Publications by authors named "Johan T Den Dunnen"

Background: The Human Genome Variation Society (HGVS) Nomenclature is the global standard for describing and communicating variants in DNA, RNA, and protein sequences in clinical and research genomics. This manuscript details recent updates to the HGVS Nomenclature, highlighting improvements in governance, community engagement, website functionality, and underlying implementation of the standard.

Methods: The HGVS Variant Nomenclature Committee (HVNC) now operates under the Human Genome Organization (HUGO), facilitating broader community feedback and collaboration with related standards organizations.

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  • A study compared the ABC and ACMG variant classification systems using 10 challenging cases, involving 43 European clinical laboratories, to determine how each system influences variant reporting and clinical utility.
  • Although the ACMG system is primarily for assessing pathogenicity rather than reporting, it still affects reporting in many labs, leading to some noted differences in how variants are classified and communicated.
  • The comparison revealed that ABC-based classifications tend to be clearer and more adaptable to clinical questions, allowing for more context-appropriate reporting of variants, unlike ACMG which can mislabel variants in certain clinical scenarios.
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  • The study focused on improving the classification of genetic variants linked to familial adenomatous polyposis using APC-specific criteria developed by an expert panel.
  • A total of 10,228 unique variants were analyzed, resulting in 41% of VUS from ClinVar and 61% from LOVD being reclassified, primarily as (Likely) Benign, which reduced the overall VUS by 37%.
  • The research highlighted a systematic approach to variant classification in large datasets that could be applied to other gene/disease interpretations and allowed for prioritization of VUS requiring further evidence collection.
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Leukocyte adhesion deficiency (LAD) is an immunodeficiency caused by defects in the adhesion of leukocytes (especially neutrophils) to the blood vessel wall. As a result, patients with LAD suffer from severe bacterial infections and impaired wound healing, accompanied by neutrophilia. In LAD-I, characterized directly after birth by delayed separation of the umbilical cord, mutations are found in ITGB2, the gene that encodes the β subunit (CD18) of the β integrins.

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The journal Human Mutation has as its principal focus variants in the human genome, covering the entire spectrum from methods used to detect variants, to ways of answering the ultimate question: "What are the consequences of carrying a variant for the health of the individual?" This comprehensive collection of articles provides an excellent perspective of the advancements in variant effect prediction in recent years, as well as some caveats and cautions in this developing field. We believe that this resource will help to drive further evolution of the variant effect prediction process toward more robust understanding of genotype-phenotype relationships through reliable variant classification.

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While in most patients the identification of genetic alterations causing dystrophinopathies is a relatively straightforward task, a significant number require genomic and transcriptomic approaches that go beyond a routine diagnostic set-up. In this work, we present a Becker Muscular Dystrophy patient with elevated creatinine kinase levels, progressive muscle weakness, mild intellectual disability and a muscle biopsy showing dystrophic features and irregular dystrophin labelling. Routine molecular techniques (Southern-blot analysis, multiplex PCR, MLPA and genomic DNA sequencing) failed to detect a defect in the gene.

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Pathogenic variants of the nuclear receptor subfamily 2 group F member 1 gene (NR2F1) are responsible for Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS), an autosomal dominant disorder characterized by optic atrophy associated with developmental delay and intellectual disability, but with a clinical presentation which appears to be multifaceted. We created the first public locus-specific database dedicated to NR2F1. All variants and clinical cases reported in the literature, as well as new unpublished cases, were integrated into the database using standard nomenclature to describe both molecular and phenotypic anomalies.

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Background: Auriculocondylar syndrome (ARCND) is a rare genetic disease that affects structures derived from the first and second pharyngeal arches, mainly resulting in micrognathia and auricular malformations. To date, pathogenic variants have been identified in three genes involved in the EDN1-DLX5/6 pathway (, and ) and some cases remain unsolved. Here we studied a large unsolved four-generation family.

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The European Society of Human Genetics (ESHG) was founded in 1967 as a professional organisation for members working in genetics in clinical practice, research and education. The Society seeks the integration of scientific research and its implementation into clinical practice and the education of specialists and the public in all areas of medical and human genetics. The Society works to do this through many approaches, including educational sessions at the annual conference; training courses in general and specialist areas of genetics; an online resource of educational materials (EuroGEMS); and a mentorship scheme.

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Gene variant databases are the backbone of DNA-based diagnostics. These databases, also called Locus-Specific DataBases (LSDBs), store information on variants in the human genome and the observed phenotypic consequences. The largest collection of public databases uses the free, open-source LOVD software platform.

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Article Synopsis
  • The text discusses a frequently mutated gene associated with intellectual disability, noting that about 1% of cases involve this gene's variants, which are often classified as pathogenic due to their expected loss-of-function effects.
  • It highlights the complexity of interpreting familial loss-of-function variants, as they may have variable effects, with some leading to mild symptoms in parents or being benign based on the gene's specific regions.
  • The study includes 12 families with challenging variants but successfully classifies most through clinical and DNA methylation studies, providing new insights and suggesting updates to the ACMG guidelines for better interpretation of these genetic variants.
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Pathogenic variants of the aconitase 2 gene (ACO2) are responsible for a broad clinical spectrum involving optic nerve degeneration, ranging from isolated optic neuropathy with recessive or dominant inheritance, to complex neurodegenerative syndromes with recessive transmission. We created the first public locus-specific database (LSDB) dedicated to ACO2 within the "Global Variome shared LOVD" using exclusively the Human Phenotype Ontology (HPO), a standard vocabulary for describing phenotypic abnormalities. All the variants and clinical cases listed in the literature were incorporated into the database, from which we produced a dataset.

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Article Synopsis
  • - The ACMG-AMP system classifies genetic variants into five categories: benign, likely benign, VUS, likely pathogenic, and pathogenic, while the new ABC classification model offers an alternative that focuses first on functional assessment and then on clinical relevance.
  • - The ABC system grades variants on two levels: functional (A) and clinical (B), each with a scoring range of 1-5, or a "zero" for insufficient knowledge, and combines these to create a comprehensive classification from A to F.
  • - By distinguishing VUS into two subcategories and linking classifications to standardized comments, the ABC system aims to provide clinicians with clearer insights on variant significance and better guidance for reporting.
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Duchenne Muscular Dystrophy (DMD) is a lethal progressive muscle-wasting disease. New treatment strategies relying on DMD gene exon-skipping therapy have recently been approved and about 30% of patients could be amenable to exon 51, 53 or 45 skipping. We evaluated the spectrum of deletions reported in DMD registries, and designed a method to screen newborns and identify DMD deletions amenable to exon 51, 53 and 45 skipping.

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Motivation: Unambiguous variant descriptions are of utmost importance in clinical genetic diagnostics, scientific literature and genetic databases. The Human Genome Variation Society (HGVS) publishes a comprehensive set of guidelines on how variants should be correctly and unambiguously described. We present the implementation of the Mutalyzer 2 tool suite, designed to automatically apply the HGVS guidelines so users do not have to deal with the HGVS intricacies explicitly to check and correct their variant descriptions.

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One application of personalized medicine is the tailoring of medication to the individual, so that the medication will have the highest chance of success. In order to individualize medication, one must have a complete inventory of all current pharmaceutical compounds (a detailed formulary) combined with pharmacogenetic datasets, the genetic makeup of the patient, their (medical) family history and other health-related data. For healthcare professionals to make the best use of this information, it must be visualized in a way that makes the most medically relevant data accessible for their decision-making.

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Documenting variation in our genomes is important for research and clinical care. Accuracy in the description of DNA variants is therefore essential. To address this issue, the Human Variome Project convened a committee to evaluate the feasibility of requiring authors to verify that all variants submitted for publication complied with a widely accepted standard for description.

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Background: The dysfunction of OPA1, a dynamin GTPase involved in mitochondrial fusion, is responsible for a large spectrum of neurological disorders, each of which includes optic neuropathy. The database dedicated to OPA1 ( https://www.lovd.

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Each year diagnostic laboratories in the Netherlands profile thousands of individuals for heritable disease using next-generation sequencing (NGS). This requires pathogenicity classification of millions of DNA variants on the standard 5-tier scale. To reduce time spent on data interpretation and increase data quality and reliability, the nine Dutch labs decided to publicly share their classifications.

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Variations in the DMD gene that affect dystrophin production underlie both the severe Duchenne and the milder Becker muscular dystrophies (DMD and BMD, respectively). Depending on their location, deletions and duplications involving one or more exons of a gene can have a range of consequences. This overview, summarizing the important points to consider, was drafted in response to frequent questions we receive about deletions/duplications involving the dystrophin encoding DMD gene.

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A recognized source of disease-causing genome alterations is erroneous repair of broken chromosomes, which can be executed by two distinct mechanisms: non-homologous end joining (NHEJ) and the recently discovered polymerase theta-mediated end joining (TMEJ) pathway. While TMEJ has previously been considered to act as an alternative mechanism backing up NHEJ, recent work points to a role for TMEJ in the repair of replication-associated DNA breaks that are excluded from repair through homologous recombination. Because of its mode of action, TMEJ is intrinsically mutagenic and sometimes leaves behind a recognizable genomic scar when joining chromosome break ends (i.

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The BRCA Challenge is a long-term data-sharing project initiated within the Global Alliance for Genomics and Health (GA4GH) to aggregate BRCA1 and BRCA2 data to support highly collaborative research activities. Its goal is to generate an informed and current understanding of the impact of genetic variation on cancer risk across the iconic cancer predisposition genes, BRCA1 and BRCA2. Initially, reported variants in BRCA1 and BRCA2 available from public databases were integrated into a single, newly created site, www.

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