REGULATION OF CARDIAC MORPHOGENESIS

先天性心脏病(CHDS)影响了几乎1%的活产，经常需要干预 为了防止死亡。尽管这种心脏畸形的有害后果通常是 这些先天缺陷的原因在出生后很明显，通常涉及到体内事件的失调。 控制心脏规格、构型、分化和形态发生的转录程序。 Hand1和Hand2是进化保守的碱性螺旋-环-螺旋(BHLH)转录因子 在心脏发育过程中表现出部分重叠的时空表达模式。手柄和 Hand2最初是共表达的，但在循环之后；Hand1主要限于主要 左心室，而手2指向右心室。然而，这两个基因仍然在 主动脉囊、流出道(OFT)和室间隔。测试Hand1和Hand2是否有 不同的生物学功能，我们产生了Hand1-to-Hand2敲门嵌合幼崽。高百分比 嵌合体在出生时死亡，表现为左右心室发育不良，右心室双出口(DORV)， 肌性和膜性室间隔缺损(VSD)。观察到的表型发生在 特别是在内源性Handl表达的地方，表明手介导的原始缺陷 心脏发育早期的心腔模式是这些新生儿先天性心脏病的根本原因。这些数据 支持我们的假设，即Hand1和Hand2在心脏发生过程中传递独特的转录调节。 除了差异表达外，手部蛋白还可以与一些潜在的bHLH二聚化 合作伙伴(E-蛋白、Twist-Family和Hey2)提供了另一种调节机制。我们的目标是 确定Hand1和Hand2蛋白中表达所观察到的独特的不同功能结构域 功能和更好地理解观察到的CHD背后的分子机制/S 在1对2的敲门狗中。具体目标1：将确定心血管异常是否在 Hand1-to-Hand2突变体是细胞增殖、存活或左半身规格改变的结果 和右室心肌细胞和/或定植心脏神经脊。具体目标2将决定 Hand1和Hand2的功能有何不同，Hand1和Hand2在功能上如何与Hey2相互作用。

Congenital heart defects (CHDs) affect almost 1% of all live human births and frequently require intervention in order to prevent death. Although the deleterious consequences of such cardiac malformations are usually evident after birth, the causes of these congenital defects frequently involve disregulation of events within the transcriptional programs that control cardiac specification, patterning, differentiation and morphogenesis. Handl and Hand2 are evolutionary conserved basic Helix-Loop-Helix (bHLH) transcription factors that exhibit partially overlapping spatiotemporal expression patterns during cardiac development. Handl and Hand2 are initially co-expressed, but following looping; Handl is predominantly restricted to predominantly the left ventricle, whereas Hand2 to the right ventricle. However, both genes remain co-expressed in the aortic sac, outflow tract (OFT) and the interventricular septum. To test whether Handl and Hand2 have distinct biological functions, we generated Hand1-to-Hand2 knockin chimeric pups. High percentage chimeras die at birth and exhibit hypoplastic left and right ventricles, double-outlet right ventricle (DORV), and both muscular and membranous interventricular septal defects (VSDs). The observed phenotypes occur specifically where endogenous Handl is expressed, suggesting that primary defects in Hand-mediated chamber patterning during early heart development is the root cause of these neonatal CHDs. These data support our hypothesis that Handl and Hand2 convey unique transcriptional regulation during cardiogenesis. In addition to differential expression, Hand proteins can also dimerize with a number of potential bHLH partners (E-proteins, Twist-family, and Hey2) providing yet another regulatory mechanism. Our goals are to identify the distinct functional domains in Handl and Hand2 proteins that convey the observed unique functions and to gain a better understanding of the molecular mechanism/s that underlie the CHDs observed in the Hand1-to-Hand2 knockin pups. Specific Aim 1:Will determine if the cardiovascular anomalies in the Hand1-to-Hand2 mutants are the result of alterations in cell proliferation, survival, or specification of the left and right ventricular cardiomyocytes and/or colonizing cardiac neural crest. Specific Aim 2 will determine what motifs distinguish Handl and Hand2 function and how Handl and 2 functionally interact with Hey2.