Figure 1.

Comparison of activin and myostatin antagonism for FST mutants. FST mutants were tested at a single dose (200 ng/ml) for ability to antagonize activin (5 ng/ml) or myostatin (15 ng/ml) in an in vitro bioassay, and results were expressed relative to WT FST tested in the same assay so that a ratio of 1 indicates identical antagonism to that of WT FST. The first group represents deletion, substation, or rearrangement of whole FST domains, whereas the mutants in the second and third groups represent point mutations in FSD1 or -2, respectively. Mutants in which activin antagonism was compromised but myostatin antagonism activity remained largely intact were investigated further. Shown are representative results from one of at least three experiments.