Cited 2 Action in Cardiac and Neural Development

描述（由申请人提供）：Cited 2基因敲除小鼠表型表明，Cited 2是一种最近发现的转录激活因子，对圆锥干（心脏流出道）和颅神经管的形态发生至关重要。已知这两种组织在其发育期间都是缺氧的。在体外系统中，Cited 2已被证明能有效地与缺氧诱导因子1-α（HIF-1 α）竞争结合CBP/p300的CH 1结构域，并负调节缺氧反应基因的表达。在Cited 2-/-胚胎中缺氧诱导基因的上调支持了这一假设。因此，Cited 2可能是特别需要的调节缺氧反应，在那些胚胎组织经历最低的氧张力在正常发育过程中。我们将在小鼠和鸡胚胎中测试这一假设，主要关注心脏流出道（OFT）。目的1：确定正常发育所需的细胞类型或细胞类型Cited 2表达。我们将首先详细确定Cited 2蛋白和mRNA在胚胎心脏和神经管形态发生的关键阶段的表达，并与缺氧和凋亡部位进行比较。我们将使用Cre-lox系统特异性敲除神经嵴细胞或心肌细胞中的Cited 2，并分析结果。目标二：使用体内系统测试Cited 2需要与HIF-Ia竞争CBP/p300结合以下调心脏中的缺氧反应的假设。我们将减少Cited 2的行动，特别是在心肌细胞的鸟类OFT和观察的后果形态发生和缺氧反应，包括冠状动脉血管的发展。我们将把Cited 2小鼠与HIF-Ia小鼠杂交，以确定HIF-Ia基因剂量是否可以调节Cited 2的作用，反之亦然。这些研究不仅将为我们了解正常和异常的心脏和神经发育提供关键信息，而且还将阐明体内转录因子和辅助因子之间复杂的相互作用。

DESCRIPTION (provided by applicant): The Cited2 knockout mouse phenotype indicates that Cited2, a recently discovered transcriptional activator, is critical for morphogenesis of the conotruncus (cardiac outflow tract) and the cranial neural tube. Both of these tissues are known to be hypoxic during their development. Cited2 has been shown in in vitro systems to effectively compete with hypoxia-inducible factor 1-alpha (HIF-1alpha) for binding to the CH1 domain of CBP/p300 and to negatively regulate hypoxia-responsive gene expression. Up regulation of hypoxia inducible genes in the Cited2-/- embryo supports this hypothesis. Thus, Cited2 may be especially required for modulating the hypoxia response in those embryonic tissues that experience the lowest oxygen tension during normal development. We will test this hypothesis in mouse and chicken embryos with our main focus on the cardiac outflow tract (OFT). Aim 1: Determine in which cell type or cell types Cited2 expression is required for normal development. We will first determine in detail the expression of the Cited2 protein and mRNA in the embryo at critical stages in heart and neural tube morphogenesis and compare to hypoxic and apoptotic sites. We will specifically knock out Cited2 in the neural crest cells or cardiomyocytes using the Cre-lox system and assay the consequences. Aim 2: Test using in vivo systems the hypothesis that Cited2 is required to compete with HIF-Ia for CBP/p300 binding to down-regulate the hypoxia response in the heart. We will reduce Cited2 action specifically in the cardiomyocytes of the avian OFT and observe the consequences to morphogenesis and the hypoxia response including coronary vascular development. We will cross the Cited2 mice with HIF-Ia mice to determine whether the HIF-Ia gene dosage can modulate Cited2 action and vice versa. These studies will not only provide information critical to our understanding of normal and abnormal heart and neural development but also elucidate the complex interplay between transcription factors and co-factors in vivo.