Fig. 4

Muscle damage and FLNc content in soleus muscles of adult WT and Hom mice. a Immunostaining of soleus muscle cross sections for muscle damage marker Xin reveals increased muscle damage in Hom animals. FLNc colocalizes with Xin in damage areas. Note that identical scan settings were applied. b Statistical analysis of the area of muscle damage using the Mann-Whitney U-test reveals significantly increased damage in Hom mice: median of lesion area in % of total muscle area, 0.48 in WT versus 1.97 (n = 6 in each group; p = 0.0022). c-e Comparison of FLNc and titin expression levels in soleus muscle of wildtype and Hom mice. c Double staining of longitudinal sections of soleus muscle for FLNc and an epitope of titin close to the Z-disc shows significantly reduced levels of FLNc in Z-discs of Hom mice. Note that identical scan settings were used. Instead, FLNc was found highly concentrated in lesions (asterisks) and MTJs (arrows). d Illustration of Zen software line profiles of the mean immunofluorescent intensities of FLNc and titin in Z-discs of WT and Hom mice using the line profile option of the microscope and Zen 2 software Version 2.0.0.0. Note comparable intensities of FLNc and titin signals in Z-discs of wildtype mice but reduced FLNc intensity in Hom mice. e Quantification of FLNc Z-disc signal corrected against the background and normalized against titin confirms a highly significant reduction of FLNc levels in Z-discs in Hom mice. Statistical analysis was performed for sections from 3 mice of each genotype and in each 10 Z-discs were included in the calculations. Kruskal-Wallis test one-way analysis of variance; post-hoc analyses by performing Mann-Whitney U-tests of both groups (median of WT: 1.16, median of Hom: 0.22; p < 0.0001). For all experiments the RR90 antibody was used to detect FLNc. Bars: 200 μm (a), 10 μm (c), 5 μm (d)