title: High throughput exome coverage of clinically relevant cardiac genes.
abstract: BACKGROUND
  Given the growing use of whole-exome sequencing (WES) for clinical diagnostics of complex human disorders, we evaluated coverage of clinically relevant cardiac genes on WES and factors influencing uniformity and depth of coverage of exonic regions.
  
  
  METHODS
  Two hundred and thirteen human DNA samples were exome sequenced via Illumina HiSeq using different versions of the Agilent SureSelect capture kit. 50 cardiac genes were further analyzed including 31 genes from the American College of Medical Genetics (ACMG) list for reporting of incidental findings and 19 genes associated with congenital heart disease for which clinical testing is available. Gene coordinates were obtained from two databases, CCDS and Known Gene and compared. Read depth for each region was extracted from the exomes and used to assess capture variability between kits for individual genes, and for overall coverage. GC content, gene size, and inter-sample variability were also tested as potential contributors to variability in gene coverage.
  
  
  RESULTS
  All versions of capture kits (designed based on Consensus coding sequence) included only 55% of known genomic regions for the cardiac genes. Although newer versions of each Agilent kit showed improvement in capture of CCDS regions to 99%, only 64% of Known Gene regions were captured even with newer capture kits. There was considerable variability in coverage of the cardiac genes. 10 of the 50 genes including 6 on the ACMG list had less than the optimal coverage of 30X. Within each gene, only 32 of the 50 genes had the majority of their bases covered at an interquartile range ≥30X. Heterogeneity in gene coverage was modestly associated with gene size and significantly associated with GC content.
  
  
  CONCLUSIONS
  Despite improvement in overall coverage across the exome with newer capture kit versions and higher sequencing depths, only 50% of known genomic regions of clinical cardiac genes are targeted and individual gene coverage is non-uniform. This may contribute to a bias with greater attribution of disease causation to mutations in well-represented and well-covered genes. Improvements in WES technology are needed before widespread clinical application.
authors.affiliation: Division of Cardiology, Department of Pediatrics, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. dorin.manase@sickkids.ca.|Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada. dorin.manase@sickkids.ca.
authors.forename: Dorin
authors.initials: D
authors.lastname: Manase
authors.affiliation: Division of Cardiology, Department of Pediatrics, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. lisac.dalessandro@sickkids.ca.|Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada. lisac.dalessandro@sickkids.ca.
authors.forename: Lisa C A
authors.initials: LC
authors.lastname: D'Alessandro
authors.affiliation: Division of Cardiology, Department of Pediatrics, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. ashokkumar.manickaraj@sickkids.ca.|Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada. ashokkumar.manickaraj@sickkids.ca.
authors.forename: Ashok Kumar
authors.initials: AK
authors.lastname: Manickaraj
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton, UK. sa9@sanger.ac.uk.
authors.forename: Saeed
authors.initials: S
authors.lastname: Al Turki
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton, UK. meh@sanger.ac.uk.
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Hurles
authors.affiliation: Division of Cardiology, Department of Pediatrics, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. seema.mital@sickkids.ca.|Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada. seema.mital@sickkids.ca.
authors.forename: Seema
authors.initials: S
authors.lastname: Mital
mesh_terms: D000293:Adolescent; D001482:Base Composition; D015415:Biomarkers / Q000378:metabolism*; D016022:Case-Control Studies; D066264:Datasets as Topic; D059472:Exome / Q000235:genetics*; D005260:Female; D015894:Genome, Human; D006330:Heart Defects, Congenital / Q000175:diagnosis / Q000235:genetics*; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods*; D006801:Humans; D008297:Male; D011446:Prospective Studies
chemical_list: D015415:Biomarkers