ABSTRACT
Interdigital cell death is a physiological regression process responsible for sculpturing the digits in the embryonic vertebrate limb. Changes in the intensity of this degenerative process account for the different patterns of interdigital webbing among vertebrate species. Here, we show that Reelin is present in the extracellular matrix of the interdigital mesoderm of chick and mouse embryos during the developmental stages of digit formation. Reelin is a large extracellular glycoprotein which has important functions in the developing nervous system, including neuronal survival; however, the significance of Reelin in other systems has received very little attention. We show that reelin expression becomes intensely downregulated in both the chick and mouse interdigits preceding the establishment of the areas of interdigital cell death. Furthermore, fibroblast growth factors, which are cell survival signals for the interdigital mesoderm, intensely upregulated reelin expression, while BMPs, which are proapototic signals, downregulate its expression in the interdigit. Gene silencing experiments of reelin gene or its intracellular effector Dab-1 confirmed the implication of Reelin signaling as a survival factor for the limb undifferentiated mesoderm. We found that Reelin activates canonical survival pathways in the limb mesoderm involving protein kinase B and focal adhesion kinase. Our findings support that Reelin plays a role in interdigital cell death, and suggests that anoikis (apoptosis secondary to loss of cell adhesion) may be involved in this process.
Subject(s)
Cell Adhesion Molecules, Neuronal/metabolism , Embryo, Mammalian/metabolism , Embryo, Mammalian/pathology , Extracellular Matrix Proteins/metabolism , Extracellular Matrix/metabolism , Extremities/embryology , Extremities/pathology , Nerve Tissue Proteins/metabolism , Serine Endopeptidases/metabolism , Animals , Bone Morphogenetic Proteins/metabolism , Cell Adhesion Molecules, Neuronal/genetics , Cell Death , Cell Survival/genetics , Chick Embryo , Chickens , Extracellular Matrix Proteins/genetics , Fibroblast Growth Factors/metabolism , Flow Cytometry , Focal Adhesion Protein-Tyrosine Kinases/metabolism , Gene Expression Regulation, Developmental , Mesoderm/enzymology , Mesoderm/pathology , Mice , Necrosis , Nerve Tissue Proteins/genetics , Proto-Oncogene Proteins c-akt/metabolism , Reelin Protein , Serine Endopeptidases/genetics , Signal Transduction/geneticsSubject(s)
Cell Cycle Proteins/genetics , Gene Expression Regulation, Developmental , RNA, Messenger , Animals , Blotting, Northern , Cdh1 Proteins , Cell Cycle Proteins/biosynthesis , Cell Cycle Proteins/metabolism , Cell Line , Hematopoietic Stem Cells/metabolism , Mice , Organ Specificity/geneticsABSTRACT
This paper deals with the use of several methods to characterize the chemical surface groups of carbon materials. Several samples embracing a wide range of acidic and basic characteristics have been used for this purpose. The quantitative determinations have been carried out by selective titrations in aqueous solutions, thermal programmed desorption connected to mass spectrometry (TPD-MS), and ammonia adsorption-desorption, measured by thermogravimetry (TG). The results show some inconsistencies between the different experimental methods. These mainly arise because chemical transformations can be produced during the experiments. Moreover, the textural characteristics of the carbon materials and the existence of pi electrons on the graphitic planes are important factors to be considered in the discussion of the results.
