Mesenchymal Regulation of Jaw Bone Length

描述（由申请人提供）：这是一个K 08奖的申请博士艾琳Ealba，在加州大学，旧金山弗朗西斯科的普通牙医。Ealba博士正在确立自己作为颅面骨发育基础科学研究的年轻研究员的地位。Ealba与实现以下目标所需的支持：（1）成为发育，骨骼和颅面生物学的专家;（2）专注于教师技能;（3）提高她的手稿和授予写作能力。为了实现这些目标，Ealba博士组建了一个指导团队，由一位主要导师[Richard Schneider博士，颅面发育领域的权威]，两位共同导师[Pamela DenBesten博士，专注于牙釉质矿化的领先牙医科学家，和Tamara Alliston博士，TGF？信号传导]和三位合作者[玛丽中村博士、拉尔夫·马库西奥博士和奥菲尔·克莱因博士]。Ealba博士的长期目标是发现用于调节骨长度和形状的新型分子疗法，以满足颅面畸形非手术治疗的需求。本研究的目的是通过了解神经嵴间充质（NCM）如何形成面部和颌骨骨骼中的所有元素来实现这一目标，调节颌骨大小。为了解决这个问题，我们在体内操纵NCM，一个高度可及的胚胎群体。具体地，我们将更快成熟的鹌鹑供体NCM移植到发育较慢的鸭宿主中，这产生了嵌合的鹌鹑;并且我们将较慢的鸭供体NCM移植到相对较快的鹌鹑宿主中，产生了嵌合的双胞胎。利用鹌鹑和鸭的不同发育程序提供了一种独特的方式来操纵NCM和邻近宿主组织之间的信号传导，并允许发现NCM依赖性过程。此外，所有的鹌鹑细胞可以通过一个无处不在的核标记不存在于鸭检测。在已发表的工作和初步研究中，我们观察到NCM自主地调节和指导成骨诱导、增殖、分化、基质沉积、矿化和基质重塑。NCM如何完成如此复杂的任务，以及哪些因素足以复制这种现象，目前尚不清楚。可能的候选者可能包括转化生长因子-β（TGF 2）的成员和靶点，因为已知它们在骨生成过程中起关键作用，并且它们的表达在嵌合体中改变。因此，我们假设，通过调节TGF？通过信号传导，NCM指导其自身的成骨程序并协调破骨细胞的活动以控制颌骨长度。为了验证我们的假设，我们提出了三个互补和非相互依赖的具体目标。具体目标1将确定NCM利用TGF 2信号传导来控制颌长度的程度。具体目标2将确定NCM在多大程度上依赖于破骨细胞的作用来调节颌骨长度。具体目标3将确定NCM通过TGF 2依赖性RANKL/OPG信号传导影响破骨细胞活性和颌骨长度的程度。我们将采用获得和丧失功能的技术，以确定分子机制，赋予NCM的能力，以控制颌骨长度。这个提议的实验可以作为一个原理证明，可以设计基于分子的疗法来治疗影响下颌长度的疾病。此外，确定供体NCM将其对破骨细胞等宿主细胞的影响传递给宿主细胞的机制对于创伤或骨质疏松症和骨坏死等疾病损伤的骨骼的修复和再生具有重要意义。我们希望我们的研究将为基于生物学的非手术方法提供基础，以补救各种临床骨骼疾病。

DESCRIPTION (provided by applicant): This is an application for a K08 award for Dr. Erin Ealba, a general dentist at the University of California, San Francisco. Dr. Ealba is establishing herself as a young investigator in basic science research of craniofacial bone development. This K08 award will provide Dr. Ealba with the support necessary to accomplish the following goals: (1) to become an expert in developmental, skeletal, and craniofacial biology; (2) to focus on faculty skills; and (3) to enhance her manuscript and grant writing abilities. To achieve these goals, Dr. Ealba has assembled a mentoring team comprised of a primary mentor [Dr. Richard Schneider, an authority in the field of craniofacial development], two co-mentors [Dr. Pamela DenBesten, a leading dentist-scientist focused on enamel mineralization, and Dr. Tamara Alliston, an expert in TGF? signaling], and three collaborators [Dr. Mary Nakamura, Dr. Ralph Marcucio, and Dr. Ophir Klein]. Dr. Ealba's long-term goal is to discover novel molecular-based therapies for regulating the length and shape of bone as a means to address the need for non-surgical treatments of craniofacial malformations. The objective of the current study is to build toward this goal by understanding how neural crest mesenchyme (NCM), which forms all the elements in the facial and jaw skeletons, regulates jaw size. To address this issue, we manipulate in vivo the NCM, a highly accessible embryonic population. Specifically, we transplant faster- maturing quail donor NCM into a slower-developing duck host, which creates chimeric quck; and we transplant slower duck donor NCM into the relatively faster quail host, generating chimeric duail. Exploiting the divergent developmental programs of quail and duck provides a unique way to manipulate signaling between NCM and adjacent host tissues, and allows discovery of NCM-dependent processes. Also, all quail cells can be detected via a ubiquitous nuclear marker not present in duck. In published work and in preliminary studies, we observe that NCM autonomously synchronizes and directs osteogenic induction, proliferation, differentiation, matrix deposition, mineralization, and matrix remodeling. How NCM accomplishes such a complex task, and what factors are sufficient to replicate this phenomenon, is unknown. Likely candidates may include members and targets of the Transforming Growth Factor-Beta (TGF2) since they are known to play critical roles during osteogenesis, and their expression is altered in chimeras. Therefore, we hypothesize that by modulating levels of TGF? signaling, NCM directs its own osteogenic program and coordinates the activities of osteoclasts to control jaw length. To test our hypothesis, we propose three complementary and non-interdependent Specific Aims. Specific Aim 1 will determine the extent to which NCM employs TGF2 signaling to control jaw length. Specific Aim 2 will determine the extent to which NCM relies on the actions of osteoclasts to regulate jaw length. Specific Aim 3 will determine the extent to which NCM acts via TGF2-dependent RANKL/OPG signaling to affect osteoclast activity and jaw length. We will employ gain- and loss-of-function techniques to identify molecular mechanisms that endow NCM with the ability to control jaw length. Experiments from this proposal can serve as a proof-of-principle that molecular-based therapies can be devised to treat disorders that affect the length of the jaw. Moreover, identifying mechanisms through which donor NCM transduces its effects on host cells such as osteoclasts has implications for repair and regeneration of bones injured by trauma or diseases like osteoporosis and osteonecrosis. We are hopeful that our research will provide a foundation for biologically based, non-surgical methods to remedy a variety of clinical skeletal conditions.