Role of Gab2 and Shp2 in Hematopoietic Signalling

描述（由申请人提供）：造血是由生长因子和细胞因子调节的，其中许多通过蛋白酪氨酸激酶（PTKs）发出信号。异常PTKs导致骨髓增生性疾病（MPD）和/或白血病；例如，编码融合ptk的白血病相关易位（例如Bcr/Abl， Tel-Jak2），或ptk中的点突变，例如在许多成人mpd中发现的Jak2中的V617F突变。蛋白酪氨酸磷酸酶（PTPs）也调节酪氨酸磷酸化。它们的作用还不太清楚，直到最近，PTP突变还没有在MPD/白血病中被发现。本研究的长期目标是了解含有sh2的PTP Shp2 （PTPn11）及其结合蛋白Gab2在正常造血和疾病中的功能。早期的研究表明，细胞因子诱发的Ras/Erk通路激活需要Shp2。最近，在人类疾病中发现了类似于我们之前产生的“激活突变体”的Shp2突变。种系Shp2突变导致努南综合征（NS），这是一种常染色体显性遗传病，以发育缺陷和MPD风险增加为特征，尤其是青少年髓细胞白血病（JMML）。体细胞Shp2突变见于JMML和其他白血病。没有Shp2突变的JMML病例有激活Ras或Nf1突变功能丧失，这与Shp2在调节Ras中的作用一致，但疾病相关的Shp2突变的生化和生物学后果尚不清楚。在目前的资助期内，我们建立了NS和JMML的小鼠模型并对其进行了表征。我们的研究结果表明，白血病相关的Shp2突变体是通过增强il - 3/GMCSF信号导致MPD的强超突变体，而NS等位基因是较弱的超突变体。然而，与遗传修饰因子和/或合作等位基因相反，Shp2突变的内在特性在多大程度上决定疾病表型仍不清楚。致白血病Shp2作用的靶细胞尚不清楚，致白血病Shp2突变体增强IL3/GMCSF信号的确切机制尚不清楚。在初步研究中，我们开发了一种新的，独特的“敲入”模型，用于白血病突变体D61Y和其他疾病相关的Shp2敲入突变等位基因系列。我们将使用这些模型来描述在内源性启动子控制下表达的白血病和NS突变体对造血和造血细胞信号传导的影响，以确定shp2诱发MPD的靶细胞，并评估疾病基因、修饰位点和次要事件对MPD发展的相对贡献。最近的数据表明，致白血病的Shp2突变体通过增强Jak2激活而起作用，这表明儿童和成人MPD之间存在共享的分子途径。我们还将确定Jak2过度激活的机制和后果，并测试Shp2突变是否也可能在成人MPD中发挥作用。

DESCRIPTION (provided by applicant): Hematopoiesis is regulated by growth factors and cytokines, many of which signal via protein- tyrosine kinases (PTKs). Abnormal PTKs cause myeloproliferative disorders (MPD) and/or leukemia; e.g., leukemia-associated translocations that encode fusion-PTKs (e.g. Bcr/Abl, Tel-Jak2), or point mutations in PTKs, such as the V617F mutation in Jak2 found in many adult MPDs. Protein-tyrosine phosphatases (PTPs) also regulate tyrosyl phosphorylation. Their roles are less well understood, and until recently, PTP mutations had not been identified in MPD/leukemia. The long range goal of this research is to understand the function of the SH2-containing PTP Shp2 (PTPn11) and its binding protein, Gab2, in normal hematopoiesis and disease. Earlier work established that Shp2 in required for cytokine-evoked Ras/Erk pathway activation. More recently, mutations in Shp2, similar to "activated mutants" we generated earlier, were identified in human disease. Germ-line Shp2 mutations cause Noonan syndrome, (NS) an autosomal dominant disorder featuring developmental defects and increased risk of MPD, especially juvenile myelomonocytic leukemia (JMML). Somatic Shp2 mutations are found in JMML and other leukemias. JMML cases without Shp2 mutation have activated Ras or loss-of-function Nf1 mutations, consistent with Shp2's role in regulating Ras, but the biochemical and biological consequences of disease-associated Shp2 mutations was unclear. During the current funding period, we generated and characterized mouse models for NS and JMML. Our results suggested that leukemia-associated Shp2 mutants are strong hypermorphs that cause MPD by enhancing IL3/GMCSF signaling, whereas NS alleles are weaker hypermorphs. However, the extent to which the intrinsic properties of an Shp2 mutation determine disease phenotype, as opposed to genetic modifiers and/or cooperating alleles remains unclear. The target cell in which leukemogenic Shp2 acts remains unidentified, and the precise mechanism by which leukemogenic Shp2 mutants enhance IL3/GMCSF signaling remains unknown. In Preliminary Studies, we have developed a new, unique "knock-in" model for the leukemogenic mutant D61Y and an allelic series of other disease- associated Shp2 knock-in mutants. We will use these models to delineate the effect of leukemogenic and NS mutants, expressed under endogenous promoter control, on hematopoiesis and hematopoietic cell signaling, to identify the target cell(s) for Shp2-evoked MPD, and to assess the relative contribution of disease gene, modifier loci, and secondary events to MPD development. Very recent data indicate that leukemogenic Shp2 mutants act by enhancing Jak2 activation, suggesting a shared molecular pathway between childhood and adult MPD. We also will determine the mechanisms and consequences of Jak2 hyperactivation, and test whether Shp2 mutations may also play a role in adult MPD.