About 9,500 people in the UK suffer from a form of myotonic dystrophy – a rare genetic disease affecting the neuromuscular system. Myotonic dystrophy type 1 (DM1) is the most frequent muscular dystrophy in adults, with an estimated prevalence of 1/8000. DM1 causes progressive muscle weakness and wasting, and a difficulty of muscles to relax after contraction; there is currently no cure for this debilitating and deadly neuromuscular disease.
Why is treating DM1 so challenging? On a molecular level, the disease is linked to a mutation in the DMPK gene. This genetic anomaly consists of an increase in the repeat number of a small three-nucleotide DNA sequence, which results in an accumulation of mutated DMPK RNA in the cell's nucleus. This in turn leads to a perturbation of the proper functioning of cells. Several rare genetic diseases may be treated using antisense oligonucleotides (synthesised RNA fragments) acting on the mutated RNA. However, in myotonic dystrophy type 1, unlike in other muscular dystrophies, the membrane barrier of muscle fibres is not weakened, which means that the antisense oligonucleotides cannot cross it easily. The reduced penetration leads to a reduced efficiency of the treatment.
Read more (MDUK Oxford Neuromuscular Centre website)