Silencing the enhancer of zeste homologue 2, Ezh2, represses axon regeneration of dorsal root ganglion neurons

Abstract

Recovery from injury to the peripheral nervous system is different from that of the central nervous system in that it can lead to gene reprogramming that can induce the expression of a series of regeneration-associated genes. This eventually leads to axonal regeneration of injured neurons. Although some regeneration-related genes have been identified, the regulatory network underlying axon regeneration remains largely unknown. To explore the regulator of axon regeneration, we performed RNA sequencing of lumbar L4 and L5 dorsal root ganglion (DRG) neurons at different time points (0, 3, 6, 12 hours, 1, 3 and 7 days) after rat sciatic nerve crush. The isolation of neurons was carried out by laser capture microscopy combined with NeuN immunofluorescence staining. We found 1228 differentially expressed genes in the injured sciatic nerve tissue. The hub genes within these differentially expressed genes include Atf3, Jun, Myc, Ngf, Fgf2, Ezh2, Gfap and Il6. We verified that the expression of the enhancer of zeste homologue 2 gene (Ezh2) was up-regulated in DRG neurons after injury, and this up-regulation differed between large- and small-sized dorsal root ganglion neurons. To investigate whether the up-regulation of Ezh2 impacts axonal regeneration, we silenced Ezh2 with siRNA in cultured DRG neurons and found that the growth of the newborn axons was repressed. In our investigation into the regulatory network of Ezh2 by interpretive phenomenal analysis, we found some regulators of Ezh2 (including Erk, Il6 and Hif1a) and targets (including Atf3, Cdkn1a and Smad1). Our findings suggest that Ezh2, as a nerve regeneration-related gene, participates in the repair of the injured DRG neurons, and knocking down the Ezh2 in vitro inhibits the axonal growth of DRG neurons. All the experimental procedures approved by the Administration Committee of Experimental Animals of Jiangsu Province of China (approval No. S20191201-201) on March 21, 2019.

Keywords

• axon regeneration; dorsal root ganglion neurons; ezh2; ib4; laser capture microscopy; nf160/200; quantitative reverse transcription-polymerase chain reaction; sciatic nerve crush; scrna-seq; sirna