Objective  To explore the roles of 2 microRNA molecules

miR-21and miR-22

in the myogenic differentiation of C2C12 myoblasts.   Methods  C2C12 cells was taken as the model since they have a tendency of myogenic differentiation when cultured in differentiation medium. The expression levels of miR-21 and miR-22 in the process of myogenic differentiation and different tissues (the brain

small intestine

skeleton muscle

spleen

kidneys

liver

heart and lungs) were detected by Northern blotting. Loss-of-function about these 2 microRNAs were carried out by transfecting the antisense strands of their DNA/locked nucleic acid (LNA) mixtures respectively and the effects on the expressions of 3 myogenic differentiation related genes

skeletal-α-actin

myogenin and myocyte enhancer factor-2D (MEF-2D) were evaluated by RT-PCR.   Results  These 2 microRNAs were strongly expressed during the differentiation of C2C12 cells and they had obvious expression profiles in different tissues. Comparing to negative control

inhibiting the up-regulation of miR-21 and miR-22 had no effect on the expressions of above mentioned genes.   Conclusion  miR-21 and miR-22 have little effects on the myogenic differentiation of the murine myoblast cell line C2C12.