REGULATION AND EXPRESSION OF GATA TRANSCRIPTION FACTORS

用非洲爪蟾和鸡胚进行的经典实验 表明心脏发育的最初步骤涉及一个 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 加塔-4在中胚层和巨噬细胞之间的这种相互作用中起着重要作用。 内胚层加塔-4在心前中胚层和相邻的中胚层中表达。 在心管形成的同时过程中的内胚层， 前肠内陷加塔-4敲除小鼠在p.c.和 腹部形态发生缺陷，包括前肠异常 形成和融合失败的双边心肌 原基相反，高百分比的Gata 4-/- ES细胞<> Gata 4 +/+ Gata 4 +/+细胞仅分布于内胚层的嵌合小鼠胚胎 在腹部发育中没有表现出异常，表明 内脏和/或定形内胚层中野生型细胞的存在 足以使相邻的Gata 4-\- 中胚层组织我们假设加塔-4参与了 通过调节心肌细胞的细胞周期， 皮质靶基因在内胚层中的表达。我们将利用 这只老鼠固有的遗传优势， 内胚层和心源性中胚层之间相互作用的性质。到 区分加塔-4表达是否在内脏或决定性 内胚层细胞是心脏形态发生所必需的，我们将分析 通过聚集四倍体细胞产生的嵌合小鼠的表型 Gata 4-/- ES细胞或胚胎。此外，我们将研究 来自宿主胚胎的嵌合体的心脏发育 内脏内胚层功能的缺陷（例如，HNF-4中的突变体）。 差异显示和原位杂交将用于 鉴定Gata 4-/-内胚层中低表达基因。我们将补充 这些对小鼠Gata 4的实验以及对患有 在8p23.1上的人类GATA 4基因附近的染色体缺失， 缺失/重复位点与高发病率相关 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GATA 4的单倍不足与GATA 4的单倍不足相关的假设， 患有先天性心脏病这些实验应该能提供 正常和病理性心脏病的机制 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.