Figure 1.

mTOR controls miR-1 levels during myogenesis both in vitro and in vivo. (A) C2C12 cells were induced to differentiate in the absence or presence of 50 nM rapamycin (Rap). RNA was isolated at the indicated time points of differentiation (Diff), and miR-1 levels were measured by qRT-PCR. (B) C2C12 cells were transduced with lentiviruses expressing two independent mTOR shRNAs or scrambled shRNA, selected with puromycin, and induced to differentiate. At 72 h of differentiation, cells were lysed and subjected to Western analysis. 59-kD S6K1 has an apparent molecular mass of 70 kD on SDS-PAGE. (C) Cells treated as in B were harvested at the indicated times of differentiation, and miR-1 levels were measured by qRT-PCR. In both A and C, relative levels are shown as fold increase compared with the level at 0 h. (D) TA muscles in mice hind limbs were injured by intramuscular injection of BaCl₂ followed by daily intraperitoneal injection of rapamycin. On various days AI, injected muscles were isolated and homogenized for RNA isolation followed by quantitative PCR to determine relative miR-1 levels, shown as fold increase compared with uninjured muscles. Data are presented as mean ± SD (n = 3).