Fig. 13.

Muscles from the severe FSHD-like model mice start to undergo apoptosis within 6 days of induced DUX4-fl expression. TA muscles from male severe model mice that had undergone treadmill exhaustion analysis (see Fig. 9) were assayed at SD3 (a, e), SD6 (b, f), and SD9 (c, g). ACTA1-MCM (k, l, o, p) and mild FSHD-like model mice (D, H) were analyzed at indicated time point. Green signal in the TUNEL assay (a–d, i–l) indicates nuclei undergoing apoptosis, compared with DAPI staining (e–h, m–p) showing all nuclei in the same histological sections. DNase-I treated histological section of ACTA1-MCM (i, m) and TUNEL staining of the severe model SD9 sample without the TdT enzyme (j, n) are used as positive and negative controls for TUNEL staining, respectively. Scale bar = 200 μm. Quantitative analysis of data is shown in Figure S14