转录因子Isl1是第二心区前体细胞的标志物，在心脏形成中起重要作用。Isl1在流出道持续表达，但作用不明。我们建立了Isl1低表达和心肌特异性敲除的小鼠模型。我们发现，Isl1变异体的心脏表型模拟了人类复杂性先天性心脏病（CHD）的表型。本研究将进一步探讨Isl1在流出道心肌细胞和不同发育阶段前体细胞的增殖、分化和存活中的作用，以及与心脏神经嵴细胞的调控关系；通过转录组学、ChIP-seq和染色质构象位点作用等研究分析，确定Isl1的直接靶点， Isl1介导的增强子/抑制子与启动子相互作用，进一步阐明流出道形成的调控网络并筛选共同靶点和信号通路。本研究将加深我们对流出道形成的调控及人类CHD发生机制的理解，为CHD的早期诊断和预防奠定基础。

Congenital heart disease (CHD) with outflow tract malformation is one of the most common forms of birth defects. However it's etiology and molecular mechanisms remain largely unknown, preventing early diagnosis and prevention. LIM-homedomain transcription factor Isl1 is a marker for cardiac progenitors of the second heart field (SHF). Isl1 is required for these progenitors to contribute to heart formation. However, the molecular mechanism underlying its action remains largely unknown. Isl1 expression persists in outflow tract myocytes. Due to early embryonic lethality and loss of SHF derived cardiac tissues, including the outflow tract, role Isl1 in these differentiated myocytes of the outflow tract remains unknown. We generated several Isl1 mutant mouse lines with reduced Isl1 expression (hypomorphic) or Isl1 being specifically deleted in cardiomycytes with aMHC-Cre. We found that Isl1 mutant mice exhibited severe outflow tract malformations that closely mimic human complex CHDs such as Tetralogy of Fallot and DiGeorge Syndrome. We hypothesized that Isl1, in coordination with other key cardiac transcription factors such as Nkx2.5, plays essential roles in modulating cardiac genetic programs required for specification, proliferation, differentiation, migration and survival of SHF progenitors and outflow tract myocytes, as well as cardiac neural crest. To test these, we will: 1) examine in detail morphogenesis of the outflow tract and pharyngeal great vessels of Isl1 mutants; 2) examine the distribution and number of SHF progenitor cells and their derived myocytes, as well as neural crest cells within pharyngeal arches and outflow tract; and examine their proliferation, differentiation and survival; 3) examine expression of genes known to be essential in outflow tract formation; 4) perform gene profiling to define genetic and epigenetic programs regulated by Isl1 and direct targets of Isl1 in SHF progenitors at different stages and outflow tract myocytes; 5) perform Chromosome Conformation Capture (3C) and Combined 3C-ChIP-Cloning (6C) analysis to uncover specific pattern of promoter-enhancer/repressor interactions mediated by Isl1 and further elucidate molecular mechanisms underlying Isl1’s actions during outflow tract development. Results of proposed studies will provide novel molecular insights into outflow tract formation, and will enhance our understanding of the pathology of human CHDs that ultimately leads to discovery of early diagnosis and prevention.