Myostatin manipulation in vivo.

<p>Neonatal C57 mice (day 4–5) were treated with either Saline (n = 12), AAV9-LacZ (n = 11), AAV9-dnMSTAT (n = 12), or AAV9-MSTAT (n = 8),via subxiphoid injection to target the heart. A saline injection group was added to control for viral effects. (A) X-gal histochemistry demonstrates distribution of transgene expression. Western blot demonstrates expression of (B) dominant negative myostatin (propeptide antibody), (C) myostatin precursor (∼50 kDa) and processed C-monomer (∼13 kDa) (C-terminus antibody), and (D) phospho-Smad2/3. Samples from myostatin knock-out (MSTN KO) mouse heart and skeletal muscle, as well as from normal (C57) mouse skeletal muscle were also run as controls. The precursor protein is depicted with an arrow at 50 kDa and is present at high levels in the MSTN lane and absent in the MSTN KO lanes. Proposed C-dimer and monomer bands are also depicted with an arrow. Predicted molecular weights for the various forms of myostatin are as follows: full length precursor monomer (43–45 kDa); propeptide (30–32 kDa); C-terminus monomer (12–13 kDa); active C-dimer (24–26 kDa). Glycosylation may causes these forms to run approximately 5–10 kDa higher than predicted on PAGE. (E) Quantification of myostatin full-length precursor (∼50 kDa). *p<0.05 vs. Saline and LacZ (ANOVA). #p<0.05 vs. Saline, LacZ, and dnMSTAT (ANOVA). Scale bar represents 1 mm (lo) or 200 µm (hi).