Fig. 3: Atf3 deletion provokes premature SC activation and pseudo-regeneration in homeostatic muscle.

a SCs from Ctrl or iKO mice were cultured for 24 h and treated with EdU for 6 h before staining for EdU (red) and Pax7 (green). Scale bar: 50 μm. p = 0.0000014. b IF staining of Pax7 (green) and MyoD (red) on the above SCs cultured for 24 h. Scale bar: 50 μm. p = 0.00050. c Representative FACS plots showing the size of FISCs sorted from Ctrl or iKO muscles. p = 0.050. d Freshly isolated myofibers from Ctrl or iKO mice were cultured for 36 h and treated with EdU for 6 h before staining for EdU (red) and Pax7 (green). Scale bar: 50 μm. p = 0.00034. e IF staining of Pax7 (green) and MyoD (red) on the above myofibers immediately after isolation or cultured for 3 h. Scale bar: 25 μm. f Quantification of the percentage of Myod-Pax7+ and Myod+Pax7+ SCs. p = 0.0098 and 0.00035. g Quantification of the numbers of Pax7+ SCs per 100 fibers on uninjured Ctrl or iKO muscles 5, 21, 28 and 56 days after TMX injection. p = 0.96, 0.0018, 0.000049 and 0.00018. h H&E staining of the above uninjured muscles 56 days after TMX injection. Scale bar: 50 μm. p = 0.00043. i Upper: Schematic outline of the in vivo EdU assay performed on uninjured Ctrl or iKO muscle; EdU was injected by IP 5 days after TMX. The muscles were collected 21 days later. Lower IF staining of EdU (red) and Laminin (green). Scale bar: 25 μm. p = 0.00024. n = 5 mice per group (a–h); n = 3 mice per group (i). All the bar graphs are presented as mean ± SD, Student’s t test (two-tailed unpaired) was used to calculate the statistical significance (a–d, f–i): *p < 0.05, **p < 0.01, ***p < 0.001. n.s. no significance. Source data are provided as a Source Data file.