Project I-- CHARACTERIZATION & MODIFICATION OF CARDIAC NEURAL CREST

鸡胚神经嵴消融的多学科研究表明，在神经嵴细胞预期到达完整胚胎心脏之前，心肌功能发生了改变。当心肌功能障碍首次出现时，心脏神经鞘细胞与咽的背外侧缘接触。我们最近发现，分离的咽内胚层可以引起类似的变化，在培养的心肌。 该作用可被FGF的多克隆中和抗体阻断。这些观察结果导致了这样的假设：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，该信号导致神经嵴细胞中心肌发育异常，从而抑制内胚层来源的信号。首先通过在神经嵴、内胚层和心肌中定位FGF配体和受体的表达，然后在体外神经嵴和/或内胚层与心肌的组织重组中定位FGF配体和受体的表达来测试假设。将使用各种技术来干扰组织重组和外植体培养中的FGF信号传导。将使用各种技术来干扰组织重组和外植体培养中的FGF信号传导。神经嵴消融和背部移植将用于修改FGF调节因子的表达，并干扰完整胚胎中的FGF信号传导。最后，我们将过量的视黄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。实验将阐明一个以前未被认识到的心脏神经嵴细胞的功能，并表征神经嵴细胞与咽内胚层的相互作用。这些相互作用似乎对正常心肌发育至关重要，如果没有它们，心肌发育史就会改变。我们认为，这可能会导致高死亡率的儿童神经嵴相关的心脏缺陷，即使在手术修复。

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.