Mechanisms of neural crest related heart defects

描述（由申请人提供）：心脏神经嵴细胞（NC）发育缺陷导致主动脉弓重塑缺陷和流出道分离失败。通过研究斑点（sp2H）突变小鼠的心脏缺陷（pax3突变），我们发现心脏NC不能进行正常的NC干细胞扩增。没有足够的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损是继发于心肌功能障碍（兴奋-收缩耦合不良）。令人惊讶的是，有报道称，通过将sp突变体与含有msx2同源盒的存活小鼠杂交，nc相关的心脏缺陷可以在遗传上得到“拯救”，这表明pax3是抑制msx2表达所必需的。鉴于msx2是BMP信号的良好调节因子，我们将sp2H突变体与Bmp4-1acZ敲除小鼠杂交。初步结果表明，Bmp4在sp2H突变体中过度表达，这与几种可能调节间质形态发生的潜在pax3效应基因（包括细胞粘附分子periostin）的过度表达有关。具体来说，虽然普遍存在的阴阳-1 （YY1）转录因子过表达，但在sp2H中，periostin表达不足。在咽部弓和流出道内，骨膜蛋白可能在NC凝聚和向结缔组织的反分化中起作用。我们假设通过pax3/Bmp4/YY1调节msx2表达导致sp2H心血管缺陷。我们也假设缺乏骨膜蛋白介导的心外膜前细胞上皮-间质转化导致sp2H心肌功能障碍。为了确定这些效应基因是主要还是次要受到影响，并将心肌功能障碍与nc相关的心脏缺陷分离开来，我们制造了一只pax3-1oxP小鼠，使我们能够在胚胎发生的特定时间的特定组织中重建sp2H突变。我们将确定sp2H突变对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.