Heart Field Development

描述（由申请人提供）：项目总结在胚胎发生期间，器官前体必须精确定位，以允许关键的诱导组织-组织相互作用 从而驱动细胞命运的发生。心脏领域的前体如何定位在发展过程中，然而，仍然知之甚少。目前的模型假设所有的心肌细胞和内皮细胞都来自原发性和继发性（或前）心脏区域（1 <$HF和2 <$HF）。然而，我们最近发现：（i）心房和房室交界处心肌、起搏器、流入和心外膜的许多细胞并不起源于任何一个HF;（ii）令人惊讶的是，它们来自1 <$HF和2 <$HF后面的侧板中胚层（下文称为“三级HF（3 <$HF）”）。重要的是，我们的初步研究表明：（iii）3 <$HF以及1 <$HF和2 <$HF的前体细胞是形成原条的第一批细胞;（iv）它们从原条两侧退出，而不穿过胚胎中线;（v）迁移时几乎没有侧向细胞嵌入，直到它们到达每个HF。因此，HF前体细胞在PS内的原始位置预测它们在左侧或右侧内的限定目的地。尽管所有三个高频的PS起源的重要性，很少有人知道的HF前体如何填充到PS内的定义的位置，以及它们如何对称地迁移，形成三个高频双边。此外，我们以前的研究已经确定：（vi）1 <$HF和2 <$HF的前体位于胚盘的后端;（g）单个前体细胞进行定向细胞分裂并产生一系列沿着原条的胚胎AP轴排列成阵列的子细胞;（vii）原条的中线细胞独特地经历细胞死亡：最后（viii）抑制中线细胞死亡导致心脏循环的随机化。这些发现导致了一种新的模型，心脏领域中胚层图案，定向细胞分裂在PS加上中线细胞死亡精确定位HF前体原肠胚形成。本提案将通过确定以下因素来检验这一模型： 从原条形成三个HF（Aim 1），定向细胞分裂的能力不驱动单个HF的前体到原条内的限定结构域（Aim 2），以及中线细胞死亡对于限定HF前体的左和右迁移途径以形成双侧HF的调节作用（Aim 3）。综上所述，拟议的研究将提供心脏前体细胞如何在胚胎中形成原肠胚的第一个理解，同时建立协调定位在原始条纹中对最终心源性命运的重要性。

DESCRIPTION (provided by applicant): Project Summary During embryogenesis, organ precursors must be precisely positioned to allow the critical inductive tissue- tissue interactions which drive cell fate specification to occur. How heart field precursors are positioned during development, however, remains poorly understood. The current model assumes that all myocardial and endocardial cells arise from the primary and secondary (or anterior) heart fields (1¿HF and 2¿HF). We have recently found however that: (i) many cells of the atrial and atrioventricular junction myocardium, the pacemaker, inflow, and proepicardium do not originate in either HF; and (ii) surprisingly, they are derived from the lateral plate mesoderm (designated as "the tertiary HF (3¿HF)" hereafter) posterior to the 1¿HF and 2¿HF. Importantly, our preliminary study has revealed that: (iii) precursors of the 3¿HF as well as the 1¿HF and 2¿HF are among the first cells to form the primitive streak; (iv) they exit from the primitive streak bilaterally without crossing the embryonic midline and (v) migrate with little lateral cell intercalation until their arrival at each HF. Thus, an original position of HF precursor cells withn the PS predicts their defined destination within the left or right. Despite the importance of PS-origin for all three HFs, little is known about how the HF precursors populate to the defined position within the PS and how they migrate symmetrically to form the three HFs bilaterally. Further, our previous studies have identified that: (vi) the precursors of the 1¿HF and 2¿HF reside at the posterior end of the blastodisc; (g) individual precursor cells undergo an oriented cell division and generate a series of daughter cells that are aligned as an array along the embryonic AP axis of the primitive streak; (vii) midline cells of the primitive streak uniquely undergo cell death: and finally (viii) inhibition of the midline cell death results in randomizatio of heart looping. These findings lead to a novel model for heart field mesodermal patterning whereby oriented cell division in the PS coupled with midline cell death precisely position HF precursors prior to gastrulation. This proposal will test this model by determining: the origin and formation of three HFs from the primitive streak (Aim 1), the ability of a oriented cell division t drive precursors of individual HFs to defined domains within the primitive streak (Aim 2), and the regulatory role of midline cell death for defining the left and right migration pathways of HF precursors to form bilateral HFs (Aim 3). Taken together, the proposed study will provide the first understanding of how cardiac precursors gastrulate in amniotes, while establishing the importance of coordinated positioning in the primitive streak to ultimate cardiogenic fate.