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Zheng JB, Qiao LN, Sun XJ, Qi J, Ren HL, Wei GB, Zhou PH, Yao JF, Zhang L, Jia PB. Overexpression of caudal-related homeobox transcription factor 2 inhibits the growth of transplanted colorectal tumors in nude mice. Mol Med Rep 2015; 12:3409-3415. [PMID: 26005051 PMCID: PMC4526061 DOI: 10.3892/mmr.2015.3838] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 04/15/2015] [Indexed: 12/13/2022] Open
Abstract
Caudal-related homeobox transcription factor 2 (CDX2) is a transcription factor, which is specifically expressed in the adult intestine. It is essential for the development and homeostasis of the intestinal epithelium and its functions as a tumor suppressor have been demonstrated in the adult colon. The present study aimed to examine the inhibitory effects of the overexpression of CDX2 on subcutaneously-transplanted tumors, derived from LoVo colon cancer cells, in nude mice, and to provide experimental evidence for the biotherapy of colon cancer. A pEGFP-C1-CDX2 eukaryotic expression vector was transfected into the LoVo cells via lipofection, and LoVo cells stably-expressing CDX2 (pEGFP-C1-CDX2 cells) were obtained using G418 selection. A nude mouse subcutaneously-transplanted tumor model was established by inoculating the nude mice with the pEGFP-C1-CDX2 cells, and the effects of overexpression of CDX2 on transplanted tumor growth in the LoVo cells were observed. Western blotting results demonstrated that the protein expression of CDX2 in the LoVo cells was higher in the pEGFP-C1-CDX2 cell group, compared with that in the pEGFP-C1 cell group and the untreated cell group. At 20 days post-inoculation with either pEGFP-C1-CDX2 or pEGFP-C1, the transplanted tumor masses were significantly lower in the pEGFP-C1-CDX2 group, compared with those in the pEGFP-C1 and untreated groups. Immunohistochemistry revealed that the expression levels of CDX2 and matrix metalloproteinase-2 (MMP-2) were detected in each group, and the protein expression of CDX2 was increased in the tumor tissues from the nude mice in the pEGFP-C1-CDX2 group. However the expression of MMP-2 was downregulated in the tumor tissues of the nude mice in the pEGFP-C1-CDX2 group. Taken together, these data suggested that pEGFP-C1-CDX2 cells exhibited suppressed tumor growth in vivo. Overexpression of CDX2 was observed in transplanted tumors in the pEGFP-C1-CDX2 group, and the gene expression of MMP-2 was reduced. These results indicate that CDX2 inhibited the growth of colorectal tumor cells, possibly by downregulating the gene expression.
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Affiliation(s)
- Jian-Bao Zheng
- Department of General Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Li-Na Qiao
- Department of General Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Xue-Jun Sun
- Department of General Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Jie Qi
- Second Department of Cardiovascular Medicine, Shaanxi Provincial People's Hospital, Xi'an, Shaanxi 710068, P.R. China
| | - Hai-Liang Ren
- Department of General Surgery, The Third Hospital of Chengdu, Chengdu, Sichuan 610031, P.R. China
| | - Guang-Bing Wei
- Department of General Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Pei-Hua Zhou
- Department of General Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Jian-Feng Yao
- Department of General Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Li Zhang
- Department of General Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Peng-Bo Jia
- Department of General Surgery, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
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Witek ME, Snook AE, Lin JE, Blomain ES, Xiang B, Magee M, Waldman SA. A novel CDX2 isoform regulates alternative splicing. PLoS One 2014; 9:e104293. [PMID: 25101906 PMCID: PMC4125279 DOI: 10.1371/journal.pone.0104293] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 07/11/2014] [Indexed: 12/27/2022] Open
Abstract
Gene expression is a dynamic and coordinated process coupling transcription with pre-mRNA processing. This regulation enables tissue-specific transcription factors to induce expression of specific transcripts that are subsequently amplified by alternative splicing allowing for increased proteome complexity and functional diversity. The intestine-specific transcription factor CDX2 regulates development and maintenance of the intestinal epithelium by inducing expression of genes characteristic of the mature enterocyte phenotype. Here, sequence analysis of CDX2 mRNA from colonic mucosa-derived tissues revealed an alternatively spliced transcript (CDX2/AS) that encodes a protein with a truncated homeodomain and a novel carboxy-terminal domain enriched in serine and arginine residues (RS domain). CDX2 and CDX2/AS exhibited distinct nuclear expression patterns with minimal areas of co-localization. CDX2/AS did not activate the CDX2-dependent promoter of guanylyl cyclase C nor inhibit transcriptional activity of CDX2. Unlike CDX2, CDX2/AS co-localized with the putative splicing factors ASF/SF2 and SC35. CDX2/AS altered splicing patterns of CD44v5 and Tra2-β1 minigenes in Lovo colon cancer cells independent of CDX2 expression. These data demonstrate unique dual functions of the CDX2 gene enabling it to regulate gene expression through both transcription (CDX2) and pre-mRNA processing (CDX2/AS).
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Affiliation(s)
- Matthew E. Witek
- Department of Radiation Oncology, Kimmel Cancer Center & Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Adam E. Snook
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Jieru E. Lin
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Erik S. Blomain
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Bo Xiang
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Michael Magee
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Scott A. Waldman
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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Roeseler DA, Sachdev S, Buckley DM, Joshi T, Wu DK, Xu D, Hannink M, Waters ST. Elongation factor 1 alpha1 and genes associated with Usher syndromes are downstream targets of GBX2. PLoS One 2012; 7:e47366. [PMID: 23144817 PMCID: PMC3493575 DOI: 10.1371/journal.pone.0047366] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 09/12/2012] [Indexed: 11/18/2022] Open
Abstract
Gbx2 encodes a DNA-binding transcription factor that plays pivotal roles during embryogenesis. Gain-and loss-of-function studies in several vertebrate species have demonstrated a requirement for Gbx2 in development of the anterior hindbrain, spinal cord, inner ear, heart, and neural crest cells. However, the target genes through which GBX2 exerts its effects remain obscure. Using chromatin immunoprecipitation coupled with direct sequencing (ChIP-Seq) analysis in a human prostate cancer cell line, we identified cis-regulatory elements bound by GBX2 to provide insight into its direct downstream targets. The analysis revealed more than 286 highly significant candidate target genes, falling into various functional groups, of which 51% are expressed in the nervous system. Several of the top candidate genes include EEF1A1, ROBO1, PLXNA4, SLIT3, NRP1, and NOTCH2, as well as genes associated with the Usher syndrome, PCDH15 and USH2A, and are plausible candidates contributing to the developmental defects in Gbx2(-/-) mice. We show through gel shift analyses that sequences within the promoter or introns of EEF1A1, ROBO1, PCDH15, USH2A and NOTCH2, are directly bound by GBX2. Consistent with these in vitro results, analyses of Gbx2(-/-) embryos indicate that Gbx2 function is required for migration of Robo1-expressing neural crest cells out of the hindbrain. Furthermore, we show that GBX2 activates transcriptional activity through the promoter of EEF1A1, suggesting that GBX2 could also regulate gene expression indirectly via EEF1A. Taken together, our studies show that GBX2 plays a dynamic role in development and diseases.
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Affiliation(s)
- David A. Roeseler
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States of America
- Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri, United States of America
| | - Shrikesh Sachdev
- Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri, United States of America
- Department of Biochemistry, University of Missouri, Columbia, Missouri, United States of America
| | - Desire M. Buckley
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States of America
- Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri, United States of America
| | - Trupti Joshi
- Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri, United States of America
- Department of Computer Science, University of Missouri, Columbia, Missouri, United States of America
- Informatics Institute, University of Missouri, Columbia, Missouri, United States of America
| | - Doris K. Wu
- Laboratory of Molecular Biology, NIDCD, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Dong Xu
- Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri, United States of America
- Department of Computer Science, University of Missouri, Columbia, Missouri, United States of America
- Informatics Institute, University of Missouri, Columbia, Missouri, United States of America
| | - Mark Hannink
- Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri, United States of America
- Department of Biochemistry, University of Missouri, Columbia, Missouri, United States of America
| | - Samuel T. Waters
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States of America
- Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri, United States of America
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Bhat AA, Sharma A, Pope J, Krishnan M, Washington MK, Singh AB, Dhawan P. Caudal homeobox protein Cdx-2 cooperates with Wnt pathway to regulate claudin-1 expression in colon cancer cells. PLoS One 2012; 7:e37174. [PMID: 22719836 PMCID: PMC3376107 DOI: 10.1371/journal.pone.0037174] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 04/17/2012] [Indexed: 11/18/2022] Open
Abstract
Dysregulation of tight junctions (TJs) is often associated with human diseases including carcinogenesis and recent studies support role of TJ integral proteins in the regulation of Epithelial-to-Mesenchymal Transition (EMT). In this regard, expression of claudin-1, a key constituent of TJs, is highly increased in colon cancer and is causally associated with the tumor growth and progression. However, mechanism/s underlying regulation of claudin-1 expression in intestinal epithelial cells remains poorly understood. In our studies, we have identified putative binding sites for intestinal transcription factors Cdx1, -2 and GATA4 in the 5'-flanking region of the claudin-1 gene. Our further studies using full length and/or deletion mutant constructs in two different human colon cancer cell lines, SW480 and HCT116, showed key role of Cdx1, Cdx2 and GATA4 in the regulation of claudin-1 mRNA expression. However, overexpression of Cdx2 had the most potent effect upon claudin-1 mRNA expression and promoter activity. Also, in colon cancer patient samples, we observed a significant and parallel correlation between claudin-1 and Cdx2 expressions. Chromatin immunoprecipitation (ChIP) assay confirmed the Cdx2 binding with claudin-1 promoter in vivo. Using Cdx2 deletion mutant constructs, we further mapped the Cdx2 C-terminus domain to be important in the regulation of claudin-1 promoter activity. Interestingly, co-expression of activated β-catenin further induced the Cdx2-dependent upregulation of claudin-1 promoter activity while expression of the dominant negative (dn)-TCF-4 abrogated this activation. Taken together, we conclude that homeodomain transcription factors Cdx1, Cdx2 and GATA4 regulate claudin-1 gene expression in human colon cancer cells. Moreover, a functional crosstalk between Wnt-signaling and transcriptional activation related to caudal-related homeobox (Cdx) proteins and GATA-proteins is demonstrated in the regulation of claudin-1 promoter-activation.
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Affiliation(s)
- Ajaz A. Bhat
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Ashok Sharma
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Jillian Pope
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Cancer Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Moorthy Krishnan
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Mary K. Washington
- Department of Pathology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Amar B. Singh
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Punita Dhawan
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Cancer Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
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Effects of Homeodomain Protein CDX2 Expression on the Proliferation and Migration of Lovo Colon Cancer Cells. Pathol Oncol Res 2011; 17:743-51. [DOI: 10.1007/s12253-011-9380-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 02/07/2011] [Indexed: 02/04/2023]
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Abstract
The Cdx (Caudal-type homeobox) group of ParaHox genes (Cdx1, Cdx2 and Cdx4 in the mouse) perform multiple functions in mammalian development. Cdx1 is concerned with axial positional information, and its deletion appears to have no important effect other than a disturbance of axial patterning. In contrast, Cdx2 is required for trophoblast differentiation, axial patterning and extension, as well as for morphological specification (i.e. patterning) of gut endoderm. Cdx4-knockout animals do not present an abnormal phenotype, but, when combined with Cdx2 haploinsufficiency, present a dramatic picture involving abnormal cloacal specification. The latter is probably due in large part to defective paraxial mesodermal development in the caudal region, but may also involve defective endodermal growth. A significant degree of redundancy is apparent between the Cdx genes with respect to caudal extension and possibly also during gut development.
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Direct repression of Sonic Hedgehog expression in the stomach by Cdx2 leads to intestinal transformation. Biochem J 2010; 427:423-34. [PMID: 20199401 DOI: 10.1042/bj20091177] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Shh (Sonic Hedgehog) is a morphogen involved in gastric fundic gland differentiation in the adult. Shh expression is reduced in Helicobacter pylori-associated intestinal metaplastic change of the gastric epithelium and mice that lack Shh show intestinal transformation of the gastric mucosa. Similarly, in the stomach of Cdx2 (caudal-type homeobox 2)-transgenic mice, the gastric mucosa is replaced by intestinal metaplastic mucosa. The aim of the present study was to use Cdx2-transgenic mice to investigate: (i) Shh expression in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach; and (ii) the relationship between Shh and Cdx2. We determined that Shh mRNA levels were dramatically reduced in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach compared with the normal (wild-type) mouse stomach. This was not due to hypermethylation of the Shh promoter, but instead we showed that Cdx2 directly bound to the TATA box region of the Shh promoter. Cdx2 also down-regulated transcription of the Shh gene in the human gastric carcinoma cell lines AGS, MKN45 and MKN74. In conclusion, Cdx2 reduced Shh expression by binding to the unmethylated Shh promoter in the intestinal metaplastic mucosa of Cdx2-transgenic mouse stomach.
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Mutoh H, Hayakawa H, Sakamoto H, Sashikawa M, Sugano K. Transgenic Cdx2 induces endogenous Cdx1 in intestinal metaplasia of Cdx2-transgenic mouse stomach. FEBS J 2009; 276:5821-31. [PMID: 19725873 DOI: 10.1111/j.1742-4658.2009.07263.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Cdx1 and Cdx2, which are transcription factors regulating normal intestinal development, have been studied as potential key molecules in the pathogenesis of the precancerous intestinal metaplasia of the human stomach. However, the regulation of Cdx1 expression in the intestinal metaplasia is poorly understood. Cdx2-expressing gastric mucosa of Cdx2-transgenic mouse stomach was replaced by intestinal metaplastic mucosa. The aim of this study was to investigate the following: (a) Cdx1 expression in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach; and (b) the relationship between Cdx1 and Cdx2. A mouse model of intestinal metaplasia, the Cdx2-transgenic mouse, was used to investigate Cdx1 gene expression by RT-PCR. DNA methylation profile analysis was performed by bisulfite sequencing, and the interaction of Cdx2 with the Cdx1 promoter was examined by chromatin immunoprecipitation assay, electrophoretic mobility shift assay, and luciferase reporter assays. Cdx2 mRNA was expressed in the Cdx2-transgenic mouse stomach. However, endogenous Cdx2 mRNA was not expressed in the intestinal metaplasia of the Cdx2-transgenic mouse stomach. On the other hand, endogenous Cdx1 mRNA and protein were expressed in the intestinal metaplasia of the Cdx2-transgenic mouse stomach. The Cdx1 promoter was unmethylated in the intestinal metaplasia of the Cdx2-transgenic mouse stomach. Chromatin immunoprecipitation assay and electrophoretic mobility shift assay showed that Cdx2 was bound to the Cdx1 promoter region in the intestinal metaplasia and the normal intestine. Cdx2 upregulated and siRNA-Cdx2 downregulated the transcriptional activity of the Cdx1 gene in the human gastric carcinoma cell lines AGS, MKN45, and MKN74. In conclusion, transgenic Cdx2 induced endogenous Cdx1 through the binding of Cdx2 to the unmethylated Cdx1 promoter region in the intestinal metaplasia of the Cdx2-transgenic mouse stomach.
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Affiliation(s)
- Hiroyuki Mutoh
- Department of Medicine, Division of Gastroenterology, Jichi Medical University, Tochigi, Japan.
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Li H, Shuai XW, Xie PY, Li J. Expression of CDX1/2 in patients with Barrett's esophagus and the effects of bile acids on CDX2 expression. Shijie Huaren Xiaohua Zazhi 2009; 17:1738-1744. [DOI: 10.11569/wcjd.v17.i17.1738] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate CDX1 and CDX2 expressions in biopsies obtained from patients with reflux esophagitis and Barrett's esophagus and to study the effects of various bile acids on CDX2 mRNA expression in human esophageal cell line (Eca-109).
METHODS: Endoscopic biopsies were obtained at the distal esophagus in patients and classified according to histology: normal squamous mucosa (n = 5), esophagitis mucosa (n = 7), and Barrett's metaplasia (n = 8). Gene expression of CDX1 and CDX2 were measured using reverse transcription polymerase chain reaction (RT-PCR) or quantitative real-time RT-PCR. CDX2 protein expression was assessed immunohistochemically. Human esophageal cell line (Eca-109) was exposed to cell culture for 1-24 h to 100, 400, 1000 μmol/L deoxycholic acid (DCA), cholicacid (CA), and glycocholicacids (GC). CDX2 mRNA expression was determined by quantitative RT-PCR.
RESULTS: CDX2 mRNA expression was significantly higher in Barrett's epithelium (9.6411 ± 6.6823) and reflux esophagitis (3.9156 ± 3.6700), compared with normal esophagus (P = 0.006, 0.025 respectively). There was no significant difference between Barrett's mucosa and reflux esophagits (P = 0.133). CDX1 mRNA was not detected in all esophageal mucosa. There was no CDX2 protein expression in normal squamous esophagus, and nuclear immunoreactivity was seen in Barrett's epithelium. Perinuclear immunoreactivity for CDX2 was detected in reflux esophagitis. CDX2 mRNA expression was absent before bile acid exposure in all cell lines and increased in a dose- and time-dependent pattern with deoxycholic acid (DCA), cholicacid (CA), and glycocholicacids (GC).
CONCLUSION: CDX2 expression is up-regulated in esphagitis and Barrett's esophagus, suggesting a possible onset role for CDX2 in esophagitis-Barrett's metaplasia sequence. Bile acids can evoke high expression of CDX2 in vitro. Bile acids may play an important role in Barrett's metaplasia by influencing the expression of CDX2.
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Gastrointestinal differentiation marker Cytokeratin 20 is regulated by homeobox gene CDX1. Proc Natl Acad Sci U S A 2009; 106:1936-41. [PMID: 19188603 DOI: 10.1073/pnas.0812904106] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
CDX1 is a transcription factor that plays a key role in intestinal development and differentiation. However, the downstream targets of CDX1 are less well defined than those of its close homologue, CDX2. We report here the identification of downstream targets of CDX1 using microarray gene-expression analysis and other approaches. Keratin 20 (KRT20), a member of the intermediate filament and a well-known marker of intestinal differentiation, was initially identified as one of the genes likely to be directly regulated by CDX1. CDX1 and KRT20 mRNA expression were significantly correlated in a panel of 38 colorectal cancer cell lines. Deletion and mutation analysis of the KRT20 promoter showed that the minimum regulatory region for the control of KRT20 expression by CDX1 is within 246 bp upstream of the KRT20 transcription start site. ChIP analysis confirmed that CDX1 binds to the predicted CDX elements in this region of the KRT20 promoter in vivo. In addition, immunohistochemistry showed expression of CDX1 parallels that of KRT20 in the normal crypt, which further supports their close relationship. In summary, our observations strongly imply that KRT20 is directly regulated by CDX1, and therefore suggest a role for CDX1 in maintaining differentiation in intestinal epithelial cells. Because a key feature of the development of a cancer is an unbalanced program of proliferation and differentiation, dysregulation of CDX1 may be an advantage for the development of a colorectal carcinoma. This could, therefore, explain the relatively frequent down regulation of CDX1 in colorectal carcinomas by hypermethylation.
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Saksena S, Dwivedi A, Singla A, Gill RK, Tyagi S, Borthakur A, Alrefai WA, Ramaswamy K, Dudeja PK. Characterization of the 5'-flanking region and regulation of expression of human anion exchanger SLC26A6. J Cell Biochem 2009; 105:454-66. [PMID: 18655181 DOI: 10.1002/jcb.21842] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
SLC26A6 (putative anion transporter 1, PAT1) has been shown to play an important role in mediating the luminal Cl(-)/OH(-)(HCO(3)(-)) exchange process in the intestine. Very little is known about the molecular mechanisms involved in the transcriptional regulation of intestinal SLC26A6 gene expression in the intestine. Current studies were, therefore, designed to clone and characterize the 5'-regulatory region of the human SLC26A6 gene and determine the mechanisms involved in its regulation. A 1,120 bp (p-964/+156) SLC26A6 promoter fragment cloned upstream to the luciferase reporter gene in pGL2-basic exhibited high promoter activity when transfected in Caco2 cells. Progressive deletions of the 5'-flanking region demonstrated that -214/-44 region of the promoter harbors cis-acting elements important for maximal SLC26A6 promoter activity. Since, diarrhea associated with inflammatory bowel diseases is attributed to increased secretion of pro-inflammatory cytokines, we examined the effects of IFNgamma (30 ng/ml, 24 h) on SLC26A6 function, expression and promoter activity. IFNgamma decreased both SLC26A6 mRNA and function and repressed SLC26A6 promoter activity. Deletion analysis indicated that IFNgamma response element is located between -414/-214 region and sequence analysis of this region revealed the presence of potential Interferon Stimulated Responsive Element (ISRE), a binding site (-318/-300 bp) for interferon regulatory factor-1 transcription factor (IRF-1). Mutations in the potential ISRE site abrogated the inhibitory effects of IFNgamma. These studies provided novel evidence for the involvement of IRF-1 in the regulation of SLC26A6 gene expression by IFNgamma in the human intestine.
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Affiliation(s)
- Seema Saksena
- Department of Medicine, University of Illinois at Chicago, Jesse Brown VA Medical Center, Chicago, Illinois 60612, USA.
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12
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Fukushima A, Aizaki Y, Sakuma K. Short-chain fatty acids induce intestinal transient receptor potential vanilloid type 6 expression in rats and Caco-2 cells. J Nutr 2009; 139:20-5. [PMID: 19056662 DOI: 10.3945/jn.108.096230] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Fructooligosaccharides (FOS) are indigestible oligosaccharides that increase calcium absorption by the colorectum in rats, but the underlying mechanisms remain unclear. We therefore investigated the effects of FOS on expressions of genes involved with calcium absorption in rat colorectal mucosa cells. After feeding a diet containing FOS (100 g/kg diet) to rats for 2 d, we investigated gene transcripts of transient receptor potential vanilloid type 6 (TRPV6), calbindin-D9k, and plasma membrane calcium-ATPase 1b (PMCA1b). The FOS diet increased expression of TRPV6 and calbindin-D9k but did not affect PMCA1b expression. Because FOS could not directly affect gene expression, SCFA formed as fermentation products of FOS were considered as likely intermediates. SCFA (2.0 mmol/L) were thus added to Caco-2 human colonic epithelial cells, resulting in significantly increased mRNA expression of TRPV6. To ascertain the effects of SCFA on mRNA expression, a genomic clone of TRPV6 was isolated. Using luciferase reporter assay, a segment between -71 nucleotides and the translation start site was found to contain a positive responsive element to SCFA. These results suggest that FOS increase calcium absorption by increasing mRNA expression of TRPV6 in rat colorectum, and cell culture analysis indicated that SCFA, as fermentation products of FOS, are involved in the increased mRNA expression of TRPV6. We found for the first time, to our knowledge, that regulation of TRPV6 gene expression by SCFA may be a molecular mechanism involved in the promotion of calcium absorption by FOS in rats.
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Affiliation(s)
- Akiko Fukushima
- Department of Molecular Nutrition, Kagawa Nutrition University, 3-9-21 Chiyoda, Sakado, Saitama 350-0288, Japan
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Gutiérrez-González L, Wright NA. Biology of intestinal metaplasia in 2008: more than a simple phenotypic alteration. Dig Liver Dis 2008; 40:510-22. [PMID: 18400571 DOI: 10.1016/j.dld.2008.02.029] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Accepted: 02/18/2008] [Indexed: 12/11/2022]
Abstract
This review concentrates on one main aspect of cancerization in the oesophagus and stomach: principally, intestinal metaplasia. There are at least two other important pathways that lead to cancer and do not need such a morphological transformation. One is the gastric type of carcinoma on the Lauren classification, which arises directly from the stem cell zone and is the signet ring form of cancer, while the other is spasmolytic polypeptide-expressing metaplasia (SPEM)--spasmolytic polypeptide (TFF2) expressing metaplasia, where the gastric glands become filled with TFF2-expressing cells and may also lead to gastric dysplasia and cancer. The development of intestinal metaplasia is complex. Here, we examine intestinal metaplasia in molecular terms, noting the over-expression of Cdx1, Cdx2, Pdx1, Oct1, TFF3 and the downregulation of Hedgehog signalling; Runx3 is deactivated by epigenetic silencing, and pathways such as Wnt and MARK/ERK are involved. These changes start to explain the principles of the development of intestinal metaplasia and suggest that the regulation of these genes is of importance in the development of gastric cancer.
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Saegusa M, Hashimura M, Kuwata T, Hamano M, Wani Y, Okayasu I. A functional role of Cdx2 in beta-catenin signaling during transdifferentiation in endometrial carcinomas. Carcinogenesis 2007; 28:1885-92. [PMID: 17468517 DOI: 10.1093/carcin/bgm105] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Nuclear beta-catenin is required for changes in morphology from glandular to morular phenotypes of endometrial carcinoma (Em Ca) cells, with activation of p14(ARF)/p53/p21(Waf1) and alteration of p16(INK4A)/pRb pathways. Having demonstrated previously that the homeodomain transcription factor Cdx2 increases markedly during intestinal epithelial cell differentiation, we have examined its effects in beta-catenin signaling during transdifferentiation of Em Ca cells. In clinical cases, Cdx2 immunoreactivity, along with increased mRNA signals, was found to overlap with nuclear accumulation of beta-catenin and p21(Waf1) in morules, demonstrating an inverse correlation with cell proliferation. In cell lines, over-expression of active form beta-catenin resulted in a significant increase in endogenous Cdx2 expression at both mRNA and protein levels. Furthermore, the Cdx2 promoter was activated by T-cell factor 4 (TCF4) -independent activated beta-catenin, as well as Cdx2 itself, through the region from -39 to +9 bp relative to transcription start site. Cells over-expressing exogenous Cdx2 showed high levels of p21(Waf1) expression due to stabilization of the mRNA status, resulting in significant decrease in the proliferation rate, in contrast to the lack of apparent changes in morphology. Moreover, transfected Cdx2 could inhibit beta-catenin/TCF4-mediated transcriptional activation of target genes, including p14(ARF) and cyclin D1, probably through indirect mechanisms. These data suggest that over-expression of Cdx2 mediated by nuclear beta-catenin and Cdx2 itself can cause an inhibition of Em Ca cell proliferation through up-regulation of p21(Waf1) expression, modulating beta-catenin/TCF4-mediated transcription. We therefore conclude that an association between Cdx2 and beta-catenin signaling may participate in induction of transdifferentiation of Em Ca cells.
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Affiliation(s)
- Makoto Saegusa
- Department of Pathology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 228-8555, Japan.
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15
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Shimada T, Koike T, Yamagata M, Yoneda M, Hiraishi H. Regulation of TFF3 expression by homeodomain protein CDX2. ACTA ACUST UNITED AC 2006; 140:81-7. [PMID: 17182120 DOI: 10.1016/j.regpep.2006.11.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2006] [Revised: 11/03/2006] [Accepted: 11/10/2006] [Indexed: 10/23/2022]
Abstract
Although trefoil factor family 3 (TFF3) plays an important role in protecting the intestinal mucosa, the regulatory mechanisms of its expression are not fully understood. Since homeodomain protein CDX2 has been reported to be critically involved in the development and differentiation of intestinal epithelium, we examined whether CDX2 affects the expression of TFF3. The transcription of human TFF3 reporter genes was significantly up-regulated by the transient overexpression of CDX2 in COS-7 cells and AGS gastric cells. Electrophoretic mobility shift assay revealed the presence of at least two CDX-binding sites within the human TFF3 promoter. Deletion analysis showed the relative importance of the proximal CDX-binding site at -63. We also detected the up-regulation of endogenous TFF3 mRNA expression in AGS cells stably transfected with CDX2 expression vectors. These results suggest that CDX2 plays a key role in the expression of TFF3 in the intestine and perhaps in intestinal metaplasia of the stomach.
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Affiliation(s)
- Tadahito Shimada
- Department of Gastroenterology, Dokkyo Medical University, Mibu, Tochigi 321-0293, Japan.
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16
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Expression of Cdx2 is associated with clinicopathologic features and prognosis of gastric carcinoma. Chin J Cancer Res 2006. [DOI: 10.1007/s11670-006-0105-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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17
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Bosse T, van Wering HM, Gielen M, Dowling LN, Fialkovich JJ, Piaseckyj CM, Gonzalez FJ, Akiyama TE, Montgomery RK, Grand RJ, Krasinski SD. Hepatocyte nuclear factor-1alpha is required for expression but dispensable for histone acetylation of the lactase-phlorizin hydrolase gene in vivo. Am J Physiol Gastrointest Liver Physiol 2006; 290:G1016-24. [PMID: 16223943 DOI: 10.1152/ajpgi.00359.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hepatocyte nuclear factor-1alpha (HNF-1alpha) is a modified homeodomain-containing transcription factor that has been implicated in the regulation of intestinal genes. To define the importance and underlying mechanism of HNF-1alpha for the regulation of intestinal gene expression in vivo, we analyzed the expression of the intestinal differentiation markers and putative HNF-1alpha targets lactase-phlorizin hydrolase (LPH) and sucrase-isomaltase (SI) in hnf1alpha null mice. We found that in adult jejunum, LPH mRNA in hnf1alpha(-/-) mice was reduced 95% compared with wild-type controls (P < 0.01, n = 4), whereas SI mRNA was virtually identical to that in wild-type mice. Furthermore, SI mRNA abundance was unchanged in the absence of HNF-1alpha along the length of the adult mouse small intestine as well as in newborn jejunum. We found that HNF-1alpha occupies the promoters of both the LPH and SI genes in vivo. However, in contrast to liver and pancreas, where HNF-1alpha regulates target genes by recruitment of histone acetyl transferase activity to the promoter, the histone acetylation state of the LPH and SI promoters was not affected by the presence or absence of HNF-1alpha. Finally, we showed that a subset of hypothesized intestinal target genes is regulated by HNF-1alpha in vivo and that this regulation occurs in a defined tissue-specific and developmental context. These data indicate that HNF-1alpha is an activator of a subset of intestinal genes and induces these genes through an alternative mechanism in which it is dispensable for chromatin remodeling.
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Affiliation(s)
- Tjalling Bosse
- Department of Medicine, University of Amsterdam, Amsterdam, the Netherlands
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18
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Ericsson A, Kotarsky K, Svensson M, Sigvardsson M, Agace W. Functional characterization of the CCL25 promoter in small intestinal epithelial cells suggests a regulatory role for caudal-related homeobox (Cdx) transcription factors. THE JOURNAL OF IMMUNOLOGY 2006; 176:3642-51. [PMID: 16517733 DOI: 10.4049/jimmunol.176.6.3642] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The chemokine CCL25 is selectively and constitutively expressed in the small intestinal epithelium and plays an important role in mediating lymphocyte recruitment to this site. In this study, we demonstrate that CCL25 expression in murine small intestinal epithelial cells is independent of signaling through the lymphotoxin beta receptor and is not enhanced by inflammatory stimuli, pathways involved in driving the expression of most other chemokines. We define a transcriptional start site in the CCL25 gene and a region -141 to -5 proximal of exon 1 that is required for minimal promoter activity in the small intestinal epithelial cell lines, MODE-K and mICc12. These cell lines expressed far less CCL25 mRNA than freshly isolated small intestinal epithelial cells indicating that they are missing important factors driving CCL25 expression. The CCL25 promoter contained putative binding sites for the intestinal epithelial-associated Caudal-related homeobox (Cdx) transcription factors Cdx-1 and Cdx-2, and small intestinal epithelial cells but not MODE-K and mICc12 cells expressed Cdx-1 and Cdx-2. EMSA analysis demonstrated that Cdx proteins were present in nuclear extracts from freshly isolated small intestinal epithelial cells but not in MODE-K or mICcl2 cells, and bound to putative Cdx sites within the CCL25 promoter. Finally, cotransfection of MODE-K cells with Cdx transcription factors significantly increased CCL25 promoter activity as well as endogenous CCL25 mRNA levels. Together these results demonstrate a unique pattern of regulation for CCL25 and suggest a role for Cdx proteins in regulating CCL25 transcription.
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Affiliation(s)
- Anna Ericsson
- Immunology Section, Stem Cell Center, Biomedical Centre I-13, Lund University, S-22184 Lund, Sweden
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19
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Staloch LJ, Divine JK, Witten JT, Simon TC. C/EBP and Cdx family factors regulate liver fatty acid binding protein transgene expression in the small intestinal epithelium. ACTA ACUST UNITED AC 2005; 1731:168-78. [PMID: 16321657 DOI: 10.1016/j.bbaexp.2005.08.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Revised: 08/09/2005] [Accepted: 08/25/2005] [Indexed: 11/23/2022]
Abstract
A transgene constructed from the rat liver fatty acid binding protein gene (Fabp1) promoter is active in all murine small intestinal crypt and villus epithelial cells. Coincident Cdx and C/EBP transcription factor binding sites were identified spanning Fabp1 nucleotides -90 to -78. CDX-1, CDX-2, C/EBPalpha, and C/EBPbeta activated the Fabp1 transgene in CaCo-2 cells, and mutagenizing the -78 site prevented activation by these factors. CDX but not C/EBP factors bound to the site in vitro, although C/EBP factors competed with CDX factors for transgene activation. The -78 site adjoins an HNF-1 site, and CDX and C/EBP family factors cooperated with HNF-1alpha but not HNF-1beta to activate the transgene. Furthermore, CDX-1, CDX-2, C/EBPalpha, and C/EBPbeta bound to HNF-1alpha and HNF-1beta. The transgene with a mutagenized -78 site was silenced in vivo specifically in small intestinal crypt epithelial cells but remained active in villus cells. These results demonstrate functional interactions between HNF-1, C/EBP, and CDX family factors and suggest that these interactions may contribute to differential transcriptional regulation in the small intestinal crypt and villus compartments.
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Affiliation(s)
- Lora J Staloch
- Department of Pediatrics, Washington University School of Medicine, Campus Box 8208, St. Louis, MO 63110, USA
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20
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Fan Z, Li J, Dong B, Huang X. Expression of Cdx2 and hepatocyte antigen in gastric carcinoma: correlation with histologic type and implications for prognosis. Clin Cancer Res 2005; 11:6162-70. [PMID: 16144916 DOI: 10.1158/1078-0432.ccr-05-0278] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
PURPOSE This study was designed to (a) analyze the correlation between the expression of Cdx2 and Hep and the clinicopathologic features of patients with gastric carcinoma, and (b) determine the value of combined analysis of Cdx2 and Hep expression in distinguishing histologic types and prognoses of gastric carcinomas. EXPERIMENTAL DESIGN The expression of Cdx2 and Hep were studied using immunohistochemistry of paraffin-embedded tumor specimens from 109 patients who underwent D2 resection for gastric adenocarcinoma from 1995 to 1998. RESULTS Nuclear Cdx2 and Hep expression was detected in 36.7% (40 of 109) and 54.1% (59 of 109) of gastric carcinoma cases, respectively. Expression of Cdx2 and Hep was significantly higher in intestinal-type carcinomas than in diffuse-type carcinomas (P = 0.027 and P = 0.037, respectively). There was a clear negative correlation between Cdx2 expression and lymph node metastasis (P = 0.029), as well as between Hep expression and depth of wall invasion (P = 0.011). The patients with Cdx2-positive or Hep-positive expression shows higher survival rate than those with Cdx2-negative or Hep-negative expression (P = 0.0008 and P = 0.003, respectively). Multivariate analysis revealed that the expression of Cdx2 and Hep were independent prognostic indicators of gastric carcinoma. The combination of Cdx2 and Hep expression was significantly lower in diffuse-type carcinoma than in intestinal or mixed-type carcinoma. Multivariate analysis revealed that Cdx2 and Hep expression was an independent prognostic indicator of gastric carcinoma (P < 0.001). CONCLUSIONS These data suggest that combined analysis of Cdx2 and Hep has significant value in distinguishing histologic types and in predicting the prognosis of gastric carcinoma.
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Affiliation(s)
- Zhaoqing Fan
- Department of Surgery, Peking University School of Oncology and Beijing Cancer Hospital, Beijing, PR China
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21
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Olsen L, Bressendorff S, Troelsen JT, Olsen J. Differentiation-dependent activation of the human intestinal alkaline phosphatase promoter by HNF-4 in intestinal cells. Am J Physiol Gastrointest Liver Physiol 2005; 289:G220-6. [PMID: 15831710 DOI: 10.1152/ajpgi.00449.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The intestinal alkaline phosphatase gene (ALPI) encodes a digestive brush-border enzyme, which is highly upregulated during small intestinal epithelial cell differentiation. To identify new putative promoter motifs responsible for the regulation of ALPI expression during differentiation of the enterocytes, we have conducted a computer-assisted cis-element search of the proximal human ALPI promoter sequence. A putative recognition site for the transcription factor hepatocyte nuclear factor (HNF)-4 was predicted at the positions from -94 to -82 in relation to the translational start site. The ability of HNF-4alpha to stimulate the expression from the ALPI promoter was investigated in the nonintestinal Hela cell line. Cotransfection with an HNF-4alpha expression vector demonstrated a direct activation of the ALPI promoter through this -94 to -82 element. EMSA showed that HNF-4alpha from nuclear extracts of differentiated intestinal epithelial cells (Caco-2) bound with high affinity to the predicted HNF-4 binding site. A 521 bp promoter fragment containing the HNF-4 binding site demonstrated a differentiation-dependent increase in promoter activity in Caco-2 cells. The presence of the HNF-4 binding site was necessary for this increase to occur.
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Affiliation(s)
- Line Olsen
- Dept. of Medical Biochemistry and Genetics, University of Copenhagen, The Panum Institute Bldg. 6.4. Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
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22
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Chen L, Wang P, Andrade CF, Zhao IY, Dubé PE, Brubaker PL, Liu M, Jin T. PKA independent and cell type specific activation of the expression of caudal homeobox gene Cdx-2 by cyclic AMP. FEBS J 2005; 272:2746-59. [PMID: 15943809 DOI: 10.1111/j.1742-4658.2005.04694.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cdx-2 is a transactivator for the proglucagon gene in pancreatic and intestinal endocrine cells. Cdx-2 is also expressed in differentiated intestinal epithelia of nonendocrine origin. Cdx-2-/- mice are embryonic lethal, while Cdx-2+/- mutants show multiple malfunctions including the formation of intestinal polyps. Within the polyps, the remaining wild type Cdx-2 allele ceases its expression, while the expression of both Cdx-2 and proglucagon in the endocrine cells remains unaltered, indicating that Cdx-2 could be haplo-insufficient for nonendocrine cells, but not for proglucagon producing endocrine cells. We propose that mechanisms underlying Cdx-2 expression and auto-regulation [Xu F, Li H & Jin T (1999), J Biol Chem274, 34310-34316] differ in these two types of cells. We show here that forskolin and cAMP upregulate Cdx-2 expression in proglucagon producing cells, but not in colon cancer cells and primary intestinal cell cultures. It is unlikely that the activation is mainly mediated by PKA, because the activation was observed in a PKA deficient cell line. Co-transfecting a dominant negative Ras expression plasmid substantially repressed the Cdx-2 promoter, in contrast to a previous finding that Ras is a negative factor for Cdx-2 expression in colon cancer cells. Furthermore, forskolin activated ERK1/2 phosphorylation in the endocrine cells, and attenuation of ERK1/2 phosphorylation by its inhibitor is associated with attenuated Cdx-2 expression. Finally, an Epac pathway specific cAMP analogue stimulated both ERK1/2 phosphorylation and Cdx-2 expression. Taken together, our observations suggest that Cdx-2 expression is regulated by the second messenger cAMP, cell-type specifically, via the Epac pathway.
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Affiliation(s)
- Liang Chen
- Division of Cell and Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, Ontario
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23
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Maier EA, Dusing MR, Wiginton DA. Cdx binding determines the timing of enhancer activation in postnatal duodenum. J Biol Chem 2005; 280:13195-202. [PMID: 15677472 DOI: 10.1074/jbc.m413158200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mammalian intestine, adenosine deaminase (ADA) is expressed at high levels only along the villi of the duodenal epithelium. A duodenum-specific enhancer identified in the second intron of the human ADA gene controls this pattern of expression. This enhancer faithfully recapitulates this expression pattern in transgenic mice, when included in CAT reporter gene constructions. Multiple binding sites for PDX-1 and GATA factors were previously identified within the approximately 300-bp region that encompasses the enhancer. Mutation analyses demonstrated that binding of PDX-1 and of GATA-4 was absolutely essential for enhancer function. In the present study, we have identified additional enhancer binding sites for Cdx factors, for YY1, and for NFI family members. Detailed EMSA studies were used to confirm binding at these sites. This brings the number of confirmed binding sites within the enhancer to thirteen, with five different factors or family of factors contributing to the putative enhanceosome complex. Mutation analysis was utilized to examine the specific roles of the newly identified sites. Two sites were identified that bound both Cdx1 and Cdx2. Mutations were identified in these two sites that completely and specifically eliminated Cdx binding. In transgenic mice, these enhancer mutations dramatically changed the developmental timing of enhancer activation (delaying it by 2-3 weeks) without affecting other aspects of enhancer function. In the chromatin context of certain transgenic insertion sites, mutation of the two YY1 sites to specifically ablate binding caused a delay in enhancer activation similar to that observed with the Cdx mutations. No overt changes were observed from mutation of the NFI site.
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Affiliation(s)
- Elizabeth A Maier
- Department of Pediatrics, Division of Developmental Biology, University of Cincinnati College of Medicine and Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio 45229, USA
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24
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Wang L, Klopot A, Freund JN, Dowling LN, Krasinski SD, Fleet JC. Control of differentiation-induced calbindin-D9k gene expression in Caco-2 cells by cdx-2 and HNF-1alpha. Am J Physiol Gastrointest Liver Physiol 2004; 287:G943-53. [PMID: 15217781 PMCID: PMC2701355 DOI: 10.1152/ajpgi.00121.2004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Calbindin D9k (CaBP) is critical for intestinal calcium absorption; its in vivo expression is restricted to differentiated enterocytes of the small intestine. Our goal was to identify factors controlling the transcriptional regulation of this gene in the human intestine. Both the natural gene and a 4600-bp promoter construct were strongly regulated by differentiation (>100-fold) but not by treatment with 1,25(OH)2 vitamin D (<2-fold) in the Caco-2 clone TC7. Deletion-mutation studies revealed that conserved promoter sequences for cdx-2 (at -3158 bp) and hepatocyte nuclear factor (HNF)-1 (at -3131 and at -98 bp) combined to control CaBP expression during differentiation. Other putative response elements were not important for CaBP regulation in TC7 cells (CCAAT enhancer binding protein, pancreatic duodenal homebox-1 (pdx-1), a proximal cdx-2 element). Mutation of the distal HNF-1 site had the greatest impact on CaBP gene expression through disruption of HNF-1alpha binding; both basal and differentiation-mediated CaBP expression was reduced by 80%. In contrast, mutation of the distal cdx-2 element reduced only basal CaBP expression. Whereas a 60% reduction of CaBP mRNA in the duodenum of HNF-1alpha null mice confirmed the physiological importance of HNF-1alpha for CaBP gene regulation, additional studies showed that maximal CaBP expression requires the presence of both HNF-1alpha and cdx-2. Our data suggest that cdx-2 is a permissive factor that influences basal CaBP expression in enterocytes and that HNF-1alpha modulates CaBP gene expression during cellular differentiation.
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Affiliation(s)
- Liyong Wang
- Interdepartmental Nutrition Program, Purdue University, West Lafayette, Indiana 47907, USA
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25
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Barley NF, Taylor V, Shaw-Smith CJ, Chakravarty P, Howard A, Legon S, Walters JRF. Human ileal bile acid-binding protein promoter and the effects of CDX2. ACTA ACUST UNITED AC 2004; 1630:138-43. [PMID: 14654244 DOI: 10.1016/j.bbaexp.2003.09.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The ileal bile acid-binding protein (IBABP) is important for the reabsorption of bile salts in the distal small intestine. Studies with the human IBABP gene (FABP6, on chromosome 5q33.3-q34) defined the major transcription start site and identified conserved elements. A consensus element for the caudal-related homeobox factor CDX2 was functional in gel-shift assays and in transfection experiments.
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Affiliation(s)
- Natalie F Barley
- Gastroenterology Section, Faculty of Medicine, Imperial College London, UK
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26
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Gautier-Stein A, Domon-Dell C, Calon A, Bady I, Freund JN, Mithieux G, Rajas F. Differential regulation of the glucose-6-phosphatase TATA box by intestine-specific homeodomain proteins CDX1 and CDX2. Nucleic Acids Res 2003; 31:5238-46. [PMID: 12954759 PMCID: PMC203330 DOI: 10.1093/nar/gkg747] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Glucose-6-phosphatase (Glc6Pase), the last enzyme of gluconeogenesis, is only expressed in the liver, kidney and small intestine. The expression of the Glc6Pase gene exhibits marked specificities in the three tissues in various situations, but the molecular basis of the tissue specificity is not known. The presence of a consensus binding site of CDX proteins in the minimal Glc6Pase gene promoter has led us to consider the hypothesis that these intestine-specific CDX factors could be involved in the Glc6Pase-specific expression in the small intestine. We first show that the Glc6Pase promoter is active in both hepatic HepG2 and intestinal CaCo2 cells. Using gel shift mobility assay, mutagenesis and competition experiments, we show that both CDX1 and CDX2 can bind the minimal promoter, but only CDX1 can transactivate it. Consistently, intestinal IEC6 cells stably overexpressing CDX1 exhibit induced expression of the Glc6Pase protein. We demonstrate that a TATAAAA sequence, located in position -31/-25 relating to the transcription start site, exhibits separable functions in the preinitiation of transcription and the transactivation by CDX1. Disruption of this site dramatically suppresses both basal transcription and the CDX1 effect. The latter may be restored by inserting a couple of CDX- binding sites in opposite orientation similar to that found in the sucrase-isomaltase promoter. We also report that the specific stimulatory effect of CDX1 on the Glc6Pase TATA-box, compared to CDX2, is related to the fact that CDX1, but not CDX2, can interact with the TATA-binding protein. Together, these data strongly suggest that CDX proteins could play a crucial role in the specific expression of the Glc6Pase gene in the small intestine. They also suggest that CDX transactivation might be essential for intestine gene expression, irrespective of the presence of a functional TATA box.
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Affiliation(s)
- Amandine Gautier-Stein
- INSERM U.449, Faculté de Médecine Laennec, Rue Guillaume Paradin, 69372 Lyon cedex 08, France
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27
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Shekels LL, Ho SB. Characterization of the mouse Muc3 membrane bound intestinal mucin 5' coding and promoter regions: regulation by inflammatory cytokines. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1627:90-100. [PMID: 12818427 DOI: 10.1016/s0167-4781(03)00081-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The mouse Muc3 mucin is a membrane-bound glycoprotein highly expressed in the intestinal tract. We have characterized the mouse Muc3 5' structure and regulation of its promoter by cytokines and growth factors. The first two exons of Muc3 are separated by an intron of over 8 kb. Exon 3 contains the tandem repeat domain. Ten exons reside 3' to the tandem repeat domain. The 5' nonrepetitive sequence contains 104 amino acids characterized by a putative signal sequence, a single cysteine and 28% serine/threonine. No TATA box is found near the transcription start site. The promoter has consensus binding sites for AP1, CREB, SP1, NF kappa B, GATA binding protein and Cdx. Muc3 promoter constructs demonstrate that IL4, IL6, EGF or PMA increased promoter activity to 35-58% of control. TNF alpha and IFN gamma showed lesser stimulation. These data indicate that cytokines and growth factors are capable of regulating Muc3 gene expression, suggesting that this protein may play an active role in intestinal mucosal defense.
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Affiliation(s)
- Laurie L Shekels
- Department of Medicine, University of Minnesota and VA Medical Center, Research 151, 1 Veterans Drive, Minneapolis, MN 55417, USA.
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28
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Fleet JC, Wang L, Vitek O, Craig BA, Edenberg HJ. Gene expression profiling of Caco-2 BBe cells suggests a role for specific signaling pathways during intestinal differentiation. Physiol Genomics 2003; 13:57-68. [PMID: 12644633 DOI: 10.1152/physiolgenomics.00152.2002] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the pattern of gene expression resulting from spontaneous differentiation of Caco-2 BBe cells to gain insight into the molecular changes necessary for enterocyte differentiation. RNA was prepared from cells harvested at three cell stages: proliferating (50% confluent, 2 days in culture), postproliferative nondifferentiated (8 days), and differentiated (15 days). Gene expression profiles were determined using Affymetrix Human Genome U95A GeneChips. Differentially expressed genes were identified following statistical analysis (i.e., ANOVA, bootstrapping adjustments to P values, false detection rate criterion). We identified 1,150 unique genes as differentially expressed; expression of 48.6% fell and 46% increased from 2 to 15 days, while 5.4% had expression that either peaked or dipped at 8 days. Genes expressed during differentiation included several small-intestine-specific genes involved in nutrient transport/metabolism, e.g., DCT1, hephaestin, folate receptor 1, sucrase-isomaltase, and apolipoproteins CI, CIII, B100, H, and M, indicating that this colonic adenocarcinoma cell line has a hybrid colonocyte/enterocyte phenotype. Patterns of gene expression based upon functional classification suggest a role for cell-cell/cell-matrix interactions, suppression of Wnt signaling, and activation of TGFbeta and phosphatidylinositol 3-kinase pathways during enterocyte differentiation.
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Affiliation(s)
- James C Fleet
- Interdepartmental Nutrition Program, Purdue University, West Lafayette, Indiana 47907,
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29
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Sterling KM, Cutroneo KR. Differentiation-dependent induction of CYP1A1 in cultured rat small intestinal epithelial cells, colonocytes, and human colon carcinoma cells: basement membrane-mediated apoptosis. J Cell Biochem 2003; 86:440-50. [PMID: 12210751 DOI: 10.1002/jcb.10237] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Rat small intestinal epithelial cells and human colon adenocarcinoma cells cultured on Matrigel expressed the differentiation specific enzyme, sucrase-isomaltase, as determined by indirect immunofluorescence. Rat small intestinal epithelial cells, rat colonocytes, and human colon adenocarcinoma cells developed an altered morphology when cultured on Matrigel and became apoptotic within 24-48 h. Benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin caused a 2- and 5-fold induction, respectively, of ethoxyresorufin-o-deethylase activity in rat small intestinal epithelial cells cultured on Matrigel. Benzo[a]pyrene- or 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced ethoxyresorufin-o-deethylase activity in rat small intestinal epithelial cells cultured on plastic was not detected. 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment caused a 14-fold induction of transfected, rat CYP1A1-promoter-luciferase activity in rat small intestinal epithelial cells cultured on Matrigel. Benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment induced ethoxyresorufin-o-deethylase activity by 6- and 1.6-fold, respectively in rat colonocytes cultured on Matrigel. Induction of ethoxyresorufin-o-deethylase activity was not observed in rat colonocytes cultured on plastic. CYP1A1-promoter-luciferase activity was induced 3-fold by 2,3,7,8-tetrachlorodibenzo-p-dioxin in rat colonocytes cultured on Matrigel. Induction of CYP1A1-promoter-luciferase activity in rat small intestinal epithelial cells or rat colonocytes cultured on plastic was not observed. Ethoxyresorufin-o-deethylase activity in human colon adenocarcinoma cells, cultured on either plastic or Matrigel, was induced 7-fold by benzo[a]pyrene. 2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced ethoxyresorufin-o-deethylase activity was 2-fold greater in human colon adenocarcinoma cells cultured on Matrigel compared to cells cultured on plastic. Extracellular matrix-mediated differentiation and apoptosis of intestinal cells provide in vitro systems for study of the regulation of CYP1A1 expression, carcinogen activation in the gut and mechanism(s) of apoptosis of colon cancer cells.
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Affiliation(s)
- Kenneth M Sterling
- Dartmouth College, Department of Physics and Astronomy, 6127 Wilder Laboratory, Hanover, New Hampshire 03755-3528, USA.
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van Wering HM, Moyer L, Grand RJ, Krasinski SD. Novel interaction at the Cdx-2 binding sites of the lactase-phlorizin hydrolase promoter. Biochem Biophys Res Commun 2002; 299:587-93. [PMID: 12459179 DOI: 10.1016/s0006-291x(02)02697-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cdx-2 is an intestine-specific homeodomain-containing transcription factor that activates the promoters of intestinal genes through specific interactions with the consensus, TTTAT/C. Here, we demonstrate that Cdx-2 interacts with the lactase-phlorizin hydrolase (LPH) promoter at cis-element (CE)-LPH1a (-54 to -40 bp) as well as the LPH TATA-box. Affinity comparisons between SIF-1, CE-LPH1a, and the LPH TATA-box revealed that the TATA-box has the lowest affinity for Cdx-2. Characterization of CE-LPH1a using EMSAs revealed binding of a novel, non-Cdx-2 complex in multiple cell lines that bind to sequence that is different from that of the Cdx-2 binding site. Heterologous promoter analysis in transient transfection assays revealed a repressor function for this protein, and thus, it was designated as nuclear factor-LPH1/repressor (NF-LPH1/R). These data are consistent with the hypothesis that NF-LPH1/R represses LPH gene expression in non-Cdx-2-producing cells, and that this repression is released in cells that synthesize Cdx-2, such as those in the intestinal epithelium.
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Affiliation(s)
- Herbert M van Wering
- Division of Gastroenterology and Nutrition, Department of Medicine, Harvard Medical School, Children's Hospital Boston, 300 Longwood Avenue, Boston, MA 02115, USA
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31
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Moucadel V, Totaro MS, Dell CD, Soubeyran P, Dagorn JC, Freund JN, Iovanna JL. The homeobox gene Cdx1 belongs to the p53-p21(WAF)-Bcl-2 network in intestinal epithelial cells. Biochem Biophys Res Commun 2002; 297:607-15. [PMID: 12270138 DOI: 10.1016/s0006-291x(02)02250-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Because the Cdx1 homeobox gene stimulates proliferation and induces transformation and tumorigenesis, it has been investigated whether it is involved in the complex network comprising p53, p21(WAF), and Bcl-2 in intestinal epithelial cells. Non-transformed intestinal IEC-6 cells and colon adenocarcinoma SW480 cells were used to study the putative molecular relationship between Cdx1, p53, p21(WAF), and Bcl-2. Wild-type p53 inhibited the transcriptional activity of the Cdx1 promoter whereas the inactive mutant p53(mut22/23) had no effect. Induction of Cdx1 expression had no direct effect on p53 expression and activity. However, it inhibited the transcriptional activity of the p21(WAF) promoter through Cdx1 binding to the p21(WAF) TATA-box and increased the transcriptional activity of the Bcl-2 promoter P2 through a consensus Cdx-binding site. Finally, compared to control cells, Cdx1-overexpressing cells were more resistant to adriamycin-induced apoptosis, probably because they do not show concomitant decrease in endogenous Bcl-2 level. In conclusion, Cdx1 is a negatively regulated target of p53 in intestinal cells. Its regulation of p21(WAF) and Bcl-2 is opposite to that of p53 and is p53-independent. Cdx1 belongs to the regulatory networks of apoptosis, proliferation, and differentiation. These results emphasize the oncogenic potential of Cdx1.
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Affiliation(s)
- Virginie Moucadel
- Centre de Recherche INSERM, EMI 0116, 163 av de Luminy, 13009 Marseille, France
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32
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Uesaka T, Lu H, Katoh O, Watanabe H. Heparin-binding EGF-like growth factor gene transcription regulated by Cdx2 in the intestinal epithelium. Am J Physiol Gastrointest Liver Physiol 2002; 283:G840-7. [PMID: 12223343 DOI: 10.1152/ajpgi.00075.2002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Development and differentiation of the intestinal epithelium appear to be regulated by various growth factors. Using cDNA microarrays, we identified heparin-binding EGF-like growth factor (HB-EGF) as one of the genes induced by intestinal-specific transcription factor Cdx2 in an intestinal undifferentiated rat cell line, intestinal epithelial cell (IEC)-6. Both Cdx2 and HB-EGF stimulated cell proliferation and migration, and their effects were inhibited partially by an EGF receptor-specific tyrosine kinase inhibitor, PD-153035. HB-EGF may function as one of the mediators of Cdx2 and may be associated with the proliferation and migration in the intestinal epithelium. The Cdx2 protein can bind to the Cdx2-binding element of the HB-EGF gene. Reporter gene analyses showed that the HB-EGF gene promoter is Cdx2 responsive and that the activity of the promoter in the IEC-6 cells depends on the number of consensus Cdx2-binding site-like sequences. These data indicate that HB-EGF gene expression can be regulated by Cdx2 and serves to mediate the control of Cdx2 of the proliferation and migration of IEC-6 cells.
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Affiliation(s)
- Toshihiro Uesaka
- Department of Cellular Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan.
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Sakaguchi T, Gu X, Golden HM, Suh E, Rhoads DB, Reinecker HC. Cloning of the human claudin-2 5'-flanking region revealed a TATA-less promoter with conserved binding sites in mouse and human for caudal-related homeodomain proteins and hepatocyte nuclear factor-1alpha. J Biol Chem 2002; 277:21361-70. [PMID: 11934881 DOI: 10.1074/jbc.m110261200] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Claudin-2 is a structural component of tight junctions in the kidneys, liver, and intestine, but the mechanisms regulating its expression have not been defined. The 5'-flanking region of the claudin-2 gene contains binding sites for intestine-specific Cdx homeodomain proteins and hepatocyte nuclear factor (HNF)-1, which are conserved in human and mouse. Both Cdx1 and Cdx2 activated the claudin-2 promoter in the human intestinal epithelial cell line Caco-2. HNF-1alpha augmented the Cdx2-induced but not Cdx1-induced transcriptional activation of the human claudin-2 promoter. In mice, HNF-1alpha was required for claudin-2 expression in the villus epithelium of the ileum and within the liver but not in the kidneys, indicating an organ-specific function of HNF-1alpha in the regulation of claudin-2 gene expression. Tight junction structural components, which determine epithelial polarization and intestinal barrier function, can be regulated by homeodomain proteins that control the differentiation of the intestinal epithelium.
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Affiliation(s)
- Takanori Sakaguchi
- Gastrointestinal Unit, Department of Medicine, Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital & Harvard Medical School, Boston, Massachusetts 02114, USA
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Zhang L, E X, Luker KE, Shao JS, Levin MS, Suh E, Li E. Analysis of human cellular retinol-binding protein II promoter during enterocyte differentiation. Am J Physiol Gastrointest Liver Physiol 2002; 282:G1079-87. [PMID: 12016134 DOI: 10.1152/ajpgi.00041.2001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cellular retinol binding protein II (CRBP II) is a vitamin A-binding protein that is expressed specifically in small intestinal villus absorptive cells. Previous studies have shown that retinoic acid upregulates endogenous human CRBP II gene expression in differentiated Caco-2 cells. To better characterize the regulation of human CRBP II expression, we analyzed the ability of receptor-selective agonists to enhance transcription from the 5'-upstream flanking region of the human CRBP II gene. Stable transfection experiments showed that the proximal 2.8-kb region of the human CRBP II gene is sufficient for retinoic acid inducibility in differentiated Caco-2 cells. However, direct sequence analysis and transient transfection experiments indicate that, unlike the rat CRBP II promoter, the human CRBP II promoter is not a direct retinoid X receptor target. The results indicate that the retinoic acid responsiveness of the human CRBP II promoter is mediated by an indirect mechanism and that this mechanism is associated with enterocyte differentiation.
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Affiliation(s)
- Liang Zhang
- Department of Medicine, Washington University-St. Louis School of Medicine, St. Louis, Missouri 63110, USA
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Domon-Dell C, Freund JN. Stimulation of Cdx1 by oncogenic beta-catenin/Tcf4 in colon cancer cells; opposite effect of the CDX2 homeoprotein. FEBS Lett 2002; 518:83-7. [PMID: 11997022 DOI: 10.1016/s0014-5793(02)02650-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The homeobox gene Cdx1 is a regulator of intestinal epithelial cell proliferation and differentiation. Using a transfection approach, we showed here that the oncogenic activation of the beta-catenin pathway stimulates the endogenous expression of the Cdx1 mRNA as well as the activity of the Cdx1 promoter in cancer cells of the human colon. Reciprocally, the paralogue homeobox gene Cdx2 exerts an inhibitory effect on the basal and on the beta-catenin-stimulated activity of the Cdx1 promoter. The inhibitory effect of CDX2 requires the intact homeodomain. It is not dependent on canonical CDX binding sites in the Cdx1 promoter nor on the cis-elements specifically targeted by the beta-catenin/Tcf complex. We conclude that the oncogenically activated beta-catenin and CDX2 have opposite and independent effects on the Cdx1 homeobox gene.
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Affiliation(s)
- Claire Domon-Dell
- Institut National de la Santé et de la Recherche Médicale, Unité 381, 3 avenue Molière, 67200, Strasbourg, France
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Abstract
An essential process for fatty acid digestion, absorption and assimilation is the constant replacement of mature intestinal epithelial cells by differentiating stem cells. Free fatty acids (FFA) and PYY may act in concert to alter mucosal cell differentiation through the cytoskeletal-extracellular matrix interactions. PYY induced expression of tetraspanins and intestinal fatty acid binding protein (I-FABP) may be part of a mechanism whereby FFA modulate expression of differentiation dependent proteins in the mucosa. This modulation provides a means for FFA to act as signal molecules in the feedback regulation of their own assimilation.
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Affiliation(s)
- Gregory W Aponte
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720-3104, USA.
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Arai H, Miyamoto KI, Yoshida M, Yamamoto H, Taketani Y, Morita K, Kubota M, Yoshida S, Ikeda M, Watabe F, Kanemasa Y, Takeda E. The polymorphism in the caudal-related homeodomain protein Cdx-2 binding element in the human vitamin D receptor gene. J Bone Miner Res 2001; 16:1256-64. [PMID: 11450701 DOI: 10.1359/jbmr.2001.16.7.1256] [Citation(s) in RCA: 181] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The major physiological activity of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] is the regulation of calcium absorption in the small intestine, and the level of vitamin D receptor (VDR) is an important factor in this regulation. In a previous study, we indicated-that the caudal-related homeodomain Cdx-2 played an important role in the intestine-specific transcription of the human VDR gene. In this study, the polymorphism was identified in the core sequence 5'-ATAAAAACTTAT-3' in the Cdx-2 binding site in the VDR gene promoter. In 261 Japanese women with genotyped VDR polymorphisms, 48 were genotype Cdx-A (adenine at -3731 nucleotides [nt] relative to the transcription start site of human VDR gene 5-ATAAAAACTTAT), 82 were genotype Cdx-G (guanine at -3731 nt, 5'-GTAAAAACTTAT-3'), and 131 were genotype Cdx-A/G (heterozygote). In postmenopausal Japanese women, the bone mineral density (BMD) in the lumbar spine (L2-L4) with the Cdx-G homozygote was 12% lower than that with the Cdx-A homozygote (p < 0.05). In electrophoretic gel mobility shift assay (EMSA), the oligonucleotide with Cdx-G allele markedly decreased the binding to Cdx-2 compared with that in the Cdx-A allele. The transcriptional activity of the VDR promoter with Cdx-G allele was decreased to 70% of the Cdx-A allele. In addition, in the herpes simplex virus thymidine kinase promoter, the Cdx-2 binding element with the G allele showed significantly lower transcriptional activity than that of the A allele. Thus, the polymorphism in the Cdx-2 binding site of the VDR gene (Cdx-polymorphism) would affect the expression of VDR in the small intestine. In addition, this polymorphism may modulate BMD in postmenopausal Japanese women.
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Affiliation(s)
- H Arai
- Department of Clinical Nutrition, School of Medicine, University of Tokushima, Japan
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Houde M, Laprise P, Jean D, Blais M, Asselin C, Rivard N. Intestinal epithelial cell differentiation involves activation of p38 mitogen-activated protein kinase that regulates the homeobox transcription factor CDX2. J Biol Chem 2001; 276:21885-94. [PMID: 11283019 DOI: 10.1074/jbc.m100236200] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The intracellular signaling pathways responsible for cell cycle arrest and differentiation along the crypt-villus axis of the human small intestine remain largely unknown. p38 mitogen-activated protein kinases (MAPKs) have recently emerged as key modulators of various vertebrate cell differentiation processes. In order to elucidate further the mechanism(s) responsible for the loss of proliferative potential once committed intestinal cells begin to differentiate, the role and regulation of p38 MAPK with regard to differentiation were analyzed in both intact epithelium as well as in well established intestinal cell models recapitulating the crypt-villus axis in vitro. Results show that phosphorylated and active forms of p38 were detected primarily in the nuclei of differentiated villus cells. Inhibition of p38 MAPK signaling by 2-20 microm SB203580 did not affect E2F-dependent transcriptional activity in subconfluent Caco-2/15 or HIEC cells. p38 MAPK activity dramatically increased as soon as Caco-2/15 cells reached confluence, whereas addition of SB203580 during differentiation of Caco-2/15 cells strongly attenuated sucrase-isomaltase gene and protein expression as well as protein expression of villin and alkaline phosphatase. The binding of CDX2 to the sucrase-isomaltase promoter and its transcriptional activity were significantly reduced by SB203580. Pull-down glutathione S-transferase and immunoprecipitation experiments demonstrated a direct interaction of CDX3 with p38. Finally, p38-dependent phosphorylation of CDX3 was observed in differentiating Caco-2/15 cells. Taken together, our results indicate that p38 MAPK may be involved in the regulation of CDX2/3 function and intestinal cell differentiation.
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Affiliation(s)
- M Houde
- CIHR Group on Functional Development and Physiopathology of the Digestive Tract, Département d'Anatomie et Biologie Cellulaire, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Abstract
Intestinal reabsorption of bile salts plays a crucial role in human health and disease. This process is primarily localized to the terminal ileum and is mediated by a 48-kd sodium-dependent bile acid cotransporter (SLC10A2 = ASBT). ASBT is also expressed in renal tubule cells, cholangiocytes, and the gallbladder. Exon skipping leads to a truncated version of ASBT, which sorts to the basolateral surface and mediates efflux of bile salts. Inherited mutation of ASBT leads to congenital diarrhea secondary to bile acid malabsorption. Partial inhibition of ASBT may be useful in the treatment of hypercholesterolemia and intrahepatic cholestasis. During normal development in the rat ileum, ASBT undergoes a biphasic pattern of expression with a prenatal onset, postnatal repression, and reinduction at the time of weaning. The bile acid responsiveness of the ASBT gene is not clear and may be dependent on both the experimental model used and the species being investigated. Future studies of the transcriptional and posttranscriptional regulation of the ASBT gene and analysis of ASBT knockout mice will provide further insight into the biology, physiology, and pathophysiology of intestinal bile acid transport.
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Affiliation(s)
- B L Shneider
- Mount Sinai Medical Center, New York, NY 10029, USA
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40
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Clements D, Rex M, Woodland HR. Initiation and early patterning of the endoderm. INTERNATIONAL REVIEW OF CYTOLOGY 2001; 203:383-446. [PMID: 11131522 DOI: 10.1016/s0074-7696(01)03012-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We review the early stages of endoderm formation in the major animal models. In Amphibia maternal molecules are important in initiating endoderm formation. This is followed by successive signaling events that establish and then pattern the endoderm. In other organisms there are differences in endodermal development, particularly in the initial, prephylotypic stages. Later many of the same key families of transcription factors and signaling cassettes are used in all animals, but more work will be needed to establish exact evolutionary homologies.
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Affiliation(s)
- D Clements
- Department of Biological Sciences, University of Warwick, Coventry, United Kingdom
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Suh E, Wang Z, Swain GP, Tenniswood M, Traber PG. Clusterin gene transcription is activated by caudal-related homeobox genes in intestinal epithelium. Am J Physiol Gastrointest Liver Physiol 2001; 280:G149-56. [PMID: 11123208 DOI: 10.1152/ajpgi.2001.280.1.g149] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Caudal-related homeobox (Cdx) proteins play an important role in development and differentiation of the intestinal epithelium. Using cDNA differential display, we identified clusterin as a prominently induced gene in a Cdx2-regulated cellular model of intestinal differentiation. Transfection experiments and DNA-protein interaction assays showed that clusterin is an immediate downstream target gene for Cdx proteins. The distribution of clusterin protein in the intestine was assessed during development and in the adult epithelium using immunohistochemistry. In the adult mouse epithelium, clusterin protein was localized in both crypt and villus compartments but not in interstitial cells of the intestinal mucosa. Together, these data suggest that clusterin is a direct target gene for Cdx homeobox proteins, and the pattern of clusterin protein expression suggests that it is associated with the differentiated state in the intestinal epithelium.
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Affiliation(s)
- E Suh
- Department of Internal Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
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Sivagnanasundaram S, Islam I, Talbot I, Drummond F, Walters JR, Edwards YH. The homeobox gene CDX2 in colorectal carcinoma: a genetic analysis. Br J Cancer 2001; 84:218-25. [PMID: 11161380 PMCID: PMC2363702 DOI: 10.1054/bjoc.2000.1544] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Accumulation of mutations in tumour suppressor genes and oncogenes has been proposed to underlie the initiation and progression of sporadic colorectal cancer (CRC). Evidence is accumulating to suggest that the caudal homeobox gene CDX2 is implicated in the pathogenesis of CRC. The CDX2 transcription factor is expressed in intestinal epithelium and is markedly down-regulated in colon tumours. Furthermore, Cdx2 heterozygous null mice develop multiple intestinal tumours. In this present study, we have investigated CDX2 as a potential candidate gene for sporadic CRC by a thorough search of all exons and exon/intron boundaries for DNA polymorphisms and rare variants in a panel of CRC tumours. 6 polymorphisms were identified and the haplotypes determined. In addition two rare variants were found, one of which was only identified in DNA from a CRC case. Loss of heterozygosity was observed in 3 out of 28 informative CRC cases. A possible association between particular haplotypes and tumour progression was also suggested by the data. In addition a preliminary analysis of the relative expression of CDX2 alleles in tumour/normal tissue suggested some variation in the levels, however further analysis is required before any conclusions can be drawn. While CDX2 mutations predisposing to sporadic CRC have not been identified, this study has established that loss of CDX2 contributes towards the progression of some sporadic CRC tumours.
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MESH Headings
- Adult
- Aged
- Aged, 80 and over
- Alleles
- CDX2 Transcription Factor
- Cohort Studies
- Colorectal Neoplasms/genetics
- Colorectal Neoplasms/pathology
- DNA Mutational Analysis
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Neoplasm/chemistry
- DNA, Neoplasm/genetics
- Exons
- Female
- Gene Frequency
- Haplotypes
- Homeodomain Proteins/genetics
- Humans
- Introns
- Loss of Heterozygosity
- Male
- Middle Aged
- Mutation
- Polymorphism, Genetic
- Polymorphism, Single-Stranded Conformational
- RNA Splicing/genetics
- RNA, Neoplasm/genetics
- RNA, Neoplasm/metabolism
- Sequence Analysis, DNA
- Trans-Activators
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Affiliation(s)
- S Sivagnanasundaram
- MRC Human Biochemical Genetics Unit, Biology Department, University College London, Wolfson House, 4 Stephenson Way, London, NW1 2HE
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Dusing MR, Brickner AG, Lowe SY, Cohen MB, Wiginton DA. A duodenum-specific enhancer regulates expression along three axes in the small intestine. Am J Physiol Gastrointest Liver Physiol 2000; 279:G1080-93. [PMID: 11053006 DOI: 10.1152/ajpgi.2000.279.5.g1080] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Adenosine deaminase (ADA) is expressed at high levels in the epithelium of proximal small intestine. Transgenic mice were used to characterize the regulatory region governing this activation. A duodenum-specific enhancer is located in intron 2 of the human ADA gene at the central site among a cluster of seven DNase I-hypersensitive sites present in duodenal DNA. Flanking DNA, including the remaining hypersensitive sites, is required for consistent high-level enhancer function. The enhancer activates expression in a pattern identical to endogenous ADA along both the anterior-posterior axis of the small intestine and the crypt-villus differentiation axis of the intestinal epithelium. Timing of activation by the central enhancer mimics endogenous mouse ADA activation, occurring at 2-3 wk of age. However, two upstream DNA segments, one proximal and one distal, collaborate to change enhancer activation to a perinatal time point. Studies with duodenal nuclear extracts identified five distinct DNase I footprints within the enhancer. Protected regions encompass six putative binding sites for the transcription factor PDX-1, as well as proposed CDX, hepatocyte nuclear factor-4, and GATA-type sites.
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Affiliation(s)
- M R Dusing
- Division of Developmental Biology, Department of Pediatrics, University of Cincinnati College of Medicine and Children's Hospital Research Foundation, Cincinnati, Ohio 45229, USA
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44
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Abstract
BACKGROUND & AIMS The intestine-specific transcription factors Cdx1 and Cdx2 are candidate genes for directing intestinal development, differentiation, and maintenance of the intestinal phenotype. This study focused on the complex patterns of expression of Cdx1 and Cdx2 during mouse gastrointestinal development. METHODS Embryonic and postnatal mouse tissues were analyzed by immunohistochemistry to determine protein expression of Cdx1 and Cdx2 in the developing intestinal tract. RESULTS Cdx2 protein expression was observed at 9. 5 postcoitum (pc), whereas weak expression of Cdx1 protein was first seen at 12.5 pc in the distal developing intestine (hindgut). Expression of Cdx1 increased from 13.5 to 14.5 pc during the endoderm/epithelial transition with predominately distal expression. In contrast to Cdx1, there was intense expression of Cdx2 in all but the distal portions of the developing intestine. Cdx2 expression remained low in the distal colon throughout postnatal development. A gradient of expression formed in the crypt-villus axis, with Cdx1 primarily in the crypt and Cdx2 primarily in the villus. CONCLUSIONS Direct comparison of the patterns of Cdx1 and Cdx2 protein expression during development as performed in this study provides new insights into their potential functional roles. The relative expression of Cdx1 to Cdx2 protein may be important in the anterior to posterior patterning of the intestinal epithelium and in defining patterns of proliferation and differentiation along the crypt-villus axis.
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Affiliation(s)
- D G Silberg
- Division of Gastroenterology, Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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45
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Basson MD, Liu YW, Hanly AM, Emenaker NJ, Shenoy SG, Gould Rothberg BE. Identification and comparative analysis of human colonocyte short-chain fatty acid response genes. J Gastrointest Surg 2000; 4:501-12. [PMID: 11077326 DOI: 10.1016/s1091-255x(00)80093-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Short-chain fatty acids (SCFAs) butyrate, propionate, and acetate produced during fiber fermentation promote colonic differentiation and can reverse or suppress neoplastic progression. We sought to identify candidate genes responsible for SCFA activity on colonocytes and to compare the relative activities of independent SCFAs. cDNA was generated from polyA+ mRNA isolated from control Caco-2 cells and cells treated with equimolar butyrate, propionate, and acetate. GeneCalling, a restriction-based differential RNA expression platform linked to a DNA sequence database lookup, was applied. A total of 30,000 individual genetic sequences were analyzed for differential expression among the three SCFAs. Differentially expressed peaks corresponding to cancer-related genes were isolated, sequenced, and cross-referenced to the GenBank human database. Gene identities were independently confirmed by oligonucleotide poisoning. More than 1000 gene fragments were identified as being substantially modulated in expression by butyrate. Butyrate tended to have the most pronounced effects and acetate the least. Five fragments selected for further study were fully sequenced and proved 100% homologous with human sequences for clusterin, amyloid precursor-like protein 2, and caudal homeobox 2 protein, not previously known to be modulated by SCFAs. In each case, a similar order of potency for the three SCFAs studied was observed. The common SCFAs appear to exert different effects. This study suggests the diversity of the SCFA response at the molecular level and facilitates identifying genes important in the biologic activity of dietary fiber.
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Affiliation(s)
- M D Basson
- Department of Surgery, Yale University, New Haven, CT 06520-8062, USA
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Abstract
The gut of vertebrates exhibits a common anteroposterior regional differentiation. The role of homeobox genes in establishing this pattern is inferred by their sites of expression. It is suggested that the primary source of positional information is in the endoderm, which subsequently establishes a 'dialogue' with the surrounding visceral layer of the lateral plate mesoderm. This results in the anatomical and physiological specialization of the adult gut.
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Affiliation(s)
- F Beck
- Department of Biochemistry, University of Leicester, United Kingdom.
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Kitchen PA, Fitzgerald AJ, Goodlad RA, Barley NF, Ghatei MA, Legon S, Bloom SR, Price A, Walters JR, Forbes A. Glucagon-like peptide-2 increases sucrase-isomaltase but not caudal-related homeobox protein-2 gene expression. Am J Physiol Gastrointest Liver Physiol 2000; 278:G425-8. [PMID: 10712262 DOI: 10.1152/ajpgi.2000.278.3.g425] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To determine the effect of glucagon-like peptide-2 (GLP-2) on sucrase-isomaltase and caudal-related homeobox protein-2 (Cdx-2) gene expression, male Wistar rats were divided into total parenteral nutrition (TPN)-fed and GLP-2-treated, TPN-fed groups. TPN was given via a jugular line, inserted under anesthesia, for 7 days. The treatment group received 40 microg/day of GLP-2 intravenously with the TPN diet. The small intestine and colon were weighed and measured. Tissue was obtained from the jejunum, terminal ileum, and midcolon. RNA analysis, morphometry, and microdissection were performed. The weight of the small intestine of GLP-2-treated rats was greater than that of TPN-fed rats (P < 0.001). GLP-2 increased the mean metaphase arrests/crypt in both the jejunum and ileum (P < 0.001). Ileal expression of sucrase-isomaltase was increased by 1. 6-fold (P < 0.05). Jejunal expression was increased by a similar amount, although not significantly (P = 0.08). There was no change in Cdx-2 gene expression. Thus GLP-2 can maintain small intestinal morphology and function, but effects on gene expression are not mediated by gross changes in the level of the mRNA for the homeobox protein Cdx-2.
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Affiliation(s)
- P A Kitchen
- St Mark's Hospital, Harrow HA1 3UJ, United Kingdom.
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Lynch J, Suh ER, Silberg DG, Rulyak S, Blanchard N, Traber PG. The caudal-related homeodomain protein Cdx1 inhibits proliferation of intestinal epithelial cells by down-regulation of D-type cyclins. J Biol Chem 2000; 275:4499-506. [PMID: 10660624 DOI: 10.1074/jbc.275.6.4499] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cdx1 is a homeodomain transcription factor that regulates intestine-specific gene expression. Experimental evidence suggests that Cdx1 may be involved in cell cycle regulation, but its role is ill defined and the mechanisms have not been explored. We used stable transfection of inducible constructs and transient expression with a replication-deficient adenovirus to induce Cdx1 expression in rat IEC6 cells, a non-transformed intestinal epithelial cell line that does not express Cdx1 protein. Expression of Cdx1 markedly reduced proliferation of IEC6 cells with accumulation of cells in the G(0)/G(1) phase of the cell cycle. Cell cycle arrest was accompanied by an increase in the hypophosphorylated forms of the retinoblastoma protein (pRb) and the pRb-related p130 protein. Protein levels of multiple cyclin-dependent kinase inhibitors were either unchanged (p16, p18, p21, p27, and p57) or were not detected (p15 and p19). Most significantly, levels of cyclins D1 and D2 were markedly diminished with Cdx1 expression, but not cyclins D3, E, or the G(1) kinases. Additionally, cyclin-dependent kinase-4 activity was decreased in association with decreased cyclin D protein. We conclude that Cdx1 regulates intestinal epithelial cell proliferation by inhibiting progression through G(0)/G(1), most likely via modulation of cyclin D1 and D2 protein levels.
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Affiliation(s)
- J Lynch
- Division of Gastroenterology, Department of Medicine and Genetics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Fang R, Santiago NA, Olds LC, Sibley E. The homeodomain protein Cdx2 regulates lactase gene promoter activity during enterocyte differentiation. Gastroenterology 2000; 118:115-27. [PMID: 10611160 DOI: 10.1016/s0016-5085(00)70420-3] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND & AIMS Lactase is the intestinal disaccharidase responsible for digestion of lactose, the predominant carbohydrate in milk. Transcription of the lactase gene is activated during enterocyte differentiation. We have characterized the interaction between the lactase promoter and Cdx2, a homeodomain protein involved in regulating intestinal development and differentiation. METHODS Nuclear protein bound to the lactase gene cis element, CE-LPH1, was analyzed by electrophoretic mobility shift assays and supershifts with Cdx2 antibody. Lactase promoter activities were assayed in cells transfected with luciferase reporter constructs and a Cdx2 expression construct. RESULTS Electrophoretic mobility shift assay with CE-LPH1 yields a specific DNA/protein complex that requires the caudal-related protein binding site, TTTAC. The complex is recognized by Cdx2 antibody and is more abundant in differentiated enterocytes. A Cdx2 expression construct is able to activate transcription driven by the wild-type, but not a mutated, promoter and results in increased endogenous lactase messenger RNA. CONCLUSIONS The homeodomain protein Cdx2 interacts with the lactase promoter and is capable of activating transcription of the endogenous gene. In contrast to a previous report, Cdx2 interaction with the lactase promoter correlates with enterocyte differentiation. These conclusions are consistent with the role of Cdx2 in regulating intestinal cell differentiation.
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Affiliation(s)
- R Fang
- Department of Pediatrics, Stanford University Medical Center, Stanford, California 94305, USA
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Xu F, Li H, Jin T. Cell type-specific autoregulation of the Caudal-related homeobox gene Cdx-2/3. J Biol Chem 1999; 274:34310-6. [PMID: 10567407 DOI: 10.1074/jbc.274.48.34310] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The caudal-related homeobox gene Cdx-2/3 is a critical "master" control gene in embryogenesis. Mice heterozygous for a null mutation in Cdx-2/3 exhibit multiple malfunctions including tail abnormalities, stunted growth, a homeotic shift in vertebrae, and the development of multiple intestinal adenomatous polyps, indicating that Cdx-2/3 is haplo-insufficient. In vitro studies have identified more than a half-dozen downstream target genes expressed in pancreatic and intestinal cells for this transcription factor. We have examined the transcriptional properties of the mouse Cdx-2/3 promoter. This promoter could be autoregulated in pancreatic and intestinal cells that express endogenous Cdx-2/3. In contrast, Cdx-2/3 transfection represses the Cdx-2/3 promoter in fibroblasts, which do not express endogenous Cdx-2/3. Since Cdx-2/3 activates proglucagon gene promoter in both pancreatic and intestinal cells and in fibroblasts, we suggest that some, yet to be identified, cell type-specific components are required for activating selected target gene promoters of Cdx-2/3, including the Cdx-2/3 promoter itself. Cdx-2/3 binds to the TATA box and another AT-rich motif, designated as DBS, within an evolutionarily conserved proximal element of the Cdx-2/3 promoter. The DBS motif is critical for the autoregulation, whereas the TATA box may act as an attenuating element for the autoregulatory loop. Finally, overexpression of Cdx-2/3 in a pancreatic cell line activated the expression of the endogenous Cdx-2/3. Taken together, our results indicate that the dose-dependent phenotype of Cdx-2/3 expression on its downstream targets in vivo could be regulated initially via a transcriptional network involving cell type-specific autoregulation of the Cdx-2/3 promoter.
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Affiliation(s)
- F Xu
- Oncology Research Laboratory, The Toronto Hospital, University of Toronto, Toronto, Ontario M5G 2M1, Canada
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