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Novel long QT syndrome-associated missense mutation, L762F, in CACNA1C-encoded L-type calcium channel imparts a slower inactivation tau and increased sustained and window current.

ABSTRACT: BACKGROUND:Mutations in the CACNA1C-encoded L-type calcium channel have been associated with Timothy syndrome (TS) with severe QT prolongation, syndactyly, facial dysmorphisms, developmental delay, and sudden death. Recently, patients hosting CACNA1C mutations with only long QT syndrome (LQTS) have been described. We sought to identify novel variants in CACNA1C associated with either TS or LQTS, and to determine the impact of the mutation on channel function. METHODS/RESULTS:Two probands were identified with mutations in CACNA1C, one with a TS-associated mutation, G406R, and a second with genotype-negative LQTS. Illumina HiSeq 2000 whole exome sequencing on the genotype-negative LQTS proband revealed a novel variant, CACNA1C-L762F, that co-segregated within a multi-generational family. The missense mutation localized to the DII/DIII intracellular interlinker segment of the channel in a highly conserved region in close proximity to the 6th transmembrane segment of domain II (DIIS6). Whole cell patch clamp of heterologously expressed CACNA1C-L762F in TSA201 cells demonstrated slower inactivation tau and increased sustained and window current. Comprehensive review and topological mapping of all described CACNA1C mutations revealed TS-specific hotspots localizing to the cytoplasmic aspect of 6th transmembrane segment of respective domains. Probands hosting TS mutations were associated with elevated QTc, higher prevalence of 2:1 AV block, and a younger age at presentation compared to LQTS. CONCLUSIONS:The CACNA1C-L762F mutation is associated with development of LQTS through slower channel inactivation and increased sustained and window current. TS-associated mutations localize to specific areas of CACNA1C and are associated with a younger age at presentation, higher QTc, and 2:1 AV block than isolated LQTS-associated mutations.

SUBMITTER: Landstrom AP

PROVIDER: S-EPMC6311393 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Novel long QT syndrome-associated missense mutation, L762F, in CACNA1C-encoded L-type calcium channel imparts a slower inactivation tau and increased sustained and window current.

Landstrom Andrew P AP Boczek Nicole J NJ Ye Dan D Miyake Christina Y CY De la Uz Caridad M CM Allen Hugh D HD Ackerman Michael J MJ Kim Jeffrey J JJ

International journal of cardiology 20160623

<h4>Background</h4>Mutations in the CACNA1C-encoded L-type calcium channel have been associated with Timothy syndrome (TS) with severe QT prolongation, syndactyly, facial dysmorphisms, developmental delay, and sudden death. Recently, patients hosting CACNA1C mutations with only long QT syndrome (LQTS) have been described. We sought to identify novel variants in CACNA1C associated with either TS or LQTS, and to determine the impact of the mutation on channel function.<h4>Methods/results</h4>Two p ...[more]

PMID: 27390944

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Project description:Mutations in CACNA1C that increase current through the CaV1.2 L-type Ca2+ channel underlie rare forms of long QT syndrome (LQTS), and Timothy syndrome (TS). We identified a variant in CACNA1C in a male child of Filipino descent with arrhythmias and extracardiac features by candidate gene sequencing and performed functional expression studies to electrophysiologically characterize the effects of the variant on CaV1.2 channels. As a baby, the subject developed seizures and displayed developmental delays at 30 months of age. At age 5 years, he displayed a QTc of 520 ms and experienced recurrent VT. Physical exam at 17 years of age was notable for microcephaly, short stature, lower extremity weakness and atrophy with hyperreflexia, spastic diplegia, multiple dental caries and episodes of rhabdomyolysis. Candidate gene sequencing identified a G>C transversion at position 5731 of CACNA1C (rs374528680) predicting a glycine>arginine substitution at residue 1911 (p.G1911R) of CaV1.2. The allele frequency of this variant is 0.01 in Malays, but absent in 984 Caucasian alleles and in the 1000 genomes project. In electrophysiological analyses, the variant decreased voltage-dependent inactivation, thus causing a gain of function of CaV1.2. We also observed a negative shift of V1/2 of activation and positive shift of V1/2 of channel inactivation, resulting in an increase of the window current. Together, these suggest a gain-of-function effect on CaV1.2 and suggest increased susceptibility for arrhythmias in certain clinical settings. The p.G1911R variant was also identified in a case of sudden unexplained infant death (SUID), for which an increasing number of clinical observations have demonstrated can be associated with arrhythmogenic mutations in cardiac ion channels. In summary, the combined effects of the CACNA1C variant to diminish voltage-dependent inactivation of CaV1.2 and increase window current expand our appreciation of mechanisms by which a gain of function of CaV1.2 can contribute to QT prolongation.

Dataset Information

Novel long QT syndrome-associated missense mutation, L762F, in CACNA1C-encoded L-type calcium channel imparts a slower inactivation tau and increased sustained and window current.

Publications

Novel long QT syndrome-associated missense mutation, L762F, in CACNA1C-encoded L-type calcium channel imparts a slower inactivation tau and increased sustained and window current.

Similar Datasets

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