The RNA-binding protein Rbfox1 regulates splicing required for skeletal muscle structure and function

Area of Science:

• Molecular Biology
• Genetics
• Muscle Physiology

Background:

• Rbfox proteins are conserved RNA-binding proteins crucial for alternative splicing (AS).
• Skeletal muscle exhibits extensive AS, necessitating tissue-specific protein isoforms.
• Rbfox1 is found in muscle and linked to neurological disorders, but its muscle-specific role is unclear.

Purpose of the Study:

• To investigate the function of Rbfox1 in adult skeletal muscle.
• To determine the impact of Rbfox1 deletion on muscle regeneration and physiology.

Main Methods:

• Developed a conditional knockout mouse model to delete Rbfox1 in adult muscle.
• Utilized deep sequencing to identify aberrant splicing events.
• Performed electron microscopy and immunostaining for ultrastructural analysis.
• Assessed muscle force generation and calcium handling.

Main Results:

• Rbfox1 is required for normal muscle function, but not for muscle regeneration in satellite cells.
• Loss of Rbfox1 leads to aberrant splicing of genes involved in myofibrillar structure, cytoskeleton, and calcium handling.
• Ultrastructural analysis revealed tubular aggregates and mislocalization of sarcoplasmic reticulum proteins (Serca1, Ryr1).
• Calcium handling and muscle force generation were significantly impaired in Rbfox1-deficient muscle.

Conclusions:

• Rbfox1 plays a critical role in maintaining skeletal muscle physiology.
• Rbfox1 regulates a network of AS events essential for myofibrillar integrity, calcium homeostasis, and muscle function.