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Abstract
Neurodevelopmental disorders are the most prevalent chronic medical conditions encountered in pediatric primary care. In addition to identifying appropriate descriptive diagnoses and guiding families to evidence-based treatments and supports, comprehensive care for individuals with neurodevelopmental disorders includes a search for an underlying etiologic diagnosis, primarily through a genetic evaluation. Identification of an underlying genetic etiology can inform prognosis, clarify recurrence risk, shape clinical management, and direct patients and families to condition-specific resources and supports. Here we review the utility of genetic testing in patients with neurodevelopmental disorders and describe the three major testing modalities and their yields - chromosomal microarray, exome sequencing (with/without copy number variant calling), and FMR1 CGG repeat analysis for fragile X syndrome. Given the diagnostic yield of genetic testing and the potential for clinical and personal utility, there is consensus that genetic testing should be offered to all patients with global developmental delay, intellectual disability, and/or autism spectrum disorder. Despite this recommendation, data suggest that a minority of children with autism spectrum disorder and intellectual disability have undergone genetic testing. To address this gap in care, we describe a structured but flexible approach to facilitate integration of genetic testing into clinical practice across pediatric specialties and discuss future considerations for genetic testing in neurodevelopmental disorders to prepare pediatric providers to care for patients with such diagnoses today and tomorrow.
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Affiliation(s)
- Juliann M. Savatt
- Autism & Developmental Medicine Institute, Geisinger, Danville, PA, United States
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2
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Martin HC, Gardner EJ, Samocha KE, Kaplanis J, Akawi N, Sifrim A, Eberhardt RY, Tavares ALT, Neville MDC, Niemi MEK, Gallone G, McRae J, Wright CF, FitzPatrick DR, Firth HV, Hurles ME. The contribution of X-linked coding variation to severe developmental disorders. Nat Commun 2021; 12:627. [PMID: 33504798 PMCID: PMC7840967 DOI: 10.1038/s41467-020-20852-3] [Citation(s) in RCA: 22] [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] [Received: 03/16/2020] [Accepted: 12/08/2020] [Indexed: 12/14/2022] Open
Abstract
Over 130 X-linked genes have been robustly associated with developmental disorders, and X-linked causes have been hypothesised to underlie the higher developmental disorder rates in males. Here, we evaluate the burden of X-linked coding variation in 11,044 developmental disorder patients, and find a similar rate of X-linked causes in males and females (6.0% and 6.9%, respectively), indicating that such variants do not account for the 1.4-fold male bias. We develop an improved strategy to detect X-linked developmental disorders and identify 23 significant genes, all of which were previously known, consistent with our inference that the vast majority of the X-linked burden is in known developmental disorder-associated genes. Importantly, we estimate that, in male probands, only 13% of inherited rare missense variants in known developmental disorder-associated genes are likely to be pathogenic. Our results demonstrate that statistical analysis of large datasets can refine our understanding of modes of inheritance for individual X-linked disorders.
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Affiliation(s)
- Hilary C Martin
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK.
| | | | | | - Joanna Kaplanis
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK
| | - Nadia Akawi
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Alejandro Sifrim
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK
- Department of Human Genetics, University of Leuven, Leuven, Belgium
| | | | - Ana Lisa Taylor Tavares
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK
- Department of Clinical Genetics, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
- Genomics England, Queen Mary University of London, London, EC1M 6BQ, UK
| | | | - Mari E K Niemi
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK
- Institute for Molecular Medicine Finland, University of Helsinki, Tukholmankatu 8, Helsinki, FI-00014, Finland
| | - Giuseppe Gallone
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK
- Max Planck Institute for Molecular Genetics, Ihnestraße 63, 14195, Berlin, Germany
| | - Jeremy McRae
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK
- Illumina Inc., 5200 Illumina Way, San Diego, CA, 92122, USA
| | - Caroline F Wright
- Institute of Biomedical & Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - David R FitzPatrick
- MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK
| | - Helen V Firth
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK
- Department of Clinical Genetics, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
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3
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Palmer EE, Carroll R, Shaw M, Kumar R, Minoche AE, Leffler M, Murray L, Macintosh R, Wright D, Troedson C, McKenzie F, Townshend S, Ward M, Nawaz U, Ravine A, Runke CK, Thorland EC, Hummel M, Foulds N, Pichon O, Isidor B, Le Caignec C, Demeer B, Andrieux J, Albarazi SH, Bye A, Sachdev R, Kirk EP, Cowley MJ, Field M, Gecz J. RLIM Is a Candidate Dosage-Sensitive Gene for Individuals with Varying Duplications of Xq13, Intellectual Disability, and Distinct Facial Features. Am J Hum Genet 2020; 107:1157-1169. [PMID: 33159883 PMCID: PMC7820564 DOI: 10.1016/j.ajhg.2020.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 10/13/2020] [Indexed: 12/21/2022] Open
Abstract
Interpretation of the significance of maternally inherited X chromosome variants in males with neurocognitive phenotypes continues to present a challenge to clinical geneticists and diagnostic laboratories. Here we report 14 males from 9 families with duplications at the Xq13.2-q13.3 locus with a common facial phenotype, intellectual disability (ID), distinctive behavioral features, and a seizure disorder in two cases. All tested carrier mothers had normal intelligence. The duplication arose de novo in three mothers where grandparental testing was possible. In one family the duplication segregated with ID across three generations. RLIM is the only gene common to our duplications. However, flanking genes duplicated in some but not all the affected individuals included the brain-expressed genes NEXMIF, SLC16A2, and the long non-coding RNA gene FTX. The contribution of the RLIM-flanking genes to the phenotypes of individuals with different size duplications has not been fully resolved. Missense variants in RLIM have recently been identified to cause X-linked ID in males, with heterozygous females typically having normal intelligence and highly skewed X chromosome inactivation. We detected consistent and significant increase of RLIM mRNA and protein levels in cells derived from seven affected males from five families with the duplication. Subsequent analysis of MDM2, one of the targets of the RLIM E3 ligase activity, showed consistent downregulation in cells from the affected males. All the carrier mothers displayed normal RLIM mRNA levels and had highly skewed X chromosome inactivation. We propose that duplications at Xq13.2-13.3 including RLIM cause a recognizable but mild neurocognitive phenotype in hemizygous males.
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Affiliation(s)
- Elizabeth E Palmer
- Genetics of Learning Disability Service, Waratah, NSW 2298, Australia; School of Women's and Children's Health, UNSW Medicine, University of New South Wales, Randwick, NSW 2031, Australia; Sydney Children's Hospital, Randwick, NSW 2031, Australia; Kinghorn Centre for Clinical Genomics, Garvan Institute, Darlinghurst, Sydney, NSW 2010, Australia.
| | - Renee Carroll
- Adelaide Medical School and the Robinson Research Institute, University of Adelaide, Adelaide, SA 5000, Australia
| | - Marie Shaw
- Adelaide Medical School and the Robinson Research Institute, University of Adelaide, Adelaide, SA 5000, Australia
| | - Raman Kumar
- Adelaide Medical School and the Robinson Research Institute, University of Adelaide, Adelaide, SA 5000, Australia
| | - Andre E Minoche
- St Vincent's Clinical School, University of New South Wales, Sydney, NSW 2010, Australia
| | - Melanie Leffler
- Genetics of Learning Disability Service, Waratah, NSW 2298, Australia
| | - Lucinda Murray
- Genetics of Learning Disability Service, Waratah, NSW 2298, Australia
| | | | - Dale Wright
- Discipline of Genomic Medicine and Discipline of Child & Adolescent Health, University of Sydney, Sydney, NSW 2010, Australia; Department of Cytogenetics, The Children's Hospital at Westmead, Westmead, NSW 2145, Australia
| | - Chris Troedson
- Children's Hospital at Westmead, Sydney, NSW 2145, Australia
| | - Fiona McKenzie
- School of Paediatrics and Child Health, University of Western Australia, Perth, WA 6009, Australia; Genetic Services of Western Australia, Perth, WA 6008, Australia
| | | | - Michelle Ward
- Genetic Services of Western Australia, Perth, WA 6008, Australia
| | - Urwah Nawaz
- Adelaide Medical School and the Robinson Research Institute, University of Adelaide, Adelaide, SA 5000, Australia
| | - Anja Ravine
- Department of Cytogenetics, The Children's Hospital at Westmead, Westmead, NSW 2145, Australia; Pathwest Laboratory Medicine WA, Perth, WA 6008, Australia
| | - Cassandra K Runke
- Genomics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Scottsdale, AZ 85259, USA
| | - Erik C Thorland
- Genomics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Scottsdale, AZ 85259, USA
| | - Marybeth Hummel
- West Virginia University School of Medicine, Department of Pediatrics, Section of Medical Genetics Morgantown, WV 26506-9600, USA
| | - Nicola Foulds
- Wessex Clinical Genetics Services, Southampton SO16 5YA, UK
| | - Olivier Pichon
- Service de génétique médicale - Unité de Génétique Clinique, CHU de Nantes - Hôtel Dieu, Nantes 44093, France
| | - Bertrand Isidor
- Service de génétique médicale - Unité de Génétique Clinique, CHU de Nantes - Hôtel Dieu, Nantes 44093, France
| | - Cédric Le Caignec
- Service de génétique médicale, Institut fédératif de Biologie, CHU Hopital Purpan, Toulouse 31059, France
| | - Bénédicte Demeer
- Center for Human Genetics, CLAD Nord de France, CHU Amiens-Picardie, Amiens 80080, France; CHIMERE EA 7516, University Picardie Jules Verne, Amiens 80025, France
| | - Joris Andrieux
- Institut de Biochimie et Génétique Moléculaire, CHU Lille, Lille 59000, France
| | | | - Ann Bye
- School of Women's and Children's Health, UNSW Medicine, University of New South Wales, Randwick, NSW 2031, Australia; Sydney Children's Hospital, Randwick, NSW 2031, Australia
| | - Rani Sachdev
- School of Women's and Children's Health, UNSW Medicine, University of New South Wales, Randwick, NSW 2031, Australia; Sydney Children's Hospital, Randwick, NSW 2031, Australia
| | - Edwin P Kirk
- School of Women's and Children's Health, UNSW Medicine, University of New South Wales, Randwick, NSW 2031, Australia; Sydney Children's Hospital, Randwick, NSW 2031, Australia
| | - Mark J Cowley
- Children's Cancer Institute, Lowy Cancer Research Centre, University of New South Wales, Randwick, NSW 2033, Australia
| | - Mike Field
- Genetics of Learning Disability Service, Waratah, NSW 2298, Australia
| | - Jozef Gecz
- Adelaide Medical School and the Robinson Research Institute, University of Adelaide, Adelaide, SA 5000, Australia; Healthy Mothers, Babies and Children, South Australian Health and Medical Research Institute, Adelaide, SA 5000, Australia.
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Capalbo A, Poli M, Riera-Escamilla A, Shukla V, Kudo Høffding M, Krausz C, Hoffmann ER, Simon C. Preconception genome medicine: current state and future perspectives to improve infertility diagnosis and reproductive and health outcomes based on individual genomic data. Hum Reprod Update 2020; 27:254-279. [PMID: 33197264 DOI: 10.1093/humupd/dmaa044] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 08/13/2020] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Our genetic code is now readable, writable and hackable. The recent escalation of genome-wide sequencing (GS) applications in population diagnostics will not only enable the assessment of risks of transmitting well-defined monogenic disorders at preconceptional stages (i.e. carrier screening), but also facilitate identification of multifactorial genetic predispositions to sub-lethal pathologies, including those affecting reproductive fitness. Through GS, the acquisition and curation of reproductive-related findings will warrant the expansion of genetic assessment to new areas of genomic prediction of reproductive phenotypes, pharmacogenomics and molecular embryology, further boosting our knowledge and therapeutic tools for treating infertility and improving women's health. OBJECTIVE AND RATIONALE In this article, we review current knowledge and potential development of preconception genome analysis aimed at detecting reproductive and individual health risks (recessive genetic disease and medically actionable secondary findings) as well as anticipating specific reproductive outcomes, particularly in the context of IVF. The extension of reproductive genetic risk assessment to the general population and IVF couples will lead to the identification of couples who carry recessive mutations, as well as sub-lethal conditions prior to conception. This approach will provide increased reproductive autonomy to couples, particularly in those cases where preimplantation genetic testing is an available option to avoid the transmission of undesirable conditions. In addition, GS on prospective infertility patients will enable genome-wide association studies specific for infertility phenotypes such as predisposition to premature ovarian failure, increased risk of aneuploidies, complete oocyte immaturity or blastocyst development failure, thus empowering the development of true reproductive precision medicine. SEARCH METHODS Searches of the literature on PubMed Central included combinations of the following MeSH terms: human, genetics, genomics, variants, male, female, fertility, next generation sequencing, genome exome sequencing, expanded carrier screening, secondary findings, pharmacogenomics, controlled ovarian stimulation, preconception, genetics, genome-wide association studies, GWAS. OUTCOMES Through PubMed Central queries, we identified a total of 1409 articles. The full list of articles was assessed for date of publication, limiting the search to studies published within the last 15 years (2004 onwards due to escalating research output of next-generation sequencing studies from that date). The remaining articles' titles were assessed for pertinence to the topic, leaving a total of 644 articles. The use of preconception GS has the potential to identify inheritable genetic conditions concealed in the genome of around 4% of couples looking to conceive. Genomic information during reproductive age will also be useful to anticipate late-onset medically actionable conditions with strong genetic background in around 2-4% of all individuals. Genetic variants correlated with differential response to pharmaceutical treatment in IVF, and clear genotype-phenotype associations are found for aberrant sperm types, oocyte maturation, fertilization or pre- and post-implantation embryonic development. All currently known capabilities of GS at the preconception stage are reviewed along with persisting and forthcoming barriers for the implementation of precise reproductive medicine. WIDER IMPLICATIONS The expansion of sequencing analysis to additional monogenic and polygenic traits may enable the development of cost-effective preconception tests capable of identifying underlying genetic causes of infertility, which have been defined as 'unexplained' until now, thus leading to the development of a true personalized genomic medicine framework in reproductive health.
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Affiliation(s)
- Antonio Capalbo
- Igenomix Italy, Marostica, Italy.,Igenomix Foundation, INCLIVA, Valencia, Spain
| | | | - Antoni Riera-Escamilla
- Andrology Department, Fundació Puigvert, Universitat Autònoma de Barcelona, Instituto de Investigaciones Biomédicas Sant Pau (IIB-Sant Pau), Barcelona, Spain
| | - Vallari Shukla
- Department of Cellular and Molecular Medicine, DRNF Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
| | - Miya Kudo Høffding
- Department of Cellular and Molecular Medicine, DRNF Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
| | - Csilla Krausz
- Andrology Department, Fundació Puigvert, Universitat Autònoma de Barcelona, Instituto de Investigaciones Biomédicas Sant Pau (IIB-Sant Pau), Barcelona, Spain.,Department of Experimental and Clinical Biomedical Sciences "Mario Serio", Centre of Excellence DeNothe, University of Florence, Florence, Italy
| | - Eva R Hoffmann
- Department of Cellular and Molecular Medicine, DRNF Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
| | - Carlos Simon
- Igenomix Foundation, INCLIVA, Valencia, Spain.,Department of Obstetrics and Gynecology, University of Valencia, Valencia, Spain.,Department of Obstetrics and Gynecology BIDMC, Harvard University, Cambridge, MA, USA
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De Luca C, Race V, Keldermans L, Bauters M, Van Esch H. Challenges in molecular diagnosis of X-linked Intellectual disability. Br Med Bull 2020; 133:36-48. [PMID: 32043524 DOI: 10.1093/bmb/ldz039] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 11/25/2019] [Accepted: 11/26/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND Intellectual disability (ID) affects 1-3% of the Western population and is heterogeneous in origin. Mutations in X-linked genes represent 5-10% of ID in males. Fragile X syndrome, due to the silencing of the FMR1 gene, is the most common form of ID, with a prevalence of around 1:5000 males. Females are usually non- or mildly affected carriers, and in a few rare cases, the only gender affected. Array comparative genome hybridization (aCGH) and next-generation sequencing (NGS) have dramatically changed the nature of human genome analysis leading to the identification of new X-linked intellectual disability syndromes and disease-causing genes. SOURCES OF DATA Original papers, reviews, guidelines and experiences of the diagnostic laboratories. AREAS OF AGREEMENT Family history and clinical examination still are essential to choose the appropriate diagnostic tests, including, a disease-specific genetic test, aCGH or FMR1 molecular analysis. If negative, NGS approaches like well-defined gene panels, whole exome, or even whole genome sequencing, are increasingly being used, improving diagnostics and leading to the identification of novel disease mechanisms. AREAS OF CONTROVERSY The main challenge in the era of NGS is filtering and interpretation of the data generated by the analysis of a single individual. In X-linked cases, assessing pathogenicity is particularly challenging, even more when the variant is found to be inherited from a healthy carrier mother or when a heterozygous X-linked mutation is found in an impaired female. GROWING POINTS At present, variant interpretation remains a challenging task, especially in X-linked disorders. We review the main difficulties and propose a comprehensive overview that might aid in variant interpretation. Establishing a genetic diagnosis facilitates counseling and allows better delineation of clinical phenotypes. AREAS TIMELY FOR DEVELOPING RESEARCH To improve variant interpretation, there is need to refine in silico predictions with specific criteria for each gene, and to develop cost-effective functional tools, which can be easily transferred to diagnostics.
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Affiliation(s)
- Chiara De Luca
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Valérie Race
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Liesbeth Keldermans
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Marijke Bauters
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Hilde Van Esch
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium.,Laboratory for the Genetics of Cognition, Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium
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Waggoner D, Wain KE, Dubuc AM, Conlin L, Hickey SE, Lamb AN, Martin CL, Morton CC, Rasmussen K, Schuette JL, Schwartz S, Miller DT. Yield of additional genetic testing after chromosomal microarray for diagnosis of neurodevelopmental disability and congenital anomalies: a clinical practice resource of the American College of Medical Genetics and Genomics (ACMG). Genet Med 2018; 20:1105-1113. [PMID: 29915380 PMCID: PMC6410698 DOI: 10.1038/s41436-018-0040-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 04/04/2018] [Indexed: 11/16/2022] Open
Abstract
Purpose: Chromosomal microarray (CMA) is recommended as the first tier test in evaluation of individuals with neurodevelopmental disability and congenital anomalies. CMA may not detect balanced cytogenomic abnormalities or uniparental disomy (UPD), and deletion/duplications and regions of homozygosity may require additional testing to clarify the mechanism and inform accurate counseling. We conducted an evidence review to synthesize data regarding the benefit of additional testing after CMA to inform a genetic diagnosis. Methods: The review was guided by key questions related to the detection of genomic events that may require additional testing. A PubMed search for original research articles, systematic reviews, and meta-analyses were evaluated from articles published between January 1, 1983 and March 31, 2017. Based on the key questions, articles were retrieved and data extracted in parallel with comparison of results and discussion to resolve discrepancies. Variables assessed included study design and outcomes. Results: A narrative synthesis was created for each question to describe the occurrence of, and clinical significance of, additional diagnostic findings from subsequent testing performed after CMA. Conclusion: These findings may be used to assist the laboratory and clinician when making recommendations about additional testing after CMA, as it impacts clinical care, counseling, and diagnosis.
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Affiliation(s)
- Darrel Waggoner
- Department of Human Genetics, University of Chicago, Chicago, Illinois, USA.
| | - Karen E Wain
- Autism & Developmental Medicine Institute, Geisinger Health System, Danville, Pennsylvania, USA
| | - Adrian M Dubuc
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Laura Conlin
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | - Scott E Hickey
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, USA
| | - Allen N Lamb
- Department of Pathology, ARUP Laboratories, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - Christa Lese Martin
- Autism & Developmental Medicine Institute, Geisinger Health System, Danville, Pennsylvania, USA
| | - Cynthia C Morton
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.,Department of Obstetrics and Gynecology and Reproductive Biology, Brigham and Women's Hospital, Broad Institute of MIT and Harvard, Harvard Medical School, Boston, Massachusetts, USA.,Division of Evolution and Genomics Science, School of Biological Sciences, Manchester Academic Health Science Center, Manchester, UK
| | - Kristen Rasmussen
- Department of Medical Genetics, Marshfield Clinic, Marshfield, Wisconsin, USA
| | - Jane L Schuette
- Department of Human Genetics, University of Michigan School of Medicine, Ann Arbor, Michigan, USA
| | - Stuart Schwartz
- Laboratory Corporation of America® Holdings, Burlington, North Carolina, USA
| | - David T Miller
- Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
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7
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Doble B, Schofield DJ, Roscioli T, Mattick JS. Prioritising the application of genomic medicine. NPJ Genom Med 2017; 2:35. [PMID: 29263844 PMCID: PMC5698310 DOI: 10.1038/s41525-017-0037-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 10/20/2017] [Accepted: 10/25/2017] [Indexed: 12/25/2022] Open
Abstract
The clinical translation of genomic sequencing is hampered by the limited information available to guide investment into those areas where genomics is well placed to deliver improved health and economic outcomes. To date, genomic medicine has achieved its greatest successes through applications to diseases that have a high genotype–phenotype correlation and high penetrance, with a near certainty that the individual will develop the condition in the presence of the genotype. It has been anticipated that genomics will play an important role in promoting population health by targeting at-risk individuals and reducing the incidence of highly prevalent, costly, complex diseases, with potential applications across screening, prevention, and treatment decisions. However, where primary or secondary prevention requires behavioural changes, there is currently very little evidence to support reduction in disease incidence. A better understanding of the relationship between genomic variation and complex diseases will be necessary before effective genomic risk identification and management of the risk of complex diseases in healthy individuals can be carried out in clinical practice. Our recommended approach is that priority for genomic testing should focus on diseases where there is strong genotype–phenotype correlation, high or certain penetrance, the effects of the disease are serious and near-term, there is the potential for prevention and/or treatment, and the net costs incurred are acceptable for the health gains achieved.
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Affiliation(s)
- Brett Doble
- Garvan Institute of Medical Research, Sydney, NSW 2010 Australia.,Health Economics Research Centre, Nuffield Department of Population Health, University of Oxford, Oxford, OX3 7LF UK
| | - Deborah J Schofield
- Garvan Institute of Medical Research, Sydney, NSW 2010 Australia.,Faculty of Pharmacy, The University of Sydney, Sydney, NSW 2006 Australia.,Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, VIC 3052 Australia
| | - Tony Roscioli
- Department of Medical Genetics, Sydney Children's Hospital, Sydney, NSW 2031 Australia
| | - John S Mattick
- Garvan Institute of Medical Research, Sydney, NSW 2010 Australia.,St. Vincent's Clinical School, UNSW Australia, Sydney, NSW 2052 Australia
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8
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Affiliation(s)
- Brett Doble
- Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia; Centre for Health Economics, Monash Business School, Monash University, Melbourne, VIC, Australia
| | - Deborah J Schofield
- Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia; Faculty of Pharmacy, University of Sydney, NSW, Australia; Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, VIC, Australia
| | - Tony Roscioli
- Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia; Department of Medical Genetics, Sydney Children's Hospital, Sydney, NSW, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - John S Mattick
- Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia.
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9
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Shoubridge C, Walikonis RS, Gécz J, Harvey RJ. Subtle functional defects in the Arf-specific guanine nucleotide exchange factor IQSEC2 cause non-syndromic X-linked intellectual disability. Small GTPases 2014; 1:98-103. [PMID: 21686261 DOI: 10.4161/sgtp.1.2.13285] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 07/28/2010] [Accepted: 08/01/2010] [Indexed: 11/19/2022] Open
Abstract
Mutations in IQSEC2, a guanine nucleotide exchange factor for the ADP-ribosylation factor (Arf) family of small GTPases have recently been shown to cause non-syndromic X-linked intellectual disability (ID), characterised by substantial limitations in intellectual functioning and adaptive behaviour. This discovery was revealed by a combination of large-scale resequencing of the X chromosome, and key functional assays that revealed a reduction, but not elimination, of IQSEC2 GEF activity for mutations affecting conserved amino acids in the IQ-like and Sec7 domains. Compromised GTP binding activity of IQSEC2 leading to reduced activation of selected Arf substrates (Arf1, Arf6) is expected to impact on cytoskeletal organization, dendritic spine morphology and synaptic organisation. This study highlights the need for further investigation of the IQSEC gene family and Arf GTPases in neuronal morphology and synaptic function, and suggests that the genes encoding the ArfGEFs IQSEC1 and IQSEC3 should be considered as candidates for screening in autosomal ID.
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Affiliation(s)
- Cheryl Shoubridge
- Genetics and Molecular Pathology; SA Pathology; The University of Adelaide; Adelaide, Australia
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10
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Lubs HA, Stevenson RE, Schwartz CE. Fragile X and X-linked intellectual disability: four decades of discovery. Am J Hum Genet 2012; 90:579-90. [PMID: 22482801 DOI: 10.1016/j.ajhg.2012.02.018] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/03/2012] [Accepted: 02/17/2012] [Indexed: 01/18/2023] Open
Abstract
X-Linked intellectual disability (XLID) accounts for 5%-10% of intellectual disability in males. Over 150 syndromes, the most common of which is the fragile X syndrome, have been described. A large number of families with nonsyndromal XLID, 95 of which have been regionally mapped, have been described as well. Mutations in 102 X-linked genes have been associated with 81 of these XLID syndromes and with 35 of the regionally mapped families with nonsyndromal XLID. Identification of these genes has enabled considerable reclassification and better understanding of the biological basis of XLID. At the same time, it has improved the clinical diagnosis of XLID and allowed for carrier detection and prevention strategies through gamete donation, prenatal diagnosis, and genetic counseling. Progress in delineating XLID has far outpaced the efforts to understand the genetic basis for autosomal intellectual disability. In large measure, this has been because of the relative ease of identifying families with XLID and finding the responsible mutations, as well as the determined and interactive efforts of a small group of researchers worldwide.
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Affiliation(s)
- Herbert A Lubs
- Greenwood Genetic Center, JC Self Research Institute of Human Genetics, 113 Gregor Mendel Circle, Greenwood, SC 29646, USA
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11
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Raymond FL, Whittaker J, Jenkins L, Lench N, Chitty LS. Molecular prenatal diagnosis: the impact of modern technologies. Prenat Diagn 2010; 30:674-81. [PMID: 20572117 DOI: 10.1002/pd.2575] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Originally prenatal diagnosis was confined to the diagnosis of metabolic disorders and depended on assaying enzyme levels in amniotic fluid. With the development of recombinant DNA technology, molecular diagnosis became possible for some genetic conditions late in the 1970s. Here we briefly review the history of molecular prenatal diagnostic testing, using Duchenne muscular dystrophy as an example, and describe how over the last 30 years we have moved from offering testing to a few affected individuals using techniques, such as Southern blotting to identify deletions, to more rapid and accurate PCR-based testing which identifies the precise change in dystrophin for a greater number of families. We discuss the potential for safer, earlier prenatal genetic diagnosis using cell free fetal DNA in maternal blood before concluding by speculating on how more recent techniques, such as next generation sequencing, might further impact on the potential for molecular prenatal testing. Progress is not without its challenges, and as cytogenetics and molecular genetics begin to unite into one, we foresee the main challenge will not be in identifying the genetic change, but rather in interpreting its significance, particularly in the prenatal setting where we frequently have no phenotype on which to base interpretation.
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Affiliation(s)
- F Lucy Raymond
- Cambridge Institute for Medical Research, Department of Medical Genetics, University of Cambridge, Cambridge, UK
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