MicroRNA-212 inhibits oligodendrocytes during maturation by down-regulation of differentiation-associated gene expression

MicroRNA-212 (mir-212) has been reported to regulate neuronal development and functioning. However, its expression and function in glia are not yet known. Here, we demonstrate that the level of microRNA-212 (mir-212) was reduced in spinal cord lesion site at 1 week and 1 month after a contusive spinal cord injury. In addition to its expression in neurons, mir-212 expression was detected in oligodendrocytes (OLGs) and glial progenitor cells (GPCs) in adult CNS. The addition of antagomir-212 to reduce mir-212 expression enabled to improve the cell process outgrowth of OLGs along with the up-regulation of the genes associated with OLG differentiation and maturation, including OLIG1, SOX10, myelin basic protein (MBP), and proteolipid protein 1 (PLP1). In contrast, these genes were significantly down-regulated by an increased expression of mir-212 in GPCs or in OLG progenitor cells (OPCs) through lentivirus-mediated gene delivery approach. Moreover, we found that PLP1 was the direct target molecule of mir-212. Furthermore, mir-212 over-expression diminished the protein production of OLGs markers including 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase), MBP, and PLP. Additionally, mir-212 over-expression decreased the number of mature OLGs expressing MBP, and the expression of galactocerebroside (GC). Complementary studies in a hippocampal neuron-OLG co-culture model and an ex vivo cerebellar slice system indicated that OLGs derived from GPCs with mir-212 over-expression exhibited decreased ability to interact with neuronal axons. Collectively, our findings demonstrate that mir-212 repressed the expression of OLG maturation-associated proteins and inhibited OLG cell process extension, indicating that mir-212 has negative regulatory effect on OLG lineage progression.