Myopathic changes in murine skeletal muscle lacking synemin

Area of Science:

• Muscle physiology
• Cell biology
• Biochemistry

Background:

• Intermediate filament (IF) proteins are crucial for muscle structure and function.
• Defects in IF proteins can disrupt the contractile apparatus and costamere links in striated muscle.

Purpose of the Study:

• To investigate the role of synemin, a type IV IF protein, in skeletal muscle function.
• To analyze the effects of synemin deficiency on muscle phenotype and mechanical properties.

Main Methods:

• Examined mice lacking synemin (synm-null mice).
• Assessed skeletal muscle phenotype, including fiber diameter, force production, and injury susceptibility.
• Utilized elastimetry to measure sarcolemmal tension and deformability.

Main Results:

• Synm-null mice exhibited decreased mean fiber diameter and reduced twitch/tetanic force in tibialis anterior muscles.
• These mice showed increased susceptibility to injury from lengthening contractions.
• Sarcolemmal tension was reduced, indicating increased deformability, though contractile apparatus organization remained unaltered.
• Fatigue was more pronounced, but treadmill running performance was comparable to controls.

Conclusions:

• Synemin contributes to the linkage between costameres and the contractile apparatus in skeletal muscle.
• Absence of synemin leads to reduced fiber size, increased sarcolemmal deformability, and heightened susceptibility to muscle injury.
• Synemin plays a distinct, moderate role in fast-twitch skeletal muscle function.