Morphological characteristics of primary myocytes from WT and R2509C-RYR1 mice. (A) Bright-field images of primary myocytes derived from WT (left) and R2509C-RYR1 mice (R2509C-Het [middle] and R2509C-Hom [right]) at 3 d after differentiation. Myocytes highlighted by red lines (also indicated by yellow arrows) are shown in the kymographs at the bottom (i.e., time-dependent changes in contrast). (B) Confocal images showing immunostained MHC (MF20) in red and nuclei stained with 4′,6-diamidino-2-phenylindole (DAPI) in cyan in primary myocytes. Left, middle, and right indicate WT, R2509C-Het, and R2509C-Hom myocytes, respectively. (C) Expression levels of MHC in myocytes. Left: Western blotting showing MHC and the loading control glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in myocytes expressing WT, R2509C-Het (Het), and R2509C-Hom (Hom) myocytes. Molecular mass standards are shown on the right (kD). Right: Graph showing MHC/GAPDH analyzed from band intensities in Western blotting in WT, Het, and Hom. Data normalized by that of WT at day 3. Data are means ± SD (n = 4–6) and analyzed by two-way ANOVA with Tukey’s test. Primary myocytes were cultured from three mice (N = 3) in each group.