p29 enhances myogenesis suppressed by myostatin and GDF11, but not activin or TGF-β1.

<p>(<b>A</b>) C2C12 myoblasts were maintained in growth medium. Mononucleated myoblasts differentiate into multinucleated myotubes in differentiation medium with (+) or without (–) 1 μM p29 for 7 days. Phase-contrast and fluorescence images of cells stained for myotube markers MyHC, myogenin, and CK. Scale bar, 100 μm. (<b>B</b>) The protein analysis of MyHC in C2C12 cells expressing in growth or differentiation media with (+) or without (–) 1 μM p29. (<b>C</b>) Wright-Giemsa-stained C2C12 cells expressing an empty vector in growth or differentiation media with (+) or without (–) 1 μM p29 (<b>left</b>). Scale bar, 100 μm. Fusion indices were calculated in triplicate as the percentage of the total nuclei in myotubes/mm² (<b>right</b>). Values are the means ± SD (<i>n</i> = 5). *<i>P</i> < 0.05. (<b>D</b>) Phase-contrast (<b>left)</b> and fluorescence (<b>right</b>) images of MyHC in C2C12 myoblasts expressing the empty vector (mock), myostatin, GDF11, activin A, or TGF-β1 at 7 days after differentiation with (+) or without (–) 1 μM p29. Scale bar, 100 μm. (<b>E</b>) Immunoblot analysis of MyHC protein in C2C12 cells at 7 days after differentiation with (+) or without (–) 1 μM p29 (<b>upper</b>). Densitometric analysis (<b>lower</b>). Values are the mean ± SD fold increases compared with untreated C2C12 cells expressing the empty vector (mock) (<i>n</i> = 5). *<i>P</i> < 0.05.