Profile of N6-methyladenosine of Pb-exposed neurons presents epitranscriptomic alterations in Pi3K-AKT pathway-associated genes

Lead (Pb) is a pervasive heavy metal with multi-organ toxicity. However, the molecular mechanisms of Pb-induced neurotoxicity are not fully understood. The dynamics of N6-methylademine (m6A) is an emerging regulatory mechanism for gene expression, which is closely related to nervous system diseases. To elucidate the association between m6A modification and Pb-mediated neurotoxicity, primary hippocampal neurons exposed to 5 μM Pb for 48 h were used as the paradigm neurotoxic model in this study. According to the results, Pb exposure reprogrammed the transcription spectrum. Simultaneously, Pb exposure remodeled the transcriptome-wide distribution of m6A while disrupting the overall level of m6A in cellular transcripts. United analysis of MeRIP-Seq and RNA-Seq was applied to further identify the core genes whose expression levels are regulated by m6A in the process of lead-induced nerve injury. GO and KEGG analysis unveiled that the modified transcripts were overrepresented by the PI3K-AKT pathway. Mechanically, we elucidated the regulatory role of the methyltransferase like3 (METTL3) in the process of lead-induced neurotoxicity and the downregulation of the PI3K-AKT pathway. In conclusion, our novel findings shed new light on the functional roles of m6A modification in the expressional alternations of downstream transcripts caused by lead, providing an innovative molecular basis to explain Pb neurotoxicity.铅（Lead, Pb）是一种广泛存在的重金属，具有多器官毒性。然而，铅诱导神经毒性的分子机制尚未完全阐明。N6-甲基腺苷（N6-methylademine, m6A）的动态调控是一种新兴的基因表达调控机制，与神经系统疾病密切相关。为阐明m6A修饰与铅介导神经毒性之间的关联，本研究以暴露于5 μM铅处理48小时的原代海马神经元作为神经毒性模型范式。研究结果显示，铅暴露重塑了转录谱；与此同时，铅暴露在破坏细胞转录本整体m6A水平的同时，也重塑了全转录组范围内的m6A分布模式。本研究通过MeRIP-Seq与RNA-Seq的联合分析，进一步筛选出在铅诱导神经损伤过程中受m6A调控表达的核心基因。基因本体（Gene Ontology, GO）与京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）富集分析显示，受修饰的转录本显著富集于PI3K-AKT信号通路。机制层面上，本研究阐明了甲基转移酶样3（Methyltransferase-like 3, METTL3）在铅诱导神经毒性及PI3K-AKT通路下调过程中的调控作用。综上，本研究的创新性发现为阐释铅暴露诱导的下游转录本表达改变中m6A修饰的功能作用提供了新视角，同时为解释铅神经毒性机制提供了全新的分子学基础。