1
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Ji Y, Garland MA, Sun B, Zhang S, Reynolds K, McMahon M, Rajakumar R, Islam MS, Liu Y, Chen Y, Zhou CJ. Cellular and developmental basis of orofacial clefts. Birth Defects Res 2020; 112:1558-1587. [PMID: 32725806 DOI: 10.1002/bdr2.1768] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 06/21/2020] [Accepted: 06/27/2020] [Indexed: 12/11/2022]
Abstract
During craniofacial development, defective growth and fusion of the upper lip and/or palate can cause orofacial clefts (OFCs), which are among the most common structural birth defects in humans. The developmental basis of OFCs includes morphogenesis of the upper lip, primary palate, secondary palate, and other orofacial structures, each consisting of diverse cell types originating from all three germ layers: the ectoderm, mesoderm, and endoderm. Cranial neural crest cells and orofacial epithelial cells are two major cell types that interact with various cell lineages and play key roles in orofacial development. The cellular basis of OFCs involves defective execution in any one or several of the following processes: neural crest induction, epithelial-mesenchymal transition, migration, proliferation, differentiation, apoptosis, primary cilia formation and its signaling transduction, epithelial seam formation and disappearance, periderm formation and peeling, convergence and extrusion of palatal epithelial seam cells, cell adhesion, cytoskeleton dynamics, and extracellular matrix function. The latest cellular and developmental findings may provide a basis for better understanding of the underlying genetic, epigenetic, environmental, and molecular mechanisms of OFCs.
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Affiliation(s)
- Yu Ji
- Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, Sacramento, California, USA.,Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA.,Biochemistry, Molecular, Cellular, and Developmental Biology (BMCDB) graduate group, University of California, Davis, California, USA
| | - Michael A Garland
- Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, Sacramento, California, USA.,Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA
| | - Bo Sun
- Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, Sacramento, California, USA.,Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA
| | - Shuwen Zhang
- Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, Sacramento, California, USA.,Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA
| | - Kurt Reynolds
- Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, Sacramento, California, USA.,Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA.,Biochemistry, Molecular, Cellular, and Developmental Biology (BMCDB) graduate group, University of California, Davis, California, USA
| | - Moira McMahon
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA
| | - Ratheya Rajakumar
- Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, Sacramento, California, USA.,Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA
| | - Mohammad S Islam
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA
| | - Yue Liu
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA
| | - YiPing Chen
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana, USA
| | - Chengji J Zhou
- Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, Sacramento, California, USA.,Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, School of Medicine, University of California at Davis, Sacramento, California, USA.,Biochemistry, Molecular, Cellular, and Developmental Biology (BMCDB) graduate group, University of California, Davis, California, USA
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2
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Logan SM, Benson MD. Medial epithelial seam cell migration during palatal fusion. J Cell Physiol 2019; 235:1417-1424. [PMID: 31264714 DOI: 10.1002/jcp.29061] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 06/13/2019] [Indexed: 12/13/2022]
Abstract
The mammalian secondary palate forms from two shelves of mesenchyme sheathed in a single-layered epithelium. These shelves meet during embryogenesis to form the midline epithelial seam (MES). Failure of MES degradation prevents mesenchymal confluence and results in a cleft palate. Previous studies indicated that MES cells undergo features of epithelial-to-mesenchymal transition (EMT) and may become migratory as part of the fusion mechanism. To detect MES cell movement over the course of fusion, we imaged the midline of fusing embryonic ephrin-B2/GFP mouse palates in real time using two-photon microscopy. These mice express an ephrin-B2-driven green fluorescent protein (GFP) that labels the palatal epithelium nuclei and persists in those cells through the time window necessary for fusion. We observed collective migration of MES cells toward the oral surface of the palatal shelf over 48 hr of imaging, and we confirmed histologically that the imaged palates had fused by the end of the imaged period. We previously reported that ephrin reverse signaling in the MES is required for palatal fusion. We therefore added recombinant EphA4/Fc protein to block this signaling in imaged palates. The blockage inhibited fusion, as expected, but did not change the observed migration of GFP-labeled cells. Thus, we uncoupled migration and fusion. Our data reveal that palatal MES cells undergo a collective, unidirectional movement during palatal fusion and that ephrin reverse signaling, though required for fusion, controls aspects of the fusion mechanism independent of migration.
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Affiliation(s)
- Shaun M Logan
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas
| | - M Douglas Benson
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas
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Chen H, Chen Q, Jiang CM, Shi GY, Sui BW, Zhang W, Yang LZ, Li ZY, Liu L, Su YM, Zhao WC, Sun HQ, Li ZZ, Fu Z. Triptolide suppresses paraquat induced idiopathic pulmonary fibrosis by inhibiting TGFB1-dependent epithelial mesenchymal transition. Toxicol Lett 2017; 284:1-9. [PMID: 29195901 DOI: 10.1016/j.toxlet.2017.11.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 11/22/2017] [Accepted: 11/27/2017] [Indexed: 12/24/2022]
Abstract
Idiopathic pulmonary fibrosis (IPF) and tumor are highly similar to abnormal cell proliferation that damages the body. This malignant cell evolution in a stressful environment closely resembles that of epithelial-mesenchymal transition (EMT). As a popular EMT-inducing factor, TGFβ plays an important role in the progression of multiple diseases. However, the drugs that target TGFB1 are limited. In this study, we found that triptolide (TPL), a Chinese medicine extract, exerts an anti-lung fibrosis effect by inhibiting the EMT of lung epithelial cells. In addition, triptolide directly binds to TGFβ and subsequently increase E-cadherin expression and decrease vimentin expression. In in vivo studies, TPL improves the survival state and inhibits lung fibrosis in mice. In summary, this study revealed the potential therapeutic effect of paraquat induced TPL in lung fibrosis by regulating TGFβ-dependent EMT progression.
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Affiliation(s)
- Hong Chen
- Department of Respiratory Medicine, Children's Hospital of Chongqing Medical University, Ministry of Education Key Laboratory of Child Development and Disorders, China; China International Science and Technology Cooperation base of Child development and Critical Disorders, China; Chongqing Engineering Research Center of Stem Cell Therapy, China; Department of Pediatrics, First Affiliated Hospital, Heilongjiang University Of Chinese Medicine, China
| | - Qun Chen
- Department of Laboratory, The People's Hospital of Acheng District, Harbin, China
| | - Chun-Ming Jiang
- The First Affiliated Hospital of Harbin Medical University, China
| | | | - Bo-Wen Sui
- First Affiliated Hospital, Heilongjiang University Of Chinese Medicine, China
| | - Wei Zhang
- First Affiliated Hospital, Heilongjiang University Of Chinese Medicine, China
| | - Li-Zhen Yang
- First Affiliated Hospital, Heilongjiang University Of Chinese Medicine, China
| | - Zhu-Ying Li
- First Affiliated Hospital, Heilongjiang University Of Chinese Medicine, China
| | - Li Liu
- First Affiliated Hospital, Heilongjiang University Of Chinese Medicine, China
| | - Yu-Ming Su
- First Affiliated Hospital, Heilongjiang University Of Chinese Medicine, China
| | - Wen-Cheng Zhao
- The First Affiliated Hospital of Harbin Medical University, China
| | - Hong-Qiang Sun
- The First Affiliated Hospital of Harbin Medical University, China
| | | | - Zhou Fu
- Department of Respiratory Medicine, Children's Hospital of Chongqing Medical University, Ministry of Education Key Laboratory of Child Development and Disorders, China; China International Science and Technology Cooperation base of Child development and Critical Disorders, China; Chongqing Engineering Research Center of Stem Cell Therapy, China.
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4
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Ibrahim I, Serrano MJ, Ruest LB, Svoboda KKH. Biglycan and Decorin Expression and Distribution in Palatal Adhesion. J Dent Res 2017; 96:1445-1450. [PMID: 28759311 DOI: 10.1177/0022034517722783] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Previous studies demonstrated that chondroitin sulfate proteoglycans (CSPGs) on apical surfaces of palatal medial edge epithelial (MEE) cells were necessary for palatal adhesion. In this study, we identified 2 proteoglycans, biglycan and decorin, that were expressed in the palatal shelves prior to adhesion. In addition, we established that these proteoglycans were dependent on transforming growth factor β (TGFβ) signaling. Laser capture microdissection was used to collect selected palatal epithelial cells from embryonic mouse embryos at various palate development stages. The expression of specific messenger RNA (mRNA) for biglycan and decorin was determined with quantitative real-time polymerase chain reaction. The TGFβrI kinase inhibitor (SB431542) was used in palatal organ cultures to determine if blocking TFGβ signaling changed biglycan and decorin distribution. Immunohistochemistry of both biglycan and decorin revealed expression on the apical and lateral surfaces of MEE cells. Biglycan protein and mRNA levels peaked as the palatal shelves adhered. Decorin was less abundant on the apical epithelial surface and also had reduced mRNA levels compared to biglycan. Their proteins were not expressed on MEE cells of palates treated with SB431542, an inhibitor of TGFβ signaling. The temporal expression of biglycan and decorin on the apical surface of MEE, combined with the evidence that these proteins were regulated through the TGFβ pathway, indicated that they may be important for adhesion.
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Affiliation(s)
- I Ibrahim
- 1 Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, TX, USA
| | - M J Serrano
- 1 Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, TX, USA
| | - L B Ruest
- 1 Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, TX, USA
| | - K K H Svoboda
- 1 Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, TX, USA
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Serrano MJ, Liu J, Svoboda KKH, Nawshad A, Benson MD. Ephrin reverse signaling mediates palatal fusion and epithelial-to-mesenchymal transition independently of Tgfß3. J Cell Physiol 2015; 230:2961-72. [PMID: 25893671 DOI: 10.1002/jcp.25025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 04/16/2015] [Indexed: 01/02/2023]
Abstract
The mammalian secondary palate forms from shelves of epithelia-covered mesenchyme that meet at midline and fuse. The midline epithelial seam (MES) is thought to degrade by apoptosis, epithelial-to-mesenchymal transition (EMT), or both. Failure to degrade the MES blocks fusion and causes cleft palate. It was previously thought that transforming growth factor ß3 (Tgfß3) is required to initiate fusion. Members of the Eph tyrosine kinase receptor family and their membrane-bound ephrin ligands are expressed on the MES. We demonstrated that treatment of mouse palates with recombinant EphB2/Fc to activate ephrin reverse signaling (where the ephrin acts as a receptor and transduces signals from its cytodomain) was sufficient to cause mouse palatal fusion when Tgfß3 signaling was blocked by an antibody against Tgfß3 or by an inhibitor of the TgfßrI serine/threonine receptor kinase. Cultured palatal epithelial cells traded their expression of epithelial cell markers for that of mesenchymal cells and became motile after treatment with EphB2/Fc. They concurrently increased their expression of the EMT-associated transcription factors Snail, Sip1, and Twist1. EphB2/Fc did not cause apoptosis in these cells. These data reveal that ephrin reverse signaling directs palatal fusion in mammals through a mechanism that involves EMT but not apoptosis and activates a gene expression program not previously associated with ephrin reverse signaling.
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Affiliation(s)
- Maria J Serrano
- Department of Biomedical Sciences, Texas A&M University Baylor College of Dentistry, Dallas, Texas
| | - Jingpeng Liu
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska
| | - Kathy K H Svoboda
- Department of Biomedical Sciences, Texas A&M University Baylor College of Dentistry, Dallas, Texas
| | - Ali Nawshad
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska
| | - M Douglas Benson
- Department of Biomedical Sciences, Texas A&M University Baylor College of Dentistry, Dallas, Texas
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6
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Ibrahim I, Serrano MJ, Svoboda KKH. Method of Studying Palatal Fusion using Static Organ Culture. J Vis Exp 2015. [PMID: 26437268 DOI: 10.3791/53063] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Cleft lip and palate are among the most common of all birth defects. The secondary palate forms from mesenchymal shelves covered with epithelium that adheres to form the midline epithelial seam (MES). The theories suggest that MES cells follow an epithelial to mesenchymal transition (EMT), apoptosis and migration, making a fused palate (1). Complete disintegration of the MES is the final essential phase of palatal confluence with surrounding mesenchymal cells. We provide a method for palate organ culture. The developed in vitro protocol allows the study of the biological and molecular processes during fusion. The applications of this technique are numerous, including evaluating responses to exogenous chemical agents, effects of regulatory and growth factors and specific proteins. Palatal organ culture has a number of advantages including manipulation at different stages of development that is not possible using in vivo studies.
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Affiliation(s)
- Isra Ibrahim
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry
| | - Maria Juliana Serrano
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry;
| | - Kathy K H Svoboda
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry
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7
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Kim S, Lewis AE, Singh V, Ma X, Adelstein R, Bush JO. Convergence and extrusion are required for normal fusion of the mammalian secondary palate. PLoS Biol 2015; 13:e1002122. [PMID: 25848986 PMCID: PMC4388528 DOI: 10.1371/journal.pbio.1002122] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 03/06/2015] [Indexed: 11/24/2022] Open
Abstract
The fusion of two distinct prominences into one continuous structure is common during development and typically requires integration of two epithelia and subsequent removal of that intervening epithelium. Using confocal live imaging, we directly observed the cellular processes underlying tissue fusion, using the secondary palatal shelves as a model. We find that convergence of a multi-layered epithelium into a single-layer epithelium is an essential early step, driven by cell intercalation, and is concurrent to orthogonal cell displacement and epithelial cell extrusion. Functional studies in mice indicate that this process requires an actomyosin contractility pathway involving Rho kinase (ROCK) and myosin light chain kinase (MLCK), culminating in the activation of non-muscle myosin IIA (NMIIA). Together, these data indicate that actomyosin contractility drives cell intercalation and cell extrusion during palate fusion and suggest a general mechanism for tissue fusion in development. A study of the mouse palate shows that the fusion of tissues during development involves convergence and displacement of epithelial cells, coupled with cell extrusion driven by the contractile activity of actomyosin. Tissue fusion, the process by which two independent prominences become united to form one continuous structure, is common during development, and its failure leads to multiple structural birth defects. In this study, we directly examine the cellular and molecular mechanisms by which tissue fusion occurs using the mouse secondary palate as a model. Using live imaging, we find that fusion of the secondary palatal shelves proceeds by a progression of previously undescribed cell behaviors. Cellular protrusions and establishment of contacts between palatal shelves leads to the formation of a transient multicellular epithelial structure that then converges toward the midline, driven by cell intercalation. This convergence occurs together with displacement of the epithelium and epithelial cell extrusions that squeeze epithelial cells out from between the palatal shelves and mediate continuity of the structure. We show that in mice this morphogenesis requires an actomyosin contractility pathway culminating in non-muscle myosin IIA activation. Altogether, these data support a new model for tissue fusion during mouse embryogenesis in which convergence, displacement, and cell extrusion drive the union of independent structures.
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Affiliation(s)
- Seungil Kim
- Department of Cell and Tissue Biology, Program in Craniofacial Biology and Institute for Human Genetics, University of California, San Francisco, California, United States of America
| | - Ace E. Lewis
- Department of Cell and Tissue Biology, Program in Craniofacial Biology and Institute for Human Genetics, University of California, San Francisco, California, United States of America
| | - Vivek Singh
- Department of Cell and Tissue Biology, Program in Craniofacial Biology and Institute for Human Genetics, University of California, San Francisco, California, United States of America
| | - Xuefei Ma
- Laboratory of Molecular Cardiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Robert Adelstein
- Laboratory of Molecular Cardiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jeffrey O. Bush
- Department of Cell and Tissue Biology, Program in Craniofacial Biology and Institute for Human Genetics, University of California, San Francisco, California, United States of America
- * E-mail:
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Yu W, Zhang Y, Ruest LB, Svoboda KKH. Analysis of Snail1 function and regulation by Twist1 in palatal fusion. Front Physiol 2013; 4:12. [PMID: 23424071 PMCID: PMC3575576 DOI: 10.3389/fphys.2013.00012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 01/10/2013] [Indexed: 12/24/2022] Open
Abstract
Palatal fusion is a tightly controlled process which comprises multiple cellular events, including cell movement and differentiation. Midline epithelial seam (MES) degradation is essential to palatal fusion. In this study, we analyzed the function of Snail1 during the degradation of the MES. We also analyzed the mechanism regulating the expression of the Snail1 gene in palatal shelves. Palatal explants treated with Snail1 siRNA did not degrade the MES and E-cadherin was not repressed leading to failure of palatal fusion. Transforming growth factor beta 3 (Tgfβ3) regulated Snail1 mRNA, as Snail1 expression decreased in response to Tgfβ3 neutralizing antibody and a PI-3 kinase (PI3K) inhibitor. Twist1, in collaboration with E2A factors, regulated the expression of Snail1. Twist1/E47 dimers bond to the Snail1 promoter to activate expression. Without E47, Twist1 repressed Snail1 expression. These results support the hypothesis that Tgfβ3 may signal through Twist1 and then Snail1 to downregulate E-cadherin expression during palatal fusion.
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Affiliation(s)
- Wenli Yu
- Department of Biomedical Sciences, Center for Craniofacial Research and Diagnosis, Texas A&M University, Baylor College of Dentistry Dallas, TX, USA
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9
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Benson MD, Serrano MJ. Ephrin regulation of palate development. Front Physiol 2012; 3:376. [PMID: 23055980 PMCID: PMC3458271 DOI: 10.3389/fphys.2012.00376] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 09/02/2012] [Indexed: 11/17/2022] Open
Abstract
Studies of palate development are motivated by the all too common incidence of cleft palate, a birth defect that imposes a tremendous health burden and can leave lasting disfigurement. Although, mechanistic studies of palate growth and fusion have focused on growth factors such as Transforming Growth Factor ß-3 (Tgfß3), recent studies have revealed that the ephrin family of membrane bound ligands and their receptors, the Ephs, play central roles in palatal morphogenesis, growth, and fusion. In this mini-review, we will discuss the recent findings by our group and others on the functions of ephrins in palatal development.
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Affiliation(s)
- M Douglas Benson
- Department of Biomedical Sciences, Texas A&M Health Science Center Baylor College of Dentistry Dallas, TX, USA
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10
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Rgs19 regulates mouse palatal fusion by modulating cell proliferation and apoptosis in the MEE. Mech Dev 2012; 129:244-54. [DOI: 10.1016/j.mod.2012.07.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 07/18/2012] [Accepted: 07/18/2012] [Indexed: 01/12/2023]
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11
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Jalali A, Zhu X, Liu C, Nawshad A. Induction of palate epithelial mesenchymal transition by transforming growth factor β3 signaling. Dev Growth Differ 2012; 54:633-48. [PMID: 22775504 DOI: 10.1111/j.1440-169x.2012.01364.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 05/14/2012] [Accepted: 05/15/2012] [Indexed: 12/25/2022]
Abstract
Transforming growth factor (TGFβ)3 is essential for palate development, particularly during the late phase of palatogenesis when the disintegration of the palatal medial edge seam (MES) occurs resulting in mesenchymal confluence. The MES is composed of medial-edge epithelium (MEE) of opposite palatal shelves; its complete disintegration is essential for mediating correct craniofacial morphogenesis. This phenomenon is initiated by TGFβ3 upon adherence of opposing palatal shelves, and subsequently epithelial-mesenchymal transition (EMT) instigates the loss of E-Cadherin, causing the MES to break into small epithelial islands forming confluent palatal mesenchyme; however, apoptosis and cell migration or in combination of all are other established mechanisms of seam disintegration. To investigate the molecular mechanisms that cause this E-Cadherin loss, we isolated and cultured murine embryonic primary MES cells from adhered palates and employed several biological approaches to explore the mechanism by which TGFβ3 facilitates palatal seam disintegration. Here, we demonstrate that TGFβ3 signals by activating both Smad-dependent and Smad-independent pathways. However, activation of the two most common EMT related transcription factors, Snail and SIP, was facilitated by Smad-independent pathways, contrary to the commonly accepted Smad-dependent pathway. Finally, we provide the first evidence that TGFβ3-activated Snail and SIP1, combined with Smad4, bind to the E-Cadherin promoter to repress its transcription in response to TGFβ3 signaling. These results suggest that TGFβ3 uses multiple pathways to activate Snail and SIP1 and these transcription factors repress the cell-cell adhesion protein, E-Cadherin, to induce palatal epithelial seam EMT. Manipulation and intervention of the pathways stimulated by TGFβ3 during palate development may have a significant therapeutic potential.
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Affiliation(s)
- Azadeh Jalali
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, NE 68512, USA
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12
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Yoshida M, Shimono Y, Togashi H, Matsuzaki K, Miyoshi J, Mizoguchi A, Komori T, Takai Y. Periderm cells covering palatal shelves have tight junctions and their desquamation reduces the polarity of palatal shelf epithelial cells in palatogenesis. Genes Cells 2012; 17:455-72. [PMID: 22571182 DOI: 10.1111/j.1365-2443.2012.01601.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In palatogenesis, bilateral palatal shelves grow and fuse with each other to establish mesenchyme continuity across the horizontal palate. The palatal shelves are covered with the medial edge epithelium (MEE) in which most apical cells are periderm cells. We investigated localization and roles of tight junction (TJ) and adherens junction (AJ) components and an apical membrane marker in the MEE in palatogenesis. Immunofluorescence and immunoelectron microscopy analyses revealed that TJs were located at the boundary between neighboring periderm cells, whereas AJ components were localized at the boundary between all epithelial cells in the MEE. Specifically, typical AJs were observed at the boundaries between neighboring periderm cells and between periderm cells and underlying epithelial cells where the signal for nectin-1 was observed. The TGF-β-induced desquamation of periderm cells reduced the polarity of remaining epithelial cells as estimated by changes of epithelial cell morphology and the staining of the polarity marker and the AJ components. These less polarized epithelial cells then intermingled and finally disappeared at least partly by apoptosis. These results indicate that periderm cells covering growing palatal shelves have bona fide TJs and their desquamation reduces the polarity of palatal shelf epithelial cells in palatogenesis.
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Affiliation(s)
- Midori Yoshida
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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13
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San Miguel S, Serrano MJ, Sachar A, Henkemeyer M, Svoboda KKH, Benson MD. Ephrin reverse signaling controls palate fusion via a PI3 kinase-dependent mechanism. Dev Dyn 2011; 240:357-64. [PMID: 21246652 DOI: 10.1002/dvdy.22546] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Secondary palate fusion requires adhesion and epithelial-to-mesenchymal transition (EMT) of the epithelial layers on opposing palatal shelves. This EMT requires transforming growth factor β3 (TGFβ3), and its failure results in cleft palate. Ephrins, and their receptors, the Ephs, are responsible for migration, adhesion, and midline closure events throughout development. Ephrins can also act as signal-transducing receptors in these processes, with the Ephs serving as ligands (termed "reverse" signaling). We found that activation of ephrin reverse signaling in chicken palates induced fusion in the absence of TGFβ3, and that PI3K inhibition abrogated this effect. Further, blockage of reverse signaling inhibited TGFβ3-induced fusion in the chicken and natural fusion in the mouse. Thus, ephrin reverse signaling is necessary and sufficient to induce palate fusion independent of TGFβ3. These data describe both a novel role for ephrins in palate morphogenesis, and a previously unknown mechanism of ephrin signaling.
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Affiliation(s)
- Symone San Miguel
- Department of Biomedical Sciences, Texas A&M Health Science Center Baylor College of Dentistry, Dallas, Texas, USA
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14
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Kitase Y, Yamashiro K, Fu K, Richman JM, Shuler CF. Spatiotemporal localization of periostin and its potential role in epithelial-mesenchymal transition during palatal fusion. Cells Tissues Organs 2010; 193:53-63. [PMID: 21051860 DOI: 10.1159/000320178] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The medial epithelial seam (MES) between the palatal shelves degrades during palatal fusion to achieve the confluence of palatal mesenchyme. Cellular mechanisms underlying the degradation of MES have been proposed, such as apoptosis, epithelial-mesenchymal transition (EMT) and migration of medial edge epithelia (MEE). Extracellular matrix components have been shown to play an important role in EMT in many model systems. Periostin (also known as osteoblast-specific factor-2) is a secreted mesenchymal extracellular matrix component that affects the ability of cells to migrate and/or facilitates EMT during both embryonic development and pathologic conditions. In this study, we evaluated the spatiotemporal expression patterns of periostin during mouse palatal fusion by in situ hybridization and immunofluorescence. Periostin mRNA and protein were present in the palatal mesenchyme, the protein being distributed in a fine fibrillar network and in the basement membrane, but absent from the epithelium. During MES degradation, the protein was strongly expressed in the basement membrane underlying the MES and in some select MEE. Confocal microscopic analysis using an EMT marker, twist1, and an epithelial marker, cytokeratin 14, provided evidence that select MEE were undergoing EMT in association with periostin. Moreover, the major extracellular matrix molecules in basement membrane, laminin and collagen type IV were degraded earlier than periostin. The result is that select MEE establish interactions with periostin in the mesenchymal extracellular matrix, and these new cell-matrix interactions may regulate MEE transdifferentiation during palatal fusion.
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Affiliation(s)
- Yukiko Kitase
- Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, B.C., Canada
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15
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The expression of TGF-β3 for epithelial-mesenchyme transdifferentiated MEE in palatogenesis. J Mol Histol 2010; 41:343-55. [DOI: 10.1007/s10735-010-9296-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Accepted: 09/07/2010] [Indexed: 10/18/2022]
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16
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Greene RM, Pisano MM. Palate morphogenesis: current understanding and future directions. ACTA ACUST UNITED AC 2010; 90:133-54. [PMID: 20544696 DOI: 10.1002/bdrc.20180] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In the past, most scientists conducted their inquiries of nature via inductivism, the patient accumulation of "pieces of information" in the pious hope that the sum of the parts would clarify the whole. Increasingly, modern biology employs the tools of bioinformatics and systems biology in attempts to reveal the "big picture." Most successful laboratories engaged in the pursuit of the secrets of embryonic development, particularly those whose research focus is craniofacial development, pursue a middle road where research efforts embrace, rather than abandon, what some have called the "pedestrian" qualities of inductivism, while increasingly employing modern data mining technologies. The secondary palate has provided an excellent paradigm that has enabled examination of a wide variety of developmental processes. Examination of cellular signal transduction, as it directs embryogenesis, has proven exceptionally revealing with regard to clarification of the "facts" of palatal ontogeny-at least the facts as we currently understand them. Herein, we review the most basic fundamentals of orofacial embryology and discuss how functioning of TGFbeta, BMP, Shh, and Wnt signal transduction pathways contributes to palatal morphogenesis. Our current understanding of palate medial edge epithelial differentiation is also examined. We conclude with a discussion of how the rapidly expanding field of epigenetics, particularly regulation of gene expression by miRNAs and DNA methylation, is critical to control of cell and tissue differentiation, and how examination of these epigenetic processes has already begun to provide a better understanding of, and greater appreciation for, the complexities of palatal morphogenesis.
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Affiliation(s)
- Robert M Greene
- Department of Molecular, Cellular and Craniofacial Biology, University of Louisville, Birth Defects Center, ULSD, Louisville, Kentucky 40292, USA.
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17
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Brown GD, Nazarali AJ. Matrix metalloproteinase-25 has a functional role in mouse secondary palate development and is a downstream target of TGF-β3. BMC DEVELOPMENTAL BIOLOGY 2010; 10:93. [PMID: 20809987 PMCID: PMC2944159 DOI: 10.1186/1471-213x-10-93] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Accepted: 09/01/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND Development of the secondary palate (SP) is a complex event and abnormalities during SP development can lead to cleft palate, one of the most common birth disorders. Matrix metalloproteinases (MMPs) are required for proper SP development, although a functional role for any one MMP in SP development remains unknown. MMP-25 may have a functional role in SP formation as genetic scans of the DNA of human cleft palate patients indicate a common mutation at a region upstream of the MMP-25 gene. We report on the gene expression profile of MMP-25 in the developing mouse SP and identify its functional role in mouse SP development. RESULTS MMP-25 mRNA and protein are found at all SP developmental stages in mice, with the highest expression at embryonic day (E) 13.5. Immunohistochemistry and in situ hybridization localize MMP-25 protein and mRNA, respectively, to the apical palate shelf epithelial cells and apical mesenchyme. MMP-25 knockdown with siRNA in palatal cultures results in a significant decrease in palate shelf fusion and persistence of the medial edge epithelium. MMP-25 mRNA and protein levels significantly decrease when cultured palate shelves are incubated in growth medium with 5 μg/mL of a TGF-β3-neutralizing antibody. CONCLUSIONS Our findings indicate: (i) MMP-25 gene expression is highest at E12.5 and E13.5, which corresponds with increasing palate shelf growth downward alongside the tongue; (ii) MMP-25 protein and mRNA expression predominantly localize in the apical epithelium of the palate shelves, but are also found in apical areas of the mesenchyme; (iii) knockdown of MMP-25 mRNA expression impairs palate shelf fusion and results in significant medial edge epithelium remaining in contacted areas; and (iv) bio-neutralization of TGF-β3 significantly decreases MMP-25 gene expression. These data suggest a functional role for MMP-25 in mouse SP development and are the first to identify a role for a single MMP in mouse SP development.
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Affiliation(s)
- Graham D Brown
- Laboratory of Molecular Biology, College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada
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18
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Harrington EK, Coon DJ, Kern MF, Svoboda KKH. PTH stimulated growth and decreased Col-X deposition are phosphotidylinositol-3,4,5 triphosphate kinase and mitogen activating protein kinase dependent in avian sterna. Anat Rec (Hoboken) 2010; 293:225-34. [PMID: 19957341 DOI: 10.1002/ar.21072] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Type X collagen (Col-X) deposition is a marker of terminal differentiation during chondrogenesis, in addition to appositional growth and apoptosis. The parathyroid hormone/parathyroid hormone related peptide (PTH/PTHrP) receptor, or PPR, is a G-Protein coupled receptor (GPCR), which activates several downstream pathways, moderating chondrocyte differentiation, including suppression of Col-X deposition. An Avian sterna model was used to analyze the PPR GPCR downstream kinase role in growth rate and extracellular matrix (ECM) including Col-II, IX, and X. Phosphatidylinositol kinase (PI3K), mitogen activating protein kinase (MAPK) and protein kinase A (PKA) were inhibited with specific established inhibitors LY294002, PD98059, and H89, respectively to test the hypothesis that they could reverse/inhibit the PTH/PTHrP pathway. Excised E14 chick sterna were PTH treated with or without an inhibitor and compared to controls. Sternal length was measured every 24 hr. Cultured sterna were immuno-stained using specific antibodies for Col-II, IX, or X and examined via confocal microscopy. Increased growth in PTH-treated sterna was MAPK, PI3K, and PKA dose dependent, suggesting growth was regulated through multiple pathways. Col-X deposition was rescued in PTH-treated sterna in the presence of PI3K or MAPK inhibitors, but not with the PKA inhibitor. All three inhibitors moderately disrupted Col-II and Col-IX deposition. These results suggest that PTH can activate multiple pathways during chondrocyte differentiation.
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Affiliation(s)
- Erik Kern Harrington
- Department of Biomedical Sciences, Texas A&M Health Sciences Center, Dallas, 75246, USA
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19
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Jugessur A, Farlie PG, Kilpatrick N. The genetics of isolated orofacial clefts: from genotypes to subphenotypes. Oral Dis 2009; 15:437-53. [DOI: 10.1111/j.1601-0825.2009.01577.x] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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20
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Regulation of Epithelial-Mesenchymal Transition in Palatal Fusion. Exp Biol Med (Maywood) 2009; 234:483-91. [DOI: 10.3181/0812-mr-365] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
During palatal fusion, the midline epithelial seam between the palatal shelves degrades to achieve mesenchymal confluence. Morphological and molecular evidence support the theory that the epithelial-mesenchymal transition is one mechanism that regulates palatal fusion. It appears that transforming growth factor (TGF)-β signaling plays a role in palatal EMT. TGFβ3 is the main inducer in palatal fusion and activates both Smad-dependent and -independent signaling pathways, including the key EMT transcription factors, Lef1, Twist, and Snail1, in the MEE prior to the palatal EMT program. The roles and interactions among these transcription factors will be discussed.
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21
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Nawshad A. Palatal seam disintegration: to die or not to die? that is no longer the question. Dev Dyn 2008; 237:2643-56. [PMID: 18629865 DOI: 10.1002/dvdy.21599] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Formation of the medial epithelial seam (MES) by palatal shelf fusion is a crucial step of palate development. Complete disintegration of the MES is the final essential phase of palatal confluency with surrounding mesenchymal cells. In general, the mechanisms of palatal seam disintegration are not overwhelmingly complex, but given the large number of interacting constituents; their complicated circuitry involving feedforward, feedback, and crosstalk; and the fact that the kinetics of interaction matter, this otherwise simple mechanism can be quite difficult to interpret. As a result of this complexity, apparently simple but highly important questions remain unanswered. One such question pertains to the fate of the palatal seam. Such questions may be answered by detailed and extensive quantitative experimentation of basic biological studies (cellular, structural) and the newest molecular biological determinants (genetic/dye cell lineage, gene activity, kinase/enzyme activity), as well as animal model (knockouts, transgenic) approaches. System biology and cellular kinetics play a crucial role in cellular MES function; omissions of such critical contributors may lead to inaccurate understanding of the fate of MES. Excellent progress has been made relevant to elucidation of the mechanism(s) of palatal seam disintegration. Current understanding of palatal seam disintegration suggests epithelial-mesenchymal transition and/or programmed cell death as two most common mechanisms of MES disintegration. In this review, I discuss those two mechanisms and the differences between them.
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Affiliation(s)
- Ali Nawshad
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska 68583, USA.
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22
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Abstract
In palatogenesis, the MEE (Medial Edge Epithelium) cells disappear when palates fuse. We hypothesize that the MEE cells undergo EMT (Epithelial-Mesenchymal Transition) to achieve mesenchyme confluence. Twist has an important role in EMT for tumor metastasis. The purpose of this study was to analyze Twist function during palatal fusion. Twist protein was expressed in palatal shelves and MEE both in vivo and in vitro just prior to fusion. Twist mRNA increased in chicken palates 3 and 6 hr after TGFbeta3 treatment. Palatal fusion was decreased when cultured palatal shelves were treated with 200 nM Twist siRNA and the subcellular localization of beta-catenin was altered. Twist mRNA decreased in palatal shelves treated with TGFbeta3 neutralizing antibody or LY294002, a specific phosphatidylinositol-3 kinase (PI-3K) inhibitor. In summary, Twist is downstream of TGFbeta3 and PI-3K pathways during palatal fusion. However, decreasing Twist with siRNA did not completely block palate fusion, indicating that the function of Twist may be duplicated by other transcription factors.
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Affiliation(s)
- Wenli Yu
- Biomedical Sciences, Texas A&M Health Science Center, Baylor College of Dentistry, Dallas, Texas 75246, USA
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23
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Dudas M, Li WY, Kim J, Yang A, Kaartinen V. Palatal fusion - where do the midline cells go? A review on cleft palate, a major human birth defect. Acta Histochem 2007; 109:1-14. [PMID: 16962647 DOI: 10.1016/j.acthis.2006.05.009] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Revised: 05/26/2006] [Accepted: 05/31/2006] [Indexed: 01/14/2023]
Abstract
Formation of the palate, the organ that separates the oral cavity from the nasal cavity, is a developmental process characteristic to embryos of higher vertebrates. Failure in this process results in palatal cleft. During the final steps of palatogenesis, two palatal shelves outgrowing from the sides of the embryonic oronasal cavity elevate above the tongue, meet in the midline, and rapidly fuse together. Over the decades, multiple mechanisms have been proposed to explain how the superficial mucous membranes disappear from the contact line, thus allowing for normal midline mesenchymal confluence. A substantial body of experimental evidence exists for cell death, cell migration, epithelial-to-mesenchymal transdifferentiation (EMT), replacement through new tissue intercalation, and other mechanisms. However, the most recent use of gene recombination techniques in cell fate tracking disfavors the EMT concept, and suggests that apoptosis is the major fate of the midline cells during physiological palatal fusion. This article summarizes the benefits and drawbacks of histochemical and molecular tools used to determine the fates of cells within the palatal midline. Mechanisms of normal disintegration of the midline epithelial seam are reviewed together with pathologic processes that prevent this disintegration, thus causing cleft palate.
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Affiliation(s)
- Marek Dudas
- Developmental Biology Program, The Saban Research Institute of Childrens Hospital Los Angeles, Mail Stop 35, 4650 Sunset Blvd., Los Angeles, CA 90027, USA.
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24
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Nakajima A, Ito Y, Asano M, Maeno M, Iwata K, Mitsui N, Shimizu N, Cui XM, Shuler CF. Functional role of transforming growth factor-β type III receptor during palatal fusion. Dev Dyn 2007; 236:791-801. [PMID: 17295310 DOI: 10.1002/dvdy.21090] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The molecular regulation of palatogenesis continues to be an active area of investigation to provide a foundation for understanding the molecular etiology of cleft palate. Transforming growth factor (TGF) -beta type III receptor (TbetaR-III) has been shown to be specifically expressed in the medial edge epithelium at critical stages of palatal shelf adherence during palatogenesis. The aim of this study was to examine TbetaR-III mRNA localization and expression levels in vivo and to determine the requirement for TbetaR-III expression during palatal fusion in vitro. TbetaR-III gene expression was analyzed by in situ hybridization in tissue specimens and real-time reverse transcriptase-polymerase chain reaction using specific cells in the palatal shelf isolated by laser capture microdissection. TbetaR-III was knocked down in embryonic day (E) 13 palatal shelves in organ culture. Palatal shelf organ cultures were treated with small interfering RNA (siRNA) at final concentrations of 300, 400, and 500 nM, respectively. The treatment with siRNA specific for TbetaR-III decreased the amount of protein by approximately 75%. The reduction in TbetaR-III resulted in a delay in the process of palatal fusion compared with control. The protein expression of phospho-Smad2 was decreased in the TbetaR-III siRNA group. In addition, palatal organ cultures treated with TbetaR-III siRNA + rhTGF-beta3 completely fused by 72 hr in vitro. These results support our hypothesis that TbetaR-III has a critical role in the process of palatal fusion.
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Affiliation(s)
- Akira Nakajima
- Department of Orthodontics, Nihon University School of Dentistry, Tokyo, Japan
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25
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Kang P, Svoboda KKH. Epithelial-mesenchymal transformation during craniofacial development. J Dent Res 2006; 84:678-90. [PMID: 16040723 DOI: 10.1177/154405910508400801] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Epithelial to mesenchymal phenotype transition is a common phenomenon during embryonic development, wound healing, and tumor metastasis. This transition involves cellular changes in cytoskeleton architecture and protein expression. Specifically, this highly regulated biological event plays several important roles during craniofacial development. This review focuses on the regulation of epithelial-mesenchymal transformation (EMT) during neural crest cell migration, and fusion of the secondary palate and the upper lip.
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Affiliation(s)
- P Kang
- Graduate Endodontics Department, Texas A&M University System, Baylor College of Dentistry, 3302 Gaston Avenue, Dallas, TX 75266, USA
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26
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Gritli-Linde A. Molecular control of secondary palate development. Dev Biol 2006; 301:309-26. [PMID: 16942766 DOI: 10.1016/j.ydbio.2006.07.042] [Citation(s) in RCA: 210] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 07/24/2006] [Accepted: 07/28/2006] [Indexed: 12/17/2022]
Abstract
Compared with the embryonic development of other organs, development of the secondary palate is seemingly simple. However, each step of palatogenesis, from initiation until completion, is subject to a tight molecular control that is governed by epithelial-mesenchymal interactions. The importance of a rigorous molecular regulation of palatogenesis is reflected when loss of function of a single protein generates cleft palate, a frequent malformation with a complex etiology. Genetic studies in humans and targeted mutations in mice have identified numerous factors that play key roles during palatogenesis. This review highlights the current understanding of the molecular and cellular mechanisms involved in normal and abnormal palate development with special respect to recent advances derived from studies of mouse models.
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Affiliation(s)
- Amel Gritli-Linde
- Department of Oral Biochemistry, Sahlgrenska Academy at Göteborg University, Medicinaregatan 12F, Göteborg, Sweden.
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27
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Abstract
Transforming growth factor beta (TGFbeta), a multifunctional growth factor, is one of the most important ligands involved in the regulation of cell behavior in ocular tissues in physiological or pathological processes of development or tissue repair, although various other growth factors are also involved. Increased activity of this ligand may induce unfavorable inflammatory responses and tissue fibrosis. In mammals, three isoforms of TGFbeta, that is, beta1, beta2, and beta3, are known. Although all three TGFbeta isoforms and their receptors are present in ocular tissues, lack of TGFbeta2, but not TGFbeta1 or TGFbeta3, perturbs embryonic morphogenesis of the eyes in mice. Smads2/3 are key signaling molecules downstream of cell surface receptors for TGFbeta or activin. Upon TGF binding to the respective TGF receptor, Smads2/3 are phosphorylated by the receptor kinase at the C-terminus, form a complex with Smad4 and translocate to the nucleus for activation of TGFbeta gene targets. Moreover, mitogen-activated protein kinase, c-Jun N-terminal kinase, and p38 modulate Smad signals directly via Smad linker phosphorylation or indirectly via pathway crosstalk. Smad signals may therefore be a critical threrapeutic target in the treatment of ocular disorders related to fibrosis as in other systemic fibrotic diseases. The present paper reviews recent progress concerning the roles of TGFbeta signaling in the pathology of the eye.
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Affiliation(s)
- Shizuya Saika
- Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan.
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28
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29
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Jugessur A, Murray JC. Orofacial clefting: recent insights into a complex trait. Curr Opin Genet Dev 2005; 15:270-8. [PMID: 15917202 PMCID: PMC2442458 DOI: 10.1016/j.gde.2005.03.003] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2005] [Accepted: 03/18/2005] [Indexed: 11/20/2022]
Abstract
Orofacial clefts are common birth defects of multifactorial etiology. Several novel approaches have recently been applied to investigate the causes of clefts. These include examining Mendelian forms of clefting to identify genes that might also be implicated in isolated clefting, analyzing chromosomal rearrangements in which clefting is part of the resultant phenotype, studying animal models in which clefts arise either spontaneously or as a result of mutagenesis experiments, exploring how expression patterns correlate with gene function and examining the effects of gene-environment interactions. Together, these complementary strategies are providing researchers with new clues as to what mechanisms underlie orofacial clefting.
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Affiliation(s)
- Astanand Jugessur
- Department of Paediatrics, University of Iowa, Iowa City, IA 52242, USA
- Section for Epidemiology and Medical Statistics, Department of Public Health and Primary Health Care, University of Bergen, Norway
| | - Jeffrey C Murray
- Department of Paediatrics, University of Iowa, Iowa City, IA 52242, USA
- The Institute of Public Health, University of Southern Denmark, Odense, Denmark
- Corresponding author: Murray, Jeffrey C ()
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30
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Hay ED. The mesenchymal cell, its role in the embryo, and the remarkable signaling mechanisms that create it. Dev Dyn 2005; 233:706-20. [PMID: 15937929 DOI: 10.1002/dvdy.20345] [Citation(s) in RCA: 453] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
This review centers on the role of the mesenchymal cell in development. The creation of this cell is a remarkable process, one where a tightly knit, impervious epithelium suddenly extends filopodia from its basal surface and gives rise to migrating cells. The ensuing process of epithelial-mesenchymal transformation (EMT) creates the mechanism that makes it possible for the mesenchymal cell to become mobile, so as to leave the epithelium and move through the extracellular matrix. EMT is now recognized as a very important mechanism for the remodeling of embryonic tissues, with the power to turn an epithelial somite into sclerotome mesenchyme, and the neural crest into mesenchyme that migrates to many targets. Thus, the time has come for serious study of the underlying mechanisms and the signaling pathways that are used to form the mesenchymal cell in the embryo. In this review, I discuss EMT centers in the embryo that are ready for such serious study and review our current understanding of the mechanisms used for EMT in vitro, as well as those that have been implicated in EMT in vivo. The purpose of this review is not to describe every study published in this rapidly expanding field but rather to stimulate the interest of the reader in the study of the role of the mesenchymal cell in the embryo, where it plays profound roles in development. In the adult, mesenchymal cells may give rise to metastatic tumor cells and other pathological conditions that we will touch on at the end of the review.
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Affiliation(s)
- Elizabeth D Hay
- Harvard Medical School, Department of Cell Biology, Boston, Massachusetts 02115, USA.
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31
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Dudas M, Kaartinen V. Tgf-beta superfamily and mouse craniofacial development: interplay of morphogenetic proteins and receptor signaling controls normal formation of the face. Curr Top Dev Biol 2005; 66:65-133. [PMID: 15797452 DOI: 10.1016/s0070-2153(05)66003-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Marek Dudas
- Developmental Biology Program at the Saban Research Institute of Children's Hospital Los Angeles, Los Angeles, California 90027, USA
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32
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Nawshad A, LaGamba D, Hay ED. Transforming growth factor beta (TGFbeta) signalling in palatal growth, apoptosis and epithelial mesenchymal transformation (EMT). Arch Oral Biol 2004; 49:675-89. [PMID: 15275855 DOI: 10.1016/j.archoralbio.2004.05.007] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/11/2004] [Indexed: 11/26/2022]
Abstract
Formation of the medial edge epithelial (MEE) seam by fusing the palatal shelves is a crucial step of palate development. The opposing shelves adhere to each other at first by adherens junctions, then by desmosomes in the MEE. The MEE seam disappears by epithelial mesenchymal transformation (EMT), which creates confluence of connective tissue across the palate. Cleft palate has a mutifactorial etiology that often includes failure of adherence of apposing individual palatal shelves and/or EMT of the MEE. In this review, we first discuss TGFbeta biology, including functions of TGFbeta isoforms, receptors, down stream transcription factors, endosomes, and signalling pathways. Different isoforms of the TGFbeta family play important roles in regulating various aspects of palate development. TGFbeta1 and TGFbeta2 are involved in growth, but it is TGFbeta3 that regulates MEE transformation to mesenchyme to bring about palatal confluence. Its absence results in cleft palate. Understanding of TGFbeta family signalling is thus essential for development of therapeutic strategies. Because TGFbeta3 and its downstream target, LEF1, play the major role in epithelial transformation, it is important to identify the signalling pathways they use for palatal EMT. Here, we will discuss in detail the mechanisms of palatal seam disappearance in response to TGFbeta3 signalling, including the roles, if any, of growth and apoptosis, as well as EMT in successful MEE adherence and seam formation. We also review recent evidence that TGFbeta3 uses Smad2 and 4 during palatal EMT, rather than beta-Catenin, to activate LEF1. TGFbeta1 has been reported to use non-Smad signalling using RhoA or MAPKinases in vitro, but these are not involved in activation of palatal EMT in situ. A major aim of this review is to document the genetic mechanisms that TGFbeta uses to bring about palatal EMT and to compare these with EMT mechanisms used elsewhere.
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Affiliation(s)
- A Nawshad
- Department of Cell Biology, Harvard Medical School, 220 Longwood Ave, Goldensen Bldg, Room 342, Boston, MA 02115, USA
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33
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Dudas M, Nagy A, Laping NJ, Moustakas A, Kaartinen V. Tgf-beta3-induced palatal fusion is mediated by Alk-5/Smad pathway. Dev Biol 2004; 266:96-108. [PMID: 14729481 DOI: 10.1016/j.ydbio.2003.10.007] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cleft palate is among the most common birth defects in humans, caused by a failure in the complex multistep developmental process of palatogenesis. It has been recently shown that transforming growth factor beta3 (Tgf-beta3) is an absolute requirement for successful palatal fusion, both in mice and humans. However, very little is known about the mechanisms of Tgf-beta3 signaling during this process. Here we show that putative Tgf-beta type I receptors, Alk-1, Alk-2, and Alk-5, are all endogenously expressed in the palatal epithelium. Activation of Alk-5 in the Tgf-beta3 (-/-) palatal epithelium is able to rescue palatal fusion, whereas inactivation of Alk-5 in the wild-type palatal epithelium prevents palatal fusion. The effect of Alk-2 is similar, but less pronounced. The induction of fusion by activation of Alk-5 or Alk-2 is stronger in the posterior parts of the palates at the embryonic day 14 (E14), while their activation at E13.5 also restores anterior fusion, reflecting the natural anterior-posterior direction of palate maturation in vivo. We also show that Smad2 is endogenously activated in the palatal midline epithelial seam (MES) during the fusion process. By using a mutant Alk-5 receptor that is an active kinase but is unable to activate Smads, we show that activation of Smad-independent Tgf-beta responses is not sufficient to induce fusion of shelves deficient in Tgf-beta3. Based on these observations, we conclude that the Smad2-dependent Alk-5 signaling pathway is dominant in palatal fusion driven by Tgf-beta3.
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Affiliation(s)
- Marek Dudas
- Developmental Biology Program, Department of Pathology of University of Southern California, Childrens Hospital Los Angeles, Los Angeles, CA 90027, USA
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34
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Gurley JM, Wamsley MS, Sandell LJ. Alterations in Apoptosis and Epithelial-Mesenchymal Transformation in an In Vitro Cleft Palate Model. Plast Reconstr Surg 2004; 113:907-14. [PMID: 15108882 DOI: 10.1097/01.prs.0000105342.08168.13] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The processes of apoptosis and epithelial-mesenchymal transformation have been identified as two major mechanisms by which secondary palatal shelves achieve fusion. The aim of this study was to investigate alterations in these mechanisms by changing the physical distance between paired palatal shelves in an in vitro model of palatogenesis. Wild-type palatal pairs were dissected from E13.5 CD1 mouse embryos and allowed to grow in tissue culture for 48 hours at various intershelf distances. During the fusion process, medial edge epithelial cell fate was assessed using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining, to evaluate apoptosis, and carboxyfluorescence (carboxy-2,7'-dichlorofluorescein diacetate succinimidyl ester) labeling, to measure transformation to mesenchymal cells. Palatal pairs separated in culture greater than or equal to 0.4 mm failed to fuse. TUNEL staining showed that the number of apoptotic cells in the palatal shelves increased as the intershelf distance increased, becoming marked in shelves that did not achieve fusion. The amount of epithelial-mesenchymal transformation, however, decreased with increasing intershelf distance. These results suggest that the contribution of epithelial-mesenchymal transformation and apoptosis to palatal shelf development and fusion can be altered by physical proximity. Therefore, one mechanism behind clefting in utero may result from an imbalance in epithelial-mesenchymal transformation and apoptosis as observed in vitro where palatal shelves are challenged to fuse by physical separation. This effect could be significant in the understanding and treatment of developmental palatal abnormalities. Perhaps in utero manipulation of intershelf spacing or epithelial-mesenchymal transformation and/or apoptosis could reverse the clefting paradigm.
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Affiliation(s)
- Judith M Gurley
- Division of Plastic Surgery, Department of Surgery, St. Louis Children's Hospital, St. Louis, MO 63110, USA.
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Nawshad A, Hay ED. TGFbeta3 signaling activates transcription of the LEF1 gene to induce epithelial mesenchymal transformation during mouse palate development. ACTA ACUST UNITED AC 2004; 163:1291-301. [PMID: 14691138 PMCID: PMC2173726 DOI: 10.1083/jcb.200306024] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Epithelial mesenchymal transformation (EMT) of the medial edge epithelial (MEE) seam creates palatal confluence. This work aims to elucidate the molecular mechanisms by which TGFβ3 brings about palatal seam EMT. We collected mRNA for PCR analysis from individual transforming MEE cells by laser microdissection techniques and demonstrated that TGFβ3 stimulates lymphoid-enhancing factor 1 (LEF1) mRNA synthesis in MEE cells. We show with antisense β-catenin oligonucleotides that up-regulated LEF1 is not activated by β-catenin in palate EMT. We ruled out other TGFβ3 targets, such as RhoA and MEK1/2 pathways, and we present evidence using dominant-negative Smad4 and dominant-negative LEF1 showing that TGFβ3 uses Smads both to up-regulate synthesis of LEF1 and to activate LEF1 transcription during induction of palatal EMT. When phospho-Smad2 and Smad4 are present in the nucleus, LEF1 is activated without β-catenin. Our paper is the first to show that the Smad2,4/LEF1 complex replaces β-catenin/LEF1 during activation of EMT in vivo by TGFβ3.
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Affiliation(s)
- Ali Nawshad
- Department of Cell Biology, Harvard Medical School, 220 Longwood Ave., B-1, Room 342, Boston, MA 02115-6092, USA
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Kang P, Svoboda KKH. Nicotine inhibits palatal fusion and modulates nicotinic receptors and the PI-3 kinase pathway in medial edge epithelia. Orthod Craniofac Res 2003; 6:129-42. [PMID: 12962196 PMCID: PMC2862388 DOI: 10.1034/j.1600-0544.2003.02236.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVES To analyze the effects of nicotine on palatal fusion inhibition in vitro and determine if nicotine modulated transforming growth factor beta3 or phosphatidylinositol-3 kinase signaling. A second objective was to determine the localization and regulation of nicotinic receptors in the medial edge epithelia (MEE) during palatal fusion. DESIGN Palatal shelves from embryonic day (E) 13.5 mice were cultured in serum free media and treated with 0, 0.06, 0.6, or 6 mM nicotine, nicotinic receptor antagonist alpha-bungarotoxin, or the combination of nicotine and alpha-bungarotoxin. Tissues harvested at 72 h were analyzed for epithelial-mesenchymal transformation (EMT) and fusion. MEE samples collected at 20 h were analyzed for phosphorylated Akt-Ser473, phosphorylated Smad2, and nicotinic receptors. RESULTS Nicotine inhibited palatal fusion in vitro in a dose dependent manner. Activated Akt-Ser473 was greater in control MEE than in nicotine treated tissues; while there was no difference in activated Smad2 between groups. The alpha7 subunit of nicotinic receptor was expressed in MEE during palate fusion and increased in nicotine treated tissues. Alpha-bungarotoxin did not rescue the nicotine treated palates. CONCLUSION Nicotine treatment had no effect on Smad2, but caused a down regulation of the PI-3 kinase pathway that may have contributed to inhibiting palatal fusion in vitro.
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Affiliation(s)
- P Kang
- Biomedical Sciences, Texas A & M University System, Baylor College of Dentistry, Dallas, TX 75246, USA
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