Difference in potential DNA methylation impact on gene expression between fast- and slow-type myofibers

Area of Science:

• Molecular Biology
• Epigenetics
• Muscle Physiology

Background:

• Skeletal muscles consist of fast and slow myofiber types.
• Epigenetic mechanisms are hypothesized to maintain muscle fiber-type specificity but remain poorly understood.

Purpose of the Study:

• To investigate the role of CpG methylation in maintaining skeletal muscle fiber-type specificity.
• To analyze differences in DNA methylation patterns between fast and slow muscle fibers.

Main Methods:

• Reduced representation of bisulfite sequencing (RRBS) was employed for comprehensive CpG methylation analysis.
• GFP-myh7 mouse model used to visually distinguish and isolate slow-type and fast-type fibers.
• Analysis of differentially methylated CpGs and their association with gene expression.

Main Results:

• Significant differences in CpG methylation were observed between fast and slow fibers (31,967 and 26,274 CpGs, respectively).
• Promoter hypermethylation was associated with downregulated gene expression, particularly in slow-type fibers (3.5 times higher).
• Gene body hypermethylation of specific myofibrillar genes correlated with downregulated expression, suggesting regulation of gene expression and alternative promoter usage.

Conclusions:

• CpG methylation, particularly gene body methylation, plays a role in myofiber type-specific gene expression and alternative promoter usage.
• Promoter hypermethylation has a dominant effect on gene expression in slow myofibers.
• Epigenetic regulation via DNA methylation is crucial for maintaining skeletal muscle fiber identity.