Characterization of Secondary Heart Field

描述(由申请人提供)：这项建议的长期目标是了解干细胞对心肌谱系的承诺和分化。我们的团队最近发现了一个以前未知的次级心电场，它在鸡胚胎中产生了最终流出道的心肌。我们发现，在心脏循环过程中，通过从次级心场添加心肌细胞而导致的流出延长失败会导致右旋糖化的主动脉。这项应用的总体假设是，干细胞向心肌谱系承诺的过程对所有心肌祖细胞群体都是共同的。在这些实验中要检验的具体假设是：(1)次级心场与初级心场有不同的起源。这将使用三种最先进的鸡胚胎细胞追踪技术来确定。(2)次级心野细胞对心肌细胞系的承诺是由诱导初级心野细胞承诺的同一生长因子家族的成员诱导的。在流出道延长的过程中，其家族成员表达于流出道附近。该家族的特定成员，包括成纤维细胞生长因子-8和骨形态发生蛋白-2，将以不同的方式进行操作，以确定它们在诱导次级心场细胞分化为心肌中的作用。提出的研究将建立二次心场的发展历史。此外，由于流出心肌是正确分隔心脏动脉极的关键，这些研究将增强我们对流出心肌正常发育的认识，并将为圆锥干畸形的基础提供新的见解。

DESCRIPTION (provided by applicant): The long-term objective of this proposal is to understand stem cell commitment and differentiation to a myocardial lineage. Our group has recently discovered a previously unknown secondary heart field that produces the myocardium of the definitive outflow tract in chick embryos. We have found that failure of outflow lengthening by addition of myocardial cells from the secondary heart field during cardiac looping results in dextroposed aorta. The overall hypothesis of the application is that the process of stem cell commitment to a myocardial lineage is common to all myocardial progenitor populations. The specific hypotheses to be tested in these experiments are: (1) The secondary heart field has an origin distinct from the primary heart field. This will be determined using three state-of-the-art cell tracing techniques in chick embryos. (2) Commitment of cells in the secondary heart field to the myocardial lineage is induced by members of the same growth factor families that induce myocardial commitment in the primary heart fields. TGFbeta and FGF family members are expressed in proximity to the outflow tract during its lengthening. Specific members of this family, including FGF-8 and BMP-2, will be manipulated in a variety of ways to determine their role in inducing differentiation of secondary heart field cells into myocardium. The studies proposed will establish the developmental history of the secondary heart field. Furthermore, because the outflow myocardium is critical for correct septation of the arterial pole of the heart, these studies will enhance our knowledge of normal development of the definitive outflow myocardium, and will provide new insights into the basis of conotruncal malformations.