Targeted Deletion of KCNE4 Impairs Ventricular Repolarization in Mice

by adjusting gel stiffness with different mixing ratios of PVA and crosslinker. Results:Myocyte contraction and calcium transients were measured in-gel and compared with load-free cells. Contracting cells in-gel showed a significantly lower fractional shortening (12.6 5 0.9 in-gel vs. 18.2 5 0.9 load-free, p<0.001), demonstrating a ‘‘knock-down factor’’ of 31% when the myocyte is pulling mechanical load. Contraction departure and return velocities were significantly slower in-gel than in the load-free state as expected. However, the systolic calcium transient was greater in-gel than load-free (Fura-2 fluorescence ratio peak height 1.47 5 0.09 in-gel vs. 0.87 5 0.04 load-free, p<0.0001), revealing the mechano-chemotransduction that translates external stress to intracellular Ca2þ increase. The calcium transient departure and return velocities were also significantly higher in-gel than load-free. Conclusions: Our newly-developed versatile Cell-in-Gel system provides a novel experimental method to control mechanical stress at the single cell level for investigating mechano-chemotransduction pathways in intact myocytes. The above experimental results are consistent with our modeling predictions, demonstrating the mechanical load effects on altering myocyte Ca2þ handling and contraction dynamics.