Dental Follicle: A Central Regulator of Tooth Eruption and Root Formation

项目总结/摘要 牙齿萌出是人类生存所必需的，直接影响到人类的基本功能， 下面部的生长和发育，营养/能量摄入的咀嚼， 有效沟通。涉及牙齿萌出的疾病以各种形式在普通公众中普遍存在。 阻萌、异位萌、阻萌（2~4%）。许多受影响的 牙齿对正牙机械力的反应不好，经常导致关节强直。提取这些 牙齿导致发病，随后需要功能较差的假体，从而损害 患者的生活质量。因此，需要更有效的方式来促进或重新激活牙齿萌出。的 围绕发育中牙齿的牙囊（DF）协调牙齿萌出和牙根形成。DF 促进破骨细胞的形成，破骨细胞再吸收牙槽骨以产生萌出路径，并且包括 用于成牙骨质细胞和牙周韧带（PDL）细胞的间充质祖细胞。这些DF祖细胞 细胞对牙周组织的发育至关重要，这对牙周病的后期阶段尤其重要。 牙齿萌出由于PTH/PTHrP受体（PPR）的功能缺失突变导致原发性牙齿衰竭， 在人类的PFE中，PPR依赖的调节DF祖细胞的机制可能起作用， 对牙齿萌出和牙根形成的耦合起重要作用。在这个项目中，我们假设DF 祖细胞是牙齿萌出和牙根形成的中心调节器， 发挥重要的调节作用，以维持这些细胞的独特性质。在目标1中，我们将确定 体内牙囊祖细胞的分子特征工作假设是DF细胞 表达一组独特的转录因子，这些转录因子保持它们作为间充质祖细胞的特性。 使用DF特异性PTHrP-creER转基因系，我们将确定个体DF的基因表达谱， 基于单细胞RNA-seq分析的祖细胞，随后对这些基因进行原位验证。此外，本发明还 我们将建立一个细胞培养模型来研究DF祖细胞的异质性和特性， 克隆选择和鉴定。在Aim 2中，我们将定义PTH/PTHrP受体在DF祖细胞中的作用。 牙齿萌出的细胞。工作假设是，在DF祖细胞中PTHrP-PPR信号传导是必不可少的 以维持其自我更新和分化成牙周膜（PDL）细胞的能力。使用鼠标 我们已经成功建立了PFE模型，我们将确定PPR缺陷对细胞命运的影响 使用离体细胞培养系统的DF祖细胞的决定和自我更新。此外，使用 比较RNA-seq分析，我们将确定PPR靶基因负责小鼠PFE表型 其中牙齿萌出与牙根形成分离。作为今后的研究计划，我们将进一步调查 调节DF祖细胞命运决定的关键分子机制。我们将特别关注 PPR信号下游的转录因子。

PROJECT SUMMARY/ABSTRACT Tooth eruption is essential for survival of humans, with direct impact on the fundamental functions such as growth and development of the lower face, mastication for nutrition/energy intake, speech and esthetics for effective communication. Disorders involving tooth eruption are prevalent among the general public in a variety of forms such as delayed, ectopic and failure of eruption (2~4% for permanent molars). Many of these affected teeth do not respond well to orthodontic mechanical forces, often resulting in ankylosis. Extraction of these teeth results in morbidity and subsequently requires prostheses with inferior function, thus compromising patients' quality of life. Thus, more effective modalities to facilitate or reactivate tooth eruption are needed. The dental follicle (DF) surrounding the developing tooth coordinates tooth eruption and root formation. DF facilitates formation of osteoclasts that resorb alveolar bones to create the eruption pathway, and includes mesenchymal progenitor cells for cementoblasts and periodontal ligament (PDL) cells. These DF progenitor cells are crucial for development of periodontal tissues, which are particularly important for the later stage of tooth eruption. As loss-of-function mutations in PTH/PTHrP receptor (PPR) cause primary failure of tooth eruption (PFE) in humans, a PPR-dependent mechanism regulating DF progenitor cells is likely to play important roles for the coupling of tooth eruption and root formation. In this project, we hypothesize that DF progenitor cells are the central regulators of tooth eruption and root formation, whereby PTHrP-PPR signaling exerts important regulatory roles to maintain their unique properties of these cells. In Aim1, we will determine molecular characteristics of dental follicle progenitor cells in vivo. The working hypothesis is that DF cells express a unique set of transcription factors that maintain their properties as mesenchymal progenitor cells. Using the DF-specific PTHrP-creER transgenic line, we will define the gene expression profiles of individual DF progenitor cells based on a single cell RNA-seq analysis, followed by in situ validation of these genes. Further, we will establish a cell culture model to investigate heterogeneity and properties of DF progenitor cells through clonal selection and characterization. In Aim2, we will define roles of the PTH/PTHrP receptor in DF progenitor cells in tooth eruption. The working hypothesis is that PTHrP-PPR signaling in DF progenitor cells is essential to maintain their ability to self-renew and differentiate into periodontal ligament (PDL) cells. Using the mouse PFE model we have successfully established, we will determine the impact of PPR-deficiency on cell fate decision and self-renewal of DF progenitor cells using ex vivo cell culture systems. Further, using a comparative RNA-seq analysis, we will identify PPR-target genes responsible for the mouse PFE phenotypes in which tooth eruption is uncoupled from root formation. As a future research plan, we will further investigate key molecular mechanisms that regulate cell fate decisions of DF progenitor cells. We will particular focus on transcription factors downstream of PPR signaling.