Heart Field Development

描述(申请人提供)：项目摘要在胚胎发育过程中，器官前体必须精确定位，以允许关键的诱导性组织-组织相互作用 这驱动了细胞命运规范的发生。然而，心场前体在发育过程中如何定位仍然知之甚少。目前的模型假设所有的心肌和心内膜细胞都来自初级和次级(或前)心场(1？HF和2？HF)。然而，我们最近发现：(I)心房和房室交界处、起搏器、流入和心外膜的许多细胞并不起源于这两种高频中的任何一种；(Ii)令人惊讶的是，它们来自于1？HF和2？HF之后的侧板中胚层(以下称为“第三级HF(3？HF)”)。重要的是，我们的初步研究表明：(3)3？HF的前体以及1？HF和2？HF是最早形成原始条纹的细胞；(4)它们从原始条纹两侧离开，而不越过胚胎中线；(V)在到达每个HF之前，它们迁移时几乎没有横向细胞嵌入。因此，具有PS的HF前体细胞的原始位置预测其定义的目的地在左侧或右侧。尽管PS起源对所有三种HFs都很重要，但关于HF前体如何聚集到PS内的特定位置，以及它们如何对称迁移形成三种HFs的双边情况，人们知之甚少。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，产生一系列子细胞，这些子细胞沿原始条纹的胚胎AP轴排列成阵列；(Vii)原始条纹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心场中胚层模式模式，即PS中定向细胞分裂与中线细胞死亡相结合，在原肠形成之前精确定位HF前体。这项提案将通过确定以下来源来测试此模型： 从原始条纹形成三个HFs的能力(目标1)，定向细胞分裂将单个HFs的前体驱动到原始条纹内的特定结构域的能力(目标2)，以及中线细胞死亡对定义HF前体的左右迁移路径以形成双侧HFs的调节作用(目标3)。综上所述，这项拟议的研究将提供关于心脏前体如何在羊膜中原肠形成的第一个理解，同时确立原始条纹中协调定位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.