Myostatin (also known as growth differentiation
factor 8, abbreviated GDF-8) is a myokine, a protein produced and released by myocytes that acts on muscle cells' autocrine function to inhibit myogenesis: muscle
cell growth and differentiation. In humans it is encoded by the MSTN gene.[6]
Myostatin is a secreted growth differentiation
factor that is a member of the TGF beta protein family Animals either lacking
myostatin or treated with substances that block the activity of
myostatin have significantly more muscle mass. Furthermore, individuals who have mutations in both copies of the
myostatin gene have significantly more muscle mass and are stronger than normal. There is hope that studies into
myostatin may have therapeutic application in treating muscle wasting diseases such as muscular dystrophy.[ After that discovery, several laboratories cloned and established the nucleotide sequence of a
myostatin gene in two breeds of cattle, Belgian Blue and Piedmontese. They found mutations in the
myostatin gene (various mutations in each breed) which in one way or another lead to absence of functional myostatin.Unlike mice with a damaged
myostatin gene, in these cattle breeds the muscle
cells multiply rather than enlarge. People describe these cattle breeds as "double muscled", but the total increase in all muscles is no more than 40%Animals lacking
myostatin or animals treated with substances such as follistatin that block the binding of
myostatin to its receptor have significantly larger muscles. Thus, reduction of
myostatin could potentially benefit the livestock industry, with even a 20 percent reduction in
myostatin levels potentially having a large effect on the development of musclesHowever, the animal breeds developed as homozygous for
myostatin deficiency have reproduction issues due to their unusually heavy and bulky offspring, and require special care and a more expensive diet to achieve a superior yield. This negatively affects
economics of myostatin-deficient breeds to the point where they do not usually offer an obvious advantage. While hypertrophic meat (e.g. from Piedmontese beef) has a place on the specialist market due to its unusual properties, at least for purebred myostatin-deficient strains the expenses and (especially in cattle) necessity of veterinary supervision place them at a disadvantage in the bulk market.
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