Regulation of Nodal Signaling in Holoprosencephaly

前脑无裂畸形的节点信号传导调节

• 批准号: 6954594
• 负责人: Jixiang Ding
• 金额: $ 9.53万
• 依托单位: UNIVERSITY OF LOUISVILLE
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6954594
• 关键词: activins; biological signal transduction; brain morphology; congenital brain disorder; developmental neurobiology; embryogenesis; gene expression profiling; gene mutation; gene targeting; growth factor receptors; in situ hybridization; microarray technology; molecular biology; pathologic process; prosencephalon; tissue /cell culture; transforming growth factors

DESCRIPTION (provided by applicant): Holoprosencephaly represents a common birth defect (1:16,000 in live births and 1:250 in stillbirths) with a broad spectrum of craniofacial malformations ranging from distressful cyclopia to mild symptom of a single central incisor. It is caused by defects in the specification of the ventral forebrain (a part of the anterior axial midline), which subsequently lead to incomplete separation of the brain into the left and right hemispheres. Recent studies indicated that Nodal signaling plays a central role in controlling midline development, we therefore will focus on the regulation of Nodal signaling in mouse embryogenesis with a special interest in anterior axial midline formation. Nodal is a member of the transforming growth factor beta (TGF-beta) superfamily that utilizes a signaling pathway defined by Activin type I and II receptors, Smad2 and 4, and FoxH1(FAST). Importantly, members of the EGF-CFC family of extracellular proteins such as mouse Cripto are essential co-factors for Nodal. We previously reported a Cripto null allele, and recently we generated a Cripto hypomorphic allele, Cripto3-loxP, by genetic manipulation. Approximately 50% of the Cripto3-loxP/CriptoNull mice displayed a wide range of axial midline defects resembling holoprosencephaly. In contrast, TGIF is a homeobox gene encoding a nuclear protein that antagonizes TGF-beta signaling by blocking Smad2 function. Interestingly, mutations in human TGIF gene are associated with holoprosencephaly, suggesting its function in axial midline formation, presumably through regulating Nodal/Smad2 signaling pathway. Based on these results, we will pursue the following specific aims in the proposed research: I) Analysis of the Cripto3-loxP/CriptoNull mice as a model system for ventral forebrain defects and HPE by detailed analysis of the defects in Cripto3-loxP/CriptoNull mice at morphology and molecular levels; II) Investigation of mechanisms underlying Cripto function in mouse axial midline formation by identifying the tissues and cells where Cripto is functioning and downstream target genes of Cripto; III) Investigation of TGIF function in mouse axial midline development by generating TGIF null embryos and examining the modulation of Nodal signaling by TGIF. These studies should improve our understanding of mammalian axial midline formation and human holoprosencephaly.

描述（由申请人提供）：前脑无裂畸形是一种常见的出生缺陷（活产中的比例为 1:16,000，死产中的比例为 1:250），具有广泛的颅面畸形，从令人痛苦的独眼到单个中切牙的轻微症状。它是由腹侧前脑（前轴中线的一部分）的规格缺陷引起的，随后导致大脑不完全分离为左右半球。最近的研究表明，Nodal 信号在控制中线发育中起着核心作用，因此，我们将重点关注小鼠胚胎发生中 Nodal 信号的调节，特别关注前轴中线的形成。 Nodal 是转化生长因子 β (TGF-β) 超家族的成员，该家族利用由激活素 I 型和 II 型受体、Smad2 和 4 以及 FoxH1(FAST) 定义的信号传导通路。重要的是，细胞外蛋白 EGF-CFC 家族的成员（例如小鼠 Cripto）是 Nodal 的重要辅助因子。我们之前报道了一个 Cripto 无效等位基因，最近我们通过基因操作生成了一个 Cripto 亚等位基因 Cripto3-loxP。大约 50% 的 Cripto3-loxP/CriptoNull 小鼠表现出广泛的轴向中线缺陷，类似于前脑无裂畸形。相比之下，TGIF 是一种同源盒基因，编码一种核蛋白，通过阻断 Smad2 功能来拮抗 TGF-β 信号传导。有趣的是，人类 TGIF 基因的突变与前脑无裂畸形相关，表明其在中线形成中发挥作用，可能是通过调节 Nodal/Smad2 信号通路来实现的。基于这些结果，我们将在拟议的研究中追求以下具体目标：I）通过在形态和分子水平上详细分析 Cripto3-loxP/CriptoNull 小鼠的缺陷，将 Cripto3-loxP/CriptoNull 小鼠作为腹侧前脑缺陷和 HPE 的模型系统进行分析； II) 通过鉴定 Cripto 发挥功能的组织和细胞以及 Cripto 的下游靶基因，研究 Cripto 在小鼠轴中线形成中发挥作用的机制； III)通过生成TGIF无效胚胎并检查TGIF对Nodal信号的调节来研究TGIF在小鼠中线发育中的功能。这些研究应该提高我们对哺乳动物轴中线形成和人类前脑无裂畸形的理解。