MicroRNAs 93-5p, 106b-5p, 17-5p, and 140-5p target the expression of early growth response protein 2 in Schwann cells.

Early growth response protein 2 (EGR2) is an essential transcription factor for peripheral nerve myelination. Schwann cells (SCs), the peripheral myelin-forming glial cells, express high levels of EGR2 during postnatal myelination. In contrast, SCs exhibit low EGR2 expression during Wallerian degeneration after injury. In this study, we screened 10 potential microRNAs (miRNAs) (20a-5p, 137-5p, 140-5p, 148b-3p, 150-5p, 17-5p, 93-5p, 20b-5p, 106b-5p, and 152-3p) that potentially target EGR2 using miRNA algorithms and identified that miRNAs 106b-5p, 140-5p, 93-5p, and 17-5p target EGR2 in SCs. These miRNAs directly target EGR2 by binding to the 3'-untranslated region to suppress EGR2 mRNA levels. Additionally, the levels of miRNAs 93-5p, 106b-5p, 17-5p, and 140-5p were decreased in the sciatic nerves during postnatal development; however, these miRNAs were increased on day 1 after sciatic nerve injury. Taken together, these findings suggest that the expression of EGR2 during postnatal development and Wallerian degeneration could be regulated by the inverse expression of miRNAs 106b-5p, 140-5p, 93-5p, and 17-5p, which target EGR2.