Diaphragm displays early and progressive functional deficits in dysferlin-deficient mice

Area of Science:

• Biomedical research
• Muscle physiology
• Animal models of disease

Background:

• Dysferlin deficiency causes limb girdle muscular dystrophy 2B and Miyoshi myopathy.
• Current animal models exhibit slow pathology progression, hindering therapeutic screening.
• A functional signature for dysferlin-lacking skeletal muscles is needed.

Purpose of the Study:

• To identify a functional signature in skeletal muscles lacking dysferlin.
• To assess the utility of the A/J mouse model for dysferlinopathy research.
• To determine if diaphragm deficits can accelerate therapeutic evaluation.

Main Methods:

• Isolated limb muscles and diaphragm from 10- and 36-week-old A/J and control mice were analyzed.
• Measurements included force generation and susceptibility to eccentric contractile injury.
• Fiber-specific analysis identified myosin heavy chain 2A-expressing fibers in the diaphragm.

Main Results:

• Limb muscles maintained normal specific force at both ages.
• The diaphragm exhibited significant deficits in specific force and eccentric injury susceptibility.
• Diaphragm membrane ruptures during eccentric contractions occurred in myosin heavy chain 2A fibers.
• Dysferlin content did not correlate with disease severity across wildtype muscles.

Conclusions:

• The diaphragm, unlike limb muscles, shows early functional deficits in A/J mice.
• These early diaphragm deficits may reduce the required age for therapy evaluation.
• The A/J mouse diaphragm presents a promising model for accelerated dysferlinopathy research.