title: MicroRNA-1 and microRNA-133a expression are decreased during skeletal muscle hypertrophy.
abstract: MicroRNAs (miRNAs) are a class of highly conserved, noncoding RNAs involved in posttranscriptional gene regulation. A small number of muscle-specific miRNAs have been identified and shown to have a role in myoblast proliferation and differentiation as well as embryonic muscle growth. The primary objective of the present study was to determine the expression level of the muscle-specific miRNAs in the soleus and plantaris muscles and whether their expression in the plantaris was altered in response to functional overload. Of the miRNAs examined, only miRNA-206 was differentially expressed between soleus and plantaris muscles, as reflected by the sevenfold higher expression in the soleus for both the primary miRNA (pri-miRNA) and mature miRNA (miR). Following 7 days of functional overload, transcript levels for both pri-miRNA-1-2 and pri-miRNA-133a-2 increased by approximately 2-fold, whereas pri-miRNA-206 levels were elevated 18.3-fold. In contrast, expression of miR-1 and miR-133a were downregulated by approximately 50% following overload. The discrepancy between pri-miRNA and miR expression following overload was not explained by a change in the expression of components of the miRNA biogenesis pathway, since Drosha and Exportin-5 transcript levels were significantly increased by 50% in response to functional overload, whereas Dicer expression remained unchanged. These results are the first to report alterations in expression of muscle-specific miRNAs in adult skeletal muscle and suggest miRNAs may have a role in the adaptation to functional overload.
authors.affiliation: Department of Physiology, University of Kentucky Medical Center, 800 Rose St., Lexington, KY 40536-0298, USA. jjmcca2@uky.edu
authors.forename: John J
authors.initials: JJ
authors.lastname: McCarthy
authors.forename: Karyn A
authors.initials: KA
authors.lastname: Esser
mesh_terms: D000818:Animals; D005786:Gene Expression Regulation; D006984:Hypertrophy / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology*; D010641:Phenotype; D010805:Physical Conditioning, Animal / Q000502:physiology; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism
chemical_list: D028884:Karyopherins; D035683:MicroRNAs; C517731:Mirn1 microRNA, mouse; C517732:Mirn133 microRNA, mouse; C499175:Xpo5 protein, mouse; C513400:Drosha protein, mouse; D043244:Ribonuclease III