Tooth development is a complex process orchestrated by intricate gene regulatory networks, involving both odontogenic epithelium and ectomesenchyme. Six1, a pivotal transcription factor (TF), is involved in the development of the lower incisor. However, its precise role during incisor development and the molecular mechanisms underpinning its regulatory functions remain poorly understood. This study employs Six1 deletion mouse models to elucidate the critical regulatory role of Six1 in governing dental mesenchyme development. By performing single-cell RNA sequencing, we constructed a comprehensive transcriptome atlas of tooth germ development from the bud to bell stage. Our analyses suggest that the dental follicle and the dental papilla (DP) are differentiated from dental ectomesenchyme (DEM) and identify the key TFs underlying these distinct states. Notably, we show that Dlx1, Dlx2, and Dlx5 ( Dlx1/ 2/ 5) may function as the key TFs that promote the formation of DP. We further show that the deletion of Six1 perturbs dental mesenchyme development by impeding the transitions from DEM to DP states. Importantly, SIX1 directly binds to the promoters of Dlx1/ 2/ 5 to promote their co-expression, which subsequently leads to widespread epigenetic and transcriptional remodeling. In summary, our findings unveil Six1’s indispensable role in incisor development, offering key insights into TF-driven regulatory networks that govern dental mesenchyme cell fate transitions during tooth development.

中文翻译：

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Six1 通过促进 dlx1/2/5 表达来调节小鼠切牙发育


牙齿发育是一个复杂的过程，由错综复杂的基因调控网络精心编排，涉及牙源性上皮细胞和外胚层。Six1 是一种关键转录因子 （TF），参与下切牙的发育。然而，它在切牙发育过程中的确切作用以及支撑其调节功能的分子机制仍然知之甚少。本研究采用 Six1 缺失小鼠模型来阐明 Six1 在控制牙齿间充质发育中的关键调节作用。通过进行单细胞 RNA 测序，我们构建了从芽到钟期牙胚发育的综合转录组图谱。我们的分析表明，牙囊和牙（DP） 与牙外胚层充质 （DEM） 不同，并确定了这些不同状态背后的关键 TF。值得注意的是，我们表明 Dlx1、Dlx2 和 Dlx5 （ Dlx1/ 2/ 5） 可能是促进 DP 形成的关键 TF。我们进一步表明，Six1 的缺失通过阻碍从 DEM 到 DP 状态的转变来扰乱牙齿间充质发育。重要的是，SIX1 直接与 Dlx1/ 2/ 5 的启动子结合以促进它们的共表达，这随后导致广泛的表观遗传和转录重塑。总之，我们的研究结果揭示了 Six1 在切牙发育中不可或缺的作用，为 TF 驱动的调节网络提供了关键见解，这些网络控制着牙齿发育过程中牙齿间充质细胞命运的转变。