Animal Models of Polycythemia Vera

本研究项目的长期目标是确定真性红细胞增多症（PV）的分子基础。 PV通过其对定向造血祖细胞的作用代表突变激酶JAK 2 V617 F的最终表型，但我们假设，虽然JAK 2 V617 F表达是PV临床表型的原因，但导致该疾病的潜在分子机制存在于细胞内。 在某些实施方案中，本发明涉及不需要JAK 2的造血干细胞（HSC），并且血小板生成素（TPO）受体Mpl整体地参与这些机制。这一假设是基于我们发现PV中Mpl表达受损，血浆TPO随之增加，以及我们观察到PV中Mpl表达缺失， MPL基因在JAK 2 V617 F转基因小鼠PV模型中消除了PV表型，为在干细胞水平上理解PV的病理生理学和合理的治疗方法提供了机制基础。为此，我们建议使用遗传技术来剖析MPL基因对PV表型的影响。 MPL：TPO轴，以及人PV CD 34+细胞中上调的特定基因对PV鼠JAK 2 V617 F tg模型中HSC行为的作用。在具体目标1中，我们将检查TPO基因的废除对JAK 2 V617 F tg小鼠的表型、其HSC库的大小和HSC的表型的影响。 基因表达谱，通过与TPO-/-小鼠交配。对照实验将采用Mpl功能被点突变或不依赖于MPL的基因敲除而废除的小鼠，所述点突变或基因敲除损害血小板产生，而中和Mpl抗血清将作为靶向治疗的模型进行检查。在特定 目的2，我们将创建表达PV Mpl剪接变体的tg小鼠，并在存在和不存在JAK 2 V617 F的情况下评估其表型。我们还研究了通过杂交，敲除JAK 2 V617 F tg小鼠表型上的JAK 2或LCN 2（PV中上调的两个基因）的影响。 最后，在特定目标3中，我们将在NOG小鼠中使用异种移植来检查来自临床上不同PV患者群体的遗传学定义的PV CD 34+细胞的体内行为，这些PV患者群体是我们通过基因表达谱和非监督分层聚类确定的。

The long-temri objective of this research project is to define the molecular basis of polycythemia vera (PV). PV represents the ultimate phenotype of the mutant kinase, JAK2 V617F, through its effects on committed hematopoietic progenitor cells but we hypothesize that while JAK2 V617F expression is responsible for the clinical phenotype of PV, the underlying molecular mechanisms responsible for the disease reside in the hematopoietic stem cell (HSC), which does not require JAK2, and that the thrombopoietin (TPO) receptor, Mpl, is integrally Involved In these mechanisms. This hypothesis, which is based on our discovery of impaired Mpl expression in PV with an attendant increase in plasma TPO, and our observation that absence of the MPL gene abrogated the PV phenotype in a JAK2 V617F transgenic (tg) mouse model of PV, provides a mechanistic basis for understanding the pathophysiology of PV at the stem cell level and a rational approach to therapy To this end, we propose to use genetic techniques to dissect the influence of the MPL:TPO axis, and also the roles of specific genes up regulated in human PV CD34+ cells, on the behavior of HSC in the murine JAK2 V617F tg model of PV. In Specific Aim 1, we will examine the effect of abrogation of the TPO gene on the phenotype of the JAK2 V617F tg mouse, on the size of its HSC pool and the HSC gene expression profile, by breeding with a TPO-/- mouse. Control experiments will employ mice in which Mpl function was abrogated by a point mutation or a gene knockout independent of MPL that impairs platelet production, while a neutralizing Mpl antiserum will be examined as a model of targeted therapy. In Specific Aim 2, we will create a tg mouse expressing a PV Mpl splice variant and assess its phenotype in the presence and absence of JAK2 V617F. We also examine by crossbreeding, the effect of knocking out SPARC or LCN2, two genes that are up regulated in PV, on the phenotype of the JAK2 V617F tg mouse. Finally, in Specific Aim 3, we will use xenotranslantation in NOG mice to examine the in vivo behavior of genetically-defined PV CD34 + cells from clinically distinct PV patient populations that we have identified by gene expression profiling and unsuoervised hierarchical clustering.