Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Retinoic acid (RA) receptors (RARs) are ligand-inducible transcription factors that bind to specific DNA sequences associated with the regulatory regions of RA-regulatable genes. Since RA has been implicated as an important factor both in normal development and in teratological studies, one would like to have a model system that detects the presence of activated receptors during development. We have constructed a recombinant reporter gene that has three copies of the RA response element (RARE) from the RAR beta-2 promoter 5' to the herpes simplex virus thymidine kinase promoter; this regulatory region is coupled to the bacterial beta-galactosidase reporter gene. This construct was RA inducible in transient transfection assays in F9 embryonal carcinoma cells. Transgenic embryos with this reporter gene construct exhibited restricted and reproducible patterns of beta-galactosidase activity during embryogenesis, beginning between gestational ages day 7.5 and 8.5. At day 8.5, beta-galactosidase activity was detected in the closed neurotube and somites. Day 8.5 embryos, from pregnant females fed RA 14 hr earlier, exhibited a greater intensity and distribution of beta-galactosidase activity. Similarly, at later stages of gestation, maternal RA exposure resulted in enhanced embryonic beta-galactosidase expression. This type of transgenic indicator mouse should be useful in detailing the role of activated RARs during embryonic development.
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PMID:Transgenic indicator mice for studying activated retinoic acid receptors during development. 131 86

Retinoic acid receptors (RARs) modulate gene expression following association with retinoic acid (RA). In transient transfection, an RAR alpha-beta-galactosidase fusion protein (RAR-LacZ) was able to transactivate expression in the absence of RA. When expressed in the ocular lens of transgenic mice, this constitutively active RAR-LacZ fusion gene resulted in founder and progeny animals that exhibited cataracts and microphthalmia, both being characteristics of retinoid-induced teratogenesis. The transgenic phenotypes indicate that retinoid teratogenesis can be mimicked by expression of a constitutively active RAR-LacZ fusion protein in retinoid-sensitive tissues.
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PMID:Transgenic mice expressing a constitutively active retinoic acid receptor in the lens exhibit ocular defects. 131 36

Retinoic acid (RA) is a signalling molecule important for pattern formation during development. There are three known types of nuclear receptors for RA in mammals, RAR-alpha, RAR-beta and RAR-gamma, which transduce the RA signal by inducing or repressing the transcription of target genes. Here we describe the developmental expression pattern of the mouse RAR-beta 2 promoter. Independent lines of transgenic animals expressing RAR-beta 2 promoter sequences fused to the E. coli beta-galactosidase gene were examined throughout the course of embryogenesis and found to exhibit reproducible and specific patterns of beta-galactosidase expression in a majority of sites that have been shown previously to contain mRAR-beta transcripts. In the limbs, mRAR-beta 2 promoter activity and mRAR-beta transcripts were both excluded from precartilagenous condensations; interestingly, mRAR-beta 2 promoter activity was observed in the apical ectodermal ridge (AER) where mRAR-beta transcripts could not be detected, while no mRAR-beta 2 promoter activity or mRAR-beta transcripts were associated with the limb region that contains the zone of polarizing activity (ZPA). Analysis of the lacZ expression pattern in embryos from mothers treated with teratogenic doses of RA, indicated that mRAR-beta 2 promoter is selectively induced in a manner suggesting that overexpression of the mRAR-beta 2 isoform is involved in RA-generated malformations. The normal and induced expression pattern of the mRAR-beta 2 promoter suggests several possible roles for mRAR-beta 2 in development of the limbs, as an inhibitor of cartilage formation, in programmed cell death and in the formation of loose connective tissue.
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PMID:Developmental analysis of the retinoic acid-inducible RAR-beta 2 promoter in transgenic animals. 166 76

Expression vectors have been constructed for a region of the human retinoic acid receptor-alpha (hRAR-alpha) and transferred into F9 embryonal carcinoma (EC) cells. When the vectors are overexpressed in F9 cells, clones can be selected for resistance to retinoic acid-induced differentiation. This effect is obtained even when the hRAR-alpha region is expressed as a beta-galactosidase fusion protein. Using the beta-galactosidase component of the fusion protein as a marker, overexpression of the fusion protein has been correlated with the retinoic acid-resistance effect. The clones resistant to retinoic acid no longer exhibit the normal retinoic acid induction of endo B cytokeratin, laminin B-1, and tissue plasminogen activator mRNAs observed with normal F9 cells. Retinoic acid induction of type IV alpha-1 collagen and Hox-1.3 RNAs is observed with these clones. When transfected with a thyroid receptor DNA-binding sequence (TRE)/thymidine kinase promoter/luciferase construct, the retinoic acid-resistant clones do not yield the same retinoic acid-induced level of luciferase obtained with F9 cells. It is hypothesized that the RAR vectors are interfering with endogenous RAR(s) in a dominant-negative manner to inhibit retinoic acid-induced differentiation of F9 EC cells.
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PMID:Retinoic acid receptor expression vector inhibits differentiation of F9 embryonal carcinoma cells. 255 44

Retinoic acid and its derivatives (retinoids) exert profound influences on epithelial growth differentiation in a variety of tissues, including the skin. How retinoic acid mediates these effects is not fully understood. The recent cloning of a series of nuclear receptors for retinoic acid (RARs) has demonstrated that these proteins can function as ligand-inducible transcriptional enhancing factors. Moreover, all receptors are members of the steroid/thyroid hormone multigene family. In vitro studies have demonstrated the expression of RAR alpha, RAR beta, and RAR gamma in various cell types found in the skin. While multiple isoforms exist for each of the three RARs, it is unclear where each of these receptors functions in vivo to mediate the tissue-specific effects of retinoic acid. As a first step in determining sites of retinoic acid-mediated transcriptional activation in the skin and its appendages, we developed a transgenic model in which the retinoic acid response element (RARE) of the RAR beta 2 isoform is linked to a beta-galactosidase reporter gene. Our observations consistently demonstrate that retinoic acid transcriptionally activates the beta 2RARE in distinct areas of the skin. Of interest, certain of these areas are known to contain stem cells. These data clearly demonstrate that this type of transgenic "reporter" model can be used to further define retinoic acid-regulated signal transduction pathways in the skin, as well as other complex tissues. Furthermore, these observations raise the possibility that transcriptional activation of RAR beta 2 may regulate the growth and differentiation programs of selected populations of stem cells in the skin and its appendages.
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PMID:A beta 2RARE-LacZ transgene identifies retinoic acid-mediated transcriptional activation in distinct cutaneous sites. 808 29

Retinoic acid (RA) affects the growth and differentiation of cells in culture, usually to decrease the growth rate. In amphibian limb regeneration RA has the remarkable ability to affect pattern formation by changing positional identity, but its initial action on the limb is to inhibit division of the blastemal progenitor cells. Newt limb blastemal cells also show this inhibition in culture. In order to investigate the role of different RA receptors (RARs) in the RA response, the hormone binding domain of the newt RARs alpha 1 and delta 1 was replaced with the corresponding region from the Xenopus thyroid hormone receptor-alpha (TR-alpha). In COS cells transfected with each of the chimeras, transcription was activated after exposure to thyroid hormone (T3). Their profile of activity on three different response elements was indicative of RAR specificity and not TR specificity. After transfection of cultured newt blastemal cells with a DNA particle gun, the chimeras were equally active in stimulating T3-dependent transcription of two different synthetic reporter genes. Blastemal cells were transfected with chimeras or control plasmids along with a marker plasmid expressing beta-galactosidase, exposed to RA or T3 and labelled with [3H]thymidine followed by autoradiography. The alpha 1 chimera gave T3-dependent inhibition of growth, comparable to the effect exerted by RA itself, whereas the delta 1 chimera and control plasmids were inactive. The results imply that RAR-alpha 1 mediates the effects of RA on blastemal cell growth.
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PMID:Chimeric retinoic acid/thyroid hormone receptors implicate RAR-alpha 1 as mediating growth inhibition by retinoic acid. 825 72

Bmp2, a highly conserved member of the transforming growth factor-beta gene family, is crucial for normal development. Retinoic acid, combined with cAMP analogs, sharply induces the Bmp2 mRNA during the differentiation of F9 embryonal carcinoma cells into parietal endoderm. Retinoic acid (RA) also induces the Bmp2 gene in chick limb buds. Since normal Bmp2 expression may require an endogenous retinoid signal and aberrant Bmp2 expression may cause some aspects of RA-induced teratogenesis, we studied the mechanism underlying the induction of Bmp2. Measurements of the Bmp2 mRNA half-life and nuclear run-on assays indicated that RA stimulated the transcription rate of the Bmp2 gene. The results of ribonuclease protection and primer extension assays indicated that Bmp2 transcription started 2,127 nucleotides upstream of the translation start site in F9 cells. To identify genetic elements controlling this transcription rate increase, upstream and downstream genomic sequences flanking the Bmp2 gene were screened using chloramphenicol acetyltransferase reporter genes in F9 cells and beta-galactosidase reporter genes in Saccharomyces cerevisiae that were cotransformed with retinoic acid receptor and retinoid X receptor expression plasmids. RA-dependent transcriptional activation was detected between base pairs -2,373 and -2,316 relative to the translation start site. We also identified a required Sp1 binding site between -2,308 and -2,298. The data indicate that Bmp2 is directly regulated by retinoic acid-bound receptors and Sp1.
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PMID:Transcriptional regulation of the Bmp2 gene. Retinoic acid induction in F9 embryonal carcinoma cells and Saccharomyces cerevisiae. 988 May 12

Throughout the reproductive lifespan of most male mammals, sperm production is constant because of the regulated differentiation of spermatogonia. Retinoic acid (RA) and a downstream target, Stra8, are required for complete spermatogenesis. To examine the role of RA in initiating spermatogonial differentiation, a transgenic mouse model expressing beta-galactosidase under the control of an RA response element was used. Cells in the neonatal testis undergoing active RA signaling were visualized by beta-galactosidase activity, the relationship between RA and differentiation determined, and the role of RA-degrading enzymes in regulating RA demonstrated. Beta-galactosidase activity was found to be predominantly associated with differentiating, premeiotic germ cells and to be distributed nonuniformly throughout the seminiferous tubules. Additionally, beta-galactosidase activity in premeiotic germ cells colocalized with STRA8 protein and was induced in germ cells with exogenous RA treatment. The RA-degrading enzyme, CYP26B1, was found to have germ cell localization and nonuniform distribution between tubules via immunohistochemistry. Treatment with a CYP26 enzyme inhibitor resulted in an increased number of germ cells with both beta-galactosidase activity and STRA8 protein and an increase in the expression of genes associated with differentiation and reduced expression of a gene associated with undifferentiated germ cells. These results show the action of RA in a subset of spermatogonia leads to nonuniform initiation of differentiation throughout the neonatal testis, potentially mediated through the action of CYP26 enzymes. Thus, the presence of RA is a likely driving factor in the initiation of spermatogonial differentiation and may result in asynchronous spermatogenesis.
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PMID:Retinoic acid availability drives the asynchronous initiation of spermatogonial differentiation in the mouse. 2084 80

Retinoic acid (RA) is required for germ cell differentiation, the regulation of which gives rise to a constant production of mature sperm. In testes from 3-day postpartum (dpp) RARE-hsplacZ mice, periodic regions positive for beta-galactosidase activity were observed along the length of the seminiferous tubules. Periodicity was abolished by treatment of neonates with exogenous RA at 2 dpp. To assess the consequences, 2-dpp mice were treated with RA, and the long- and short-term effects were assessed. Long-term effects of neonatal RA exposure included a delay in the appearance of advanced germ cells and the absence of a spermatogenic wave (synchronous spermatogenesis) in the adult. In contrast, RA exposure in vitamin A-sufficient adults did not result in synchronous spermatogenesis but rather induced apoptosis in a subset of spermatogonia. Shortly after (24 h) neonates were exposed, altered expression of known germ cell differentiation and the (Stra8, Kit, Sycp3, and Rec8) meiosis markers and an increase in the number of STRA8 and SYCP3 immunopositive cells were observed relative to those of vehicle controls. However, 48 and 72 h after exposure, a significant reduction in the number of STRA8 and SYCP3 immunopositive cells occurred. Immunohistochemical analysis of a marker for apoptosis demonstrated neonatal exposure resulted in increased germ cell apoptosis, as observed in the adult. Additionally, RA exposure resulted in increased Cyp26a1 expression of the RA-degrading enzyme. Thus, while RA treatment of neonatal and adult mice resulted in apoptosis of spermatogonia, synchronous spermatogenesis occurred only after neonatal RA exposure.
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PMID:Exposure to retinoic acid in the neonatal but not adult mouse results in synchronous spermatogenesis. 2122 14

Retinoic acid (RA) is an important developmental morphogen that coordinates anteroposterior and dorsoventral axis patterning, somitic differentiation, neurogenesis, patterning of the hindbrain and spinal cord, and the development of multiple organ systems. Due to its chemical nature as a small amphipathic lipid, direct detection and visualization of RA histologically remains technically impossible. Currently, methods used to infer the presence and localization of RA make use of reporter systems that detect the biological activity of RA. Most established reporter systems, both transgenic mice and cell lines, make use of the highly potent RA response element (RARE) upstream of the RAR-beta gene to drive RA-inducible expression of reporter genes, such as beta-galactosidase or luciferase. The transgenic RARE-LacZ mouse is useful in visualizing spatiotemporal changes in RA signaling especially during embryonic development. However, it does not directly measure overall RA levels. As a reporter system, the F9 RARE-LacZ cell line can be used in a variety of ways, from simple detection of RA to quantitative measurements of RA levels in tissue explants. Here we describe the quantitative determination of relative RA levels generated in embryos and neurosphere cultures using the F9 RARE-LacZ reporter cell line.
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PMID:Quantitative Measurement of Relative Retinoic Acid Levels in E8.5 Embryos and Neurosphere Cultures Using the F9 RARE-Lacz Cell-based Reporter Assay. 2768 94


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