Cux-1 and Cell Cycle Regulation in Kidney Development

描述(申请人提供)：该提案的总体目标是确定Cux-1是否是Notch信号通路的下游效应者。Cux-1是果蝇基因Cut的小鼠同源物。哺乳动物的切割蛋白在许多不同的组织中作为细胞周期依赖的转录抑制因子发挥作用。CuX-1抑制细胞周期蛋白激酶抑制因子p21在S期的表达，是控制细胞周期由G1向S转变的网络的一部分。Cux-1还抑制CKI p27的表达，在转基因小鼠中异位表达的Cux-1通过异常下调p27的表达而导致多器官增生。虽然关于Cux-1调控的靶点已经了解很多，但对Cux-1的上游调控因子知之甚少。在果蝇中，Cut作为Notch信号通路的下游效应器发挥作用。初步研究表明，Cux-1在表达固有活性的Notch受体的大鼠肾上皮细胞中上调，这与p27的表达减少有关。此外，免疫沉淀分析显示Cux-1和Groucho同源物TLE-4之间存在相互作用，TLE-4是一种共抑制物，与已知的Notch信号效应器相互作用。最后，最近的研究表明，Cux-1和Notch途径组分在肾脏发育过程中的表达模式有惊人的相似性。这些结果表明，Cux-1是Notch信号通路的效应者。这些研究将验证一种假设，即通过Notch信号通路对Cux-1的调节在哺乳动物发育过程中是保守的，并且Cux-1与TLE蛋白相互作用来调节p27基因的表达。其具体目的是：1.确定Cux-1的表达是否需要Notch信号。2.研究TLE蛋白与Cux-1的相互作用。3.明确Cux-1和Notch2在体内肾脏发育中的关系。4.明确Cux-1、TLE-4和Notch信号在足细胞发育和肾脏发生中的关系。这些研究将为细胞在发育过程中的增殖机制提供新的见解。

DESCRIPTION (provided by applicant): The overall aim of this proposal is to determine whether Cux-1 is a downstream effector of the Notch signaling pathway. Cux-1 is the murine homologue of the Drosophila gene Cut. Mammalian Cut proteins function as cell cycle-dependent transcriptional repressors in many different tissues. Cux-1 represses the expression of the cyclin kinase inhibitor p21 in S phase and is part of the network controlling G1-S transition. Cux-1 also represses the CKI p27, and ectopic expression of Cux-1 in transgenic mice results in multiorgan hyperplasia from the aberrant down regulation of p27 expression. While much has been learned about the targets of Cux-1 regulation, little is known about the upstream regulators of Cux-1. In Drosophila, Cut functions as a downstream effector of the Notch signaling pathway. Preliminary studies show that Cux-1 is upregulated in rat kidney epithelial cells expressing a constitutively active Notch receptor, and this is associated with decreased expression of p27. In addition, immunoprecipitation assays reveal an interaction between Cux-1 and the groucho homologue TLE-4, a co-repressor that interacts with known effectors of Notch signaling. Finally, recent studies reveal a striking similarity in expression pattern between Cux-1 and Notch pathway components during kidney development. These results suggest that Cux-1 functions as an effector of the Notch signaling pathway. The proposed studies will test the hypothesis that regulation of Cux-1 by the Notch signaling pathway is conserved during mammalian development and that Cux-1 interacts with TLE proteins to regulate p27 gene expression. The specific aims are: 1. Determine whether Notch signaling is required for Cux-1 expression. 2. Evaluate the interaction between TLE proteins and Cux-1. 3. Define the relationship between Cux-1 and Notch2 in kidney development in vivo. 4. Define the relationship between Cux-1, TLE-4, and Notch signaling during podocyte development and nephrogenesis. These studies will provide novel insights into the mechanisms of cell proliferation during development.