Figure 1. Tw2-expressing and Pax7-expressing cells are distinct cell types in skeletal muscle.

(a) Immunostaining of Tw2 (red) and Pax7 (green) on transverse sections of gastrocnemius muscle of 3-month old C57Bl6 WT mice. Myofibers were co-stained with wheat germ agglutinin (WGA) (white) and DAPI (blue). Arrows indicate Pax7+ cells and arrowheads indicate Tw2+ cells. Scale bar: 50 um.

(b) Quantification of the number of Pax7+, Tw2+, and Pax7+/Tw2+ double positive cells per field in 3-month old C57Bl6 WT mice. Quantification was performed on the top panel images in Fig. 1a. For each muscle section, at least 6 different fields were quantified and averaged. Data are mean ± S.E.M. N=6 mice.

(c) TA muscle of C57Bl6 WT mice was injured by CTX injection and harvested on Days 4, 7 and 10 post injury. Muscle sections were stained for Pax7 (green), Tw2 (red), DAPI (blue) and WGA (white). CTL: contralateral TA muscle. Scale bar: 100 um.

(d) Quantification of the number of Pax7+, Tw2+, and Pax7+/Tw2+ double positive cells per field in C57Bl6 WT mice on days 4, 7 and 14 post-CTX injury. For each muscle section, at least 6 different fields were quantified and averaged. Data are mean ± S.E.M. N=3 mice.

(e) Tw2 expression in TA muscle of Pax7-CreERT2; R26-tdTO mice after CTX injury. Adult Pax7-CreERT2; R26-tdTO mice were treated with TMX for 3 alternating days. One week after the first dose of TMX, CTX injury was performed on TA muscle. Muscles were harvested at Days 4 and 7 post injury and immunostained for Tw2 (green) and DAPI (blue). Scale bar: 100 um.

(f) Quantification of the number of Pax7+ (tdTO+), Tw2+, and Pax7+/Tw2+ double positive cells per field in Pax7-CreERT2; R26-tdTO on days 4 and 7 post-CTX injury. Pax7+ cells were detected by tdTO+ signal. For each muscle section, at least 6 different fields were quantified and averaged. Data are mean ± S.E.M. N=3 mice.

Statistic source data for b,d,f are provided in Supplementary Table 3.