Figure 1.

T-Tubule Derangements in mdx Mice Are Associated With JPH-2 Misregulation

(A) Representative confocal images of cardiac myocytes stained with wheat germ agglutinin to delineate t-tubules. Older (8 months to 10 months) but not young (2 months to 3 months) mdx mice showed loss of regularity of the t-tubule network. Scale bar equals 5 μm. (B) Quantification of t-tubule organization in older (8 months to 10 months of age) WT, young, and older mdx mice. There was a significant reduction in t-tubule regularity in aged mdx mice. An asterisk (*) indicates p ≤ 0.05 when compared to WT; A pound symbol (#) indicates p ≤ 0.05 when compared to young mdx as determined by 1-way ANOVA with Tukey post-hoc analysis. N = 17 cells to 20 cells per genotype from 2 animals to 3 animals per genotype. Representative Western blot analyses and subsequent quantification from cardiac extracts of young (ages 2 months to 3 months) (C and D) and older (8 months to 10 months) (E and F) WT and mdx mice along with CBB stained SDS-PAGE, which served as a loading control. There was no difference in VGCC but there was a significant 75% reduction in JPH-2 levels in older mdx mice (p = 0.0003). N = 3 animals to 4 animals per genotype per age. (G) Representative confocal micrographs of cardiac myocytes from aged-matched (8 months to 10 months) control and mdx cardiac myocytes stained for JPH-2. Scale bar equals 5 μm. (H) Quantification of JPH-2 localization using TT_Power. Older mdx mice showed altered localization of JPH-2 in cardiac myocytes (p < 0.0001). N =17 cells to 19 cells from 2 animals to 3 animals per treatment. An asterisk (*) indicates p ≤ 0.05 as determined using Student t test. Values are presented as mean ± SEM. ANOVA = analysis of variance; CBB = Coomassie brilliant blue; JPH-2 = junctophilin-2; SDS-PAGE = sodium dodecyl sulfate−polyacrylamide gel electrophoresis; VGCC = voltage-gated calcium channel; WT = wild-type.