Genetic Pathways Directing Ventral Folding Morphogenesis in Mammalian Embryos

指导哺乳动物胚胎腹侧折叠形态发生的遗传途径

• 批准号: 8814123
• 负责人: ELIZABETH H LACY
• 金额: $ 46.91万
• 依托单位: SLOAN-KETTERING INST CAN RESEARCH
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-15 至 2016-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8814123
• 关键词: Alleles; Anterior; BMP2 gene; Bilateral; Biological Assay; Bone Morphogenetic Proteins; Cardiac; Cell Lineage; Cells; Cellular biology; Congenital Abnormality; Congenital Heart Defects; Development; Developmental Process; Ectoderm; Ectopia Cordis; Elements; Embryo; Endoderm; Epiblast; Fetus; Future; Gastroschisis; Generations; Genetic; Genetic Transcription; Genetic study; Goals; Head; Heart; Human; Impairment; Intestines; Knowledge; LacZ Genes; Lateral; Live Birth; Location; Mammals; Maps; Medial; Mediating; Membrane; Mesoderm; Morphogenesis; Mus; Mutant Strains Mice; Neuroectoderm; Pathway interactions; Phenotype; Play; Population; Positioning Attribute; Pregnancy; Primitive foregut structure; Process; Property; Receptor Signaling; Reporter; Role; Signal Pathway; Signal Transduction; Staging; Thoracic cavity structure; Tissues; Transgenes; Transgenic Mice; Transgenic Organisms; Tube; Visceral; abdominal wall; bone morphogenetic protein receptors; cell behavior; cell type; cis acting element; expression vector; gastrulation; heart primordium; in vivo; mutant; receptor function; stomach cardia

DESCRIPTION (provided by applicant): The overall goal of this project is to elucidate the genetic pathways and cellular mechanism that mediate ventral folding morphogenesis. Human embryos undergo ventral folding morphogenesis during the fourth week of gestation. Despite the different topologies of the epiblast in early human and mouse embryos (a flat disc in the former, a hollow cylinder in the latter), a number of key aspects of ventral folding morphogenesis are conserved: internalization of the gut, formation of a linear heart tube, closure of the ventral body wall, and encasement of the fetus in the amniotic membrane. Abnormalities in ventral morphogenesis underlie a number of birth defects associated with incomplete body wall closure (gastroschisis, development of intestines outside the abdominal wall; ectopia cordis, location of heart outside the thoracic cavity); such aberrations of ventral folding occur in ~ 1/2000 live births. An absence of knowledge about the signaling pathways and cell populations directing ventral folding morphogenesis in mammals has precluded systematic study of the genetics and cell biology underlying this developmental process. The proposed studies build directly on our recent finding that the Anterior Visceral Endoderm (AVE), a well defined signaling center in the pre-streak (PS) and Early Streak (ES) mouse embryo, plays a central role in initiating and directing anterior ventral folding morphogenesis. Tissue-specific mouse mutant analyses have shown that the Bone Morphogenetic Protein (BMP) pathway is a key regulator of anterior ventral folding morphogenesis. BMP2 expressed by the AVE signals to epiblast derivatives during gastrulation to orchestrate the initial stages of ventra morphogenesis; including formation of the foregut invagination and placement of the heart caudal to the head. Our central hypothesis is that AVE-expressed BMP2 directs foregut invagination and head fold morphogenesis by signaling to one or more distinct epiblast-derived cell types: gut endoderm, anterior neuroectoderm, and/or cardiac mesoderm. Upon receipt of the AVE-derived BMP2 signal, target tissues undergo morphogenetic changes in cell behaviors that coordinate the generation of foregut invagination with a rostral-caudal shift in the positions of head and heart. Three specific aims will investigate this hypothesis. Aim 1 uses lineage-specific Cre transgenes and a conditional allele of Bmpr1a to determine if AVE-expressed Bmp2 signals to definitive endoderm, ectoderm and/or mesoderm to initiate ventral folding morphogenesis. Aim 2 investigates whether a VE specific null allele of Bmp2 genetically interacts with null alleles of Gata4 and Hgs/Hrs, mutants known to also disrupt ventral folding morphogenesis. Aim3 maps cis-acting elements that target transcription to the proximal AVE using Bmp2-LacZ BAC reporter transgenic mouse lines; this will allow us to develop expression vectors for in vivo studies on the functional properties of the BMP2-expressing population in the proximal AVE.

描述（由申请人提供）：该项目的总体目标是阐明介导腹侧折叠形态发生的遗传途径和细胞机制。人类胚胎在妊娠第四周经历腹侧折叠形态发生。尽管早期人类和小鼠胚胎的外胚层具有不同的拓扑结构（前者为扁平盘，后者为空心圆柱体），但腹侧折叠形态发生的许多关键方面是保守的：肠道的内化、线性心管的形成、腹侧体壁的闭合以及胎儿被羊膜包裹。腹侧形态发生异常是许多与体壁闭合不完全相关的出生缺陷的基础（腹裂，肠在腹壁外发育；心异位，心脏位于胸腔外）；这种腹侧折叠异常发生在约 1/2000 的活产婴儿中。 由于缺乏对哺乳动物腹侧折叠形态发生的信号通路和细胞群的了解，无法对这一发育过程的遗传学和细胞生物学进行系统研究。拟议的研究直接建立在我们最近的发现之上，即前内脏内胚层（AVE）是前条纹（PS）和早期条纹（ES）小鼠胚胎中明确的信号中心，在启动和指导前腹侧折叠形态发生中发挥着核心作用。组织特异性小鼠突变分析表明，骨形态发生蛋白（BMP）途径是前腹侧折叠形态发生的关键调节因子。原肠胚形成过程中 AVE 向外胚层衍生物发出信号，协调腹腔形态发生的初始阶段；包括前肠内陷的形成和心脏尾部到头部的位置。 我们的中心假设是，AVE 表达的 BMP2 通过向一种或多种不同的外胚层衍生细胞类型（肠内胚层、前神经外胚层和/或心脏中胚层）发出信号来指导前肠内陷和头褶形态发生。收到 AVE 衍生的 BMP2 信号后，靶组织会发生细胞行为的形态发生变化，从而协调前肠内陷的产生与位置的头尾移位 的头和心。三个具体目标将研究这一假设。目标 1 使用谱系特异性 Cre 转基因和 Bmpr1a 的条件等位基因来确定 AVE 表达的 Bmp2 是否向定形内胚层、外胚层和/或中胚层发出信号以启动腹侧折叠形态发生。目标 2 研究 Bmp2 的 VE 特异性无效等位基因是否与 Gata4 和 Hgs/Hrs 的无效等位基因发生遗传相互作用，已知这些突变体也会破坏腹侧折叠形态发生。 Aim3 使用 Bmp2-LacZ BAC 报告基因转基因小鼠系定位顺式作用元件，将转录靶向近端 AVE；这将使我们能够开发表达载体，用于体内研究近端 AVE 中 BMP2 表达群体的功能特性。