The role of Lmp4 in the regulation of the cardiac transcription factor Tbx5

描述（由申请人提供）：先天性心脏缺陷是影响人类的最普遍和最严重的疾病之一。因此，对受影响的个人，家庭和社会的不利影响强调了在器官和细胞水平上更好地了解潜在分子事件的必要性。心血管系统特别受到改变的T-box基因功能的影响。脊椎动物基因组包含至少18个不同的T-box（Tbx）基因的家族。其中，Tbx 5在各种心脏谱系和结构中具有功能，并且人类TBX 5的突变导致Holt-Oram综合征（HOS），这是一种以先天性心脏和肢体缺陷为特征的疾病。这种心脏/肢体疾病的心脏表现从房间隔缺损和室间隔缺损到复杂畸形如法洛四联症不等。HOS表型可以由Tbx 5的量减少或增加引起，表明Tbx蛋白的水平对于正常功能至关重要。尽管它们在胚胎发生和疾病中的重要性，但编码的转录因子发挥其功能的机制尚不清楚。该项目的长期目标是阐明Tbx 5转录因子在心脏发生过程中如何在分子调控网络中相互作用，以及这些过程有时如何以及为什么会失败。我们已经确定了一种新的Tbx 5结合蛋白，Lmp 4。我们建议测试的假设，Lmp 4调节Tbx 5转录因子的活性，通过控制其亚细胞定位。本研究的重点是研究Tbx 5/Lmp 4蛋白复合物形成对Tbx 5核定位的作用，Tbx 5依赖的心脏基因表达的变化，心脏模式和形态发生。在细胞水平上，我们将确定Tbx 5转录因子及其结合伴侣的定位，并询问蛋白质水平和亚细胞定位的操作是否会干扰下游基因表达。在生物体水平上，我们将在斑马鱼和鸡胚胎模型中使用互补策略。斑马鱼的功能获得和丧失实验将测试Lmp 4在早期鱼类胚胎发生中的作用，特别强调心脏形成。在鸡心脏中的野生型和突变形式的结合因子的强制错误表达将研究其对心脏特异性基因表达和模式形成的作用。最终，这些研究将提供更广泛的视角Tbx功能，这对于更好地理解与Tbx 5基因突变相关的先天性心血管畸形是必要的，并将深入了解心脏发生中转录因子调控的先前未知机制。

DESCRIPTION (provided by applicant): Congenital heart defects are among the most prevalent and serious diseases affecting humans. Thus, the detrimental impact on the affected individuals, families, and society emphasizes the need for a better understanding of the underlying molecular events at the organ and cell levels. The cardiovascular system is in particular affected by altered T-box gene function. The vertebrate genome contains a family of at least 18 different T-box (Tbx) genes. Among those, Tbx5 has functions in a variety of cardiac lineages and structures, and mutations in human TBX5 result in Holt-Oram syndrome (HOS), a disease characterized by congenital heart and limb defects. The cardiac manifestations in this heart/limb disease range from atrial and ventricular septal defects to complex malformations such as tetralogy of Fallot. The HOS phenotypes can result form either reduced or increased amounts of Tbx5, indicating that the levels of Tbx proteins are critical for normal functioning. In spite of their importance in embryogenesis and disease, the mechanisms by which the encoded transcription factors exert their functions are not yet understood. The long-term objective of this project is to elucidate how the Tbx5 transcription factor interacts within a molecular regulatory network during cardiogenesis, and how and why these processes sometimes fail. We have identified a novel Tbx5 binding protein, Lmp4. We propose testing the hypothesis that Lmp4 regulates Tbx5 transcription factor activity by controlling its subcellular localization. The focus of this study is to investigate the role of Tbx5/Lmp4 protein complex formation on Tbx5 nuclear localization, changes in Tbx5-dependent cardiac gene expression, heart patterning, and morphogenesis. At the cellular level we will determine the localization of Tbx5 transcription factors and their binding partner and ask whether manipulation of protein levels and subcellular localization interferes with downstream gene expression. At the organism level we will use complementary strategies in zebrafish and chicken embryo models. Gain- and loss-of-function experiments in zebrafish will test the role of Lmp4 in early fish embryogenesis with a special emphasis on heart formation. Forced misexpression of wild type and mutated forms of the binding factor in chicken hearts will investigate its role on cardiac-specific gene expression and pattern formation. Ultimately, these studies will provide a broader perspective of Tbx function, necessary for a better understanding of congenital cardiovascular malformations associated with Tbx5 gene mutations, and will provide insight into a previously unknown mechanism for transcription factor regulation in cardiogenesis.