title: Exome sequencing and systems biology converge to identify novel mutations in the L-type calcium channel, CACNA1C, linked to autosomal dominant long QT syndrome.
abstract: BACKGROUND
  Long QT syndrome (LQTS) is the most common cardiac channelopathy with 15 elucidated LQTS-susceptibility genes. Approximately 20% of LQTS cases remain genetically elusive.
  
  
  RESULTS
  We combined whole-exome sequencing and bioinformatic/systems biology to identify the pathogenic substrate responsible for nonsyndromic, genotype-negative, autosomal dominant LQTS in a multigenerational pedigree, and we established the spectrum and prevalence of variants in the elucidated gene among a cohort of 102 unrelated patients with "genotype-negative/phenotype-positive" LQTS. Whole-exome sequencing was used on 3 members within a genotype-negative/phenotype-positive family. Genomic triangulation combined with bioinformatic tools and ranking algorithms led to the identification of a CACNA1C mutation. This mutation, Pro857Arg-CACNA1C, cosegregated with the disease within the pedigree, was ranked by 3 disease-network algorithms as the most probable LQTS-susceptibility gene and involves a conserved residue localizing to the proline, gltamic acid, serine, and threonine (PEST) domain in the II-III linker. Functional studies reveal that Pro857Arg-CACNA1C leads to a gain of function with increased ICa,L and increased surface membrane expression of the channel compared to wild type. Subsequent mutational analysis identified 3 additional variants within CACNA1C in our cohort of 102 unrelated cases of genotype-negative/phenotype-positive LQTS. Two of these variants also involve conserved residues within Cav1.2's PEST domain.
  
  
  CONCLUSIONS
  This study provides evidence that coupling whole-exome sequencing and bioinformatic/systems biology is an effective strategy for the identification of potential disease-causing genes/mutations. The identification of a functional CACNA1C mutation cosegregating with disease in a single pedigree suggests that CACNA1C perturbations may underlie autosomal dominant LQTS in the absence of Timothy syndrome.
authors.affiliation: Center for Translational Science Activities, Mayo Graduate School, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Nicole J
authors.initials: NJ
authors.lastname: Boczek
authors.forename: Jabe M
authors.initials: JM
authors.lastname: Best
authors.forename: David J
authors.initials: DJ
authors.lastname: Tester
authors.forename: John R
authors.initials: JR
authors.lastname: Giudicessi
authors.forename: Sumit
authors.initials: S
authors.lastname: Middha
authors.forename: Jared M
authors.initials: JM
authors.lastname: Evans
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Kamp
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
mesh_terms: D000293:Adolescent; D000328:Adult; D001483:Base Sequence; D020746:Calcium Channels, L-Type / Q000235:genetics*; D015331:Cohort Studies; D004252:DNA Mutational Analysis; D059472:Exome; D005260:Female; D005799:Genes, Dominant; D006801:Humans; D008133:Long QT Syndrome / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010375:Pedigree; D055815:Young Adult
chemical_list: C079146:CACNA1C protein, human; D020746:Calcium Channels, L-Type