Cartilage and bone of the lower jaw in development and disease

项目总结 下颌骨演变为由许多骨骼组成的结构，其中最大的一块牙齿，作为一种 现代哺乳动物中的单个下颌骨，在人类中被称为下颌。下颌骨紊乱， 通常会导致小颌骨，是人类最常见的出生缺陷之一。这些疾病可以戏剧性地 影响生活质量，并经常与呼吸道阻塞、言语障碍和 喂食。在胚胎发育过程中，下颌骨的发育先于小管并与之相关。 被称为Meckel‘s软骨(MC)的软骨棒和MC的异常与下颌骨有关 精神错乱。在现代哺乳动物中，MC的发育是复杂的：前部有助于MC的形成 下颌联合，其后部形成软骨，软骨内矿化形成两个中间 耳骨，中部的后半部分形成韧带。对前半部分的了解较少 MC的中间区域是暂时的，在其前面的胚胎发育的一个小窗口中存在 消失了。公认的评估将MC描述为下颌骨形成的模板，但有证据表明 这方面的研究很少，对MC中段和下颌之间的关系也知之甚少。 矿化、大小和形状或MC在长度上的生长过程、软骨膜骨化和 MC的失踪。我们提供的数据表明，MC不能作为模板 软骨模型在软骨内骨化中的作用和MC中段的新作用 在确定下颌长度时，软骨膜的矿化，下颌骨的矿化，以及其 失踪案。因为我们的发现挑战了MC的传统角色，我们设计这个项目是为了 验证MC中段消失和下颌骨形成时发生的发育事件 通过对四个过程的详细分析：1)MC的形成和长大；2)MC的矿化 软骨膜；3)下颌骨矿化；4)MC消失。我们的方法是基于 我们通过对发生在不同时间的这些过程进行初步调查而获得的知识 沿着MC的长度，并跨越MC内部的颊到舌方面。我们结合了3D成像 对胚胎突变型Sox9Flox/FLOX、Col2a1-CreERT和Sox9Flox/FLOX小鼠进行了组织和细胞分析 精确定义在发育时间和解剖空间中下颌骨细胞动力学的变化。 这些数据反过来被用来为我们的rna-seq分析提供关于发育中的MC和下颌骨的信息 通过差异基因表达、途径和网络分析恢复潜在的转录组。我们 计划细胞谱系追踪实验，以确定MC中间区域细胞的命运，这些细胞 启动MC软骨膜矿化和下颌骨矿化。我们的综合方法旨在 为下颌骨发育带来新的认识，开辟新的研究领域，推进战略 下颌骨疾病的骨修复、再生和预防。

PROJECT SUMMARY The lower jaw evolved as a structure composed of many bones the largest of which, the dentary, persists as a single lower jawbone in modern mammals, and is referred to as the mandible in humans. Mandibular disorders, often resulting in small jaws, are among the most common human birth defects. These disorders can dramatically affect quality of life, and are often associated, or compound problems with airway obstruction, speech, and feeding. During embryogenesis, development of the mandible is preceded by and associated with a tubular cartilage rod called Meckel's cartilage (MC) and anomalies of MC have been associated with mandibular disorders. Development of MC in modern mammals is complex: the anterior part contributes to the formation of the mandibular symphysis, its posterior part forms cartilages that mineralize endochondrally to form two middle ear bones, and the posterior half of the middle region forms ligaments. Less is known about the anterior half of the middle region of MC, which is transient, present during a small window of embryonic development before it disappears. Established assessments describe MC as a template for the formation of the mandible, but evidence of this is lacking and little is known of the relationship between the midportion of MC and mandibular mineralization, size, and shape or the processes of MC growth in length, perichondrial ossification, and disappearance of MC. We present data demonstrating that MC does not serve as a template in the way cartilaginous models function in endochondral ossification and hypothesize a new role for the mid portion of MC in determining mandibular length, mineralization of the perichondrium, mineralization of the mandible, and its disappearance. Because our findings challenge the traditional role of MC, we have designed this project to validate the developmental events that take place as the midportion of MC disappears and the mandible forms through a detailed analysis of four processes: 1) initiation and growth in length of MC; 2) mineralization of MC perichondrium; 3) mineralization of the mandible; and 4) disappearance of MC. Our approach is based on knowledge we have gained through preliminary investigations of these processes occurring at different times along the length of MC, and spanning the buccal to lingual aspects of the interior of MC. We couple 3D imaging with tissue and cellular analyses of embryonic mutant Sox9flox/flox;Col2a1-CreERT, and Sox9flox/flox mice to precisely define the changing cellular dynamics of the lower jaw in developmental time and anatomical space. These data are used in turn to inform our RNA-seq analyses of the developing MC and mandible directed at recovering the underlying transcriptome by differential gene expression, pathway, and network analyses. We plan cell lineage tracing experiments to determine the fate of cells from the intermediate region of MC, those that initiate MC perichondrial mineralization, and mandible mineralization. Our integrative approach is designed to bring new understanding to lower jaw development and open novel research areas to advance strategies for bone repair, regeneration, and prevention in mandibular disease.