Mice lacking microRNA 133a develop dynamin 2–dependent centronuclear myopathy

Area of Science:

• Molecular Biology
• Genetics
• Muscle Physiology

Background:

• MicroRNAs (miRNAs) are key regulators of gene expression, influencing cellular phenotypes by targeting messenger RNAs (mRNAs).
• Skeletal muscle function and homeostasis rely on intricate regulatory networks, including the roles of specific miRNAs.

Purpose of the Study:

• To investigate the essential roles of muscle-specific microRNAs miR-133a-1 and miR-133a-2 in maintaining adult skeletal muscle structure and function in mice.
• To explore the link between miR-133a dysregulation and the development of centronuclear myopathy.

Main Methods:

• Genetic deletion of miR-133a-1 and miR-133a-2 in mice.
• Analysis of skeletal muscle phenotypes, including myofiber type, mitochondrial function, and muscle triad structure.
• Investigation of the miR-133a target dynamin 2 mRNA expression.

Main Results:

• Mice lacking miR-133a-1 and miR-133a-2 developed adult-onset centronuclear myopathy, primarily affecting type II myofibers.
• Observed abnormalities included impaired mitochondrial function, a shift in myofiber type (fast-to-slow conversion), and disrupted muscle triads.
• These muscle defects were partly attributed to the dysregulation of dynamin 2 mRNA, a known target of miR-133a and implicated in human centronuclear myopathy.

Conclusions:

• miR-133a is essential for maintaining adult skeletal muscle integrity, function, bioenergetics, and myofiber identity.
• Dysregulation of miR-133a contributes to the pathogenesis of centronuclear myopathy.
• These findings highlight miR-133a as a potential therapeutic target for centronuclear myopathies.