A novel G protein signaling pathway controlling Drosophila cardiac morphogenesis

描述（申请人提供）：心脏形成的早期形态发生机制在进化上是保守的。为了鉴定新的致心基因，我们在果蝇中进行了大规模的基因筛选。我们发现了一种独特的心脏缺陷，称为心碎（bro），心包细胞和心脏母细胞分离，导致心脏功能丧失和胚胎死亡。这种表型是由于编码甲基戊酸途径中HMG-CoA还原酶及其下游酶的基因突变，以及G蛋白G31的基因突变，该基因是香叶酰香叶酰化的，因此代表了类异戊二烯生物合成的终点。确定C在心脏形态发生中的重要作用，为发现心脏形态发生所需的整个G蛋白遗传途径打开了大门。在这里，我们将研究G31的功能机制，并确定与G31形成心脏异三聚体G蛋白复合物的G1和G2伙伴。从我们的筛选中，我们还鉴定了两个参与这一过程的g蛋白偶联受体（gpcr）。我们将利用我们在初步研究中建立的心脏细胞类型特异性救援系统来研究这些gpcr的作用。我们的筛选还发现了两个兄弟突变破坏编码间隔连接成分的基因，表明间隔连接的形成参与心脏形态发生。我们将利用电子显微镜表征果蝇心脏的细胞-细胞连接，并研究分离连接蛋白在心脏发育过程中的作用。我们还将研究G蛋白信号突变如何影响心脏中分离连接的形成。这些研究将填补心脏发育研究领域的重大空白，促进我们对先天性心脏病分子机制的认识。

DESCRIPTION (provided by applicant): The early morphogenetic mechanisms involved in heart formation are evolutionarily conserved. To identify novel cardiogenic genes, we performed a large-scale genetic screen in Drosophila. We discovered a unique cardiac defect, called broken hearted (bro), in which pericardial cells and cardioblasts dissociate, causing loss of cardiac function and embryonic lethality. This phenotype resulted from mutations in genes encoding HMG-CoA reductase and its downstream enzymes in the mevalonate pathway, as well as G protein G31, which is geranylgeranylated, thus representing an end point of isoprenoid biosynthesis. Identification of the essential role of C in cardiac morphogenesis opened a door to discovery of the entire G protein genetic pathway required for cardiac morphogenesis. Here, we will investigate the functional mechanism of G31, and identify the G1 and G2 partners that form the cardiac heterotrimeric G protein complex with G31. From our screen, we also identified two G-protein coupled receptors (GPCRs) involved in this process. We will investigate the roles of these GPCRs using cardiac cell type specific rescue system established in our preliminary studies. Our screen also identified two bro mutations disrupting genes encoding septate junction components, indicating that septate junction formation is involved in cardiac morphogenesis. We will characterize the cell-cell junctions of Drosophila heart using electron microscopy and study the role of septate junction proteins during heart development. We will also examine how the G protein signaling mutants affect septate junction formation in the heart. These studies will fill a significant gap in the research field of heart development, and promote our understanding of the molecular mechanism of congenital heart disease. Narrative: Heart development is controlled by evolutionarily conserved genetic network. To identify genes in this network, we performed a large-scale genetic screen in Drosophila and identified a group of highly conserved genes required for heart formation. Studies of these genes promote our understanding of heart development and mechanism of congenital heart disease.