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Yoon G, Davidson LA, Goldsby JS, Mullens DA, Ivanov I, Donovan SM, Chapkin RS. Exfoliated epithelial cell transcriptome reflects both small and large intestinal cell signatures in piglets. Am J Physiol Gastrointest Liver Physiol 2021; 321:G41-G51. [PMID: 33949197 PMCID: PMC8321797 DOI: 10.1152/ajpgi.00017.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Assessing intestinal development and host-microbe interactions in healthy human infants requires noninvasive approaches. We have shown that the transcriptome of exfoliated epithelial cells in feces can differentiate breast-fed and formula-fed infants and term and preterm infants. However, it is not fully understood which regions of the intestine that the exfoliated cells represent. Herein, the transcriptional profiles of exfoliated cells with that of the ileal and colonic mucosa were compared. We hypothesized that exfoliated cells in the distal colon would reflect mucosal signatures of more proximal regions of the gut. Two-day-old piglets (n = 8) were fed formulas for 20 days. Luminal contents and mucosa were collected from ileum (IL), ascending colon (AC), and descending (DC) colon, and mRNA was extracted and sequenced. On average, ∼13,000 genes were mapped in mucosal tissues and ∼10,000 in luminal contents. The intersection of detected genes between three mucosa regions and DC exfoliome indicated an approximately 99% overlap. On average, 49% of the genes in IL, AC, and DC mucosa were present in the AC and DC exfoliome. Genes expressed predominantly in specific anatomic sites (stomach, pancreas, small intestine, colon) were detectable in exfoliated cells. In addition, gene markers for all intestinal epithelial cell types were expressed in the exfoliome representing a diverse array of cell types arising from both the small and large intestine. Genes were mapped to nutrient absorption and transport and immune function. Thus, the exfoliome represents a robust reservoir of information in which to assess intestinal development and responses to dietary interventions.NEW & NOTEWORTHY The transcriptome of exfoliated epithelial cells in stool contain gene signatures from both small and large intestinal mucosa affording a noninvasive approach to assess gut health and function.
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Affiliation(s)
- Grace Yoon
- 1Department of Statistics, Texas A&M University, College Station, Texas
| | - Laurie A. Davidson
- 2Department of Nutrition, Texas A&M University, College Station Texas,3Program in Integrative Nutrition & Complex Diseases, Texas A&M University, College Station, Texas
| | - Jennifer S. Goldsby
- 2Department of Nutrition, Texas A&M University, College Station Texas,3Program in Integrative Nutrition & Complex Diseases, Texas A&M University, College Station, Texas
| | - Destiny A. Mullens
- 3Program in Integrative Nutrition & Complex Diseases, Texas A&M University, College Station, Texas,4Department of Veterinary Pathobiology, Texas A&M University, College Station, Texas
| | - Ivan Ivanov
- 4Department of Veterinary Pathobiology, Texas A&M University, College Station, Texas
| | - Sharon M. Donovan
- 5Department of Food Science and Human Nutrition, University of Illinois, Urbana-Champaign, Illinois
| | - Robert S. Chapkin
- 2Department of Nutrition, Texas A&M University, College Station Texas,3Program in Integrative Nutrition & Complex Diseases, Texas A&M University, College Station, Texas
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2
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Heuberger J, Hill U, Förster S, Zimmermann K, Malchin V, Kühl AA, Stein U, Vieth M, Birchmeier W, Leutz A. A C/EBPα-Wnt connection in gut homeostasis and carcinogenesis. Life Sci Alliance 2018; 2:e201800173. [PMID: 30599048 PMCID: PMC6306571 DOI: 10.26508/lsa.201800173] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 12/12/2022] Open
Abstract
This research reveals an antagonism between C/EBPα expression and activated Wnt signaling in the human and mouse gut and suggests a tumor suppressor function of C/EBPα in human and murine intestinal cancer. We explored the connection between C/EBPα (CCAAT/enhancer-binding protein α) and Wnt signaling in gut homeostasis and carcinogenesis. C/EBPα was expressed in human and murine intestinal epithelia in the transit-amplifying region of the crypts and was absent in intestinal stem cells and Paneth cells with activated Wnt signaling. In human colorectal cancer and murine APCMin/+ polyps, C/EBPα was absent in the nuclear β-catenin–positive tumor cells. In chemically induced intestinal carcinogenesis, C/EBPα KO in murine gut epithelia increased tumor volume. C/EBPα deletion extended the S-phase cell zone in intestinal organoids and activated typical proliferation gene expression signatures, including that of Wnt target genes. Genetic activation of β-catenin in organoids attenuated C/EBPα expression, and ectopic C/EBPα expression in HCT116 cells abrogated proliferation. C/EBPα expression accompanied differentiation of the colon cancer cell line Caco-2, whereas β-catenin stabilization suppressed C/EBPα. These data suggest homeostatic and oncogenic suppressor functions of C/EBPα in the gut by restricting Wnt signaling.
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Affiliation(s)
| | - Undine Hill
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Susann Förster
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | | | | | - Anja A Kühl
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Ulrike Stein
- Experimental and Clinical Research Center, Charite-Universitätsmedizin Berlin and Max Delbrück Center for Molecular Medicine, Berlin, Germany.,German Cancer Consortium (Deutsches Konsortium für Translationale Krebsforschung), Heidelberg, Germany
| | - Michael Vieth
- Klinikum Bayreuth, Institute for Pathology, Bayreuth, Germany
| | | | - Achim Leutz
- Max Delbrück Center for Molecular Medicine, Berlin, Germany.,Institute of Biology, Humboldt University of Berlin, Berlin, Germany
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3
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Expression and regulation of C/EBPα in normal myelopoiesis and in malignant transformation. Blood 2017; 129:2083-2091. [PMID: 28179278 DOI: 10.1182/blood-2016-09-687822] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 10/14/2016] [Indexed: 12/13/2022] Open
Abstract
One of the most studied transcription factors in hematopoiesis is the leucine zipper CCAAT-enhancer binding protein α (C/EBPα), which is mainly involved in cell fate decisions for myeloid differentiation. Its involvement in acute myeloid leukemia (AML) is diverse, with patients frequently exhibiting mutations, deregulation of gene expression, or alterations in the function of C/EBPα. In this review, we emphasize the importance of C/EBPα for neutrophil maturation, its role in myeloid priming of hematopoietic stem and progenitor cells, and its indispensable requirement for AML development. We discuss that mutations in the open reading frame of CEBPA lead to an altered C/EBPα function, affecting the expression of downstream genes and consequently deregulating myelopoiesis. The emerging transcriptional mechanisms of CEBPA are discussed based on recent studies. Novel insights on how these mechanisms may be deregulated by oncoproteins or mutations/variants in CEBPA enhancers are suggested in principal to reveal novel mechanisms of how CEBPA is deregulated at the transcriptional level.
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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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5
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Gartner H, Graul MC, Oesterreicher TJ, Finegold MJ, Henning SJ. Development of the fetal intestine in mice lacking the glucocorticoid receptor (GR). J Cell Physiol 2003; 194:80-7. [PMID: 12447992 DOI: 10.1002/jcp.10189] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
During rodent development there are two surges of circulating corticosterone: one just prior to birth and then one in the third postnatal week. Prior studies have shown that the latter controls the rate of intestinal development in the postnatal period. To date, a role for the earlier surge in the prenatal phase of intestinal development has not been investigated. We hypothesized that the late fetal surge of circulating corticosterone is involved in both morphologic and functional maturation of the intestinal epithelium, and thus that such maturation would be delayed if glucocorticoid action was abrogated. The hypothesis was tested by studying intestinal development in mice lacking a functional glucocorticoid receptor (GR). After GR+/- mice were bred onto a C57Bl/6 background, heterozygote matings yielded the expected ratios of -/-, +/-, and +/+ offspring. Analysis of GR mRNA in intestines of +/+ and -/- fetuses confirmed expression in wild-type mice but not in the GR-null mice. Intestinal histology of GR+/+ and -/- littermates at E13.5, E15.5, and E18.5 showed no effect of GR genotype on morphologic development. Further studies at E18.5 showed that GR-/- mice have normal functional maturation of the intestinal epithelium as assessed by: lactase activity in the enterocyte lineage, normal numbers of goblet and enteroendocrine cells, and normal numbers of proliferating cells in the intestinal crypts. Neither the minerolocorticoid receptor (MR) nor the pregnane X receptor (PXR) showed compensatory up-regulation in GR-/- mice. We conclude that, in contrast to our original hypothesis, the rodent intestine passes through a phase of glucocorticoid independence (late fetal) prior to becoming responsive to glucocorticoids in the postnatal period. These findings have implications for the clinical use of corticosteroids to enhance intestinal maturation in preterm infants.
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MESH Headings
- Animals
- Cell Differentiation/genetics
- Cell Lineage/genetics
- Corticosterone/metabolism
- Female
- Fetus
- Genotype
- Goblet Cells/cytology
- Goblet Cells/metabolism
- Intestinal Mucosa/cytology
- Intestinal Mucosa/embryology
- Intestinal Mucosa/metabolism
- Intestine, Small/cytology
- Intestine, Small/embryology
- Intestine, Small/metabolism
- Ki-67 Antigen/metabolism
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mutation/genetics
- Paneth Cells/cytology
- Paneth Cells/metabolism
- Pregnane X Receptor
- RNA, Messenger/metabolism
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Glucocorticoid/deficiency
- Receptors, Glucocorticoid/genetics
- Receptors, Mineralocorticoid/genetics
- Receptors, Steroid/genetics
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Affiliation(s)
- Hans Gartner
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA
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6
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Solorzano-Vargas RS, Wang J, Jiang L, Tsai HV, Ontiveros LO, Vazir MA, Aguilera RJ, Martín MG. Multiple transcription factors in 5'-flanking region of human polymeric Ig receptor control its basal expression. Am J Physiol Gastrointest Liver Physiol 2002; 283:G415-25. [PMID: 12121890 DOI: 10.1152/ajpgi.00420.2001] [Citation(s) in RCA: 11] [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
The polymeric Ig receptor (pIgR) is a critical component of the mucosal immune system and is expressed in largest amounts in the small intestine. In this study, we describe the initial characterization of the core promoter region of this gene. Expression of chimeric promoter-reporter constructs was supported in Caco-2 and HT-29 cells, and DNase I footprint analysis revealed a large protein complex within the core promoter region. Site-directed mutagenesis experiments determined that elements within this region serve to either augment or repress basal activity of the human pIgR promoter. Band shift assays of overlapping oligonucleotides within the core promoter identified eight distinct complexes; the abundance of most complexes was enhanced in post-confluent cells. In summary, we report the characterization of the human pIgR promoter and the essential role that eight different nuclear complexes have in controlling basal expression of this gene in Caco-2 cells.
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7
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Wang H, Qu X, De Plaen IG, Hsueh W. Platelet-activating factor and endotoxin activate CCAAT/enhancer binding protein in rat small intestine. Br J Pharmacol 2001; 133:713-21. [PMID: 11429396 PMCID: PMC1572822 DOI: 10.1038/sj.bjp.0704102] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The transcription factor family CCAAT/enhancer binding proteins (C/EBP) is involved in inflammation via the regulation of the gene expression of various pro-inflammatory cytokines and proteins. PAF and endotoxin (lipopolysaccharide, LPS) are known agents causing intestinal inflammation and injury. In this study, we examined the binding activity of C/EBP isoforms in rat small intestine in response to PAF (1.5 microg kg(-1), i.v.) or LPS (5 mg kg(-1), i.v.). We found that C/EBP is constitutively active in normal small intestine, mainly as C/EBP-alpha and beta (C/EBP-beta>alpha). Both C/EBP-alpha and beta are localized in the intestinal epithelial cells: C/EBP-alpha mainly in the crypts, and C/EBP-beta in both villi and crypts, as well as in some lamina propria cells. Only minute amounts of C/EBP-delta were found. PAF rapidly upregulates the binding activity of C/EBP-alpha and beta within 30 min. The increase in C/EBP-alpha is prominent in the crypt cells, whereas the change of C/EBP-beta is more widespread. LPS also increases the binding activity of C/EBP-alpha and beta, and the response is slower than PAF. PAF synergizes with LPS to markedly activate all three subunits. The increase in C/EBP-alpha is transient, whereas the other two have a sustained elevation until 120 min. After challenge with PAF (but not LPS), small amounts of nuclear factor -kappaB (NF-kappaB) p50 and p65 subunits are found in the C/EBP-DNA binding complex, indicating cross-dimerization of the two transcription families. Pretreatment of rats with pyrrolidine dithiocarbamate (PDTC) suppresses LPS-, but not PAF-, induced NF-kappaB and C/EBP binding activity, and significantly increases the C/EBP-delta subunit in LPS- or PAF-induced C/EBP complex. These results suggest that PAF and LPS activate intestinal C/EBP in vivo, probably via different pathways.
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Affiliation(s)
- Hao Wang
- Department of Pathology, Children's Memorial Medical Center, Northwestern University Medical School, Chicago, Illinois, IL 60614, U.S.A
| | - Xiaowu Qu
- Department of Pathology, Children's Memorial Medical Center, Northwestern University Medical School, Chicago, Illinois, IL 60614, U.S.A
| | - Isabelle G De Plaen
- Department of Pediatrics, Children's Memorial Medical Center, Northwestern University Medical School, Chicago, Illinois, IL 60614, U.S.A
| | - Wei Hsueh
- Department of Pathology, Children's Memorial Medical Center, Northwestern University Medical School, Chicago, Illinois, IL 60614, U.S.A
- Author for correspondence:
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8
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Antes TJ, Levy-Wilson B. HNF-3 beta, C/EBP beta, and HNF-4 act in synergy to enhance transcription of the human apolipoprotein B gene in intestinal cells. DNA Cell Biol 2001; 20:67-74. [PMID: 11244563 DOI: 10.1089/104454901750070265] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Recently, we identified a 315-bp intestinal enhancer (IE), localized over 55 kb upstream from the transcriptional start of the human apolipoprotein B (apoB) gene, that confers expression of human apoB transgenes in the intestines of mice. Four functional binding sites for the intestine-enriched transcription factors hepatocyte nuclear factor (HNF)-3beta, CAAT enhancer binding protein (C/EBP)beta, and HNF-4 were demonstrated within the 315-bp IE. In this report, we extend these earlier studies and examine the relative contributions of these three transcription factors to the activity of the enhancer as well as their mechanism of interaction with one another. Cotransfection experiments with the expression vectors for HNF-3beta, C/EBPbeta, and HNF-4 revealed that HNF-3beta bound to Site 1, C/EBPbeta bound to Site 2, and HNF-4 bound to Site 3 within the 315-bp IE and that the sites act synergistically to enhance intestinal expression of apoB. Each one of these four binding sites was mutated, and mutant constructs were transfected into intestine-derived CaCo-2 cells to evaluate the role of each of these binding sites in enhancer activity. The results of the mutagenesis experiments confirmed that the HNF-3beta and HNF-4 sites are most important for the enhancer activity, followed by C/EBPbeta Site 2. All three factors bound to Sites 1, 2, and 3 must act synergistically for optimal activity of the apoB IE.
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Affiliation(s)
- T J Antes
- Research Institute, Palo Alto Medical Foundation, and Department of Medicine, Stanford University, Palo Alto, California, USA
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Antes TJ, Goodart SA, Huynh C, Sullivan M, Young SG, Levy-Wilson B. Identification and characterization of a 315-base pair enhancer, located more than 55 kilobases 5' of the apolipoprotein B gene, that confers expression in the intestine. J Biol Chem 2000; 275:26637-48. [PMID: 10859308 DOI: 10.1074/jbc.m003025200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We recently reported that an 8-kilobase (kb) region, spanning from -54 to -62 kb 5' of the human apolipoprotein B (apoB) gene, contains intestine-specific regulatory elements that control apoB expression in the intestines of transgenic mice. In this study, we further localized the apoB intestinal control region to a 3-kb segment (-54 to -57 kb). DNaseI hypersensitivity studies uncovered a prominent DNaseI hypersensitivity site, located within a 315-base pair (bp) fragment at the 5'-end of the 3-kb segment, in transcriptionally active CaCo-2 cells but not in transcriptionally inactive HeLa cells. Transient transfection experiments with CaCo-2 and HepG2 cells indicated that the 315-bp fragment contained an intestine-specific enhancer, and analysis of the DNA sequence revealed putative binding sites for the tissue-specific transcription factors hepatocyte nuclear factor 3beta, hepatocyte nuclear factor 4, and CAAT enhancer-binding protein beta. Binding of these factors to the 315-bp enhancer was demonstrated in gel retardation experiments. Transfection of deletion mutants of the 315-bp enhancer revealed the relative contributions of these transcription factors in the activity of the apoB intestinal enhancer. The corresponding segment of the mouse apoB gene (located -40 to -83 kb 5' of the structural gene) exhibited a high degree of sequence conservation in the binding sites for the key transcriptional activators and also exhibited enhancer activity in transient transfection assays with CaCo-2 cells. In transgenic mouse expression studies, the 315-bp enhancer conferred intestinal expression to human apoB transgenes.
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Affiliation(s)
- T J Antes
- Research Institute, Palo Alto Medical Foundation, Palo Alto, California 94301, USA
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Li TW, Wang J, Lam JT, Gutierrez EM, Solorzano-Vargus RS, Tsai HV, Martín MG. Transcriptional control of the murine polymeric IgA receptor promoter by glucocorticoids. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:G1425-34. [PMID: 10362646 DOI: 10.1152/ajpgi.1999.276.6.g1425] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Glucocorticoids have been implicated as an important regulator of intestinal epithelial cell ontogeny. The polymeric IgA receptor (pIgR) is expressed in the intestinal epithelial layer and is regulated by several mediators, including glucocorticoids. The mechanism of how corticosteroids alter the transcriptional regulation of pIgR expression has not been defined. In this study, we demonstrated that glucocorticoids upregulate steady-state pIgR mRNA levels in the proximal intestine of suckling rats and in the IEC-6 intestinal cell line. We performed functional analysis of the 5'-flanking region in the presence of glucocorticoids and its receptor using the intestinal cell line Caco-2. We screened 4.7 kb of the upstream region of the murine gene and identified the most potent steroid response element to reside between nt -215 and -163 relative to the start of transcription. Substitution mutation analysis of this region identified the location of the putative steroid response element to be between nt -195 and -176. In vitro DNase I footprint analysis using the recombinant glucocorticoid receptor DNA binding domain confirmed a single area of protection that spans the nt identified by mutagenesis analysis. Electrophoretic mobility shift assays of the putative element confirmed the binding of both recombinant and cell synthesized glucocorticoid receptor in a specific manner. In summary, we report the identification and characterization of the glucocorticoid-DNA response element located in the immediate 5'-upstream region of the murine pIgR gene.
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Affiliation(s)
- T W Li
- Department of Pediatrics, Division of Gastroenterology and Nutrition, University of California Los Angeles School of Medicine, Los Angeles, CA 90095-1752, USA
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Abstract
A combination of approaches has begun to elucidate the mechanisms of gastrointestinal development. This review describes progress over the last 20 years in understanding human gastrointestinal development, including data from both human and experimental animal studies that address molecular mechanisms. Rapid progress is being made in the identification of genes regulating gastrointestinal development. Genes directing initial formation of the endoderm as well as organ-specific patterning are beginning to be identified. Signaling pathways regulating the overall right-left asymmetry of the gastrointestinal tract and epithelial-mesenchymal interactions are being clarified. In searching for extrinsic developmental regulators, numerous candidate trophic factors have been proposed, but compelling evidence remains elusive. A critical gene that initiates pancreas development has been identified, as well as a number of genes regulating liver, stomach, and intestinal development. Mutations in genes affecting neural crest cell migration have been shown to give rise to Hirschsprung's disease. Considerable progress has been achieved in understanding specific phenomena, such as the transcription factors regulating expression of sucrase-isomaltase and fatty acid-binding protein. The challenge for the future is to integrate these data into a more complete understanding of the physiology of gastrointestinal development.
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Affiliation(s)
- R K Montgomery
- Division of Pediatric Gastroenterology and Nutrition, The Floating Hospital for Children at New England Medical Center, Boston, MA 02111-1533, USA
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