Fig. 3

Excitation-contraction coupling in single isolated muscle fibers is altered. All values are mean ± SEM. Statistical significance was determined using a Student’s t-test. a Representative confocal images of T-tubule network stained with di-8-anepps from a CTRL and a RyR1-Rec fiber, allowing evaluation of T-tubule density and sarcomere length, performed in 42 CTRL fibers and 41 RyR1-Rec fibers (4 mice in each group). b Representative DHPR Ca²⁺ current from a CTRL and a RyR1-Rec fiber in response to 0.5 s-long depolarizing steps to the indicated levels (10 mV increment). c Voltage-dependence of the peak DHPR Ca²⁺ current density. d Parameters obtained from the fit of curves c in 29 CTRL fibers and 30 RyR1-Rec fibers (5 mice in each group), (cf Additional file 1: Supp. Method). e Representative x,t images of rhod-2 fluorescence (a.u.) from a CTRL and a RyR1-Rec fiber stimulated by a voltage-clamp depolarizing pulse to − 10 mV. f Representative line-averaged rhod-2 Ca²⁺ transients from a CTRL and from a RyR1-Rec fiber in response to voltage-clamp pulses to the indicated levels. g Rate of SR Ca²⁺ release calculated from the curves shown in f. h Voltage-dependence of the peak rate of SR Ca²⁺ release (top) and of the time-to-peak rate of SR Ca²⁺ release (bottom). i Parameters obtained from fitting the peak rate of SR Ca²⁺ release vs voltage relationship with a Boltzmann function in each fiber (cf Additional file 1: Supplementary Method). Data are from the same fibers as in b–d