Developmental expression and evolution of muscle-specific microRNAs conserved in vertebrates

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Molecular Genetics

Background:

• MicroRNAs (miRs) are small non-coding RNAs crucial for tissue-specific gene regulation.
• miR-1, miR-206, and miR-133 are key regulators of vertebrate myogenesis, encoded in bicistronic gene clusters.
• Understanding the evolutionary history of these miRs is vital for comprehending muscle development diversity.

Purpose of the Study:

• To investigate the evolutionary trajectory of miR-1, miR-206, and miR-133 gene organization and function.
• To identify and characterize homologous miRs in diverse vertebrate taxa, including cyclostomes, chondrichthyans, and teleosts.
• To examine the developmental expression patterns of these miRs across different vertebrate groups.

Main Methods:

• Bioinformatic identification of miR-1, miR-206, and miR-133 homologues across various vertebrate species.
• Comparative genomic analysis of gene clusters and synteny conservation.
• Expression analysis of miRs in different muscle tissues during embryonic and adult stages in model organisms like medaka.

Main Results:

• Cyclostomes and chondrichthyans possess fewer miR-1/miR-133 genes compared to teleosts like medaka.
• miR-206 was present in medaka but absent in chondrichthyans and lampreys, indicating lineage-specific gain.
• Conserved synteny was observed for miR-1(206)/miR-133 clusters across vertebrates, suggesting ancient genomic organization.
• miR-1 and miR-133 exhibited conserved expression in skeletal and cardiac muscle across lamprey, shark, and medaka.
• Differential expression of miR-1 and miR-206 was noted in medaka embryonic muscles, highlighting functional divergence.

Conclusions:

• The miR-1/miR-133 and miR-206 gene families have undergone duplications and functional diversification throughout vertebrate evolution.
• Conserved genomic organization and expression patterns suggest ancient roles in myogenesis, while differential expression points to adaptation.
• These muscle-specific miRs have played a significant role in shaping the diverse musculature observed in vertebrates.