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Background: Dystonia is a clinically and genetically heterogeneous condition that occurs in isolation (isolated dystonia), in combination with other movement disorders (combined dystonia), or in the context of multisymptomatic phenotypes (isolated or combined dystonia with other neurological involvement). However, our understanding of its aetiology is still incomplete. We aimed to elucidate the monogenic causes for the major clinical categories of dystonia., Methods: For this exome-wide sequencing study, study participants were identified at 33 movement-disorder and neuropaediatric specialty centres in Austria, Czech Republic, France, Germany, Poland, Slovakia, and Switzerland. Each individual with dystonia was diagnosed in accordance with the dystonia consensus definition. Index cases were eligible for this study if they had no previous genetic diagnosis and no indication of an acquired cause of their illness. The second criterion was not applied to a subset of participants with a working clinical diagnosis of dystonic cerebral palsy. Genomic DNA was extracted from blood of participants and whole-exome sequenced. To find causative variants in known disorder-associated genes, all variants were filtered, and unreported variants were classified according to American College of Medical Genetics and Genomics guidelines. All considered variants were reviewed in expert round-table sessions to validate their clinical significance. Variants that survived filtering and interpretation procedures were defined as diagnostic variants. In the cases that went undiagnosed, candidate dystonia-causing genes were prioritised in a stepwise workflow., Findings: We sequenced the exomes of 764 individuals with dystonia and 346 healthy parents who were recruited between June 1, 2015, and July 31, 2019. We identified causative or probable causative variants in 135 (19%) of 728 families, involving 78 distinct monogenic disorders. We observed a larger proportion of individuals with diagnostic variants in those with dystonia (either isolated or combined) with coexisting non-movement disorder-related neurological symptoms (100 [45%] of 222; excepting cases with evidence of perinatal brain injury) than in those with combined (19 [19%] of 98) or isolated (16 [4%] of 388) dystonia. Across all categories of dystonia, 104 (65%) of the 160 detected variants affected genes which are associated with neurodevelopmental disorders. We found diagnostic variants in 11 genes not previously linked to dystonia, and propose a predictive clinical score that could guide the implementation of exome sequencing in routine diagnostics. In cases without perinatal sentinel events, genomic alterations contributed substantively to the diagnosis of dystonic cerebral palsy. In 15 families, we delineated 12 candidate genes. These include IMPDH2, encoding a key purine biosynthetic enzyme, for which robust evidence existed for its involvement in a neurodevelopmental disorder with dystonia. We identified six variants in IMPDH2, collected from four independent cohorts, that were predicted to be deleterious de-novo variants and expected to result in deregulation of purine metabolism., Interpretation: In this study, we have determined the role of monogenic variants across the range of dystonic disorders, providing guidance for the introduction of personalised care strategies and fostering follow-up pathophysiological explorations., Funding: Else Kröner-Fresenius-Stiftung, Technische Universität München, Helmholtz Zentrum München, Medizinische Universität Innsbruck, Charles University in Prague, Czech Ministry of Education, the Slovak Grant and Development Agency, the Slovak Research and Grant Agency., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Gene-panel and whole-exome analyses are now standard methodologies for mutation detection in Mendelian disease. However, the diagnostic yield achieved is at best 50%, leaving the genetic basis for disease unsolved in many individuals. New approaches are thus needed to narrow the diagnostic gap. Whole-genome sequencing is one potential strategy, but it currently has variant-interpretation challenges, particularly for non-coding changes. In this study we focus on transcriptome analysis, specifically total RNA sequencing (RNA-seq), by using monogenetic neuromuscular disorders as proof of principle. We examined a cohort of 25 exome and/or panel "negative" cases and provided genetic resolution in 36% (9/25). Causative mutations were identified in coding and non-coding exons, as well as in intronic regions, and the mutational pathomechanisms included transcriptional repression, exon skipping, and intron inclusion. We address a key barrier of transcriptome-based diagnostics: the need for source material with disease-representative expression patterns. We establish that blood-based RNA-seq is not adequate for neuromuscular diagnostics, whereas myotubes generated by transdifferentiation from an individual's fibroblasts accurately reflect the muscle transcriptome and faithfully reveal disease-causing mutations. Our work confirms that RNA-seq can greatly improve diagnostic yield in genetically unresolved cases of Mendelian disease, defines strengths and challenges of the technology, and demonstrates the suitability of cell models for RNA-based diagnostics. Our data set the stage for development of RNA-seq as a powerful clinical diagnostic tool that can be applied to the large population of individuals with undiagnosed, rare diseases and provide a framework for establishing minimally invasive strategies for doing so., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: The Personal Genome Project Canada is a comprehensive public data resource that integrates whole genome sequencing data and health information. We describe genomic variation identified in the initial recruitment cohort of 56 volunteers., Methods: Volunteers were screened for eligibility and provided informed consent for open data sharing. Using blood DNA, we performed whole genome sequencing and identified all possible classes of DNA variants. A genetic counsellor explained the implication of the results to each participant., Results: Whole genome sequencing of the first 56 participants identified 207 662 805 sequence variants and 27 494 copy number variations. We analyzed a prioritized disease-associated data set ( n = 1606 variants) according to standardized guidelines, and interpreted 19 variants in 14 participants (25%) as having obvious health implications. Six of these variants (e.g., in BRCA1 or mosaic loss of an X chromosome) were pathogenic or likely pathogenic. Seven were risk factors for cancer, cardiovascular or neurobehavioural conditions. Four other variants - associated with cancer, cardiac or neurodegenerative phenotypes - remained of uncertain significance because of discrepancies among databases. We also identified a large structural chromosome aberration and a likely pathogenic mitochondrial variant. There were 172 recessive disease alleles (e.g., 5 individuals carried mutations for cystic fibrosis). Pharmacogenomics analyses revealed another 3.9 potentially relevant genotypes per individual., Interpretation: Our analyses identified a spectrum of genetic variants with potential health impact in 25% of participants. When also considering recessive alleles and variants with potential pharmacologic relevance, all 56 participants had medically relevant findings. Although access is mostly limited to research, whole genome sequencing can provide specific and novel information with the potential of major impact for health care., Competing Interests: Competing interests: Stephen Scherer serves on the Scientific Advisory Committees of Population Bio and Deep Genomics. Sherilyn Bell, Jo-Anne Herbrick, Jennifer Howe, Ann Joseph-George, Barbara Kellam, Chao Lu, Jeffrey MacDonald, Christian Marshall, Thomas Nalpathamkalam, Rohan Patel, Tara Paton, Giovanna Pellecchia, Sergio Pereira, Miriam Reuter, Stephen Scherer, Lisa Strug, Wilson Sung, Bhooma Thiruvahindrapuram, Susan Walker, Zhuozhi Wang, John Wei, Joe Whitney, Richard Wintle and Ryan Yuen have received grants from Genome Canada/Ontario Genomics; Canada Foundation for Innovation; McLaughlin Centre, University of Toronto; the Government of Ontario, Canadian Institutes of Health Research (CIHR); and the The Hospital for Sick Children Foundation during the conduct of the study. James Ellis, Matthew Hildebrandt, Hin Lee, Peter Pasceri and Wei Wei have received a grant from the McLaughlin Centre, University of Toronto. Daniele Merico is an employee of Deep Genomics. Brett Trost has received a postdoctoral fellowship from CIHR. No other competing interests were declared., (© 2018 Joule Inc. or its licensors.)

Whole-exome sequencing (WES) has increasingly enabled new pathogenic gene variant identification for undiagnosed neurodevelopmental disorders and provided insights into both gene function and disease biology. Here, we describe seven children with a neurodevelopmental disorder characterized by microcephaly, profound developmental delays and/or intellectual disability, cataracts, severe epilepsy including infantile spasms, irritability, failure to thrive, and stereotypic hand movements. Brain imaging in these individuals reveals delay in myelination and cerebral atrophy. We observe an identical recurrent de novo heterozygous c.892C>T (p.Arg298Trp) variant in the nucleus accumbens associated 1 (NACC1) gene in seven affected individuals. One of the seven individuals is mosaic for this variant. NACC1 encodes a transcriptional repressor implicated in gene expression and has not previously been associated with germline disorders. The probability of finding the same missense NACC1 variant by chance in 7 out of 17,228 individuals who underwent WES for diagnoses of neurodevelopmental phenotypes is extremely small and achieves genome-wide significance (p = 1.25 × 10 -14 ). Selective constraint against missense variants in NACC1 makes this excess of an identical missense variant in all seven individuals more remarkable. Our findings are consistent with a germline recurrent mutational hotspot associated with an allele-specific neurodevelopmental phenotype in NACC1., (Copyright © 2017 American Society of Human Genetics. All rights reserved.)

Our increasing knowledge of how genomic variants affect human health and the falling costs of whole-genome sequencing are driving the development of individualized genetic medicine. This new clinical paradigm uses knowledge of an individual's genomic variants to guide health care decisions throughout life, to anticipate, diagnose, and manage disease. While individualized genetic medicine offers the promise of transformative change in health care, it forces us to reconsider existing ethical, scientific, and clinical paradigms. The potential benefits of presymptomatic identification of at risk individuals, improved diagnostics, individualized therapy, accurate prognosis, and avoidance of adverse drug reactions coexist with the potential risks of uninterpretable results, psychological harm, outmoded counseling models, and increased health care costs. Here, we review the challenges of integrating genomic analysis into clinical practice and describe a prototype for implementing genetic medicine. Our multidisciplinary team of bioinformaticians, health economists, ethicists, geneticists, genetic counselors, and clinicians has designed a "Genome Clinic" research project that addresses multiple challenges in genomic medicine-ranging from the development of bioinformatics tools for the clinical assessment of genomic variants and the discovery of disease genes to health policy inquiries, assessment of clinical care models, patient preference, and the ethics of consent., (© 2014 WILEY PERIODICALS, INC.)

Genome sequencing (or whole genome sequencing) is a comprehensive test capable of detecting nearly all DNA variation in a genome. Next-generation sequencing gene panel test: a targeted test focusing on a predefined list of genes that typically detects only exonic sequence-level variants and exon-level deletions or duplications in those genes. Genome sequencing is a comprehensive genetic test that is being integrated into health care systems internationally. For these reasons, genome sequencing will likely eventually supplant exome sequencing, large next-generation sequencing gene panel tests and chromosomal microarray analysis. [Extracted from the article]

Since bi-allelic variants in the PXDN gene were first discovered in 2011 to be associated with anterior segment dysgenesis, a spectrum of ophthalmologic and systemic clinical manifestations has been described. This manuscript reports two distinct clinical phenotypes in monozygotic twin sisters, including the previously unreported ocular manifestation of bilateral primary aphakia, associated with novel compound heterozygous variants in the PXDN gene. We used genome sequencing to study a non-consanguineous family with monozygotic twin sister probands: one presenting with bilateral microphthalmia, primary aphakia, total corneal opacification, congenital glaucoma, and complex systemic comorbidities; the other with anterior persistent fetal vasculature in the right eye, and Peters anomaly type 2 with cataract and iris coloboma in the left eye but no systemic issues. These findings were compared to published reports of PXDN-related ocular diseases upon comprehensive review of prior literature. In both affected sisters, genome sequencing identified two novel heterozygous variants in trans in the PXDN gene: c.1569_1570insT, predicting p.(Thr524TyrfsTer53), and c.3206 C > A, predicting p.(Ala1069Asp), respectively. No other potentially diagnostic variants were identified in any other genes. This report on two novel compound heterozygous variants in the PXDN gene associated with previously unreported clinical manifestations further expands the genotypic and phenotypic spectrum associated with this gene. Our finding of distinctive clinical phenotypes associated with identical compound heterozygous PXDN variants in monozygotic twins emphasizes the significant clinical variability that can occur, suggesting a potential role for stochastic developmental and/or epigenetic factors in the ultimate pathophysiologic pathway. [ABSTRACT FROM AUTHOR]