LQTS mutation N1325S in cardiac sodium channel gene SCN5A causes cardiomyocyte apoptosis, cardiac fibrosis and contractile dysfunction in mice.
OBJECTIVE
Mutations in the cardiac sodium channel gene SCN5A cause long QT syndrome (LQTS). We previously generated an LQTS mouse model (TG-NS) that overexpresses the LQTS mutation N1325S in SCN5A. The TG-NS mice manifested the clinical features of LQTS including spontaneous VT, syncope and sudden death. However, the long-term prognosis of LQTS on the structure of the heart has not been investigated in this or any other LQTS models and human patients.


RESULTS
Impaired systolic function and reduced left ventricular fractional shortening were detected by echocardiography, morphological and histological examination in two lines of adult mutant transgenic mice. Histological and TUNEL analyses of heart sections revealed fibrosis lesions and increased apoptosis in an age-dependent manner. Cardiomyocyte apoptosis was associated with the increased activation of caspases 3 and 9 in TG-NS hearts. Western blot analysis showed a significantly increased expression of the key Ca(2+) handling proteins L-type Ca(2+) channel, RYR2 and NCX in TG-NS hearts. Increased apoptosis and an altered expression of Ca(2+) handling proteins could be detected as early as 3months of age when echocardiography showed little or no alterations in TG-NS mice.


CONCLUSIONS
Our findings revealed for the first time that the LQTS mutation N1325S in SCN5A causes cardiac fibrosis and contractile dysfunction in mice, possibly through cellular mechanisms involving aberrant cardiomyocyte apoptosis. Therefore, we provide the experimental evidence supporting the notion that some LQTS patients have an increased risk of structural and functional cardiac damage in a prolonged disease course.
Zhang
Teng
T
Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
Yong
Sandro L
SL
Drinko
Jeanne K
JK
Popović
Zoran B
ZB
Shryock
John C
JC
Belardinelli
Luiz
L
Wang
Qing Kenneth
QK
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D004452:Echocardiography; D005354:Fibrosarcoma; D006801:Humans; D008133:Long QT Syndrome / Q000000981:diagnostic imaging / Q000235:genetics / Q000473:pathology; D051379:Mice; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000473:pathology; D032383:Myocytes, Cardiac / Q000473:pathology* / Q000502:physiology*; D062554:NAV1.5 Voltage-Gated Sodium Channel; D017354:Point Mutation; D011379:Prognosis; D015222:Sodium Channels / Q000235:genetics* / Q000378:metabolism; D018754:Ventricular Dysfunction / Q000000981:diagnostic imaging / Q000235:genetics / Q000473:pathology
D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; C568321:Scn5a protein, mouse; D015222:Sodium Channels; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D002118:Calcium