CNV

CNV
Name	CNV
Caption	Copy-number variation schematic
Field	Genetics
Discovered	2004
Genes	Variable
Disorders	Multiple

CNV

Copy-number variation refers to segments of DNA that vary in copy number between individuals and populations. It encompasses deletions, duplications, insertions, and complex multi-allelic rearrangements affecting genomic segments typically from kilobases to megabases in length. CNV contributes to human phenotypic diversity and disease susceptibility and is studied across projects and institutions using genomic technologies.

Definition and Nomenclature

CNV terminology arose during large-scale surveys such as those by the Human Genome Project, 1000 Genomes Project, HapMap Project, and early reports from the Wellcome Trust Sanger Institute and Broad Institute. Terms commonly used include "deletion", "duplication", "gain", "loss", "multiallelic CNV", and "structural variant" as defined by groups like the American College of Medical Genetics and Genomics and the Genome Reference Consortium. Nomenclature guidelines are influenced by standards set by the Human Genome Variation Society and databases such as ClinVar and DECIPHER. Classification often references cytogenetic bands used by the National Center for Biotechnology Information and coordinates in assemblies maintained by the Ensembl and UCSC Genome Browser projects.

Mechanisms and Formation

CNVs arise through molecular mechanisms characterized by research from teams at institutions including the National Institutes of Health, Max Planck Society, and Cold Spring Harbor Laboratory. Recurrent CNVs often reflect nonallelic homologous recombination mediated by segmental duplications first cataloged by the Database of Genomic Variants and described in studies from the McGill University and University of Washington. Nonrecurrent CNVs can result from mechanisms such as fork stalling and template switching (FoSTeS) and microhomology-mediated break-induced replication (MMBIR) investigated at the Salk Institute and European Molecular Biology Laboratory. Retrotransposition events studied by the Howard Hughes Medical Institute and end-joining pathways researched at the Francis Crick Institute also contribute to CNV formation.

Detection and Measurement Techniques

Technologies from companies and consortia including Affymetrix, Illumina, Oxford Nanopore Technologies, and Pacific Biosciences underpin CNV detection. Array comparative genomic hybridization (aCGH) developed at the Whitehead Institute and single nucleotide polymorphism arrays from Perlegen Sciences enabled early surveys. Short-read sequencing pipelines used by the Broad Institute and long-read sequencing approaches pioneered by PacBio and Oxford Nanopore give differing sensitivity for breakpoint resolution. Optical mapping platforms commercialized by Bionano Genomics and linked-read methods introduced by 10x Genomics are applied in clinical and research settings at centers like Mayo Clinic and Johns Hopkins University Hospital. Bioinformatic tools and standards from the Global Alliance for Genomics and Health and software produced by groups such as those at University of California, Santa Cruz perform CNV calling, genotyping, and annotation.

Clinical Significance and Disease Associations

Associations between CNV and disorders have been demonstrated by consortia including the Psychiatric Genomics Consortium, Deciphering Developmental Disorders study, and cancer genome projects at the International Cancer Genome Consortium. Recurrent CNVs involving loci such as 22q11.2, 16p11.2, and 1q21.1 are linked to syndromes catalogued in OMIM and reported by clinical centers like Great Ormond Street Hospital and Boston Children’s Hospital. CNV burden and specific large-effect events have been implicated in neurodevelopmental disorders studied by teams at King’s College London and Massachusetts General Hospital, while somatic CNVs drive oncogenesis characterized in studies at Memorial Sloan Kettering Cancer Center and Dana-Farber Cancer Institute. Pharmacogenomic implications have been explored at St. Jude Children’s Research Hospital and regulatory assessments referenced by agencies such as the Food and Drug Administration.

Population Genetics and Evolutionary Impact

Population-scale surveys by the 1000 Genomes Project, GenomeAsia 100K project, and regional efforts at the African Genome Variation Project and Icelandic deCODE genetics reveal CNV frequency spectra across populations studied by teams at University of Cambridge and Seoul National University. Balancing selection, positive selection, and drift shaping CNV distributions have been inferred in analyses published by researchers at Princeton University and Stanford University. Adaptive CNVs affecting immune loci, metabolic genes, and olfactory receptor repertoires have been reported in comparative genomics work involving data from the Primate Genome Project and collaborations with the Smithsonian Institution.

Interpretation, Reporting, and Guidelines

Clinical interpretation frameworks rely on recommendations from the American College of Medical Genetics and Genomics, the European Society of Human Genetics, and expert panels convened by the Clinical Genome Resource (ClinGen). Reporting practices implemented at diagnostic laboratories such as those at Mayo Clinic Laboratories and hospital networks follow criteria for pathogenicity, incidence, inheritance, and dosage sensitivity catalogued in ClinGen Dosage Sensitivity Map and ClinVar. Consent, data sharing, and ethical oversight are guided by policies from organizations including the World Health Organization, National Human Genome Research Institute, and regional bodies like the European Medicines Agency.

Category:Genetics