REGULATION OF CARDIAC MORPHOGENESIS

先天性心脏病（CHD）影响了近1%的活产婴儿，经常需要干预 为了防止死亡。虽然这种心脏畸形的有害后果通常是 这些先天性缺陷的原因在出生后就很明显，通常涉及脑内事件的失调。 转录程序控制心脏的规格，图案，分化和形态发生。 Handl和Hand 2是进化上保守的碱性螺旋环抑制（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。处理和 Hand 2最初是共表达的，但随后是循环; Handl主要限于主要 左心室，而Hand 2到右心室。然而，这两种基因仍然共表达在 主动脉囊、流出道（OFT）和室间隔。测试Handl和Hand 2是否具有 不同的生物学功能，我们产生了Hand 1到Hand 2敲入嵌合幼崽。高百分比 嵌合体在出生时死亡并表现出发育不全的左心室和右心室，双出口右心室（DORV）， 以及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，这表明Handl介导的 在早期心脏发育期间的腔室模式是这些新生儿CHD的根本原因。这些数据 支持我们的假设，Hand 1和Hand 2在心脏发生过程中传递独特的转录调节。 除了差异表达，Hand蛋白还可以与许多潜在的bHLH二聚化。 伴侣（E蛋白，Twist家族和Hey 2）提供了另一种调节机制。我们的目标是 鉴定Handl和Hand 2蛋白中不同的功能结构域，其表达所观察到的独特的 功能，并更好地了解所观察到的CHD的分子机制 在一对二的短兵相接中具体目标1：将确定是否心血管异常， Hand 1-to-Hand 2突变体是细胞增殖、存活或左半胱氨酸特异性改变的结果。 和右心室心肌细胞和/或定殖心脏神经嵴。具体目标2将决定 什么基序区分Hand 1和Hand 2功能以及Hand 1和Hand 2如何在功能上与Hey 2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.