Myostatin Mutation Associated with Gross Muscle Hypertrophy in a Child

Abstract

Muscle wasting and weakness are among the most common inherited and acquired disorders and include the muscular dystrophies, cachexia, and age-related wasting. Since there is no generally accepted treatment to improve muscle bulk and strength, these conditions pose a substantial burden to patients as well as to public health. Consequently, there has been considerable interest in a recently described inhibitor of muscle growth, myostatin, or growth/differentiation factor 8 (GDF-8), which belongs to the transforming growth factor β superfamily of secreted proteins that control the growth and differentiation of tissues throughout the body. The myostatin gene is expressed almost exclusively in cells of skeletal-muscle lineage throughout embryonic development as well as in adult animals and functions as a negative regulator of muscle growth.^1,2 Targeted disruption of the myostatin gene in mice doubles skeletal-muscle mass.¹ Conversely, systemic overexpression of the myostatin gene leads to a wasting syndrome characterized by extensive muscle loss.³ In adult animals, myostatin appears to inhibit the activation of satellite cells, which are stem cells resident in skeletal muscle.^4,5