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Tanudisastro HA, Deveson IW, Dashnow H, MacArthur DG. Sequencing and characterizing short tandem repeats in the human genome. Nat Rev Genet 2024; 25:460-475. [PMID: 38366034 DOI: 10.1038/s41576-024-00692-3] [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: 12/06/2023] [Indexed: 02/18/2024]
Abstract
Short tandem repeats (STRs) are highly polymorphic sequences throughout the human genome that are composed of repeated copies of a 1-6-bp motif. Over 1 million variable STR loci are known, some of which regulate gene expression and influence complex traits, such as height. Moreover, variants in at least 60 STR loci cause genetic disorders, including Huntington disease and fragile X syndrome. Accurately identifying and genotyping STR variants is challenging, in particular mapping short reads to repetitive regions and inferring expanded repeat lengths. Recent advances in sequencing technology and computational tools for STR genotyping from sequencing data promise to help overcome this challenge and solve genetically unresolved cases and the 'missing heritability' of polygenic traits. Here, we compare STR genotyping methods, analytical tools and their applications to understand the effect of STR variation on health and disease. We identify emergent opportunities to refine genotyping and quality-control approaches as well as to integrate STRs into variant-calling workflows and large cohort analyses.
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Affiliation(s)
- Hope A Tanudisastro
- Centre for Population Genomics, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, Victoria, Australia
- Faculty of Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
- Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
| | - Ira W Deveson
- Faculty of Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
- Genomics and Inherited Disease Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Harriet Dashnow
- Department of Human Genetics, University of Utah, Salt Lake City, UT, USA.
| | - Daniel G MacArthur
- Centre for Population Genomics, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.
- Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, Victoria, Australia.
- Faculty of Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia.
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Kernohan KD, Boycott KM. The expanding diagnostic toolbox for rare genetic diseases. Nat Rev Genet 2024; 25:401-415. [PMID: 38238519 DOI: 10.1038/s41576-023-00683-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/22/2023] [Indexed: 05/23/2024]
Abstract
Genomic technologies, such as targeted, exome and short-read genome sequencing approaches, have revolutionized the care of patients with rare genetic diseases. However, more than half of patients remain without a diagnosis. Emerging approaches from research-based settings such as long-read genome sequencing and optical genome mapping hold promise for improving the identification of disease-causal genetic variants. In addition, new omic technologies that measure the transcriptome, epigenome, proteome or metabolome are showing great potential for variant interpretation. As genetic testing options rapidly expand, the clinical community needs to be mindful of their individual strengths and limitations, as well as remaining challenges, to select the appropriate diagnostic test, correctly interpret results and drive innovation to address insufficiencies. If used effectively - through truly integrative multi-omics approaches and data sharing - the resulting large quantities of data from these established and emerging technologies will greatly improve the interpretative power of genetic and genomic diagnostics for rare diseases.
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Affiliation(s)
- Kristin D Kernohan
- CHEO Research Institute, University of Ottawa, Ottawa, ON, Canada
- Newborn Screening Ontario, CHEO, Ottawa, ON, Canada
| | - Kym M Boycott
- CHEO Research Institute, University of Ottawa, Ottawa, ON, Canada.
- Department of Genetics, CHEO, Ottawa, ON, Canada.
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McNeill A. 2023 in the European Journal of Human Genetics. Eur J Hum Genet 2024; 32:135-137. [PMID: 38332347 PMCID: PMC10853252 DOI: 10.1038/s41431-024-01540-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024] Open
Affiliation(s)
- Alisdair McNeill
- Division of Neuroscience and Neuroscience Institute, The University of Sheffield, Sheffield, UK.
- Sheffield Clinical Genetics Service, Sheffield Children's Hospital NHS Foundation Trust, Sheffield, UK.
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4
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Rafehi H, Bennett MF, Bahlo M. Detection and discovery of repeat expansions in ataxia enabled by next-generation sequencing: present and future. Emerg Top Life Sci 2023; 7:349-359. [PMID: 37733280 PMCID: PMC10754322 DOI: 10.1042/etls20230018] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 08/29/2023] [Accepted: 09/12/2023] [Indexed: 09/22/2023]
Abstract
Hereditary cerebellar ataxias are a heterogenous group of progressive neurological disorders that are disproportionately caused by repeat expansions (REs) of short tandem repeats (STRs). Genetic diagnosis for RE disorders such as ataxias are difficult as the current gold standard for diagnosis is repeat-primed PCR assays or Southern blots, neither of which are scalable nor readily available for all STR loci. In the last five years, significant advances have been made in our ability to detect STRs and REs in short-read sequencing data, especially whole-genome sequencing. Given the increasing reliance of genomics in diagnosis of rare diseases, the use of established RE detection pipelines for RE disorders is now a highly feasible and practical first-step alternative to molecular testing methods. In addition, many new pathogenic REs have been discovered in recent years by utilising WGS data. Collectively, genomes are an important resource/platform for further advancements in both the discovery and diagnosis of REs that cause ataxia and will lead to much needed improvement in diagnostic rates for patients with hereditary ataxia.
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Affiliation(s)
- Haloom Rafehi
- Population Health and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
| | - Mark F Bennett
- Population Health and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
- Epilepsy Research Centre, Department of Medicine, University of Melbourne, Austin Health, Heidelberg, VIC, Australia
| | - Melanie Bahlo
- Population Health and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
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Read JL, Davies KC, Thompson GC, Delatycki MB, Lockhart PJ. Challenges facing repeat expansion identification, characterisation, and the pathway to discovery. Emerg Top Life Sci 2023; 7:339-348. [PMID: 37888797 PMCID: PMC10754332 DOI: 10.1042/etls20230019] [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: 07/31/2023] [Revised: 10/06/2023] [Accepted: 10/12/2023] [Indexed: 10/28/2023]
Abstract
Tandem repeat DNA sequences constitute a significant proportion of the human genome. While previously considered to be functionally inert, these sequences are now broadly accepted as important contributors to genetic diversity. However, the polymorphic nature of these sequences can lead to expansion beyond a gene-specific threshold, causing disease. More than 50 pathogenic repeat expansions have been identified to date, many of which have been discovered in the last decade as a result of advances in sequencing technologies and associated bioinformatic tools. Commonly utilised diagnostic platforms including Sanger sequencing, capillary array electrophoresis, and Southern blot are generally low throughput and are often unable to accurately determine repeat size, composition, and epigenetic signature, which are important when characterising repeat expansions. The rapid advances in bioinformatic tools designed specifically to interrogate short-read sequencing and the development of long-read single molecule sequencing is enabling a new generation of high throughput testing for repeat expansion disorders. In this review, we discuss some of the challenges surrounding the identification and characterisation of disease-causing repeat expansions and the technological advances that are poised to translate the promise of genomic medicine to individuals and families affected by these disorders.
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Affiliation(s)
- Justin L Read
- Bruce Lefroy Centre, Murdoch Children's Research Institute, Parkville, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Parkville, Victoria, Australia
| | - Kayli C Davies
- Bruce Lefroy Centre, Murdoch Children's Research Institute, Parkville, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Parkville, Victoria, Australia
| | - Genevieve C Thompson
- Bruce Lefroy Centre, Murdoch Children's Research Institute, Parkville, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Parkville, Victoria, Australia
| | - Martin B Delatycki
- Bruce Lefroy Centre, Murdoch Children's Research Institute, Parkville, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Parkville, Victoria, Australia
- Victorian Clinical Genetics Services, Parkville, Victoria, Australia
| | - Paul J Lockhart
- Bruce Lefroy Centre, Murdoch Children's Research Institute, Parkville, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Parkville, Victoria, Australia
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Waung MW, Ma F, Wheeler AG, Zai CC, So J. The Diagnostic Landscape of Adult Neurogenetic Disorders. BIOLOGY 2023; 12:1459. [PMID: 38132285 PMCID: PMC10740572 DOI: 10.3390/biology12121459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 11/11/2023] [Accepted: 11/16/2023] [Indexed: 12/23/2023]
Abstract
Neurogenetic diseases affect individuals across the lifespan, but accurate diagnosis remains elusive for many patients. Adults with neurogenetic disorders often undergo a long diagnostic odyssey, with multiple specialist evaluations and countless investigations without a satisfactory diagnostic outcome. Reasons for these diagnostic challenges include: (1) clinical features of neurogenetic syndromes are diverse and under-recognized, particularly those of adult-onset, (2) neurogenetic syndromes may manifest with symptoms that span multiple neurological and medical subspecialties, and (3) a positive family history may not be present or readily apparent. Furthermore, there is a large gap in the understanding of how to apply genetic diagnostic tools in adult patients, as most of the published literature focuses on the pediatric population. Despite these challenges, accurate genetic diagnosis is imperative to provide affected individuals and their families guidance on prognosis, recurrence risk, and, for an increasing number of disorders, offer targeted treatment. Here, we provide a framework for recognizing adult neurogenetic syndromes, describe the current diagnostic approach, and highlight studies using next-generation sequencing in different neurological disease cohorts. We also discuss diagnostic pitfalls, barriers to achieving a definitive diagnosis, and emerging technology that may increase the diagnostic yield of testing.
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Affiliation(s)
- Maggie W. Waung
- Division of General Neurology, Department of Neurology, Weill Institute for Neurosciences, University of California, San Francisco, CA 94158, USA
| | - Fion Ma
- Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, CA 94143, USA
| | - Allison G. Wheeler
- Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, CA 94143, USA
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Clement C. Zai
- Tanenbaum Centre for Pharmacogenetics, Molecular Brain Science, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada
- Department of Psychiatry, Institute of Medical Science, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Joyce So
- Division of Medical Genetics, Department of Pediatrics, University of California, San Francisco, CA 94158, USA
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McNeill A. New year, new genes. Eur J Hum Genet 2023; 31:1-2. [PMID: 36609690 PMCID: PMC9822939 DOI: 10.1038/s41431-022-01271-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- Alisdair McNeill
- Department of Neuroscience, The University of Sheffield, Sheffield, UK.
- Sheffield Clinical Genetics Department, Sheffield Children's Hospital NHS Foundation Trust, Sheffield, UK.
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