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Palatal Fusion (palatal + fusion)
Selected AbstractsThe role of twist during palate development,DEVELOPMENTAL DYNAMICS, Issue 10 2008Wenli Yu 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 TGF,3 treatment. Palatal fusion was decreased when cultured palatal shelves were treated with 200 nM Twist siRNA and the subcellular localization of ,-catenin was altered. Twist mRNA decreased in palatal shelves treated with TGF,3 neutralizing antibody or LY294002, a specific phosphatidylinositol-3 kinase (PI-3K) inhibitor. In summary, Twist is downstream of TGF,3 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. Developmental Dynamics 237:2716,2725, 2008. © 2008 Wiley-Liss, Inc. [source] Inhibition of SMAD2 expression prevents murine palatal fusionDEVELOPMENTAL DYNAMICS, Issue 7 2006Nobuyuki Shiomi Abstract Transforming growth factor (TGF)-beta 3 is known to regulate the disappearance of murine medial edge epithelium (MEE) during palatal fusion. Our previous studies showed that SMAD2, a TGF-beta signaling mediator, was expressed and phosphorylated primarily in the MEE and that SMAD2 phosphorylation in the MEE was temporospatially regulated by TGF-beta 3. The goal of this study was to examine the requirement for SMAD2 to complete the developmental events necessary for palatal fusion. SMAD2 expression was inhibited with Smad2 siRNA transfection into palatal tissues in vitro. The results showed that Smad2 siRNA transfection resulted in the maintenance of MEE cells in the palatal midline. Western blot and immunofluorescence analyses confirmed that the endogenous SMAD2 and phospho-SMAD2 levels were reduced following siRNA transfection. The SMAD3 level was not altered by the Smad2 siRNA transfection. The persistence of the MEE and the decreased SMAD2/phospho-SMAD2 levels were coincident with increased MEE cell proliferation. Addition of exogenous TGF-beta 3 increased p-SMAD2 level but not the total SMAD2 level. Therefore, exogenous TGF-beta 3 was not able to induce p-SMAD2 enough to rescue the palatal phenotype in the Smad2 siRNA group. The results indicated that the endogenous SMAD2 level is crucial in the regulation of disappearance of MEE during palatal fusion. Developmental Dynamics 235:1785,1793, 2006. © 2006 Wiley-Liss, Inc. [source] PDGFR-, signaling is critical for tooth cusp and palate morphogenesisDEVELOPMENTAL DYNAMICS, Issue 1 2005Xun Xu Abstract Platelet-derived growth factor receptor alpha (PDGFR-,) and PDGF ligands are key regulators for embryonic development. Although Pdgfr, is spatially expressed in the cranial neural crest (CNC)-derived odontogenic mesenchyme, mice deficient for Pdgfr, are embryonic lethal, making it impossible to investigate the functional significance of PDGF signaling in regulating the fate of CNC cells during tooth morphogenesis. Taking advantage of the kidney capsule assay, we investigated the biological function of PDGF signaling in regulating tooth morphogenesis. Pdgfr, and Pdgfa are specifically and consistently expressed in the CNC-derived odontogenic mesenchyme and the dental epithelium, respectively, throughout all stages of tooth development, suggesting a paracrine function of PDGF signaling in regulating tooth morphogenesis. Highly concentrated expression patterns of Pdgfr, and Pdgfa are associated with the developing dental cusp, suggesting possible functional importance of PDGF signaling in regulating cusp formation. Loss of the Pdgfr, gene does not affect proper odontoblasts proliferation and differentiation in the CNC-derived odontogenic mesenchyme but perturbs the formation of extracellular matrix and the organization of odontoblast cells at the forming cusp area, resulting in dental cusp growth defect. Pdgfr,,/, mice have complete cleft palate. We show that the cleft palate in Pdgfr, mutant mice results from an extracellular matrix defect within the CNC-derived palatal mesenchyme. The midline epithelium of the mutant palatal shelf remains functionally competent to mediate palatal fusion once the palatal shelves are placed in close contact in vitro. Collectively, our data suggests that PDGFR, and PDGFA are critical regulators for the continued epithelial,mesenchymal interaction during tooth and palate morphogenesis. Disruption of PDGFR, signaling disturbs the growth of dental cusp and interferes with the critical extension of palatal shelf during craniofacial development. Developmental Dynamics 232:75,84, 2005. © 2004 Wiley-Liss, Inc. [source] TGF-,3,dependent SMAD2 phosphorylation and inhibition of MEE proliferation during palatal fusionDEVELOPMENTAL DYNAMICS, Issue 3 2003Xiao-Mei Cui Abstract Transforming growth factor (TGF) -,3 is known to selectively regulate the disappearance of murine medial edge epithelium (MEE) during palatal fusion. Previous studies suggested that the selective function of TGF-,3 in MEE was conducted by TGF-, receptors. Further studies were needed to demonstrate that the TGF-, signaling mediators were indeed expressed and phosphorylated in the MEE cells. SMAD2 and SMAD3 were both present in the MEE, whereas SMAD2 was the only one phosphorylated during palatal fusion. SMAD2 phosphorylation was temporospatially restricted to the MEE and correlated with the disappearance of the MEE. No phosphorylated SMAD2 was found in MEE in TGF-,3,/, mice, although nonphosphorylated SMAD2 was present. The results suggest that TGF-,3 is required for initiating and maintaining SMAD2 phosphorylation in MEE. Phospho-SMAD3 was not detectable in palate during normal palatal fusion. Previous results suggested TGF-,,induced cessation of DNA synthesis in MEE cells during palatal fusion in vitro. The present results provide evidence that inhibition of MEE proliferation in vivo was controlled by endogenous TGF-,3. The number of 5-bromo-2,-deoxyuridine (BrdU) -labeled MEE cells was significantly reduced in TGF-,3+/+ compared with TGF-,3,/, mice when the MEE seam formed (t -test, P < 0.05). This finding suggests that TGF-,3 is required for inhibiting MEE proliferation during palatal fusion. The inhibition of MEE proliferation may be mediated by TGF-,3,dependent phosphorylation of SMAD2. Developmental Dynamics 227:387,394, 2003. © 2003 Wiley-Liss, Inc. [source] Tissue-specific expression of Cre recombinase from the Tgfb3 locusGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 2 2008Liang-Tung Yang Abstract Tgfb3, a member of the TGF-, superfamily, is tightly regulated, both spatially and temporally, during embryogenesis. Previous mouse knockout studies have demonstrated that Tgfb3 is absolutely required for normal palatal fusion and pulmonary development. We have generated a novel tool to ablate genes in Tgfb3 -expressing cells by targeting the promoterless Cre-pgk-Neo cassette into exon 1 of the mouse Tgfb3 gene, which generates a functionally null Tgfb3 allele. Using the Rosa26 reporter assay, we demonstrate that Cre -induced recombination was already induced at embryonal day 10 (E10) in the ventricular myocardium, limb buds, and otic vesicles. At E14, robust recombination was detected in the prefusion palatal epithelium. Deletion of the TGF-, type I receptor Alk5 (Tgfbr1) specifically in Tgfb3 expressing cells using the Tgfb3-Cre driver line lead to a cleft palate phenotype similar to that seen in conventional Tgfb3 null mutants. In addition, Alk5/ Tgfb3-Cre mice displayed hydrocephalus, and severe intracranial bleeding due to germinal matrix hemorrhage. genesis 46:112,118, 2008. © 2008 Wiley-Liss, Inc. [source] | ||||||||||