Abstract 19448: Heterozygous Knock-out of Ryanodine Receptor 2 in Rabbits Produces Haploinsufficiency in the Absence of Compensatory Remodeling of the Heart
The Ryanodine Receptor type 2 (RyR2) is the major Ca2+ release channel in the heart. It is involved in excitation-contraction coupling (e-c coupling), the process that turns electrical activity into mechanical contraction in the cardiac muscle. During an action potential, RyR2 releases Ca2+ from the sarcoplasmic reticulum (SR), after being activated by a small Ca2+ influx (ICa) through L-type Ca2+ channels. RyR2 has prompted extensive research over the last two decades, because mutations in this channel are the culprits of severe arrhythmogenic syndromes, and because the details of its regulation is not fully understood. Using RNA-guided endonuclease genome editing, we generated a novel RyR2 knockout rabbit model to determine the cardiac effects of RyR2 deficiency. After breeding heterozygous knockout rabbits (RyR2+/-) we have not observed homozygotes, suggesting that, as previously reported for mice, complete ablation of RyR2 is embryonic lethal. Using Western blots, we found that RyR2 expression is decreased in the left ventricle (LV) of RyR2+/- rabbits (32.98±2.90% of RyR2+/+, n=3 per genotype, p<0.05), while other e-c coupling proteins were unchanged (n=3 per genotype, p>0.05). Interestingly, we did not observe any functional or structural abnormalities in RyR2+/- animals subjected to echocardiography (n=7 per genotype, p>0.05). Histological analysis of LV biopsies revealed no difference in the general microstructure of the tissue (n=3 per genotype). Finally, basic electrocardiogram parameters were not different between RyR2+/- and RyR2+/+ rabbits (heart rate, QTc interval, PR interval, n=7 per genotype, p>0.05). These data suggest that RyR2 haplo-deficiency is compensated in the absence of a whole organ phenotype. We will perform Ca2+-imaging and electrophysiologic studies in LV myocytes, to determine whether the cellular e-c coupling mechanism undergoes functional changes to adjust for RyR2 deficiency. These studies will contribute to better understand the regulation of Ca2+ handling in normal cardiac function. Furthermore, they will give valuable insights into the role of RyR2 in heart disease.
Author Disclosures: F.J. Alvarado: None. J.J. Hernandez: None. D. Wang: None. J. Xu: None. J. Zhang: None. Y.E. Chen: None. H.H. Valdivia: None.
- © 2014 by American Heart Association, Inc.