Duchenne muscular dystrophy is a lethal genetic disorder, caused by a defect in the DMD gene. This gene produces dystrophin, a protein essential to muscle function. Because of the gene defect, Duchenne muscular dystrophy causes progressive muscle weakness, leading to loss of ability to walk and early death after the muscle of the heart and lungs stops working properly. It also can cause learning difficulties and intellectual disability. Because of how the disease is inherited, only boys are affected, but girls can carry the gene and pass it on to their children.
The disease varies substantially in severity and response to treatment, which suggests that other genes or environmental factors can modify the effects of DMD. To explore this theory, researchers funded by the Intellectual and Developmental Disabilities Branch used two different groups of patients with Duchenne muscular dystrophy to identify additional genes that increase disease severity.
They found a mutation in the SPP1 gene that caused greater muscle weakness and more rapid disease progression. Of patients without this mutation, 20% could still walk at age 14. Of those with the mutation, none could still walk at this age.
The SPP1 mutation occurs in about 35% of Duchenne patients. Identifying it not only helps researchers understand how Duchenne and other muscular dystrophies progress, but also could be important in developing treatments for Duchenne muscular dystrophy (PMID: 21178099).