Expression profiling of the forming atrioventricular node using a novel Tbx3-based node-specific transgenic reporter. Mus musculus

The atrioventricular (AV) node is a recurrent source of potentially life-threatening arrhythmias. Nevertheless, limited data are available on its developmental control or molecular phenotype. We used a novel AV node-specific reporter mouse to gain insight into the gene programs determining the formation and phenotype of the AV node. In the transgenic reporter, green fluorescent protein (GFP) expression was driven by 160 kbp of Tbx3 and flanking sequences. GFP was selectively expressed in the AV canal of embryos, and in the AV node of adults, while all other Tbx3+ conduction system components, including the AV bundle, were devoid of GFP expression. Fluorescent AV nodal (Tbx3BAC-Egfp) and complementary working (NppaBAC336-Egfp) myocardial cell populations of E10.5 embryos and E17.5 fetuses were purified using fluorescence-activated cell sorting, and their expression profiles were assessed by microarray analysis. We constructed a comprehensive list of sodium, calcium, and potassium channels specific for the nodal or working myocard. Furthermore, the data revealed that the AV node and the working myocardium phenotypes diverge during development, but that the functional gene classes characteristic for both compartments are maintained. Interestingly, the AV node-specific gene repertoire consisted of multiple neurotrophic factors not yet appreciated to play a role in nodal development. These data present the first genome-wide transcription profiles of the AV node during development, providing valuable information concerning its molecular identity. Keywords: Tbx3, AV node, working myocardium, embryonic development, cardiac development, cardiac conduction system Overall design: 24 samples: 6x working myocardium stage E10.5 (NppaBAC336-Egfp mice), 6x AV canal myocardium stage E10.5 (Tbx3BAC-Egfp mice), 6x working myocardium stage E17.5 (NppaBAC336-Egfp mice), 6x AV node myocardium stage E17.5 (Tbx3BAC-Egfp mice)

房室结（atrioventricular node，AV node）是潜在致命性心律失常的常见起源部位。然而，目前关于其发育调控机制与分子表型的研究数据仍较为有限。本研究使用一种新型房室结特异性报告基因小鼠，旨在解析调控房室结形成与表型的基因表达程序。在该转基因报告小鼠中，绿色荧光蛋白（green fluorescent protein，GFP）的表达由160kbp的Tbx3基因及其侧翼序列驱动。GFP仅在胚胎时期的房室管以及成年个体的房室结中选择性表达，而包括房室束在内的其余所有Tbx3阳性传导系统组分均不表达GFP。本研究通过荧光激活细胞分选术（fluorescence-activated cell sorting，FACS），分离获取了胚胎发育第10.5天（E10.5）的房室结心肌细胞群（Tbx3BAC-Egfp）与对应工作心肌细胞群（NppaBAC336-Egfp），以及胚胎发育第17.5天（E17.5）的上述两类细胞群，并通过基因芯片分析对其表达谱进行了检测。本研究构建了房室结与工作心肌特异性的钠、钙、钾离子通道的完整名录。此外，本研究数据显示，房室结与工作心肌的表型在发育过程中逐渐分化，但两类心肌区域各自特有的功能基因类别均得以保留。值得注意的是，房室结特异性基因库中包含多种此前未被发现与结区发育相关的神经营养因子。本研究数据首次提供了发育过程中房室结的全基因组转录谱，为解析其分子特征提供了宝贵的研究资料。
关键词：Tbx3，房室结（atrioventricular node，AV node），工作心肌，胚胎发育，心脏发育，心脏传导系统
实验设计：共包含24个样本：胚胎发育第10.5天的工作心肌样本6份（源自NppaBAC336-Egfp小鼠）、胚胎发育第10.5天的房室管心肌样本6份（源自Tbx3BAC-Egfp小鼠）、胚胎发育第17.5天的工作心肌样本6份（源自NppaBAC336-Egfp小鼠）、胚胎发育第17.5天的房室结心肌样本6份（源自Tbx3BAC-Egfp小鼠）