The present invention provides a substantially purified growth differentiationfactor (GDF) receptor, including a GDF-8 (myostatin) receptor, as well asfunctional peptide portions thereof. In addition, the invention provides avirtual representation of a GDF receptor or a functional peptide portionthereof. The present invention also provides a method of modulating an effectof myostatin on a cell by contacting the cell with an agent that affectsmyostatin signal transduction in the cell. In addition, the invention providesa method of ameliorating the severity of a pathologic condition, which ischaracterized, at least in part, by an abnormal amount, development ormetabolic activity of muscle or adipose tissue in a subject, by modulatingmyostatin signal transduction in a muscle cell or an adipose tissue cell inthe subject. The invention also provides a method of modulating the growth ofmuscle tissue or adipose tissue in a eukaryotic organism by administering anagent that affects myostatin signal transduction to the organism.
