TWISTED GASTRULATION AND MANDIBULAR ARCH MORPHOGENESIS

描述（由申请人提供）：大量的人类颅面综合征是第一（下颌）鳃弓（BA 1）发育异常的结果。大多数BA 1间充质细胞来源于头神经嵴细胞（NCC），出现在神经褶皱的侧边缘，在靠近发育中的咽腹侧迁移，并填充BA 1原基。在BA 1水平，NCC从局部环境接收信号，调节其增殖、存活和分化。多种发育途径参与调节BA 1的形态发生，其中骨形态发生蛋白（BMPs）起着重要作用。Twsg 1是一种分泌性蛋白，可与BMP结合并调节其活性。我们已经表明，Twsg 1缺陷小鼠有异常的BA 1形态发生，表现为无颌症，伴有不同程度的颅面缺陷。Twsg 1突变小鼠也显示出前肠内胚层的缺陷，这表明Twsg 1信号传导是前肠发育所必需的。我们的长期目标是了解人类颅面综合征的分子机制。本研究的目的是描述Twsg 1在下颌弓形态发生中的作用。我们的中心假设是，Twsg 1是必需的BA 1和前肠内胚层缺陷的内侧区域的形态发生Twsg 1-/-小鼠影响头部NCC的图案。这项研究的基本原理是，从这项研究中获得的知识将促进我们对BA 1模式的分子和细胞基础的理解，最终可以更好地诊断由BA 1异常发育引起的人类颅面综合征。我们的研究还将告知BMP信号传导的精确调节如何影响复杂的模式化事件，例如下颌骨发育所需的事件。本研究的主要目的是：1）利用NCC和BA 1特异性标记，检测Twsg 1-/-小鼠头侧NCC的形成、迁移和下颌弓的形态发生，以及细胞增殖和凋亡的检测; 2）利用基因芯片技术，鉴定BA 1发育过程中Twsg 1信号通路调控的基因; 3）通过产生Twsg 1的内胚层特异性缺失来鉴定在BA 1的模式化中作为Twsg 1基因作用的主要靶标的细胞; 4）通过将Twsg 1浸泡的珠子植入小鼠下颌外植体中，了解过量的Twsg 1如何影响BA 1形态发生期间BMP信号传导的分子边界。 摘要：下颌发育异常是各种颅面综合征患儿的常见表现。我们已经确定了一个基因，Twsg 1，这是重要的下巴发育的小鼠。由于Twsg 1基因也存在于人类中，并且小鼠和人类的下颌发育相似，因此这项工作可以更好地理解并最终诊断人类颅面综合征。

DESCRIPTION (provided by applicant): A significant number of human craniofacial syndromes are the result of abnormal development of the first (mandibular) branchial arch (BA1). Most of BA1 mesenchyme is derived from cephalic neural crest cells (NCC) that emerge from the lateral edges of the neural folds, migrate ventrally in close proximity to the developing pharynx, and populate BA1 primordia. At the level of BA1, NCCs receive signals from the local environment that regulate their proliferation, survival, and differentiation. Multiple developmental pathways are involved in regulating morphogenesis of BA1, with bone morphogenetic proteins (BMPs) playing a prominent role. Twsg1 is a secreted protein that binds to BMPs and modulates their activities. We have shown that Twsg1-deficient mice have abnormal morphogenesis of BA1, manifesting as agnathia, with variable degrees of accompanying craniofacial defects. Twsg1 mutant mice also show defects in foregut endoderm suggesting that Twsg1 signaling is necessary for foregut development. Our long-range goal is to understand molecular mechanisms underlying human craniofacial syndromes. The objective of the present study is to characterize the role of Twsg1 in mandibular arch morphogenesis. Our central hypothesis is that Twsg1 is required for morphogenesis of the medial region of BA1 and that foregut endoderm deficiency in Twsg1-/- mice affects patterning of cephalic NCC. The rationale for the proposed research is that knowledge obtained from this study will promote our understanding of the molecular and cellular basis of BA1 patterning that can ultimately lead to better diagnosis of human craniofacial syndromes, which result from abnormal development of BA1. Our studies will also inform how precise regulation of BMP signaling affects complex patterning events, such as those required for mandibular development. The following specific aims will be pursued: 1) Examine cephalic NCC formation and migration and mandibular arch morphogenesis in Twsg1-/- mice by using NCC- and BA1-specific markers, as well as assays of proliferation and apoptosis; 2) Identify genes regulated by Twsg1 signaling in BA1 development by using microarray technology; 3) Identify the cells that are the primary target of Twsg1 gene action in patterning of BA1 by generating endoderm-specific deletion of Twsg1; 4) Understand how excess of Twsg1 affects molecular boundaries of BMP signaling during BA1 morphogenesis by implanting Twsg1-soaked beads into mouse mandibular explants. Lay summary: Abnormal development of the lower jaw is a common finding in children with various craniofacial syndromes. We have identified a gene, Twsg1, that is important for jaw development in mice. Since Twsg1 gene is also present in humans and lower jaw development is similar in mice and humans, this work can lead to better understanding and ultimately diagnosis of human craniofacial syndromes.