Control of reptilian dental patterning and tooth replacement in 4D

描述（由申请人提供）：拟议研究的长期目标是发现爬行动物终身牙齿继承的分子基础，并将这些知识应用于人类牙齿的再生。博士后研究员将在这个项目中使用一种独特的模型，豹纹壁虎。与更典型的模型——老鼠相比，使用爬行动物有两个主要好处。首先，爬行动物是羊膜动物，因此与哺乳动物有着共同的祖先。我们在爬行动物身上学到的东西也适用于人类。其次，爬行动物的牙齿替换是持续进行的，与磨损或损伤无关，而且是快速的（30-90天），因此在实验室环境中研究这一过程是可行的。相比之下，哺乳动物最多只有两副牙齿，通常第二代牙齿会持续发育到产后。首先要解决的问题是，在健康的成年爬行动物中，牙齿更换的精确时间和模式是什么？为了回答这些问题，我们以豹壁虎为模型。这些动物很容易处理，并且有可能使许多用于人类的牙科手术适应它们较小的嘴巴。在6个月的时间里，将对牙齿进行连续的蜡咬和CT扫描，并测量牙齿脱落和更换的时间。然后，牙齿替换表型将与牙齿组织中基因的表达相关。我们感兴趣的是寻找沿下颌长度周期性表达的基因，因为其中一些基因可能协调牙齿间距和诱导替换牙齿的时间。第二个要解决的问题是破坏牙层活动对牙齿置换模式的长期后遗症是什么？为了回答这个问题，将对成年壁虎进行显微手术，包括切割牙板。预测结果是牙间距或牙齿置换率的变化，这可以追溯到牙上皮的分子变化。第三个也是最后一个要问的问题是，在胚胎形成和成人替代期间，牙齿形成和诱导的分子控制是什么？两个候选分子的作用将被研究。这两种通路被称为无翼相关（Wnt）和Notch，部分原因是Wnt突变会增加或减少人类的牙齿数量，而且Notch- Delta信号已知可以调节成体干细胞更新和分化之间的细胞命运决定，并在调节发育时钟机制中发挥作用。为了反映人类的情况，寻找调节牙齿更新的稳态开关的证据，将Wnt和Notch的激活剂或抑制剂注射到卵子中，并研究对牙齿上皮生长和模式的影响。申请人/博士后研究员和导师之间的协同研究伙伴关系将有一天产生更自然的方法来替代因疾病或受伤而失去的牙齿。

DESCRIPTION (provided by applicant): The long term goal of the proposed research is to discover the molecular basis for life-long tooth succession in reptiles and to apply this knowledge to the regeneration of human teeth. The post-doctoral fellow will be using a unique model, the leopard gecko, for this project. There are two main benefits to using reptiles as opposed to the more typical model, the mouse. First, reptiles are amniotes and thus share a common ancestry with mammals. What we learn in reptiles is relevant for humans. Second, tooth replacement in reptiles is on-going, independent of wear or injury and is rapid (30-90 days) thus it is feasible to study the process in a lab setting. In contrast, mammals have at most two sets of teeth and usually the second generation continues to form well into the post-natal period. The first question to be addressed is what is the precise timing and pattern of tooth replacement in healthy adult reptiles? To answer these questions, the leopard gecko is used as the model. These animals are easy to handle and it is possible to adapt many dental procedures used for humans to their smaller mouths. Miniature, serial wax bites and �CT scans will be taken over a 6 month period and measurements of when teeth are lost and replaced will be taken. The tooth replacement phenotypes will then be correlated with the expression of genes in the dental tissues. We are interested in finding genes that are periodically expressed along the length of the jaw since some of these may coordinate tooth spacing and timing of induction of replacement teeth. The second question to be addressed is what are the long term sequelae of disrupting the activity of the dental lamina on the patterns of tooth replacement? To answer this question, micro surgeries will be carried out in adult geckos including cutting of the dental lamina. The outcomes are predicted to be a change in the spacing or rate of tooth replacement that can be traced back to molecular changes in the dental epithelium. The third and final question to be asked is what are the molecular controls of tooth patterning and induction during embryonic initiation and adult replacement? The roles of two candidate molecules will be studied. These two pathways, called Wingless related (Wnt) and Notch were selected in part because mutations in Wnt increase or decrease tooth number in humans, and because Notch- Delta signalling is known to regulate cell fate decisions between adult stem cell renewal and differentiation along with its role in regulating developmental clock mechanisms. To mirror the human condition, to look for evidence of homeostatic switches regulating tooth renewal, activators or inhibitors of Wnt and Notch will be injected into eggs and the effects on tooth epithelial growth and patterning will be studied. The synergistic research partnership between the applicant/postdoctoral fellow and supervisor will one day lead to more natural ways to replace teeth lost to disease or injury.