REGULATION AND EXPRESSION OF GATA TRANSCRIPTION FACTORS

用非洲爪哇和小鸡胚胎进行的经典实验 提示心脏发育的最初步骤包括 心源性中胚层和相邻内胚层之间的相互作用。我们最近 对突变小鼠胚胎的研究表明，转录因子 GATA-4在中胚层和中胚层之间的相互作用中起着至关重要的作用 内胚层。GATA-4在心前中胚层及邻近中胚层表达 内胚层在心管形成和发育同步过程中的作用 前肠内陷。GATA-4基因敲除小鼠在公元前9.5天死亡。和 表现出腹侧形态发生缺陷，包括前肠异常 双侧心肌融合的形成和失败 原始人。相反，高比例的Gata4-/-ES细胞&gt；Gata4+/+ Gata4+/+细胞仅存在于内胚层的嵌合小鼠胚胎 腹侧发育未见异常，提示 内脏和/或最终内胚层中存在野生型细胞 足以让相邻的Gata4-\-的腹面正常发育 中胚层组织。我们假设GATA-4参与了 心肌原基的迁移与融合 皮质靶基因在内胚层中的表达。我们会利用这个优势 这只小鼠固有的遗传优势来表征 内胚层与心源性中胚层相互作用的本质。至 区分GATA-4是内脏表达还是确定性表达 内胚层细胞对心脏形态发生是必不可少的，我们将分析 聚合四倍体细胞产生的嵌合体小鼠的表型 使用Gata4-/-ES细胞或胚胎。此外，我们还将审查 来自宿主胚胎的嵌合体心脏发育 内脏内胚层功能缺陷(例如，HNF-4的突变)。 将利用差异显示和原位杂交技术 鉴定在Gata4-/-内胚层中低表达的基因。我们将互为补充 在小鼠Gata4上的这些实验和对患者的研究 人GATA4基因8p23.1，a附近的染色体缺失 缺失/复制基因座与糖尿病高发相关 先天性心脏病。删除的确切大小和边界 将使用标准技术对一系列患者进行表征 为了检验GATA4单倍体不足与之相关的假设 患有先天性心脏病。这些实验应该会提供一些洞察力 探讨正常心脏和病理性心脏的潜在机制 脊椎动物的发育。

Classical experiments performed with Xenopus and chick embryos have suggested that the initial steps of cardiac development involve an interplay between cardiogenic mesoderm and adjacent endoderm. Our recent studies with mutant mouse embryos have shown that transcription factor GATA-4 plays an essential role in this interaction between mesoderm and endoderm. GATA-4 is expressed in pre-cardiac mesoderm and adjoining endoderm during the simultaneous processes of heart tube formation and foregut invagination. GATA-4 knockout mice die before 9.5 days p.c. and exhibit defects in ventral morphogenesis, including abnormal foregut formation and a failure of fusion of the bilateral myocardial primordia. In contrast, high percentage Gata4-/- ES cell <> Gata4+/+ chimeric mouse embryos in which Gata4+/+ cells populate only endoderm do not exhibit abnormalities in ventral development, indicating the presence of wild type cells in visceral and/or definitive endoderm is sufficient to allow normal ventral development in adjoining Gata4-\- mesodermal tissues. We postulate that GATA-4 participates in the migration and fusion of the myocardial primordia by regulation the expression of cortical target genes in endoderm. We will take advantage of the inherent genetic strengths of this mouse to characterize the nature of the interactions between endoderm and cardiogenic mesoderm. To distinguish whether expression of GATA-4 in visceral or definitive endoderm cells is essential for cardiac morphogenesis, we will analyze the phenotype of chimeric mice produced by aggregating tetraploid cells with either Gata4-/- ES cells or embryos. In addition, we will examine heart development in chimeras derived from host embryos with deficiencies in visceral endoderm function (e.g., mutants in HNF-4). Differential display and in situ hybridization will be utilized to identify genes under-expressed in Gata4-/- endoderm. We will complement these experiments on mouse Gata4 with studies of patients with chromosomal deletions near the human GATA4 gene on 8p23.1, a deletion/duplication locus association with a high incidence of congenital heart disease. The exact size and boundaries of the deletions in a series of patients will be characterized using standard techniques to test the hypothesis that haploinsufficiency of GATA4 is associated with congenital heart disease. These experiments should provide insight into the mechanisms underlying both normal and pathological cardiac development in vertebrates.