A sodium-channel mutation causes isolated cardiac conduction disease.
Cardiac conduction disorders slow the heart rhythm and cause disability in millions of people worldwide. Inherited mutations in SCN5A, the gene encoding the human cardiac sodium (Na+) channel, have been associated with rapid heart rhythms that occur suddenly and are life-threatening; however, a chief function of the Na+ channel is to initiate cardiac impulse conduction. Here we provide the first functional characterization of an SCN5A mutation that causes a sustained, isolated conduction defect with pathological slowing of the cardiac rhythm. By analysing the SCN5A coding region, we have identified a single mutation in five affected family members; this mutation results in the substitution of cysteine 514 for glycine (G514C) in the channel protein. Biophysical characterization of the mutant channel shows that there are abnormalities in voltage-dependent 'gating' behaviour that can be partially corrected by dexamethasone, consistent with the salutary effects of glucocorticoids on the clinical phenotype. Computational analysis predicts that the gating defects of G514C selectively slow myocardial conduction, but do not provoke the rapid cardiac arrhythmias associated previously with SCN5A mutations.
The Experimental and Molecular Cardiology Group, Academic Medical Center, University of Amsterdam, The Netherlands.
H L
HL
Tan
M T
MT
Bink-Boelkens
C R
CR
Bezzina
P C
PC
Viswanathan
G C
GC
Beaufort-Krol
P J
PJ
van Tintelen
M P
MP
van den Berg
A A
AA
Wilde
J R
JR
Balser
D000200:Action Potentials; D019943:Amino Acid Substitution; D001145:Arrhythmias, Cardiac / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D003545:Cysteine; D004252:DNA Mutational Analysis; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D005998:Glycine; D006329:Heart Conduction System; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D008959:Models, Neurological; D009154:Mutation; D062554:NAV1.5 Voltage-Gated Sodium Channel; D018807:Polymorphism, Single-Stranded Conformational; D015222:Sodium Channels / Q000187:drug effects / Q000235:genetics* / Q000502:physiology
D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; D015222:Sodium Channels; D003907:Dexamethasone; D003545:Cysteine; D005998:Glycine