Myostatin (fomerly known as Growth and Differentiation Factor 8) is a growth factor that limits muscle tissue growth, i.e. higher concentrations of myostatin in the body cause the individual to have lesser developed muscles. The myostatin protein is produced in muscle cells, circulates in the blood and acts on muscle tissue, apparently by slowing down the development of muscle stem cells. Myostatin is a compound responsible for limiting muscular hypertrophy, and the idea is that if myostatin can be disabled, muscular growth should proceed without limitations.
Myostatin is a growth factor that regulates the size of muscles beginning in early embryonic development and continuing throughout life. Myostatin acts by inhibiting the growth of muscles, It prevents them from growing too large. Myostatin is also known as growth and differentiation factor 8 (GDF-8). It is a protein made up of two identical subunits. Each subunit contains 110 amino acids. The gene encoding myostatin is termed MSTN (or GDF8) and is on chromosome 2 in band 2q32.1.
Myostatin is a potent inhibitor of muscle growth. Genetic deletion of Myostatin leads to massive hyperplasia and hypertrophy of skeletal muscle. However, the overall muscle pattern is preserved. We show that, during chick embryonic development, Myostatin is expressed at stages and positions unlikely to influence qualitative muscle development. In the somites, Myostatin is predominantly expressed in a central domain of the dermomyotome but not at the dorsomedial and ventrolateral lips, where most cells for myotomal elongation are recruited. During limb bud development, Myostatin is transiently expressed at early stages in both myogenic and nonmyogenic regions. Myostatin is reexpressed during limb bud development at a time when splitting of muscle is underway. Heterotopically developed wing buds that fail to form muscle still express Myostatin. This demonstrates that, in the limb, not all Myostatin-expressing cells are of myogenic origin. Ectoderm and Sonic hedgehog have different effects on the expression of Myostatin dependent on stages at which the operation was performed and the length of the postoperative period. Finally, we show that application of Myostatin protein into the developing limb bud results in a down-regulation of Pax-3 and Myf-5, both genes associated with proliferation of myogenic cells; and, furthermore, Myostatin also prevents the expression of MyoD, a gene associated with muscle differentiation. The long-term effect of Myostatin treatment leads to a deficiency of limb muscle. Therefore, Myostatin negatively affects gene expression of transcription factors, which are necessary for establishing myogenic cell identity.