The Role of HNF4alpha in Cell Proliferation

描述（由申请人提供）：肝细胞核因子（HNF） 41是胎儿和成人肝脏形态和功能所需的重要核受体，调节许多肝脏特异性基因，涉及各种代谢过程、血液稳态和上皮结构。这种高度保守的核受体在n端和C端具有不同的同种异构体。它们是通过使用两个可选启动子和3'剪接事件产生的。有证据表明，这些剪接变体在肝脏发育中起着不同的作用。P1亚型（HNF411/12）仅在胚胎后期、出生后和成人肝脏中表达，而P2亚型（HNF417/18）仅在胎儿肝脏中表达。这些同种异构体如何调节细胞从增殖到分化的转变还有待阐明。最近，我们发现HNF411上调细胞周期蛋白依赖性激酶抑制剂p21（一种细胞周期抑制剂）；我们还发现癌蛋白c-Myc可以消除这种活性。其他研究表明HNF41与TCF/LEF相互作用，TCF/LEF是Wnt/2-catenin通路的下游。该通路的功能障碍与肝脏和其他癌症有关。我们的目标是破译HNF41在细胞周期调节中的作用，并研究不同的HNF41亚型在这一过程中的作用。我们将在我们的研究中结合分子和高通量技术，如共免疫沉淀（co-IP）、细胞增殖试验、表达谱阵列和染色质免疫沉淀测序（ChIP-Seq）技术。我们将使用永生化的癌细胞系和小鼠胚胎干细胞（mES）细胞，我们将把它们分化成肝细胞系。胚胎干细胞可以无限增殖，就像癌细胞一样，但它们也可以分化成任何特殊的细胞类型。简而言之，它们模仿正常的发育。另一方面，癌细胞系提供了一个系统来检查破坏微妙的增殖-分化平衡的病理后果。这两个系统将提供互补的方法来解决肝脏发育和疾病中细胞增殖和细胞分化之间的基本二分法。

DESCRIPTION (provided by applicant): Hepatocyte nuclear factor (HNF) 41, an important nuclear receptor required for the morphology and function of the fetal and adult livers, regulates many liver-specific genes involved in various metabolic processes, blood homeostasis, and epithelium architecture. This highly conserved nuclear receptor has various isoforms that differ in the N-terminal and C- terminal domains. These are generated by the use of two alternative promoters and 3' splicing events. There has been evidence suggesting that these splice variants play different roles in liver development. The P1 isoforms (HNF411/12) are expressed exclusively in lat embryo, postnatal and adult livers while the P2 isoforms (HNF417/18) are expressed only in the fetal liver. How these isoforms regulate the transition from proliferating to differentiating cells is yet to be elucidated. Recently, we have shown that HNF411 upregulates cyclin dependent kinase inhibitor p21, a cell cycle inhibitor; we have also shown that the oncoprotein c-Myc abolishes this activity. Others have shown HNF41 interacts with TCF/LEF which is the downstream of the Wnt/2-catenin pathway. Dysfunction in this pathway is associated with liver and other cancers. Our goal is to decipher the role of HNF41 in cell cycle regulation and to investigate the role of the different HNF41 isoforms in that process. We will incorporate molecular and high throughput technology such as co-immunoprecipitiation (co-IP), cell proliferation assays, expression profiling arrays, and chromatin immunoprecipitation sequencing (ChIP-Seq) techniques in our study. We will use both immortalized cancer cell lines and mouse embryonic stem (mES) cells that we will differentiate into the hepatic lineage. ES cells can proliferate indefinitely, just like cancer cells, but they also can differentiate into any specialized cell type. In short, they mimic normal development. Cancer cell lines, on the other hand, provide a system to examine the pathological consequences of disrupting the delicate proliferation-differentiation balance. These two systems will provide complementary approaches to address the fundamental dichotomy between cell proliferation and cell differentiation in liver development and disease. PUBLIC HEALTH RELEVANCE: The liver, which is the primary site for metabolism, detoxification and homeostasis, is an important and major organ that contributes to the well being of the body. Malfunction of the liver attributes to various severe human diseases such as diabetes, atherosclerosis, and cancer. Important as the liver is in the human adult, improper formation of the liver in the fetus can also lead to complications and eventually death. Thus, our investigation as to how the liver is formed from early cells to more specialized cells will help us understand the battle between cell proliferation and cell differentiation that can lead to the formation and progression of liver cancer as well as the development of other various forms of diseases.