Myostatin - Double-muscle Mutation in Humans

Double-muscle Mutation in Humans

Myostatin is active in muscles used for movement (skeletal muscles) both before and after birth. It normally restrains muscle growth, ensuring that muscles do not grow too large. Mutations that reduce the production of functional myostatin lead to an overgrowth of muscle tissue. Myostatin-related muscle hypertrophy has a pattern of inheritance known as incomplete autosomal dominance. People with a mutation in both copies of the MSTN gene in each cell (homozygotes) have significantly increased muscle mass and strength. People with a mutation in one copy of the MSTN gene in each cell (heterozygotes) also have increased muscle bulk, but to a lesser degree.

In 2004, a German boy was diagnosed with a mutation in both copies of the myostatin-producing gene, making him considerably stronger than his peers. His mother has a mutation in one copy of the gene.

An American boy born in 2005, Liam Hoekstra, was diagnosed with a clinically similar condition but with a somewhat different cause: his body produces a normal level of functional myostatin, but because he is stronger and more muscular than most others his age, his doctor believes that a defect in his myostatin receptors prevents his muscle cells from responding normally to myostatin. Liam appeared on the television show World's Strongest Toddler.