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)：全前脑畸形是一种常见的出生缺陷(活产为1：16,000，死产为1：250)，并伴有广泛的头面部畸形，从痛苦的眼球旋转到单个中央切牙的轻微症状。它是由腹侧前脑(前轴中线的一部分)的规格缺陷引起的，这随后导致大脑左右半球的不完全分离。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Nodal信号在小鼠胚胎发育中的调控，特别是前轴中线的形成。Node是转化生长因子β超家族的成员，该家族利用激活素I和II受体、Smad2和4以及FoxH1(FAST)所定义的信号通路。重要的是，EGF-CFC胞外蛋白家族的成员，如小鼠Cripto，是Nodal的重要辅助因子。我们以前报道了一个Cripto零等位基因，最近我们通过遗传操作产生了一个Cripto亚型等位基因Cripto 3-loxP。大约50%的CRIPOPT3-loxP/CRIPONull小鼠表现出广泛的中轴线缺陷，类似于全前脑畸形。相反，TGIF是一个同源盒基因，编码一种核蛋白，通过阻断Smad2功能来对抗转化生长因子-β信号转导。有趣的是，人类TGIF基因的突变与全前脑畸形有关，提示其在中轴线形成中发挥作用，可能是通过调节Nodal/Smad2信号通路。基于这些结果，我们将在拟议的研究中追求以下特定目标：i)通过从形态和分子水平详细分析Criplo3-loxP/CriploNull小鼠的缺陷，对其作为前脑腹侧缺陷和HPE的模型系统进行分析；ii)通过鉴定Cripto在小鼠中轴线形成中的功能组织和细胞以及Cripto的下游靶基因，研究Cripto在小鼠轴中线形成中的作用机制；iii)通过产生TGIF零胚胎并检测TGIF对Nodal信号的调节来研究TGIF在小鼠轴中线发育中的作用。这些研究应该会提高我们对哺乳动物中线轴线形成和人类全前脑形成的理解。