Alteration in global DNA methylation status following preconditioning injury influences axon growth competence of the sensory neurons

Preconditioning peripheral nerve injury primes the sensory neurons in the dorsal root ganglia(DRGs) to acquire axon regeneration competence. Transcription of a large set of regenerationassociated-genes (RAGs) contributes to the enhanced intrinsic axonal regeneration capacity.However, the mechanism underlying the coordinated upregulation of RAGs orchestrated by preconditioning injury is unclear. We sought to determine the potential influence of DNA methylation change on transcriptional activation of RAGs in the L4-L6 DRGs following sciaticnerve injury. Genome-wide sequencing revealed that about 20% of the methylated DNA fragments were differentially methylated, and more than 3000 genes contained differentially methylated regions. Not only demethylation but also increased methylation was observed to a similar extent. The change in the global DNA methylation did not correlate with the gene expression level of most genes, including the well-documented RAGs. However, pharmacological inhibition or activation of DNA methylation markedly attenuated the axon growth capacity of the preconditioned DRG neurons. Pharmacological inhibition or activation ofDNA methylation resulted in the simultaneous downregulation of many highly overlapping nontranscription factor RAGs, which was accompanied by a concurrent, robust upregulation of SOCS3 and Serpine1. Overexpression of SOCS3 and Serpine1 in the DRG neurons overrode injury-induced axon growth competence, corroborating their roles as the negative regulators of axon regeneration. We conclude that the injury-induced global alteration of DNA methylome strongly influences the axon growth competence in preconditioned DRG neurons. Perturbing DNA methylome changes may lead to the upregulation of negative regulator RAGs thereby attenuating axon growth capacity