CHARACTERIZATION & MODIFICATION OF CARDIAC NEURAL CREST

对神经嵴消融的鸡胚胎的多学科研究表明，在完整胚胎的神经嵴细胞到达心脏之前，心肌功能就发生了改变。心肌功能障碍初见时，心脏神经衣细胞与咽部背外侧缘接触。我们最近发现离体咽部内胚层在培养心肌中也能引起类似的变化。该效应可被FGF多克隆中和抗体阻断。这些观察结果导致了以下假设：1)神经嵴细胞与内胚层的相互作用是抑制fgf样信号所必需的，而fgf样信号会导致神经嵴细胞心肌发育异常，从而抑制内胚层来源的信号。这些假设将首先通过神经嵴、内胚层和心肌中FGF配体和受体的局部表达进行验证，然后在体外进行神经嵴和/或内胚层与心肌的组织重组。在组织重组和外植体培养中，将使用各种技术来干扰FGF信号。在组织重组和外植体培养中，将使用各种技术来干扰FGF信号。神经嵴消融和背部移植将用于改变FGF调节因子的表达，并干扰完整胚胎中的FGF信号传导。最后，我们将过量的维甲酸应用于神经嵴细胞，以改变神经嵴调节FGF信号传导机制的能力。提出的实验将阐明心脏神经嵴细胞以前未被认识的功能，并表征神经嵴细胞与咽部内胚层的相互作用。这些相互作用似乎对正常的心肌发育至关重要，如果没有它们，心肌发展史就会改变。我们认为这可能导致神经嵴相关心脏缺陷患儿即使在手术修复后仍有较高的死亡率。

Multi-disciplinary studies of chick embryos that neural crest ablation have shown that myocardial function is altered prior to the time that neural crest cells would be expected to reach the heart in intact embryos. At the time when myocardial dysfunction can first be seen, the cardiac neural cress cells are in contact with the dorsolateral margin of the pharynx. We have recently found that isolated pharyngeal endoderm can cause similar changes in cultured myocardium. The effect can be blocked by a polyclonal neutralizing antibody to FGF. These observations have led to the hypothesis that 1) an interaction of neural crest cells with endoderm is required for suppression of an FGF-like signal that leads to abnormal myocardial development in neural crest cells to suppress the endodermally-derived signal. The hypotheses will be tested first by localizing expression of FGF ligands and receptors in neural crest, endoderm, and myocardium and then in tissue recombinations of neural crest and/or endoderm with myocardium in vitro. Various techniques will be used to interfere with FGF signaling in the tissue recombinations and in explant cultures. Various techniques will be used to interfere with FGF signaling in the tissue recombinations and in explant cultures. Neural crest ablations and back-transplantations will be used to modify expression of FGF modulating factors and to interfere with FGF signaling in intact embryos. Finally, we will apply excess retinoic acid to neural crest cells to alter the ability of neural crest to modulate the FGF signaling mechanism. The experiments proposed will elucidate a previously unrecognized function of cardiac neural crest cells and characterize the interactions of neural crest cells with pharyngeal endoderm. These interactions appear to be critical for normal myocardial development and in their absence, myocardial developmental history is altered. We believe that this may lead to the high mortality in children with neural crest-related heart defects even after surgical repair.