C313Y-MstnGF is unable to inhibit the proliferation of C2C12 myoblasts. The difference in absorbance at 450 and 630 nm correlates to cell density after incubation with WT or C313Y myostatin growth factor, precursor protein or latent complex. Cells incubated in media in the absence of protein but with buffer (Buffer only) or without buffer (Cells only) were used as controls. Error bars represent the standard error of the mean for triplicate samples from three independent experiments for WT samples and two independent experiments for C313Y. Statistical significance was calculated using a paired Student's t-test where ** P < 0.05.