TWISTED GASTRULATION AND MANDIBULAR ARCH MORPHOGENESIS

描述（由申请人提供）：大量人类颅面综合征是第一（下颌）鳃弓（BA1）发育异常的结果。大多数 BA1 间充质源自头侧神经嵴细胞 (NCC)，这些细胞从神经皱襞的侧边缘出现，向腹侧迁移，靠近发育中的咽，并填充 BA1 原基。在 BA1 水平上，NCC 接收来自局部环境的信号，调节其增殖、生存和分化。 BA1 的形态发生涉及多种发育途径，其中骨形态发生蛋白 (BMP) 发挥着重要作用。 Twsg1 是一种分泌蛋白，可与 BMP 结合并调节其活性。我们发现，Twsg1 缺陷小鼠的 BA1 形态发生异常，表现为无颌，伴有不同程度的颅面缺陷。 Twsg1 突变小鼠还表现出前肠内胚层缺陷，表明 Twsg1 信号传导对于前肠发育是必需的。我们的长期目标是了解人类颅面综合征的分子机制。本研究的目的是表征 Twsg1 在下颌牙弓形态发生中的作用。我们的中心假设是 Twsg1 对于 BA1 内侧区域的形态发生是必需的，并且 Twsg1-/- 小鼠的前肠内胚层缺陷会影响头部 NCC 的模式。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 BA1 模式的分子和细胞基础的理解，最终可以更好地诊断由 BA1 异常发育引起的人类颅面综合征。我们的研究还将揭示 BMP 信号传导的精确调节如何影响复杂的模式事件，例如下颌发育所需的事件。我们将追求以下具体目标：1）通过使用NCC和BA1特异性标记物以及增殖和凋亡测定，检查Twsg1-/-小鼠的头侧NCC形成和迁移以及下颌弓形态发生； 2) 利用微阵列技术鉴定BA1发育过程中受Twsg1信号调节的基因； 3) 通过生成 Twsg1 的内胚层特异性缺失，鉴定 Twsg1 基因在 BA1 模式中作用的主要靶标细胞； 4) 通过将 Twsg1 浸泡的珠子植入小鼠下颌外植体，了解过量的 Twsg1 如何影响 BA1 形态发生过程中 BMP 信号传导的分子边界。 简单总结：下颌发育异常是患有各种颅面综合征的儿童的常见现象。我们已经鉴定出一种基因 Twsg1，它对小鼠下颌发育非常重要。由于 Twsg1 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.