Composite polymorphisms in the ryanodine receptor 2 gene associated with arrhythmogenic right ventricular cardiomyopathy.
OBJECTIVE
Mutations in the cardiac ryanodine receptor (RYR2) gene have been reported to cause arrhythmogenic right ventricular cardiomyopathy (ARVC). The molecular mechanisms by which genetic modifications lead to ARVC are still not well understood.


METHODS
ARVC patients were screened for mutations in the RYR2 gene by denaturing HPLC and DNA sequencing. Single channel measurements were carried out with RyR2 channels purified from explanted hearts of ARVC patients.


RESULTS
None of the published RYR2 mutations were found in our ARVC-cohort. However, we identified two single nucleotide polymorphisms (SNPs) in exon 37 of the human RYR2 gene which lead to the amino acid exchanges G1885E and G1886S, respectively. Both SNPs together were found exclusively in 3 out of 85 ARVC patients in a composite heterozygous fashion (genotype T4). This genotype was associated with ARVC (p<0.05) but not with dilated cardiomyopathy (DCM, 79 patients) or none-failing controls (463 blood donors). However, either one of the two SNPs were identified in further 7 ARVC patients, in 11 DCM patients, and in 64 blood donors. The SNP leading to G1886S may create a protein kinase C phosphorylation site in the human RyR2. Single channel recordings at pCa4.3 revealed four conductance states for the RyR2 of genotype T4 and a single open state for the wild type RyR2. At pCa7.7, the lowest subconductance state of the RyR2 channel of genotype T4 persisted with a greatly enhanced open probability indicating a leaky channel.


CONCLUSIONS
The RyR2 channel leak under diastolic conditions could cause SR-Ca2+ depletion, concomitantly arrhythmogenesis and heart failure in a subgroup of ARVC patients of genotype T4. A change in the RyR2 subunit composition due to the combined expression of both SNPs alters the behaviour of the tetrameric channel complex.
Milting
Hendrik
H
Herz- und Diabeteszentrum NRW, Klinik der Ruhr-Universität Bochum, Erich und Hanna Klessmann-Institut für Kardiovaskuläre Forschung und Entwicklung, Georgstr. 11, 32545 Bad Oeynhausen, Germany. hmilting@hdz-nrw.de
Lukas
Nina
N
Klauke
Bärbel
B
Körfer
Reiner
R
Perrot
Andreas
A
Osterziel
Karl-Josef
KJ
Vogt
Jürgen
J
Peters
Stefan
S
Thieleczek
Rolf
R
Varsányi
Magdolna
M
D000328:Adult; D000595:Amino Acid Sequence; D019571:Arrhythmogenic Right Ventricular Dysplasia / Q000235:genetics* / Q000378:metabolism; D002311:Cardiomyopathy, Dilated / Q000235:genetics / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004252:DNA Mutational Analysis / Q000379:methods; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics* / Q000502:physiology; D013045:Species Specificity
D019837:Ryanodine Receptor Calcium Release Channel