subjects. Age at onset of the disease is inversely correlated with the inherited CAG length, but is further modulated by a series of genetic modifiers which are most likely to act on the CAG repeat in HTT that permit it to further expand. Longer repeats are more prone to expansions, and this expansion is age dependent and tissue-specific. Given that the inherited tract expands through life and most subjects develop disease in mid-life, this implies that in cells that degenerate, the CAG length is likely to be longer than the inherited length. These findings suggest two thresholds- the inherited CAG length which permits further expansion, and the intracellular pathogenic threshold, above which cells become dysfunctional and die. This two-step mechanism has been previously proposed and modelled mathematically to give an intracellular pathogenic threshold at a tract length of 115 CAG (95% confidence intervals 70- 165 CAG). Empirically, the intracellular pathogenic threshold is difficult to determine. Clues from studies of people and models of HD, and from other diseases caused by expanded repeat tracts, place this threshold between 60- 100 CAG, most likely towards the upper part of that range. We assess this evidence and discuss how the intracellular pathogenic threshold in manifest disease might be better determined. Knowing the cellular pathogenic threshold would be informative for both understanding the mechanism in HD and deploying treatments.
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Affiliation(s)
- Jasmine Donaldson
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Sophie Powell
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Nadia Rickards
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Peter Holmans
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Lesley Jones
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
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Frequency and distribution of polyQ disease intermediate-length repeat alleles in healthy Italian population. Neurol Sci 2020; 41:1475-1482. [PMID: 31940111 DOI: 10.1007/s10072-019-04233-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 12/30/2019] [Indexed: 12/13/2022]
Abstract
BACKGROUND Huntington disease (HD) and spinocerebellar ataxia type 1-2-17 (SCA1-2-17) are adult-onset autosomal dominant diseases, caused by triplet repeat expansions in the HTT, ATXN1, ATXN2, and TBP genes. Alleles with a repeat number just below the pathological threshold are associated with reduced penetrance and meiotic instability and are defined as intermediate alleles (IAs). OBJECTIVES We aimed to determine the frequencies of IAs in healthy Italian subjects and to compare the proportion of the IAs with the prevalence of the respective diseases. METHODS We analyzed the triplet repeat size in HTT, ATXN1, ATXN2, and TBP genes in the DNA samples from 729 consecutive adult healthy Italian subjects. RESULTS IAs associated with reduced penetrance were found in ATXN2 gene (1 subject, 0.1%) and TBP gene (0.82%). IAs at risk for meiotic instability were found in HTT (5.3%) and ATXN2 genes (2.7%). In ATXN1, we found a low percentage of IAs (0.4%). Alleles lacking the common CAT interruption within the CAG sequence were also rare (0.3%). CONCLUSIONS The high frequencies of IAs in HTT and ATXN2 genes suggest a correlation with the prevalence of the diseases in our population and support the hypothesis that IAs could represent a reservoir of new pathological expansions. On the opposite, ATXN1-IA were very rare in respect to the prevalence of SCA1 in our country, and TBP- IA were more frequent than expected, suggesting that other mechanisms could influence the occurrence of novel pathological expansions.
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Distribution of the CAG Triplet Repeat in ATXN1, ATXN3, and CACNA1A Loci in Peruvian Population. THE CEREBELLUM 2020; 19:527-535. [PMID: 32285347 DOI: 10.1007/s12311-020-01129-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Spinocerebellar ataxia subtypes 1, 3, and 6 (SCA1, MJD/SCA3, and SCA6) are among the most prevalent autosomal dominant cerebellar ataxias worldwide, but their relative frequencies in Peru are low. Frequency of large normal (LN) alleles at spinocerebellar ataxia-causative genes has been proposed to be associated with disease prevalence. To investigate the allelic distribution of the CAG repeat in ATXN1, ATXN3, and CACNA1A genes in a Peruvian mestizo population and examine their association with the relative frequency of SCA1, MJD/SCA3, and SCA6 across populations. We genotyped 213 healthy mestizo individuals from Northern Lima, Peru, for ATXN1, ATXN3, and CACNA1A using polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis (PAGE). We compared the frequency of LN alleles and relative disease frequency between populations. We also tested 40 samples for CAT repeat interruptions within the CAG tract of ATXN1. We found no association between disease frequency and population frequency of LN alleles at ATXN1 and ATXN3. All 40 ATXN1 samples tested for CAT interruptions were positive. Frequency of LN alleles at CACNA1A correlates with SCA6 frequency across several populations, but this effect was largely driven by data from a single population. Low frequency of SCA1 and MJD/SCA3 in Peru is not explained by frequency of LN alleles at ATXN1 and ATXN3, respectively. The observed correlation between CACNA1A LN alleles and SCA6 frequency requires further assessment.
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Chiara M, Zambelli F, Picardi E, Horner DS, Pesole G. Critical assessment of bioinformatics methods for the characterization of pathological repeat expansions with single-molecule sequencing data. Brief Bioinform 2019; 21:1971-1986. [DOI: 10.1093/bib/bbz099] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 06/22/2019] [Accepted: 07/09/2019] [Indexed: 01/19/2023] Open
Abstract
Abstract
A number of studies have reported the successful application of single-molecule sequencing technologies to the determination of the size and sequence of pathological expanded microsatellite repeats over the last 5 years. However, different custom bioinformatics pipelines were employed in each study, preventing meaningful comparisons and somewhat limiting the reproducibility of the results. In this review, we provide a brief summary of state-of-the-art methods for the characterization of expanded repeats alleles, along with a detailed comparison of bioinformatics tools for the determination of repeat length and sequence, using both real and simulated data. Our reanalysis of publicly available human genome sequencing data suggests a modest, but statistically significant, increase of the error rate of single-molecule sequencing technologies at genomic regions containing short tandem repeats. However, we observe that all the methods herein tested, irrespective of the strategy used for the analysis of the data (either based on the alignment or assembly of the reads), show high levels of sensitivity in both the detection of expanded tandem repeats and the estimation of the expansion size, suggesting that approaches based on single-molecule sequencing technologies are highly effective for the detection and quantification of tandem repeat expansions and contractions.
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Affiliation(s)
- Matteo Chiara
- Department of Biosciences, University of Milan, via Celoria 26, 20133 Milan, Italy
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, National Research Council, Via Amendola e, 70126 Bari, Italy
| | - Federico Zambelli
- Department of Biosciences, University of Milan, via Celoria 26, 20133 Milan, Italy
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, National Research Council, Via Amendola e, 70126 Bari, Italy
| | - Ernesto Picardi
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, National Research Council, Via Amendola e, 70126 Bari, Italy
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari “A. Moro”, Via Orabona 4, 70126 Bari, Italy
| | - David S Horner
- Department of Biosciences, University of Milan, via Celoria 26, 20133 Milan, Italy
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, National Research Council, Via Amendola e, 70126 Bari, Italy
| | - Graziano Pesole
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, National Research Council, Via Amendola e, 70126 Bari, Italy
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari “A. Moro”, Via Orabona 4, 70126 Bari, Italy
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Sulek A, Lusakowska A, Krysa W, Rajkiewicz M, Kaminska A, Nojszewska M, Kostera-Pruszczyk A, Zdzienicka E, Kubalska J, Rakowicz M, Szirkowiec W, Kwiecinski H, Zaremba J. WITHDRAWN: Evidence for a relatively high proportion of DM2 mutations in a large group of Polish patients. Neurol Neurochir Pol 2018:S0028-3843(18)30152-X. [PMID: 29880430 DOI: 10.1016/j.pjnns.2018.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 04/12/2018] [Indexed: 11/24/2022]
Abstract
The Publisher regrets that this article is an accidental duplication of an article that has already been published, 10.1016/j.pjnns.2018.02.008. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.
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Affiliation(s)
- Anna Sulek
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland.
| | | | - Wioletta Krysa
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Marta Rajkiewicz
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Anna Kaminska
- Department of Neurology, Medical University, Warsaw, Poland
| | | | | | - Elzbieta Zdzienicka
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Jolanta Kubalska
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Maria Rakowicz
- Department of Clinical Neurophysiology, Institute of Psychiatry and Neurology, Warsaw, Poland
| | | | | | - Jacek Zaremba
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
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11
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Sulek A, Lusakowska A, Krysa W, Rajkiewicz M, Kaminska A, Nojszewska M, Kostera-Pruszczyk A, Zdzienicka E, Kubalska J, Rakowicz M, Szirkowiec W, Kwiecinski H, Zaremba J. Evidence for a relatively high proportion of DM2 mutations in a large group of Polish patients. Neurol Neurochir Pol 2018; 52:736-742. [PMID: 29588063 DOI: 10.1016/j.pjnns.2018.02.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Revised: 02/16/2018] [Accepted: 02/26/2018] [Indexed: 11/16/2022]
Abstract
INTRODUCTION Myotonic dystrophies (DMs) type 1 (DM1) and type 2 (DM2) are autosomal dominant, multisystem disorders, considered the most common dystrophies in adults. DM1 and DM2 are caused by dynamic mutations in the DMPK and CNBP genes, respectively. METHODS Molecular analyses were performed by PCR and the modified RP-PCR in patients, in their at-risk relatives and prenatal cases. RESULTS The analysis of Polish controls revealed the range of 5-31 CTG repeats for DM1 and 110-228 bp alleles for DM2. Among 318 confirmed probands - 196 (62%) were DM1 and 122 (38%) - DM2. Within DM1families, 10 subjects carried a low expanded CTG tract (< 100 repeats), which resulted in a full mutation in subsequent generations. Two related individuals had unstable alleles-188 bp and 196 bp without common interruptions. CONCLUSION The relative frequencies of DM1/DM2 among Polish patients were 68% and 32%, respectively, with a relatively high proportion of DM2 mutations (1.6:1).
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Affiliation(s)
- Anna Sulek
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland.
| | - Anna Lusakowska
- Department of Neurology, Medical University of Warsaw, Warsaw, Poland
| | - Wioletta Krysa
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Marta Rajkiewicz
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Anna Kaminska
- Department of Neurology, Medical University of Warsaw, Warsaw, Poland
| | - Monika Nojszewska
- Department of Neurology, Medical University of Warsaw, Warsaw, Poland
| | | | - Elzbieta Zdzienicka
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Jolanta Kubalska
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Maria Rakowicz
- Department of Clinical Neurophysiology, Institute of Psychiatry and Neurology, Warsaw, Poland
| | | | - Hubert Kwiecinski
- Department of Neurology, Medical University of Warsaw, Warsaw, Poland
| | - Jacek Zaremba
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
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12
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Intrinsic Disorder in Proteins with Pathogenic Repeat Expansions. Molecules 2017; 22:molecules22122027. [PMID: 29186753 PMCID: PMC6149999 DOI: 10.3390/molecules22122027] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 11/18/2017] [Accepted: 11/21/2017] [Indexed: 11/18/2022] Open
Abstract
Intrinsically disordered proteins and proteins with intrinsically disordered regions have been shown to be highly prevalent in disease. Furthermore, disease-causing expansions of the regions containing tandem amino acid repeats often push repetitive proteins towards formation of irreversible aggregates. In fact, in disease-relevant proteins, the increased repeat length often positively correlates with the increased aggregation efficiency and the increased disease severity and penetrance, being negatively correlated with the age of disease onset. The major categories of repeat extensions involved in disease include poly-glutamine and poly-alanine homorepeats, which are often times located in the intrinsically disordered regions, as well as repeats in non-coding regions of genes typically encoding proteins with ordered structures. Repeats in such non-coding regions of genes can be expressed at the mRNA level. Although they can affect the expression levels of encoded proteins, they are not translated as parts of an affected protein and have no effect on its structure. However, in some cases, the repetitive mRNAs can be translated in a non-canonical manner, generating highly repetitive peptides of different length and amino acid composition. The repeat extension-caused aggregation of a repetitive protein may represent a pivotal step for its transformation into a proteotoxic entity that can lead to pathology. The goals of this article are to systematically analyze molecular mechanisms of the proteinopathies caused by the poly-glutamine and poly-alanine homorepeat expansion, as well as by the polypeptides generated as a result of the microsatellite expansions in non-coding gene regions and to examine the related proteins. We also present results of the analysis of the prevalence and functional roles of intrinsic disorder in proteins associated with pathological repeat expansions.
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13
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Ciesiolka A, Jazurek M, Drazkowska K, Krzyzosiak WJ. Structural Characteristics of Simple RNA Repeats Associated with Disease and their Deleterious Protein Interactions. Front Cell Neurosci 2017; 11:97. [PMID: 28442996 PMCID: PMC5387085 DOI: 10.3389/fncel.2017.00097] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 03/21/2017] [Indexed: 12/14/2022] Open
Abstract
Short Tandem Repeats (STRs) are frequent entities in many transcripts, however, in some cases, pathological events occur when a critical repeat length is reached. This phenomenon is observed in various neurological disorders, such as myotonic dystrophy type 1 (DM1), fragile X-associated tremor/ataxia syndrome, C9orf72-related amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS/FTD), and polyglutamine diseases, such as Huntington's disease (HD) and spinocerebellar ataxias (SCA). The pathological effects of these repeats are triggered by mutant RNA transcripts and/or encoded mutant proteins, which depend on the localization of the expanded repeats in non-coding or coding regions. A growing body of recent evidence revealed that the RNA structures formed by these mutant RNA repeat tracts exhibit toxic effects on cells. Therefore, in this review article, we present existing knowledge on the structural aspects of different RNA repeat tracts as revealed mainly using well-established biochemical and biophysical methods. Furthermore, in several cases, it was shown that these expanded RNA structures are potent traps for a variety of RNA-binding proteins and that the sequestration of these proteins from their normal intracellular environment causes alternative splicing aberration, inhibition of nuclear transport and export, or alteration of a microRNA biogenesis pathway. Therefore, in this review article, we also present the most studied examples of abnormal interactions that occur between mutant RNAs and their associated proteins.
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Affiliation(s)
- Adam Ciesiolka
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of SciencesPoznan, Poland
| | - Magdalena Jazurek
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of SciencesPoznan, Poland
| | - Karolina Drazkowska
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of SciencesPoznan, Poland
| | - Wlodzimierz J Krzyzosiak
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of SciencesPoznan, Poland
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14
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Kuiper EFE, de Mattos EP, Jardim LB, Kampinga HH, Bergink S. Chaperones in Polyglutamine Aggregation: Beyond the Q-Stretch. Front Neurosci 2017; 11:145. [PMID: 28386214 PMCID: PMC5362620 DOI: 10.3389/fnins.2017.00145] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 03/08/2017] [Indexed: 01/12/2023] Open
Abstract
Expanded polyglutamine (polyQ) stretches in at least nine unrelated proteins lead to inherited neuronal dysfunction and degeneration. The expansion size in all diseases correlates with age at onset (AO) of disease and with polyQ protein aggregation, indicating that the expanded polyQ stretch is the main driving force for the disease onset. Interestingly, there is marked interpatient variability in expansion thresholds for a given disease. Between different polyQ diseases the repeat length vs. AO also indicates the existence of modulatory effects on aggregation of the upstream and downstream amino acid sequences flanking the Q expansion. This can be either due to intrinsic modulation of aggregation by the flanking regions, or due to differential interaction with other proteins, such as the components of the cellular protein quality control network. Indeed, several lines of evidence suggest that molecular chaperones have impact on the handling of different polyQ proteins. Here, we review factors differentially influencing polyQ aggregation: the Q-stretch itself, modulatory flanking sequences, interaction partners, cleavage of polyQ-containing proteins, and post-translational modifications, with a special focus on the role of molecular chaperones. By discussing typical examples of how these factors influence aggregation, we provide more insight on the variability of AO between different diseases as well as within the same polyQ disorder, on the molecular level.
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Affiliation(s)
- E F E Kuiper
- Department of Cell Biology, University Medical Center Groningen, University of Groningen Groningen, Netherlands
| | - Eduardo P de Mattos
- Department of Cell Biology, University Medical Center Groningen, University of GroningenGroningen, Netherlands; Programa de Pós-Graduação em Genética e Biologia Molecular, Department of Genetics, Universidade Federal do Rio Grande do SulPorto Alegre, Brazil; Medical Genetics Service, Hospital de Clínicas de Porto AlegrePorto Alegre, Brazil
| | - Laura B Jardim
- Programa de Pós-Graduação em Genética e Biologia Molecular, Department of Genetics, Universidade Federal do Rio Grande do SulPorto Alegre, Brazil; Medical Genetics Service, Hospital de Clínicas de Porto AlegrePorto Alegre, Brazil; Departamento de Medicina Interna, Universidade Federal do Rio Grande do SulPorto Alegre, Brazil
| | - Harm H Kampinga
- Department of Cell Biology, University Medical Center Groningen, University of Groningen Groningen, Netherlands
| | - Steven Bergink
- Department of Cell Biology, University Medical Center Groningen, University of Groningen Groningen, Netherlands
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15
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Kraus-Perrotta C, Lagalwar S. Expansion, mosaicism and interruption: mechanisms of the CAG repeat mutation in spinocerebellar ataxia type 1. CEREBELLUM & ATAXIAS 2016; 3:20. [PMID: 27895927 PMCID: PMC5118900 DOI: 10.1186/s40673-016-0058-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 11/03/2016] [Indexed: 11/12/2022]
Abstract
Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder that primarily affects the cerebellum and brainstem. The genetic mutation is an expansion of CAG trinucleotide repeats within the coding region of the ataxin-1 gene, characterizing SCA1 as a polyglutamine expansion disease like Huntington’s. As with most polyglutamine expansion diseases, SCA1 follows the rules of genetic anticipation: the larger the expansion, the earlier and more rapid the symptoms. Unlike the majority of polyglutamine expansion diseases, the presence of histidine interruptions within the polyglutamine tract of ataxin-1 protein can prevent or mitigate disease. The present review aims to synthesize three decades of research on the ataxin-1 polyglutamine expansion mutation that causes SCA1. Data from genetic population studies and case studies is gathered along with data from manipulation studies in animal models. Specifically, we examine the molecular mechanisms that cause tract expansions and contractions, the molecular pathways that confer instability of tract length in gametic and somatic cells resulting in gametic and somatic mosaicism, the influence of maternal or paternal factors in inheritance of the expanded allele, and the effects of CAT/histidine interruptions to the ataxin-1 allele and protein product. Our review of existing data supports the following conclusions. First, polyCAG expansion of gametic alleles occur due to the failure of gap repair mechanisms for single or double strand breaks during the transition from an immature haploid spermatid to a mature haploid sperm cell. Equivalent failures were not detected in female gametic cells. Second, polyCAG expansion of somatic alleles occur due to hairpins formed on Okazaki fragments and slipped strand structures due to failures in mismatch repair and transcription-coupled nucleotide excision repair mechanisms. Third, CAT trinucleotide interruptions, which code for histidines in the translated protein, attenuate the formation of slipped strand structures which may protect the allele from the occurrence of large expansions. Many of the mechanisms of expansion identified in this review differ from those noted in Huntington’s disease indicating that gene -or sequence-specific factors may affect the behavior of the polyCAG/glutamine tract. Therefore, synthesis and review of research from the SCA1 field is valuable for future clinical and diagnostic work in the treatment and prevention of SCA1.
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Affiliation(s)
- Cara Kraus-Perrotta
- Department of Biology, Skidmore College, 815 North Broadway, Saratoga Springs, NY 12866 USA
| | - Sarita Lagalwar
- Neuroscience Program, Skidmore College, 815 North Broadway, Saratoga Springs, NY 12866 USA
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16
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Shimada MK, Sanbonmatsu R, Yamaguchi-Kabata Y, Yamasaki C, Suzuki Y, Chakraborty R, Gojobori T, Imanishi T. Selection pressure on human STR loci and its relevance in repeat expansion disease. Mol Genet Genomics 2016; 291:1851-69. [PMID: 27290643 DOI: 10.1007/s00438-016-1219-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Accepted: 05/21/2016] [Indexed: 12/30/2022]
Abstract
Short Tandem Repeats (STRs) comprise repeats of one to several base pairs. Because of the high mutability due to strand slippage during DNA synthesis, rapid evolutionary change in the number of repeating units directly shapes the range of repeat-number variation according to selection pressure. However, the remaining questions include: Why are STRs causing repeat expansion diseases maintained in the human population; and why are these limited to neurodegenerative diseases? By evaluating the genome-wide selection pressure on STRs using the database we constructed, we identified two different patterns of relationship in repeat-number polymorphisms between DNA and amino-acid sequences, although both patterns are evolutionary consequences of avoiding the formation of harmful long STRs. First, a mixture of degenerate codons is represented in poly-proline (poly-P) repeats. Second, long poly-glutamine (poly-Q) repeats are favored at the protein level; however, at the DNA level, STRs encoding long poly-Qs are frequently divided by synonymous SNPs. Furthermore, significant enrichments of apoptosis and neurodevelopment were biological processes found specifically in genes encoding poly-Qs with repeat polymorphism. This suggests the existence of a specific molecular function for polymorphic and/or long poly-Q stretches. Given that the poly-Qs causing expansion diseases were longer than other poly-Qs, even in healthy subjects, our results indicate that the evolutionary benefits of long and/or polymorphic poly-Q stretches outweigh the risks of long CAG repeats predisposing to pathological hyper-expansions. Molecular pathways in neurodevelopment requiring long and polymorphic poly-Q stretches may provide a clue to understanding why poly-Q expansion diseases are limited to neurodegenerative diseases.
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Affiliation(s)
- Makoto K Shimada
- Institute for Comprehensive Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan. .,National Institute of Advanced Industrial Science and Technology, 2-3-26 Aomi Koto-ku, Tokyo, 135-0064, Japan. .,Japan Biological Informatics Consortium, 10F TIME24 Building, 2-4-32 Aomi, Koto-ku, Tokyo, 135-8073, Japan.
| | - Ryoko Sanbonmatsu
- Japan Biological Informatics Consortium, 10F TIME24 Building, 2-4-32 Aomi, Koto-ku, Tokyo, 135-8073, Japan
| | - Yumi Yamaguchi-Kabata
- National Institute of Advanced Industrial Science and Technology, 2-3-26 Aomi Koto-ku, Tokyo, 135-0064, Japan.,Tohoku Medical Megabank Organization, Tohoku University, 2-1 Seiryo-machi, Aoba-ku, Sendai, 980-8573, Japan
| | - Chisato Yamasaki
- National Institute of Advanced Industrial Science and Technology, 2-3-26 Aomi Koto-ku, Tokyo, 135-0064, Japan.,Japan Biological Informatics Consortium, 10F TIME24 Building, 2-4-32 Aomi, Koto-ku, Tokyo, 135-8073, Japan
| | - Yoshiyuki Suzuki
- Graduate School of Natural Sciences, Nagoya City University, 1 Yamanohata, Mizuho-cho, Mizuho-ku, Nagoya, Aichi, 467-8501, Japan
| | - Ranajit Chakraborty
- Health Science Center, University of North Texas, 3500 Camp Bowie Blvd., Fort Worth, TX, 76107, USA
| | - Takashi Gojobori
- National Institute of Advanced Industrial Science and Technology, 2-3-26 Aomi Koto-ku, Tokyo, 135-0064, Japan.,Computational Bioscience Research Center, King Abdullah University of Science and Technology, Ibn Al-Haytham Building (West), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Tadashi Imanishi
- National Institute of Advanced Industrial Science and Technology, 2-3-26 Aomi Koto-ku, Tokyo, 135-0064, Japan.,Department of Molecular Life Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan
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17
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Zhao Y, Liu X, Sun H, Wang Y, Yang W, Ma H. Contactin‑associated protein‑like 2 expression in SH‑SY5Y cells is upregulated by a FOXP2 mutant with a shortened poly‑glutamine tract. Mol Med Rep 2015; 12:8162-8. [PMID: 26497390 DOI: 10.3892/mmr.2015.4483] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 09/14/2015] [Indexed: 11/06/2022] Open
Abstract
The forkhead box protein P2 (FOXP2) gene encodes an important transcription factor that contains a polyglutamine (poly‑Q) tract and a forkhead DNA binding domain. It has been observed that FOXP2 is associated with speech sound disorder (SSD), and mutations that decrease the length of the poly‑Q tract were identified in the FOXP2 gene of SSD patients. However, the exact role of poly‑Q reduction is not well understood. In the present study, constructs expressing wild‑type and poly‑Q reduction mutants of FOXP2 were generated by polymerase chain reaction (PCR) using lentiviral vectors and transfected into the SH‑SY5Y neuronal cell line. Quantitative reverse transcription (qRT)‑PCR and western blotting indicated that infected cells stably expressed high levels of FOXP2. Using this cell model, the impact of FOXP2 on the expression of contactin‑associated protein‑like 2 (CNTNAP2) were investigated, and CNTNAP2 mRNA expression levels were observed to be significantly higher in cells expressing poly‑Q‑reduced FOXP2. In addition, the expression level of CASPR2, a mammalian homolog of Drosophila Neurexin IV, was increased in cells expressing the FOXP2 mutant. Demonstration of regulation by FOXP2 indicates that CNTNAP2 may also be involved in SSD.
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Affiliation(s)
- Yunjing Zhao
- Department of Developmental Pediatrics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China
| | - Xiaoliang Liu
- Department of Clinical Genetics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China
| | - Hongwei Sun
- Department of Pediatrics, Central Hospital Affiliated to Shenyang Medical College, Shenyang, Liaoning 110024, P.R. China
| | - Yueping Wang
- Department of Clinical Genetics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China
| | - Wenzhu Yang
- Department of Developmental Pediatrics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China
| | - Hongwei Ma
- Department of Developmental Pediatrics, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, P.R. China
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18
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Ananda G, Hile SE, Breski A, Wang Y, Kelkar Y, Makova KD, Eckert KA. Microsatellite interruptions stabilize primate genomes and exist as population-specific single nucleotide polymorphisms within individual human genomes. PLoS Genet 2014; 10:e1004498. [PMID: 25033203 PMCID: PMC4102424 DOI: 10.1371/journal.pgen.1004498] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 05/28/2014] [Indexed: 01/01/2023] Open
Abstract
Interruptions of microsatellite sequences impact genome evolution and can alter disease manifestation. However, human polymorphism levels at interrupted microsatellites (iMSs) are not known at a genome-wide scale, and the pathways for gaining interruptions are poorly understood. Using the 1000 Genomes Phase-1 variant call set, we interrogated mono-, di-, tri-, and tetranucleotide repeats up to 10 units in length. We detected ∼26,000–40,000 iMSs within each of four human population groups (African, European, East Asian, and American). We identified population-specific iMSs within exonic regions, and discovered that known disease-associated iMSs contain alleles present at differing frequencies among the populations. By analyzing longer microsatellites in primate genomes, we demonstrate that single interruptions result in a genome-wide average two- to six-fold reduction in microsatellite mutability, as compared with perfect microsatellites. Centrally located interruptions lowered mutability dramatically, by two to three orders of magnitude. Using a biochemical approach, we tested directly whether the mutability of a specific iMS is lower because of decreased DNA polymerase strand slippage errors. Modeling the adenomatous polyposis coli tumor suppressor gene sequence, we observed that a single base substitution interruption reduced strand slippage error rates five- to 50-fold, relative to a perfect repeat, during synthesis by DNA polymerases α, β, or η. Computationally, we demonstrate that iMSs arise primarily by base substitution mutations within individual human genomes. Our biochemical survey of human DNA polymerase α, β, δ, κ, and η error rates within certain microsatellites suggests that interruptions are created most frequently by low fidelity polymerases. Our combined computational and biochemical results demonstrate that iMSs are abundant in human genomes and are sources of population-specific genetic variation that may affect genome stability. The genome-wide identification of iMSs in human populations presented here has important implications for current models describing the impact of microsatellite polymorphisms on gene expression. Microsatellites are short tandem repeat DNA sequences located throughout the human genome that display a high degree of inter-individual variation. This characteristic makes microsatellites an attractive tool for population genetics and forensics research. Some microsatellites affect gene expression, and mutations within such microsatellites can cause disease. Interruption mutations disrupt the perfect repeated array and are frequently associated with altered disease risk, but they have not been thoroughly studied in human genomes. We identified interrupted mono-, di-, tri- and tetranucleotide MSs (iMS) within individual genomes from African, European, Asian and American population groups. We show that many iMSs, including some within disease-associated genes, are unique to a single population group. By measuring the conservation of microsatellites between human and chimpanzee genomes, we demonstrate that interruptions decrease the probability of microsatellite mutations throughout the genome. We demonstrate that iMSs arise in the human genome by single base changes within the DNA, and provide biochemical data suggesting that these stabilizing changes may be created by error-prone DNA polymerases. Our genome-wide study supports the model in which iMSs act to stabilize individual genomes, and suggests that population-specific differences in microsatellite architecture may be an avenue by which genetic ancestry impacts individual disease risk.
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Affiliation(s)
- Guruprasad Ananda
- Department of Biology, Penn State University, University Park, Pennsylvania, United States of America
| | - Suzanne E. Hile
- Department of Pathology, Gittlen Cancer Research Foundation, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Amanda Breski
- Department of Pathology, Gittlen Cancer Research Foundation, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Yanli Wang
- Department of Biology, Penn State University, University Park, Pennsylvania, United States of America
| | - Yogeshwar Kelkar
- Department of Biology, Penn State University, University Park, Pennsylvania, United States of America
| | - Kateryna D. Makova
- Department of Biology, Penn State University, University Park, Pennsylvania, United States of America
- Center for Medical Genomics, Penn State University, University Park, Pennsylvania, United States of America
- * E-mail: (KDM); (KAE)
| | - Kristin A. Eckert
- Department of Pathology, Gittlen Cancer Research Foundation, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
- Center for Medical Genomics, Penn State University, University Park, Pennsylvania, United States of America
- * E-mail: (KDM); (KAE)
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19
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Fiszer A, Krzyzosiak WJ. Oligonucleotide-based strategies to combat polyglutamine diseases. Nucleic Acids Res 2014; 42:6787-810. [PMID: 24848018 PMCID: PMC4066792 DOI: 10.1093/nar/gku385] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Considerable advances have been recently made in understanding the molecular aspects of pathogenesis and in developing therapeutic approaches for polyglutamine (polyQ) diseases. Studies on pathogenic mechanisms have extended our knowledge of mutant protein toxicity, confirmed the toxicity of mutant transcript and identified other toxic RNA and protein entities. One very promising therapeutic strategy is targeting the causative gene expression with oligonucleotide (ON) based tools. This straightforward approach aimed at halting the early steps in the cascade of pathogenic events has been widely tested for Huntington's disease and spinocerebellar ataxia type 3. In this review, we gather information on the use of antisense oligonucleotides and RNA interference triggers for the experimental treatment of polyQ diseases in cellular and animal models. We present studies testing non-allele-selective and allele-selective gene silencing strategies. The latter include targeting SNP variants associated with mutations or targeting the pathologically expanded CAG repeat directly. We compare gene silencing effectors of various types in a number of aspects, including their design, efficiency in cell culture experiments and pre-clinical testing. We discuss advantages, current limitations and perspectives of various ON-based strategies used to treat polyQ diseases.
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Affiliation(s)
- Agnieszka Fiszer
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Wlodzimierz J Krzyzosiak
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
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20
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Menon RP, Nethisinghe S, Faggiano S, Vannocci T, Rezaei H, Pemble S, Sweeney MG, Wood NW, Davis MB, Pastore A, Giunti P. The role of interruptions in polyQ in the pathology of SCA1. PLoS Genet 2013; 9:e1003648. [PMID: 23935513 PMCID: PMC3723530 DOI: 10.1371/journal.pgen.1003648] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 06/04/2013] [Indexed: 11/18/2022] Open
Abstract
At least nine dominant neurodegenerative diseases are caused by expansion of CAG repeats in coding regions of specific genes that result in abnormal elongation of polyglutamine (polyQ) tracts in the corresponding gene products. When above a threshold that is specific for each disease the expanded polyQ repeats promote protein aggregation, misfolding and neuronal cell death. The length of the polyQ tract inversely correlates with the age at disease onset. It has been observed that interruption of the CAG tract by silent (CAA) or missense (CAT) mutations may strongly modulate the effect of the expansion and delay the onset age. We have carried out an extensive study in which we have complemented DNA sequence determination with cellular and biophysical models. By sequencing cloned normal and expanded SCA1 alleles taken from our cohort of ataxia patients we have determined sequence variations not detected by allele sizing and observed for the first time that repeat instability can occur even in the presence of CAG interruptions. We show that histidine interrupted pathogenic alleles occur with relatively high frequency (11%) and that the age at onset inversely correlates linearly with the longer uninterrupted CAG stretch. This could be reproduced in a cellular model to support the hypothesis of a linear behaviour of polyQ. We clarified by in vitro studies the mechanism by which polyQ interruption slows down aggregation. Our study contributes to the understanding of the role of polyQ interruption in the SCA1 phenotype with regards to age at disease onset, prognosis and transmission. Spinocerebellar ataxia type 1 (SCA1) is a progressive neurodegenerative disorder resulting in loss of coordination and balance. It is caused by an expanded repeated DNA sequence (CAG) in the gene ATXN1. The CAG repeat region is normally interrupted by the DNA sequence CAT. Loss of this interruption is believed to cause instability whereby the CAG repeat expands beyond a key threshold resulting, ultimately, in polyglutamine protein aggregation and cell death. Here we examine how interruptions influence pathology in patients and establish a cellular model to support our findings. We distinguish our patients into two sub-groups based on whether or not their expanded CAG repeat stretches contained an interruption. This is not possible with conventional diagnostic techniques. Differentiating the sub-group with no interruptions led to improved accuracy in predicting their age at onset. The other sub-group, with interruptions, reveals a delay in age at onset that shows greater alignment with the longest stretch of CAG repeats. These findings are significant for genetic counselling and prognosis. Our cellular model and in vitro studies confirmed the relationship between disease severity and uninterrupted repeat length and showed that interruptions do not significantly affect the polyglutamine protein aggregation, but do slow down the aggregation rate.
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Affiliation(s)
| | - Suran Nethisinghe
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, United Kingdom
| | | | | | - Human Rezaei
- Department of Protein Macroassemblies and Prion Pathology, INRA, Domain de Vilvert, Jouy en Josas, France
| | - Sally Pemble
- Neurogenetics Unit, National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Mary G. Sweeney
- Neurogenetics Unit, National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Nicholas W. Wood
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, United Kingdom
| | - Mary B. Davis
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, United Kingdom
| | | | - Paola Giunti
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, United Kingdom
- * E-mail: (AP); (PG)
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Laffita-Mesa J, Almaguer-Mederos L, Kourí V, Bauer P, Vázquez-Mojena Y, Cruz Mariño T, Velázquez-Pérez L. Large normal alleles and SCA2 prevalence: lessons from a nationwide study and analysis of the literature. Clin Genet 2013; 86:96-8. [DOI: 10.1111/cge.12221] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 06/19/2013] [Accepted: 06/19/2013] [Indexed: 11/29/2022]
Affiliation(s)
- J.M. Laffita-Mesa
- Center for Research and Rehabilitation of Hereditary Ataxias - CIRAH; Holguín Cuba
- Branch of Biomedicine of the Cuban Academy of Sciences - ACC; Havana Cuba
| | - L.E. Almaguer-Mederos
- Center for Research and Rehabilitation of Hereditary Ataxias - CIRAH; Holguín Cuba
- Branch of Biomedicine of the Cuban Academy of Sciences - ACC; Havana Cuba
| | - V. Kourí
- Virology Department; Institute of Tropical Medicine “Pedro Kourí”; Havana Cuba
| | - P.O. Bauer
- Department of Neuroscience; Mayo Clinic; Jacksonville FL USA
| | - Y. Vázquez-Mojena
- Center for Research and Rehabilitation of Hereditary Ataxias - CIRAH; Holguín Cuba
| | - T. Cruz Mariño
- Center for Research and Rehabilitation of Hereditary Ataxias - CIRAH; Holguín Cuba
| | - L. Velázquez-Pérez
- Center for Research and Rehabilitation of Hereditary Ataxias - CIRAH; Holguín Cuba
- Branch of Biomedicine of the Cuban Academy of Sciences - ACC; Havana Cuba
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Cruz-Mariño T, Laffita-Mesa JM, Gonzalez-Zaldivar Y, Velazquez-Santos M, Aguilera-Rodriguez R, Estupinan-Rodriguez A, Vazquez-Mojena Y, Macleod P, Paneque M, Velazquez-Perez L. Large normal and intermediate alleles in the context of SCA2 prenatal diagnosis. J Genet Couns 2013; 23:89-96. [PMID: 23813298 DOI: 10.1007/s10897-013-9615-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Accepted: 05/22/2013] [Indexed: 12/22/2022]
Abstract
In 2001 a program for predictive testing of Spinocerebellar Ataxia type 2 was developed in Cuba, based on the detection of an abnormal CAG trinucleotide repeat expansion in the ATXN2 gene. A descriptive study was designed to assess the implications of ATXN2 large normal and intermediate alleles in the context of the SCA2 Prenatal Diagnosis Program. Four clinical scenarios were selected based upon the behaviour of large normal and intermediate alleles when passing from one generation to the next, showing expansions, contractions, or stability in the CAG repeat size. In some populations, traditional Mendelian risk figures of 0 % or 50 % may not be applicable due to the high frequency of unstable large normal alleles. Couples with no family history of SCA2 may have a >0 % risk of having an affected offspring. Similarly, couples in which there is both an expanded and a large normal allele may have a recurrence risk >50 %. It is imperative that these issues be addressed with these couples during genetic counseling. These recurrence risks have to be carefully estimated in the presence of such alleles (particularly alleles ≥27 CAG repeats), carriers need to be aware of the potential risk for their descendants, and programs for prenatal diagnosis must be available for them.
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Affiliation(s)
- Tania Cruz-Mariño
- Predictive Genetics Department, Center for the Research and Rehabilitation of Hereditary Ataxias, Reparto Edecio Pérez, Carretera Vía Habana, Holguín, Cuba, 80100,
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Fiszer A, Krzyzosiak WJ. RNA toxicity in polyglutamine disorders: concepts, models, and progress of research. J Mol Med (Berl) 2013; 91:683-91. [PMID: 23512265 PMCID: PMC3659269 DOI: 10.1007/s00109-013-1016-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 02/19/2013] [Accepted: 02/25/2013] [Indexed: 01/13/2023]
Abstract
In Huntington's disease and other polyglutamine (polyQ) disorders, mutant proteins containing a long polyQ stretch are well documented as the trigger of numerous aberrant cellular processes that primarily lead to degeneration and, ultimately, the death of neuronal cells. However, mutant transcripts containing expanded CAG repeats may also be toxic and contribute to cellular dysfunction. The exact nature and importance of RNA toxicity in polyQ diseases are only beginning to be recognized, and the first insights have mainly resulted from studies using simple model systems. In this review, we briefly present the basic mechanisms of protein toxicity in polyQ disorders and RNA toxicity in myotonic dystrophy type 1 and discuss recent results suggesting that the pathogenesis of polyQ diseases may also be mediated by mutant transcripts. This review is focused on the experimental systems used thus far to demonstrate RNA toxicity in polyQ disorders and the design of new systems that will be more relevant to the human disease situation and capable of separating RNA toxicity from protein toxicity.
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Affiliation(s)
- Agnieszka Fiszer
- Laboratory of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Wlodzimierz J. Krzyzosiak
- Laboratory of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
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24
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Martindale JE, Seneca S, Wieczorek S, Sequeiros J. Spinocerebellar ataxias: an example of the challenges associated with genetic databases for dynamic mutations. Hum Mutat 2012; 33:1359-65. [PMID: 22753119 DOI: 10.1002/humu.22156] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 06/21/2012] [Indexed: 11/08/2022]
Abstract
Locus-specific databases are an important source of information for diagnostic laboratories and a valued means of improving quality of genetic testing. Although increasingly frequent, databases for oligonucleotide repeat expansions are still scarce, due to factors that make them different and the building of databases much more difficult. Definition of what constitutes "the repeat" to measure is not a simple matter and correct sizing is not always straightforward. Reference ranges and penetrance classes are not easy to establish. Acceptable margins of error depend on the disease and allele-size distribution, and vary according to size range and pathogenic significance. Inter- and intralaboratorial variance is well documented and allele distribution may vary among populations. The spinocerebellar ataxias, used only as an example of those difficulties, are also a highly heterogeneous group, which includes loci with both pathogenic repeat expansions and point mutations or insertions/deletions. They display a variable, but often overlapping phenotype, where genotype-phenotype correlation is difficult or nonexistent. Standard (Human Genome Variation Society) nomenclature is not appropriate for oligonucleotide repeats, as established at harmonization among all EMQN (European Molecular Genetics Network) external quality assessment (EQA) schemes for "repeat disorders." Curation of such databases is a difficult task, but one that needs to be addressed adequately and without much delay.
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Affiliation(s)
- Joanne E Martindale
- European Molecular Genetics Network (EMQN), spinocerebellar ataxias (SCAs) External Quality Assessment (EQA) Scheme organizer (JS) and assessors, Manchester, UK
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25
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Ryan CP, Crespi BJ. Androgen receptor polyglutamine repeat number: models of selection and disease susceptibility. Evol Appl 2012; 6:180-96. [PMID: 23467468 PMCID: PMC3586616 DOI: 10.1111/j.1752-4571.2012.00275.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 05/04/2012] [Indexed: 12/14/2022] Open
Abstract
Variation in polyglutamine repeat number in the androgen receptor (AR CAGn) is negatively correlated with the transcription of androgen-responsive genes and is associated with susceptibility to an extensive list of human disease. Only a small portion of the heritability for many of these diseases is explained by conventional SNP-based genome-wide association studies, and the forces shaping AR CAGn among humans remains largely unexplored. Here, we propose evolutionary models for understanding selection at the AR CAG locus, namely balancing selection, sexual conflict, accumulation-selection, and antagonistic pleiotropy. We evaluate these models by examining AR CAGn-linked susceptibility to eight extensively studied diseases representing the diverse physiological roles of androgens, and consider the costs of these diseases by their frequency and fitness effects. Five diseases could contribute to the distribution of AR CAGn observed among contemporary human populations. With support for disease susceptibilities associated with long and short AR CAGn, balancing selection provides a useful model for studying selection at this locus. Gender-specific differences AR CAGn health effects also support this locus as a candidate for sexual conflict over repeat number. Accompanied by the accumulation of AR CAGn in humans, these models help explain the distribution of repeat number in contemporary human populations.
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Affiliation(s)
- Calen P Ryan
- Department of Biological Sciences, Simon Fraser University Burnaby, BC, Canada
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26
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Ramazzotti M, Monsellier E, Kamoun C, Degl'Innocenti D, Melki R. Polyglutamine repeats are associated to specific sequence biases that are conserved among eukaryotes. PLoS One 2012; 7:e30824. [PMID: 22312432 PMCID: PMC3270027 DOI: 10.1371/journal.pone.0030824] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 12/23/2011] [Indexed: 12/20/2022] Open
Abstract
Nine human neurodegenerative diseases, including Huntington's disease and several spinocerebellar ataxia, are associated to the aggregation of proteins comprising an extended tract of consecutive glutamine residues (polyQs) once it exceeds a certain length threshold. This event is believed to be the consequence of the expansion of polyCAG codons during the replication process. This is in apparent contradiction with the fact that many polyQs-containing proteins remain soluble and are encoded by invariant genes in a number of eukaryotes. The latter suggests that polyQs expansion and/or aggregation might be counter-selected through a genetic and/or protein context. To identify this context, we designed a software that scrutinize entire proteomes in search for imperfect polyQs. The nature of residues flanking the polyQs and that of residues other than Gln within polyQs (insertions) were assessed. We discovered strong amino acid residue biases robustly associated to polyQs in the 15 eukaryotic proteomes we examined, with an over-representation of Pro, Leu and His and an under-representation of Asp, Cys and Gly amino acid residues. These biases are conserved amongst unrelated proteins and are independent of specific functional classes. Our findings suggest that specific residues have been co-selected with polyQs during evolution. We discuss the possible selective pressures responsible of the observed biases.
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Affiliation(s)
- Matteo Ramazzotti
- Dipartimento di Scienze Biochimiche, Università degli Studi di Firenze, Florence, Italy
- * E-mail: (MR); (EM)
| | - Elodie Monsellier
- Laboratoire d'Enzymologie et de Biochimie Structurales, UPR 3082 CNRS, Gif sur Yvette, France
- * E-mail: (MR); (EM)
| | - Choumouss Kamoun
- Laboratoire d'Enzymologie et de Biochimie Structurales, UPR 3082 CNRS, Gif sur Yvette, France
| | | | - Ronald Melki
- Laboratoire d'Enzymologie et de Biochimie Structurales, UPR 3082 CNRS, Gif sur Yvette, France
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27
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Affiliation(s)
- Georg W J Auburger
- Section Molecular Neurogenetics, Department of Neurology, Johann Wolfgang Goeche University Medical School, Frankfurt/Main, Germany.
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28
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Kelkar YD, Eckert KA, Chiaromonte F, Makova KD. A matter of life or death: how microsatellites emerge in and vanish from the human genome. Genome Res 2011; 21:2038-48. [PMID: 21994250 DOI: 10.1101/gr.122937.111] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Microsatellites--tandem repeats of short DNA motifs--are abundant in the human genome and have high mutation rates. While microsatellite instability is implicated in numerous genetic diseases, the molecular processes involved in their emergence and disappearance are still not well understood. Microsatellites are hypothesized to follow a life cycle, wherein they are born and expand into adulthood, until their degradation and death. Here we identified microsatellite births/deaths in human, chimpanzee, and orangutan genomes, using macaque and marmoset as outgroups. We inferred mutations causing births/deaths based on parsimony, and investigated local genomic environments affecting them. We also studied birth/death patterns within transposable elements (Alus and L1s), coding regions, and disease-associated loci. We observed that substitutions were the predominant cause for births of short microsatellites, while insertions and deletions were important for births of longer microsatellites. Substitutions were the cause for deaths of microsatellites of virtually all lengths. AT-rich L1 sequences exhibited elevated frequency of births/deaths over their entire length, while GC-rich Alus only in their 3' poly(A) tails and middle A-stretches, with differences depending on transposable element integration timing. Births/deaths were strongly selected against in coding regions. Births/deaths occurred in genomic regions with high substitution rates, protomicrosatellite content, and L1 density, but low GC content and Alu density. The majority of the 17 disease-associated microsatellites examined are evolutionarily ancient (were acquired by the common ancestor of simians). Our genome-wide investigation of microsatellite life cycle has fundamental applications for predicting the susceptibility of birth/death of microsatellites, including many disease-causing loci.
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Affiliation(s)
- Yogeshwar D Kelkar
- Department of Biology, Penn State University, University Park, Pennsylvania 16802, USA
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Laffita-Mesa JM, Velázquez-Pérez LC, Santos Falcón N, Cruz-Mariño T, González Zaldívar Y, Vázquez Mojena Y, Almaguer-Gotay D, Almaguer Mederos LE, Rodríguez Labrada R. Unexpanded and intermediate CAG polymorphisms at the SCA2 locus (ATXN2) in the Cuban population: evidence about the origin of expanded SCA2 alleles. Eur J Hum Genet 2011; 20:41-9. [PMID: 21934711 DOI: 10.1038/ejhg.2011.154] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The role of short, large or intermediate normal alleles (ANs) of the ataxin-2 gene in generating expanded alleles (EAs) causing spinocerebellar ataxia type 2 (SCA2) is poorly understood. It has been postulated that SCA2 prevalence is related to the frequency of large ANs. SCA2 shows the highest worldwide prevalence in Cuban population, which is therefore a unique source for studying the relationship between the frequency of large and intermediate alleles and the frequency of SCA2 mutation. Through genetic polymorphism analyses in a comprehensive sample (~3000 chromosomes), we show that the frequency of large ANs in the ataxin-2 gene is the highest worldwide, although short ANs are also frequent. This highly polymorphic population displayed also high variability in the CAG sequence, featured by loss of the anchor CAA interruption(s). In addition, large ANs showed germinal and somatic instability. Our study also includes related genotypic, genealogical and haplotypic data and provides substantial evidence with regard to the role of large and intermediate alleles in the generation of pathological EAs.
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Affiliation(s)
- José Miguel Laffita-Mesa
- Laboratory of Molecular Neurobiology, Centre for the Research and Rehabilitation of Hereditary Ataxias, Holguín, Cuba. mails:
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Krzyzosiak WJ, Sobczak K, Wojciechowska M, Fiszer A, Mykowska A, Kozlowski P. Triplet repeat RNA structure and its role as pathogenic agent and therapeutic target. Nucleic Acids Res 2011; 40:11-26. [PMID: 21908410 PMCID: PMC3245940 DOI: 10.1093/nar/gkr729] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This review presents detailed information about the structure of triplet repeat RNA and addresses the simple sequence repeats of normal and expanded lengths in the context of the physiological and pathogenic roles played in human cells. First, we discuss the occurrence and frequency of various trinucleotide repeats in transcripts and classify them according to the propensity to form RNA structures of different architectures and stabilities. We show that repeats capable of forming hairpin structures are overrepresented in exons, which implies that they may have important functions. We further describe long triplet repeat RNA as a pathogenic agent by presenting human neurological diseases caused by triplet repeat expansions in which mutant RNA gains a toxic function. Prominent examples of these diseases include myotonic dystrophy type 1 and fragile X-associated tremor ataxia syndrome, which are triggered by mutant CUG and CGG repeats, respectively. In addition, we discuss RNA-mediated pathogenesis in polyglutamine disorders such as Huntington's disease and spinocerebellar ataxia type 3, in which expanded CAG repeats may act as an auxiliary toxic agent. Finally, triplet repeat RNA is presented as a therapeutic target. We describe various concepts and approaches aimed at the selective inhibition of mutant transcript activity in experimental therapies developed for repeat-associated diseases.
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Affiliation(s)
- Wlodzimierz J Krzyzosiak
- Laboratory of Cancer Genetics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
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31
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Ross OA, Rutherford NJ, Baker M, Soto-Ortolaza AI, Carrasquillo MM, DeJesus-Hernandez M, Adamson J, Li M, Volkening K, Finger E, Seeley WW, Hatanpaa KJ, Lomen-Hoerth C, Kertesz A, Bigio EH, Lippa C, Woodruff BK, Knopman DS, White CL, Van Gerpen JA, Meschia JF, Mackenzie IR, Boylan K, Boeve BF, Miller BL, Strong MJ, Uitti RJ, Younkin SG, Graff-Radford NR, Petersen RC, Wszolek ZK, Dickson DW, Rademakers R. Ataxin-2 repeat-length variation and neurodegeneration. Hum Mol Genet 2011; 20:3207-12. [PMID: 21610160 DOI: 10.1093/hmg/ddr227] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Expanded glutamine repeats of the ataxin-2 (ATXN2) protein cause spinocerebellar ataxia type 2 (SCA2), a rare neurodegenerative disorder. More recent studies have suggested that expanded ATXN2 repeats are a genetic risk factor for amyotrophic lateral sclerosis (ALS) via an RNA-dependent interaction with TDP-43. Given the phenotypic diversity observed in SCA2 patients, we set out to determine the polymorphic nature of the ATXN2 repeat length across a spectrum of neurodegenerative disorders. In this study, we genotyped the ATXN2 repeat in 3919 neurodegenerative disease patients and 4877 healthy controls and performed logistic regression analysis to determine the association of repeat length with the risk of disease. We confirmed the presence of a significantly higher number of expanded ATXN2 repeat carriers in ALS patients compared with healthy controls (OR = 5.57; P= 0.001; repeat length >30 units). Furthermore, we observed significant association of expanded ATXN2 repeats with the development of progressive supranuclear palsy (OR = 5.83; P= 0.004; repeat length >30 units). Although expanded repeat carriers were also identified in frontotemporal lobar degeneration, Alzheimer's and Parkinson's disease patients, these were not significantly more frequent than in controls. Of note, our study identified a number of healthy control individuals who harbor expanded repeat alleles (31-33 units), which suggests caution should be taken when attributing specific disease phenotypes to these repeat lengths. In conclusion, our findings confirm the role of ATXN2 as an important risk factor for ALS and support the hypothesis that expanded ATXN2 repeats may predispose to other neurodegenerative diseases, including progressive supranuclear palsy.
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Affiliation(s)
- Owen A Ross
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
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Chen XC, Sun H, Mi DQ, Huang XQ, Lin KQ, Yi W, Yu L, Shi L, Shi L, Yang ZQ, Chu JY. [Variation of CAG repeats in coding region of ATXN2 gene in different ethnic groups]. YI CHUAN = HEREDITAS 2011; 33:353-357. [PMID: 21482525 DOI: 10.3724/sp.j.1005.2011.00353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Toinvestigate CAG repeats variation of ATXN2 gene coding region in six ethnic groups that live in comparatively different environments, to evaluate whether these variations are under positive selection, and to find factors driving selection effects, 291 unrelated healthy individuals were collected from six ethnic groups and their STR geneotyping was performed. The frequencies of alleles and genotypes were counted and thereby Slatkin's linearized Fst values were calculated. The UPGMA tree against this gene was constructed. The MDS analysis among these groups was carried out as well. The results from the linearized Fst values indicated that there were significant evolutionary differences of the STR in ATXN2 gene between Hui and Yi groups, but not among the other 4 groups. Further analysis was performed by combining our data with published data obtained from other groups. These results indicated that there were significant differences between Japanese and other groups including Hui, Hani, Yunnan Mongolian, and Inner Mongolian. Both Hui and Mongolian from Inner Mongolia were significantly different from Han. In conclusion, the six ethnic groups had their own distribution characterizations of allelic frequencies of ATXN2 STR, and the potential cause of frequency changes in rare alleles could be the consequence of positive selection.
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Affiliation(s)
- Xiao-Chen Chen
- Department of Medical Genetics, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Kunming 650118, China.
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de Mezer M, Wojciechowska M, Napierala M, Sobczak K, Krzyzosiak WJ. Mutant CAG repeats of Huntingtin transcript fold into hairpins, form nuclear foci and are targets for RNA interference. Nucleic Acids Res 2011; 39:3852-63. [PMID: 21247881 PMCID: PMC3089464 DOI: 10.1093/nar/gkq1323] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The CAG repeat expansions that occur in translated regions of specific genes can cause human genetic disorders known as polyglutamine (poly-Q)-triggered diseases. Huntington's disease and spinobulbar muscular atrophy (SBMA) are examples of these diseases in which underlying mutations are localized near other trinucleotide repeats in the huntingtin (HTT) and androgen receptor (AR) genes, respectively. Mutant proteins that contain expanded polyglutamine tracts are well-known triggers of pathogenesis in poly-Q diseases, but a toxic role for mutant transcripts has also been proposed. To gain insight into the structural features of complex triplet repeats of HTT and AR transcripts, we determined their structures in vitro and showed the contribution of neighboring repeats to CAG repeat hairpin formation. We also demonstrated that the expanded transcript is retained in the nucleus of human HD fibroblasts and is colocalized with the MBNL1 protein. This suggests that the CAG repeats in the HTT mRNA adopt ds-like RNA conformations in vivo. The intracellular structure of the CAG repeat region of mutant HTT transcripts was not sufficiently stable to be protected from cleavage by an siRNA targeting the repeats and the silencing efficiency was higher for the mutant transcript than for its normal counterpart.
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Affiliation(s)
- Mateusz de Mezer
- Laboratory of Cancer Genetics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
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Whan V, Hobbs M, McWilliam S, Lynn DJ, Lutzow YS, Khatkar M, Barendse W, Raadsma H, Tellam RL. Bovine proteins containing poly-glutamine repeats are often polymorphic and enriched for components of transcriptional regulatory complexes. BMC Genomics 2010; 11:654. [PMID: 21092319 PMCID: PMC3014979 DOI: 10.1186/1471-2164-11-654] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 11/23/2010] [Indexed: 11/12/2022] Open
Abstract
Background About forty human diseases are caused by repeat instability mutations. A distinct subset of these diseases is the result of extreme expansions of polymorphic trinucleotide repeats; typically CAG repeats encoding poly-glutamine (poly-Q) tracts in proteins. Polymorphic repeat length variation is also apparent in human poly-Q encoding genes from normal individuals. As these coding sequence repeats are subject to selection in mammals, it has been suggested that normal variations in some of these typically highly conserved genes are implicated in morphological differences between species and phenotypic variations within species. At present, poly-Q encoding genes in non-human mammalian species are poorly documented, as are their functions and propensities for polymorphic variation. Results The current investigation identified 178 bovine poly-Q encoding genes (Q ≥ 5) and within this group, 26 genes with orthologs in both human and mouse that did not contain poly-Q repeats. The bovine poly-Q encoding genes typically had ubiquitous expression patterns although there was bias towards expression in epithelia, brain and testes. They were also characterised by unusually large sizes. Analysis of gene ontology terms revealed that the encoded proteins were strongly enriched for functions associated with transcriptional regulation and many contributed to physical interaction networks in the nucleus where they presumably act cooperatively in transcriptional regulatory complexes. In addition, the coding sequence CAG repeats in some bovine genes impacted mRNA splicing thereby generating unusual transcriptional diversity, which in at least one instance was tissue-specific. The poly-Q encoding genes were prioritised using multiple criteria for their likelihood of being polymorphic and then the highest ranking group was experimentally tested for polymorphic variation within a cattle diversity panel. Extensive and meiotically stable variation was identified. Conclusions Transcriptional diversity can potentially be generated in poly-Q encoding genes by the impact of CAG repeat tracts on mRNA alternative splicing. This effect, combined with the physical interactions of the encoded proteins in large transcriptional regulatory complexes suggests that polymorphic variations of proteins in these complexes have strong potential to affect phenotype.
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Affiliation(s)
- Vicki Whan
- CSIRO Livestock Industries, Queensland Bioscience Precinct, 306 Carmody Rd, St Lucia, Queensland 4067, Australia
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Sequeiros J, Seneca S, Martindale J. Consensus and controversies in best practices for molecular genetic testing of spinocerebellar ataxias. Eur J Hum Genet 2010; 18:1188-95. [PMID: 20179748 PMCID: PMC2987480 DOI: 10.1038/ejhg.2010.10] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 12/14/2009] [Accepted: 01/05/2010] [Indexed: 11/09/2022] Open
Abstract
Many laboratories worldwide are offering molecular genetic testing for spinocerebellar ataxias (SCAs). This is essential for differential diagnosis and adequate genetic counselling. The European Molecular Genetics Quality Network (EMQN) started an SCA external quality assessment scheme in 2004. There was a clear need for updated laboratory guidelines. EMQN and EuroGentest organized a Best Practice (BP) meeting to discuss current practices and achieve consensus. A pre-meeting survey showed that 36 laboratories (20 countries) conducted nearly 18 000 SCA tests the year before, and identified issues to discuss. Draft guidelines were produced immediately after the meeting and discussed online for several months. The final version was endorsed by EMQN, and harmonized with guidelines from other oligonucleotide repeat disorders. We present the procedures taken to organize the survey, BP meeting, as well as drafting and approval of BP guidelines. We emphasize the most important recommendations on (1) pre-test requirements, (2) appropriate methodologies and (3) interpretation and reporting, and focus on the discussion of controversial issues not included in the final document. In addition, after an extensive review of scientific literature, and responding to recommendations made, we now produce information that we hope will facilitate the activities of diagnostic laboratories and foster quality SCA testing. For the main loci, this includes (1) a list of repeat sequences, as originally published; (2) primers in use; and (3) an evidence-based description of the normal and pathogenic repeat-size ranges, including those of reduced penetrance and those in which there is still some uncertainty. This information will be maintained and updated in http://www.scabase.eu.
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Affiliation(s)
- Jorge Sequeiros
- Institute for Molecular and Cell Biology and ICBAS, University Porto, Rua Campo Alegre 823, Porto, Portugal.
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36
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Dickson AM, Wilusz CJ. Repeat expansion diseases: when a good RNA turns bad. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 1:173-92. [PMID: 21956913 DOI: 10.1002/wrna.18] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
An increasing number of dominantly inherited diseases have now been linked with expansion of short repeats within specific genes. Although some of these expansions affect protein function or result in haploinsufficiency, a significant portion cause pathogenesis through production of toxic RNA molecules that alter cellular metabolism. In this review, we examine the criteria that influence toxicity of these mutant RNAs and discuss new developments in therapeutic approaches.
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Affiliation(s)
- Alexa M Dickson
- Department of Microbiology, Immunology & Pathology, Colorado State University, Fort Collins, CO 80523, USA
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Koneva LA, Konev AV, Kucher AN. Simulation of the distribution of spinocerebellar ataxia type 1 in Yakut populations: Description of the model. RUSS J GENET+ 2010. [DOI: 10.1134/s1022795410030154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Warby SC, Visscher H, Butland S, Pearson CE, Hayden MR. Response to Falush: a role for cis-element polymorphisms in HD. Am J Hum Genet 2009; 85:942-5. [PMID: 20004773 DOI: 10.1016/j.ajhg.2009.11.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 11/02/2009] [Accepted: 11/02/2009] [Indexed: 01/21/2023] Open
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Fondon JW, Hammock EAD, Hannan AJ, King DG. Simple sequence repeats: genetic modulators of brain function and behavior. Trends Neurosci 2008; 31:328-34. [PMID: 18550185 DOI: 10.1016/j.tins.2008.03.006] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 03/17/2008] [Accepted: 03/18/2008] [Indexed: 02/03/2023]
Affiliation(s)
- John W Fondon
- McDermott Center for Human Growth and Development and Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Microsatellite evolution: Mutations, sequence variation, and homoplasy in the hypervariable avian microsatellite locus HrU10. BMC Evol Biol 2008; 8:138. [PMID: 18471288 PMCID: PMC2396632 DOI: 10.1186/1471-2148-8-138] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Accepted: 05/09/2008] [Indexed: 02/01/2023] Open
Abstract
Background Microsatellites are frequently used genetic markers in a wide range of applications, primarily due to their high length polymorphism levels that can easily be genotyped by fragment length analysis. However, the mode of microsatellite evolution is yet not fully understood, and the role of interrupting motifs for the stability of microsatellites remains to be explored in more detail. Here we present a sequence analysis of mutation events and a description of the structure of repeated regions in the hypervariable, pentanucleotide microsatellite locus HrU10 in barn swallows (Hirundo rustica) and tree swallows (Tachycineta bicolor). Results In a large-scale parentage analysis in barn swallows and tree swallows, broods were screened for mutations at the HrU10 locus. In 41 cases in the barn swallows and 15 cases in the tree swallows, mutations corresponding to the loss or gain of one or two repeat units were detected. The parent and mutant offspring alleles were sequenced for 33 of these instances (26 in barn swallows and 7 in tree swallows). Replication slippage was considered the most likely mutational process. We tested the hypothesis that HrU10, a microsatellite with a wide allele size range, has an increased probability of introductions of interruptive motifs (IMs) with increasing length of the repeated region. Indeed, the number and length of the IMs was strongly positively correlated with the total length of the microsatellite. However, there was no significant correlation with the length of the longest stretch of perfectly repeated units, indicating a threshold level for the maximum length of perfectly repeated pentanucleotide motifs in stable HrU10 alleles. The combination of sequence and pedigree data revealed that 15 barn swallow mutations (58%) produced alleles that were size homoplasic to other alleles in the data set. Conclusion Our results give further insights into the mode of microsatellite evolution, and support the assumption of increased slippage rate with increased microsatellite length and a stabilizing effect of interrupting motifs for microsatellite regions consisting of perfect repeats. In addition, the observed extent of size homoplasy may impose a general caution against using hypervariable microsatellites in genetic diversity measures when alleles are identified by fragment length analysis only.
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Lin JX, Ishikawa K, Sakamoto M, Tsunemi T, Ishiguro T, Amino T, Toru S, Kondo I, Mizusawa H. Direct and accurate measurement of CAG repeat configuration in the ataxin-1 (ATXN-1) gene by "dual-fluorescence labeled PCR-restriction fragment length analysis". J Hum Genet 2008; 53:287-295. [PMID: 18301861 DOI: 10.1007/s10038-007-0242-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Accepted: 12/15/2007] [Indexed: 10/22/2022]
Abstract
Spinocerebellar ataxia type 1 (SCA1; OMIM: #164400) is an autosomal dominant cerebellar ataxia caused by an expansion of CAG repeat, which encodes polyglutamine, in the ataxin-1 (ATXN1) gene. Length of polyglutamine in the ATXN1 protein is the critical determinant of pathogenesis of this disease. Molecular diagnosis of SCA1 is usually undertaken by assessing the length of CAG repeat configuration using primers spanning this configuration. However, this conventional method may potentially lead to misdiagnosis in assessing polyglutamine-encoding CAG repeat length, since CAT interruptions may be present within the CAG repeat configuration, not only in normal controls but also in neurologically symptomatic subjects. We developed a new method for assessing actual CAG repeat numbers not interrupted by CAT sequences. Polymerase chain reaction using a primer pair labeled with two different fluorescences followed by restriction enzyme digestion with SfaNI which recognizes the sequence "GCATC(N)(5)", lengths of actual CAG repeats that encode polyglutamine were directly detected. We named this method "dual fluorescence labeled PCR-restriction fragment length analysis". We found that numbers of actual CAG repeat encoding polyglutamine do not overlap between our cohorts of normal chromosomes (n=385) and SCA1 chromosomes (n=5). We conclude that the present method is a useful way for molecular diagnosis of SCA1.
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Affiliation(s)
- Jiang X Lin
- Department of Neurology and Neurological Science, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
| | - Kinya Ishikawa
- Department of Neurology and Neurological Science, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan.
| | - Masaki Sakamoto
- Department of Neurology and Neurological Science, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
| | - Taiji Tsunemi
- Department of Neurology and Neurological Science, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
| | - Taro Ishiguro
- Department of Neurology and Neurological Science, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
| | - Takeshi Amino
- Department of Neurology and Neurological Science, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
| | - Shuta Toru
- Department of Neurology and Neurological Science, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
| | - Ikuko Kondo
- Department of Medical Genetics, Ehime University, Onsen-gun, Ehime, Japan.,Ibaraki Prefectural Child Welfare Health Center, Yoshizawa-cho 3979-3, Mito, Ibaraki, 310-0845, Japan
| | - Hidehiro Mizusawa
- Department of Neurology and Neurological Science, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
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Boyer JC, Hawk JD, Stefanovic L, Farber RA. Sequence-dependent effect of interruptions on microsatellite mutation rate in mismatch repair-deficient human cells. Mutat Res 2007; 640:89-96. [PMID: 18242644 DOI: 10.1016/j.mrfmmm.2007.12.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 11/21/2007] [Accepted: 12/11/2007] [Indexed: 11/18/2022]
Abstract
Although microsatellite mutation rates generally increase with increasing length of the repeat tract, interruptions in a microsatellite may stabilize it. We have performed a direct analysis of the effect of microsatellite interruptions on mutation rate and spectrum in cultured mammalian cells. Two mononucleotide sequences (G(17) and A(17)) and a dinucleotide [(CA)(17)] were compared with interrupted repeats of the same size and with sequences of 8 repeat units. MMR-deficient (MMR(-)) cells were used for these studies to eliminate effects of this repair process. Mutation rates were determined by fluctuation analysis on cells containing a microsatellite sequence at the 5' end of an antibiotic-resistance gene; the vector carrying this sequence was integrated in the genome of the cells. In general, interrupted sequences had lower mutation rates than perfect ones of the same size, but the magnitude of the difference was dependent upon the sequence of the interrupting base(s). Some interrupted repeats had mutation rates that were lower than those of perfect sequences of the same length but similar to those of half the length. This suggests that interrupting bases effectively divide microsatellites into smaller repeat runs with mutational characteristics different from those of the corresponding full-length microsatellite. We conclude that interruptions decrease microsatellite mutation rate and influence the spectrum of frameshift mutations. The sequence of the interrupting base(s) determines the magnitude of the effect on mutation rate.
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Affiliation(s)
- Jayne C Boyer
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, CB #7525, Chapel Hill, NC 27599, United States.
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Butland SL, Devon RS, Huang Y, Mead CL, Meynert AM, Neal SJ, Lee SS, Wilkinson A, Yang GS, Yuen MMS, Hayden MR, Holt RA, Leavitt BR, Ouellette BFF. CAG-encoded polyglutamine length polymorphism in the human genome. BMC Genomics 2007; 8:126. [PMID: 17519034 PMCID: PMC1896166 DOI: 10.1186/1471-2164-8-126] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Accepted: 05/22/2007] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
Expansion of polyglutamine-encoding CAG trinucleotide repeats has been identified as the pathogenic mutation in nine different genes associated with neurodegenerative disorders. The majority of individuals clinically diagnosed with spinocerebellar ataxia do not have mutations within known disease genes, and it is likely that additional ataxias or Huntington disease-like disorders will be found to be caused by this common mutational mechanism. We set out to determine the length distributions of CAG-polyglutamine tracts for the entire human genome in a set of healthy individuals in order to characterize the nature of polyglutamine repeat length variation across the human genome, to establish the background against which pathogenic repeat expansions can be detected, and to prioritize candidate genes for repeat expansion disorders.
Results
We found that repeats, including those in known disease genes, have unique distributions of glutamine tract lengths, as measured by fragment analysis of PCR-amplified repeat regions. This emphasizes the need to characterize each distribution and avoid making generalizations between loci. The best predictors of known disease genes were occurrence of a long CAG-tract uninterrupted by CAA codons in their reference genome sequence, and high glutamine tract length variance in the normal population. We used these parameters to identify eight priority candidate genes for polyglutamine expansion disorders. Twelve CAG-polyglutamine repeats were invariant and these can likely be excluded as candidates. We outline some confusion in the literature about this type of data, difficulties in comparing such data between publications, and its application to studies of disease prevalence in different populations. Analysis of Gene Ontology-based functions of CAG-polyglutamine-containing genes provided a visual framework for interpretation of these genes' functions. All nine known disease genes were involved in DNA-dependent regulation of transcription or in neurogenesis, as were all of the well-characterized priority candidate genes.
Conclusion
This publication makes freely available the normal distributions of CAG-polyglutamine repeats in the human genome. Using these background distributions, against which pathogenic expansions can be identified, we have begun screening for mutations in individuals clinically diagnosed with novel forms of spinocerebellar ataxia or Huntington disease-like disorders who do not have identified mutations within the known disease-associated genes.
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Rozanska M, Sobczak K, Jasinska A, Napierala M, Kaczynska D, Czerny A, Koziel M, Kozlowski P, Olejniczak M, Krzyzosiak WJ. CAG and CTG repeat polymorphism in exons of human genes shows distinct features at the expandable loci. Hum Mutat 2007; 28:451-8. [PMID: 17226796 DOI: 10.1002/humu.20466] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Although the trinucleotide repeats are present in the exons of numerous human genes, the allele distribution is not well known, and the factors responsible for their intergenic and intragenic variability are not well understood. We have analyzed the length and sequence variation within the most commonly occurring CAG and CTG repeats in a large number of human genes selected to contain the longest reported repeat tracts. Our study revealed that in genes other than those implicated in the Triplet Repeat Expansion Diseases (TREDs), the very long and highly polymorphic repeats are rather infrequent. The length of pure repeat tract in the most frequent allele was found to correlate well with the rate of the repeat length polymorphism, and CAA triplets were shown to be the most frequent CAG repeat interruptions. As both the CAG and CAA triplets code for glutamine, our results may suggest that the selective pressure disfavors the long uninterrupted CAG repeats in genes and transcripts but not the long normal polyglutamine tracts in proteins. This may indicate that hairpin structures formed in ssDNA and RNA by long pure CAG repeats would be selected against as they may impede normal cellular processes.
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Affiliation(s)
- Matylda Rozanska
- Laboratory of Cancer Genetics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
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Martins S, Calafell F, Wong VCN, Sequeiros J, Amorim A. A multistep mutation mechanism drives the evolution of the CAG repeat at MJD/SCA3 locus. Eur J Hum Genet 2006; 14:932-40. [PMID: 16724006 DOI: 10.1038/sj.ejhg.5201643] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Despite the intense debate around the repeat instability reported on the large group of neurological disorders caused by trinucleotide repeat expansions, little is known about the mutation process underlying alleles in the normal range that, ultimately, expand to pathological size. In this study, we assessed the mutation mechanisms by which wild-type Machado-Joseph disease (MJD) alleles have been generated throughout human evolution. Haplotypes including the CAG repeat, six intragenic SNPs and four flanking microsatellites were analysed in 431 normal chromosomes of European, Asian and African origin. A bimodal CAG repeat length frequency distribution was found in the four most frequent wild-type lineages (H1-GCGGCA; H2-GTGGCA; H3-TTAGAC and H4-TTACAC). Based on flanking microsatellite haplotypes, the variance calculated by analysis of molecular variance between modal (CAG)n alleles was little or null in lineages H1, H2 and H4, as were the pairwise differences. Moreover, genetic distances among all the alleles from each lineage did not reflect the allele sizes differences, as expected if a stepwise mutation model was the main process of evolution. On the contrary, when exposed in maximum parsimonious phylogenetic trees, a large number of mutation steps separated same-size alleles, whereas several microsatellite haplotypes were shared by modal CAGs. In conclusion, our results suggest that the main mutation mechanism occurring in the evolution of the polymorphic CAG region at MJD/SCA3 locus is a multistep one, either by gene conversion or DNA slippage; repeats with 14, 21, 23 and 27 CAGs are the main alleles involved in this process.
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Affiliation(s)
- Sandra Martins
- IPATIMUP - Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Porto, Portugal.
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Kurosaki T, Ninokata A, Wang L, Ueda S. Evolutionary scenario for acquisition of CAG repeats in human SCA1 gene. Gene 2006; 373:23-7. [PMID: 16497448 DOI: 10.1016/j.gene.2005.12.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Revised: 12/15/2005] [Accepted: 12/21/2005] [Indexed: 01/20/2023]
Abstract
We investigated the CAG repeat sequence of the spinocerebellar ataxia type 1 (SCA1) gene in various species of primates to reveal how human has acquired the repeat structure with interruptions. Our results demonstrate no repetitive structure in the region corresponding to the human CAG repeats in prosimians and New World monkeys like in rodents, perfect (uninterrupted) CAG repeats in Old World monkeys, and interrupted CAG repeats in hominoids. Comparative analysis on the secondary structures of the primate SCA1 transcripts suggests the human prototype was built in the common ancestor of simians. We show an evolutionary scenario for acquisition of CAG repeats with interruptions in the human SCA1 gene.
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Affiliation(s)
- Tatsuaki Kurosaki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Yu F, Sabeti PC, Hardenbol P, Fu Q, Fry B, Lu X, Ghose S, Vega R, Perez A, Pasternak S, Leal SM, Willis TD, Nelson DL, Belmont J, Gibbs RA. Positive selection of a pre-expansion CAG repeat of the human SCA2 gene. PLoS Genet 2005; 1:e41. [PMID: 16205789 PMCID: PMC1239938 DOI: 10.1371/journal.pgen.0010041] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Accepted: 08/26/2005] [Indexed: 11/18/2022] Open
Abstract
A region of approximately one megabase of human Chromosome 12 shows extensive linkage disequilibrium in Utah residents with ancestry from northern and western Europe. This strikingly large linkage disequilibrium block was analyzed with statistical and experimental methods to determine whether natural selection could be implicated in shaping the current genome structure. Extended Haplotype Homozygosity and Relative Extended Haplotype Homozygosity analyses on this region mapped a core region of the strongest conserved haplotype to the exon 1 of the Spinocerebellar ataxia type 2 gene (SCA2). Direct DNA sequencing of this region of the SCA2 gene revealed a significant association between a pre-expanded allele [(CAG)8CAA(CAG)4CAA(CAG)8] of CAG repeats within exon 1 and the selected haplotype of the SCA2 gene. A significantly negative Tajima's D value (-2.20, p < 0.01) on this site consistently suggested selection on the CAG repeat. This region was also investigated in the three other populations, none of which showed signs of selection. These results suggest that a recent positive selection of the pre-expansion SCA2 CAG repeat has occurred in Utah residents with European ancestry.
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Affiliation(s)
- Fuli Yu
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Pardis C Sabeti
- Broad Institute of the Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, United States of America
| | - Paul Hardenbol
- ParAllele Bioscience, South San Francisco, California, United States of America
| | - Qing Fu
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Ben Fry
- Broad Institute of the Massachusetts Institute of Technology, and Harvard University, Cambridge, Massachusetts, United States of America
| | - Xiuhua Lu
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Sy Ghose
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Richard Vega
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Ag Perez
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Shiran Pasternak
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Suzanne M Leal
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Thomas D Willis
- ParAllele Bioscience, South San Francisco, California, United States of America
| | - David L Nelson
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - John Belmont
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
| | - Richard A Gibbs
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, United States of America
- * To whom correspondence should be addressed. E-mail:
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Napierala M, Bacolla A, Wells RD. Increased negative superhelical density in vivo enhances the genetic instability of triplet repeat sequences. J Biol Chem 2005; 280:37366-76. [PMID: 16166072 DOI: 10.1074/jbc.m508065200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The influence of negative superhelical density on the genetic instabilities of long GAA.TTC, CGG.CCG, and CTG.CAG repeat sequences was studied in vivo in topologically constrained plasmids in Escherichia coli. These repeat tracts are involved in the etiologies of Friedreich ataxia, fragile X syndrome, and myotonic dystrophy type 1, respectively. The capacity of these DNA tracts to undergo deletions-expansions was explored with three genetic-biochemical approaches including first, the utilization of topoisomerase I and/or DNA gyrase mutants, second, the specific inhibition of DNA gyrase by novobiocin, and third, the genetic removal of the HU protein, thus lowering the negative supercoil density (-sigma). All three strategies revealed that higher -sigma in vivo enhanced the formation of deleted repeat sequences. The effects were most pronounced for the Friedreich ataxia and the fragile X triplet repeat sequences. Higher levels of -sigma stabilize non-B DNA conformations (i.e. triplexes, sticky DNA, flexible and writhed DNA, slipped structures) at appropriate repeat tracts; also, numerous prior genetic instability investigations invoke a role for these structures in promoting the slippage of the DNA complementary strands. Thus, we propose that the in vivo modulation of the DNA structure, localized to the repeat tracts, is responsible for these behaviors. Presuming that these interrelationships are also found in humans, dynamic alterations in the chromosomal nuclear matrix may modulate the -sigma of certain DNA regions and, thus, stabilize/destabilize certain non-B conformations which regulate the genetic expansions-deletions responsible for the diseases.
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Affiliation(s)
- Marek Napierala
- Institute of Biosciences and Technology, Center for Genome Research, Texas A&M University System Health Science Center, Houston, 77030-3303, USA
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Ralser M, Nonhoff U, Albrecht M, Lengauer T, Wanker EE, Lehrach H, Krobitsch S. Ataxin-2 and huntingtin interact with endophilin-A complexes to function in plastin-associated pathways. Hum Mol Genet 2005; 14:2893-909. [PMID: 16115810 DOI: 10.1093/hmg/ddi321] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Spinocerebellar ataxia type 2 is an inherited neurodegenerative disorder that is caused by an expanded trinucleotide repeat in the SCA2 gene, encoding a polyglutamine stretch in the gene product ataxin-2. Although evidence has been provided that ataxin-2 is involved in RNA metabolism, the physiological function of ataxin-2 remains unclear. Here, we demonstrate that ataxin-2 interacts with two members of the endophilin family, endophilin-A1 and endophilin-A3. To elucidate the physiological implications of these interactions, we exploited yeast as a model system and discovered that expression of ataxin-2 as well as both endophilin proteins is toxic for yeast lacking the SAC6 gene product fimbrin, a protein involved in actin filament organization and endocytotic processes. Intriguingly, expression of huntingtin, another polyglutamine protein interacting with endophilin-A3, was also toxic in Deltasac6 yeast. These effects can be suppressed by simultaneous expression of one of the two human fimbrin orthologs, L- or T-plastin. Moreover, we have discovered that ataxin-2 associates with L- and T-plastin and that overexpression of ataxin-2 leads to accumulation of T-plastin in mammalian cells. Thus, our findings suggest an interplay between ataxin-2, endophilin proteins and huntingtin in plastin-associated cellular pathways.
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Affiliation(s)
- Markus Ralser
- Max Planck Institute for Molecular Genetics, Ihnestrasse 73, 14195 Berlin, Germany
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50
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Mittal U, Sharma S, Chopra R, Dheeraj K, Pal PK, Srivastava AK, Mukerji M. Insights into the mutational history and prevalence of SCA1 in the Indian population through anchored polymorphisms. Hum Genet 2005; 118:107-14. [PMID: 16133185 DOI: 10.1007/s00439-005-0018-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Accepted: 06/15/2005] [Indexed: 11/27/2022]
Abstract
There is a wide variation in prevalence of spinocerebellar ataxia type 1 (SCA1) in different populations. In the present study, we observed SCA1 in approximately 22% (37/167 families) of the autosomal dominant cerebellar ataxias (ADCAs) in the Indian population. We investigated the role of various genetic factors like repeat length, interruption pattern and chromosomal background in predisposing the repeats to instability in these families. We analyzed 12 markers (9 SNPs and 3 microsatellite markers) and found 3 of them, spanning a region of approximately 65 kbp to be linked with the disease locus in the Indian population. The haplotype C-4-C defined by rs1476464 (SNP9)-D6S288-rs2075974 (SNP1), which was extremely rare in nonaffected chromosomes (approximately 3%), was observed to be significantly (P<0.0000) associated with the expanded chromosomes in approximately 44% of SCA1 families. This haplotype was found in all nonhuman primates. SNP1 (C/T), which showed a skewed allelic distribution between large (LN > 30 repeats) and small normal (SN <or= 30 repeats) alleles (P<0.0000) had similar allelic distribution (P=0.3477) in LN and expanded alleles. Our study suggested that LN and expanded chromosomes linked with the ancestral C allele of SNP1 might have originated simultaneously during evolution by the lengthening of repeats. The LN alleles might have accumulated repeat stabilizing non-CAG interruptions during this process. Similar proportions of T allele in SN with single interruptions, LN and expanded chromosomes lend credence to the origin of expanded alleles from singly-interrupted chromosomes. Our analyses using markers linked (anchoring) to SCA1 suggest that prevalence of SCA1 is correlated to both repeat length and number of interruptions in the Indian population. The spectrum of these alleles also points toward the antiquity of SCA1 mutation in the Indian population.
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Affiliation(s)
- Uma Mittal
- Functional Genomics Unit, Institute of Genomics and Integrative Biology, CSIR, Mall Road, Delhi, 110007, India
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