Targeting neurodevelopmental miR132-3p promotes neuroprotection and axon regeneration after optic nerve injury in mice.

Micro-RNA (miRNA) miR-132 regulates the axonal elongation-to-branching switch in central nervous system (CNS) neurons during maturation, which coincides with the mammalian developmental loss of CNS projection neurons' intrinsic axon growth capacity. However, it is unknown whether experimental targeting of miR-132 in mature CNS neurons could activate elongation/regeneration of the axons severed by an injury. Here, we characterized miR-132 5p and 3p arm expression during maturation of a prototypical CNS projection neuron, the retinal ganglion cell (RGC), and then tested whether miR-132 arm-specific knockdown (KD) in the RGCs activates elongation/regeneration of axons severed by optic nerve crush (ONC) injury in vivo. We identified the miR132-3p arm as developmentally-upregulated in the RGCs and found that its KD modestly but significantly promoted RGC axon-regeneration and survival. We also gained insights into the miR132-3p KD-regulated biological processes by transcriptomic profiling of the treated injured RGCs, which showed enrichment of a developmental gene network for formation of axonal projections. Thus, neuronal miR132-3p plays a role in axon regeneration after optic nerve injury, and future studies should investigate the underlying mechanisms.