T-tubule integrity in Flag-Rad and Flag-RadΔCT cardiomyocytes. (A) Representative α-actinin staining of Flag-Rad and Flag-RadΔCT cardiomyocytes. Scale bar, 10 μm; magnification is the same for both panels. (B) Live cardiomyocyte di-8-ANEPPS staining of representative cardiomyocytes. FFT analysis of t-tubule periodicity did not vary significantly between genotypes (mean spacing 1.78 [SEM = 0.008] and 1.81 [SEM = 0.012] µm, for Flag-Rad and Flag-RadΔCT, respectively) (linear mixed model, nesting cells into mice, genotype F = 3.058, P = 0.133, N = 8 mice, n = 127 cells). Scale bar, 10 μm; magnification is the same for all panels. (C) FFT analysis of resting sarcomere length from brightfield microscopy of live cells did not vary significantly between genotype (mean spacing 1.87 [SEM = 0.0385] and 1.93 [SEM = 0.0388] µm, for Flag-Rad and Flag-RadΔCT) (linear mixed model, nesting cells into mice, genotype F = 0.958, P = 0.372, N = 7 mice, n = 122 cells).