Mechanisms of neural crest related heart defects

描述（由申请方提供）：心脏神经嵴细胞（NC）发育缺陷导致主动脉弓动脉重塑缺陷和流出道分隔失败。通过研究斑点（sp2 H）突变小鼠（pax 3突变）的心脏缺陷，我们已经表明，心脏NC不能进行正常的NC干细胞扩增。不足的NC细胞迁移到发育中的心脏。初步数据表明，sp2 H主动脉弓重塑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，已经报道了NC相关的心脏缺陷可以通过将sp突变体与含有msx 2同源框的存活的无效小鼠杂交而在遗传上“拯救”，这表明pax 3是抑制msx 2表达所必需的。鉴于msx 2是BMP信号传导的一种有据可查的调节剂，我们将sp2 H突变体与Bmp 4 -1acZ敲除小鼠杂交。初步结果表明，Bmp 4在sp2 H突变体中过表达，这与可能调节间充质形态发生的几个潜在pax 3效应基因（包括细胞粘附分子periostin）的过表达相关。具体而言，虽然普遍存在的阴阳-1（YY 1）转录因子过表达，但骨膜蛋白在sp2 H中表达不足。骨膜蛋白可能在咽弓和流出道内的NC凝聚和转分化成结缔组织中发挥作用。我们推测通过pax 3/Bmp 4/YY 1调节msx 2表达导致sp2 H心血管缺陷。我们还假设，缺乏骨膜蛋白介导的上皮间充质转化的前心外膜细胞的sp2 H心肌功能障碍的原因。为了确定这些效应基因是否主要或次要受到影响，并将心肌功能障碍与NC相关的心脏缺陷分开，我们产生了pax 3 - 1 oxP小鼠，使我们能够在胚胎发生期间的特定时间在特定组织内重建sp2 H突变。我们将确定心血管系统不同区域内sp2 H突变的影响，如果pax 3直接或间接与YY相互作用，如果pax 3调节骨膜蛋白。

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.