Transgenic Non-Human Animals Expressing A Truncated Activin Type II Receptor

A method of increasing muscle mass in a non-human animal comprising administering to the animal a myostatin propeptide, myostatin receptor, follistatin, an antibody that specifically binds to myostatin, or a functional fragment thereof, thereby increasing muscle mass in the animal.

A transgenic non-human animal whose genome contains a nucleic acid sequence comprising gene encoding a myostatin propeptide, a myostatin receptor, follistatin, or an antibody that specifically binds to myostatin, and a regulatory element comprising a muscle-specific promoter operably linked and integrated into the genome of the transgenic non-human animal, wherein the nucleic acid sequence is expressed so as to result in increased muscle mass in the transgenic non-human animal as compared to a corresponding non-transgenic animal.

A method of identifying an agent that specifically interacts with a myostatin receptor, the method comprising:

• a) contacting a myostatin receptor with a test agent, and b) determining that the test agent specifically interacts with the myostatin receptor, thereby identifying an agent that specifically interacts with a myostatin receptor.