Mesenchymal stem cell (MSC)-based therapy has emerged as a promising treatment for spinal cord injury (SCI), but improving the neurogenic potential of MSCs remains a challenge. Mixed lineage leukemia 1 (MLL1), an H3K4me3 methyltransferases, plays a critical role in regulating lineage-specific gene expression and influences neurogenesis. In this study, we investigated the role and mechanism of MLL1 in the neurogenesis of stem cells from apical papilla (SCAPs). We examined the expression of neural markers, and the nerve repair and regeneration ability of SCAPs using dynamic changes in neuron-like cells, immunofluorescence staining, and a SCI model. We employed a coimmunoprecipitation (Co-IP) assay, real-time RT-PCR, microarray analysis, and chromatin immunoprecipitation (ChIP) assay to investigate the molecular mechanism. The results showed that MLL1 knock-down increased the expression of neural markers, including neurogenic differentiation factor (NeuroD), neural cell adhesion molecule (NCAM), tyrosine hydroxylase (TH), βIII-tubulin and Nestin, and promoted neuron-like cell formation in SCAPs. In vivo, a transplantation experiment showed that depletion of MLL 1 in SCAPs can restore motor function in a rat SCI model. MLL1 can combine with WD repeat domain 5 (WDR5) and WDR5 inhibit the expression of neural markers in SCAPs. MLL1 regulates Hairy and enhancer of split 1 (HES1) expression by directly binds to HES1 promoters via regulating H3K4me3 methylation by interacting with WDR5. Additionally, HES1 enhances the expression of neural markers in SCAPs. Our findings demonstrate that MLL1 inhibits the neurogenic potential of SCAPs by interacting with WDR5 and repressing HES1. These results provide a potential therapeutic target for promoting the recovery of motor function in SCI patients.

基于间充质干细胞 (MSC) 的疗法已成为脊髓损伤 (SCI) 的一种有前景的治疗方法，但提高 MSC 的神经源潜力仍然是一个挑战。混合谱系白血病 1 (MLL1) 是一种 H3K4me3 甲基转移酶，在调节谱系特异性基因表达和影响神经发生中发挥着关键作用。在本研究中，我们研究了 MLL1 在心尖乳头干细胞 (SCAP) 神经发生中的作用和机制。我们利用神经元样细胞的动态变化、免疫荧光染色和 SCI 模型检查了神经标志物的表达以及 SCAP 的神经修复和再生能力。我们采用免疫共沉淀 (Co-IP) 测定、实时 RT-PCR、微阵列分析和染色质免疫沉淀 (ChIP) 测定来研究分子机制。结果显示，MLL1敲除增加了神经标志物的表达，包括神经源性分化因子（NeuroD）、神经细胞粘附分子（NCAM）、酪氨酸羟化酶（TH）、βIII-微管蛋白和巢蛋白，并促进神经元样细胞形成在 SCAP 中。体内移植实验表明，SCAP 中 MLL 1 的缺失可以恢复大鼠 SCI 模型的运动功能。MLL1可以与WD重复结构域5（WDR5）结合，WDR5抑制SCAP中神经标志物的表达。MLL1 通过与 WDR5 相互作用调节 H3K4me3 甲基化，直接结合 HES1 启动子，从而调节毛状和分裂增强子 1 (HES1) 的表达。此外，HES1 还能增强 SCAP 中神经标志物的表达。我们的研究结果表明，MLL1 通过与 WDR5 相互作用并抑制 HES1 来抑制 SCAP 的神经源性潜力。这些结果为促进SCI患者运动功能的恢复提供了潜在的治疗靶点。