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 regeneration-associated-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 potential influence of DNA methylation change on transcriptional activation of RAGs in the L4-L6 DRGs following sciatic nerve injury. Genome-wide sequencing revealed that about 20% of the methylated DNA fragments were differentially methylated, and >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 perturbation of DNA methylation resulted in simultaneous downregulation of many highly overlapping non-transcription 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. Our results also suggest a possibility that perturbing DNA methylome changes might lead to the upregulation of negative regulator RAGs thereby attenuating axon growth capacity.

中文翻译：

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预适应性损伤后总体DNA甲基化状态的改变影响感觉神经元的轴突生长能力。

预处理周围神经损伤可启动背根神经节（DRGs）中的感觉神经元，以获取轴突再生能力。大量的再生相关基因（RAGs）的转录有助于增强内在的轴突再生能力。然而，由预适应性损伤导致的RAGs协同上调的潜在机制尚不清楚。我们试图确定坐骨神经损伤后L4-L6 DRG中DNA甲基化变化对RAGs转录激活的潜在影响。全基因组测序表明，甲基化的DNA片段中约有20％被甲基化，而超过3000个基因包含甲基化区域。不仅观察到了脱甲基，而且观察到了甲基化的增加。总体DNA甲基化的变化与大多数基因的基因表达水平无关，包括有据可查的RAG。但是，药理学抑制或DNA甲基化的激活明显减弱了预处理的DRG神经元的轴突生长能力。DNA甲基化的药理学扰动导致许多高度重叠的非转录因子RAGs同时下调，同时伴随着SOCS3和Serpine1的同时强烈上调。DRG神经元中SOCS3和Serpine1的过表达会覆盖损伤诱导的轴突生长能力，从而证实了它们作为轴突再生的负调节剂的作用。我们得出的结论是，损伤引起的DNA甲基化组整体变化强烈影响预处理DRG神经元中的轴突生长能力。