Cux-1 and Cell Cycle Regulation in Kidney Development

描述（由申请人提供）：本提案的总体目的是确定Cux-1是否是Notch信号通路的下游效应物。Cux-1是果蝇基因Cut的鼠同源物。哺乳动物切割蛋白在许多不同组织中作为细胞周期依赖性转录抑制因子发挥作用。Cux-1抑制细胞周期蛋白激酶抑制剂p21在S期的表达，并且是控制G1-S转变的网络的一部分。Cux-1还抑制CKI p27，并且Cux-1在转基因小鼠中的异位表达导致来自p27表达的异常下调的多器官增生。虽然对Cux-1调控的靶点了解很多，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物发挥作用。初步研究表明，Cux-1在表达组成型活性Notch受体的大鼠肾上皮细胞中上调，这与p27表达降低有关。此外，免疫沉淀试验揭示了Cux-1和groucho同源物TLE-4之间的相互作用，TLE-4是一种与Notch信号传导的已知效应物相互作用的共阻遏物。最后，最近的研究揭示了肾脏发育过程中Cux-1和Notch通路组分之间的表达模式惊人的相似性。这些结果表明，Cux-1作为Notch信号通路的效应子发挥作用。拟议的研究将测试的假设，即调控Cux-1的Notch信号通路是保守的哺乳动物发育过程中，Cux-1与TLE蛋白相互作用，以调节p27基因的表达。具体目标是：1.确定Cux-1表达是否需要Notch信号传导。2.评价TLE蛋白和Cux-1之间的相互作用。3.明确Cux-1和Notch 2在体内肾脏发育中的关系。4.明确足细胞发育和肾发生过程中Cux-1、TLE-4和Notch信号之间的关系。这些研究将为发育过程中细胞增殖的机制提供新的见解。

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.