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Abstract：
Congenital heart defects (CHDs) affecting the cardiac outflow tract (OFT) constitute a significant cause of morbidity and mortality. The OFT develops from migratory cell populations which include the cardiac neural crest cells (cNCCs) and secondary heart field (SHF) derived myocardium and endocardium. The related transcription factors HAND1 and HAND2 have been implicated in human CHDs involving the OFT. Although Hand1 is expressed within the OFT, Hand1 NCC-specific conditional knockout mice (H1CKOs) are viable. Here we show that these H1CKOs present a low penetrance of OFT phenotypes, whereas SHF-specific Hand1 ablation does not reveal any cardiac phenotypes. Further, HAND1 and HAND2 appear functionally redundant within the cNCCs, as a reduction/ablation of Hand2 on an NCC-specific H1CKO background causes pronounced OFT defects. Double conditional Hand1 and Hand2 NCC knockouts exhibit persistent truncus arteriosus (PTA) with 100% penetrance. NCC lineage-tracing and Sema3c in situ mRNA expression reveal that Sema3c-expressing cells are mis-localized, resulting in a malformed septal bridge within the OFTs of H1CKO;H2CKO embryos. Interestingly, Hand1 and Hand2 also genetically interact within the SHF, as SHF H1CKOs on a heterozygous Hand2 background exhibit Ventricular Septal Defects (VSDs) with incomplete penetrance. Previously, we identified a BMP, HAND2, and GATA-dependent Hand1 OFT enhancer sufficient to drive reporter gene expression within the nascent OFT and aorta. Using these transcription inputs as a probe, we identify a novel Hand2 OFT enhancer, suggesting that a conserved BMP-GATA dependent mechanism transcriptionally regulates both HAND factors. These findings support the hypothesis that HAND factors interpret BMP signaling within the cNCCs to cooperatively coordinate OFT morphogenesis.
摘要：
影响心脏流出道（OFT）的先天性心脏缺陷（CHD）是发病率和死亡率的重要原因。OFT从包括心脏神经c细胞（cNCC）和次级心脏视野（SHF）衍生的心肌和心内膜的迁移细胞群发展而来。相关转录因子HAND1和HAND2与涉及OFT的人类CHD有关。尽管Hand1在OFT中表示，Hand1NCC特异性条件性敲除小鼠(H1CKOs)是可行的。在这里，我们显示这些H1CKO呈现OFT表型的低外显率，而SHF特异性Hand1消融不显示任何心脏表型。Further,HAND1和HAND2在cNCC中出现功能冗余，由于Hand2在NCC特异性H1CKO背景上的减少/消融导致明显的OFT缺陷。双条件Hand1和Hand2NCC敲除表现出持续的动脉干（PTA），外显率为100％。NCC谱系追踪和Sema3c原位mRNA表达表明，Sema3c表达细胞定位错误，导致S1CKO；H2CKO胚胎的OFTs内出现畸形的间隔桥。有趣的是,Hand1和Hand2也在SHF内发生遗传相互作用，由于Hand2杂合背景上的SHFH1CKOs表现出室间隔缺损（VSD），外显率不完全。以前,我们确定了一个BMP,HAND2和GATA依赖性Hand1OFT增强子足以驱动新生OFT和主动脉内的报告基因表达。使用这些转录输入作为探针，我们确定了一种新的Hand2OFT增强子，提示保守的BMP-GATA依赖性机制在转录上调节两种HAND因子。这些发现支持HAND因子解释cNCC内的BMP信号以协同协调OFT形态发生的假设。
