RETINOL BINDING PROTEIN AND HEART DEVELOPMENT

描述（申请人的逐字描述）：本实验室的目的 是识别早期开发人员所隐藏的支持和规范因素， 胚胎内胚层细胞，调节心脏发育。我们最近 确定内胚层强烈表达维生素A转运蛋白 甲状腺素运载蛋白（TTR）和视黄醇结合蛋白（RBP）。TTR和 RBP蛋白和mRNA在胚胎中的表达揭示了这些因素 一般与心脏形成区域相关， 尤其是心肌结构。因为发育中的心脏 由于它是视黄醇，特别是视黄酸（RA）的敏感代谢产物， 假设RBP来源于内胚层和定形心肌 细胞是必要的，以调节视黄醇输送到心肌结构， 他们的发展。通过同源重组缺失RBP基因将 用于在多种鼠胚胎模型中检验这一假设。（一） 第一个目标将使用靶向的ES细胞来检查RBP-/- 在胚状体心脏发生过程中发生突变。(2)第二个目标将 利用通过将同源缺陷型RBP-/- ES 桑椹胚期Rosa 26野生型胚胎的细胞组成性表达 β-半乳糖苷酶。从胚胎心脏中排除RBP-/-突变细胞 其器官在其他方面是嵌合的， RBP基因在心脏发育中的作用(3)第三个目标将直接 通过产生RBP基因来建立心脏发育的必要性， 利用四倍体技术从RBP-/- ES细胞获得RBP-/-胚胎 聚合来最后，（4）将制备一系列RBP-敲除小鼠，以延长 这些研究。这些实验的结果将阐明 发育中的心肌对维生素A及其 产物维甲酸（RA）。这些发现将进一步有助于 阐明了先天性心脏缺陷的机制 成人心肌不能修复的原因。

DESCRIPTION (the applicant's description verbatim): This laboratory's objective is to identify support and specification factors that are secreted by early embryonic endoderm cells, which regulate heart development. We have recently determined that endoderm strongly expresses the vitamin A transport proteins transthyretin (TTR) and retinol binding protein (RBP). Mapping sites of TTR and RBP protein and mRNA expression in the embryo has revealed that these factors are associated with the heart forming region in general and with definitive myocardial structures in particular. Because the developing heart is highly sensitive metabolic products of retinol, particularly retinoic acid (RA), it is hypothesized that RBP derived from both endoderm and definitive myocardial cells is necessary to regulate retinol delivery to myocardial structures during their development. Deletion of the RBP gene via homologous recombination will be used to test this hypothesis in a variety of murine embryonic models. (1) The first aim will use targeted ES cells to examine the effect of the RBP-/- mutation during cardiogenesis in embryoid bodies. (2) The second aim will utilize chimeric embryos prepared by combining homozygous-deficient RBP-/- ES cells with morula-stage Rosa26 wild-type embryos that constitutively express b-galactosidase. The exclusion of RBP-/- mutant cells from the heart of embryos whose organs are otherwise chimeric would indicate an autonomous requirement for the RBP gene in heart development. (3) The third aim will directly establish the necessity of the RBP gene for heart development by producing RBP-/- embryos from RBP-/- ES cells using the technique of tetraploid aggregation. Finally, (4) a line of RBP-null mice will be prepared to extend these studies. Results from these experiments will elucidate the dependence of the developing myocardium on carefully regulated levels of vitamin A and its product, retinoic acid (RA). These findings will further contribute to an elucidation of the mechanisms which underlie congenital heart defects as well as the reasons why the adult myocardium is incapable of repair.