Investigation of Molecular Mechanism for Excitation-contraction Coupling in Heart

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This study has been performed to elucidate a molecular mechanism for excitation-contraction coupling and examine the structure-function relationship of ryanodine receptor in heart.We attempted to obtain cardiac-specific sorcine knockout mice, which has been known to interact both with dihidropyridine receptor and with ryanodine receptor. We, first, isolated mouse sorcine gene and analyzed it to obtain targeting construct.We inserted a flox sequence in the first and second exon and electroporated it into ES cells. After selection with G418, we identified recombinant ES cells with PCR and sourthern blot analysis. We injected the ES cells into mouse uterus and obtained chimera mice.We have crossed floxed ryanodine receptor mice with MLC-2v Cre mice. The mice, which lack one allele of the gene, appeared normal. Western blot analysis revealed about 50 % decrease in ryr2 protein level but no differences in SEACA, NCX, and CAQ. Echocardiography indicated that heterozygous ryr2 knockout mice showed no significant differences in chamber size and ejection fraction compared with wild type mice. Hemodynamic study also indicated ablation of one allele of the gene led to no alteration in cardiac function.