Cardiac Channelopathies Associated with Infantile Fatal Ventricular Arrhythmias: From the Cradle to the Bench
Drs. Kato and Makiyama contributed equally to this work.
This work was supported by research grants from the Ministry of Education, Culture, Science, and Technology of Japan, health science research grants from the Ministry of Health, Labor and Welfare of Japan for Clinical Research on Measures for Intractable Diseases, the Translational Research Funds from the Japan Circulation Society (to MH), and a grant from the National Natural Science Foundation of China (#81273501 to JW).
Channelopathies in Infantile Arrhythmias
Fatal ventricular arrhythmias in the early period of life have been associated with cardiac channelopathies for decades, and postmortem analyses in SIDS victims have provided evidence of this association. However, the prevalence and functional properties of cardiac ion channel mutations in infantile fatal arrhythmia cases are not clear.
Methods and Results
Seven infants with potentially lethal arrhythmias at age < 1 year (5 males, age of onset 44.1 ± 72.1 days) were genetically analyzed for KCNQ1, KCNH2, KCNE1–5, KCNJ2, SCN5A, GJA5, and CALM1 by using denaturing high-performance liquid chromatography and direct sequencing. Whole-cell currents of wildtype and mutant channels were recorded and analyzed in Chinese hamster ovary cells transfected with SCN5A and KCNH2 cDNA. In 5 of 7 patients, we identified 4 mutations (p.N1774D, p.T290fsX53, p.F1486del and p.N406K) in SCN5A, and 1 mutation (p.G628D) in KCNH2. N1774D, F1486del, and N406K in SCN5A displayed tetrodotoxin-sensitive persistent late Na+ currents. By contrast, SCN5A-T290fsX53 was nonfunctional. KCNH2-G628D exhibited loss of channel function.
Genetic screening of 7 patients was used to demonstrate the high prevalence of cardiac channelopathies. Functional assays revealed both gain and loss of channel function in SCN5A mutations, as well as loss of function associated with the KCNH2 mutation.