The contraction machinery protein, actin, exists in different forms in the adult heart and skeletal muscles.
The heart form, ACTC, is the dominant form in skeletal muscle of the fetus.
However during development, the skeletal form, ACTA1, increases in production and by birth has taken over.
The researchers suggested that mutations to the ACTA1 gene cause a rare but serious myopathy or muscular disease. Most patients die within the first year of life and some are born almost completely paralyzed.
Lead researcher Nowak showed that mice lacking ACTA1 died within nine days after birth.
The team sought to determine if ACTC could compensate for a lack of ACTA1.
They crossed Acta1 mutant mice with transgenic mice that express human ACTC at high levels in skeletal muscle cells.
The resulting mice didn't die at nine days. In fact, almost 93.5pct survived more than three months, and some more than two years.
Moreover the mice's locomotor performance was comparable with wild-type, as was their overall muscle strength and their endurance was actually higher-they ran faster and for longer.
The findings were published in the Journal of Cell Biology.