Disrupted Myostatin Function

Myostatin is a regulatory protein that discourages production of muscle proteins. Individuals that have bulky muscles as a result of a myostatin deficiency are said to have myostatin-related muscle hypertrophy.

A. Liam, a Michigan boy whose muscles do not respond to the inhibitory effect of myostatin. As a result he is unusually strong for his age.

B A bully whippet (left) does not make myostatin. Such heavily muscled dogs are often euthanized by breeders because they do not conform to the standard for the breed. Bully whippets are homozygous for a two-base deletion mutation in the myostatin gene. The mutation changes an mRNA codon for cysteine to a stop codon.