Neural tube defects (NTDs) are common congenital malformations resulting in failure of the neural tube closure during early embryonic development. Although it is known that maternal folate deficiency increases the risk of NTDs, the mechanism remains elusive. Herein, we report that histone H2A monoubiquitination (H2AK119ub1) plays a role in neural tube closure. We found that the folate antagonist methotrexate induced H2AK119ub1 in mouse embryonic stem cells. We demonstrated that an increase in H2AK119ub1 downregulated expression of the neural tube closure-related genes Cdx2, Nes, Pax6, and Gata4 in mouse embryonic stem cells under folate deficiency conditions. We also determined that the E3 ligase Mdm2 was responsible for the methotrexate-induced increase in H2AK119ub1 and downregulation of neural tube closure-related genes. Surprisingly, we found that Mdm2 is required for MTX-induced H2A ubiquitination and is recruited to the sites of DSB, which is dependent on DNA damage signaling kinase ATM. Furthermore, folic acid supplementation restored H2AK119ub1 binding to neural tube closure-related genes. Downregulation of these genes was also observed in both brain tissue of mouse and human NTD cases, and high levels of H2AK119ub1 were found in the corresponding NTDs samples with their maternal serum folate under low levels. Pearson correlation analysis showed a significant negative correlation between expression of the neural precursor genes and H2AK119ub1. Our results indicate that folate deficiency contributes to the onset of NTDs by altering H2AK119ub1 and subsequently affecting expression of neural tube closure-related genes. This may be a potential risk factor for NTDs in response to folate deficiency.

中文翻译：

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叶酸缺乏诱导H2A泛素化，导致神经管缺陷相关基因的表达下调。

神经管缺损（NTD）是常见的先天畸形，导致早期胚胎发育过程中神经管闭合失败。尽管已知孕妇叶酸缺乏会增加NTD的风险，但该机制仍然难以捉摸。在此，我们报道了组蛋白H2A单泛素化（H2AK119ub1）在神经管闭合中起作用。我们发现叶酸拮抗剂甲氨蝶呤在小鼠胚胎干细胞中诱导了H2AK119ub1。我们证明了H2AK119ub1的增加下调了叶酸缺乏条件下小鼠胚胎干细胞中神经管闭合相关基因Cdx2，Nes，Pax6和Gata4的表达。我们还确定E3连接酶Mdm2负责甲氨蝶呤诱导的H2AK119ub1的增加和神经管闭合相关基因的下调。出奇，我们发现Mdm2是MTX诱导的H2A泛素化所必需的，并被募集到DSB的位点，这取决于DNA损伤信号转导激酶ATM。此外，补充叶酸可恢复H2AK119ub1与神经管闭合相关基因的结合。在小鼠和人类NTD病例的脑组织中也观察到这些基因的下调，并且在相应的NTD样品中发现了高水平的H2AK119ub1，其母体血清叶酸水平较低。皮尔逊相关分析显示神经前体基因的表达与H2AK119ub1之间存在显着的负相关。我们的结果表明，叶酸缺乏通过改变H2AK119ub1并随后影响神经管闭合相关基因的表达而促进了NTD的发作。