Death is the major fate of medial edge epithelial cells and the cause of basal lamina degradation during palatogenesis.
ABSTRACT During mammalian development, a pair of shelves fuses to form the secondary palate, a process that requires the adhesion of the medial edge epithelial tissue (MEE) of each shelf and the degeneration of the resulting medial epithelial seam (MES). It has been reported that epithelial-mesenchymal transformation (EMT) occurs during shelf fusion and is considered a fundamental process for MES degeneration. We recently found that cell death is a necessary process for shelf fusion. These findings uncovered the relevance of cell death in MES degeneration; however, they do not discard the participation of other processes. In the present work, we focus on the evaluation of the processes that could contribute to palate shelf fusion. We tested EMT by traditional labeling of MEE cells with a dye, by infection of MEE with an adenovirus carrying the lacZ gene, and by fusing wild-type shelves with the ones from EGFP-expressing mouse embryos. Fate of MEE labeled cells was followed by culturing whole palates, or by a novel slice culture system that allows individual cells to be followed during the fusion process. Very few labeled cells were found in the mesenchyme compartment, and almost all were undergoing cell death. Inhibition of metalloproteinases prevented basal lamina degradation without affecting MES degeneration and MEE cell death. Remarkably, independently of shelf fusion, activation of cell death promoted the degradation of the basal lamina underlying the MEE ('cataptosis'). Finally, by specific labeling of periderm cells (i.e. the superficial cells that cover the basal epithelium), we observed that epithelial triangles at oral and nasal ends of the epithelial seam do not appear to result from MEE cell migration but rather from periderm cell migration. Inhibition of migration or removal of these periderm cells suggests that they have a transient function controlling MEE cell adhesion and survival, and ultimately die within the epithelial triangles. We conclude that MES degeneration occurs almost uniquely by cell death, and for the first time we show that this process can activate basal lamina degradation during a developmental process.
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ABSTRACT: To identify the differential protein pattern in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced cleft palates using a proteomic approach. At gestation day (GD) 12, TCDD (64 g/kg; n = 30) or corn oil control (n = 30) was given to time-pregnant C57BL/6J mice by gavage. The anatomical, histological, proteomic changes in the palates of the fetal mice were studied on GD18. Total protein was extracted from the palate tissue and examined by 2-dimensional gel electrophoresis (2-DE). Spots differentially expressed between the two groups were selected for analysis by matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The proteins were identified by data searching in the Mascot database. In TCDD group, the incidence of cleft palate was 100%. Ten differential protein spots with the largest fold change were selected for further identification by mass spectrometry, 7 showed significantly higher volumes and 3 showed significantly lower volumes in TCDD palates than the control palates (all p<0.05). Peroxiredoxin-1 were robustly up-regulated in the cleft palate group, as well proteins linked to energy metabolism, cell migration, and apoptosis. Peroxiredoxin-1 protein may be associated with cleft palate in mice induced by TCDD. The embryo mouse palate tissues energy metabolism cells migration/apoptosis related proteins have the disorder.Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association 04/2012; 50(7):2270-4. · 2.99 Impact Factor
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ABSTRACT: Interdigital cell death (ICD) is the oldest and best-studied model of programmed cell death (PCD) in vertebrates. The classical view of ICD function is the separation of digits by promotion of tissue regression. However, in addition, ICD can contribute to digit individualization by restricting interdigital tissue growth. Depending on the species, the relative contribution of either regression or growth-restricting functions of ICD to limb morphogenesis may differ. Under normal conditions, most cells appear to die by apoptosis during ICD. Accordingly, components of the apoptotic machinery are found in the interdigits, though their role in the initiation and execution of cell death is yet to be defined. Fgf8 has been identified as a survival factor for the distal mesenchymal cells of the limb such that ICD can initiate following specific downregulation of Fgf8 expression in the ectoderm overlying the interdigital tissue. On the other hand, Bmps may promote cell death directly by acting on the interdigital tissue, or indirectly by downregulating Fgf8 expression in the ectoderm. In addition, retinoic acid can activate ICD directly or through a Bmp-mediated mechanism. Interactions at different levels between these factors establish the spatiotemporal patterning of ICD activation. Defining the regulatory network behind ICD activation will greatly advance our understanding of the mechanisms controlling PCD in general.Embryologia 02/2011; 53(2):245-58. · 2.21 Impact Factor
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ABSTRACT: The effect of all-trans retinoic acid (atRA) on palatal fusion and the underlying mechanisms were investigated using organ culture. Compared with control group, the atRA-treated group (1 μM and 5 μM) had more medial edge epithelium (ME) remaining within the midline epithelial seam (MES). At 10 μM atRA, the opposing shelves were not in contact at the culture end (72 h). Cell death detection by TUNEL and laminin immunohistochemistry demonstrated that atRA (5 μM) induced apoptosis in mesenchyme and inhibited degradation of basal lamina within MES. Notably, migration and apoptosis of ME cells and degradation of basal lamina within MES markedly represented vehicle control palatal shelves in culture. Additionally, apoptosis was not detected in mesenchyme of control palatal shelves. Immunoblotting analysis revealed that Smad2 and Smad3 were endogenously activated and expression of Smad7 was inhibited during the fusion process. In contrast, atRA treatment abrogated phosphorylation of Smad2 and Smad3 and inducible expression of Smad7 in ME. From these data, it is assumed that inhibition of Smad pathway by atRA in ME may play a critical role in abrogation of the ME cell apoptosis and degradation of the basal laminin, which might contribute to failure of palatal fusion.Acta Biologica Hungarica 06/2011; 62(2):142-50. · 0.50 Impact Factor