Epitranscriptomic Analysis of m6A Methylome After Peripheral Nerve Injury.

Lei Zhang,Zihao Liu,Guangyuan Tian,Jia Qin,Xianhu Zhou,Pengyi Ma,Boyuan Ma,Dingyu Hao

doi:10.3389/fgene.2021.686000

Abstract

N6-methyladenosine (m6A) is one of the most plentiful internal RNA modifications, especially in eukaryotic messenger RNA (mRNA), which plays pivotal roles in the regulation of mRNA life cycle and nerve development. However, the mRNA m6A methylation pattern in peripheral nervous injury (PNI) has not been investigated. In this study, sciatic nerve samples were collected from 7 days after sciatic nerve injury (SNI) and control rats. Quantitative real-time PCR demonstrated that m6A-related methyltransferase/demethylase genes were remarkably upregulated in SNI group compared with control group. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) was performed to reveal the m6A methylation landscape. The results showed that 4,014 m6A peaks were significantly altered, including 2,144 upregulated and 1,870 downregulated m6A peaks, which were corresponded to 1,858 genes. Moreover, 919 differentially expressed genes were identified by the conjoint analysis of MeRIP-seq and RNA-seq. GO and KEGG pathway analyses were performed to determine the biological functions and signaling pathways of the m6A-modified genes. Notably, these genes were mainly related to the immune system process, cell activation, and nervous system development in GO analysis. KEGG pathway analysis revealed that these genes were involved in the cell cycle, B cell receptor signaling pathway, axon guidance pathway, and calcium signaling pathway. Furthermore, the m6A methylation and protein expression levels of autophagy-related gene (Atg7) were increased, together with the activation of autophagy. These findings shed some light on the epigenetic regulation of gene expression, which may provide a new opinion to promote functional recovery after PNI.

Highlights

Peripheral nerve repair following injury is a complicated process
Schwann cells secrete various trophic factors that accelerate axon regeneration coincided with the recruitment of immune cells to the nerve injury sites (Gaudet et al, 2011; Richner et al, 2014)
The ubiquitous expression of these genes indicates that m6A plays a prominent role during sciatic nerve injury (SNI)

Summary

Introduction

Peripheral nerve repair following injury is a complicated process. The distal stump of injured nerve undergoes Wallerian degeneration due to the loss of nutrition and energy support (Waller, 1851; Stoll et al, 2002). Neuronal apoptosis/necrosis and axon disintegration may induce the dedifferentiation and reprogramming of Schwann cells The injury-induced Schwann cells can proliferate to form Bungner’s bands that establish connections between broken stumps and guide the direction of axon regeneration (Waller, 1851). Schwann cells secrete various trophic factors that accelerate axon regeneration coincided with the recruitment of immune cells (neutrophils, macrophages, and T lymphocytes) to the nerve injury sites (Gaudet et al, 2011; Richner et al, 2014). On the 7th day after peripheral nerve injury (PNI), the number and proliferative activity of activated Schwann cells attain the highest level (Zhou et al, 2017). The recovery of motor and sensory functions is limited in some patients with severe PNI, and the molecular mechanisms underlying this phenomenon are still unclear

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Conclusion