Expression of miR-1, miR-133a, miR-133b and miR-206 increases during development of human skeletal muscle

We examined the levels of miR-1, miR-133a, miR-133b and miR-206 during the development of human foetus. All four miRNA levels were found increased during late stages of human foetal muscle development. Increases in the expression levels of these miRNAs were proportional to the capacity of myoblasts to form myotubes. Changes in miRNA levels during human foetal development were accompanied by endogenous alterations in their known targets and also in their inducer, MyoD. Ectopic MyoD expression caused an induction of muscle cell differentiation in vitro, accompanied by an increase in the levels of miR-1, miR-133a, miR-133b and miR-206.This study provides data about the profile of four miRNAs in human muscle cells isolated during different stages of foetal development. These results may shed light on the differentiation of muscle cells and regulation of muscle formation through miRNAs, during the development of human foetus.MicroRNAs (miRNAs) are small (~22 nucleotides) non-coding RNAs that negatively regulate gene expression at the post-transcriptional level [1,2]. miRNAs bind to the 3' untranslated region (3'UTR) of their target mRNAs, causing either inhibition of protein translation or mRNA degradation [2]. During the last few years, intense research has revealed the regulatory role of miRNAs in almost all cellular processes, during health and disease [3-6].Skeletal myogenesis is a complex and tightly regulated developmental process that directs myoblasts to differentiate into mature myotubes. During myogenesis, myoblasts are stimulated to initiate the expression of myogenic differentiation-specific genes, withdraw from cell cycle and fuse together to form multinucleated myotubes, which are ultimately organized into myofibers [7]. Myogenesis occurs during embryogenesis in order to form muscle and in adults to replace lost or damaged muscle. Most embryonic skeletal myogenic progenitors arise from somites, which are masses of paraxial mesoderm distributed along the two