A novel dysferlin mutant pseudoexon bypassed with antisense oligonucleotides

Area of Science:

• Genetics
• Molecular Biology
• Neuromuscular Disorders

Background:

• Dysferlin (DYSF) protein is crucial for muscle membrane repair and T-tubule function.
• Mutations in DYSF cause various muscular dystrophies, including Miyoshi myopathy and limb-girdle muscular dystrophy type 2B.
• Over 330 pathogenic DYSF mutations are known, but some patients with muscular dystrophy have only one identified mutation.

Purpose of the Study:

• To identify the genetic cause of muscular dystrophy in a family with a known DYSF mutation.
• To investigate potential therapeutic strategies for DYSF-related muscular dystrophies.

Main Methods:

• Sequencing of the full DYSF cDNA to identify genetic defects.
• Investigating antisense oligonucleotides (AONs) to correct aberrant mRNA splicing.

Main Results:

• A novel pseudoexon (PE44.1) was identified, inserting 177 nucleotides into DYSF mRNA and altering the C2F protein domain.
• This PE44.1 mutation was found in two unrelated patients with dysferlinopathy.
• AONs targeting PE44.1 successfully blocked abnormal splicing, restoring normal DYSF mRNA and increasing DYSF protein expression in vitro.

Conclusions:

• This study reports the first deep intronic DYSF mutation causing a pseudoexon insertion affecting mRNA splicing.
• AON-mediated exon-skipping demonstrated the potential to restore functional DYSF protein production in patient cells.
• This approach offers a promising therapeutic strategy for dysferlinopathies and a foundation for targeting other DYSF mutations.