Molecular pathology of myofibrillar myopathies

Area of Science:

• Muscle biology
• Genetics
• Molecular pathology

Background:

• Myofibrillar myopathies (MFMs) are a diverse group of inherited muscle disorders.
• They are characterized by the breakdown of myofibrils and accumulation of protein aggregates within muscle cells.
• MFMs serve as a key model for understanding conformational protein diseases affecting skeletal and cardiac muscles.

Purpose of the Study:

• To review the genetic and clinical features of MFMs caused by mutations in Z-disc proteins.
• To summarize current understanding of the molecular mechanisms underlying muscle fiber degeneration in MFMs.
• To highlight the role of impaired protein degradation pathways in MFM pathogenesis.

Main Methods:

• Literature review of genetic and clinical studies on MFMs.
• Analysis of molecular pathogenic mechanisms, including protein aggregation and degradation pathways.
• Focus on mutations in genes encoding Z-disc proteins such as desmin, alphaB-crystallin, myotilin, ZASP, and filamin C.

Main Results:

• Identification of causative mutations in multiple genes, primarily encoding sarcomeric Z-disc proteins.
• Recognition of defective extralysosomal protein degradation as a critical factor in muscle fiber degeneration.
• Involvement of factors like mutant proteins, impaired ubiquitin-proteasome system, aggresome formation, and oxidative stress in MFM pathology.

Conclusions:

• Defects in Z-disc proteins lead to a spectrum of myofibrillar myopathies.
• Impaired protein clearance mechanisms are central to the pathogenesis of MFMs.
• Further research into these pathways may reveal therapeutic targets for muscle degeneration.