Fig. 1.

Induction of tdTomato expression in satellite cells labels myofibers by satellite cell fusion. a Pax7Cre;tdTomato mice were injected with tamoxifen once a day for five consecutive days to induce tdTomato expression in satellite cells. Images shown in this figure are from 6-month-old mice. b–e Representative images of TA sections show that 96 % of Pax7-expressing satellite cells are also expressing tdTomato. Insert highlights a Pax7+, tdTomato+ sub-laminar satellite cell. f Pax7Cre;tdTomato mice were injected with tamoxifen once a day for five consecutive days and then tissue was collected 2 weeks following the last injection. g–j Representative images of TA sections show Pax7-expressing satellite cells as tdTomato+ but also unexpectedly show tdTomato+ myofibers. Insert highlights a tdTomato-expressing myofiber with an associated Pax7+, tdTomato+ satellite cell. k–n Representative images of TA sections from Pax7Cre;tdTomato mice that were injected with only with corn oil showing no basal tdTomato expression prior to tamoxifen injection. Images display DAPI (blue), Sdc4 (green), tdTomato (red), Pax7 (white). ^ marks indicate satellite cells. Scale bars are 50 μm