Potential role of microRNA: Identification and functional analysis of microRNA in corticospinal tract after unilateral lesions of the medullary pyramid

Corticospinal tract is mainly descending tracts by dominating voluntary movement of the limbs and fine movement of distal limb, especially in mammals. Distal axonal degeneration is called anterograde degeneration. Proximal end is connected to the neuron cell body, whereas retrograde degeneration is very slight with the possibility of regeneration. MicroRNAs (miRNAs) are a short non-coding RNAs that regulate gene expression at the post-transcriptional level by binding with the 3′ untranslated region of target mRNAs. In order to understand the mechanism of underlying gene alteration in the rostral and caudal, respectively, after the corticospinal tract injury, we analyzed rostral and caudal mRNA and miRNA, respectively, using microRNA and mRNA profiles. We combined the predicted targets of miRNA with differentially expressed mRNA for selecting intersection gene. To predict the function miRNAs, GO and KEGG enrichment analysis were performed to find genes associated with change of rostral and caudal, respectively. The bioinformatics analysis indicated that changes in miRNA and target mRNA expression affected rostral regeneration, including negative regulation of apoptosis, positive regulation of cell proliferation, cell adhesion, oligodendrocyte development etc. It also affected caudal degeneration, including induction of apoptosis, down-regulating nervous system development, immune response etc. The current results illustrated that corticospinal tract injury produces a wide range changes of miRNAs, whereas mRNA also showed significantly change which affects key biological processes after injury in rostral and caudal.