Regulation of duodenal specific expression of the human adenosine deaminase gene

Blimp1 regulates the transition of neonatal to adult intestinal epithelium

In many mammalian species, the intestinal epithelium undergoes major changes that allow a dietary transition from mother's milk to the adult diet at the end of the suckling period. These complex developmental changes are the result of a genetic programme intrinsic to the gut tube, but its regulators have not been identified. Here we show that transcriptional repressor B lymphocyte-induced maturation protein 1 (Blimp1) is highly expressed in the developing and postnatal intestinal epithelium until the suckling to weaning transition. Intestine-specific deletion of Blimp1 results in growth retardation and excessive neonatal mortality. Mutant mice lack all of the typical epithelial features of the suckling period and are born with features of an adult-like intestine. We conclude that the suckling to weaning transition is regulated by a single transcriptional repressor that delays epithelial maturation.

Onecut-2 knockout mice fail to thrive during early postnatal period and have altered patterns of gene expression in small intestine

Ablation of the mouse genes for Onecut-2 and Onecut-3 was reported previously, but characterization of the resulting knockout mice was focused on in utero development, principally embryonic development of liver and pancreas. Here we examined postnatal development of these Onecut knockout mice, especially the critical period before weaning. Onecut-3 knockout mice develop normally during this period. However, Onecut-2 knockout mice fail to thrive, lagging behind their littermates in size and weight. By postnatal day (d)19, they are consistently 25-30% smaller. Onecut-2 knockout mice also have a much higher level of mortality before weaning, with only approximately 70% survival. Interestingly, Onecut-2 knockout mice that are heterozygous for the Onecut-3 knockout allele are diminished even further in their ability to thrive. They are approximately 50-60% as large as their normal-sized littermates at d19, and less than half of these mice survive to weaning. As reported previously, the Onecut-2/Onecut-3 double knockout is a perinatal lethal. Microarray technology was used to determine the effect of Onecut-2 ablation on gene expression in duodenum, whose epithelium has among the highest levels of Onecut-2. A subset of intestinally expressed genes showed dramatically altered patterns of expression. Many of these genes encode proteins associated with the epithelial membrane, including many involved in transport and metabolism. Previously, we reported that Onecut-2 was critical to temporal regulation of the adenosine deaminase gene in duodenum. Many of the genes with altered patterns of expression in Onecut-2 knockout mouse duodenum displayed changes in the timing of gene expression.

THE EXTRACELLULAR CARDIAC PURINE METABOLOME IN SEPSIS

The total cardiac purine metabolome includes all of the adenine and guanine nucleoside and nucleosides and related molecules involved throughout the intracellular and extracellular compartments and various cell types in the heart. In considering purines as molecules involved in autocrine and paracrine communication, effective interstitial concentrations of the nucleoside adenosine, or purine metabolites, are of greatest interest. These molecules arise from the complex interactions between cardiac-specific cell types, including fibroblasts and myocytes, and noncardiac cells, such as tissue-resident macrophages and other immune cells that have vascular access. In the interstitial environment, adenosine can regulate vascular resistance, contractile function, and immunochemical interactions. The breakdown of purines can produce reactive oxygen species that also influence autocrine and paracrine interactions. A central enzyme in this paradigm, adenosine deaminase, is a pivotal molecule in regulating the balance between pro-inflammatory and anti-inflammatory signaling cascades. A new role for adenosine deaminase as an allosteric regulator of relevant membrane proteins has yet to be explored in the heart.

Temporal regulation of enhancer function in intestinal epithelium: a role for Onecut factors

An intestine-specific gene regulatory region was previously identified near the second exon of the human adenosine deaminase (ADA) gene. In mammalian intestine, ADA is expressed at high levels only along the villi of the duodenal epithelium, principally if not exclusively in enterocytes. Within the ADA intestinal regulatory region, a potent duodenum-specific enhancer was identified that controls this pattern of expression. This enhancer has been shown to rely on PDX-1, GATA factors, and Cdx factors for its function. Upstream of the enhancer, a separate temporal regulatory region was identified that has no independent enhancer capability but controls the timing of enhancer activation. DNase I footprinting and electrophoretic mobility shift assays were used to begin to characterize temporal region function at the molecular level. In this manner, binding sites for the Onecut (OC) family of factors, YY1, and NFI family members were identified. Identification of the OC site was especially interesting, because almost nothing is known about the function of OC factors in intestine. In transgenic mice, mutation of the OC site to ablate binding resulted in a delay of 2-3 weeks in enhancer activation in the developing postnatal intestine, a result very similar to that observed previously when the entire temporal region was deleted. In mammals, the OC family is comprised of OC-1/HNF-6, OC-2, and OC-3. An examination of intestinal expression patterns showed that all three OC factors are expressed at detectable levels in adult mouse duodenum, with OC-2 predominant. In postnatal day 2 mice only OC-2 and OC-3 were detected in intestine, with OC-2 again predominant.

Cdx binding determines the timing of enhancer activation in postnatal duodenum

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.

Adenosine Deaminase Deficiency: Metabolic Basis of Immune Deficiency and Pulmonary Inflammation

Genetic deficiencies in the purine catabolic enzyme adenosine deaminase (ADA) in humans results primarily in a severe lymphopenia and immunodeficiency that can lead to the death of affected individuals early in life. The metabolic basis of the immunodeficiency is likely related to the sensitivity of lymphocytes to the accumulation of the ADA substrates adenosine and 2'-deoxyadenosine. Investigations using ADA-deficient mice have provided compelling evidence to support the hypothesis that T and B cells are sensitive to increased concentrations of 2'-deoxyadenosine that kill cells through mechanisms that involve the accumulation of dATP and the induction of apoptosis. In addition to effects on the developing immune system, ADA-deficient humans exhibit phenotypes in other physiological systems including the renal, neural, skeletal, and pulmonary systems. ADA-deficient mice develop similar abnormalities that are dependent on the accumulation of adenosine and 2'-deoxyadenosine. Detailed analysis of the pulmonary insufficiency seen in ADA-deficient mice suggests that the accumulation of adenosine in the lung can directly access cellular signaling pathways that lead to the development and exacerbation of chronic lung disease. The ability of adenosine to regulate aspects of chronic lung disease is likely mediated by specific interactions with adenosine receptor subtypes on key regulatory cells. Thus, the examination of ADA deficiency has identified the importance of purinergic signaling during lymphoid development and in the regulation of aspects of chronic lung disease.

Macrophages are a source of extracellular adenosine deaminase-2 during inflammatory responses

Serum activity of the adenosine deaminase (ADA) isozyme, ADA2, has been reported to be elevated during various disease states. Macrophages have been suggested as the cellular source of extracellular ADA activity because they are one of the only cell types in which intracellular ADA2 activity has been measured, but extracellular secretion has never been demonstrated. Rat primary peritoneal macrophages (PPMs) and peripheral blood monocytes (PBMs) were harvested and incubated for 18 h in RPMI supplemented with horse serum. PPM and PBM lysates were assayed for intracellular ADA activity (ammonia production). In vitro and in vivo extracellular ADA activities were measured in media and rat serum, respectively. Activity of ADA1 was confirmed by selective inhibition with erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA). ADA2 activity was inhibited by 2'-deoxycoformcin only, and was increased at a low pH (6.5). Activity of both ADA isozymes was found in PPMs and PBMs, and their media. In a separate group of rats, peritonitis was induced by ip insertion of 400 mg/kg caecal slurry. PPMs were harvested 24 h later and incubated for 18 h. In PPMs from rats with peritonitis both isozymes were elevated by a similar proportion. In contrast, media from these PPMs had a lower ADA1 and a higher ADA2 activity compared to PPMs from nonseptic rats. This resulted in a greater proportion of ADA2 in media. The isozyme proportions in serum from septic rats more closely resembled that of the PPM media. The response of PBM was small relative to that of PPM. These results suggest that macrophages are a significant source of extracellular ADA isozymes, the activity of which increases during an inflammatory response. Because extracellular isozymes profiles differ from cellular concentrations, the data also suggest differential release of each isozyme from PPMs.

Adenosine deaminase, a key enzyme in DNA precursors control, is a new p73 target

The discovery of the p73 and p63 genes, homologous to p53 tumor suppressor has uncovered a family of transcription factors and widened the scenario of cell cycle control and apoptosis. We have identified a putative p53-responsive element in the human adenosine deaminase (ADA) gene, an important enzyme involved in nucleotide metabolism, the deficit of which causes the inhibition of DNA synthesis and repair. Here, we demonstrate that the ectopic expression of p73 isoforms leads to the ADA gene upregulation, showing for the first time a correlation between p73 and ADA. We found that p73 promotes ADA gene expression following a dNTP unbalance generated by ADA enzyme deficiency and 2'deoxyadenosine accumulation. The abrogation of p73 transcriptional activity by the specific dominant-negative p73DD abolishes ADA induction. By contrast, the ADA gene does not appear to be a functional p53 target in the physiological conditions we tested. On the whole, our results contribute to the emerging picture that p73 could play a different role from p53 in normal growth and development by inducing alternative target genes, which are not shared by p53.

High-level activation by a duodenum-specific enhancer requires functional GATA binding sites

The purine metabolic gene adenosine deaminase (ADA) is expressed at high levels in a well-defined spatiotemporal pattern in the villous epithelium of proximal small intestine. A duodenum-specific enhancer module responsible for this expression pattern has been identified in the second intron of the human ADA gene. It has previously been shown that binding of the factor PDX-1 is essential for function of this enhancer. The studies presented here examine the proposed roles of GATA factors in the enhancer. Site-directed mutagenesis of the enhancer's GATA binding sites crippled enhancer function in 10 lines of transgenic mice, with 9 of the lines demonstrating <1% of normal activity. Detailed studies along the longitudinal axis of mouse small intestine indicate that GATA-4 and GATA-5 mRNA levels display a reciprocal pattern, with low levels of GATA-6 throughout. Interestingly, gel shift studies with duodenal nuclear extracts showed binding only by GATA-4.

Cis elements of the villin gene control expression in restricted domains of the vertical (crypt) and horizontal (duodenum, cecum) axes of the intestine

Villin, an actin bundling protein found in the apical brush border of absorptive tissues, is one of the first structural genes to be transcriptionally activated in the embryonic intestinal endoderm. In the adult, villin is broadly expressed in every cell of the intestinal epithelium on both the vertical axis (crypt to villus tip) and the horizontal axis (duodenum through colon) of the intestine. Here, we document that a 12.4-kilobase region of the mouse villin gene drives high level expression of two different reporter genes (LacZ and Cre recombinase) within the entire intestinal epithelium of transgenic mice. Deletion of a portion of this transgene results in reduction of beta-galactosidase activity in restricted domains of the small intestine (duodenum) and large intestine (cecum). In addition, expression is reduced in the crypt compartment throughout the intestine. Thus, the global expression pattern of villin in the intestine is apparently the consequence of an amalgam of distinct and individual domain-specific control processes. That is, expression of villin in the duodenum and cecum requires different regulatory sequences than the rest of the intestine, and the expression of villin in crypts is regulated by different circuitry than expression of villin on villus tips.

Novel genes and functional relationships in the adult mouse gastrointestinal tract identified by microarray analysis

BACKGROUND & AIMS

A genome-level understanding of the molecular basis of segmental gene expression along the anterior-posterior (A-P) axis of the mammalian gastrointestinal (GI) tract is lacking. We hypothesized that functional patterning along the A-P axis of the GI tract could be defined at the molecular level by analyzing expression profiles of large numbers of genes.

METHODS

Incyte GEM1 microarrays containing 8638 complementary DNAs (cDNAs) were used to define expression profiles in adult mouse stomach, duodenum, jejunum, ileum, cecum, proximal colon, and distal colon. Highly expressed cDNAs were classified based on segmental expression patterns and protein function.

RESULTS

571 cDNAs were expressed 2-fold higher than reference in at least 1 GI tissue. Most of these genes displayed sharp segmental expression boundaries, the majority of which were at anatomically defined locations. Boundaries were particularly striking for genes encoding proteins that function in intermediary metabolism, transport, and cell-cell communication. Genes with distinctive expression profiles were compared with mouse and human genomic sequence for promoter analysis and gene discovery.

CONCLUSIONS

The anatomically defined organs of the GI tract (stomach, small intestine, colon) can be distinguished based on a genome-level analysis of gene expression profiles. However, distinctions between various regions of the small intestine and colon are much less striking. We have identified novel genes not previously known to be expressed in the adult GI tract. Identification of genes coordinately regulated along the A-P axis provides a basis for new insights and gene discovery relevant to GI development, differentiation, function, and disease.

Human apolipoprotein B gene intestinal control region

Recently, we reported that a 315 bp enhancer, located over 55 kilobases (kb) upstream of the transcriptional start site of the human apolipoprotein B (apoB) gene, was sufficient to direct high-level expression of human apoB transgenes in mice. In this report, we expand our analysis of the distant apoB intestinal control region (ICR), by examining the function of segments in the vicinity of the 315 bp intestinal enhancer (315 IE). DNaseI hypersensitivity (DH) studies of a 4.8 kb segment from the ICR revealed three new DH sites, in addition to the previously described DH1 region present within the 315 IE. DH2 mapped to a 485 bp segment (485 IE) immediately upstream of the 315 IE that exhibited strong intestinal enhancer activity in transient transfection experiments with intestine-derived CaCo-2 cells. Within the DH2 region, an HNF-4/ARP-1 binding site was demonstrated by gel retardation experiments. A 1.8 kb segment incorporating the 485 IE was capable of driving expression of human apoB transgenes in the intestines of mice. Additionally, a third component of the apoB ICR was found about 1.2 kb downstream of the 315 IE, within a 1031 bp segment (1031 IE) that also harbored two DH sites, DH3 and DH4. This segment did not display enhancer activity but was capable of driving transgene expression in the intestine. The three components of the ICR displayed a similar pattern of apoB mRNA expression along the horizontal axis of the intestine. The previously characterized in vivo liver-specific elements of the apoB gene, namely, the second intron enhancer and the 5' upstream liver enhancer, did not play a role in intestinal expression of apoB transgenes in mice.

Pdx-1 is required for activation in vivo from a duodenum-specific enhancer

The purine metabolic gene adenosine deaminase (ADA) is expressed along a defined spatiotemporal pattern in the developing mammalian small intestine, where high-level expression is limited to the villous epithelium of the duodenum. This activation is observed in rodents as the intestine completes the final maturation resulting in adult crypt-villus structures at 2-3 weeks postpartum. A regulatory module responsible for this pattern of expression has been identified in the second intron of the human ADA gene. Of the multiple duodenal proteins that can interact with this small duodenal enhancer region, the studies contained in this work describe the identification of five of these proteins as the dispersed homeobox protein PDX-1. This transcription factor exhibits a profile of expression in the small intestine similar to that observed for ADA, making it an ideal candidate factor for the duodenum-specific ADA enhancer. Loss of PDX-1 binding, via a PDX-1 mutated enhancer transgenic construction, resulted in complete loss of high-level activation in the duodenum, demonstrating the absolute requirement for this factor in vivo. However, co-transfection experiments suggest that other proteins that bind the enhancer are also required for enhancer function because PDX-1 alone was incapable of significant transactivation.

Differential gene expression in the small intestines of wildtype and W/W(V) mice

Much of the evidence demonstrating the role of interstitial cells of Cajal (ICC) in pacemaking and neurotransmission in the gastrointestinal tract comes from studies of W/W(V) mice. These animals have few pacemaker ICC in the small bowel due to reduced functional Kit protein. We examined gene expression in the small intestines of wildtype and W/W(V) mice. RNA expression in the jejunums of wildtype and W/W(V) mutants was studied using a differential gene expression

METHOD

Seven known genes were differentially expressed in wildtype and W/W(V) mice. COX7B (cytochrome c oxidase, subunit VIIb) and SORCIN (encoding multidrug-resistance complex, class 4) were suppressed in both fed and fasted W/W(V) mice. Expression of another five genes was increased in W/W(V) mice: ADA (adenosine deaminase), MDH1 (malate dehydrogenase), RPL-8 (ribosomal protein L8), SPTB2 (spectrin, nonerythroid, beta subunit), and p6-5 (encoding phosphorylcholine [PC] T-cell suppressor factor [TsF]). Differential expression was the same in fasted and fed animals, suggesting that the differences were independent of the dietetic state. We conclude that several genes are differentially expressed in the small intestines of W/W(V) mice where the major lesion is loss of pacemaker ICC. Differential gene display may help develop a molecular profile of motility disorders in which ICC are lost.

A duodenum-specific enhancer regulates expression along three axes in the small intestine

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.

Regulation of forestomach-specific expression of the murine adenosine deaminase gene

The maturation of stratified squamous epithelium of the upper gastrointestinal tract is a highly ordered process of development and differentiation. Information on the molecular basis of this process is, however, limited. Here we report the identification of the first murine forestomach regulatory element using the murine adenosine deaminase (Ada) gene as a model. In the adult mouse, Ada is highly expressed in the terminally differentiated epithelial layer of upper gastrointestinal tract tissues. The data reported here represent the identification and detailed analysis of a 1. 1-kilobase (kb) sequence located 3.4-kb upstream of the transcription initiation site of the murine Ada gene, which is sufficient to target cat reporter gene expression to the forestomach in transgenic mice. This 1.1-kb fragment is capable of directing cat reporter gene expression mainly to the forestomach of transgenic mice, with a level comparable to the endogenous Ada gene. This expression is localized to the appropriate cell types, confers copy number dependence, and shows the same developmental regulation. Mutational analysis revealed the functional importance of multiple transcription factor-binding sites.

Estrogen induces adenosine deaminase gene expression in MCF-7 human breast cancer cells: role of estrogen receptor-Sp1 interactions

Adenosine deaminase (ADA) gene expression is induced by 17beta-estradiol (E2) in MCF-7 human breast cancer cells, whereas the antiestrogens 4'-hydroxytamoxifen and ICI 182,780 exhibit partial estrogen receptor (ER) agonist/antagonist and antagonist activities, respectively. Previous studies have shown that the -211 to +11 region of the ADA gene promoter contains six GC-rich sites (I-VI) that bind Sp1 protein, and these elements are required for high basal expression. In transient transfection studies with pADA211, which contains the -211 to +11 ADA gene promoter linked to a bacterial chloramphenicol acetyl transferase (CAT) reporter gene, E2 and tamoxifen (but not ICI 182,780) induced CAT activity. Ligand-induced transactivation was observed only in cells cotransfected with expression plasmids for wild-type ER or HE11, which does not contain the DNA-binding domain of the ER. Cotransfection with HE15 and HE19, which contain the DNA-binding domain and activation function-1 (AF-1) and AF-2 of the ER, respectively, did not result in E2-induced activity. Subsequent deletion analysis of the ADA gene promoter showed that Sp1 binding site IV (-79 to -73) was primarily responsible for hormone responsiveness. ER activation of ADA gene expression is another example of an E2-induced gene that is dependent on ER/Sp1 interactions with a site-specific GC-rich motif.