Congenital long-QT syndrome (LQTS) is a cardiac channelopathy caused by mutations in genes that encode cardiac ion channel subunits. We determined the spectrum of cardiac channel mutations in a cohort of unrelated Southern Italy patients affected by LQTS. METHODS. We screened for LQTS-causing mutations in the KCNQ1, KCNH2, SCN5A, KCNE1 and KCNE2 genes 13 unrelated patients using the polymerase chain reaction, denaturing high-performance liquid chromatography and DNA sequencing. We than expressed two unknown variant Na-channel cDNA mutants, c.4414_4416delAAC and c.C3989A, in HEK 293 cells. The fluorescein-conjugated antibody was used to locate the mutant Na-channels. 
RESULTS. We found 8 disease-causing mutations in the 13 unrelated LQTS families (62%): c.G5350A in SCN5A, c.C1682T in KCNH2, and c.G1573A, c.G1748A and c.G1032A in KCNQ1, which are known mutations; c.4414_4416delAAC and c.C3989A in SCN5A, and c.1450_1467del in KCNH2, which are novel mutations. All mutations co-segregated with the disease in the affected families, except in a child who had no disease signs or symptoms, despite carrying of the c.G5350A mutation in SCN5A gene. Mutation c.G1032A in KCNQ1 gene is a known splice-site mutation that we found in a child of a large family of 39 individuals: 15 of whom carried mutation and presented different clinical symptoms, from border-line QTc values without symptoms to clear long QT with syncope and ventricular arrhythmias, whereas 24 relatives carried the wild type gene, and were asymptomatic. Immunocytochemistry showed that both c.4414_4416delAAC and c.C3989A SCN5A variants are located to the cell surface, as expected for a normally trafficking channel. Functional characterization of these variants and of the other new mutation is underway using the voltage-clamp technique. 
CONCLUSIONS. About 62% of our patients had a mutation: about half of the mutations are novel. Screening of cardiac ion channel genes may: i) facilitate causative analysis at gene level in LQTS patients, and ii) identify carriers of gene mutations with reduced penetrance, thereby reducing the risk of sudden death.

Cardiac ion channel genes analysis in LQTS families of southern Italy revealed eight mutations, including three novel ones

FRISSO, GIULIA
2007

Abstract

Congenital long-QT syndrome (LQTS) is a cardiac channelopathy caused by mutations in genes that encode cardiac ion channel subunits. We determined the spectrum of cardiac channel mutations in a cohort of unrelated Southern Italy patients affected by LQTS. METHODS. We screened for LQTS-causing mutations in the KCNQ1, KCNH2, SCN5A, KCNE1 and KCNE2 genes 13 unrelated patients using the polymerase chain reaction, denaturing high-performance liquid chromatography and DNA sequencing. We than expressed two unknown variant Na-channel cDNA mutants, c.4414_4416delAAC and c.C3989A, in HEK 293 cells. The fluorescein-conjugated antibody was used to locate the mutant Na-channels. 
RESULTS. We found 8 disease-causing mutations in the 13 unrelated LQTS families (62%): c.G5350A in SCN5A, c.C1682T in KCNH2, and c.G1573A, c.G1748A and c.G1032A in KCNQ1, which are known mutations; c.4414_4416delAAC and c.C3989A in SCN5A, and c.1450_1467del in KCNH2, which are novel mutations. All mutations co-segregated with the disease in the affected families, except in a child who had no disease signs or symptoms, despite carrying of the c.G5350A mutation in SCN5A gene. Mutation c.G1032A in KCNQ1 gene is a known splice-site mutation that we found in a child of a large family of 39 individuals: 15 of whom carried mutation and presented different clinical symptoms, from border-line QTc values without symptoms to clear long QT with syncope and ventricular arrhythmias, whereas 24 relatives carried the wild type gene, and were asymptomatic. Immunocytochemistry showed that both c.4414_4416delAAC and c.C3989A SCN5A variants are located to the cell surface, as expected for a normally trafficking channel. Functional characterization of these variants and of the other new mutation is underway using the voltage-clamp technique. 
CONCLUSIONS. About 62% of our patients had a mutation: about half of the mutations are novel. Screening of cardiac ion channel genes may: i) facilitate causative analysis at gene level in LQTS patients, and ii) identify carriers of gene mutations with reduced penetrance, thereby reducing the risk of sudden death.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/341199
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