Figure 6. Human muscle biopsy tissues from individuals with LMNA muscular dystrophy have increased DNA damage.

Cryopreserved human muscle biopsy tissues from individuals with LMNA muscular dystrophy and age-matched controls were stained for either (a) 53BP1, DAPI, and phalloidin or (b) 53BP1, DAPI, and dystrophin. Arrowheads denote nuclei within muscle fibers, identified by dystrophin labeling of the muscle fiber membrane. Each muscular dystrophy patient possesses a LMNA point mutation producing a single amino acid substitution (Supplementary Table 1). The LMNA mutations cause reduced fiber size, abnormally shaped fibers, and increased nuclear 53BP1 staining. Scale bar: 30 μm. (c-e) Patients were stratified based on the age at time of tissue collection. The nuclear intensity values of 53BP1 were binned into 11 categories based on the level of intensity (color coding on the right). The X-axis shows the mutant lamin A/C expressed in individuals with an LMNA mutation and the age-matched control samples expressing wild-type lamin A/C. The Y-axis represents the relative percent intensity of 53BP1 staining quantified using ImageJ. The intensity values did not meet the criteria for a normal distribution. For panel (c) a two-sided Kruskal-Wallis one-way analysis of variance (ANOVA), followed by the two-sided Dunn post hoc test, were used to determine if there was a significant difference in staining among the genotypes. For panels (d) and (e) a two-sided Mann-Whitney non-parametric test was used for comparisons. n indicates the number of nuclei scored per patient. All bar plots show mean value ± standard error of the mean.