A team of US scientists has developed a new gene therapy treatment for Duchenne muscular dystrophy (DMD), a severe inherited muscle-wasting disease. The researchers successfully treated laboratory mice with the condition, stopping and even reversing its symptoms. The study, carried out at the University of Pittsburgh, was published in the Proceedings of the National Academy of Sciences.
People with severe DMD lack a working copy of a gene called dystrophin, which is vital for normal muscle development. The disease causes progressive muscle weakness, and those affected usually die in their early twenties. The majority of patients are boys, as the dystrophin gene is located on the X chromosome (female carriers are usually unaffected, as a working copy of the gene on one of their X-chromosomes masks the effect of the defective gene on the other).
Efforts to treat DMD by delivering a working copy of the dystrophin gene to the affected muscles have been hampered by its unusual size - it is the largest known gene. Composed of 14 kilobases (kb) of DNA, the full-length gene is too large to package into any of the viruses used to deliver genes to affected tissues. But the Pittsburgh team managed to trim the essential features of the dystrophin gene down to a mere 4.2kb, small enough to fit into an adeno-associated virus. Team leader Dr Xiao Xiao said he hoped the strategy could be used to treat patients 'within several years'. He said the mice treated with the mini-dystrophin gene showed no evidence of muscle breakdown many months after treatment, even following exercise.
Sources and References
Gene implant hope for wasting disease
Muscle disease advance