Sudden infant death syndrome in mice with an inherited mutation in RyR2.
BACKGROUND
Mutations in the cardiac ryanodine receptor gene (RyR2) have been recently identified in victims of sudden infant death syndrome. The aim of this study was to determine whether a gain-of-function mutation in RyR2 increases the propensity to cardiac arrhythmias and sudden death in young mice.


RESULTS
Incidence of sudden death was monitored prospectively in heterozygous knock-in mice with mutation R176Q in RyR2 (R176Q/+). Young R176Q/+ mice exhibited a higher incidence of sudden death compared with wild-type littermates. Optical mapping of membrane potentials and intracellular calcium in 1- to 7-day-old R176Q/+ and wild-type mice revealed an increased incidence of ventricular ectopy and spontaneous calcium releases in neonatal R176Q/+ mice. Surface ECGs in 3- to 10-day-old mice showed that R176Q/+ mice developed more ventricular arrhythmias after provocation with epinephrine and caffeine. Intracardiac pacing studies in 12- to 18-day-old mice revealed the presence of an arrhythmogenic substrate in R176Q/+ compared with wild-type mice. Reverse transcription-polymerase chain reaction and Western blotting showed that expression levels of other calcium handling proteins were unaltered, suggesting that calcium leak through mutant RyR2 underlies arrhythmogenesis and sudden death in young R176Q/+ mice.


CONCLUSIONS
Our findings demonstrate that a gain-of-function mutation in RyR2 confers an increased risk of cardiac arrhythmias and sudden death in young mice and that young R176Q/+ mice may be used as a model for elucidating the complex interplay between genetic and environmental risk factors associated with sudden infant death syndrome.
Mathur
Nitin
N
Department of Molecular Physiology and Biophysics, Division of Cardiology, Baylor College of Medicine, Houston, TX 77030, USA.
Sood
Subeena
S
Wang
Sufen
S
van Oort
Ralph J
RJ
Sarma
Satyam
S
Li
Na
N
Skapura
Darlene G
DG
Bayle
J Henri
JH
Valderrábano
Miguel
M
Wehrens
Xander H T
XH
D000322:Adrenergic Agonists / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics*; D002304:Cardiac Pacing, Artificial; D004195:Disease Models, Animal; D004562:Electrocardiography; D004837:Epinephrine / Q000494:pharmacology; D055879:Gene Knock-In Techniques; D020022:Genetic Predisposition to Disease; D006801:Humans; D007223:Infant; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation; D009206:Myocardium / Q000378:metabolism*; D010641:Phenotype; D012307:Risk Factors; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D013398:Sudden Infant Death / Q000235:genetics*; D017180:Tachycardia, Ventricular / Q000150:complications / Q000235:genetics* / Q000378:metabolism; D013806:Theophylline / Q000494:pharmacology; D056969:Voltage-Sensitive Dye Imaging
D000322:Adrenergic Agonists; D019837:Ryanodine Receptor Calcium Release Channel; D013806:Theophylline; D004837:Epinephrine