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  • Title: Physiological consequences of the P2328S mutation in the ryanodine receptor (RyR2) gene in genetically modified murine hearts.
    Author: Goddard CA, Ghais NS, Zhang Y, Williams AJ, Colledge WH, Grace AA, Huang CL.
    Journal: Acta Physiol (Oxf); 2008 Oct; 194(2):123-40. PubMed ID: 18419777.
    Abstract:
    AIM: To explore the physiological consequences of the ryanodine receptor (RyR2)-P2328S mutation associated with catecholaminergic polymorphic ventricular tachycardia (CPVT). METHODS: We generated heterozygotic (RyR2 p/s) and homozygotic (RyR2 s/s) transgenic mice and studied Ca2+ signals from regularly stimulated, Fluo-3-loaded, cardiac myocytes. Results were compared with monophasic action potentials (MAPs) in Langendorff-perfused hearts under both regular and programmed electrical stimulation (PES). RESULTS: Evoked Ca2+ transients from wild-type (WT), heterozygote (RyR2 p/s) and homozygote (RyR2 s/s) myocytes had indistinguishable peak amplitudes with RyR2 s/s showing subsidiary events. Adding 100 nm isoproterenol produced both ectopic peaks and subsidiary events in WT but not RyR2 p/s and ectopic peaks and reduced amplitudes of evoked peaks in RyR2 s/s. Regularly stimulated WT, RyR2 p/s and RyR2 s/s hearts showed indistinguishable MAP durations and refractory periods. RyR2 p/s hearts showed non-sustained ventricular tachycardias (nsVTs) only with PES. Both nsVTs and sustained VTs (sVTs) occurred with regular stimuli and PES with isoproterenol treatment. RyR2 s/s hearts showed higher incidences of nsVTs before but mainly sVTs after introduction of isoproterenol with both regular stimuli and PES, particularly at higher pacing frequencies. Additionally, intrinsically beating RyR2 s/s showed extrasystolic events often followed by spontaneous sVT. CONCLUSION: The RyR2-P2328S mutation results in marked alterations in cellular Ca2+ homeostasis and arrhythmogenic properties resembling CPVT with greater effects in the homozygote than the heterozygote demonstrating an important gene dosage effect.
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