Cessation of cytokeratin expression in a rat hepatoma cell line lacking differentiated functions (original) (raw)
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Experimental Cell Research, 1981
The intermediate filament systems of the established epithelial cell lines HeLa and PtK, have been characterized by electron microscopy using indirect immunoferritin labelling. The results provide a direct ultrastructural confirmation of the proposal based on indirect immunofluorescence microscopy, that vimentin and cytokeratin fibrils constitute two distinct IO nm filament systems in much of the cell body. In agreement both with classical histology and with the finding that cytokeratins are typically present in many epithelial tissues, demosome-attached IO nm filaments (tonofilaments) were found to be of the cytokemtin type. Vimentin, but not cytokeratin filaments were translocated into juxtanuclear caps after exposure of the cells to colcemid. Regions of the cytoplasm where the two distinct systems form mixed bundles were identified and both side-by-side arrangements and the occurrence of vimentin fibers in a sheath-like structure around a cytokeratin filament core are described. Our results emphasize that the two systems interact but differ in their organization and control. 20-81 IX12 E.rp Cdl Kcs 132 f/98/~
The Journal of Cell Biology, 1984
The expression of cytokeratins and vimentin was investigated in Madin-Darby bovine epithelial cells (MDBK) in culture under conditions of varied cell spreading and cellcell contact. When extensive cell-cell contact was achieved by seeding cells at high density in monolayer, or in suspension culture in which multicellular aggregates formed, the cells synthesized high levels of cytokeratins and low levels of vimentin. In contrast, in sparse monolayer and suspension cultures where cell-cell contact was minimal, the cells synthesized very low levels of cytokeratins. The level of vimentin synthesis was high in sparse monolayer culture and was low in both sparse and dense suspension cultures. The ratio of cytokeratin to vimentin synthesis was not affected during the cell cycle, or when cell growth was inhibited by ara C and in serum-starvation-stimulation experiments. The variations in the synthesis of cytokeratins and vimentin under the various culture conditions were also reflected at the level of mRNA activity in a cell-free in vitro translation system and as determined by RNA blot hybridization with cDNA to vimentin and cytokeratins. The results suggest that control of cytokeratin synthesis involves cell-cell contact, characteristic of epithelia in vivo, while vimentin synthesis responds to alterations in cell spreading.
A dual expression of cytokeratin and neurofilaments in bronchial carcinoid cells
International Journal of Cancer, 1985
Intermediate filaments (IF) are ubiquitous cytoplasmic structures which, by virtue of their cell-and tissue-type-specific characteristics, are widely used as markers of tissue derivation and as differential diagnostic aids in surgical pathology. In contradistinction to other IFs, vimentin filaments, characteristic of mesenchymal cells, may be coexpressed with other celltype specific IFs-cytokeratin filaments, desmin filaments, glial filaments and neurofilaments-in some tumor cells, embryonic cells, and cells in vitro. In this study we describe a novel type of IF coexpression which does not involve vimentin-filaments, viz. the presence of both cytokeratin filaments and neurofilaments in human bronchial carcinoid tumor cells.
Differentiation, 1982
Teratocarcinoma differentiation has been studied using sera specific for each of the five intermediate filament (IF) classes. These antibodies distinguish cells of epithelial, muscle, neural, astrocytic, and mesenchymal origin. In embryoid bodies, derived from embryo transplants and obtained in the ascitic fluid by transplantation of teratocarcinoma, the cells of the inner cellular mass did not express any of these intermediate filament types while the outer cells expressed cytokeratin. Intermediate filament expression in the embryoid body thus appears analogous to that in the blastocyst and differs from that in embryonal carcinoma (EC) lines. Twelve EC lines have now been shown to express vimentin although in some EC lines not all cells express vimentin. Other established permanent differentiated cell lines, derived from EC lines in vitro or from tumors in vivo, have been characterized with respect to the type of IF they contain. The distribution of different IF types has been examined in EC cells induced to differentiate by addition of retinoic acid. The proportion of cells expressing each type of intermediate filament appears to depend on the EC cell line used, on the inducing agent, and on the length of treatment. Thus, for instance, F9 cells express cytokeratin, PCC3 derivatives express vimentin, many 1009 derivatives express either glial fibrillar acidic protein (GFA) or neurofilament proteins. Overall the results obtained are in excellent agreement with emerging principles of intermediate filament expression during embryonic differentiation, thus emphasizing the potential use of the various EC lines to study differentiation in culture.
Biochemistry and Cell Biology, 1992
T51B, a cell line of the rat liver nonparenchymal cell compartment, contains a cytokeratin (CK) pair composed of CK8, a CK typical of simple epithelium, and CK14, a CK usually present in proliferative stratified epithelium. T51B-Ni, a subclone selected by prolonged exposure of the parental clone to nickel subsulfide contains CK8 and CK18 (its usual partner in simple epithelium), as well as CK14, at a lower level. The two clones have comparable levels of vimentin. Northern blot analyses of cytoplasmic mRNA demonstrated that the differences in the steady state mRNA levels of each CK paralleled those observed at the protein level, thus showing that the regulatory events occurred prior to translation. The most prominent difference was a 30-fold higher level of CK18 mRNA in T51B-Ni cells. Run-off assays of isolated nuclei revealed that the level of CK8, CK14, and vimentin was regulated primarily at the transcriptional level. However, the large increase in CK18 mRNA levels in T51B-Ni cells did not result from a corresponding increase in the relative level of CK18 gene transcription nor from a change in cytoplasmic CK18 mRNA stability. Comparative Northern blot analyses of nuclear and cytoplasmic mRNAs further suggested that the control of CK18 gene expression in T51B cells is post-transcriptionally mediated by nuclear events.
Quantitative image analysis of cytokeratin filament distribution during fetal rat liver development
Hepatology, 1996
The construction of the liver parenchyma throughout Recent reports suggest that not only chemical but also mechanical influences from the cellular environment development depends on the elaboration of intercellucould have profound effects on gene activity and could lar contacts (between epithelial cells, as well as beact on cell differentiation and proliferation. These mechtween epithelial and mesenchymal cells) and on cellanisms involve a tissue matrix system, which includes matrix interactions. extracellular matrix, nuclear matrix, and cytoskeleton. It has been demonstrated that the extracellular ma-Supposing that the cytoskeleton mediates mechanical trix components regulate hepatic gene expression and transductions from the cell environment to the nucleus, thus play a crucial role in hepatocyte differentiasignificant differences in the spatial distribution of the tion, both in normal liver and in pathological condicytoskeleton network could reflect variations in envitions. 1-7 In the fetal liver, the chemical composition of ronmental signals. Hepatocytes during fetal developthe extracellular matrix is different from the adult ment provide a useful model to study such variations, liver, laminin being the main component. 2,8,9 Therefore, because a progressive establishment of intercellular fetal hepatoblasts are surrounded by a matrix that contact is reported. The aim of this work is to discriminate steps in hepatocyte differentiation from fetal to might be similar to that of the periportal zone in adult adult livers, using computerized quantitative image liver. 6 analysis of cytokeratin (C 8) immunofluorescent localiza-It is well established, especially in cultured cells, that tion, visualized by confocal scanning laser microscopy. integrins mediate cell adhesion to extracellular matrix The filament structure is represented by the gray-scale containing RDG peptides (arg-gly-asp), and that stress skeleton of the digital images obtained by specially defiber organization in focal adhesions induces tyrosine signed segmentation methods. A set of line features was phosphorylation of focal adhesion kinase, mitogen-actiinvestigated, including number and length of lines, orivated protein kinase activation, and nuclear translocaentation of lines, and the fractal dimension of the filation. 10-13 Integrins physically link the extracellular mament network. The features studied showed highly sigtrix to the cytoplasmic actin cytoskeletal network and nificant differences throughout liver development, with can function as signal-transducting receptors capable an increase of the total amount of cytokeratin filaments. of modulating cell growth and gene expression. 14,15 We could also demonstrate a modification in the structure of the network, being more and more dense, with
Co-expression of cytokeratin and vimentin filaments in rete testis and epididymis
Virchows Archiv A Pathological Anatomy and Histopathology, 1991
In 11 testes of different developmental stages (from 10-week-old embryos to adult) the cytokeratin and vimentin expression patterns of rete testis and epididymis were investigated immunohistochemically in formaldehyde-fixed paraffin-embedded material. In addition, immunofluorescence microscopy including double immunofluorescence was performed on frozen sections of 3 of these 11 cases. Rete testis and epididymis cells displayed a heterogeneous co-expression of cytokeratin and vimentin. In double immunohistochemistry, differences in distribution of keratin and vimentin intermediate filaments with predominance of cytokeratins in the apical cytoplasmic regions and of vimentin filaments in the basal portions of the cells were found. Cytokeratin expression preceded the appearance of vimentin: cytokeratin was already detectable in 10-week-old embryos, while weak vimentin immunoreactivity was first seen in 12-week-old embryos and became conspicuous in testes around the perinatal period. In testes of children up to 2 years of age the cytoplasmic distribution of cytokeratin and vimentin was more homogeneous. Predominance of the basal cell portions for vimentin and the apical regions for cytokeratin staining were less pronounced than in adult testes. In the proximal and distal parts of the epididymis a different intermediate filament expression pattern was found with a clear predominance of cytokeratin near the rete.