MECHANISMS OF CARDIAC PATHOGENESIS IN NOONAN SYNDROME

PTPN11基因突变会导致努南综合征。第四部分将探讨PTPN11‘S在瓣膜形成中作用的机制基础。其目的是从机械上剖析Noonan综合征的心脏自主病理。我们的近期目标是在不同的心肌细胞群中，利用可诱导的、心脏特有的正常和突变形式的酪氨酸磷酸酶SHP-2的表达来进行全面的研究。这些研究将辅以可诱导的、心脏特异的PTPN11基因消融，以区分不同发育时期的蛋白质功能。目的探讨SHP-2的表达对心肌细胞的自主作用，以探讨SHP-2在心肌肥厚和瓣膜功能障碍中的原发和继发作用。野生型(WT)和突变蛋白将通过转基因仅在心肌细胞群中表达。假设是这样的 Noonan突变SHP-29(Gln79Arg)的表达，会导致心肌细胞肥大。特异性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突变在心垫形成和流出道发育过程中所起的作用。WT和突变蛋白都将在发育过程中仅在内皮细胞群体中表达。特定的AIM 3将通过使用我们部门开发的MerCreMer系统进行ART诱导的、心肌细胞特异性的敲除来探索正常蛋白质功能的丧失。我们假设SHP-2的影响 根据发育时间的不同，功能的丧失将从根本上不同，通过这种方式，可以探索SHP-2在控制心脏正常细胞过程中的作用。特异的AIM4将探索心肌细胞中SHP-2下游的信号通路。我们假设SHP-2信号是通过激活心肌细胞中的MAPK通路来实现的，SHP-2的消融将钝化MAPK信号，而WT-SHP-2或SHP-2(Gln79Arg)的过度表达将导致MAPK活性增加或通过ERK分支不适当的MAPK活性来响应各种刺激。

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.