Immunocytochemical demonstration of vimentin in astrocytes and ependymal cells of developing and adult mouse nervous system

Monoclonal antibody to neural cell surface protein: identification of a glycoprotein family of restricted cellular localization

A monoclonal antibody, designated anti-NSP-4 (anti-Neural cell Surface Protein-4), was obtained from a hybridoma generated by fusing rat myeloma cells with splenocytes of a rat immunized with membranes from the cerebella of weaver mutant mice. This antibody reacted with several high-molecular weight polypeptides in extracts prepared from the newborn and adult CNS of wild-type mice. The main NSP-4-reactive bands from neonatal cerebellum and spinal cord migrated with apparent molecular weights of 220,000 and 140,000. Major bands of 160,000 and of 175,000, 160,000 and 140,000 molecular weight were revealed in the adult cerebellum and spinal cord, respectively. Reaction of the antibodies with concanavalin A-binding proteins demonstrated the glycoprotein nature of the antigen. Cell types expressing NSP-4 antigen were determined using indirect immunofluorescence on monolayer cultures of early postnatal mouse cerebellar and dorsal root ganglion cells and on sections of developing and adult mouse cerebellum. In cerebellar cultures, the antibody reacted with the surface membrane of a subpopulation of astrocytes and of a small subset of neurones. In dorsal root ganglion cultures, anti-NSP-4 antibodies were highly specific for a subclass of small neurones. Staining for NSP-4 in sections of adult cerebellum was confined to the granular layer where the antibody seemed to label astroglia. In the developing cerebellum, NSP-4 staining outlined cell bodies of neuroblasts and migrating granule cells in the external granular layer. Post-migratory granule cells and Purkinje cells were negative. As in the adult, the labeled structures in the internal granular layer were probably astrocytes. Our results on the in vivo and in vitro localization of NSP-4 show its expression by subclasses of neurones and astrocytes in the cerebellum and by a subclass of neurones in cultures from the peripheral nervous system. The developmentally-regulated changes in the molecular weight forms of the NSP-4 antigen together with the shift in its cellular localization during cerebellar ontogeny suggest a functional significance for this antigen in developmental processes.

Expression of the major neurofilament subunit in chicken erythrocytes

The 70,000-dalton core polypeptide of neurofilaments, thought to exist only in neurons, has been detected in chicken erythrocytes, where it coexists with vimentin and synemin as a component of the intermediate filament network. It is present in the circulating erythroid cells of embryos and young chickens but is nearly absent from the erythroid cells of adults. These findings are inconsistent with current models of intermediate filament expression, but provide another example of unexpected similarities between the nervous and hemopoietic systems.

Temporal relationship between the appearance of vimentin and neural tube development

Intermediate filaments of the vimentin type that were initially identified within mesodermally derived cells have recently been demonstrated within several immature cell types derived from neuroectoderm, such as astroblasts and early stage neuroblasts. The objective of the present study was to determine the earliest developmental stage at which vimentin could be detected in the mouse neural tube. Vimentin was not detectable in the newly formed neural tube in E8 embryos. In the E9 neural tube the first positively labeled processes were observed in the ventrolateral region of the cervical neural tube with the processes having the distribution and appearance of those of radial glial cells. Between E9 and E10 there was a significant increase in the vimentin content of the neural tube as labeled filamentous bundles were observed throughout the ventricular cell layer and in the forming mantle layer. The distribution of labeled filaments in the E11 neural tube was similar to that of the E10 tissue although staining intensity was greater in the mantle layer in the E11 tissue. This work identifies the temporal relationship between the appearance of vimentin and neural tube development.

Antibodies to intermediate filament proteins in the immunohistochemical identification of human tumours: an overview

Intermediate-sized filament proteins (IFP) are tissue specific in that antibodies to keratin, vimentin, desmin, glial fibrillary acidic protein (GFAP) and the neurofilament proteins can distinguish between cells of epithelial and mesenchymal origin as well as of myogenic and neural origin respectively. Malignant cells retain their tissue-specific IFP, which makes it possible to use these antibodies in tumour diagnosis. Carcinomas are exclusively detected by antibodies to keratin. Monoclonal antibodies to keratin have allowed the differentiation between subgroups of epithelial tumours until now between adenocarcinomas and squamous cell carcinomas. Lymphomas, melanomas and several soft tissue tumours are distinctly recognized by antibodies to vimentin. On the other hand, rhabdomyosarcomas and leiomyosarcomas are positive for desmin, while astrocytomas give a strong reaction with GFAP antibodies. Thus, antibodies to IFP are useful tools for differential diagnosis in surgical pathology.

Molecular interactions in intermediate-sized filaments revealed by chemical cross-linking. Heteropolymers of vimentin and glial filament protein in cultured human glioma cells

Certain glia cells, notably astrocytes and tumor cells derived therefrom, express simultaneously two types of proteins of intermediate-sized filaments, vimentin and glia filament protein (GFP). We have used an established human glioma (astrocytoma) cell culture line (U 333 CG/343 MG) in which both proteins are seen in partly overlapping fibrillar structures by immunofluorescence microscopy, to examine the possible existence of heteropolymer filaments of these two proteins by using reversible oxidative cross-linking facilitated by the 1,10-phenanthroline-cupric ion complex. Dimeric cross-link products are characterized by one-dimensional and two-dimensional gel electrophoresis under non-reducing and reducing conditions as well as by peptide mapping. The relatively large proportions of heterodimers of vimentin and GFP obtained in cytoskeletal filaments cross-linked in this way, demonstrate the frequency of heteropolymer filaments in this cell as well as the frequency of face-to-face 'pairs' of GFP and vimentin in such filaments. Together with our related observations on heteropolymer filaments between vimentin and desmin in some smooth muscle cells [Quinlan, R. A. and Franke, W. W. (1982) Proc. Natl Acad. Sci. USA, 79, 3452-3456], we discuss this as evidence for common principles of molecular arrangements of vimentin, GFP and desmin, at least in the cysteine-containing surface domains. The results are also discussed in relation to cytoskeletal changes during glial differentiation.

Coexistence of neurofilaments and vimentin in a neurone of adult mouse retina

Different classes of intermediate filaments are restricted to particular cell types. For example, neurofilaments are found only in neurones, whereas filaments that contain the protein vimentin, which were found in some cells of mesenchymal origin and some forms of glia, are thought to be absent from mature neurones, and present only transiently in early embryonic neurones. However, evidence is presented here of an exception to that rule in the outer plexiform layer of the mouse retina. Double-labelling with antibodies to neurofilaments and vimentin showed that both types of intermediate filaments coexisted in the axonless horizontal cell of that retinal layer, recalling the previous notion that these cells are glial or intermediate between neuronal and glial (reviewed in ref. 10).

A qualitative and quantitative ultrastructural study of glial cells in the developing visual cortex of the rat

(i) This paper provides new information on the time course and fine structural features of glial cell differentiation, on the relative frequencies of glioblasts, astroblasts, astrocytes, oligodendrocytes and microglial cells, and on neuron: glia ratios in visual cortex of the rat between birth and maturity. The analyses were done on montages of electron micrographs of 75 pm wide strips extending the full depth of the cortex from animals 12 h and 4, 6, 8, 10, 12, 14, 20, 24, 90 and 180 days old (six montages from two or three animals at each age). (ii) At birth, and up to 4 days, most non-neuronal cells are poorly differentiated, irregularly shaped cells with dark nuclei (glioblasts). A few at this stage and progressively larger numbers over the next few days, can be recognized asastroblastsby the presence of a distinctive form of granular reticulum (distended cisterns with a moderately electron dense content), and some also by their position in contact with the subpial or perivascular basal laminae. Astroblasts enlarge, develop processes and transform into immature astrocytes: their nuclei become paler, the granular reticulum is no longer distended, and glial filaments begin to accumulate.Mature astrocyteswith pale nuclei, filaments and a low concentration of perikaryal organelles in a pale cytoplasmic matrix predominate at 24 days, and at 3-6 months 51 % of all glial cells are astrocytes. (iii) Concentrations of glioblasts (at 0 and 4 days) and subsequently of cells of the astrocytic lineage are apparent in the most superficial and in the deepest cortical layers, and an additional small peak is seen at the level of layer IV in the adult animals. The superficial concentration is probably associated with the subpial glia limitans and the layer IV concentration with the high density of synapses in this region; several probable explanations are considered for the concentration in layer VI. (iv) Processes ofradial glial cellsare apparent from birth to day 8 but not thereafter. No evidence was found for transformation of radial glia into astrocytes. A peak in phagocytic activity by immature microglial cells at days 6-8 suggests the possibility of loss of radial glial processes by degeneration rather than transformation. (v)Oligodendroblasts, intermediate in morphology between glioblasts and light oligodendrocytes, appear suddenly in the deep cortex and subcortical white matter at day 6 and are rapidly replaced bylight oligodendrocytes. These are large, organelle-rich cells with characteristically distended Golgi saccules, and are the only oligodendrocytes present during early myelination, which begins at day 10. Early in the 3rd postnatal week some light oligodendrocytes are replaced bymedium oligodendrocytes, which are smaller and darker, with abundant orderly stacks of granular reticulum.Dark oligodendrocytesare first apparent at the end of the 3rd week, account for about one-third of all oligodendrocytes at day 24, predominate at day 40 and constitute 90 % of all oligodendrocytes at 3 and 6 months, at which time oligodendrocytes comprise 39% of all cortical glial cells. We suggest that the progression from light to medium oligodendrocytes does not simply represent a diminution in the overall level of synthetic activity but that different components of the myelin sheath are being synthesized at the two stages. (vi)Microgliaare present from birth but are seen in significant numbers at days 6—10 and thereafter. Some are relatively mature in appearance, even in the youngest animals, and almost all are similar to the resting microglia of adult brain by day 16. At 3-6 months, 8 % of all cortical glial cells are identified as microglia and these cells are fairly evenly distributed throughout the cortical depth but are surprisingly and consistently poorly represented in layer VI. From day 6 to the end of the 2nd postnatal week, cells with poorly differentiated cytoplasm (many free polyribosomes), but containing phagocytosed products of cell degeneration, are identified asimmature microglia. However, it is possible that such cells do not mature into classical resting microglia but that they represent a different cell type. (vii) Theneuron: glia ratiois 4.54 at birth, rises to 5.09 at 4 days, and falls to approximately 2.5 at days 12-24. At 3-6 months the ratio is 2.13.

Astrocyte cell lineage. II. Mouse fibrous astrocytes and reactive astrocytes in cultures have vimentin- and GFP-containing intermediate filaments

When cells from mouse neopallium are grown in colony cultures for 10-12 days, small cells with many processes, resembling normal fibrous astrocytes, form on top of the astrocyte precursor cells independently of the presence of dBcAMP in the culture medium. These cells are distinctly different from the much larger, previously described reactive astrocytes which also form in colony cultures and whose maturation is greatly enhanced by the presence of dBcAMP in the culture medium. Immunofluorescence studies showed that both vimentin-containing and glial filament protein (GFP)-containing intermediate filaments (IF) are present in the small normal fibrous astrocytes as well as in the larger reactive astrocytes. The vimentin-containing IF are assembled first in astrocyte precursor cells, whereas GFP-containing IF are assembled later toward the final stages of astrocyte differentiation both in vivo and in vitro. Thus in respect to the expression of the two types of IF, astrocyte differentiation in vitro closely resembles that in vivo. Parallel studies by electron microscopy showed that the vimentin-positive but GFP-negative astrocyte precursor cells contain single IF or small groups of IF, whereas in the more differentiated normal fibrous astrocytes and reactive astrocytes which are also GFP-positive, additional IF arranged in large bundles are present.

Early divergence and changing proportions of neuronal and glial precursor cells in the primate cerebral ventricular zone

Immunocytochemical staining with antisera directed against glial fibrillary acidic protein (GFA) was used to examine the cellular composition of the proliferative ventricular zone (VZ) in the occipital lobe of rhesus monkey fetuses during the first half of their 165-day gestational period. Electron microscopic analysis revealed a small number of GFA-positive cells in specimens of embryonic (E) ages E39 and E40. By E47 about 28% of the cells in the VZ were immunoreactive. This percentage increased to 37% at E61 and reached 60% by E80. The fraction of GFA-positive mitotic figures followed the same general tendency with 34, 47, and 80% being labeled at E47, E61, and E80, respectively. The present results reveal the existence of two basic classes of cells, GFA positive and GFA negative, indicating that in the primate brain, glial and neuronal precursor cells may coexist in the ventricular zone at embryonic ages when few, if any, neurons have become postmitotic.

The role of cytoskeletal and cytocontractile elements in pathologic processes

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Intermediate filaments in malignant melanomas. Identification and use as marker in surgical pathology

Intermediate-sized filaments have been studied in human malignant melanomas and in normal melanocytes by immunofluorescence microscopy with antibodies directed against keratin, vimentin, desmin, neurofilament protein, and glial filament protein. Both human melanotic and amelanotic tumor cells and tumor metastases as well as normal melanocytes in human skin and in the rat eye contain exclusively intermediate filaments of the vimentin type. No reaction was seen with antibodies to keratin, desmin, neurofilaments, or glial filaments. These latter four antisera, however, gave strong reactions in epidermis and other epithelial tissues, muscle, or neural tissues, respectively. The results favor a mesenchymal character of melanocytes, although a neuroectodermal origin in an early developmental stage is possible. The finding that melanomas contain exclusively vimentin intermediate filaments may prove useful in differential diagnosis of melanomas from other tumor types.

Detection of desmin-containing intermediate filaments in cultured muscle and nonmuscle cells by immunoelectron microscopy

Antibodies raised against chicken gizzard smooth muscle desmin were shown to be specific by immunofluorescence cytochemistry and immunoautoradiography after two-dimensional polyacrylamide gel electrophoresis. Embryonic chick heart cell cultures (permeabilized with Triton X-100) and enucleated adult chicken erythrocyte ghosts (Granger, B. L., E. A. Rapasky, and E. Lazarides, 1982, J. Cell Biol. 92:299-312) were then used for immunoelectronmicroscopic localization of desmin. As expected, all intermediate filaments (IF) of the cardiac myocytes were labeled heavily and uniformly with the desmin antibodies. No periodicity or helicity was detectable along the labeled IF. Of interest was the intermittent but clear labeling of the IF of the nonmuscle, fibroblastic cells in the identical cultures. These antibodies did not bind vimentin from embryonic chick heart homogenates; furthermore, they did not label IF of avian erythrocytes known to contain vimentin but not desmin. We conclude that IF of cardiac fibroblastic cells contain low, but significant, concentrations of desmin and that this protein probably forms a copolymer with vimentin in these cells.

Proteins of intermediate filaments. An immunohistochemical and biochemical approach to the classification of soft tissue tumors

The intermediate filament cytoskeleton of various types of human soft tissue tumors was analyzed by immunofluorescence microscopy with the use of specific antibodies against cytokeratins, vimentin, and desmin, as well as by one- and two-dimensional gel electrophoresis of high-salt buffer- and detergent-resistant cytoskeletal preparations. All leiomyomas as well as a leiomyosarcoma contained desmin. Leiomyomas of both gastrointestinal and uterine derivation and the retroperitoneal leiomyosarcoma showed strong reaction for desmin in the smooth muscle cells, but the latter two exhibited also vimentin staining. In embryonal rhabdomyosarcomas, desmin prevailed in the large, apparently well-differentiated rhabdomyoblasts; whereas the smaller, less differentiated tumor cells preferentially contained vimentin. Cells of malignant fibrous histiocytomas were characterized by their content of vimentin as the only intermediate filament protein present. In alveolar soft part sarcoma, a rare tumor of hitherto unknown histogenesis, vimentin and desmin co-existed within the same tumor cells, indicating, together with chemical determinations, the myogenic derivation of this neoplasm. The results show that immunologic and biochemical analysis of proteins associated with the intermediate filament cytoskeleton is a useful adjunct in the diagnosis of diverse neoplasms, particularly those with equivocal histologic features, and thus aids in the histogenetic classification of soft tissue tumors.

Parietal and visceral endoderm differ in their expression of intermediate filaments

Two layers of extra-embryonic endoderm, viz. the parietal endoderm (PE) and the visceral endoderm (VE), arise in the mouse embryo shortly after implantation. Both cell populations apparently originate from the primitive endoderm of the blastocyst. While the endoderm differentiation has been studied both in the embryo and in the embryonal carcinoma model system, the investigation has been hampered by the paucity of unequivocal markers of differentiation, especially in the case of the PE. Here we show that the PE and VE of mouse conceptuses differ in their expression of intermediate filaments: while both cell types contain cytokeratin, expression of vimentin was only revealed in the cells of the PE. The association between the differentiation of PE and the appearance of vimentin filaments is discussed.

Malignant melanomas contain only the vimentin type of intermediate filaments

Six malignant melanomas have been examined for the type of intermediate filament they contain. All six cases showed positive staining of intermediate filaments with antibodies to vimentin, with cells containing large numbers of melanosomes being stained less strongly in general. The tumor cells did not react with antibodies to keratin, desmin, neurofilaments or glial fibrillary acidic protein. Thus typing of intermediate filaments can distinguish melanoma from undifferentiated carcinoma, but not from lymphoma or sarcoma. Since melanocytes are known to be vimentin positive, and since most of the samples we studied were from metastases, these results are a further indication that the intermediate filament type typical of the parental cell is retained in the metastases, as well as in the primaries of solid tumours. The implications of vimentin positivity for the histiogenesis of the melanocyte are also discussed.

Identification and immunocytochemical localization of a human adult brain-specific antigen (HABSA)

A new protein with a molecular weight of 669,000, identified in brain extracts from 4 to 69 years old subjects has been isolated and immunochemically characterized. The antigen is found in human adult brain but not in the brains of human fetuses and newborn infants or in the brains of several other species tested. Immunocytochemically, using the PAP method, the antigen is localized at the surface of some nerve cells and on astrocytes and oligodendrocytes of the cerebral cortex, corpus striatum, pons and medulla. The Golgi epithelial cells with Bergmann's fibers, and the velate and ordinary astrocytes in the cerebellum show immunoreactivity as well.

Intermediate filaments and their interaction with membranes. The desmosome-cytokeratin filament complex and epithelial differentiation

Intermediate-sized filaments represent a class of morphologically similar but biochemically and immunologically distinguishable cytoplasmic protein polymer structures. Five major filament types have been identified (cytokeratin, vimentin, desmin, neurofilament protein, glia filament protein) and antibodies to these proteins have been used for distinguishing different cell types and tumors derived therefrom. Epithelial and carcinoma cells are characterized by the presence of cytokeratin filaments and desmosomal elements identified by antibodies to certain high molecular weight proteins of desmosomal plaques. However, the specific pattern of cytokeratin polypeptides is different in different epithelia. The potential value of cell type identification by immunological reactions with antibodies to cytoskeletal proteins in tumor diagnosis is discussed.

Complex cytokeratin polypeptide patterns observed in certain human carcinomas

Human epithelial cells contain, intermediate-sized filaments formed by polypeptides related to epidermal alpha-keratin ("cytokeratins") which are expressed in different combinations in different epithelia. Using cytoskeletal proteins from human biopsies and autopsies we have examined, by two-dimensional gel electrophoresis and immunoblotting experiments, the cytokeratin polypeptide patterns of diverse primary and metastatic carcinomas and have compared them with those of corresponding normal epithelial tissues and cultured cells. Five groups of carcinoma cytokeratin patterns can be discriminated. (1) Cytokeratins typical of simple epithelia (polypeptides Nos. 7, 8, 18, 19) are expressed, in various combinations, by many adenocarcinomas, for example those of gastrointestinal tract. (2) Cytokeratins typical of stratified epithelia (Nos. 1, 5, 6, 10, 11, 14-17) are found, in various combinations, in squamous cell carcinomas of skin and tongue. (3) Complex patterns showing polypeptides Nos. 7, 8, 18, 19, and one basic component (No. 5 or 6) are detected in certain carcinomas of the respiratory tract and the breast. (4) Complex patterns containing cytokeratins widespread in stratified epithelia (Nos. 4-6, 14-17) as well as components Nos. 8 and 19 occur in diverse squamous cell carcinomas derived from non-cornified stratified epithelia, with or without additional small amounts of cytokeratin No. 18. (5) Patterns of unusually high complexity can be found in some rare tumors as is shown for a cloacogenic carcinoma. No significant qualitative changes of expression of cytokeratins were found when primary tumors and metastases were compared. When compared with cytokeratin patterns of normal epithelia, carcinomas of the first type usually display a high degree of relatedness to the tissue of origin. Other carcinomas do not express some of the cytokeratins present in the tissue of their origin and, vice versa, certain components which are minor or apparently absent in normal tissue are major cytokeratins in the corresponding tumor. These differences may be explained by cell type selection during carcinogenesis, but changes of expression during tumor development cannot be categorically excluded. The possibility of cell type heterogeneity within a given tumor is also discussed. Similarly complex patterns of cytokeratin polypeptides have been noted in certain cultured human carcinoma cell lines (e.g., A-431, RPMI 2650, Detroit 562, A-549) and can also be observed in cell clones. The possible value of analyses of cytokeratin patterns, by gel electrophoresis or specific monoclonal antibodies, in distinguishing different carcinomas by non-morphologic criteria is discussed.

Formation of cytoskeletal elements during mouse embryogenesis. III. Primary mesenchymal cells and the first appearance of vimentin filaments

The cytoskeletal composition of the 'primitive streak' stage of mouse embryos, i.e. at late day 8 ('day 8.5') of gestation, has been examined by electron microscopy, using thin sections of fixed and embedded embryos, and by immunofluorescence microscopy, using cryostat sections of frozen embryos. At this stage primary mesenchymal cells are observed in the posterior part of the embryo which seem to migrate toward the anterior region. For most of the embryo, these mesenchymal cells are separated from the embryonic ectoderm by a continuous basal lamina. Frequently mesenchymal cells form cytoplasmic projections many of which make contact with this basal lamina, with surfaces of proximal endoderm cells, or with other mesenchymal cells. Primary mesenchymal cells contain sparse individual intermediate-sized filaments (IF), but closely packed IF bundles as they occur as tonofibrils in both embryonic epithelia, ectoderm and proximal endoderm, have not been found. Mesenchymal cells also can form junctions of the fascia adhaerens-type but appear to be devoid of desmosomes. Antibodies to cytokeratins reveal strong fibrillar fluorescence in cells of the proximal endoderm and weak, predominantly subapical staining in embryonic ectoderm. Correspondingly, antibodies to desmoplakins, the major proteins of the desmosomal plaque, show punctate fluorescence in both embryonic epithelia. These epithelial cells are not significantly stained with antibodies to other IF proteins such as vimentin and desmin. However, antibodies to vimentin show positive fluorescence, often in fibrillar tangles, in primary mesenchymal cells which in turn are negative with cytokeratin and desmin antibodies. This first detection of expression of vimentin in embryogenesis has been confirmed by two-dimensional gel electrophoresis of cytoskeletal proteins from 35S-methionine-labelled embryos. The observations indicate that during embryogenesis synthesis of vimentin occurs, for the first time, in the primitive streak stage and is restricted to the primary mesenchymal cells. Concomitantly, these cells cease to produce cytokeratins and desmoplakin. Possible mechanisms effective in this rapid change from epithelial to mesenchymal character, i.e. from cytokeratin IF to vimentin IF, are discussed.

Vimentin in the central nervous system. A study of the mesenchymal-type intermediate filament-protein in Wallerian degeneration and in postnatal rat development by two-dimensional gel electrophoresis

Intermediate filament proteins were identified by two-dimensional gel electrophoresis in urea extracts of rat optic nerves undergoing Wallerian degeneration and in cytoskeletal preparations of rat brain and spinal cord during postnatal development. The glial fibrillary acidic (GFA) protein and vimentin were the major optic nerve proteins following Wallerian degeneration. Vimentin was a major cytoskeletal component of newborn central nervous system (CNS) and then progressively decreased until it became barely identifiable in mature brain and spinal cord. The decrease of vimentin occurred concomitantly with an increase in GFA protein. A protein with the apparent molecular weight of 61,000 and isoelectric point of 5.6 was identified in both cytoskeletal preparations of brain and spinal cord, and in urea extracts of normal optic nerves. The protein disappeared together with the polypeptides forming the neurofilament triplet in degenerated optic nerves.

In vitro differentiation of mouse teratocarcinoma cells monitored by intermediate filament expression

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.

Various sympathetic derived human tumors differ in neurofilament expression. Use in diagnosis of neuroblastoma, ganglioneuroblastoma and pheochromocytoma

We have extended our analysis of human tumors using antibodies specific for each of the five types of intermediate filaments to neuroblastoma, ganglioneuroblastoma, pheochromocytoma, ependymoblastoma, and alveolar soft part sarcoma. Tumor cells in the three cases of neuroblastoma, as well as in the single case of alveolar soft part sarcoma, did not react positively with sera directed against any of the five intermediate filament types. We suppose, therefore, that neuroblastoma at least may be derived from a cell type - possibly present in peripheral neurones - which in vivo has very few or no intermediate filaments. In ganglioneuroblastoma and in pheochromocytoma the tumor cells were positive when tested with antibodies directed against neurofilaments and negative with those directed against other intermediate filament types. The ependymoblastoma was positive when tested with antibodies directed against glial fibrillary acidic protein (GFA) and negative when tested with antibodies against other intermediate filament types. Use of antibodies to the different intermediate filament types appears to be a valid way in which to classify tumors, and so far the data presented here and elsewhere support the hypothesis that tumor cells retain the intermediate filament type typical of their cell of origin. Wider use of these sera would seem particularly useful in cases such as neuroblastoma, rhabdomyosarcoma or lymphoma where diagnosis is currently difficult using conventional histological stains.

Cell type specificity of a neural cell surface antigen recognized by the monoclonal antibody A2B5

The monoclonal antibody A2B5 reacts with the surface membrane of most neurons in monolayer cultures of cerebellum, retina, spinal cord, and dorsal root ganglion of embryonic and early postnatal C57Bl/6 J mice maintained in vitro for culture periods of 2 to 10 days. A small percentage of astroglial cells also expresses A2B5 antigen in murine, chicken and rabbit cerebellum, in chicken retina, and in murine spinal cord and dorsal root ganglion. Less mature astroglial cells are strained for A2B5 antigen to a greater extent than the more mature astrocytes. Astrocytes from rat cerebellum and mouse retina were not found to express A2B5 antigen under the present culture conditons. Some of the less mature oligodendrocytes recognized by 04 antibodies express A2B5 antigen, while the more mature 01 antigen- and galactocerebroside-positive oligodendrocytes were not found to be A2B5 antigen-positive. Fibroblasts or fibroblast-like cells do not express detectable levels of A2B5 antigen. After fixation of the cells with paraformaldehyde and ethanol, all cell types present in culture are labeled by the A2B5 antibody intracellularly.

Electron-microscopic localization of A2B5 cell surface antigen in monolayer cultures of murine cerebellum and retina

Immuno-electron microscopy was performed on live, cultured, early postnatal cerebellar and retinal cells of the mouse to identify A2B5 antigen-bearing elements. In cerebellar cultures, granule cells, some immature oligodendroglia, and astroblasts express A2B5 antigen on their cell surfaces. The typical features of astroblasts include large cisternae of the endoplasmic reticulum and a mixed population of intermediate-sized filaments and microtubules. Immature oligodendroglia cells express the antigen on their cell bodies and on processes filled with cytoplasm. Cytoplasm-free membranous whorls, however, are devoid of A2B5 antigen, but not of 0 or NS-1 antigens. In retinal cultures, A2B5 antigen is observed on differentiating neurons with the exception of photoreceptor cells as identified by ribbon synapses.

Heteropolymer filaments of vimentin and desmin in vascular smooth muscle tissue and cultured baby hamster kidney cells demonstrated by chemical crosslinking

Certain smooth muscle cells of blood vessel walls as well as cultured baby hamster kidney cells contain simultaneously two different intermediate-sized filament (IF) proteins, desmin and vimentin. We have examined the question of the occurrence of both proteins in the same IF by chemically crosslinking the single cysteine group present in each of them. Oxidative crosslinking of filaments present in cytoskeletal preparations with cupric ion complexes of 1,10-phenanthroline resulted in formation of three types of dimers: vimentin-vimentin, desmin-desmin, and vimentin-desmin. These dimers were separated by NaDodSO4/polyacrylamide gel electrophoresis and characterized by binding of specific antibodies, by one- and two-dimensional gel electrophoresis of monomers obtained after cleavage of the disulfide bond by thiol agents, and by mapping of radioiodinated tryptic peptides. The demonstration of heterodimers of vimentin and desmin in vascular smooth muscle tissue of cow and chicken and in baby hamster kidney cells shows that the two proteins can be integrated in the same IF and can be nearest neighbors, oriented with their cysteine residues in a mirror-image symmetry. The possible existence of heteropolymer IF in other cell types is discussed.

An ultrastructural and immunocytochemical study of astrocytic differentiation in vitro: changes in the composition and distribution of the cellular cytoskeleton

Astroglia in cultures of dissociated neonatal rat optic nerves were studied by light microscopy, immunocytochemistry and electron microscopy to determine whether intermediate filaments play a role in defining the multipolar morphology of the mature astrocyte. Immature, polygonal astroblasts contained few glial filaments, in spite of exhibiting positive staining with antiserum against glial fibrillary acidic (GFA) protein. Microtubules were the most prominent cytoskeletal component at early stages of cytodifferentiation, but these were progressively reduced in number at later intervals and were gradually replaced by intermediate filaments. These observations suggest that microtubules are involved in the initial establishment of cytoplasmic asymmetry and process development. Subsequently, glial filaments may play a role in maintaining and stabilizing the overall geometry of the mature astrocyte.

Cell type-specificity of epidermal growth factor (EGF) binding in primary cultures of early postnatal mouse cerebellum

Binding of 125I-labeled epidermal growth factor (EGF) to cells of cultured early postnatal mouse cerebellar cells was investigated by autoradiography in conjunction with cell type-specific immunolabeling of neurons, astrocytes and oligodendrocytes. By use of tetanus toxin for recognition of neurons and glial fibrillary acidic (GFA) protein and 04 antigen as markers for astrocytes and oligodendrocytes, respectively, it could be shown that oligodendrocytes do not express receptors for EGF within the limits of sensitivity of the autoradiographic method, and that less than 1% of all small neurons (mostly granule cells) and 50-90% of all GFA protein-sensitive astrocytes show detectable levels of EGF binding.

Cultivation of immature astrocytes of mouse cerebellum in a serum-free, hormonally defined medium. Appearance of the mature astrocyte phenotype after addition of serum

A hormonally defined culture medium is described which supports survival and proliferation of astroglia from primary cultures of early postnatal mouse cerebellum. This medium consists of bovine serum albumin, insulin, transferrin, selenium, hyaluronic acid, protease inhibitor aprotinin, and epidermal growth factor. Trypsin-dissociated single cerebellar cell suspensions are plated in this medium on poly-l-coated glass coverslips and maintained for two weeks before subcultivation. After subcultivation into defined medium more than 99% of all cells are vimentin-positive and fibronectin- and almost completely glial fibrillary acid (GFA) protein-negative, indicating that these cells are less mature astrocytes. After replacement of defined medium by culture medium containing 10% horse serum, expression of GFA protein is detectable in addition to vimentin by indirect immunofluorescence.

Cultivation of mouse cerebellar cells in serum free, hormonally defined media: survival of neurons

A hormonally defined medium is described which facilitates the survival of small neurons in primary cultures of mouse cerebellum. The defined medium consists of bovine serum albumin, insulin, transferrin, selenium, thyroxine, and the protease inhibitor aprotinin. About 95% of all cells were identified as neurons using tetanus toxin as a marker in an immunocytochemical assay. They survive for more than 4 weeks, showing a tendency to grow in cell clusters with a dense network of processes. The remaining cells (approximately 5%) were identified as astrocytes by their expression of vimentin and GFA protein and the lack of expression of fibronectin.

A monoclonal antibody specific for the 200 K polypeptide of the neurofilament triplet

A mouse monoclonal antibody, designated NF1, was obtained from a cloned hybridoma isolated from a fusion of mouse myeloma Sp2 cells with spleen cells from a BALB/c mouse immunized with a crude neurofilament preparation from porcine spinal cord. NF1 is an IgG1 and recognizes, in immune blotting procedures, only the 200 K neurofilament triplet component. Its neurofilament-specific nature is further revealed by immunofluorescence microscopy studies on frozen tissue sections and various cultured cells. Immunoelectron microscopy studies on cytoskeletons of cultured neurones emphasize the discontinuous display along each neurofilament previously observed with polyclonal antibodies specific for the 200 K component after appropriate but rather cumbersome cross-absorption steps. Use of NF1 on various neuronal cells strongly supports the previous proposal of the existence of certain subpopulations of neurofilament-free neurones and the observation that certain neuronal arrangements, (e.g., those in dendrites of pyramidal cells of the hippocampus), although rich in neurofilaments, probably lack the normal 200 K triplet component. Since NF1 shows a broad cross-species reactivity and is able to react on formaldehyde-fixed tissue, it should be a useful reagent to study differential neurofilament expression and organization in embryonic, adult and pathological tissues.

Formation of cytoskeletal elements during mouse embryogenesis. II. Epithelial differentiation and intermediate-sized filaments in early postimplantation embryos

Following our study on the expression of cytokeratin filaments in preimplantation mouse embryos [30], we have examined the organization of cytoskeletal elements in early postimplantation embryos up to day 8 of gestation, employing electron microscopy, immunofluorescence microscopy an two-dimensional gel electrophoresis of cytoskeletal proteins labelled by incorporation of 35S-nethionine. The characteristic epithelia formed by the embryonic ectoderm and proximal (visceral) endoderm present well-developed junctional complexes and various differentiated membrane structures. Several apical differentiations of the proximal endodermal cells, such as brush border-like microvilli, the endocytotic labyrinthum, and the supranuclear vacuoles resemble the organization of epithelial cells of the ileum of neonatal mammals. Both embryonic epithelia show typical desmosomes and attached intermediate sized filaments of the cytokeratin type. Other types of intermediate-sized filaments, such as vimentin and desmin filaments, have not been detected in any of the cells of embryos of days 6 and 7, but filaments of the vimentin type can be seen, by immunofluorescence microscopy, late in day 8 in certain cells located in the forming mesoderm. Gel electrophoresis has further revealed that the major cytoskeletal proteins synthesized during days 6-8 in both extraembryonic and embryonic tissue are similar to those characteristic of preimplantation blastocysts and include a major polypeptide corresponding to cytokeratin A described in some internal organs of adult rodents. By the same techniques, synthesis of another cytoskeletal proteins vimentin, has first been found late in day 8. It is concluded that early postimplantation embryonic development, up to mesoderm formation, is characterized by the exclusive presence, in both embryonic ectoderm and proximal endoderm, of differentiated epithelial cells containing desmosome-cytokeratin filament complexes and that other types of intermediate-sized filaments are not yet expressed.

Developmental expression of cell type-specific markers in mouse cerebellar cells in vitro

The expression of several cell type-specific markers was studied by indirect immunofluorescence in discontinuous BSA gradient fractionated and unfractionated mouse cerebellar cells cultured for 3 days in vitro from embryonic day 13 through postnatal day 9. Cell surface antigen NS-4 and tetanus toxin receptors are present at all ages studied. Thy-1 first detected on neurons with large cell bodies (Purkinje and/or Golgi Type II.neurons) onpostnatal day 3, but absent from all neurons with small cell bodies (granule, basket, and stellate cells). At all ages Thy-1 antigen is absent from astro- and oligodendroglia, and fibroblasts or fibroblast-like cells. Fibroblast-like cells express fibronectin at all ages studied. Astroglia expressing glial fibrillary acidic (GFA) protein are first detectable in cultures from 16-day-old embryos. Their number increases at later ages. At all ages studied fluorescein conjugated Ricinus communis agglutinin 120 brightly labels the cell surfaces of fibroblastic cells and large neurons, less brightly those of astrocytes, bu not those of small neurons. Oligodendroglia become detectable in cerebellar cultures from 16- and 17-day-old embryos maintained in vitro for 3 days using antibodies to 04 antigen and bovine corpus callosum, respectively. At embryonic ages BSA step gradient procedures do not result in enrichment of particular cell types as recognized by the available markers. From birth onward, however, enrichment of cell populations was obtained corresponding to the ones characterized at postnatal day 6 as described in the companion paper (Schnitzer and Schachner 1981b).

Neuronal and glial cells in the superficial layers of early postnatal mouse neocortex: immunofluorescence observations

Sections of immature (postnatal day 5) mouse cerebral cortex was examined for several cell-type specific immunological markers. Glial fibrillary acidic (GFA) protein or vimentin were detected in astrocytic cell processes and--more rarely--cell bodies located in the superficial layers, but not within putative Cajal-Retzius cells (CRs). These cells did, however, react with cholera toxin, tetanus toxin and NS-4 antibodies. In agreement with previous ultrastructural observations, we conclude that CRs are neurons, or at least cells which display the basic characteristics of neurons.

Immuno-electron-microscopic identification of O-antigen-bearing oligodendroglial cells in vitro

Monoclonal antibodies to cell-surface antigens of oligodendrocytes (Sommer and Schachner 1980; Schachner et al. 1980) were used to identify this cell type by immuno-electron microscopy in monolayer cultures of fetal and early postnatal mouse cerebellum. The ultrastructural features of antigen-positive cells confirm that they are immature and mature oligodendrocytes, but not neurons, astrocytes or fibroblasts or fibroblast-like cells. Type I oligodendrocytes are the immature ones with a relatively large amount of moderately electron-lucent cytoplasm, clusters of ribosomes and complex networks of rough endoplasmic reticulum. Large numbers of mitochondria and microtubules, but not intermediate-sized filaments are seen in these cells. They comprise more than 90% of all 0-antigen-positive cells. Type II cells comprise only approximately 5% of all 0-antigen-positive cells. They are characterized by a limited amount of electron-dense cytoplasm, which appears more compact and granular than in type I cells. The rough endoplasmic reticulum is distributed evenly throughout the cytoplasm. Microtubules and mitochondria are present, but more difficult to distinguish due to the compactness of the cytoplasm. Type II cells display the more mature ultrastructural features of oligodendrocytes.

Recognition of Bergmann glial and ependymal cells in the mouse nervous system by monoclonal antibody

A monoclonal antibody designated anti-Cl was obtained from a hybridoma clone isolated from a fusion of NS1 myeloma with spleen cells from BALB/c mice injected with homogenate of white matter from bovine corpus callosum. In the adult mouse neuroectoderm, C1 antigen is detectable by indirect immunohistology in the processes of Bergmann glial cells (also called Golgi epithelial cells) in the cerebellum and of Müller cells in the retina, whereas other astrocytes that express glial fibrillary acidic protein in these brain areas are negative for C1. In addition, C1 antigen is expressed in most, if not all, ependymal cells and in large blood vessels, but not capillaries. In the developing, early postnatal cerebellum, C1 antigen is not confined to Bergmann glial and ependymal cells but is additionally present in astrocytes of presumptive white matter and Purkinje cell layer. In the embryonic neuroectoderm, C1 antigen is already expressed at day 10, the earliest stage tested so far. The antigen is distinguished in radially oriented structures in telencephalon, pons, pituitary anlage, and retina. Ventricular cells are not labeled by C1 antibody at this stage. C1 antigen is not detectable in astrocytes of adult or nearly adult cerebella from the neurological mutant mice staggerer, reeler, and weaver, but is present in ependymal cells and large blood vessels. C1 antigen is expressed not only in the intact animal but also in cultured cerebellar astrocytes and fibroblastlike cells. It is localized intracellularly.

Characterization of cells of amniotic fluids by immunological identification of intermediate-sized filaments: presence of cells of different tissue origin

Antibodies against intermediate-sized filaments, of the prekeratin or vimentin type, were used to investigate the presence of these filaments by indirect immunofluorescence microscopy in cultured and non-cultured amniotic fluid cells, in frozen sections of the placenta and in isolated cells of the amniotic epithelium. Two major classes of cells can be cultured from amniotic fluids, namely cells of epithelial origin containing filaments of the prekeratin type and cells of different origin which contain filaments of the vimentin type but are negative when tested with antibodies to epidermal prekeratin. The presence of prekeratin type filaments correlates with the morphology of colonies of amniotic fluid cell cultures in vitro as classified by Hoehn et al. (1974). Cells of E-type colonies are shown to be of epithelial origin. In contrast our data indicate a different origin of almost all cells of F-type colonies and of the large majority of cells of AF-type colonies. Cells of epithelial origin and positively stained with antibodies to epidermal prekeratin are occasionally scattered in F-type colonies and in variable percentages (up to 30%) in AF-type colonies. Surprisingly, cryostat sections of the amniotic epithelium and isolated groups of amniotic cells showed positive reactions with both antibodies to vimentin and prekeratin. The possibility that amniotic cells may be different from other epithelial cells in that they contain both types of filaments simultaneously already in situ is presently under investigation.