Mechanisms of neural crest related heart defects

描述(由申请人提供)：心脏神经脊细胞(NC)发育缺陷导致主动脉弓动脉重构缺陷和流出道分离失败。通过研究斑点(Sp2H)突变小鼠(Pax3突变)的这种心脏缺陷，我们发现心脏NC无法经历正常的NC干细胞扩张。不足的NC细胞迁移到发育中的心脏。初步数据表明，Sp2H主动脉弓重构和流出道缺陷继发于心肌功能障碍(兴奋-收缩偶联不良)。令人惊讶的是，有报道称，与NC相关的心脏缺陷可以通过将sp突变体与存活的含有MSX2同源盒的空小鼠杂交而得到基因上的拯救，这表明Pax3是抑制MSX2表达所必需的。鉴于MSX2是BMP信号的调节者，我们将sp2H突变体与Bmp4-1acZ基因敲除小鼠进行杂交。初步结果表明，Bmp4在sp2H突变体中过度表达，这与几个可能调节间充质形态发生的潜在Pax3效应基因(包括细胞黏附分子Periostin)的过度表达有关。具体地说，虽然普遍存在的阴阳1(YY1)转录因子过度表达，但Periostin在sp2H中表达不足。Periostin可能在NC凝聚和转分化为咽弓和流出道内的结缔组织中发挥作用。我们假设，通过Pax3/Bmp4/YY1调节MSX2的表达导致了sp2H心血管缺陷。我们还假设，缺乏Periostin介导的心前膜细胞上皮-间充质转化是Sp2H心肌功能障碍的原因。为了确定这些效应基因是主要还是继发性受到影响，并将心肌功能障碍与NC相关的心脏缺陷区分开来，我们培育了一只Pax3-1oxP小鼠，使我们能够在胚胎发育的特定时间在特定组织内重新产生sp2H突变。我们将确定Sp2H突变在心血管系统不同区域的影响，Pax3是否直接或间接与YY相互作用，Pax3是否调节Periostin。

DESCRIPTION (provided by applicant): Deficiencies in cardiac neural crest cell (NC) development result defective remodeling of the aortic arch arteries and failure of outflow tract septation. By studying this heart defect in splotch (sp2H) mutant mice (mutation in pax3), we have shown that cardiac NC fail to undergo normal NC stem cell expansion. Insufficient NC cells migrate into the developing heart. Preliminary data indicate that sp2H aortic arch remodeling and outflow tract defects are secondary to myocardial dysfunction (poor excitation-contraction coupling). Surprisingly, it has been reported that the NC-associated heart defects can be genetically 'rescued' by crossing the sp mutants to the viable msx2 homeobox-containing null mice, demonstrating that pax3 is required for the repression of msx2 expression. Given that msx2 is a well-documented regulator of BMP signaling, we crossed the sp2H mutants with the Bmp4-1acZ knockout mice. Preliminary results indicate that Bmp4 is over-expressed in sp2H mutants and this is correlated with over-expression of several potential pax3 effector genes that may regulate mesenchymal morphogenesis (including the cell adhesion molecule periostin). Specifically, while the ubiquitous Yin Yang-1 (YY1) transcription factor is over-expressed, periostin is under-expressed in sp2H. Periostin may play a role in NC condensation and trans-differentiation into connective tissue within the pharyngeal arches and outflow tract. We hypothesize that modulation of msx2 expression via pax3/Bmp4/YY1 causes the sp2H cardiovascular defects. We also hypothesize that a lack of periostin-mediated epithelial-mesenchymal transformation of proepicardial cells causes the sp2H myocardial dysfunction. To determine whether these effector genes are primarily or secondarily affected and to separate the myocardial dysfunction from the NC-associated heart defects, we generated a pax3-1oxP mouse enabling us to re-create the sp2H mutation, within particular tissues at particular times during embryogenesis. We will determine the effects of the sp2H mutation within different regions of the cardiovascular system, if pax3 interacts directly or indirectly with YY and if pax3 regulates periostin.