Although mature CNS axons do not spontaneously regenerate,conditioning injury to the peripheral branches of sensory neurons of the dorsal root ganglion can robustly upregulate regeneration-associated genes (RAGs) and thereby enhance axon regeneration after spinal cord injury.The mechanism by which conditioning injury regulates transcriptional activation of RAGs has not been fully understood.The present study sought to determine potential influence of DNA methylation on the transcriptional activation of RAGs in the conditioning injury-induced regeneration model.Methylated DNA immunoprecip-iation (MeDIP) was performed using DNA samples from L4-6 DRGs followed by next generation sequencing.The MeDIP-seq revealed that approximately 2,000 genes were hypermethylated and a similar number of genes were demethylated after condi-tioning injury.However,the extent of changes in the level of DNA methylation was not correlated with gene expression levels measured by RNA-seq in most genes,including the RAGs.Interestingly,pharmacological inhibition (5-aza-2-deoxycytidine,5-aza) or activation (S-Adenosylmethionine,SAM) of DNA methylation significantly decreased neurite outgrowth potentials in preconditioned sensory neurons of the dorsal root ganglion.To examine the effects of pharmacological perturbation of DNA methylation on RAG expression,we performed a PCR array customized for 44 RAGs reported in literatures.We found that both 5-aza and SAM treatment led to robust upregulation of Socs3 and Serpine1 genes accompanied by downregulation of well-known growth promoting genes such as Gap-43 and Sprr1a.These findings suggest that alteration of global DNA methylation does not influence axon growth in the presence of preconditioning injury.However,these effects do not seem to be mediated by direct regulation of transcriptional activity of RAGs.