1991 — 1993 |
Taub, Rebecca A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Expression of Igfbp-1 in Liver Regeneration @ University of Pennsylvania
The liver is an epithelioid organ that can regenerate following partial hepatectomy, toxic damage or liver transplant. As such, it provides one of the few systems for analysis of mitogenesis in the fully developed, intact animal. Although it is comprised mainly of hepatocytes, the liver has a complex, multi-cellular architecture, implying that intercellular communications must exist during regeneration. Whereas multiple factors have been implicated, the growth factors involved in this process remain unknown. We have shown that one of the most highly expressed, immediate-early genes in liver regeneration encodes the rat homolog of the low molecular weight IGF binding protein (IGFBP-1). This protein has been found to enhance the mitogenic effect of IGF on tissues, and may act in a paracrine and/or autocrine fashion in maintaining normal liver architecture during regeneration. The goals of the research outlined in this proposal are first to determine the functional role of IGFBP-1 in hepatic development and regeneration, and second to analyze the regulation of expression of this gene during liver regeneration. These goals will be accomplished by completing the following specific aims: 1. Direct assessment of the mitogenic effects of IGFBP-1 and IGF-1 on hepatocyte and nonparenchymal liver cells in culture. 2. Further characterization of IGFBP-1 expression during liver development and regeneration by detection of IGFBP-1 and other IGFBPS, and by in situ detection of IGFBP-1 mRNA. 3. Examination of the transcriptional regulation of expression of the IGFBP-1 gene in insulin-treated H35 cells and in liver regeneration. 4. Genetic assessment of the role of IGFBP-1 in hepatic regeneration and development following underexpression of IGFBP-1 by gene "knock out", and overexpression of IGFBP-1 in transgenic mice.
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0.958 |
1995 — 2002 |
Taub, Rebecca A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Function of a Growth Induced Gene in Liver Regeneration @ University of Pennsylvania
The liver constitutes one of the few, normally-quiescent tissues in the adult body that has the capacity to regenerate. As a result, it provides a unique, multi-cellular, physiologically normal system in which to study the mitogenic response of epithelial cells. Previously, we identified more than 40 novel immediate-early and delayed-early genes activated during liver regeneration. Immediate-early or primary response genes many of which encode proto-oncogenes have been shown to have important effects on cell growth and differentiation. Of the genes we identified, PRL-1 is particularly interesting, because it is the only gene that is induced at a high level in regenerating liver, but is constitutively expressed in insulin-treated rat H35 hepatoma cells which otherwise show normal regulation of immediate-early genes. It is a liver-enriched immediate- early gene because its induction is much higher in the regenerating liver than in other mitogen activated cells. We reasoned that PRL-1 could have important effects on growth of hepatic cells. Initial studies revealed that PRL-1 encodes a unique protein tyrosine phosphatase (PTPase) with no homology to other PTPases outside the active site. In cells, PRL-1 migrates as a 21 kD protein, and is located primarily in the triton- insoluble fraction of the cell nucleus. Stably transfected cells which overexpress PRL-1 demonstrate altered cellular growth and morphology, and a transformed phenotype. Other PTPases have been shown to have important effects on cellular growth control. PTPases such as cdc25 and MKP-1 have very specific intracellular substrates, cdc-2, Map kinase, respectively, thus establishing their importance in cell growth control. Thus far, Dr. Taub's laboratory has not identified specific intracellular targets for the PRL-1 phosphatase. However, like other PTPases, PRL-1 may be important in normal cellular growth in liver regeneration and other cells in which it is expressed, and could contribute to the tumorigenicity of hepatomas and other cancer cells. We have two major goals in this proposal. We will demonstrate the importance of PRL-1 in hepatic and cell growth by more carefully defining its expression patterns in animals, and modulating its expression in the 3T3 and H35 (liver) cell lines and animals. We will learn more about the specifics of PRL-1 function by characterizing interacting proteins, and identifying specific intracellular substrates. Ultimately these two goals will merge and allow us to define precisely how PRL-1 functions to regulate hepatic growth during development and regeneration, and contributes to oncogenesis in liver tumors. We will accomplish these goals by (1) more precisely defining the expression of PRL-1 in liver regeneration, fetal and adult tissues; (2) testing the specific effects of PRL-1 on cell growth and oncogenesis by carefully regulating PRL-1 expression in transfected 3T3 and H35 cells and liver cells of transgenic animals; (3) identifying the cellular substrates of PRL-1 by characterizing PRL-1 associated proteins, expression cloning and testing candidate substrates; and (4) characterizing potential members of the PRL-1 gene family through homology cloning.
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0.958 |
1996 — 2000 |
Taub, Rebecca A |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Core--Molecular Biology Core @ University of Pennsylvania
histogenesis; mammalian embryology; biomedical facility; oligonucleotides; genetically modified animals; laboratory mouse; nucleic acid chemical synthesis; nucleic acid sequence; computer assisted sequence analysis;
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0.958 |
1996 — 2000 |
Taub, Rebecca A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Molecular Control of Liver Regeneration @ University of Pennsylvania
DESCRIPTION: Liver regeneration following partial hepatectomy provides one of the few examples of a physiologic growth response occurring in the intact animal. This application is directed to understanding the basic molecular mechanisms that: 1) trigger regeneration, and 2) allow the liver to concurrently grow and maintain differentiated function. Specific aim 1: Among the earliest responses observed in the regenerating liver are the activation of PHF/NF-Kappa B and Stat3, transcription factors that are normally induced by cytokines such as TNF alpha and IL-6. The PI is examining the importance of PHF/NF-Kappa B by analyzing the regenerative capacity of mouse livers from animals that are genetically missing the p50 subunit of PHF/NF-Kappa B. Similarly, she is assessing the impact of Stat3 by analyzing IL-6 negative animals that do not induce Stat3 after partial hepatectomy. Preliminary studies indicate that regeneration is abnormal in IL-6-/- animals. She will also assess the impact of C/EBP beta deficiency on liver regeneration. It is shown that there is a relative increase in C/EBP beta to alpha levels during regeneration which may be important for progression through the cell cycle and maintenance of the liver phenotype during regeneration. In this way, she will be able to determine the subset of immediate-early genes that are specific targets of PHF/NF-Kappa B, Stat 3, and C/EBP beta. By measuring the impact of these mutations on the regenerative capacity, and assessing the potential interplay between the PHF/NF-Kappa B, Stat3, and C/EBP beta pathways, the PI will determine the role of specific cytokine/growth factor pathways in triggering liver regeneration. Specific aim 2: To identify additional "liver regeneration factors", she will determine what promoter elements are responsible for induction of the liver-enriched immediate-early gene PRL-1 during liver regeneration. PRL-1 immediate-early and late expression is normal in the knockout mice examined so far. These studies will allow the definition of novel factors and pathways that control regeneration. Specific aim 3: As proteins encoded by some immediate-early and delayed-early genes are the ultimate regulators of liver regeneration, she will trace the transcriptional cascade that ultimately leads to liver cell growth. She will study the regulation of specific target genes of IL-6/Stat3, NF-Kappa B and C/EBP beta. They have already identified a specific subset of immediate-early genes including AP1 factors (jun, fos, LRF-1) and c-myc that are expressed at abnormally low levels in IL-6-/- mice. She will study their regulation in more detail and assess the role of Stat3 in their regulation. During regeneration, the liver must maintain vital functions including metabolic homeostasis despite the acute loss of two thirds of its mass. This is accomplished as a result of the induction of liver-specific immediate-early genes such as glucose-6 phosphatase (G6Pase) and PEPCK. The G6Pase gene is not induced appropriately in p50/NF-Kappa B1 -/-mice. She hypothesizes that this is because G6Pase mRNA is normally regulated by synergistic interactions between PHF/NF-Kappa B and endogenous constitutive factors such as C/EBP which continue to be expressed during liver regeneration. In addition to animal studies, she will design studies to test this hypothesis by examining direct effects and the interplay of C/EBPs and NF-Kappa B on the G6Pase gene in cell culture systems in which the local environment can be carefully regulated.
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0.958 |
1997 — 2001 |
Taub, Rebecca A |
P30Activity Code Description: To support shared resources and facilities for categorical research by a number of investigators from different disciplines who provide a multidisciplinary approach to a joint research effort or from the same discipline who focus on a common research problem. The core grant is integrated with the center's component projects or program projects, though funded independently from them. This support, by providing more accessible resources, is expected to assure a greater productivity than from the separate projects and program projects. |
Core--Molecular Biology Facility @ University of Pennsylvania
digestive disorder; molecular biology; liver disorder; biomedical facility; molecular pathology; information dissemination; human genetic material tag; molecular cloning; imaging /visualization /scanning; genetic library; nucleic acid sequence;
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0.958 |
2000 — 2002 |
Taub, Rebecca A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
The Interplay Between Hepatic Growth and Metabolism @ University of Pennsylvania
DESCRIPTION: (Adapted from the applicant's abstract) The specific focus of this project is on genes that play a role in both growth and metabolism in the liver, with a major emphasis on insulin-like growth factor binding protein-1 (IGFBP-1). Expression of IGFBP-1 is highly upregulated during liver growth in regeneration and development. Its expression is also upregulated during fasting and downregulated by high insulin levels. IGFBP-1 can cause upregulation of glucose levels with a proposed mechanism based on its inhibition of serum IGF function. In preliminary studies, the applicant demonstrates that increased transcription of the IGFBP-1 gene during liver regeneration is mediated in part by interleukin-6 (IL-6) a critical cytokine in the regenerative response. Aim 1 will examine whether IL-6 activation of IGFBP-1 transcription is mediated through STAT-3 co-activation of HNF-1 transcription of the IGFBP-1 promoter and identify the mechanism by which IL-6 blocks insulin-mediated repression of IGFBP-1 promoter expression. Experiments are also proposed to identify the mechanism by which IL-6 upregulation of AP-1 activity mediates increased IGFBP-1 gene expression. IGFBP-1 null or knockout mice have been created and they display defects in glucose regulation and abnormal liver regeneration and repair. Aim 2 will examine the ability of IGFBP-1 null livers to regenerate and repair and explore mechanistic defects after partial hepatectomy, acute and chronic carbon tetrachloride (CCl4) mediated liver injury and FAS mediated liver injury. The applicant will assess basic parameters of glucose metabolism in IGFBP-1 null mice and determine the basis for any abnormalities.
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0.958 |