Ryanodine receptor (RyR2) mutations in sudden cardiac death: studies in extended pedigrees and phenotypic characterization in vitro.
BACKGROUND
Catecholaminergic polymorphic ventricular tachycardia caused by mutations in the RyR2 gene manifests as severe arrhythmias, and may provide a candidate for sudden cardiac deaths.


METHODS
We screened 19 victims of SCD for mutations in the RyR2 gene by direct sequencing, and analyzed DNAs from available family members and from 300 controls. Medico-legal investigations were conducted by experienced pathologists. We performed resting ECG, cardiac ultrasonography, exercise stress test, epinephrine test and 24-hour ambulatory ECG recording to related mutation carriers (n = 17). The single channel recordings of the mutant RyR2s were conducted in planar lipid bilayers, and the open probabilities were determined by sequential addition of CaCl(2) to the cis-side.


RESULTS
We identified two novel RyR2 missense mutations (G2145R and R3570W) in three victims of SCD. The surviving carriers of these mutations exhibited only minor, if any structural abnormalities, and two carriers of R3570W showed ventricular arrhythmias predominantly at rest. Single channel recordings revealed a gain-of-function defect in native unphosphorylated R3570W and a similar but milder defect in native G2145R.


CONCLUSIONS
RyR2 mutations manifesting as a gain-of-function defect in vitro may be detectable in some cases of SCD. Not all RyR2 mutations lead to a uniform, highly penetrant CPVT phenotype.
Research Program for Molecular Medicine, University of Helsinki, Helsinki, Finland. annukka.marjamaa@helsinki.fi
Annukka
A
Marjamaa
Päivi
P
Laitinen-Forsblom
Anetta
A
Wronska
Lauri
L
Toivonen
Kimmo
K
Kontula
Heikki
H
Swan
D000293:Adolescent; D000328:Adult; D000368:Aged; D009202:Cardiomyopathies / Q000235:genetics* / Q000401:mortality; D016757:Death, Sudden, Cardiac; D005190:Family; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008875:Middle Aged; D020125:Mutation, Missense; D010375:Pedigree; D010641:Phenotype; D012307:Risk Factors; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics* / Q000378:metabolism; D017180:Tachycardia, Ventricular / Q000235:genetics* / Q000401:mortality; D055815:Young Adult
D019837:Ryanodine Receptor Calcium Release Channel