Cardiac sodium channel dysfunction in sudden infant death syndrome

• Published in: Circulation (New York, N.Y.) N.Y.), 2007-01, Vol.115 (3), p.368-376
• Main Authors: WANG, Dao W, DESAI, Reshma R, GEORGE, Alfred L, CROTTI, Lia, ARNESTAD, Marianne, INSOLIA, Roberto, PEDRAZZINI, Matteo, FERRANDI, Chiara, VEGE, Ashild, ROGNUM, Torleiv, SCHWARTZ, Peter J
• Format: Article
• Language: English
• Subjects: Alleles; Arrhythmias, Cardiac - complications; Arrhythmias, Cardiac - genetics; Arrhythmias, Cardiac - physiopathology; Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Cohort Studies; Diseases of the peripheral vessels. Diseases of the vena cava. Miscellaneous; DNA, Complementary - genetics; Electrocardiography; Electrophysiology; Gene Expression Regulation; Genetic Predisposition to Disease; Genetic Testing - methods; Genetic Variation - genetics; Humans; Infant; Injuries of the limb. Injuries of the spine; Long QT Syndrome - complications; Long QT Syndrome - genetics; Long QT Syndrome - physiopathology; Mathematics; Medical sciences; Muscle Proteins - genetics; Muscle Proteins - physiology; Mutation, Missense - genetics; NAV1.5 Voltage-Gated Sodium Channel; Norway; Phenotype; Risk Factors; Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis; Sodium Channels - genetics; Sodium Channels - physiology; Sudden Infant Death - etiology; Sudden Infant Death - genetics; Traumas. Diseases due to physical agents
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/CIRCULATIONAHA.106.646513

Mutations in genes responsible for the congenital long-QT syndrome, especially SCN5A, have been identified in some cases of sudden infant death syndrome. In a large-scale collaborative genetic screen, several SCN5A variants were identified in a Norwegian sudden infant death syndrome cohort (n=201). We present functional characterization of 7 missense variants (S216L, R680H, T1304M, F1486L, V1951L, F2004L, and P2006A) and 1 in-frame deletion allele (delAL586-587) identified by these efforts. Whole-cell sodium currents were measured in tsA201 cells transiently transfected with recombinant wild-type or mutant SCN5A cDNA (hH1) coexpressed with the human beta1 subunit. All variants exhibited defects in the kinetics and voltage dependence of inactivation. Five variants (S216L, T1304M, F1486L, F2004L, and P2006A) exhibited significantly increased persistent sodium currents (range, 0.5% to 1.7% of peak current) typical of SCN5A mutations associated with long-QT syndrome. These same 5 variants also displayed significant depolarizing shifts in voltage dependence of inactivation (range, 5 to 14 mV) and faster recovery from inactivation, but F1486L uniquely exhibits a depolarizing shift in the conductance-voltage relationship. Three alleles (delAL586-587, R680H, and V1951L) exhibited increased persistent current only under conditions of internal acidosis (R680H) or when expressed in the context of a common splice variant (delQ1077), indicating that they have a latent dysfunctional phenotype. Our present results greatly expand the spectrum of functionally characterized SCN5A variants associated with sudden infant death syndrome and provide further biophysical correlates of arrhythmia susceptibility in this syndrome.