Rb-Id2 Pathway in Mouse Development and Tumorigenesis

描述（由申请人提供）：在哺乳动物细胞中，视网膜母细胞瘤（Rb）肿瘤抑制蛋白对于执行终末细胞周期退出、完全分化和确保细胞存活至关重要。在缺乏Rb的情况下，小鼠发育受损，Rb突变胚胎在妊娠中期死亡，红细胞生成和神经发生严重缺陷。螺旋-环螺旋蛋白分化抑制剂2（Id 2）协调增殖和分化。Id 2结合Rb并拮抗其抗增殖功能。我们最近报道了小鼠Id 2基因的消融挽救了Rb突变胚胎的表型异常和致死性。这些结果已经确定了Id 2作为肿瘤抑制蛋白的相关靶点，其功能在发育过程中必须受到Rb的抑制。这项工作的长期目标是利用转基因小鼠模型了解Rb-Id 2复合物在增殖、分化和肿瘤发生中的作用。我们已经发现，Rb是必不可少的分化的巨噬细胞/树突状细胞谱系，细胞类型所需的支持在胎儿肝脏中的红细胞生成。这是一个令人兴奋的新发现，将使我们能够解剖最相关的Rb-空缺陷，以追踪红细胞生成中由Rb-Id 2途径指导的分子事件。我们还将通过在不存在Rb的情况下区分Id 2和E2 F功能来确定Id 2在细胞增殖和分化中的靶特异性。最后，为了确定Id 2在Rb失活引发的肿瘤发生中的作用，我们将使用Rb突变易患垂体癌的小鼠模型。这些实验将增加我们对Rb促进正常细胞的细胞周期停滞和分化的机制以及这些机制在细胞转化中的扰动的理解。

DESCRIPTION (provided by applicant): In mammalian cells, the Retinoblastoma (Rb) tumor suppressor protein is essential to execute terminal cell cycle withdrawal, complete differentiation and secure cell survival. In the absence of Rb, mouse development is impaired and Rb-mutant embryos die at mid-gestation with severe defects in erythropoiesis and neurogenesis. The helix-loop helix protein Inhibitor of differentiation 2 (Id2) coordinates proliferation and differentiation. Id2 binds Rb and antagonizes its antiproliferative function. We have recently reported that ablation of the mouse Id2 gene rescues the phenotypic abnormalities and lethality of Rb-mutant embryos. These results have identified Id2 as a relevant target of tumor suppressor proteins, whose function must be restrained by Rb during development. The long-term goal of this work is to understand the role of Rb-Id2 complexes in proliferation, differentiation and tumorigenesis using genetically modified mouse models. We have found that Rb is essential for differentiation of the macrophage/dendritic cell lineage, a cell type required to support erythropoiesis in the fetal liver. This is an exciting novel finding that will allow us to dissect the most relevant Rb-null defect, in order to trace the molecular events directed by the Rb-Id2 pathway in erythropoiesis. We will also determine the target specificity of Id2 in cell proliferation and differentiation by discriminating Id2 and E2F functions in the absence of Rb. Finally, to establish the role of Id2 in tumorigenesis initiated by inactivation of Rb, we will use a mouse model in which mutation of Rb predisposes to pituitary cancer. These experiments will increase our understanding of the mechanisms by which Rb promotes cell cycle arrest and differentiation in normal cells and the perturbation of these mechanisms in cellular transformation.