The neuronal membrane glycoprotein M6a (GPM6A) belongs to the family of myelin proteolipid protein and plays a role in neuronal remodeling and plasticity. Decreased expression of GPM6A mRNA is observed in the hippocampal tissue of suicide victims who suffered from depression and after chronic stress exposure in animals. The regulatory mechanisms that impact expression of GPM6A under chronic stress or in pathological conditions are not well understood. Previously, miRNAs miR-133b, miR-124-3p, and miR-9-5p have been shown to regulate the expression of Gpm6a mRNA under normal conditions. Here, we employed the paradigm of chronic-restraint stress in rats and using quantitative polymerase chain reaction (qPCR) showed down-regulation of expression of Gpm6a and the brain-derived neurotrophic factor (Bdnf) genes at mRNA level as well as miR-133b, and miR-124-3p, but not miR-9-5p in the hippocampus of chronically stressed rats. Furthermore, we observed alterations in the expression of histone deacetylase (Hdac5) and myocyte enhancer factor 2C (Mef2c) mRNAs. Our data suggest that chronic stress influences Gpm6a expression by miR-124-mediated impact on the expression of Hdac5 and Mef2c. Upon miR-124 over-expression in hippocampal neurons cultured in vitro, we observed enhanced neuronal arborization as evaluated by Sholl analysis, increased Gpm6a and Mef2c expression, and decreased Hdac5 expression. Moreover, treatment of hippocampal neurons cultured in vitro with BDNF resulted in an elevation in the miR-124-3p expression, a decrease in the miR-9-5p expression but did not affect miR-133b. This was accompanied by augmented expression of Gpm6a and Mef2c mRNAs and significantly lower levels of Hdac5 mRNA. Altogether, these results indicate that the regulatory mechanism that influence expression of Gpm6a under chronic stress involves miR-124-mediated impact on the expression of Hdac5 and Mef2c and a role of BDNF in the activation of Gpm6a expression.
Keywords: chronic stress; hippocampus; membrane glycoprotein M6a; microRNAs; primary hippocampal neuron; rat.
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