Choi Janghyun, Lee Hansol
Department of Biological Sciences, College of Natural Science, Inha University, Incheon, South Korea.
J Biol Chem. 2023 Oct;299(10):105193. doi: 10.1016/j.jbc.2023.105193. Epub 2023 Aug 24.
Despite significant progress in our understanding of the molecular mechanism of mesenchymal stem cell (MSC) differentiation, less is known about the factors maintaining the stemness and plasticity of MSCs. Here, we show that the NFIB-MLL1 complex plays key roles in osteogenic differentiation and stemness of C3H10T1/2 MSCs. We find that depletion of either NFIB or MLL1 results in a severely hampered osteogenic potential and failed activation of key osteogenic transcription factors, such as Dlx5, Runx2, and Osx, following osteogenic stimuli. In addition, the NFIB-MLL1 complex binds directly to the promoter of Dlx5, and exogenous expression of Myc-Dlx5, but not the activation of either the BMP- or the Wnt-signaling pathway, is sufficient to restore the osteogenic potential of cells depleted of NFIB or MLL1. Moreover, chromatin immunoprecipitation (ChIP) and ChIP-sequencing analysis showed that the NFIB-MLL1 complex mediates the deposition of trimethylated histone H3K4 at both Dlx5 and Cebpa, key regulator genes that function at the early stages of osteogenic and adipogenic differentiation, respectively, in uncommitted C3H10T1/2 MSCs. Surprisingly, the depletion of either NFIB or MLL1 leads to decreased trimethylated histone H3K4 and results in elevated trimethylated histone H3K9 at those developmental genes. Furthermore, gene expression profiling and ChIP-sequencing analysis revealed lineage-specific changes in chromatin landscape and gene expression in response to osteogenic stimuli. Taken together, these data provide evidence for the hitherto unknown role of the NFIB-MLL1 complex in the maintenance and lineage-specific differentiation of C3H10T1/2 MSCs and support the epigenetic regulatory mechanism underlying the stemness and plasticity of MSCs.
尽管我们对间充质干细胞（MSC）分化的分子机制已有显著认识，但对于维持MSC干性和可塑性的因素却知之甚少。在此，我们表明NFIB-MLL1复合物在C3H10T1/2 MSC的成骨分化和干性中起关键作用。我们发现，NFIB或MLL1的缺失会导致成骨潜能严重受损，并且在成骨刺激后关键成骨转录因子（如Dlx5、Runx2和Osx）无法激活。此外，NFIB-MLL1复合物直接结合到Dlx5的启动子上，Myc-Dlx5的外源性表达而非BMP或Wnt信号通路的激活足以恢复NFIB或MLL1缺失细胞的成骨潜能。此外，染色质免疫沉淀（ChIP）和ChIP测序分析表明，NFIB-MLL1复合物介导未分化的C3H10T1/2 MSC中组蛋白H3K4三甲基化在Dlx5和Cebpa上的沉积，这两个关键调节基因分别在成骨和成脂分化的早期阶段发挥作用。令人惊讶的是，NFIB或MLL1的缺失会导致这些发育基因处组蛋白H三甲基化水平降低，而组蛋白H3K9三甲基化水平升高。此外，基因表达谱分析和ChIP测序分析揭示了响应成骨刺激时染色质景观和基因表达的谱系特异性变化。综上所述，这些数据为NFIB-MLL1复合物在C3H10T1/2 MSC的维持和谱系特异性分化中迄今未知的作用提供了证据，并支持了MSC干性和可塑性的表观遗传调控机制。
