Diagnostic implications of genetic copy number variation in epilepsy plus
- PMID: 30866059
- PMCID: PMC6488157
- DOI: 10.1111/epi.14683
Diagnostic implications of genetic copy number variation in epilepsy plus
Abstract
Objective: Copy number variations (CNVs) represent a significant genetic risk for several neurodevelopmental disorders including epilepsy. As knowledge increases, reanalysis of existing data is essential. Reliable estimates of the contribution of CNVs to epilepsies from sizeable populations are not available.
Methods: We assembled a cohort of 1255 patients with preexisting array comparative genomic hybridization or single nucleotide polymorphism array based CNV data. All patients had "epilepsy plus," defined as epilepsy with comorbid features, including intellectual disability, psychiatric symptoms, and other neurological and nonneurological features. CNV classification was conducted using a systematic filtering workflow adapted to epilepsy.
Results: Of 1097 patients remaining after genetic data quality control, 120 individuals (10.9%) carried at least one autosomal CNV classified as pathogenic; 19 individuals (1.7%) carried at least one autosomal CNV classified as possibly pathogenic. Eleven patients (1%) carried more than one (possibly) pathogenic CNV. We identified CNVs covering recently reported (HNRNPU) or emerging (RORB) epilepsy genes, and further delineated the phenotype associated with mutations of these genes. Additional novel epilepsy candidate genes emerge from our study. Comparing phenotypic features of pathogenic CNV carriers to those of noncarriers of pathogenic CNVs, we show that patients with nonneurological comorbidities, especially dysmorphism, were more likely to carry pathogenic CNVs (odds ratio = 4.09, confidence interval = 2.51-6.68; P = 2.34 × 10-9 ). Meta-analysis including data from published control groups showed that the presence or absence of epilepsy did not affect the detected frequency of CNVs.
Significance: The use of a specifically adapted workflow enabled identification of pathogenic autosomal CNVs in 10.9% of patients with epilepsy plus, which rose to 12.7% when we also considered possibly pathogenic CNVs. Our data indicate that epilepsy with comorbid features should be considered an indication for patients to be selected for a diagnostic algorithm including CNV detection. Collaborative large-scale CNV reanalysis leads to novel declaration of pathogenicity in unexplained cases and can promote discovery of promising candidate epilepsy genes.
Keywords: SNP array; array CGH; copy number variants; epilepsy genes.
© 2019 The Authors. Epilepsia published by Wiley Periodicals, Inc. on behalf of International League Against Epilepsy.
Conflict of interest statement
A.C. has received honoraria from Eisai for participating in on an advisory board and as a speaker. B.C. has received honoraria for consulting and advisory board services from Brabant Pharma, Zogenix, and Novartis. J.H.C. is involved in clinical trials for GW Pharma and Zogenix; has received research grants from Vitaflo, NIHR, Action Medical Research, SPARKS, and the European Union; has been part of advisory boards for Takeda, Shire, UCB, and Eisai; and has given lectures for Shire and Zogenix; all honoraria and funds were given to the department. L.L. has received honoraria from Zogenix, Livanova, Shire, Takeda, UCB, and Novartis. P.S. has received speaker honoraria and travel grants from Eisai, Kolfarma, FB Health, and Zogenix. C.M. is an associate editor of
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References
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- Thomas RH, Berkovic SF. The hidden genetics of epilepsy—a clinically important new paradigm. Nat Rev Neurol. 2014;10:283–92. - PubMed
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- Striano P, Coppola A, Paravidino R, et al. Clinical significance of rare copy number variations in epilepsy: a case‐control survey using microarray‐based comparative genomic hybridization. Arch Neurol. 2012;69(3):322–30. - PubMed
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