title: Molecular and Functional Characterization of Rare CACNA1C Variants in Sudden Unexplained Death in the Young.
abstract: BACKGROUND
  Perturbations in the CACNA1C-encoded L-type calcium channel α-subunit have been linked recently to heritable arrhythmia syndromes, including Timothy syndrome, Brugada syndrome, early repolarization syndrome, and long QT syndrome. These heritable arrhythmia syndromes may serve as a pathogenic basis for autopsy-negative sudden unexplained death in the young (SUDY). However, the contribution of CACNA1C mutations to SUDY is unknown.
  
  
  OBJECTIVE
  We set out to determine the spectrum, prevalence, and pathophysiology of rare CACNA1C variants in SUDY.
  
  
  METHODS
  Mutational analysis of CACNA1C was conducted in 82 SUDY cases using polymerase chain reaction, denaturing high-performance liquid chromatography, and direct sequencing. Identified variants were engineered using site-directed mutagenesis, and heterologously expressed in TSA-201 or HEK293 cells.
  
  
  RESULTS
  Two SUDY cases (2.4%) harbored functional variants in CACNA1C. The E850del and N2091S variants involve highly conserved residues and localize to the II-III linker and C-terminus, respectively. Although observed in publically available exome databases, both variants confer abnormal CaV1.2 electrophysiological characteristics. Examination of the electrophysiological properties revealed the E850del mutation in CACNA1C led to a 95% loss-of-function in ICa, and the N2091S variant led to a 105% gain-of-function in ICa.Additionally, N2091S led to minor kinetic alterations including a -3.4 mV shift in V1/2of activation.
  
  
  CONCLUSIONS
  This study provides molecular and functional evidence that rare CACNA1C genetic variants may contribute to the underlying pathogenic basis for some cases of SUDY in either a gain or loss-of-function mechanism.
authors.affiliation: Department of Molecular Pharmacology & Experimental Therapeutics, Windland, Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minn, USA.
authors.forename: Brittan S
authors.initials: BS
authors.lastname: Sutphin
authors.affiliation: Department of Molecular Pharmacology & Experimental Therapeutics, Windland, Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minn, USA.
authors.forename: Nicole J
authors.initials: NJ
authors.lastname: Boczek
authors.affiliation: Department of Molecular Genetics, Masonic Medical Research Laboratory, Utica, N.Y., USA.
authors.forename: Héctor
authors.initials: H
authors.lastname: Barajas-Martínez
authors.affiliation: Department of Molecular Genetics, Masonic Medical Research Laboratory, Utica, N.Y., USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Hu
authors.affiliation: Department of Molecular Pharmacology & Experimental Therapeutics, Windland, Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minn, USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Ye
authors.affiliation: Department of Molecular Pharmacology & Experimental Therapeutics, Windland, Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minn, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Tester
authors.affiliation: Department of Molecular Genetics, Masonic Medical Research Laboratory, Utica, N.Y., USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Antzelevitch
authors.affiliation: Department of Molecular Pharmacology & Experimental Therapeutics, Windland, Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minn, USA.|Departments of Medicine (Division of Cardiovascular Diseases) and Pediatrics (Division of Pediatric Cardiology), Mayo Clinic, Rochester, Minn, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000235:genetics* / Q000401:mortality / Q000503:physiopathology; D020746:Calcium Channels, L-Type / Q000235:genetics* / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D016757:Death, Sudden, Cardiac / Q000209:etiology*; D005260:Female; D020022:Genetic Predisposition to Disease; D057809:HEK293 Cells; D006801:Humans; D007223:Infant; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D018408:Patch-Clamp Techniques; D010641:Phenotype; D012307:Risk Factors; D014162:Transfection; D055815:Young Adult
chemical_list: C079146:CACNA1C protein, human; D020746:Calcium Channels, L-Type
keywords: Arrhythmia; CACNA1C; Genetics; Ion Channels; Pediatrics; Sudden Death