m6A mRNA methylation is essential for oligodendrocyte maturation and CNS myelination

Oligodendrocytes are responsible for myelin formation and axonal trophic support in the vertebrate CNS. While a number of factors have been discovered that regulate oligodendrocyte lineage progression, the exact molecular mechanisms involved in this process remain unclear. Emerging studies have shown that N6-methyladenosine (m6A), the most common internal RNA modification of mammalian mRNA, plays a critical role in various developmental processes. In this study, we demonstrate that oligodendrocyte lineage progression is accompanied by changes in m6A modification on numerous transcripts. In vivo conditional inactivation in oligodendrocyte lineage cells of an essential m6A writer component, METTL14, results in decreased oligodendrocyte numbers and CNS hypomyelination, although oligodendrocyte precursor cell (OPC) numbers are normal. In vitro Mettl14 ablation disrupts post-mitotic oligodendrocyte maturation. In addition, Mettl14 ablation has distinct effects on OPC and oligodendrocyte transcriptomes. Together, our findings indicate that dynamic RNA methylation plays a critical regulatory role in oligodendrocyte development and CNS myelination. Illumina TruSeq stranded mRNA libraries prepared for m6A-seq in three replicates by Illumina HiSseq 4000 platform. Each processed data file was generated from both IP and input samples and is linked to the corresponding IP sample records.

少突胶质细胞（oligodendrocytes）负责脊椎动物中枢神经系统（CNS）的髓鞘形成与轴突营养支持。尽管目前已发现多种调控少突胶质细胞谱系发育进程的因子，但该过程的确切分子机制仍未明确。新兴研究显示，N6-甲基腺嘌呤（N6-methyladenosine, m6A）作为哺乳动物mRNA最常见的内部RNA修饰类型，在多种发育过程中发挥关键调控作用。本研究证实，少突胶质细胞谱系发育进程伴随大量转录本上的m6A修饰水平变化。在少突胶质细胞谱系细胞中条件性失活m6A写入复合物的核心组分METTL14，虽少突胶质前体细胞（OPC）数量保持正常，但会导致少突胶质细胞数目减少及中枢神经系统髓鞘发育不良。体外实验中敲除Mettl14会破坏有丝分裂后少突胶质细胞的成熟过程。此外，敲除Mettl14对少突胶质前体细胞和少突胶质细胞的转录组具有显著不同的调控效应。综上，本研究结果表明动态RNA甲基化在少突胶质细胞发育及中枢神经系统髓鞘形成中发挥关键调控作用。本研究通过Illumina HiSseq 4000平台，为m6A测序构建了3个生物学重复的Illumina TruSeq链特异性mRNA文库。每个处理后的数据文件均由免疫沉淀（IP）样本与输入对照样本共同生成，并与对应的IP样本记录相关联。