BACKGROUND Neural tube defects (NTDs) are severe, common birth defects that result from failure of normal neural tube closure during early embryogenesis. Accumulating strong evidence indicates that genetic factors contribute to NTDs etiology, among them, HOX genes play a key role in neural tube closure. Although abnormal HOX gene expression can lead to NTDs, the underlying pathological mechanisms have not fully been understood. METHOD We detected that H3K27me3 and expression of the Hox genes in a retinoic acid (RA) induced mouse NTDs model on E8.5, E9.5 and E10.5 using RNA-sequencing and chromatin immunoprecipitation sequencing assays. Furthermore, we quantified 10 Hox genes using NanoString nCounter in brain tissue of fetuses with 39 NTDs patients including anencephaly, spina bifida, hydrocephaly and encephalocele. RESULTS Here, our results showed differential expression in 26 genes with a > 20-fold change in the level of expression, including 10 upregulated Hox genes. RT-qPCR revealed that these 10 Hox genes were all upregulated in RA-induced mouse NTDs as well as RA-treated embryonic stem cells (ESCs). Using ChIP-seq assays, we demonstrate that a decrease in H3K27me3 level upregulates the expression of Hox cluster A-D in RA-induced mouse NTDs model on E10.5. Interestingly, RA treatment led to attenuation of H3K27me3 due to cooperate between UTX and Suz12, affecting Hox gene regulation. Further analysis, in human anencephaly cases, upregulation of 10 HOX genes was observed, along with aberrant levels of H3K27me3. Notably, HOXB4, HOXC4 and HOXD1 expression was negatively correlated with H3K27me3 levels. CONCLUSION Our results indicate that abnormal HOX gene expression induced by aberrant H3K27me3 levels may be a risk factor for NTDs and highlight the need for further analysis of genome-wide epigenetic modification in NTDs.

中文翻译：

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减少的H3K27me3导致神经管缺陷中异常的Hox基因表达。

背景技术神经管缺陷（NTD）是严重的，常见的先天性缺陷，是由早期胚胎发生过程中正常的神经管闭合失败导致的。越来越多的证据表明，遗传因素是导致NTD病因的原因，其中，HOX基因在神经管闭合中起关键作用。尽管HOX基因表达异常会导致NTD，但尚未完全了解其潜在的病理机制。方法我们使用RNA测序和染色质免疫沉淀测序法检测了E3，E9.5和E10.5在视黄酸（RA）诱导的小鼠NTDs模型中检测到H3K27me3和Hox基因的表达。此外，我们使用NanoString nCounter在39名NTD患者的胎儿脑组织中定量了10个Hox基因，包括无脑，脊柱裂，脑积水和脑膨出。结果在这里，我们的结果显示26种基因的差异表达，其中表达水平变化> 20倍，其中包括10种上调的Hox基因。RT-qPCR显示，这10个Hox基因在RA诱导的小鼠NTD和RA处理的胚胎干细胞（ESC）中均被上调。使用ChIP-seq分析，我们证明了H3K27me3水平的降低上调了RA诱导的E10.5小鼠NTDs模型中Hox簇AD的表达。有趣的是，由于UTX和Suz12之间的合作，RA治疗导致H3K27me3减弱，从而影响Hox基因的调控。进一步分析，在人类无脑症病例中，观察到10个HOX基因的上调以及H3K27me3的异常水平。值得注意的是，HOXB4，HOXC4和HOXD1表达与H3K27me3水平呈负相关。