1
|
Goupille O, Kadri Z, Langelé A, Luccantoni S, Badoual C, Leboulch P, Chrétien S. The integrity of the FOG-2 LXCXE pRb-binding motif is required for small intestine homeostasis. Exp Physiol 2019; 104:1074-1089. [PMID: 31012180 DOI: 10.1113/ep087369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 04/16/2019] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Do Fog2Rb- / Rb- mice present a defect of small intestine homeostasis? What is the main finding and its importance? The importance of interactions between FOG-2 and pRb in adipose tissue physiology has previously been demonstrated. Here it is shown that this interaction is also intrinsic to small intestine homeostasis and exerts extrinsic control over mouse metabolism. Thus, this association is involved in maintaining small intestine morphology, and regulating crypt proliferation and lineage differentiation. It therefore affects mouse growth and adaptation to a high-fat diet. ABSTRACT GATA transcription factors and their FOG cofactors play a key role in tissue-specific development and differentiation, from worms to humans. We have shown that GATA-1 and FOG-2 contain an LXCXE pRb-binding motif. Interactions between retinoblastoma protein (pRb) and GATA-1 are crucial for erythroid proliferation and differentiation, whereas the LXCXE pRb-binding site of FOG-2 is involved in adipogenesis. Fog2-knock-in mice have defective pRb binding and are resistant to obesity, due to efficient white-into-brown fat conversion. Our aim was to investigate the pathophysiological impact of FOG-2-pRb interaction on the small intestine and mouse growth. Histological analysis of the small intestine revealed architectural changes in Fog2Rb- / Rb- mice, including villus shortening, with crypt expansion and a change in muscularis propria thickness. These differences were more marked in the proximo-distal part of the small intestine and were associated with an increase in crypt cell proliferation and disruption of the goblet and Paneth cell lineage. The small intestine of the mutants was unable to adapt to a high-fat diet, and had significantly lower plasma lipid levels on such a diet. Fog2Rb- / Rb- mice displayed higher levels of glucose-dependent insulinotropic peptide release, and lower levels of insulin-like growth factor I release on a regular diet. Their intestinal lipid absorption was impaired, resulting in restricted weight gain. In addition to the intrinsic effects of the mutation on adipose tissue, we show here an extrinsic relationship between the intestine and the effect of FOG-2 mutation on mouse metabolism. In conclusion, the interaction of FOG-2 with pRb coordinates the crypt-villus axis and controls small intestine homeostasis.
Collapse
Affiliation(s)
- Olivier Goupille
- Division of Innovative Therapies, UMR E007, Institute of Biology François Jacob, CEA, Université Paris Sud, Université Paris-Saclay, Fontenay aux Roses, France
| | - Zahra Kadri
- Division of Innovative Therapies, UMR E007, Institute of Biology François Jacob, CEA, Université Paris Sud, Université Paris-Saclay, Fontenay aux Roses, France
| | - Amandine Langelé
- Division of Innovative Therapies, UMR E007, Institute of Biology François Jacob, CEA, Université Paris Sud, Université Paris-Saclay, Fontenay aux Roses, France
| | - Sophie Luccantoni
- Immunology of Viral Infections and Autoimmune Diseases, IDMIT Department, Institute of Biology François Jacob, CEA - Université Paris Sud 11 - INSERM U1184, Fontenay-aux-Roses, France
| | - Cécile Badoual
- Department of Pathology, G. Pompidou European Hospital APHP - Université Paris, Descartes, Paris, France
| | - Philippe Leboulch
- Division of Innovative Therapies, UMR E007, Institute of Biology François Jacob, CEA, Université Paris Sud, Université Paris-Saclay, Fontenay aux Roses, France.,Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.,Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Stany Chrétien
- Division of Innovative Therapies, UMR E007, Institute of Biology François Jacob, CEA, Université Paris Sud, Université Paris-Saclay, Fontenay aux Roses, France.,INSERM, Paris, France
| |
Collapse
|
2
|
Abstract
The SV40 viral oncogene has been used since the 1970s as a reliable and reproducible method to generate transgenic mouse models. This seminal discovery has taught us an immense amount about how tumorigenesis occurs, and its success has led to the evolution of many mouse models of cancer. Despite the development of more modern and targeted approaches for developing genetically engineered mouse models of cancer, SV40-induced mouse models still remain frequently used today. This review discusses a number of cancer types in which SV40 mouse models of cancer have been developed and highlights their relevance and importance to preclinical research.
Collapse
Affiliation(s)
- Amanda L Hudson
- Amanda L. Hudson, PhD, is a Sydney Neuro-Oncology Group postdoctoral fellow at the Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, Northern Sydney Local Health District, Sydney Medical School Northern, University of Sydney, St. Leonards, NSW, Australia. Emily K. Colvin is a Cancer Institute NSW postdoctoral fellow at the Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, Northern Sydney Local Health District, Sydney Medical School Northern, University of Sydney, St. Leonards, NSW, Australia
| | - Emily K Colvin
- Amanda L. Hudson, PhD, is a Sydney Neuro-Oncology Group postdoctoral fellow at the Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, Northern Sydney Local Health District, Sydney Medical School Northern, University of Sydney, St. Leonards, NSW, Australia. Emily K. Colvin is a Cancer Institute NSW postdoctoral fellow at the Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, Northern Sydney Local Health District, Sydney Medical School Northern, University of Sydney, St. Leonards, NSW, Australia
| |
Collapse
|
3
|
Gustafsson Sheppard N, Jarl L, Mahadessian D, Strittmatter L, Schmidt A, Madhusudan N, Tegnér J, Lundberg EK, Asplund A, Jain M, Nilsson R. The folate-coupled enzyme MTHFD2 is a nuclear protein and promotes cell proliferation. Sci Rep 2015; 5:15029. [PMID: 26461067 PMCID: PMC4602236 DOI: 10.1038/srep15029] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 09/11/2015] [Indexed: 12/16/2022] Open
Abstract
Folate metabolism is central to cell proliferation and a target of commonly used cancer chemotherapeutics. In particular, the mitochondrial folate-coupled metabolism is thought to be important for proliferating cancer cells. The enzyme MTHFD2 in this pathway is highly expressed in human tumors and broadly required for survival of cancer cells. Although the enzymatic activity of the MTHFD2 protein is well understood, little is known about its larger role in cancer cell biology. We here report that MTHFD2 is co-expressed with two distinct gene sets, representing amino acid metabolism and cell proliferation, respectively. Consistent with a role for MTHFD2 in cell proliferation, MTHFD2 expression was repressed in cells rendered quiescent by deprivation of growth signals (serum) and rapidly re-induced by serum stimulation. Overexpression of MTHFD2 alone was sufficient to promote cell proliferation independent of its dehydrogenase activity, even during growth restriction. In addition to its known mitochondrial localization, we found MTHFD2 to have a nuclear localization and co-localize with DNA replication sites. These findings suggest a previously unknown role for MTHFD2 in cancer cell proliferation, adding to its known function in mitochondrial folate metabolism.
Collapse
Affiliation(s)
- Nina Gustafsson Sheppard
- Unit of Computational Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.,Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden.,Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
| | - Lisa Jarl
- Unit of Computational Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.,Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Diana Mahadessian
- Science for Life Laboratory, Royal Institute of Technology, Solna, Sweden
| | - Laura Strittmatter
- Department of Molecular Biology and the Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Angelika Schmidt
- Unit of Computational Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.,Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Nikhil Madhusudan
- Department of Molecular Biology and the Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Jesper Tegnér
- Unit of Computational Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.,Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Emma K Lundberg
- Science for Life Laboratory, Royal Institute of Technology, Solna, Sweden
| | - Anna Asplund
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Mohit Jain
- Department of Medicine, Institute for Metabolomics Medicine, University of California, San Diego, USA
| | - Roland Nilsson
- Unit of Computational Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.,Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| |
Collapse
|
4
|
Sáenz Robles MT, Chong JL, Koivisto C, Trimboli A, Liu H, Leone G, Pipas JM. Viral oncogene expression in the stem/progenitor cell compartment of the mouse intestine induces adenomatous polyps. Mol Cancer Res 2014; 12:1355-64. [PMID: 24994749 DOI: 10.1158/1541-7786.mcr-14-0166] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
UNLABELLED Genetic and epigenetic events that alter gene expression and/or protein function or localization are thought to be the primary mechanism that drives tumorigenesis and governs the clinical behavior of cancers. Yet, a number of studies have shown that the effects of oncogene expression or tumor suppressor ablation are highly dependent on cell type. The molecular basis for this cell-type specificity and how it contributes to tumorigenesis are unknown. Here, expression of a truncated SV40 large T antigen in murine intestinal crypts promoted the formation of numerous adenomatous polyps in the colon and small intestine. In contrast, when the same T-antigen construct is expressed in villous enterocytes, the consequences are limited to hyperplasia and dysplasia. The T-antigen-induced polyps show high levels of the proto-oncogene c-Myc protein even though there is no transport of β-catenin to the nucleus. Targeting the expression of viral oncogenes to intestinal crypts or villi provides a murine model system for studying cell-type specific effects in tumorigenesis, and is particularly relevant to the study of APC/β-catenin-independent pathways contributing to the generation of intestinal polyps. IMPLICATIONS This mouse model system describes the formation of colon polyps in the absence of Wnt/β-catenin signaling.
Collapse
Affiliation(s)
| | - Jean Leon Chong
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - Christopher Koivisto
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - Anthony Trimboli
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - Huayang Liu
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - Gustavo Leone
- Department of Human Genetics and Cancer Center, Ohio State University, Columbus, Ohio
| | - James M Pipas
- Department of Biological Sciences, University of Pittsburgh. Pittsburgh, Pennsylvania.
| |
Collapse
|
5
|
An P, Sáenz Robles MT, Pipas JM. Large T antigens of polyomaviruses: amazing molecular machines. Annu Rev Microbiol 2013; 66:213-36. [PMID: 22994493 DOI: 10.1146/annurev-micro-092611-150154] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The large tumor antigen (T antigen) encoded by simian virus 40 is an amazing molecular machine because it orchestrates viral infection by modulating multiple fundamental viral and cellular processes. T antigen is required for viral DNA replication, transcription, and virion assembly. In addition, T antigen targets multiple cellular pathways, including those that regulate cell proliferation, cell death, and the inflammatory response. Ectopic T antigen expression results in the immortalization and transformation of many cell types in culture and T antigen induces neoplasia when expressed in rodents. The analysis of the mechanisms by which T antigen carries out its many functions has proved to be a powerful way of gaining insights into cell biology. The accelerating pace at which new polyomaviruses are being discovered provides a collection of novel T antigens that, like simian virus 40, can be used to discover and study key cellular regulatory systems.
Collapse
Affiliation(s)
- Ping An
- Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260, USA
| | | | | |
Collapse
|
6
|
Rathi AV, Cantalupo PG, Sarkar SN, Pipas JM. Induction of interferon-stimulated genes by Simian virus 40 T antigens. Virology 2010; 406:202-11. [PMID: 20692676 PMCID: PMC2939315 DOI: 10.1016/j.virol.2010.07.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 06/22/2010] [Accepted: 07/09/2010] [Indexed: 12/24/2022]
Abstract
Simian virus 40 (SV40) large T antigen (TAg) is a multifunctional oncoprotein essential for productive viral infection and for cellular transformation. We have used microarray analysis to examine the global changes in cellular gene expression induced by wild-type T antigen (TAg(wt)) and TAg-mutants in mouse embryo fibroblasts (MEFs). The expression profile of approximately 800 cellular genes was altered by TAg(wt) and a truncated TAg (TAg(N136)), including many genes that influence cell cycle, DNA-replication, transcription, chromatin structure and DNA repair. Unexpectedly, we found a significant number of immune response genes upregulated by TAg(wt) including many interferon-stimulated genes (ISGs) such as ISG56, OAS, Rsad2, Ifi27 and Mx1. Additionally, we also observed activation of STAT1 by TAg(wt). Our genetic studies using several TAg-mutants reveal an unexplored function of TAg and indicate that the LXCXE motif and p53 binding are required for the upregulation of ISGs.
Collapse
Affiliation(s)
- Abhilasha V. Rathi
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Paul G. Cantalupo
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Saumendra N. Sarkar
- University of Pittsburgh Cancer Institute, Hillman Cancer Research Pavilion, 5117 Centre Avenue, Pittsburgh, PA 15213
| | - James M. Pipas
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| |
Collapse
|
7
|
Abstract
Over 50 years of polyomavirus research has produced a wealth of insights into not only general biologic processes in mammalian cells, but also, how conditions can be altered and signaling systems tweaked to produce transformation phenotypes. In the past few years three new members (KIV, WUV, and MCV) have joined two previously known (JCV and BKV) human polyomaviruses. In this review, we present updated information on general virologic features of these polyomaviruses in their natural host, concentrating on the association of MCV with human Merkel cell carcinoma. We further present a discussion on advances made in SV40 as the prototypic model, which has and will continue to inform our understanding about viruses and cancer.
Collapse
Affiliation(s)
- Ole Gjoerup
- Cancer Virology Program, Hillman Cancer Research Pavilion, University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA
| | | |
Collapse
|
8
|
Cheng J, DeCaprio JA, Fluck MM, Schaffhausen BS. Cellular transformation by Simian Virus 40 and Murine Polyoma Virus T antigens. Semin Cancer Biol 2009; 19:218-28. [PMID: 19505649 PMCID: PMC2694755 DOI: 10.1016/j.semcancer.2009.03.002] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Revised: 03/19/2009] [Accepted: 03/20/2009] [Indexed: 01/09/2023]
Abstract
Simian Virus 40 (SV40) and Mouse Polyoma Virus (PY) are small DNA tumor viruses that have been used extensively to study cellular transformation. The SV40 early region encodes three tumor antigens, large T (LT), small T (ST) and 17KT that contribute to cellular transformation. While PY also encodes LT and ST, the unique middle T (MT) generates most of the transforming activity. SV40 LT mediated transformation requires binding to the tumor suppressor proteins Rb and p53 in the nucleus and ST binding to the protein phosphatase PP2A in the cytoplasm. SV40 LT also binds to several additional cellular proteins including p300, CBP, Cul7, IRS1, Bub1, Nbs1 and Fbxw7 that contribute to viral transformation. PY MT transformation is dependent on binding to PP2A and the Src family protein tyrosine kinases (PTK) and assembly of a signaling complex on cell membranes that leads to transformation in a manner similar to Her2/neu. Phosphorylation of MT tyrosine residues activates key signaling molecules including Shc/Grb2, PI3K and PLCgamma1. The unique contributions of SV40 LT and ST and PY MT to cellular transformation have provided significant insights into our understanding of tumor suppressors, oncogenes and the process of oncogenesis.
Collapse
Affiliation(s)
- Jingwei Cheng
- Department of Medical Oncology, Dana-Farber Cancer Institute; Department of Medicine, Brigham and Women’s Hospital; and Harvard Medical School, Boston, MA 02115
| | - James A. DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute; Department of Medicine, Brigham and Women’s Hospital; and Harvard Medical School, Boston, MA 02115
- Center for Applied Cancer Science, Dana-Farber Cancer Institute, Boston, MA 02115
| | - Michele M. Fluck
- Department of Microbiology and Molecular Genetics, Interdepartmental Program in Cell and Molecular Biology, Michigan State University, East Lansing, MI 48824
| | | |
Collapse
|
9
|
Simian virus 40 T-antigen-mediated gene regulation in enterocytes is controlled primarily by the Rb-E2F pathway. J Virol 2009; 83:9521-31. [PMID: 19570859 DOI: 10.1128/jvi.00583-09] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Simian virus 40 large T antigen (TAg) contributes to cell transformation, in part, by targeting two well-characterized tumor suppressors, pRb and p53. TAg expression affects the transcriptional circuits controlled by Rb and by p53. We have performed a microarray analysis to examine the global change in gene expression induced by wild-type TAg (TAg(wt)) and TAg mutants, in an effort to link changes in gene expression to specific transforming functions. For this analysis we have used enterocytes from the mouse small intestine expressing TAg. Expression of TAg(wt) in the mouse intestine results in hyperplasia and dysplasia. Our analysis indicates that practically all gene expression regulated by TAg in enterocytes is dependent upon its binding and inactivation of the Rb family proteins. To further dissect the role of the Rb family in the induction of intestinal hyperplasia, we have screened several lines of transgenic mice expressing a truncated TAg (TAg(N136)), which is able to interfere with the Rb pathway but lacks the functions associated with the carboxy terminus of the protein. This analysis confirmed the pivotal association between the Rb pathway and the induction of intestinal hyperplasia and revealed that upregulation of p53 target genes is not associated with the tumorigenic phenotype. Furthermore, we found that TAg(N136) was sufficient to induce intestinal hyperplasia, although the appearance of dysplasia was significantly delayed.
Collapse
|
10
|
Sáenz Robles MT, Pipas JM. T antigen transgenic mouse models. Semin Cancer Biol 2009; 19:229-35. [PMID: 19505650 DOI: 10.1016/j.semcancer.2009.02.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 02/03/2009] [Accepted: 02/06/2009] [Indexed: 01/12/2023]
Abstract
The study of polyomavirus has benefited immensely from two scientific methodologies, cell culture and in vitro studies on one side and the use of transgenic mice as experimental models on the other. Both approaches allowed us to identify cellular products targeted by the viruses, the consequences of these interactions at the phenotypic and molecular level, and thus the potential roles of the targets within their normal cellular context. In particular, cell culture and in vitro reports suggest a model explaining partially how SV40 large T antigen contributes to oncogenic transformation. In most cases, T antigen induces cell cycle entry by inactivation of the Rb proteins (pRb, p130, and p107), thus activating E2F-dependent transcription and subsequent S-phase entry. Simultaneously, T antigen blocks p53 activity and therefore prevents the ensuing cell-cycle arrest and apoptosis. For the most part, studies of T antigen expression in transgenic mice support this model, but the use of T antigen mutants and their expression in different tissue and cell type settings have expanded our knowledge of the model system and raised important questions regarding tumorigenic mechanisms functioning in vivo.
Collapse
|
11
|
Pipas JM. SV40: Cell transformation and tumorigenesis. Virology 2008; 384:294-303. [PMID: 19070883 DOI: 10.1016/j.virol.2008.11.024] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Accepted: 11/18/2008] [Indexed: 10/21/2022]
Abstract
The story of SV40-induced tumorigenesis and cellular transformation is intimately entwined with the development of modern molecular biology. Because SV40 and other viruses have small genomes and are relatively easy to manipulate in the laboratory, they offered tractable systems for molecular analysis. Thus, many of the early efforts to understand how eukaryotes replicate their DNA, regulate expression of their genes, and translate mRNA were focused on viral systems. The discovery that SV40 induces tumors in certain laboratory animals and transforms many types of cultured cells offered the first opportunity to explore the molecular basis for cancer. The goal of this article is to highlight some of the experiments that have led to our current view of SV40-induced transformation and to provide some context as to how they contributed to basic research in molecular biology and to our understanding of cancer.
Collapse
Affiliation(s)
- James M Pipas
- Department of Biological Sciences, University of Pittsburgh, PA 15260, USA.
| |
Collapse
|
12
|
Guo J, Longshore S, Nair R, Warner BW. Retinoblastoma protein (pRb), but not p107 or p130, is required for maintenance of enterocyte quiescence and differentiation in small intestine. J Biol Chem 2008; 284:134-140. [PMID: 18981186 DOI: 10.1074/jbc.m806133200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The function of retinoblastoma protein (pRb) in the regulation of small intestine epithelial cell homeostasis has been challenged by several groups using various promoter-based Cre transgenic mouse lines. Interestingly, different pRb deletion systems yield dramatically disparate small intestinal phenotypes. These findings confound the function of pRb in this dynamic tissue. In this study, Villin-Cre transgenic mice were crossed with Rb (flox/flox) mice to conditionally delete pRb protein in small intestine enterocytes. We discovered a novel hyperplasia phenotype as well as ectopic cell cycle reentry within villus enterocytes in the small intestine. This phenotype was not seen in other pRb family member (p107 or p130) null mice. Using a newly developed crypt/villus isolation method, we uncovered that expression of pRb was undetectable, whereas proliferating cell nuclear antigen, p107, cyclin E, cyclin D3, Cdk2, and Cdc2 were dramatically increased in pRb-deficient villus cells. Cyclin A, cyclin D1, cyclin D2, and Cdk4/6 expression was not affected by absent pRb expression. pRb-deficient villus cells appeared capable of progressing to mitosis but with higher rates of apoptosis. However, the cycling villus enterocytes were not completely differentiated as gauged by significant reduction of intestinal fatty acid-binding protein expression. In summary, pRb, but not p107 or p130, is required for maintaining the postmitotic villus cell in quiescence, governing the expression of cell cycle regulatory proteins, and completing of absorptive enterocyte differentiation in the small intestine.
Collapse
Affiliation(s)
- Jun Guo
- Division of Pediatric Surgery, Washington University School of Medicine, St. Louis Children's Hospital, St. Louis, Missouri 63110
| | - Shannon Longshore
- Division of Pediatric Surgery, Washington University School of Medicine, St. Louis Children's Hospital, St. Louis, Missouri 63110
| | - Rajalakshmi Nair
- Division of Pediatric Surgery, Washington University School of Medicine, St. Louis Children's Hospital, St. Louis, Missouri 63110
| | - Brad W Warner
- Division of Pediatric Surgery, Washington University School of Medicine, St. Louis Children's Hospital, St. Louis, Missouri 63110.
| |
Collapse
|