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Prin F, Serpente P, Itasaki N, Gould AP. Hox proteins drive cell segregation and non-autonomous apical remodelling during hindbrain segmentation. Development 2014; 141:1492-502. [PMID: 24574009 PMCID: PMC3957373 DOI: 10.1242/dev.098954] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 01/22/2014] [Indexed: 01/26/2023]
Abstract
Hox genes encode a conserved family of homeodomain transcription factors regulating development along the major body axis. During embryogenesis, Hox proteins are expressed in segment-specific patterns and control numerous different segment-specific cell fates. It has been unclear, however, whether Hox proteins drive the epithelial cell segregation mechanism that is thought to initiate the segmentation process. Here, we investigate the role of vertebrate Hox proteins during the partitioning of the developing hindbrain into lineage-restricted units called rhombomeres. Loss-of-function mutants and ectopic expression assays reveal that Hoxb4 and its paralogue Hoxd4 are necessary and sufficient for cell segregation, and for the most caudal rhombomere boundary (r6/r7). Hox4 proteins regulate Eph/ephrins and other cell-surface proteins, and can function in a non-cell-autonomous manner to induce apical cell enlargement on both sides of their expression border. Similarly, other Hox proteins expressed at more rostral rhombomere interfaces can also regulate Eph/ephrins, induce apical remodelling and drive cell segregation in ectopic expression assays. However, Krox20, a key segmentation factor expressed in odd rhombomeres (r3 and r5), can largely override Hox proteins at the level of regulation of a cell surface target, Epha4. This study suggests that most, if not all, Hox proteins share a common potential to induce cell segregation but in some contexts this is masked or modulated by other transcription factors.
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Affiliation(s)
- Fabrice Prin
- Division of Physiology and Metabolism, Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| | - Patricia Serpente
- Division of Physiology and Metabolism, Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| | - Nobue Itasaki
- Division of Developmental Neurobiology, Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| | - Alex P. Gould
- Division of Physiology and Metabolism, Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
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2
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Biomarkers of teratogenesis: Suggestions from animal studies. Reprod Toxicol 2012; 34:180-5. [DOI: 10.1016/j.reprotox.2012.05.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 05/03/2012] [Accepted: 05/10/2012] [Indexed: 12/19/2022]
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3
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Cadot S, Frenz D, Maconochie M. A novel method for retinoic acid administration reveals differential and dose-dependent downregulation of Fgf3 in the developing inner ear and anterior CNS. Dev Dyn 2012; 241:741-58. [DOI: 10.1002/dvdy.23748] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2012] [Indexed: 12/23/2022] Open
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4
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Di Renzo F, Corsini E, Broccia M, Marinovich M, Galli C, Giavini E, Menegola E. Molecular mechanism of teratogenic effects induced by the fungicide triadimefon: Study of the expression of TGF-β mRNA and TGF-β and CRABPI proteins during rat in vitro development. Toxicol Appl Pharmacol 2009; 234:107-16. [DOI: 10.1016/j.taap.2008.09.025] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Revised: 09/29/2008] [Accepted: 09/29/2008] [Indexed: 10/21/2022]
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5
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Griffith AV, Cardenas K, Carter C, Gordon J, Iberg A, Engleka K, Epstein JA, Manley NR, Richie ER. Increased thymus- and decreased parathyroid-fated organ domains in Splotch mutant embryos. Dev Biol 2008; 327:216-27. [PMID: 19135046 DOI: 10.1016/j.ydbio.2008.12.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 11/13/2008] [Accepted: 12/16/2008] [Indexed: 01/23/2023]
Abstract
Embryos that are homozygous for Splotch, a null allele of Pax3, have a severe neural crest cell (NCC) deficiency that generates a complex phenotype including spina bifida, exencephaly and cardiac outflow tract abnormalities. Contrary to the widely held perception that thymus aplasia or hypoplasia is a characteristic feature of Pax3(Sp/Sp) embryos, we find that thymic rudiments are larger and parathyroid rudiments are smaller in E11.5-12.5 Pax3(Sp/Sp) compared to Pax3(+/+) embryos. The thymus originates from bilateral third pharyngeal pouch primordia containing endodermal progenitors of both thymus and parathyroid glands. Analyses of Foxn1 and Gcm2 expression revealed a dorsal shift in the border between parathyroid- and thymus-fated domains at E11.5, with no change in the overall cellularity or volume of each shared primordium. The border shift increases the allocation of third pouch progenitors to the thymus domain and correspondingly decreases allocation to the parathyroid domain. Initial patterning in the E10.5 pouch was normal suggesting that the observed change in the location of the organ domain interface arises during border refinement between E10.5 and E11.5. Given the well-characterized NCC defects in Splotch mutants, these findings implicate NCCs in regulating patterning of third pouch endoderm into thymus- versus parathyroid-specified domains, and suggest that organ size is determined in part by the number of progenitor cells specified to a given fate.
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Affiliation(s)
- Ann V Griffith
- Department of Carcinogenesis, University of Texas MD Anderson Cancer Center, Science Park Research Division, Smithville, TX 78957, USA
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6
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Zhang Y, Liu K, Gao Y, Li S. Modulation of Dishevelled and Vangl2 by all-trans-retinoic acid in the developing mouse central nervous system and its relationship to teratogenesis. Acta Biochim Biophys Sin (Shanghai) 2007; 39:684-92. [PMID: 17805463 DOI: 10.1111/j.1745-7270.2007.00325.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The response to exposure to all-trans-retinoic acid (RA) during embryogenesis varies from physiologic to severe teratogenic effects and is dependent upon the dose and the stage of development in all species. Vangl2 and Dishevelled genes play key roles in establishing planar cell polarity and regulating convergent extension movements during the neurula period. The effects of RA-mediated teratogenesis might be due to its misregulation of Vangl2 and Dishevelled genes. The aim of this study is to monitor the modulation of Vangl2 and Dishevelled in Kunming mouse embryos following maternal treatment with a single oral dose of 30 mg/(kg body weight) of RA during the neurula period. Exposure of 7.75 d embryos to RA induced characteristic morphological changes. The most obvious external effect was the failure of neural tube closure in the midbrain and forebrain regions in 10 d embryos, resulting in exencephaly in later embryos. RA treatment also led to a pronounced decrease of Vangl2 mRNA at 4 and 18 h and a pronounced increase at 66 h after maternal treatment, as detected by reverse transcription-polymerase chain reaction. Western blot analysis showed a marked decrease of Vangl2 protein at 18 and 42 h and a marked increase at 66 and 90 h after maternal treatment. Dishevelled1/2/3 mRNA was significantly down-regulated at 4 and 18 h and up-regulated at 42 h in the fetus after RA treatment, except for an up-regulation of Dishevelled3 at 66 h. The Dishevelled2 mRNA and its protein matched each other. These results hinted that Vangl2 and Dishevelled genes might take part in RA teratogenesis of mouse embryos.
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Affiliation(s)
- Yanping Zhang
- Department of Histology and Embryology, Medical College of Shandong University, Jinan 250012, China
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7
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Malik MA, Blusztajn JK, Greenwood CE. Nutrients as trophic factors in neurons and the central nervous system: role of retinoic acid. J Nutr Biochem 2005; 11:2-13. [PMID: 15539337 DOI: 10.1016/s0955-2863(99)00066-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/1999] [Accepted: 09/28/1999] [Indexed: 12/21/2022]
Abstract
In multicellular organisms, death, survival, proliferation, and differentiation of a given cell depend on signals produced by neighboring and/or distant cells, resulting in the coordinated development and function of the various tissues. In the nervous system, control of cell survival and differentiation is achieved through the action of a distinct group of polypeptides collectively known as neurotrophic factors. Recent findings support the view that trophic factors also are involved in the response of the nervous system to acute injury. By contrast, nutrients are not traditionally viewed as potential trophic factors; however, there is increasing evidence that at least some influence neuronal differentiation. During development the brain is responsive to variations in nutrient supply, and this increased sensitivity or vulnerability of the brain to nutrient supply may reappear during neuronal repair, a period during which a rapid membrane resynthesis and reestablishment of synthetic pathways occur. To further evaluate the potential of specific nutrients to act as pharmacologic agents in the repair of injured neurons, the effects of retinoic acid, an active metabolite of vitamin A, and its role as a trophic factor are discussed. This literature review is intended to provide background information regarding the effect of retinoic acid on the cholinergic phenotype and the differentiation of these neurons and to explain how it may promote neuronal repair and survival following injury.
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Affiliation(s)
- M A Malik
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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8
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Reijntjes S, Gale E, Maden M. Generating gradients of retinoic acid in the chick embryo: Cyp26C1 expression and a comparative analysis of the Cyp26 enzymes. Dev Dyn 2004; 230:509-17. [PMID: 15188435 DOI: 10.1002/dvdy.20025] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have cloned a novel retinoic acid (RA) catabolizing enzyme, Cyp26C1, in the chick and describe here its distribution during early stages of chick embryogenesis. It is expressed from stage 4 in the presumptive anterior (cephalic) mesoderm, in a subset of cephalic neural crest cells, the ventral otic vesicle, mesenchyme adjacent to the otic vesicle, the branchial pouches and grooves, a part of the neural retina, and the anterior telencephalon, and shows a dynamic expression in the hindbrain rhombomeres and neuronal populations within them. By examining the distribution of Cyp26C1 in the RA-free quail embryo, we can determine which of these expression domains is dependent on RA, and it is only the rhombomeric sites that do not appear, suggesting a role for RA in this location. The most striking domain of Cyp26C1 distribution is in the anterior cephalic mesoderm, which is adjacent to the domain of Raldh2 in the trunk mesoderm, but separated from it by a gap dorsal to which the posterior hindbrain will develop. We suggest that a gradient of RA within the mesoderm generated by Raldh2 and catabolized by Cyp26C1 could be responsible for patterning the hindbrain. We have compared this distribution of Cyp26C1 with that of Cyp26A1 and Cyp26B1 in the chick and shown that they generally occupy nonoverlapping sites of expression in the embryo, and as a result, we suggest individual roles for each of the Cyp enzymes in the developing embryo.
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Affiliation(s)
- Susan Reijntjes
- MRC Centre for Developmental Neurobiology, King's College London, London United Kingdom
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9
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Okada Y, Shimazaki T, Sobue G, Okano H. Retinoic-acid-concentration-dependent acquisition of neural cell identity during in vitro differentiation of mouse embryonic stem cells. Dev Biol 2004; 275:124-42. [PMID: 15464577 DOI: 10.1016/j.ydbio.2004.07.038] [Citation(s) in RCA: 262] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2004] [Revised: 07/19/2004] [Accepted: 07/21/2004] [Indexed: 12/23/2022]
Abstract
Retinoic acid (RA) is one of the most important morphogens, and its embryonic distribution correlates with neural differentiation and positional specification in the developing central nervous system. To investigate the concentration-dependent effects of RA on neural differentiation of mouse embryonic stem cells (ES cells), we investigated the precise expression profiles of neural and regional specific genes by ES cells aggregated into embryoid bodies (EBs) exposed to various concentrations of RA or the BMP antagonist Noggin. RA promoted both neural differentiation and caudalization in a concentration-dependent manner, and the concentration of RA was found to regulate dorso-ventral identity, i.e., higher concentrations of RA induced a dorsal phenotype, and lower concentrations of RA induced a more ventral phenotype. The induction of the more ventral phenotype was due to the higher expression level of the N-terminus of sonic hedgehog protein (Shh-N) when treated with low concentration RA, as it was abrogated by an inhibitor of Shh signaling, cyclopamine. These findings suggest that the concentration of RA strictly and simultaneously regulates the neuralization and positional specification during differentiation of mouse ES cells and that it may be possible to use it to establish a strategy for controlling the identity of ES-cell-derived neural cells.
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Affiliation(s)
- Yohei Okada
- Department of Physiology, Keio University School of Medicine, Shinjuku-ku, Tokyo 160-8582, Japan
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10
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Otto DME, Henderson CJ, Carrie D, Davey M, Gundersen TE, Blomhoff R, Adams RH, Tickle C, Wolf CR. Identification of novel roles of the cytochrome p450 system in early embryogenesis: effects on vasculogenesis and retinoic Acid homeostasis. Mol Cell Biol 2003; 23:6103-16. [PMID: 12917333 PMCID: PMC180925 DOI: 10.1128/mcb.23.17.6103-6116.2003] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cytochrome P450-dependent monooxygenase system catalyzes the metabolism of xenobiotics and endogenous compounds, including hormones and retinoic acid. In order to establish the role of these enzymes in embryogenesis, we have inactivated the system through the deletion of the gene for the electron donor to all microsomal P450 proteins, cytochrome P450 reductase (Cpr). Mouse embryos homozygous for this deletion died in early to middle gestation (approximately 9.5 days postcoitum [dpc]) and exhibited a number of novel phenotypes, including the severe inhibition of vasculogenesis and hematopoiesis. In addition, defects in the brain, limbs, and cell types where CPR was shown to be expressed were observed. Some of the observed abnormalities have been associated with perturbations in retinoic acid homeostasis in later embryogenesis. Consistent with this possibility, embryos at 9.5 dpc had significantly elevated levels of retinoic acid and reduced levels of retinol. Further, some of the observed phenotypes could be either reversed or exacerbated by decreasing or increasing maternal retinoic acid exposure, respectively. Detailed analysis demonstrated a close relationship between the observed phenotype and the expression of genes controlling vasculogenesis. These data demonstrate that the cytochrome P450 system plays a key role in early embryonic development; this process appears to be, at least in part, controlled by regional concentrations of retinoic acid and has profound effects on blood vessel formation.
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Affiliation(s)
- Diana M E Otto
- Cancer Research UK, Molecular Pharmacology Unit, Biomedical Research Centre, Ninewells Hospital and Medical School, Dundee DD1 9SY, United Kingdom
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11
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Perrotta S, Nobili B, Rossi F, Di Pinto D, Cucciolla V, Borriello A, Oliva A, Della Ragione F. Vitamin A and infancy. Biochemical, functional, and clinical aspects. VITAMINS AND HORMONES 2003; 66:457-591. [PMID: 12852263 DOI: 10.1016/s0083-6729(03)01013-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Vitamin A is a very intriguing natural compound. The molecule not only has a complex array of physiological functions, but also represents the precursor of promising and powerful new pharmacological agents. Although several aspects of human retinol metabolism, including absorption and tissue delivery, have been clarified, the type and amounts of vitamin A derivatives that are intracellularly produced remain quite elusive. In addition, their precise function and targets still need to be identified. Retinoic acids, undoubtedly, play a major role in explaining activities of retinol, but, recently, a large number of physiological functions have been attributed to different retinoids and to vitamin A itself. One of the primary roles this vitamin plays is in embryogenesis. Almost all steps in organogenesis are controlled by retinoic acids, thus suggesting that retinol is necessary for proper development of embryonic tissues. These considerations point to the dramatic importance of a sufficient intake of vitamin A and explain the consequences if intake of retinol is deficient. However, hypervitaminosis A also has a number of remarkable negative consequences, which, in same cases, could be fatal. Thus, the use of large doses of retinol in the treatment of some human diseases and the use of megavitamin therapy for certain chronic disorders as well as the growing tendency toward vitamin faddism should alert physicians to the possibility of vitamin overdose.
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Affiliation(s)
- Silverio Perrotta
- Department of Pediatric, Medical School, Second University of Naples, Naples, Italy
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12
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Yamamoto M, Zhang J, Smith D, Hayakawa Y, McCaffery P. A critical period for retinoic acid teratogenesis and loss of neurophilic migration of pontine nuclei neurons. Mech Dev 2003; 120:701-9. [PMID: 12834869 DOI: 10.1016/s0925-4773(03)00047-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Abnormalities in the pontine nuclei (PN) and inferior olive are hallmarks of human retinoic acid (RA) teratogenesis. This study shows that RA exposure of the mouse at a specific embryonic stage alters morphological structures that derive from the wall of the IVth ventricle to form components of the precerebellar system (the inferior olivary nucleus and the PN). The study employs both normal and a RAREhspLacZ transgenic RA reporter mouse. It is shown that abnormalities in the PN and inferior olive result from exposure at a critical period of embryonic day 9.5 and 10.5. The abnormalities in the PN are due to a failure in their usual neurophilic migration. The compact stream of cells that leads from the anterior rhombic lip to the ventral pons is instead scattered widely over the anterior medulla. Given that the RA exposure occurs after the resolution of rhombomere identity this suggests that teratogenic RA interferes with a regulatory event that overlays this original pattern.
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Affiliation(s)
- M Yamamoto
- UMMS/E.K. Shriver Center, 200 Trapelo Rd., Waltham, MA 02452, USA
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13
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Chen AC, Yu K, Lane MA, Gudas LJ. Homozygous deletion of the CRABPI gene in AB1 embryonic stem cells results in increased CRABPII gene expression and decreased intracellular retinoic acid concentration. Arch Biochem Biophys 2003; 411:159-73. [PMID: 12623064 DOI: 10.1016/s0003-9861(02)00732-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cellular retinoic acid (RA) binding proteins I and II (CRABPI and CRABPII), intracellular proteins which bind retinoic acid with high affinity, are involved in the actions of RA, though their exact roles are not fully understood. We have generated several genetically engineered AB1 cell lines in which both alleles of the CRABPI gene have been deleted by homologous recombination. We have used these CRABPI knockout cell lines to examine the consequences of functional loss of CRABPI on RA-induced gene expression and RA metabolism in the murine embryonic stem cell line, AB1, which undergoes differentiation in response to RA. Complete lack of CRABPI results in decreased intracellular [3H]RA concentrations under conditions in which external concentrations of [3H]RA are low (1-10nM) and in an altered distribution of [3H] polar metabolites of [3H]RA in the cell and in the medium. Fewer [3H] polar metabolites are retained within the CRABPI(-/-) cells compared to the wild-type cells. These data suggest that CRABPI functions to regulate the intracellular concentrations of retinoic acid and to maintain high levels of oxidized retinoic acid metabolites such as 4-oxoretinoic acid within cells.
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Affiliation(s)
- Anne C Chen
- Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10021, USA
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14
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Chan WY, Tam WY, Yung KM, Cheung CS, Sham MH, Copp AJ. Tracking Down the Migration of Mouse Neural Crest Cells. ACTA ACUST UNITED AC 2003. [DOI: 10.1159/000068497] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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15
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Affiliation(s)
- Malcolm Maden
- MRC Centre for Developmental Neurobiology, 4th Floor New Hunt's House, King's College London, Guy's Campus, London Bridge, London SE1 1UL, UK.
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16
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Maden M. Role and distribution of retinoic acid during CNS development. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 209:1-77. [PMID: 11580199 DOI: 10.1016/s0074-7696(01)09010-6] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Retinoic acid (RA), the biologically active derivative of vitamin A, induces a variety of embryonal carcinoma and neuroblastoma cell lines to differentiate into neurons. The molecular events underlying this process are reviewed with a view to determining whether these data can lead to a better understanding of the normal process of neuronal differentiation during development. Several transcription factors, intracellular signaling molecules, cytoplasmic proteins, and extracellular molecules are shown to be necessary and sufficient for RA-induced differentiation. The evidence that RA is an endogenous component of the developing central nervous system (CNS) is then reviewed, data which include high-pressure liquid chromotography (HPLC) measurements, reporter systems and the distribution of the enzymes that synthesize RA. The latter is particularly relevant to whether RA signals in a paracrine fashion on adjacent tissues or whether it acts in an autocrine manner on cells that synthesize it. It seems that a paracrine system may operate to begin early patterning events within the developing CNS from adjacent somites and later within the CNS itself to induce subsets of neurons. The distribution of retinoid-binding proteins, retinoid receptors, and RA-synthesizing enzymes is described as well as the effects of knockouts of these genes. Finally, the effects of a deficiency and an excess of RA on the developing CNS are described from the point of view of patterning the CNS, where it seems that the hindbrain is the most susceptible part of the CNS to altered levels of RA or RA receptors and also from the point of view of neuronal differentiation where, as in the case of embryonal carcinoma (EC) cells, RA promotes neuronal differentiation. The crucial roles played by certain genes, particularly the Hox genes in RA-induced patterning processes, are also emphasized.
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Affiliation(s)
- M Maden
- MRC Centre for Developmental Neurobiology, King's College London, United Kingdom
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Makori N, Peterson PE, Hendrickx AG. 13-cis-retinoic acid causes patterning defects in the early embryonic rostral hindbrain and abnormal development of the cerebellum in the macaque. TERATOLOGY 2001; 63:65-76. [PMID: 11241428 DOI: 10.1002/1096-9926(200102)63:2<65::aid-tera1011>3.0.co;2-m] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND We have previously reported that exposure of embryos to 13-cis-retinoic acid (cRA) results in an abnormal phenotype of the fetal cerebellum. In this study, we analyzed early changes in the cerebellar anlagen (midbrain-hindbrain junction) as well as lesions of the fetal cerebellar vermis after a teratogenic dosing regimen of cRA in the macaque model. METHODS We examined embryo coronal sections of the midbrain-hindbrain junction immunostained for Pax-2, Engrailed-2 (En-2) and Krox-20. To characterize the cerebellum foliation and fissure formation processes, we analyzed vermal cortical cell layer development and the number and depth of the major fissures on sagittal sections of fetal vermis. We also examined Purkinje cell development in vermal sections immunostained for CD3. RESULTS Compared with controls, there was a consistent truncation of the midbrain-hindbrain region of early embryos exposed to cRA. The cRA-induced fetal vermis lesions included inhibition in its anteroposterior growth, altered folial patterning, a general loss of prominence of the fissures accompanied by a total loss of sublobular fissures, and changes in cortical cell layer development. CD3(+) Purkinje cells were abnormally dispersed deep into the molecular layer in the vermis. CONCLUSIONS Our findings indicate that the effects of cRA on the developing cerebellum involve interference with the hierarchy of complex cellular and genetic interactions that lead to the growth and subdivision of the cerebellum into smaller units. The regional vermal defects may be related to early postnatal functional deficits.
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Affiliation(s)
- N Makori
- California Regional Primate Research Center, University of California, One Shields Avenue, Davis, California 95616-8542, USA
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18
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Chung JJ, Cho S, Kwon YK, Kim DH, Kim K. Activation of retinoic acid receptor gamma induces proliferation of immortalized hippocampal progenitor cells. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 83:52-62. [PMID: 11072095 DOI: 10.1016/s0169-328x(00)00196-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the present study, we report evidence that activation of RARgamma promotes cell proliferation in immortalized hippocampal progenitor cell line HiB5. We found that treatment of HiB5 cells with all-trans- (all-trans-RA) or 9-cis-retinoic acid (9-cis-RA) significantly increased the number of dead floating cells as well as viable cells in serum-free defined medium (N2). Flow cytometric analysis of DNA contents revealed that the proportion of apoptotic cells over the whole cell population was not affected by both retinoids. Instead, the proportion of S phase cells was significantly increased by retinoids. Under this condition, bcl-2 mRNA levels were significantly increased over time by retinoid treatment, whereas bax mRNA levels were not affected. This suggests that retinoids increase viable cells by enhancing proliferation rather than by suppressing apoptosis. In an attempt to dissect the molecular mechanism underlying retinoid-induced HiB5 cell proliferation, we examined the expression patterns of retinoid receptors following retinoid treatment. Retinoids induced RARgamma mRNA, which paralleled the increase in the transactivation of strong retinoic acid response element (RARE) reporter construct. Accordingly, treatment of HiB5 cells with RARgamma-selective agonist (CD666) increased HiB5 cell number in a dose-dependent manner, which was blocked by co-treatment with RARgamma-selective antagonist (CD2665). Taken together, these data clearly indicate that activation of RARgamma increases proliferation of immortalized hippocampal progenitor cells.
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Affiliation(s)
- J J Chung
- School of Biological Sciences, Seoul National University, 151-742, Seoul, South Korea
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19
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Hoover F, Kielland A, Glover JC. RXR? gene is expressed by discrete cell columns within the alar plate of the brainstem of the chicken embryo. J Comp Neurol 2000. [DOI: 10.1002/(sici)1096-9861(20000124)416:4<417::aid-cne1>3.0.co;2-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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20
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Brewer A, Gove C, Davies A, McNulty C, Barrow D, Koutsourakis M, Farzaneh F, Pizzey J, Bomford A, Patient R. The human and mouse GATA-6 genes utilize two promoters and two initiation codons. J Biol Chem 1999; 274:38004-16. [PMID: 10608869 DOI: 10.1074/jbc.274.53.38004] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GATA-6 has been implicated in the regulation of myocardial differentiation during cardiogenesis. To determine how its expression is controlled, we have characterized the human and mouse genes. We have mapped their transcriptional start sites and demonstrate that two alternative promoters and 5' noncoding exons are utilized. Both transcript isoforms are expressed in the same tissue-specific and developmental stage-specific pattern, and their ratio appears similar wherever examined. The more upstream noncoding exon showed a substantial degree of homology between the two mammalian species, suggesting a conserved regulatory function. Moreover, in transfection assays we show that elements within this exon act to promote its transcription. Positive regulatory elements that effect transcription from the more downstream exon were not apparent in this assay, revealing a regulatory distinction between the two promoters. We also demonstrate alternative initiator codon usage in both the human and mouse GATA-6 genes. Both isoforms of the protein are synthesized in vitro regardless of which 5' noncoding exon is present in the RNA, although the larger protein has greater transcriptional activation potential in transfection assays. Thus, GATA-6 function in the cell is controlled by a complex interplay of transcriptional and translational regulation.
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Affiliation(s)
- A Brewer
- Department of Molecular Medicine, The Rayne Institute, GKT, 123 Coldharbour Lane, London SE5 9NU, United Kingdom
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21
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Abstract
We report here the development and rescue of the truncated hindbrain of retinoid-deprived quail embryos. The embryo is completely rescued by an injection of retinol into the egg; this confirms retinol, or a related retinoid, as a required molecule in hindbrain development. Staging the retinoid replacement enabled us to determine that the 3-4 somite stage is the period when retinoids are required for normal development. Analysis of the development of the retinoid-deprived hindbrain phenotype through somitogenesis has revealed a pathway of retinoid action in early hindbrain regionalization. The hindbrain of the retinoid-deprived embryo is normal in size, during early somitogenesis, but has a respecified pattern of Krox-20 expression. From the earliest expression of Krox-20, at the 5 somite stage, the rhombomere 3 stripe fills the caudal third of the developing hindbrain to the level of the first somite. Morphologically only 2, instead of the normal 5, rhombomere bulges form. These 2 bulges express genes and, later, develop morphology characteristic of rhombomeres 1 and 2 and rhombomere 3. Posterior hindbrain specific genes, Hoxb-1, Fgf3, MafB, and the rhombomere 5 stripe of Krox-20 are never expressed in the head neuroepithelium of these embryos. From the initial formation of the neural plate, there is no evidence of rhombomere 4-7 specific characteristics. These results indicate the specification of the posterior hindbrain is lost and its cells participate in the formation of an enlarged anterior hindbrain. In our previous study, we reported the absence of the posterior hindbrain in retinoid-deprived quails (Maden, M., Gale, E., Kostetskii, I., Zile, M., 1996. Vitamin A-deficient quail embryos have half a hindbrain and other neural defects. Curr. Biol. 6, 417-426). Here, we show this phenotype to be the result of respecification of the hindbrain cells. This provides evidence for a region specific response to a single stimulus, retinol, which suggests a pre-rhombomeric regionalization of the hindbrain.
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Affiliation(s)
- E Gale
- New Hunt's House, King's College London, Guy's Campus, London Bridge, London, UK.
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22
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Affiliation(s)
- M Maden
- Developmental Biology Research Centre, King's College London, England
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23
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Clotman F, Van Maele-Fabry G, Picard JJ. All-trans-retinoic acid upregulates the expression of COUP-TFI in early-somite mouse embryos cultured in vitro. Neurotoxicol Teratol 1998; 20:591-9. [PMID: 9831119 DOI: 10.1016/s0892-0362(98)00018-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Exposure of embryos to an excess of retinoic acid (RA) modifies the spatio-temporal pattern of expression of developmental genes. RA regulates the expression of target genes through binding of the retinoid nuclear receptors (RARs and RXRs), as heterodimers, to regulatory cis-acting elements. COUP-TF factors, which are able to dimerize with the RXRs and to compete with the retinoid receptors for their DNA binding sites, are suspected to modulate the retinoid signal transduction pathway. Therefore, COUP-TF factors may be involved in the regulation of the expression of developmental genes and/or in the modifications induced by an excess of RA in the expression of these genes. The aim of this work is to assess whether RA-induced modifications in the expression of Krox-20 and Hox genes correlate with alterations of the expression of COUP-TF genes. In addition to spatial modifications in the expression patterns of Krox-20 and Hox genes, we report here an upregulation of the expression level of COUP-TFI after RA exposure. However, this abnormality did not spatially overlap with the modifications observed in the expression of Krox-20 and Hox genes. These data suggest an involvement of COUP-TFI in the generation of RA-induced abnormalities, but do not support the hypothesis of an involvement of this factor in the regulation of the expression of Hox or Krox-20 genes.
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Affiliation(s)
- F Clotman
- Center for Transgene Technology and Gene Therapy, Flanders Interuniversity Institute for Biotechnology, Leuven, Belgium
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24
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Hoover F, Glover JC. Regional pattern of retinoid X receptor-alpha gene expression in the central nervous system of the chicken embryo and its up-regulation by exposure to 9-cis retinoic acid. J Comp Neurol 1998; 398:575-86. [PMID: 9717711 DOI: 10.1002/(sici)1096-9861(19980907)398:4<575::aid-cne9>3.0.co;2-#] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have investigated the expression of the retinoid X receptor-alpha (RXRalpha) gene in the developing chicken embryo by using nonradioactive wholemount in situ hybridization. At the earliest stage of development examined (stage 9; Hamburger and Hamilton [1951] J. Morphol. 88:49-92), we detect RXRalpha transcripts in a stretch of neuroepithelium corresponding roughly to the presumptive caudal hindbrain. Upon formation of the rhombomeres at stage 12, a strongly RXRalpha-positive region extends from a sharp rostral limit at the boundary between rhombomeres 6 and 7 caudad to at least the level of somite 9. This pattern of highest expression continues at least until stage 22 but with some variability in the caudal extent. A lower level of expression extends throughout the spinal cord. Transverse sections show that RXRalpha transcripts are expressed in a gradient, with the highest levels near the roof plate and decreasing toward the floor plate. At later stages, the level of expression is highest in the proliferative ventricular zone. However, at reduced levels, RXRalpha transcripts are also detectable in the mantle zone as well as outside the developing central nervous system, for example, in the neural crest and the limb buds. Nine-cis-retinoic acid up-regulates RXRalpha transcripts at stages 19.5-22.0 within a few hours, augmenting but not expanding the expression pattern. Northern blots demonstrate the potential expression of multiple RXRalpha isoforms in the central nervous system at posthatch stages. These results implicate the RXRalpha receptor in both rostrocaudal and transverse patterning of the neural tube.
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Affiliation(s)
- F Hoover
- Department of Anatomy, Institute for Basic Medical Sciences, University of Oslo, Norway
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25
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Makori N, Peterson PE, Blankenship TN, Dillard-Telm L, Hummler H, Hendrickx AG. Effects of 13-cis-retinoic acid on hindbrain and craniofacial morphogenesis in long-tailed macaques (Macaca fascicularis). J Med Primatol 1998; 27:210-9. [PMID: 9879862 DOI: 10.1111/j.1600-0684.1998.tb00073.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hindbrain and craniofacial development during early organogenesis was studied in normal and retinoic acid-exposed Macaca fascicularis embryos. 13-cis-retinoic acid impaired hindbrain segmentation as evidenced by compression of rhombomeres 1 to 5. Immunolocalization with the Hoxb-1 gene product along with quantitative measurements demonstrated that rhombomere 4 was particularly vulnerable to size reduction. Accompanying malformations of cranial neural crest cell migration patterns involved reduction and/or delay in pre- and post-otic placode crest cell populations that contribute to the pharyngeal arches and provide the developmental framework for the craniofacial region. The first and second pharyngeal arches were partially fused and the second arch was markedly reduced in size. The otocyst was delayed in development and shifted rostrolaterally relative to the hindbrain. These combined changes in the hindbrain, neural crest, and pharyngeal arches contribute to the craniofacial malformations observed in the retinoic acid malformation syndrome manifested in the macaque fetus.
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Affiliation(s)
- N Makori
- California Regional Primate Research Center, University of California, Davis 95616, USA
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26
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Kleinjan DA, Dekker S, Guy JA, Grosveld FG. Cloning and sequencing of the CRABP-I locus from chicken and pufferfish: analysis of the promoter regions in transgenic mice. Transgenic Res 1998; 7:85-94. [PMID: 9608736 DOI: 10.1023/a:1008864224100] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Retinoic acid (RA), a derivative of vitamin A, is an important molecule for development and homeostasis of vertebrate organisms. The intracellular retinoic acid binding protein CRABP-I has a high affinity for RA, and is thought to be involved in the mechanism of RA signalling. CRABP-I is well conserved in evolution and shows a specific expression pattern during development, but mice made deficient for the protein by gene targeting appear normal. However, the high degree of homology with CRABP-I from other species indicates that the protein has been subject to strong selective conservation, indicative of an important biological function. In this paper we have compared the conservation in the expression pattern of the mouse, chicken and pufferfish CRABP-I genes to substantiate this argument further. First we cloned and sequenced genes and promoter regions of the CRABP-I genes from chicken and the Japanese pufferfish, Fugu rubripes. Sequence comparison with the mouse gene did not show any large blocks of homology in the promoter regions. Nevertheless, the promoter of the chicken gene directed expression to a subset of the tissues that show expression with the promoter from the mouse gene. The pattern observed with the pufferfish promoter is even more restricted, essentially to rhombomere 4 only, indicating that this region may be functionally the most important for CRABP-I expression in the developing embryo.
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Affiliation(s)
- D A Kleinjan
- Department of Cell Biology and Genetics, Erasmus University Rotterdam, The Netherlands
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27
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Maden M, Gale E, Zile M. The role of vitamin A in the development of the central nervous system. J Nutr 1998; 128:471S-475S. [PMID: 9478051 DOI: 10.1093/jn/128.2.471s] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We describe here the defects that arise in the central nervous system (CNS) of quail embryos when they develop in the absence of vitamin A. It has been assumed that because of the effects of excess vitamin A and its metabolites, particularly retinoic acid (RA), on the CNS they are involved in various aspects of CNS development. We show that this is indeed the case, because these deficient quail embryos have three defects in their CNS. First, the posterior hindbrain fails to develop because the cells fated to form this part of the CNS in the very early embryo die by apoptosis. Second, the neural tube fails to extend neurites into the periphery both in vivo and in vitro. Third, the neural crest cells throughout the embryo die by apoptosis. These results demonstrate a crucial requirement for vitamin A in CNS development.
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Affiliation(s)
- M Maden
- Developmental Biology Research Centre, King's College London, U.K
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28
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Abstract
In this study we tested whether the segmental identities of the hindbrain and its derived neural crest are necessarily linked or, instead, if they can be altered independently. Using morphological criteria, we show that the hindbrains of Hoxa-2 mutant mice, in which the second arch skeletal derivatives assume first arch characteristics (Gendron-Maguire et al. [1993] Cell 75:1317-1331; Rijli et al. [1993] Cell 75:1333-1349), retain normal segmental identities. Also, by phenotypic analysis, we show that, with retinoic acid, changes can be induced in the identity of the preotic hindbrain without effects in its derived neural crest. Our data thus indicate that identity changes in the hindbrain and branchial arch neural crest can occur independently. Moreover, if Hoxa-2 is concomitantly induced by retinoic acid in the first branchial arch, the proximal derivatives of this arch are also affected. We propose a model for the patterning of the branchial region, according to which the segmental identity in this area is provided mainly by the branchial arches.
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Affiliation(s)
- M Mallo
- Max-Planck Institute of Immunobiology, Freiburg, Germany.
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29
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Kleinjan DA, Dekker S, Vaessen MJ, Grosveld F. Regulation of the CRABP-I gene during mouse embryogenesis. Mech Dev 1997; 67:157-69. [PMID: 9392513 DOI: 10.1016/s0925-4773(97)00116-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The cellular retinoic acid binding protein type I (CRABP-I) shows a highly specific expression pattern during mouse embryonic development. The tissues that express CRABP-I, i.e. the central nervous system (CNS), neural crest, branchial arches, limb bud and frontonasal mass, coincide with those that are most sensitive to unphysiological retinoic acid (RA) concentrations. We have investigated the transcriptional elements that are responsible for the spatiotemporal regulation of CRABP-I expression in the mouse embryo. We show here that a 16 kb fragment harbours all the elements needed for the correct spatiotemporal expression pattern. Upon further dissection of this fragment we have found that expression in the CNS is driven by elements in the upstream region of the gene, while expression in mesenchymal and neural crest tissue is regulated via element(s) located downstream of exon II of the gene. Two distinct fragments in the upstream region are required for expression in the CNS, as neither of these fragments alone is able to drive correct expression of a reporter gene in transgenic mice. DNAseI footprinting analysis of the two upstream fragments revealed the presence of a number of protected elements. One of these regulatory elements has the hallmarks of an RA response element, suggesting that CRABP-I expression in neural tissue can be directly modulated by RA via the RARs/RXRs.
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Affiliation(s)
- D A Kleinjan
- Department of Cell Biology and Genetics, Erasmus University Rotterdam, The Netherlands
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30
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Affiliation(s)
- M B Rogers
- Department of Biology, University of South Florida Tampa 33620-5150, USA
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31
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Means AL, Gudas LJ. The CRABP I gene contains two separable, redundant regulatory regions active in neural tissues in transgenic mouse embryos. Dev Dyn 1997; 209:59-69. [PMID: 9142496 DOI: 10.1002/(sici)1097-0177(199705)209:1<59::aid-aja6>3.0.co;2-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The CRABP I gene is expressed in a spatiotemporal pattern in neural and mesenchymal tissues at the onset of organogenesis. The neural pattern of CRABP I expression includes specific rhombomeres of the hindbrain, neural crest cells and their derivatives the optic stalk, and the central area of the neural retina. We have created transgenic mouse lines with CRABP I 5' and transcribed regions fused to the lacZ structural gene that recapitulate much of this neural pattern of expression. Sequences 5' of the transcription initiation site between -7.8 and -3.2 kb confer beta-galactosidase expression to specific rhombomeres, migrating neural crest cells, trigeminal ganglion, the optic stalk, and the neural retina. We have also defined a region located between exon 1 and exon 8 that confers a portion of this expression pattern, including the mesencephalic projections of the trigeminal ganglion, the inner layer of the neural retina, and the peripheral layer of the posterior hindbrain. CRABP I expression in mesenchyme appears to require sequences in addition to or outside of those examined here.
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Affiliation(s)
- A L Means
- Department of Pharmacology, Cornell University Medical College, New York 10021, USA
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32
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Conway SJ, Henderson DJ, Copp AJ. Pax3 is required for cardiac neural crest migration in the mouse: evidence from the splotch (Sp2H) mutant. Development 1997; 124:505-14. [PMID: 9053326 DOI: 10.1242/dev.124.2.505] [Citation(s) in RCA: 224] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neural crest cells originating in the occipital region of the avian embryo are known to play a vital role in formation of the septum of the cardiac outflow tract and to contribute cells to the aortic arches, thymus, thyroid and parathyroids. This ‘cardiac’ neural crest sub-population is assumed to exist in mammals, but without direct evidence. In this paper we demonstrate, using RT-PCR and in situ hybridisation, that Pax3 expression can serve as a marker of cardiac neural crest cells in the mouse embryo. Cells of this lineage were traced from the occipital neural tube, via branchial arches 3, 4 and 6, into the aortic sac and aorto-pulmonary outflow tract. Confirmation that these Pax3-positive cells are indeed cardiac neural crest is provided by experiments in which hearts were deprived of a source of colonising neural crest, by organ culture in vitro, with consequent lack of up-regulation of Pax3. Occipital neural crest cell outgrowths in vitro were also shown to express Pax3. Mutation of Pax3, as occurs in the splotch (Sp2H) mouse, results in development of conotruncal heart defects including persistent truncus arteriosus. Homozygotes also exhibit defects of the aortic arches, thymus, thyroid and parathyroids. Pax3-positive neural crest cells were found to emigrate from the occipital neural tube of Sp2H/Sp2H embryos in a relatively normal fashion, but there was a marked deficiency or absence of neural crest cells traversing branchial arches 3, 4 and 6, and entering the cardiac outflow tract. This decreased expression of Pax3 in Sp2H/Sp2H embryos was not due to down-regulation of Pax3 in neural crest cells, as use of independent neural crest markers, Hoxa-3, CrabpI, Prx1, Prx2 and c-met also revealed a deficiency of migrating cardiac neural crest cells in homozygous embryos. This work demonstrates the essential role of the cardiac neural crest in formation of the heart and great vessels in the mouse and, furthermore, shows that Pax3 function is required for the cardiac neural crest to complete its migration to the developing heart.
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Affiliation(s)
- S J Conway
- Division of Cell and Molecular Biology, Institute of Child Health, University of London, UK
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33
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Abstract
Clinical trials demonstrate that up to 70% of neural tube defects (NTDs) can be prevented by folic acid supplementation in early pregnancy, whereas the remaining NTDs are resistant to folate. Here, we show that a second vitamin, myo-inositol, is capable of significantly reducing the incidence of spinal NTDs in curly tail mice, a genetic model of folate-resistant NTDs. Inositol increases flux through the inositol/lipid cycle, stimulating protein kinase C activity and upregulating expression of retinoic acid receptor beta, specifically in the caudal portion of the embryonic hindgut. This reduces the delay in closure of the posterior neuropore, the embryonic defect that is known to lead directly to spina bifida in curly tail embryos. Our findings reveal a molecular pathway of NTD prevention and suggest the possible efficacy of combined treatment with folate and inositol in overcoming the majority of human NTDs.
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Affiliation(s)
- N D Greene
- Neural Development Unit, Institute of Child Health, University of London, UK
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34
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The Role of Retinoids in Patterning Fish, Amphibian, and Chick Embryos. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1569-2590(08)60054-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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35
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36
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Maden M, Gale E, Kostetskii I, Zile M. Vitamin A-deficient quail embryos have half a hindbrain and other neural defects. Curr Biol 1996; 6:417-26. [PMID: 8723346 DOI: 10.1016/s0960-9822(02)00509-2] [Citation(s) in RCA: 247] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Retinoic acid (RA) is a morphogenetically active signalling molecule thought to be involved in the development of severely embryonic systems (based on its effect when applied in excess and the fact that it can be detected endogenously in embryos). Here, we adopt a novel approach and use the vitamin A-deficient (A-) quail embryo to ask what defects these embryos show when they develop in the absence of RA, with particular reference to the nervous system. RESULTS We have examined the anatomy, the expression domains of a variety of genes and the immunoreactivity to several antibodies in these A- embryos. In addition to the previously documented cardiovascular abnormalities, we find that the somites are smaller in A- embryos, otic vesicle development is abnormal and the somites continue up to and underneath the otic vesicle. In the central nervous system, we find that neural crest cells need RA for normal development and survival, and the neural tube fails to extend any neurites into the periphery. Using general hindbrain morphology and the expression patterns of Hoxa-2, Hoxb-1, Hoxb-4, Krox-20 and FGF-3 as markers, we conclude that segmentation in the myelencephalon (rhombomeres 4-8) is disrupted. In contrast, the dorsoventral axis of the neural tube using Shh, islet-1 and Pax-3 as markers is normal. CONCLUSIONS These results demonstrate at least three roles for RA in central nervous system development: neural crest survival, neurite outgrowth and hindbrain patterning.
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Affiliation(s)
- M Maden
- Developmental Biology Research Centre, King's College, London, UK.
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37
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Gale E, Prince V, Lumsden A, Clarke J, Holder N, Maden M. Late effects of retinoic acid on neural crest and aspects of rhombomere. Development 1996; 122:783-93. [PMID: 8631256 DOI: 10.1242/dev.122.3.783] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We exposed st.10 chicks to retinoic acid (RA), both globally, and locally to individual rhombomeres, to look at its role in specification of various aspects of hindbrain derived morphology. Previous studies have looked at RA exposure at earlier stages, during axial specification. Stage 10 is the time of morphological segmentation of the hindbrain and is just prior to neural crest migration. Rhombomere 4 localised RA injections result in specific alterations of pathways some crest cells that normally migrate to sites of differentiation of neurogenic derivatives. The r4 crest cells that give rise to mesenchymal derivatives are unaffected. In addition, r4 gene expression is also partially altered by RA; within 6 hours of r4 exposure to RA, ectopic expression of Krox-20 is seen in r4 and Hoxb-1 expression is lost while Hoxa-2 expression continues normally. When we examined these RA-treated animals later in development, they showed an anterior displacement of the facial ganglion in addition to a mis-direction of the extensions of its distal axons and a dramatic decrease in the number of contralateral vestibuloacoustic neurons normally seen in r4. Only this r4-specific neuronal type is affected in r4; the motor neuron projections seem normal in experimental animals. The specificity of this result, combined with the loss of Hoxb-1 expression in r4 and the work by Krumlauf and co-workers showing gain of contralateral neurons co-localised with ectopic Hoxb-1 expression, indicates a role for Hoxb-1 and RA in the specification of this cell type in normal development. These results suggest that RA, at st.10, is able to affect some aspects of segment identity while leaving others unchanged.
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Affiliation(s)
- E Gale
- Developmental Biology Research Centre, The Randall Institute, King's College London, UK
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