Phenotypic Drug Screening for Dysferlinopathy Using Patient-Derived Induced Pluripotent Stem Cells

Area of Science:

• Muscle biology and regenerative medicine
• Genetics of neuromuscular disorders
• Stem cell applications in disease modeling

Background:

• Dysferlinopathy, encompassing limb-girdle muscular dystrophy type 2B and Miyoshi myopathy, results from mutations in the dysferlin (DYSF) gene.
• Dysferlin's critical role is in resealing the muscle membrane after injury.
• Previous research indicated proteasome inhibitors like MG-132 could restore membrane resealing function by increasing misfolded dysferlin in fibroblasts.

Purpose of the Study:

• To develop a screening system for identifying therapeutic compounds for dysferlinopathy using patient-derived cells.
• To identify small molecules that can restore the membrane resealing function in dysferlinopathy models.

Main Methods:

• Established a screening system utilizing myocytes derived from induced pluripotent stem cells of Miyoshi myopathy patients.
• Screened for compounds that increase dysferlin levels and enhance membrane resealing.
• Investigated the cellular mechanisms underlying the observed increase in dysferlin, including microtubule dynamics and degradation pathways (proteasome vs. autophagy).

Main Results:

• Nocodazole was identified as a compound that significantly increases dysferlin levels in patient-derived myocytes.
• Increased dysferlin levels mediated by nocodazole enhanced the membrane resealing capacity following laser-induced injury.
• The mechanism involves nocodazole-induced microtubule disorganization and activation of the autophagy pathway, not proteasomal degradation.

Conclusions:

• Small molecules that increase the amount of functional, albeit misfolded, dysferlin represent a promising therapeutic strategy for dysferlinopathy.
• Nocodazole's effect on dysferlin levels and membrane repair highlights autophagy as a potential therapeutic target for this genetic muscle disorder.