MECHANISMS OF CARDIAC PATHOGENESIS IN NOONAN SYNDROME

PTPN 11的突变导致努南综合征。组件4将探索PTPN 11在瓣膜形成中的作用的机制基础。目的是机械解剖努南综合征的心脏自主病理。我们的近期目标是在不同的心脏细胞群中，利用酪氨酸磷酸酶SHP-2的正常和突变形式的诱导性心脏特异性表达进行全面的研究。这些研究将通过PTPN 11的可诱导的心脏特异性基因消融来补充，以辨别不同发育时间的蛋白质功能。特异性目的1将探索SHP-2表达的心肌细胞自主作用，以剖析对肥大和瓣膜功能障碍的主要和次要作用。野生型（WT）和突变的蛋白质将通过转基因仅在心肌细胞群体中表达。前提是 努南突变SHP-29（Gln 79 Arg）的表达将导致心肌细胞肥大。SPECIFIC AIM 2将在相关的非心肌细胞群体中进行补充研究，以确定SHP-2突变在心脏垫形成和流出道发育过程中的作用。WT和突变的蛋白质在发育过程中仅在内皮细胞群中表达。SPECIFIC AIM 3将通过使用我们部门开发的MerCreMer系统进行艺术诱导的心肌细胞特异性敲除来探索正常蛋白质功能的丧失。我们假设SHP-2的作用 功能的丧失将根据发育时间而根本不同，并且以这种方式可以探索SHP-2在控制心脏中正常细胞过程中的作用。SPECIFIC AIM 4将探索心肌细胞中SHP-2下游的信号通路。我们假设SHP-2通过激活心肌细胞中的MAP激酶（MAPK）通路来进行信号传导，并且SHP-2的消融将减弱MAPK信号传导，而WT-SHP-2或SHP-2（Gln 79 Arg）的过表达将导致响应于各种刺激的通过ERK分支的MAPK活性增加或不适当的MAPK活性。

Mutations in PTPN11 cause Noonan syndrome. Component 4 will explore the mechanistic underpinnings of PTPN11's role in valve formation. The objective is to mechanistically dissect the cardiac-autonomous pathologies of Noonan syndrome. Our immediate goals are to carry out comprehensive studies using inducible, cardiac-specific expression of both the normal and mutated forms of the tyrosine phosphatase, SHP-2 in the different cardiac cell populations. These studies will be complemented by an inducible, cardiac-specific gene ablation of PTPN11 in order to discern protein function at different developmental times. SPECIFIC AIM 1 will explore the cardiomyocyte autonomous effects of SHP-2 expression in order to dissect the primary and secondary effects on hypertrophy and valve dysfunction. Wild type (WT) and mutated protein will be expressed only in the cardiomyocyte population via transgenesis. The hypothesis is that expression of the Noonan mutation SHP-29(Gln79Arg), will result in cardiomyocyte hypertrophy. SPECIFIC AIM 2 will carry out the complementary studies in the relevant non-cardiomyocyte populations to define the role that the SHP-2 mutation plays during cardiac cushion formation and development of the outflow tract. Both the WT and mutated protein will be expressed during development in the endothelial population only. SPECIFIC AIM 3 will explore loss of function of the normal protein by carrying out art inducible, cardiomyocyte-specific knockout using the MerCreMer system developed in our Division. We hypothesize that the effects of SHP-2 loss of function will differ radically depending upon the developmental time and in this manner the role of SHP-2 in controlling normal cellular processes in the heart can be explored. SPECIFIC AIM 4 will explore the signaling pathways downstream of SHP-2 in cardiomyocytes. We hypothesize that SHP-2 signals through activation of the MAP kinase (MAPK) pathway in cardiomyocytes and that ablation of SHP-2 will blunt MAPK signaling while over-expression of WT-SHP-2 or SHP-2(Gln79Arg) will result in increased MAPK activity or inappropriate MAPK activity through the ERK branch in response to various stimuli.