Molecular Patterning of Mammalian Dentition

哺乳动物牙列的分子模式

• 批准号: 8733649
• 负责人: RULANG JIANG
• 金额: $ 51.68万
• 依托单位: CINCINNATI CHILDRENS HOSP MED CTR
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-20 至 2018-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8733649
• 关键词: Activins; Automobile Driving; Bioinformatics; Biological Assay; Biological Models; Congenital Abnormality; Data; Defect; Dentition; Development; Embryo; Epithelium; Exhibits; Failure; Gene Expression Profiling; Gene Targeting; Generations; Genes; Genetic; Genetic Transcription; Human; Incisor; Lead; MSX1 gene; Mandible; Maxilla; Mesenchymal; Mesenchyme; Molar tooth; Molecular; Morphogenesis; Mus; Mutant Strains Mice; Mutation; Neural Crest; Odontogenesis; Organ; Organ Culture Techniques; Organogenesis; Pathway interactions; Pattern; Proteins; Regulation; Research Project Grants; Role; Signal Pathway; Signal Transduction; Staging; Supernumerary Tooth; Testing; Tissues; Tooth Germ; Tooth structure; Transducers; WNT Signaling Pathway; WNT10A gene; activin A; base; cleft lip and palate; comparative; improved; in vivo; mRNA Expression; mutant; novel; novel therapeutics; oral cavity epithelium; public health relevance; transcription factor

DESCRIPTION (provided by applicant): Tooth development has long been used as a powerful model system for studying the molecular mechanisms regulating organogenesis and the pathogenic mechanisms of tooth developmental anomalies in humans. A critical step in tooth development is the activation of odontogenic potential in the neural crest-derived tooth mesenchyme, which is responsible for driving tooth morphogenesis from the tooth bud stage and is sufficient to induce tooth organogenesis when recombined with non-dental epithelium. Failure to activate mesenchymal odontogenic potential is associated with tooth bud developmental arrest, as seen in mice lacking the Msx1 transcription factor. Mutations in MSX1 are also associated with tooth agenesis in humans. Previous studies suggested that Bmp4 is an important odontogenic signal downstream of Msx1. Bmp4 mRNA expression was downregulated in Msx1-/- tooth mesenchyme. However, we found that mice with neural crest specific inactivation of the Bmp4 gene exhibit developmental arrest of only the mandibular molar buds but their maxillary molars and incisors developed to mineralized teeth. We carried out RNAseq analyses of microdissected tooth bud mesenchyme and found that the mandibular molar mesenchyme expresses much higher levels of secreted Wnt antagonists than does the maxillary molar mesenchyme. We found that tissue- specific inactivation of ?-catenin, the obligatory transducer of canonical Wnt signaling, in the early tooth mesenchyme caused tooth bud developmental arrest, suggesting that the higher levels of Wnt antagonists in mandibular molar tooth mesenchyme contribute to the dramatic differences in maxillary and mandibular molar tooth defects in the Bmp4 mutant mice. Moreover, we discovered recently that inactivation of the Osr2 transcription factor caused supernumerary tooth formation from oral epithelium lingual to the molar tooth germs in mice. Osr2 is expressed in a gradient pattern and suppressed the domain of mesenchymal odontogenic potential along the buccolingual axis of the developing tooth mesenchyme. Whereas Msx1-/- mutant mice had tooth development arrested at the bud stage, Msx1-/-Osr2-/- double mutants exhibited nearly normal first molar morphogenesis but did not initiate supernumerary tooth development. Moreover, we found that Msx1 and Osr2 regulate antagonistically the expression of secreted Wnt antagonists in the developing tooth mesenchyme. Together, these data suggest novel mechanisms involving Bmp, Msx1, Osr2, and Wnt signaling pathways in the regulation of mesenchymal odontogenic potential. The major aims of this project are to identify, characterize, and integrate the molecula mechanisms combining these factors and pathways regulating early odontogenesis, using multifaceted experimental approaches, including in vivo pharmacological rescue, nanogram scale RNAseq-based gene expression profiling, and combined explant organ culture and genetic functional assays. Data from this project will significantly improve the current understanding of the molecular mechanisms of tooth development and multiple human birth defects and will facilitate development of new therapeutic strategies.

描述（由申请人提供）：牙齿发育长期以来一直被用作研究人类器官发生调节的分子机制和牙齿发育异常的致病机制的强大模型系统。牙齿发育的关键步骤是激活神经嵴衍生的牙齿间充质中的成牙潜能，它负责从牙芽阶段驱动牙齿形态发生，并且当与非牙齿上皮重组时足以诱导牙齿器官发生。未能激活间充质成牙潜能与牙芽发育停滞有关，正如在缺乏 Msx1 转录因子的小鼠中所见。 MSX1 突变也与人类牙齿发育不全有关。先前的研究表明Bmp4是Msx1下游重要的成牙信号。 Msx1-/- 牙齿间充质中 Bmp4 mRNA 表达下调。然而，我们发现 Bmp4 基因神经嵴特异性失活的小鼠仅下颌磨牙芽发育停滞，但上颌磨牙和门牙发育为矿化牙齿。我们对显微解剖的牙芽间充质进行了 RNAseq 分析，发现下颌磨牙间充质表达的分泌性 Wnt 拮抗剂水平比上颌磨牙间充质高得多。我们发现，早期牙齿间质中β-连环蛋白（经典Wnt信号传导的必然转导器）的组织特异性失活导致牙芽发育停滞，这表明下颌磨牙间质中较高水平的Wnt拮抗剂导致Bmp4突变小鼠上颌和下颌磨牙缺陷的显着差异。此外，我们最近发现Osr2转录因子的失活导致小鼠从口腔舌上皮到臼齿牙胚形成多生牙。 Osr2 以梯度模式表达，并抑制沿着发育中的牙齿间充质的颊舌轴的间充质成牙潜力的区域。 Msx1-/-突变小鼠的牙齿发育在芽期停滞，而Msx1-/-Osr2-/-双突变体表现出几乎正常的第一磨牙形态发生，但没有启动多生牙发育。此外，我们发现Msx1和Osr2拮抗地调节发育中的牙齿间质中分泌的Wnt拮抗剂的表达。总之，这些数据表明涉及 Bmp、Msx1、Osr2 和 Wnt 信号通路在调节间充质成牙潜能中的新机制。该项目的主要目标是使用多方面的实验方法，包括体内药理学救援、纳克级基于 RNAseq 的基因表达谱以及联合外植体器官培养和遗传功能测定，识别、表征和整合结合这些因素和调节早期牙发生的途径的分子机制。该项目的数据将显着提高目前对牙齿发育和多种人类出生缺陷分子机制的理解，并将促进新治疗策略的开发。