Fig. S6.

T-tubule defects and local alterations of voltage-activated Ca²⁺ release in MTM1-deficient fibers. The t-tubule network was stained with di-8-anepps. (A–C) Each panel shows a line-scan rhod-2 F/F₀ Ca²⁺ transient (Right) triggered by a voltage-clamp depolarization to the indicated value. Traces below correspond to the rate of Ca²⁺ release at three positions of the scanned line (indicated by colored arrows). The green image on Left is an x,y frame of the di-8-anepps fluorescence in the same fiber. The longitudinal profile of di-8-anepps fluorescence measured within a rectangular region (white rectangle) encompassing five pixels on each side of the position of the rhod-2 scanned line is reported next to the x,y di-8-anepps image (green trace) to better view the spatial correlation or absence of spatial correlation between defects in t-tubule pattern and in Ca²⁺ transient. (A) Example of clear correlations between localized defects in t-tubule pattern and in Ca²⁺ release. (B) Example showing a large fiber region with depressed Ca²⁺ release but no apparent sign of related alteration in t-tubule pattern. (C) Example of slow and delayed Ca²⁺ release in a fiber yielding an overall very much altered t-tubule pattern.