Abstract
Purpose: :
The extraocular muscles (EOMs) represent an extreme example of skeletal muscle specialization. It is not surprising that transcriptional and biochemical studies of these muscles have identified many genes and proteins differentially expressed in EOMs compared to limb skeletal muscles. MicroRNAs (miRNAs) are small noncoding RNAs (21 to 26 nucleotides) that regulate gene expression by inhibiting mRNA translation or promoting mRNA degradation. Some miRNAs are tissue-specific and may influence the adult tissue phenotype. In this study, we tested the hypothesis that EOMs would have a unique miRNA expression profile that would include a combination of muscle-specific miRNAs.
Methods: :
We isolated EOMs and gastrocnemius muscles from adult male Sprague-Dawley rats for expression profiling using miRNA microarrays, real-time quantitative PCR, and northern blots.
Results: :
A total of 223 miRNAs were present in all muscle samples (out of 636 miRNAs). Fourteen miRNAs were more abundant in EOMs compared to gastrocnemius, and five were less abundant. Surprisingly, miR-206, previously demonstrated to be enriched in skeletal muscle, was significantly less abundant in EOM. miRNAs more abundant in EOM were miR-133a/b which have been found in skeletal muscle and heart. miRNAs found in brain were also increased in EOM: miR-24 and miR-30c. Ubiquitously expressed miRNAs, miR-143and and miR-320 were also upregulated in EOM.
Conclusions: :
The results support our initial hypothesis that EOMs have a specific miRNA expression profile, significantly different from that of a limb skeletal muscle. These EOM-enriched miRNAs may represent a hitherto unrecognized regulatory influence on the phenotype of these muscles.Supported by NEI EY12998
Keywords: gene microarray • gene/expression