title: Whole Exome Sequencing and Heterologous Cellular Electrophysiology Studies Elucidate a Novel Loss-of-Function Mutation in the CACNA1A-Encoded Neuronal P/Q-Type Calcium Channel in a Child With Congenital Hypotonia and Developmental Delay.
abstract: BACKGROUND
  A 4-year-old boy born at 37 weeks' gestation with intrauterine growth retardation presented with developmental delay with pronounced language and gross motor delay, axial hypotonia, and dynamic hypertonia of the extremities. Investigations including the Minnesota Newborn Screen, thyroid stimulating hormone/thyroxin, and inborn errors of metabolism screening were negative. Cerebral magnetic resonance imaging and spectroscopy were normal. Genetic testing was negative for coagulopathy, Smith-Lemli-Opitz, fragile X, and Prader-Willi/Angelman syndromes. Whole genome array analysis was unremarkable.
  
  
  METHODS
  Whole exome sequencing was performed through a commercial testing laboratory to elucidate the underlying etiology for the child's presentation. A de novo mutation was hypothesized. In attempt to establish pathogenicity of our candidate variant, cellular electrophysiologic functional analysis of the putative de novo mutation was performed using patch-clamp technology.
  
  
  RESULTS
  Whole exome sequencing revealed a p.P1353L variant in the CACNA1A gene, which encodes for the α1-subunit of the brain-specific P/Q-type calcium channel (CaV2.1). This presynaptic high-voltage-gated channel couples neuronal excitation to the vesicular release of neurotransmitter and is implicated in several neurologic disorders. DNA Sanger sequencing confirmed that the de novo mutation was absent in both parents and present in the child only. Electrophysiologic analysis of P1353L-CACNA1A demonstrated near complete loss of function, with a 95% reduction in peak current density.
  
  
  CONCLUSIONS
  Whole exome sequencing coupled with cellular electrophysiologic functional analysis of a de novoCACNA1A missense mutation has elucidated the probable underlying pathophysiologic mechanism responsible for the child's phenotype. Genetic testing of CACNA1A in patients with congenital hypotonia and developmental delay may be warranted.
authors.affiliation: Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: Derek L
authors.initials: DL
authors.lastname: Weyhrauch
authors.affiliation: Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: Dan
authors.initials: D
authors.lastname: Ye
authors.affiliation: Department of Health Science Research, Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: Nicole J
authors.initials: NJ
authors.lastname: Boczek
authors.affiliation: Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: David J
authors.initials: DJ
authors.lastname: Tester
authors.affiliation: Department of Medical Genetics, Mayo Clinic, Rochester, Minnesota; Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Ralitza H
authors.initials: RH
authors.lastname: Gavrilova
authors.affiliation: Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota; Department of Medical Genetics, Mayo Clinic, Rochester, Minnesota; Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Marc C
authors.initials: MC
authors.lastname: Patterson
authors.affiliation: Department of Medical Genetics, Mayo Clinic, Rochester, Minnesota; Departments of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Wieben
authors.affiliation: Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota; Department of Pediatric and Adolescent Medicine (Division of Pediatric Cardiology), Mayo Clinic, Rochester, Minnesota; Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota. Electronic address: ackerman.michael@mayo.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
mesh_terms: D015220:Calcium Channels / Q000235:genetics*; D002675:Child, Preschool; D002658:Developmental Disabilities / Q000235:genetics*; D059472:Exome / Q000235:genetics*; D006801:Humans; D008297:Male; D009123:Muscle Hypotonia / Q000151:congenital / Q000235:genetics*; D020125:Mutation, Missense; D018408:Patch-Clamp Techniques; D020864:Calcium Channels, N-Type
chemical_list: D015220:Calcium Channels; C105656:CACNA1A protein, human; D020864:Calcium Channels, N-Type
keywords: CACNA1A; P/Q-type calcium channel; congenital hypotonia; developmental delay; genetics; whole exome sequencing