MiR-1b up-regulation inhibits rat neuron proliferation and regeneration yet promotes apoptosis via targeting KLF7

Introduction
MicroRNA (miRNA) is known to be involved in nerve injury. Our study aimed to identify the role and mechanism of miR-1b in rat neuron proliferation, regeneration and apoptosis.

Material and methods
Neurons were successfully separated and identified using a microscope and immunofluorescence staining of microtubule-associated protein 2 (MAP-2). The expressions of miR-1b and Krüppel-like factor 7 (KLF7) were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Neuron viability and apoptosis were detected by MTT assay and flow cytometry, respectively. Neuron regeneration states were observed using a microscope and analysed by the ImageJ software. Expressions of C-caspase-3 and cell regeneration-related proteins (nerve growth factor [NGF], ciliary neurotrophic factor [CNTF] and brain-derived neurotrophic factor [BDNF]) were measured by Western blot. Target genes and potential binding sites of KLF7 and miR-1b were predicted by TargetScan 7.2 and confirmed by dual luciferase reporter assay.

Results
Neurons were identified as MAP-2-positive. Up-regulation of miR-1b reduced neuron viability and regenerative ability, promoted neuron apoptosis and C-caspase-3 expression, and down-regulated the expressions of cell regeneration-related proteins. KLF7 was the target gene of miR-1b. Overexpressed KLF7 rescued the effects of up-regulation of miR-1b on neuron viability, regeneration and apoptosis. Expressions of NGF, CNTF and BDNF were suppressed yet C-caspase-3 expression was up-regulated by miR-1b mimic, which was partially rescued by overexpressed KLF7.

Conclusions
Up-regulation of miR-1b promoted rat neuron proliferation and regeneration yet inhibited apoptosis via targeting KLF7.