High frequency of mosaic pathogenic variants in genes causing epilepsy-related neurodevelopmental disorders

Genet Med. 2018 Apr;20(4):403-410. doi: 10.1038/gim.2017.114. Epub 2017 Aug 24.


PurposeMosaicism probably represents an underreported cause of genetic disorders due to detection challenges during routine molecular diagnostics. The purpose of this study was to evaluate the frequency of mosaicism detected by next-generation sequencing in genes associated with epilepsy-related neurodevelopmental disorders.MethodsWe conducted a retrospective analysis of 893 probands with epilepsy who had a multigene epilepsy panel or whole-exome sequencing performed in a clinical diagnostic laboratory and were positive for a pathogenic or likely pathogenic variant in one of nine genes (CDKL5, GABRA1, GABRG2, GRIN2B, KCNQ2, MECP2, PCDH19, SCN1A, or SCN2A). Parental results were available for 395 of these probands.ResultsMosaicism was most common in the CDKL5, PCDH19, SCN2A, and SCN1A genes. Mosaicism was observed in GABRA1, GABRG2, and GRIN2B, which previously have not been reported to have mosaicism, and also in KCNQ2 and MECP2. Parental mosaicism was observed for pathogenic variants in multiple genes including KCNQ2, MECP2, SCN1A, and SCN2A.ConclusionMosaic pathogenic variants were identified frequently in nine genes associated with various neurological conditions. Given the potential clinical ramifications, our findings suggest that next-generation sequencing diagnostic methods may be utilized when testing these genes in a diagnostic laboratory.

MeSH terms

  • Alleles
  • Amino Acid Substitution
  • Epilepsy / diagnosis
  • Epilepsy / genetics*
  • Gene Frequency*
  • Genetic Association Studies
  • Genetic Predisposition to Disease*
  • Genetic Testing
  • Genetic Variation*
  • Genotype
  • High-Throughput Nucleotide Sequencing
  • Humans
  • Mosaicism*
  • Neurodevelopmental Disorders / diagnosis
  • Neurodevelopmental Disorders / genetics*
  • Parents
  • Whole Exome Sequencing