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Wang L, Zhao QF, Yang BB, Liang HJ, Zhang XE, Zhang XY, Yang WJ, Guo ZY, Xu X, Tian F, Wu QH. STAT3-EphA7 axis contributes to the progression of esophageal squamous cell carcinoma. Acta Oncol 2023; 62:1757-1766. [PMID: 37738252 DOI: 10.1080/0284186x.2023.2259601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 09/12/2023] [Indexed: 09/24/2023]
Abstract
BACKGROUND Our previous study has revealed that EphA7 was upregulated in patient-derived esophageal squamous cell carcinoma (ESCC) xenografts with hyper-activated STAT3, but its mechanism was still unclear. MATERIALS AND METHODS To assess the association between EphA7 and STAT3, western blotting, immunofluorescence, ChIP assay, and qRT-PCR were conducted. Truncated mutation and luciferase assay were performed to examine the promoter activity of EphA7. CCK-8 assay and colony formation were performed to assess the proliferation of ESCC. Cell-derived xenograft models were established to evaluate the effects of EphA7 on ESCC tumor growth. RNA-seq analyses were used to assess the effects of EphA7 on related signals. RESULTS In this study, EphA7 was found upregulated in ESCC cell lines with high STAT3 activation, and immunofluorescence also showed that EphA7 was co-localized with phospho-STAT3 in ESCC cells. Interestingly, suppressing STAT3 activation by the STAT3 inhibitor Stattic markedly inhibited the protein expression of EphA7 in ESCC cells, in contrast, activation of STAT3 by IL-6 obviously upregulated the protein expression of EphA7. Moreover, the transcription of EphA7 was also mediated by the activation of STAT3 in ESCC cells, and the -2000∼-1500 region was identified as the key promoter of EphA7. Our results also indicated that EphA7 enhanced the cell proliferation of ESCC, and silence of EphA7 significantly suppressed ESCC tumor growth. Moreover, EphA7 silence markedly abolished STAT3 activation-derived cell proliferation of ESCC. Additionally, RNA-seq analyses indicated that several tumor-related signaling pathways were significantly changed after EphA7 downregulation in ESCC cells. CONCLUSION Our results showed that the transcriptional expression of EphA7 was increased by activated STAT3, and the STAT3 signaling may act through EphA7 to promote the development of ESCC.
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Affiliation(s)
- Li Wang
- Department of Obstetrics and Gynecology, Center of Genetics and Prenatal Diagnosis, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, P. R. China
| | - Qiao-Feng Zhao
- Department of Pathophysiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, P. R. China
- Collaborative Innovation Center of Henan Province for Cancer Chemoprevention, Zhengzhou University, Zhengzhou, P. R. China
| | - Bing-Bing Yang
- Department of Pathophysiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, P. R. China
- Collaborative Innovation Center of Henan Province for Cancer Chemoprevention, Zhengzhou University, Zhengzhou, P. R. China
- State Key Laboratory of Esophageal Cancer Prevention and Treatment, Zhengzhou University, Zhengzhou, P. R. China
| | - Hui-Jie Liang
- Department of Pathophysiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, P. R. China
- Collaborative Innovation Center of Henan Province for Cancer Chemoprevention, Zhengzhou University, Zhengzhou, P. R. China
| | - Xian-E Zhang
- Department of Pathophysiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, P. R. China
- Collaborative Innovation Center of Henan Province for Cancer Chemoprevention, Zhengzhou University, Zhengzhou, P. R. China
- Second People's Hospital of Henan Province, Zhengzhou, P. R. China
| | - Xiao-Yan Zhang
- Department of Pathophysiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, P. R. China
- Collaborative Innovation Center of Henan Province for Cancer Chemoprevention, Zhengzhou University, Zhengzhou, P. R. China
| | - Wan-Jing Yang
- Department of Pathophysiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, P. R. China
- Collaborative Innovation Center of Henan Province for Cancer Chemoprevention, Zhengzhou University, Zhengzhou, P. R. China
| | - Zhi-Yu Guo
- SanQuan College of XinXiang Medical University, Xinxiang, P. R. China
| | - Xin Xu
- College of Biotechnology, Center for Self-Propelled Nanotechnologies, Suzhou Industrial Park Institute of Services Outsourcing, Suzhou, P. R. China
- Translational Cancer Research Laboratory, Suzhou Acumen Medical Technology, Suzhou, P. R. China
| | - Fang Tian
- Department of Pathophysiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, P. R. China
- Collaborative Innovation Center of Henan Province for Cancer Chemoprevention, Zhengzhou University, Zhengzhou, P. R. China
- State Key Laboratory of Esophageal Cancer Prevention and Treatment, Zhengzhou University, Zhengzhou, P. R. China
| | - Qing-Hua Wu
- Department of Obstetrics and Gynecology, Center of Genetics and Prenatal Diagnosis, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, P. R. China
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2
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Ligand-dependent EphA7 signaling inhibits prostate tumor growth and progression. Cell Death Dis 2017; 8:e3122. [PMID: 29022918 PMCID: PMC5682672 DOI: 10.1038/cddis.2017.507] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 08/08/2017] [Accepted: 08/17/2017] [Indexed: 01/02/2023]
Abstract
The downregulation of receptor tyrosine kinase EphA7 is frequent in epithelial cancers and linked to tumor progression. However, the detailed mechanism of EphA7-mediated prostate tumor progression remains elusive. To test the role of EphA7 receptor in prostate cancer (PCa) progression directly, we generated EphA7 receptor variants that were either lacking the cytoplasmic domain or carrying a point mutation that inhibits its phosphorylation by site-directed mutagenesis. Overexpression of wild-type (WT) EphA7 in PCa cells resulted in decreased tumor volume and increased tumor apoptosis in primary tumors. In addition, ectopic expression of WT EphA7 both can delay PCa cell proliferation and could inhibit PCa cell migration and invasion. This protein can also induce PCa cell apoptosis that correlated with increasing the protein expression levels of Bax, elevating the caspase-3 activities, reducing the protein expression levels of Bcl-2 and facilitating the dephosphorylation of Akt, which is further increased by the stimulation of ephrinA5-Fc. However, expression of these EphA7 mutants in PCa cells has no effect in vivo and in vitro. The expression of EphA7 and ephrinA5 was significantly decreased in PCa specimens compared with BPH tissues or paired normal tissues. Moreover, the phosphorylation of EphA7 was positively related with ephrinA5 expression in human prostate tissues. In sum, receptor phosphorylation of EphA7, at least in part, suppress PCa tumor malignancy through targeting PI3K/Akt signaling pathways.
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LI RONGHUI, SUN YINGYAN, JIANG AIYING, WU YAN, LI CHENGWEI, JIN MINGCHUN, YAN HAIRUN, JIN HONG. Knockdown of ephrin receptor A7 suppresses the proliferation and metastasis of A549 human lung cancer cells. Mol Med Rep 2016; 13:3190-6. [DOI: 10.3892/mmr.2016.4904] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 11/18/2015] [Indexed: 11/05/2022] Open
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Abstract
The subdivision of tissues into sharply demarcated regions with distinct and homogenous identity is an essential aspect of embryonic development. Along the anteroposterior axis of the vertebrate nervous system, this involves signaling which induces spatially restricted expression of transcription factors that specify regional identity. The spatial expression of such transcription factors is initially imprecise, with overlapping expression of genes that specify distinct identities, and a ragged border at the interface of adjacent regions. This pattern becomes sharpened by establishment of mutually exclusive expression of transcription factors, and by cell segregation that underlies formation of a straight border. In this review, we discuss studies of the vertebrate hindbrain which have revealed how discrete regional identity is established, the roles of Eph-ephrin signaling in cell segregation and border sharpening, and how cell identity and cell segregation are coupled.
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Bai YQ, Zhang JY, Bai CY, Xu XE, Wu JY, Chen B, Wu ZY, Wang SH, Shen J, Shen JH, Yao XD, Gao LZ, Wu B, Gu HL, Liu XH, Li X, Li EM, Xu LY. Low EphA7 Expression Correlated with Lymph Node Metastasis and Poor Prognosis of Patients with Esophageal Squamous Cell Carcinoma. Acta Histochem Cytochem 2015; 48:75-81. [PMID: 26160986 PMCID: PMC4491497 DOI: 10.1267/ahc.14054] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 04/20/2015] [Indexed: 02/05/2023] Open
Abstract
As a member of the Eph family of receptor tyrosine kinases, EphA7 plays an important role in cancer. However, the expression and significance of Eph receptors in esophageal squamous cell carcinoma (ESCC) remain unclear. Here, we detected the expression of EphA7 by immunohistochemistry in a sample of 352 patients with ESCC, and aimed to investigate the expression status of EphA7 in ESCC and its impact on prognosis. The results showed that low EphA7 expression significantly correlated with lymph node metastases (N0: 29%; N1: 64%. p<0.001), poor degree of tumor differentiation (G1: 31%; G2: 49%; G3: 58%. p=0.009) and pTNM staging (I+II: 33%; III+IV: 58%. p<0.001). Furthermore, in a combined analysis, patients with low EphA7-expressing tumors showed a shorter overall survival than those with high expression, resulting in a five-year overall survival rate of 47.4% vs. 52.6%, respectively (p=0.016). Consequently, patients with a low EphA7 expression have poorer prognosis in ESCC compared with those manifesting high expression.
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Affiliation(s)
- Yu-Qin Bai
- Department of Pathology, Medical College of Chifeng University
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
| | - Jun-Yi Zhang
- Department of Pathology, Medical College of Chifeng University
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
| | - Chun-Ying Bai
- Research Centre of Molecular Medicine, Medical College of Chifeng University
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
| | - Xiu-E Xu
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
- Institute of Oncologic Pathology, Medical College of Shantou University
| | - Jian-Yi Wu
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
- Department of Biochemistry and Molecular Biology, Medical College of Shantou University, Shantou 515041, China
| | - Bo Chen
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
- Institute of Oncologic Pathology, Medical College of Shantou University
| | - Zhi-Yong Wu
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
- Department of Pathology, Shantou Central Hospital, Affiliated Shantou Hospital of Sun Yat-sen University
| | - Shao-Hong Wang
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
- Oncology Surgery, Shantou Central Hospital, Affiliated Shantou Hospital of Sun Yat-sen University, Shantou 515041, China
| | - Jian Shen
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
- Institute of Oncologic Pathology, Medical College of Shantou University
| | - Jin-Hui Shen
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
- Oncology Surgery, Shantou Central Hospital, Affiliated Shantou Hospital of Sun Yat-sen University, Shantou 515041, China
| | - Xiao-Dong Yao
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
- Department of Pathology, Shantou Central Hospital, Affiliated Shantou Hospital of Sun Yat-sen University
| | - Lian-Zhu Gao
- Department of Pathology, The Second Hospital of Chifeng City, Chifeng 024000, China
| | - Bao Wu
- Department of Histology and Embryology, Medical College of Chifeng University, Chifeng 024000, China
| | - Hong-Li Gu
- Department of Pediatrics, Affiliated Hospital of Chifeng University, Chifeng 024000, China
| | - Xiao-Hui Liu
- Department of Pathology, Medical College of Chifeng University
| | - Xin Li
- Department of Pathology, Medical College of Chifeng University
| | - En-Min Li
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
| | - Li-Yan Xu
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College
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6
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Willaredt MA, Schlüter T, Nothwang HG. The gene regulatory networks underlying formation of the auditory hindbrain. Cell Mol Life Sci 2015; 72:519-535. [PMID: 25332098 PMCID: PMC11113740 DOI: 10.1007/s00018-014-1759-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/24/2014] [Accepted: 10/09/2014] [Indexed: 01/28/2023]
Abstract
Development and evolution of auditory hindbrain nuclei are two major unsolved issues in hearing research. Recent characterization of transgenic mice identified the rhombomeric origins of mammalian auditory nuclei and unraveled genes involved in their formation. Here, we provide an overview on these data by assembling them into rhombomere-specific gene regulatory networks (GRNs), as they underlie developmental and evolutionary processes. To explore evolutionary mechanisms, we compare the GRNs operating in the mammalian auditory hindbrain with data available from the inner ear and other vertebrate groups. Finally, we propose that the availability of genomic sequences from all major vertebrate taxa and novel genetic techniques for non-model organisms provide an unprecedented opportunity to investigate development and evolution of the auditory hindbrain by comparative molecular approaches. The dissection of the molecular mechanisms leading to auditory structures will also provide an important framework for auditory processing disorders, a clinical problem difficult to tackle so far. These data will, therefore, foster basic and clinical hearing research alike.
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Affiliation(s)
- Marc A Willaredt
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
| | - Tina Schlüter
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Hans Gerd Nothwang
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
- Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
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7
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The emerging framework of mammalian auditory hindbrain development. Cell Tissue Res 2015; 361:33-48. [DOI: 10.1007/s00441-014-2110-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 12/22/2014] [Indexed: 02/06/2023]
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8
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Kita EM, Scott EK, Goodhill GJ. Topographic wiring of the retinotectal connection in zebrafish. Dev Neurobiol 2015; 75:542-56. [PMID: 25492632 DOI: 10.1002/dneu.22256] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/03/2014] [Accepted: 12/08/2014] [Indexed: 11/08/2022]
Abstract
The zebrafish retinotectal projection provides an attractive model system for studying many aspects of topographic map formation and maintenance. Visual connections initially start to form between 3 and 5 days postfertilization, and remain plastic throughout the life of the fish. Zebrafish are easily manipulated surgically, genetically, and chemically, and a variety of molecular tools exist to enable visualization and control of various aspects of map development. Here, we review zebrafish retinotectal map formation, focusing particularly on the detailed structure and dynamics of the connections, the molecules that are important in map creation, and how activity regulates the maintenance of the map.
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Affiliation(s)
- Elizabeth M Kita
- Queensland Brain Institute, The University of Queensland, Brisbane QLD 4072, Australia
| | - Ethan K Scott
- School of Biomedical Sciences, The University of Queensland, Brisbane QLD 4072, Australia
| | - Geoffrey J Goodhill
- Queensland Brain Institute, The University of Queensland, Brisbane QLD 4072, Australia.,School of Mathematics and Physics, The University of Queensland, Brisbane QLD 4072, Australia
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9
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LU YUCHENG, HENG XUEYUAN, YU JIXU, SU QUANPING, GUAN XIANGHONG, YOU CUIPING, WANG LONG, CHE FENGYUAN. miR-137 regulates the migration of human umbilical vein endothelial cells by targeting ephrin-type A receptor 7. Mol Med Rep 2014; 10:1475-80. [DOI: 10.3892/mmr.2014.2319] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 03/04/2014] [Indexed: 11/06/2022] Open
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10
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Philippidou P, Dasen JS. Hox genes: choreographers in neural development, architects of circuit organization. Neuron 2013; 80:12-34. [PMID: 24094100 DOI: 10.1016/j.neuron.2013.09.020] [Citation(s) in RCA: 263] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The neural circuits governing vital behaviors, such as respiration and locomotion, are comprised of discrete neuronal populations residing within the brainstem and spinal cord. Work over the past decade has provided a fairly comprehensive understanding of the developmental pathways that determine the identity of major neuronal classes within the neural tube. However, the steps through which neurons acquire the subtype diversities necessary for their incorporation into a particular circuit are still poorly defined. Studies on the specification of motor neurons indicate that the large family of Hox transcription factors has a key role in generating the subtypes required for selective muscle innervation. There is also emerging evidence that Hox genes function in multiple neuronal classes to shape synaptic specificity during development, suggesting a broader role in circuit assembly. This Review highlights the functions and mechanisms of Hox gene networks and their multifaceted roles during neuronal specification and connectivity.
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Affiliation(s)
- Polyxeni Philippidou
- Howard Hughes Medical Institute, NYU Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA.
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11
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Stein E, Schoecklmann H, Daniel TO. Eph family receptors and ligands in vascular cell targeting and assembly. Trends Cardiovasc Med 2012; 7:329-34. [PMID: 21235905 DOI: 10.1016/s1050-1738(97)00095-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Members of the Eph family of receptor tyrosine kinases determine neural cell aggregation and targeting behavior, functions that are also critical in vascular assembly and remodeling. Among this class of diverse receptors, EphA2 (Eck) and EphB1 (ELK) represent prototypes for two receptor subfamilies distinguished by high-affinity interaction with either glycerophosphatidylinositol (GPI)-linked or transmembrane ligands, respectively. EphA2 participates in angiogenic responses to tumor necrosis factor (TNF) through an autocrine loop affecting endothelial cell migration. EphB1 and its ligand Ephrin-B1 (LERK-2) are important determinants of assembly of endothelial cells from the microvasculature of the kidney, where both are expressed in endothelial progenitors and in glomerular microvascular endothelial cells. Ephrin-B1 activation of EphB1 promotes assembly of these cells into capillary-like structures. Interaction trap approaches have identified downstream signaling proteins that complex with ligand-activated EphA2 or EphB1, including nonreceptor tyrosine kinases and SH2 domain-containing adapter proteins. The Grb 10 adapter is one of a subset that binds activated EphB1, but not EphA2, defining distinct signaling mechanisms for these related endothelial receptors. On the basis of observations in vascular endothelial cells and recent results defining Eph receptor and ligand roles in neural cell targeting, we propose that these receptors direct cell-cell recognition events that are critical in vasculogenesis and angiogenesis. (Trends Cardiovasc Med 1997;7:329-334). © 1997, Elsevier Science Inc.
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Affiliation(s)
- E Stein
- Department of Pharmacology, Nashville, Tennessee, USA
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12
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Dearborn RE, Dai Y, Reed B, Karian T, Gray J, Kunes S. Reph, a regulator of Eph receptor expression in the Drosophila melanogaster optic lobe. PLoS One 2012; 7:e37303. [PMID: 22615969 PMCID: PMC3353934 DOI: 10.1371/journal.pone.0037303] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 04/19/2012] [Indexed: 11/19/2022] Open
Abstract
Receptors of the Eph family of tyrosine kinases and their Ephrin ligands are involved in developmental processes as diverse as angiogenesis, axon guidance and cell migration. However, our understanding of the Eph signaling pathway is incomplete, and could benefit from an analysis by genetic methods. To this end, we performed a genetic modifier screen for mutations that affect Eph signaling in Drosophila melanogaster. Several dozen loci were identified on the basis of their suppression or enhancement of an eye defect induced by the ectopic expression of Ephrin during development; many of these mutant loci were found to disrupt visual system development. One modifier locus, reph (regulator of eph expression), was characterized in molecular detail and found to encode a putative nuclear protein that interacts genetically with Eph signaling pathway mutations. Reph is an autonomous regulator of Eph receptor expression, required for the graded expression of Eph protein and the establishment of an optic lobe axonal topographic map. These results reveal a novel component of the regulatory pathway controlling expression of eph and identify reph as a novel factor in the developing visual system.
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Affiliation(s)
- Richard E Dearborn
- Department of Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York, United States of America.
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Arvanitis DN, Davy A. Regulation and misregulation of Eph/ephrin expression. Cell Adh Migr 2012; 6:131-7. [PMID: 22568953 DOI: 10.4161/cam.19690] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The erythropoietin-producing hepatocellular (Eph) receptors form the largest family of receptor tyrosine kinases. Upon interaction of the Eph receptors with their ligands the ephrins, signaling cascades are initiated downstream of both receptor and ligand, a feature known as bidirectional signaling. The Eph receptors and ephrin ligands mediate important roles in embryonic development, particularly in establishing tissue organization by mediating cell adhesion or cell repulsion. In several adult tissues, at least one Eph/ephrin pair is found to play critical roles in tissue physiology and homeostasis. In recent years numerous members of this family have gained considerable attention since changes in their expression levels are a typical feature in cancer cells. Despite the fact that Eph/ephrin developmental expression profiles are well documented, little is known on transcriptional and post-transcriptional mechanisms that permits their highly specific, graded, complementary or overlapping expression patterns. Therefore understanding the transcriptional and post-transcriptional mechanisms regulating Eph/ephrin expression has far-reaching significance in biology. This review provides an overview of the mechanisms regulating Eph/ephrin expression. We highlight important emerging mechanisms of Eph/ephrin regulation or misregulation such as epigenetics and miRNAs.
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Affiliation(s)
- Dina N Arvanitis
- Centre de Biologie du Développement, CNRS, Université de Toulouse, Toulouse, France
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14
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Saeger BM, Suhm M, Neubüser A. Ephrin/ephrin receptor expression during early stages of mouse inner ear development. Dev Dyn 2011; 240:1578-85. [DOI: 10.1002/dvdy.22632] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2011] [Indexed: 12/30/2022] Open
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Kim YJ, Park SC. Identification of EphA7 BAC clone containing a long-range dorsal midline-specific enhancer. BMB Rep 2011; 44:113-7. [DOI: 10.5483/bmbrep.2011.44.2.113] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
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16
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Baas D, Malbouyres M, Haftek-Terreau Z, Le Guellec D, Ruggiero F. Craniofacial cartilage morphogenesis requires zebrafish col11a1 activity. Matrix Biol 2009; 28:490-502. [PMID: 19638309 DOI: 10.1016/j.matbio.2009.07.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 07/14/2009] [Accepted: 07/17/2009] [Indexed: 11/26/2022]
Abstract
The zebrafish ortholog of the human COL11A1 gene encoding the cartilage collagen XI proalpha1 chain was characterized to explore its function in developing zebrafish using the morpholino-based knockdown strategy. We showed that its expression in zebrafish is developmentally regulated. A low expression level was detected by real-time PCR during the early stages of development. At 24 hpf, a sharp peak of expression was observed. At that stage, in situ hybridization indicated that col11a1 transcripts are restricted to notochord. At 48 hpf, they were exclusively detected in the craniofacial skeleton, endoskeleton of pectoral fins and in otic vesicles. Collagen XI alpha1-deficient zebrafish embryos developed defects in craniofacial cartilage formation and in notochord morphology. Neural crest specification and mesenchymal condensation occurred normally in morpholino-injected embryos. Col11a1 depletion affected the spatial organization of chondrocytes, the shaping of cartilage elements, and the maturation of chondrocytes to hypertrophy. Knockdown of col11a1 in embryos stimulated the expression of the marker of chondrocyte differentiation col2a1, resulting in the deposit of abnormally thick and sparse fibrils in the cartilage extracellular matrix. The extracellular matrix organization of the perichordal sheath was also altered and led to notochord distortion. The data underscore the importance of collagen XI in the development of a functional cartilage matrix. Moreover, the defects observed in cartilage formation resemble those observed in human chondrodysplasia such as the Stickler/Marshall syndrome. Zebrafish represent a novel reliable vertebrate model for collagen XI collagenopathies.
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Desmazières A, Charnay P, Gilardi-Hebenstreit P. Krox20 controls the transcription of its various targets in the developing hindbrain according to multiple modes. J Biol Chem 2009; 284:10831-40. [PMID: 19218566 DOI: 10.1074/jbc.m808683200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The zinc finger transcription factor Krox20 plays an essential role in the vertebrate hindbrain segmentation process. It positively or negatively controls a large variety of other regulatory genes, coordinating delimitation of segmental territories, specification of their identity, and maintenance of their integrity. We have investigated the molecular mechanisms of Krox20 transcriptional control by performing a detailed structure-function analysis of the protein in the developing chick hindbrain. This revealed an unsuspected diversity in the modes of action of a transcription factor in a single tissue, since regulation of each of the five tested target genes requires different parts of the protein and/or presumably different co-factors. The multiplicity of Krox20 functions might rely on this diversity. Investigation of known Krox20 co-factors was initiated in relation to this analysis. Nab was shown to act as a negative feedback modulator of the different Krox20 activating functions in the hindbrain. HCF-1 was found to bind to a Krox20 N-terminal region, which was shown to rely on multiple elements, including acidic domains, to convey Nab activation and Krox20 autoregulation.
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18
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Narita Y, Rijli FM. Hox genes in neural patterning and circuit formation in the mouse hindbrain. Curr Top Dev Biol 2009; 88:139-67. [PMID: 19651304 DOI: 10.1016/s0070-2153(09)88005-8] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The mammalian hindbrain is the seat of regulation of several vital functions that involve many of the organ systems of the body. Such functions are controlled through the activity of intricate arrays of neuronal circuits and connections. The establishment of ordered patterns of neuronal specification, migration, and axonal topographic connectivity during development is crucial to build such a complex network of circuits and functional connectivity in the mature hindbrain. The early development of the vertebrate hindbrain proceeds according to a fundamental metameric partitioning along the anteroposterior axis into cellular compartments known as rhombomeres. Such an organization has been highly conserved in vertebrate evolution and has a fundamental impact on the hindbrain adult structure, nuclear organization, and connectivity. Here, we review the cellular and molecular mechanisms underlying hindbrain neuronal circuitry in the mouse, with a specific focus on the role of the homeodomain transcription factors of the Hox gene family. The Hox genes are crucial determinants of rhombomere segmental identity and anteroposterior patterning. However, recent findings suggest that, in addition to their well-known roles at early embryonic stages, the Hox genes may play important roles also in later aspect of neuronal circuit development, including stereotypic neuronal migration, axon pathfinding, and topographic mapping of connectivity.
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Affiliation(s)
- Yuichi Narita
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
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19
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Reynaud C, Baas D, Gleyzal C, Le Guellec D, Sommer P. Morpholino knockdown of lysyl oxidase impairs zebrafish development, and reflects some aspects of copper metabolism disorders. Matrix Biol 2008; 27:547-60. [PMID: 18467084 DOI: 10.1016/j.matbio.2008.03.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Revised: 03/11/2008] [Accepted: 03/12/2008] [Indexed: 12/11/2022]
Abstract
Lysyl oxidase (LOX), a copper-dependent amine oxidase known in mammals to catalyze the cross-linking of collagen and elastin in the extracellular matrix, is a member of a multigenic family. Eight genes encoding lysyl oxidase isoforms have been identified in zebrafish. Recent studies have revealed a critical role for two zebrafish lysyl oxidases-like in the formation of the notochord. We now present the role of Lox in zebrafish development. lox morpholino-mediated knockdown results in a mildly undulated notochord, truncated anterior-posterior axis, tail bending and smaller head. Analyses of morphants show a complete disorganization of muscle somites and neural defects, in accordance with the lox expression pattern. Lox inhibition also induces pigment defects and pharyngeal arch deformities consistent with neural crest dysfunction. Taken together, these data reveal a role for Lox in early morphogenesis, especially in muscle development and neurogenesis, and resume some aspects of physiopathology of copper metabolism.
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Affiliation(s)
- Caroline Reynaud
- IBCP, Institut de Biologie et Chimie des Protéines, Lyon, France.
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20
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Wang LF, Fokas E, Juricko J, You A, Rose F, Pagenstecher A, Engenhart-Cabillic R, An HX. Increased expression of EphA7 correlates with adverse outcome in primary and recurrent glioblastoma multiforme patients. BMC Cancer 2008; 8:79. [PMID: 18366728 PMCID: PMC2292196 DOI: 10.1186/1471-2407-8-79] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Accepted: 03/25/2008] [Indexed: 12/19/2022] Open
Abstract
Background Malignant gliomas are lethal cancers, highly dependent on angiogenesis and treatment options and prognosis still remain poor for patients with recurrent glioblastoma multiforme (GBM). Ephs and ephrins have many well-defined functions during embryonic development of central nervous system such as axon mapping, neural crest cell migration, hindbrain segmentation and synapse formation as well as physiological and abnormal angiogenesis. Accumulating evidence indicates that Eph and ephrins are frequently overexpressed in different tumor types including GBM. However, their role in tumorigenesis remains controversial, as both tumor growth promoter and suppressor potential have been ascribed to Eph and ephrins while the function of EphA7 in GBM pathogenesis remains largely unknown. Methods In this study, we investigated the immunohistochemical expression of EphA7 in a series of 32 primary and recurrent GBM and correlated it with clinical pathological parameters and patient outcome. In addition, intratumor microvascular density (MVD) was quantified by immunostaining for endothelial cell marker von Willebrand factor (vWF). Results Overexpression of EphA7 protein was predictive of the adverse outcome in GBM patients, independent of MVD expression (p = 0.02). Moreover, high density of MVD as well as higher EphA7 expression predicted the disease outcome more accurately than EphA7 variable alone (p = 0.01). There was no correlation between MVD and overall survival or recurrence-free survival (p > 0.05). However, a statistically significant correlation between lower MVD and tumor recurrence was observed (p = 0.003). Conclusion The immunohistochemical assessment of tissue EphA7 provides important prognostic information in GBM and would justify its use as surrogate marker to screen patients for tyrosine kinase inhibitor therapy.
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Affiliation(s)
- Lin-Fang Wang
- Department of Radiotherapy and Radiation Oncology, Philipps-University Marburg, Baldingerstr, D-35043 Marburg, Germany.
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21
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Figueroa JD, Benton RL, Velazquez I, Torrado AI, Ortiz CM, Hernandez CM, Diaz JJ, Magnuson DS, Whittemore SR, Miranda JD. Inhibition of EphA7 up-regulation after spinal cord injury reduces apoptosis and promotes locomotor recovery. J Neurosci Res 2007; 84:1438-51. [PMID: 16983667 DOI: 10.1002/jnr.21048] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Functional impairment after spinal cord injury (SCI) is partially attributed to neuronal cell death, with further degeneration caused by the accompanying apoptosis of myelin-forming oligodendrocytes. The Eph receptor protein tyrosine kinase family and its cognate ligands, the ephrins, have been identified to be involved in axonal outgrowth, synapse formation, and target recognition, mainly mediated by repulsive activity. Recent reports suggest that ephrin/Eph signaling might also play a role as a physiological trigger for apoptosis during embryonic development. Here, we investigated the expression profile of EphA7, after SCI, by using a combination of quantitative real-time PCR (QRT-PCR) and immunohistochemical techniques. QRT-PCR analysis showed an increase in the expression of full-length EphA7 at 7 days postinjury (DPI). Receptor immunoreactivity was shown mostly in astrocytes of the white matter at the injury epicenter. In control animals, EphA7 expression was observed predominantly in motor neurons of the ventral gray matter, although some immunoreactivity was seen in white matter. Furthermore, blocking the expression of EphA7 after SCI using antisense oligonucleotides resulted in significant acceleration of hindlimb locomotor recovery at 1 week. This was a transient effect; by 2 weeks postinjury, treated animals were not different from controls. Antisense treatment also produced a return of nerve conduction, with shorter latencies than in control treated animals after transcranial magnetic stimulation. We identified EphA7 receptors as putative regulators of apoptosis in the acute phase after SCI. These results suggest a functional role for EphA7 receptors in the early stages of SCI pathophysiology.
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Affiliation(s)
- Johnny D Figueroa
- Department of Physiology, University of Puerto Rico Medical Science Campus, San Juan, Puerto Rico
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22
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García-Calero E, de Puelles E, Puelles L. EphA7 receptor is expressed differentially at chicken prosomeric boundaries. Neuroscience 2006; 141:1887-97. [PMID: 16844303 DOI: 10.1016/j.neuroscience.2006.04.074] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Revised: 04/05/2006] [Accepted: 04/07/2006] [Indexed: 10/24/2022]
Abstract
We reexamined tyrosine-kinase receptor EphA7 RNA signal in embryonic chicken forebrain, to clarify its topographic relationships with early regionalization processes, such as establishment of prosomeric boundaries. After neurulation, uniform alar expression appears across prospective prosomeres prosomere 1, prosomere 2 and prosomere 3 (prethalamus, thalamus and pretectum). This pattern soon changes by differential downregulation at or in between some of the prosomeric boundaries in an individual pattern for each limit, and by expansion of expression into the rostral midbrain. The secondary distribution highlights various transversal and longitudinal domains, notably the zona limitans intrathalamica and the pretectum limits, as well as two longitudinal bands in the basal plate, termed paramedian and parabasal. Strong expression of EphA7 appears at the mammillary pouch and a supramammillary tegmental arch from stage Hamburger and Hamilton stages 14-15 onwards. At the end of the developmental period examined, expression of EphA7 in the ventricular zone decreases generally (with some exceptions) and novel expression domains start to appear in the mantle layer, initiating a third phase of differential expression. Thus, while the expression of EphA7 does not show a fixed functional or topographic relationship to prosomeric boundaries, sequential transcription changes during chicken development are consistent with a differential involvement of the diverse interprosomeric boundaries, as well as dorsoventral patterning organizers, in the regulation of EphA7 expression.
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Affiliation(s)
- E García-Calero
- Department of Human Anatomy and Psychobiology, School of Medicine, University of Murcia (Campus Espinardo), E30100 Murcia, Spain
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23
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Akin ZN, Nazarali AJ. Hox genes and their candidate downstream targets in the developing central nervous system. Cell Mol Neurobiol 2005; 25:697-741. [PMID: 16075387 DOI: 10.1007/s10571-005-3971-9] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Accepted: 04/14/2004] [Indexed: 12/14/2022]
Abstract
1. Homeobox (Hox) genes were originally discovered in the fruit fly Drosophila, where they function through a conserved homeodomain as transcriptional regulators to control embryonic morphogenesis. Since then over 1000 homeodomain proteins have been identified in several species. In vertebrates, 39 Hox genes have been identified as homologs of the original Drosophila complex, and like their Drosophila counterparts they are organized within chromosomal clusters. Vertebrate Hox genes have also been shown to play a critical role in embryonic development as transcriptional regulators. 2. Both the Drosophila and vertebrate Hox genes have been shown to interact with various cofactors, such as the TALE homeodomain proteins, in recognition of consensus sequences within regulatory elements of their target genes. These protein-protein interactions are believed to contribute to enhancing the specificity of target gene recognition in a cell-type or tissue- dependent manner. The regulatory activity of a particular Hox protein on a specific regulatory element is highly variable and dependent on its interacting partners within the transcriptional complex. 3. In vertebrates, Hox genes display spatially restricted patterns of expression within the developing CNS, both along the anterioposterior and dorsoventral axis of the embryo. Their restricted gene expression is suggestive of a regulatory role in patterning of the CNS, as well as in cell specification. Determining the precise function of individual Hox genes in CNS morphogenesis through classical mutational analyses is complicated due to functional redundancy between Hox genes. 4. Understanding the precise mechanisms through which Hox genes mediate embryonic morphogenesis requires the identification of their downstream target genes. Although Hox genes have been implicated in the regulation of several pathways, few target genes have been shown to be under their direct regulatory control. Development of methodologies used for the isolation of target genes and for the analysis of putative targets will be beneficial in establishing the genetic pathways controlled by Hox factors. 5. Within the developing CNS various cell adhesion molecules and signaling molecules have been identified as candidate downstream target genes of Hox proteins. These targets play a role in processes such as cell migration and differentiation, and are implicated in contributing to neuronal processes such as plasticity and/or specification. Hence, Hox genes not only play a role in patterning of the CNS during early development, but may also contribute to cell specification and identity.
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Affiliation(s)
- Z N Akin
- Laboratory of Molecular Biology, College of Pharmacy and Nutrition, University of Saskatchewan, 116 Thorvaldson Building, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada
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24
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Wada N, Tanaka H, Ide H, Nohno T. Ephrin-A2 regulates position-specific cell affinity and is involved in cartilage morphogenesis in the chick limb bud. Dev Biol 2003; 264:550-63. [PMID: 14651937 DOI: 10.1016/j.ydbio.2003.08.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the developing limb bud, mesenchymal cells show position-specific affinity, suggesting that the positional identity of the cells is represented as their surface properties. Since the affinity is regulated by glycosylphosphatidylinositol (GPI)-anchored cell surface proteins, and by EphA4 receptor tyrosine kinase, we hypothesized that the GPI-anchored ligand, the ephrin-A family, also contributes to the affinity. Here, we describe the role of ephrin-A2 in the chick limb bud. Ephrin-A2 protein is uniformly distributed in the limb bud during early limb development. As the limb bud grows, expression of ephrin-A2 is strong in its proximal-to-intermediate regions, but weak distally. The position-dependent expression is maintained in vitro, and is regulated by FGF protein, which is produced in the apical ectodermal ridge. To investigate the role of ephrin-A2 in affinity and in cartilage morphogenesis of limb mesenchyme, we ectopically expressed ephrin-A2 in the limb bud using the retrovirus vector, RCAS. Overexpressed ephrin-A2 modulated the affinity of the mesenchymal cells that differentiate into autopod elements. It also caused malformation of the autopod skeleton and interfered with cartilage nodule formation in vitro without inhibiting chondrogenesis. These results suggest that ephrin-A2 regulates the position-specific affinity of limb mesenchyme and is involved in cartilage pattern formation in the limb.
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Affiliation(s)
- Naoyuki Wada
- Department of Molecular Biology, Kawasaki Medical School, 577 Matsushima, Kurashiki City 701-0192, Japan
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25
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Abstract
The Eph family of receptor tyrosine kinases and their ligands, the ephrins, are membrane-bound proteins that mediate bidirectional signals between adjacent cells. By modulating cytoskeleton dynamics affecting cell motility and adhesion, Ephs and ephrins orchestrate cell movements during multiple morphogenetic processes, including gastrulation, segmentation, angiogenesis, axonal pathfinding, and neural crest cell migration. The full repertoire of developmental Eph/ephrin functions remains uncertain, however, because coexpression of multiple receptor and ligand family members, and promiscuous interactions between them, can result in functional redundancy. A complete understanding of expression patterns, therefore, is a necessary prerequisite to understanding function. Here, we present a comprehensive expression overview for 10 Eph and ephrin genes during the first 48 hr of chick embryo development. First, dynamic expression domains are described for each gene between Hamburger and Hamilton stages 4 and 12; second, comparative analyses are presented of Eph/ephrin expression patterns in the primitive streak, the somites, the vasculature, and the brain. Complex spatially and temporally dynamic expression patterns are revealed that suggest novel functions for Eph and ephrin family members in both known and previously unrecognized processes. This study will provide a valuable resource for further experimental investigations of Eph and ephrin functions during early embryonic development.
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Affiliation(s)
- Robert K Baker
- Department of Cell Biology and Anatomy, University of Arizona, Tucson, Arizona 85724, USA
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26
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Hunt R, Hunt PN. The role of cell mixing in branchial arch development. Mech Dev 2003; 120:769-90. [PMID: 12915228 DOI: 10.1016/s0925-4773(03)00070-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Compartmental structures are the basis of a number of developing systems, including parts of the vertebrate head. One of the characteristics of a series of compartments is that mixing between cells in adjacent units is restricted. This is a consequence of differential chemoaffinity between neighbouring cells in adjacent compartments. We set out to determine whether mesenchymal cells in the branchial arches and their precursors show cell-mixing properties consistent with a compartmental organisation. In chimaeric avian embryos we found no evidence of preferential association or segregation of neural crest cells when surrounded by cells derived from a different axial level. In reassociation assays using mesenchymal cells isolated from chick branchial arches at stage 18, cells reformed into clusters without exhibiting a preferential affinity for cells derived from the same branchial arch. We find no evidence for differential chemoaffinity in vivo or in vitro between mesenchymal cells in different branchial arches. Our findings suggest that branchial arch mesenchyme is not organised into a series of compartments.
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Affiliation(s)
- Romita Hunt
- School of Biological and Biomedical Sciences, University of Durham, South Road, DH1 3LE Durham, UK
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27
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Hahn AC, Emmons SW. The roles of an ephrin and a semaphorin in patterning cell-cell contacts in C. elegans sensory organ development. Dev Biol 2003; 256:379-88. [PMID: 12679110 DOI: 10.1016/s0012-1606(02)00129-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ephrins and semaphorins regulate a wide variety of developmental processes, including axon guidance and cell migration. We have studied the roles of the ephrin EFN-4 and the semaphorin MAB-20 in patterning cell-cell contacts among the cells that give rise to the ray sensory organs of Caenorhabditis elegans. In wild-type, contacts at adherens junctions form only between cells belonging to the same ray. In efn-4 and mab-20 mutants, ectopic contacts form between cells belonging to different rays. Ectopic contacts also occur in mutants in regulatory genes that specify ray morphological identity. We used efn-4 and mab-20 reporters to investigate whether these ray identity genes function through activating expression of efn-4 or mab-20 in ray cells. mab-20 reporter expression in ray cells was unaffected by mutants in the Pax6 homolog mab-18 and the Hox genes egl-5 and mab-5, suggesting that these genes do not regulate mab-20 expression. We find that mab-18 is necessary for activating efn-4 reporter expression, but this activity alone is not sufficient to account for mab-18 function in controlling cell-cell contact formation. In egl-5 mutants, efn-4 reporter expression in certain ray cells was increased, inconsistent with a simple repulsion model for efn-4 action. The evidence indicates that ray identity genes primarily regulate ray morphogenesis by pathways other than through regulation of expression of semaphorin and ephrin.
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Affiliation(s)
- Andrew C Hahn
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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28
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Koo J, Shim S, Gu C, Yoo O, Park S. Identification of an enhancer region in the mouse ephA8 locus directing expression to the anterior region of the dorsal mesencephalon. Dev Dyn 2003; 226:596-603. [PMID: 12666197 DOI: 10.1002/dvdy.10253] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Eph receptors and ephrins are dynamically expressed in a wide range of regions of the vertebrate during embryogenesis. The dorsal mesencephalon appears to be segmented into two broad regions demarcated by the mutually exclusive expression of EphA receptors and ephrinA ligands. It is of considerable interest to elucidate how these expression domains are established in the development of the mesencephalon. In this study, we used a transgenic approach to define the cis-acting DNA regulatory elements involved in the anterior mesencephalon-specific expression of the mouse ephA8 gene. Our analyses of the temporal and spatial expression patterns of various ephA8/lacZ gene fusions in transgenic mice revealed that the 10-kb genomic DNA 5' immediately upstream of the ephA8 coding sequence is capable of directing lacZ expression in an ephA8-specific manner. Further deletion analyses of the ephA8 genomic region led to the identification of a 1-kb enhancer region, which directs expression in the embryo to the anterior region of the developing midbrain. This ephA8-specific regulatory DNA sequences can now be used in biochemical analyses to identify proteins modulating the anterior differentiation of the optic tectum, and in functional analyses to direct the expression of other developmentally important genes to this region.
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Affiliation(s)
- Jashin Koo
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong-gu, Taejon, Korea
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29
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Miyamoto T, Sengoku K, Takuma N, Hasuike S, Hayashi H, Yamauchi T, Yamashita T, Ishikawa M. Isolation and expression analysis of the testis-specific gene, STRA8, stimulated by retinoic acid gene 8. J Assist Reprod Genet 2002; 19:531-5. [PMID: 12489526 PMCID: PMC3455343 DOI: 10.1023/a:1020963919596] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Retinoids are known to be required for vertebrate reproduction, and in the male, for the maintenance of normal testicular structure and function. Previously several novel retinoic acid responsive genes, collectively designated as the Stra genes, had been isolated in the mouse. The Stra8 gene encodes a cytoplasmic protein and is expressed specific to the developing male gonad during mouse embryogenesis. In adult mouse, its expression is restricted to the premeiotic germ cells. Thus it has been suggested that the mouse Stra8 protein may play a role in the premeiotic phase of spermatogenesis. Recently a lot of genes that are expressed only in male germ cells have been isolated in the mouse. The mouse Stra8, Rnh2, Piwil2, Tex17, and Tuba7 were identified as testis-specific expressed genes. In addition, the Figla was known to be a testis- and ovary-specific gene. Recently we had reported the isolation of the human RNH2 cDNA and its expression, which is limited to the human testis. In the present study, we have isolated full-length cDNA of S TRA8 and partial cDNAs of PIWIL2, FIGLA, TEX17, and TUBA7, and analyzed their expression patterns in human tissues.
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Affiliation(s)
- Toshinobu Miyamoto
- Department of Obstetrics and Gynecology, Asahikawa Medical College, Hokkaido, Japan.
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30
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Munthe E, Aasheim HC. Characterization of the human ephrin-A4 promoter. Biochem J 2002; 366:447-58. [PMID: 12030849 PMCID: PMC1222801 DOI: 10.1042/bj20011693] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2001] [Revised: 04/19/2002] [Accepted: 05/24/2002] [Indexed: 01/25/2023]
Abstract
Expression of the ephrin-A4 ligand, a family member of ligands binding the Eph receptor tyrosine kinases, is induced after an antigen-receptor stimulation of lymphocytes. To understand the transcription regulation of the ephrin-A4 gene, its promoter was identified and regulating elements were characterized. The ephrin-A4 promoter contains cis elements directing the cell-specific expression. By deletion studies, three specific regions, which were contributing to the transcription activity in lymphoid cells, were localized. In one of these regions, an inverted CCAAT box was identified and shown to bind the transcription activator nuclear factor-Y (NF-Y). The importance of NF-Y binding for the ephrin-A4 promoter activity is shown by a total abrogation of promoter activity after destruction of its binding site. NF-Y binding and activity are also crucially dependent on the integrity of the surrounding sequence. In addition, electrophoretic mobility-shift assay and serial-mutation analysis of the two remaining regulating regions revealed cis regulatory elements contributing to the transcription activity of the ephrin-A4 promoter.
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Affiliation(s)
- Else Munthe
- Department of Immunology, The Norwegian Radium Hospital, Montebello, N-0310 Oslo, Norway.
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31
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Azmi S, Taneja R. Embryonic expression of mSharp-1/mDEC2, which encodes a basic helix-loop-helix transcription factor. Mech Dev 2002; 114:181-5. [PMID: 12175508 DOI: 10.1016/s0925-4773(02)00049-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We describe the expression pattern of mouse Sharp-1 (mSharp-1), a member of the basic helix-loop-helix (bHLH) family of transcription factors. mSharp-1 belongs to the Hairy/Enhancer of Split (E(Spl)) subfamily of bHLH factors that are key targets of the Notch signaling pathway and exhibits the highest sequence identity with Stra13. RNA in situ hybridization analysis from embryonic day 7.5 (E7.5) to E16.5 revealed specific expression of mSharp-1 in several developing organs during mouse embryogenesis. In early stage embryos (E8.5-E12.5), mSharp-1 is expressed in specific dorsal regions of the developing brain, the heart, the developing eye and olfactory system, as well as in the limb buds. At later stages (E12.5-E16.5), mSharp-1 is also expressed in the liver, prevertebrae, and the developing adrenal and thyroid glands. The diversity of its expression pattern suggests that mSharp-1 may regulate the differentiation of several cell types during vertebrate development.
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Affiliation(s)
- Sameena Azmi
- Department of Biochemisty and Molecular Biology, Mount Sinai School of Medicine, Box 1020, One Gustave L. Levy Place, New York, NY 10029-6574, USA
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32
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Abstract
Segmentation of the vertebrate hindbrain into rhombomeres is a key step in the development of a complex pattern of differentiated neurons from a homogeneous neuroepithelium. Many of the transcription factors important for establishing the segmental plan and assigning rhombomere identity are now known. However, the downstream effectors that bring about the formation of rhombomere boundaries are only just being characterized. Here we discuss molecules that could be responsible for segregating populations of cells from different rhombomeres. We focus on recent work demonstrating that the Eph family of receptor tyrosine kinases and their ligands, the ephrins, function in rhombomere-specific cell sorting and initiation of a structural boundary. We discuss the contributions of two mechanisms -- cell sorting and plasticity -- to the formation of rhombomere boundaries.
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Affiliation(s)
- Julie E Cooke
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Research Center B2-152, 1100 Fairview Avenue N., Seattle, WA 98109, USA.
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33
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Pasini A, Wilkinson DG. Stabilizing the regionalisation of the developing vertebrate central nervous system. Bioessays 2002; 24:427-38. [PMID: 12001266 DOI: 10.1002/bies.10085] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
During embryonic development, a number of tissues are patterned by their subdivision into domains with distinct regional identity. An important question is how sharp interfaces are established and maintained between adjacent domains despite the potential for scrambling due to cell intermingling during tissue growth. Two mechanisms have been found to underlie the maintenance of sharp interfaces: the specific restriction of cell mixing across boundaries, or the switching of identity of cells that cross between domains. We review the evidence for these mechanisms at distinct boundaries in the developing vertebrate central nervous system, and discuss what is known about their molecular mediators.
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Affiliation(s)
- Andrea Pasini
- Division of Developmental Neurobiology, National Institute for Medical Research, London
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34
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Stadler HS, Higgins KM, Capecchi MR. Loss of Eph-receptor expression correlates with loss of cell adhesion and chondrogenic capacity in Hoxa13 mutant limbs. Development 2001; 128:4177-88. [PMID: 11684655 DOI: 10.1242/dev.128.21.4177] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mesenchymal patterning is an active process whereby genetic commands coordinate cell adhesion, sorting and condensation, and thereby direct the formation of morphological structures. In mice that lack the Hoxa13 gene, the mesenchymal condensations that form the autopod skeletal elements are poorly resolved, resulting in missing digit, carpal and tarsal elements. In addition, mesenchymal and endothelial cell layers of the umbilical arteries (UAs) are disorganized, resulting in their stenosis and in embryonic death. To further investigate the role of Hoxa13 in these phenotypes, we generated a loss-of-function allele in which the GFP gene was targeted into the Hoxa13 locus. This allele allowed FACS isolation of mesenchymal cells from Hoxa13 heterozygous and mutant homozygous limb buds. Hoxa13GFP expressing mesenchymal cells from Hoxa13 mutant homozygous embryos are defective in forming chondrogenic condensations in vitro. Analysis of pro-adhesion molecules in the autopod of Hoxa13 mutants revealed a marked reduction in EphA7 expression in affected digits, as well as in micromass cell cultures prepared from mutant mesenchymal cells. Finally, antibody blocking of the EphA7 extracellular domain severely inhibits the capacity of Hoxa13GFP heterozygous cells to condense and form chondrogenic nodules in vitro, which is consistent with the hypothesis that reduction in EphA7 expression affects the capacity of Hoxa13–/– mesenchymal cells to form chondrogenic condensations in vivo and in vitro. EphA7 and EphA4 expression were also decreased in the mesenchymal and endothelial cells that form the umbilical arteries in Hoxa13 mutant homozygous embryos. These results suggest that an important role for Hoxa13 during limb and UA development is to regulate genes whose products are required for mesenchymal cell adhesion, sorting and boundary formation.
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Affiliation(s)
- H S Stadler
- Howard Hughes Medical Institute, University of Utah School of Medicine, Salt Lake City, UT 84112-5331, USA
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Alavizadeh A, Kiernan AE, Nolan P, Lo C, Steel KP, Bucan M. The Wheels mutation in the mouse causes vascular, hindbrain, and inner ear defects. Dev Biol 2001; 234:244-60. [PMID: 11356033 DOI: 10.1006/dbio.2001.0241] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In a screen for mouse mutations with dominant behavioral anomalies, we identified Wheels, a mutation associated with circling and hyperactivity in heterozygotes and embryonic lethality in homozygotes. Mutant Wheels embryos die at E10.5-E11.5 and exhibit a host of morphological anomalies which include growth retardation and anomalies in vascular and hindbrain development. The latter includes perturbation of rhombomeric boundaries as detected by Krox20 and Hoxb1. PECAM-1 staining of embryos revealed normal formation of the primary vascular plexus. However, subsequent stages of branching and remodeling do not proceed normally in the yolk sac and in the embryo proper. To obtain insights into the circling behavior, we examined development of the inner ear by paint-filling of membranous labyrinths of Whl/+ embryos. This analysis revealed smaller posterior and lateral semicircular canal primordia and a delay in the canal fusion process at E12.5. By E13.5, the lateral canal was truncated and the posterior canal was small or absent altogether. Marker analysis revealed an early molecular phenotype in heterozygous embryos characterized by perturbed expression of Bmp4 and Msx1 in prospective lateral and posterior cristae at E11.5. We have constructed a genetic and radiation hybrid map of the centromeric portion of mouse Chromosome 4 across the Wheels region and refined the position of the Wheels locus to the approximately 1.1-cM region between D4Mit104 and D4Mit181. We have placed the locus encoding Epha7, in the Wheels candidate region; however, further analysis showed no mutations in the Epha7-coding region and no detectable changes in mRNA expression pattern. In summary, our findings indicate that Wheels, a gene which is essential for the survival of the embryo, may link diverse processes involved in vascular, hindbrain, and inner ear development.
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Affiliation(s)
- A Alavizadeh
- Department of Psychiatry and Genetics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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36
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Schilling TF, Prince V, Ingham PW. Plasticity in zebrafish hox expression in the hindbrain and cranial neural crest. Dev Biol 2001; 231:201-16. [PMID: 11180963 DOI: 10.1006/dbio.2000.9997] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The anterior-posterior identities of cells in the hindbrain and cranial neural crest are thought to be determined by their Hox gene expression status, but how and when cells become committed to these identities remain unclear. Here we address this in zebrafish by cell transplantation, to test plasticity in hox expression in single cells. We transplanted cells alone, or in small groups, between hindbrain rhombomeres or between the neural crest primordia of pharyngeal arches. We found that transplanted cells regulated hox expression according to their new environments. The degree of plasticity, however, depended on both the timing and the size of the transplant. At later stages transplanted cells were more likely to be irreversibly committed and maintain their hox expression, demonstrating a progressive loss of responsiveness to the environmental signals that specify segmental identities. Individual transplanted cells also showed greater plasticity than those lying within the center of larger groups, suggesting that a community effect normally maintains hox expression within segments. We also raised experimental embryos to larval stages to analyze transplanted cells after differentiation and found that neural crest cells contributed to pharyngeal cartilages appropriate to the anterior-posterior level of the new cellular environment. Thus, consistent with models implicating hox expression in control of segmental identity, plasticity in hox expression correlates with plasticity in final cell fate.
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Affiliation(s)
- T F Schilling
- Molecular Embryology Laboratory, Imperial Cancer Research Fund, London, United Kingdom.
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37
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Pasqualetti M, Ori M, Nardi I, Rijli FM. Ectopic Hoxa2 induction after neural crest migration results in homeosis of jaw elements in Xenopus. Development 2000; 127:5367-78. [PMID: 11076758 DOI: 10.1242/dev.127.24.5367] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hox genes are required to pattern neural crest (NC) derived craniofacial and visceral skeletal structures. However, the temporal requirement of Hox patterning activity is not known. Here, we use an inducible system to establish Hoxa2 activity at distinct NC migratory stages in Xenopus embryos. We uncover stage-specific effects of Hoxa2 gain-of-function suggesting a multistep patterning process for hindbrain NC. Most interestingly, we show that Hoxa2 induction at postmigratory stages results in mirror image homeotic transformation of a subset of jaw elements, normally devoid of Hox expression, towards hyoid morphology. This is the reverse phenotype to that observed in the Hoxa2 knockout. These data demonstrate that the skeletal pattern of rhombomeric mandibular crest is not committed before migration and further implicate Hoxa2 as a true selector of hyoid fate. Moreover, the demonstration that the expression of Hoxa2 alone is sufficient to transform the upper jaw and its joint selectively may have implications for the evolution of jaws.
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Affiliation(s)
- M Pasqualetti
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Collège de France, BP 163 - 67404 Illkirch Cedex, C.U. de Strasbourg, France
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38
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Schulte D, Cepko CL. Two homeobox genes define the domain of EphA3 expression in the developing chick retina. Development 2000; 127:5033-45. [PMID: 11060230 DOI: 10.1242/dev.127.23.5033] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Graded expression of the Eph receptor EphA3 in the retina and its two ligands, ephrin A2 and ephrin A5 in the optic tectum, the primary target of retinal axons, have been implicated in the formation of the retinotectal projection map. Two homeobox containing genes, SOHo1 and GH6, are expressed in a nasal-high, temporal-low pattern during early retinal development, and thus in opposing gradients to EphA3. Retroviral misexpression of SOHo1 or GH6 completely and specifically repressed EphA3 expression in the neural retina, but not in other parts of the central nervous system, such as the optic tectum. Under these conditions, some temporal ganglion cell axons overshot their expected termination zones in the rostral optic tectum, terminating aberrantly at more posterior locations. However, the majority of ganglion cell axons mapped to the appropriate rostrocaudal locations, although they formed somewhat more diffuse termination zones. These findings indicate that other mechanisms, in addition to differential EphA3 expression in the neural retina, are required for retinal ganglion axons to map to the appropriate rostrocaudal locations in the optic tectum. They further suggest that the control of topographic specificity along the retinal nasal-temporal axis is split into several independent pathways already at a very early time in development.
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Affiliation(s)
- D Schulte
- Department of Genetics and Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
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39
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Trainor PA, Krumlauf R. Patterning the cranial neural crest: hindbrain segmentation and Hox gene plasticity. Nat Rev Neurosci 2000; 1:116-24. [PMID: 11252774 DOI: 10.1038/35039056] [Citation(s) in RCA: 240] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Understanding the patterning mechanisms that control head development--particularly the neural crest and its contribution to bones, nerves and connective tissue--is an important problem, as craniofacial anomalies account for one-third of all human congenital defects. Classical models for craniofacial patterning argue that the morphogenic program and Hox gene identity of the neural crest is pre-patterned, carrying positional information acquired in the hindbrain to the peripheral nervous system and the branchial arches. Recently, however, plasticity of Hox gene expression has been observed in the hindbrain and cranial neural crest of chick, mouse and zebrafish embryos. Hence, craniofacial development is not dependent on neural crest prepatterning, but is regulated by a more complex integration of cell and tissue interactions.
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Affiliation(s)
- P A Trainor
- Division of Developmental Neurobiology, NIMR, The Ridgeway, Mill Hill, London, NW7 1AA, UK.
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40
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Abstract
Retinal ganglion cell (RGC) axons travel in radial routes unerringly toward the optic disk, their first intermediate target in the center of the eye. The path of the RGC growth cone is restricted to a narrow zone subjacent to the endfeet of Müller glial cells and the vitreal basal lamina. The present survey indicates that RGC growth cones are guided by many molecular cues along their pathway which are recognized by receptors on their surface. Growth-promoting molecules on Müller glial endfeet and in the basal lamina assist growth cones in maintaining contact with these elements. The repellant character of deeper retinal laminae discourages them from escaping the RGC axon layer. Cell adhesion/recognition proteins enable growth cones to fasciculate with preformed axons in their vicinity. It is still unclear whether the optic disk emits long range guidance components which enable the growth cones to steer toward it. Recent evidence in fish indicates the existence of an axonal receptor (neurolin) for a guidance component of unknown identity. Receptor blockade causes RGC axons to course in aberrant routes before they reach the disk. At the disk, axons receive signals to exit the retina. Contact with netrin-1 at the optic disk/nerve head encourages growth cones to turn into the nerve. This response requires the axonal netrin receptor DCC, laminin-1, beta-integrin and most likely the UNC5H netrin receptors which convert the growth encouraging signal into a repulsive one which drives growth cones into the nerve.
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Affiliation(s)
- C A Stuermer
- Department of Biology, Developmental Neurobiology, University of Konstanz, 78457, Konstanz, Germany.
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41
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Trainor PA, Manzanares M, Krumlauf R. Genetic interactions during hindbrain segmentation in the mouse embryo. Results Probl Cell Differ 2000; 30:51-89. [PMID: 10857185 DOI: 10.1007/978-3-540-48002-0_3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- P A Trainor
- Division of Developmental Neurobiology, MRC National Institute for Medical Research, Mill Hill, London, UK
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42
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Pöpperl H, Rikhof H, Chang H, Haffter P, Kimmel CB, Moens CB. lazarus is a novel pbx gene that globally mediates hox gene function in zebrafish. Mol Cell 2000; 6:255-67. [PMID: 10983974 DOI: 10.1016/s1097-2765(00)00027-7] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Individual vertebrate Hox genes specify aspects of segment identity along the anterior-posterior axis. The exquisite in vivo specificity of Hox proteins is thought to result from their interactions with members of the Pbx/Exd family of homeodomain proteins. Here, we report the identification and cloning of a zebrafish gene, lazarus, which is required globally for segmental patterning in the hindbrain and anterior trunk. We show that lazarus is a novel pbx gene and provide evidence that it is the primary pbx gene required for the functions of multiple hox genes during zebrafish development. lazarus plays a critical role in orchestrating the corresponding segmentation of the hindbrain and the pharyngeal arches, a key step in the development of the vertebrate body plan.
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Affiliation(s)
- H Pöpperl
- Division of Basic Science, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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43
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Xu Q, Mellitzer G, Wilkinson DG. Roles of Eph receptors and ephrins in segmental patterning. Philos Trans R Soc Lond B Biol Sci 2000; 355:993-1002. [PMID: 11128993 PMCID: PMC1692797 DOI: 10.1098/rstb.2000.0635] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Eph receptor tyrosine kinases and their membrane-bound ligands, ephrins, have key roles in patterning and morphogenesis. Interactions between these molecules are promiscuous, but largely fall into two groups: EphA receptors bind to glycosylphosphatidyl inositol-anchored ephrin-A ligands, and EphB receptors bind to transmembrane ephrin-B proteins. Ephrin-B proteins transduce signals, such that bidirectional signalling can occur upon interaction with the Eph receptor. In many tissues, there are complementary and overlapping expression domains of interacting Eph receptors and ephrins. An important role of Eph receptors and ephrins is to mediate cell contact-dependent repulsion, and this has been implicated in the pathfinding of axons and neural crest cells, and the restriction of cell intermingling between hindbrain segments. Studies in an in vitro system show that bidirectional activation is required to prevent intermingling between cell populations, whereas unidirectional activation can restrict cell communication via gap junctions. Recent work indicates that Eph receptors can also upregulate cell adhesion, but the biochemical basis of repulsion versus adhesion responses is unclear. Eph receptors and ephrins have thus emerged as key regulators that, in parallel with cell adhesion molecules, underlie the establishment and maintenance of patterns of cellular organization.
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Affiliation(s)
- Q Xu
- Division of Developmental Neurobiology, National Institute for Medical Research, London, UK
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44
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Abstract
The murine HOXA-2 protein shares amino acid sequence similarity with Drosophila Proboscipedia (PB). In this paper, we test whether HOXA-2 and PB are functionally equivalent in Drosophila. In Drosophila, PB inhibits SCR activity required for larval T1 beard formation and adult tarsus formation and is required for maxillary palp and proboscis formation. HOXA-2 expressed from a heat-shock promoter weakly suppressed SCR activity required for T1 beard formation. But interestingly neither PB nor HOXA-2 expressed from a heat-shock promoter suppressed murine HOXA-5 activity, the murine SCR homologue, from inducing ectopic T1 beards in T2 and T3, indicating that HOXA-5 does not interact with PB. HOXA-2 activity expressed from the Tubulin alpha 1 promoter modified the pb null phenotype resulting in a proboscis-to-arista transformation, indicating that HOXA-2 was able to suppress SCR activity required for tarsus formation. However, HOXA-2 expressed from a Tubulin alpha 1 promoter was unable to direct maxillary palp determination when either ectopically expressed in the antenna or in the maxillary palp primordia of a pb null mutant. HOXA-2 was also unable to rescue pseudotrachea formation in a pb null mutant. These results indicate that the only activity that PB and HOXA-2 weakly share is the inhibition of SCR activity, and that murine HOXA-5 and Drosophila SCR do not share inhibition by PB activity.
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Affiliation(s)
- A Percival-Smith
- Department of Zoology, University of Western Ontario, London, Canada.
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45
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Orsulic S, Kemler R. Expression of Eph receptors and ephrins is differentially regulated by E-cadherin. J Cell Sci 2000; 113 ( Pt 10):1793-802. [PMID: 10769210 DOI: 10.1242/jcs.113.10.1793] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
E-cadherin is the main cell adhesion molecule of early embryonic and adult epithelial cells. Downregulation of E-cadherin is associated with epithelial-mesenchymal transition during embryonic mesoderm formation and tumor progression. To identify genes whose expression is affected by the loss of E-cadherin, we compared mRNA expression patterns between wild-type and E-cadherin null mutant embryonic stem (ES) cells. We found that expression of several Eph receptors and ephrins is dependent on E-cadherin. Rescue of E-cadherin null ES cells with E-cadherin cDNA restores the wild-type expression pattern of Eph family members. Rescue of E-cadherin null ES cells with N-cadherin cDNA does not restore the wild-type expression pattern, indicating that the regulation of differential expression of Eph family members is specific to E-cadherin. Constitutive ectopic expression of E-cadherin in non-epithelial NIH3T3 cells results in the production of the EphA2 receptor. In epithelial cells, E-cadherin is required for EphA2 receptor localization at cell-cell contacts; in the absence of functional E-cadherin, EphA2 localizes to the perinuclear region. Our results indicate that E-cadherin may be directly or indirectly required for the membrane localization of Eph receptors and their membrane-bound ligands.
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Affiliation(s)
- S Orsulic
- Max-Planck-Institut für Immunbiologie, Stübeweg 51, D-79108 Freiburg, Germany.
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46
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Jeong J, Choi S, Gu C, Lee H, Park S. Genomic structure and promoter analysis of the mouse EphA8 receptor tyrosine kinase gene. DNA Cell Biol 2000; 19:291-300. [PMID: 10855796 DOI: 10.1089/10445490050021203] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The gene encoding the mouse EphA8 receptor tyrosine kinase has been isolated from a mouse genomic library, and its complete genomic structure has been determined. This gene spans approximately 28 kb and consists of 17 exons. This gene structure is similar to the structure of the chick EphB2 (Cek5) gene, except for one intron present between the first two exons encoding the EphA8 kinase domain. This difference may reflect an evolutionary divergence of the catalytic domain between EphA and EphB subgroup receptors. The site for transcription initiation has been mapped to the 19th nucleotide upstream from the translation start codon ATG. A feature of this gene is an unmethylated CpG island spanning exon 1 and the flanking sequence. The putative promoter of the EphA8 gene lacks a TATA box and contains multiple copies of the sequence GGGCGG, the core sequence of the putative Sp1-binding site. The 3.5-kb upstream genomic region containing part of the first exon showed strong promoter activity in NG108-15 neuroblastoma cells but much less in 293T cells, suggesting that this fragment is sufficient for neural cell-directed promoter activity. By deleting the genomic region containing the five GC boxes, it was shown that the minimal promoter region is primarily comprised of five copies of the Sp1-binding site located upstream from the transcription initiation site. Finally, in situ RNA hybridization studies revealed a very specific pattern of EphA8 gene expression restricted to the rostral region of midbrain tectum during embryonic development. Isolation of a functional promoter for the EphA8 gene is a first step in understanding how expression of this gene is controlled at the molecular level.
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Affiliation(s)
- J Jeong
- Institute of Environment and Life Science, Hallym University, Kangwon-do,Korea
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47
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Wilkinson DG. Eph receptors and ephrins: regulators of guidance and assembly. INTERNATIONAL REVIEW OF CYTOLOGY 2000; 196:177-244. [PMID: 10730216 DOI: 10.1016/s0074-7696(00)96005-4] [Citation(s) in RCA: 162] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recent advances have started to elucidate the developmental functions and biochemistry of Eph receptor tyrosine kinases and their membrane-bound ligands, ephrins. Interactions between these molecules are promiscuous, but they largely fall into two groups: EphA receptors bind to GPI-anchored ephrin-A ligands, while EphB receptors bind to ephrin-B proteins that have a transmembrane and cytoplasmic domain. Remarkably, ephrin-B proteins transduce signals, such that bidirectional signaling can occur upon interaction with Eph receptor. In many tissues, specific Eph receptors and ephrins have complementary domains, whereas other family members may overlap in their expression. An important role of Eph receptors and ephrins is to mediate cell-contact-dependent repulsion. Complementary and overlapping gradients of expression underlie establishment of a topographic map of neuronal projections in the retinotectal system. Eph receptors and ephrins also act at boundaries to channel neuronal growth cones along specific pathways, restrict the migration of neural crest cells, and via bidirectional signaling prevent intermingling between hindbrain segments. Intriguingly, Eph receptors and ephrins can also trigger an adhesive response of endothelial cells and are required for the remodeling of blood vessels. Biochemical studies suggest that the extent of multimerization of Eph receptors modulates the cellular response and that the actin cytoskeleton is one major target of the intracellular pathways activated by Eph receptors. Eph receptors and ephrins have thus emerged as key regulators of the repulsion and adhesion of cells that underlie the establishment, maintenance, and remodeling of patterns of cellular organization.
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Affiliation(s)
- D G Wilkinson
- Division of Developmental Neurobiology, National Institute for Medical Research, London, United Kingdom
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48
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Becker CG, Becker T. Gradients of ephrin-A2 and ephrin-A5b mRNA during retinotopic regeneration of the optic projection in adult zebrafish. J Comp Neurol 2000. [DOI: 10.1002/1096-9861(20001120)427:3<469::aid-cne12>3.0.co;2-n] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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49
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Rogers JH, Ciossek T, Ullrich A, West E, Hoare M, Muir EM. Distribution of the receptor EphA7 and its ligands in development of the mouse nervous system. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1999; 74:225-30. [PMID: 10640695 DOI: 10.1016/s0169-328x(99)00284-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
EphA7 is a receptor tyrosine kinase of the Eph family. We have mapped EphA7 immunoreactivity and ligand binding in mouse embryo heads and developing brain. Immunoreactivity for the full-length receptor is found in all the cell populations that express EphA7 mRNA. In particular, it is located on growing axons from EphA7-expressing neurons, both in the trigeminal nerve and in developing brain. In many cases it persists in terminal fields in adult brain. Ligand is detected in a largely complementary distribution in embryos, but is surprisingly weak or undetectable in the target regions of many EphA7-positive axons postnatally.
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Affiliation(s)
- J H Rogers
- Department of Physiology, University of Cambridge, Downing St., Cambridge, UK.
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50
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Fortin G, Jungbluth S, Lumsden A, Champagnat J. Segmental specification of GABAergic inhibition during development of hindbrain neural networks. Nat Neurosci 1999; 2:873-7. [PMID: 10491606 DOI: 10.1038/13172] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A primordial rhythm-generating neural network emerges during the segmental period of vertebrate hindbrain development, suggesting a common genetic basis to both the structure and network activity of the region. We show here that segmentation influenced a postsegmental developmental step by which a GABAergic rhythm generator was incorporated into the primordial network and increased rhythm frequency to near mature values. This process depended on specifications in r3 and r5 that controlled, on the basis of a two-segment repeat, later maturation of GABAergic inhibition.
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Affiliation(s)
- G Fortin
- Biologie Fonctionnelle du Neurone, Institut Alfred Fessard, C.N.R.S., 1, av. de la Terrasse, 91198 Gif-sur-Yvette, France.gilles.
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