Destabilized Calcium Dynamics Visualized Using the Genetically-coded Probe GCaMPJ in Intact Hearts of Calstabin-null Mice

Optical imaging of intracellular calcium ions (Ca2+) using Ca2+-sensitive dyes or genetically encoded Ca2+ indicators (GECIs) offers high spatial and temporal resolution, and has revealed several critical mechanisms of Ca2+ signaling in cardiomyocytes. However, little progress has been made in the imaging of global Ca2+ events in intact mammalian hearts. Here, transgenic mice with cardiac-specific expression of GCaMPJ were generated, a new GECI with an overall enhancement in the sensitivity of Ca2+ dynamics compared to previous GCaMPs. Primarily, no cardiotoxicity was detected in the transgenic mice with cardiac-specific expression of GCaMPJ. GCaMPJ also showed superiority in indicating Ca2+ dynamics, and spiral and ripple waves of Ca2+ dynamics were detected in the intact hearts. The transgenic mice confirmed the function of the calstabin protein in modulating Ca2+ cycling in the integrated heart and further demonstrated that pharmacological stabilization of the ryanodine receptor (RyR) can prevent arrhythmias involving chaotic Ca2+ events.

使用钙敏感性染料或基因编码钙指示剂（genetically encoded Ca²+ indicators, GECIs）对细胞内钙离子（Ca²+）进行光学成像，具备极高的时空分辨率，已成功揭示心肌细胞内Ca²+信号传导的多项关键机制。然而，针对完整哺乳动物心脏内全局性Ca²+事件的成像研究却进展甚微。本研究构建了心脏特异性表达GCaMPJ的转基因小鼠——GCaMPJ是一款相较于既往GCaMP系列指示剂，整体钙动态敏感性显著提升的新型GECI。实验结果表明，该心脏特异性表达GCaMPJ的转基因小鼠未检测到心脏毒性。GCaMPJ在指示Ca²+动态变化方面同样展现出优异性能，研究团队在完整心脏中观测到了Ca²+动态的螺旋波与涟漪波。该转基因小鼠验证了钙稳定蛋白（calstabin）在整体心脏中调控Ca²+循环的功能，并进一步证实：对雷诺丁受体（RyR）进行药理学稳定化处理，可预防由紊乱性Ca²+事件引发的心律失常。