Institute of Neurology, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.
School of Medicine, University of Electronic Science and Technology of China, Chengdu, China.
J Cell Mol Med. 2021 Sep;25(17):8567-8572. doi: 10.1111/jcmm.16740. Epub 2021 Jul 21.
N6-Methyladenosine (m6A) is the most prevalent internal modification in messenger RNAs (mRNAs) of eukaryotes and plays a vital role in post-transcriptional regulation. Recent studies demonstrated that m6A is essential for the normal function of the central nervous system (CNS), and the deregulation of m6A leads to a series of CNS diseases. However, the functional consequences of m6A deficiency within the dopaminergic neurons of adult brain are elusive. To evaluate the necessity of m6A in dopaminergic neuron functions, we conditionally deleted Mettl14, one of the most important part of m6A methyltransferase complexes, in the substantia nigra (SN) region enriched with dopaminergic neurons. By using rotarod test, pole test, open-field test and elevated plus maze, we found that the deletion of Mettl14 in the SN region induces impaired motor function and locomotor activity. Further molecular analysis revealed that Mettl14 deletion significantly reduced the total level of m6A in the mRNA isolated from SN region. Tyrosine hydroxylase (TH), an essential enzyme for dopamine synthesis, was also down-regulated upon Mettl14 deletion, while the activation of microglia and astrocyte was enhanced. Moreover, the expression of three essential transcription factors in the regulation of TH including Nurr1, Pitx3 and En1, with abundant m6A-binding sites on their RNA 3'-untranslated regions (UTR), was significantly decreased upon Mettl14 deletion in SN. Our finding first confirmed the significance of m6A in maintaining normal dopaminergic function in the SN of adult mouse.
N6-甲基腺苷（m6A）是真核生物信使 RNA（mRNA）中最普遍的内部修饰，在转录后调控中发挥着至关重要的作用。最近的研究表明，m6A 对于中枢神经系统（CNS）的正常功能是必不可少的，而 m6A 的失调会导致一系列 CNS 疾病。然而，成年大脑中多巴胺能神经元内 m6A 缺乏的功能后果仍不清楚。为了评估 m6A 在多巴胺能神经元功能中的必要性，我们在富含多巴胺能神经元的黑质（SN）区域中条件性地敲除了 m6A 甲基转移酶复合物的重要组成部分之一 Mettl14。通过转棒试验、棒试验、旷场试验和高架十字迷宫试验，我们发现 SN 区域中 Mettl14 的缺失会导致运动功能和运动活性受损。进一步的分子分析表明，Mettl14 的缺失显著降低了从 SN 区域分离的 mRNA 中的总 m6A 水平。多巴胺合成所必需的酶酪氨酸羟化酶（TH）在 Mettl14 缺失时也下调，而小胶质细胞和星形胶质细胞的激活增强。此外，在 SN 中，调控 TH 的三个重要转录因子 Nurr1、Pitx3 和 En1 的表达，它们的 RNA 3'-非翻译区（UTR）上有丰富的 m6A 结合位点，在 Mettl14 缺失时显著降低。我们的发现首次证实了 m6A 在维持成年小鼠 SN 中正常多巴胺能功能中的重要性。
