Is the myonuclear domain size fixed?

Area of Science:

• Muscle physiology
• Cell biology
• Skeletal muscle adaptation

Background:

• The myonuclear domain theory posits a constant cytoplasmic volume per myonucleus in muscle fibers.
• This theory suggests myonuclear number scales with fiber size.

Purpose of the Study:

• To critically evaluate the concept of a constant myonuclear domain size.
• To investigate factors influencing myonuclear domain size variation in skeletal muscle.

Main Methods:

• Review of existing literature on muscle fiber growth, atrophy, and aging.
• Analysis of myonuclear number and fiber size relationships across different conditions.

Main Results:

• Myonuclear domain size varies significantly between different muscle fiber types.
• Oxidative capacity of a muscle fiber is inversely related to its myonuclear domain size.
• Myonuclear domain size increases during maturational growth and overload-induced hypertrophy.
• Myonuclear domain size decreases during disuse- and aging-associated muscle atrophy.

Conclusions:

• The concept of a constant myonuclear domain size requires cautious interpretation.
• Acquisition of new myonuclei is necessary for further muscle hypertrophy once the myonuclear domain size exceeds a specific threshold.