Monoclonal antibodies as neural cell surface markers

Expression and localization of neural cell adhesion molecule and polysialic acid during chick corneal development

PURPOSE

To assay for expression and localization of neural cell adhesion molecule (NCAM) and polysialic acid (polySia) in the chick cornea during embryonic and postnatal development.

METHODS

Real time quantitative PCR and Western blot analyses were used to determine NCAM expression and polysiaylation in embryonic, hatchling, and adult chick corneas. Immunofluorescence staining for NCAM and polySia was conducted on cryosections of embryonic and adult corneas, whole embryonic corneas, and trigeminal neurons.

RESULTS

NCAM and ST8SiaII mRNA transcripts peaked by embryonic day (E)9, remained steady between E10 and E14 and slowly decreased thereafter during embryonic development. Both gene transcripts showed > 190-fold decline in the adult chick cornea compared with E9. In contrast, ST8SiaIV expression gradually decreased 26.5-fold from E6 to E19, increased thereafter, and rose to the early embryonic level in the adult cornea. Western blot analysis revealed NCAM was polysialylated and its expression developmentally changed. Other polysiaylated proteins aside from NCAM were also detected by Western blot analysis. Five NCAM isoforms including NCAM-120, NCAM-180 and three soluble NCAM isoforms with low molecular weights (87-96 kDa) were present in chick corneas, with NCAM-120 being the predominate isoform. NCAM was localized to the epithelium, stroma, and stromal extracellular matrix (ECM) of the embryonic cornea. In stroma, NCAM expression shifted from anterior to posterior stroma during embryonic development and eventually became undetectable in 20-week-old adult cornea. Additionally, both NCAM and polySia were detected on embryonic corneal and pericorneal nerves.

CONCLUSIONS

NCAM and polySia are expressed and developmentally regulated in chick corneas. Both membrane-associated and soluble NCAM isoforms are expressed in chick corneas. The distributions of NCAM and polySia in cornea and on corneal nerves suggest their potential functions in corneal innervation.

Neural cell adhesion molecule (NCAM) and prealbumin in cerebrospinal fluid from depressed patients

The size of the soluble form of the human cerebrospinal fluid (CSF) neural cell adhesion molecule, NCAM-sol, was by gel permeation chromatography estimated to 160-250 kDa. Within the CSF the concentration of NCAM-sol was found about 15-25% increased in lumbar fluid and 25% increased in ventricular fluid, both compared to cisternal fluid. Whereas prealbumin was found evenly distributed in CSF, albumin was relatively enriched in lumbar fluid. The concentrations of NCAM-sol and prealbumin were measured in lumbar CSF from psychiatric patients. Prealbumin was increased 7.2% and NCAM-sol was decreased 15.1% in depressed patients. The changes were partially normalized during recovery from the depression. The findings can be explained by hypothesizing that endogenous depression is associated with an increased choroid plexus activity and CSF production.

Identification of neuronal cell lineage-specific molecules in the neuronal differentiation of P19 EC cells and mouse central nervous system

P19 embryonic carcinoma (EC) cells are one of the simplest systems for analyzing the neuronal differentiation. To identify the membrane-associated molecules on the neuronal cells involved in the early neuronal differentiation in mice, we generated two monoclonal antibodies, SKY-1 and SKY-2, by immunizing rats with a membrane fraction of the neuronally committed P19 EC cells as an antigen. SKY-1 and SKY-2 recognized the carbohydrate moiety of a 90 kDa protein (RANDAM-1) and the polypeptide core of a 40 kDa protein (RANDAM-2), respectively. In the P19 EC cells, the expression of RANDAM-1 was colocalized to a part of Nestin-positive cells, whereas that of RANDAM-2 was observed in most Nestin-positive cells as well as beta-III-tubulin positive neurons. In the embryonic and adult brain of mice, RANDAM-1 was expressed at embryonic day 8.5 (E8.5), and the localization of antigen was restricted on the neuroepithelium and choroid plexus. The RANDAM-2 expression commenced at E6.0, and the antigen was distributed not only on the neuroepithelium of embryonic brain but on the neurons of adult brain. Collectively, it was concluded that RANDAM-1 is a stage specific antigen to express on the neural stem cells, and RANDAM-2 is constitutively expressed on both the neural stem cells and differentiated neuronal cells in mouse central nervous system (CNS).

Neural cell adhesion molecule (NCAM) as a quantitative marker in synaptic remodeling

The neural cell adhesion molecule (NCAM) participates in adhesion and neuritic outgrowth during nervous system development. In the adult brain, NCAM is considered to be involved in neuronal sprouting and synaptic remodeling. The NCAM concentration of brain tissue has proved to be a useful marker of these processes, especially when viewed in comparison with the concentration of a marker of mature synapses, e.g. D3-protein (SNAP-25) or synaptophysin. The present review focusses on studies of adult brain in which NCAM concentration estimates and NCAM/D3 ratios have been used to evaluate the rate of synaptic remodeling in brain damage and degenerative diseases.

The cellular neurobiology of neuronal development: the cerebellar granule cell

Cerebellar granule cells in vivo and in vitro have been widely used in the study of the cellular neurobiology of neuronal development. We have described the basic neuroanatomical data on the granule cell in the developing and mature cerebellum. The importance of the cytoskeleton in determining the morphology of the granule cell and in process outgrowth and cell migration has been described. Extensive information is now available on the composition of the granule cell cytoskeleton. Cell surface glycoproteins are thought to be involved in the control of cell adhesion and cellular interactions during development. A number of surface molecules belonging to either the N-CAM or the Ng-CAM groups of glycoproteins have been studied in detail in the cerebellum. The role of these proteins in cell adhesion and in granule cell-astroglial interactions during granule cell migration has been reviewed. The survival and differentiation of neurones is controlled by soluble trophic factors. Several factors have been described which act as trophic factors for granule cells in vitro and may do the same in vivo. The numerous studies that have been carried out on the cerebellar granule cell have allowed us to describe certain aspects of the cellular neurobiology of this class of neurones as an example with general significance for the understanding of neuronal differentiation and function.

Postnatal development of rat peripheral nerves: an immunohistochemical study of membrane lipids common to non-myelin forming Schwann cells, myelin forming Schwann cells and oligodendrocytes

Interest in the role of membrane lipids in Schwann cell function prompted this study of lipid antigens on myelin- and non-myelin forming Schwann cells. Using the monoclonal antibodies 07, which recognises galactocerebroside, 08, 09 and 011, the distribution and time course of expression of the 4 membrane lipids have been determined in Schwann cells of the rat sciatic nerve and sympathetic trunk, derived from 1-60-day-old rats. The proportion of Schwann cells binding each monoclonal antibody was found by dissociating the nerves and allowing 3 h for the cells to attach to coverslips, prior to double label immunofluorescence, using the monoclonal antibody in conjunction with antibodies to S100 as a general Schwann cell marker, or P0 to distinguish cells which had formed myelin. All 4 lipid antigens were expressed by myelin forming Schwann cells, appearing just before, or at the time that the cells started to form myelin. Only 011 was restricted to myelin forming Schwann cells. Non-myelin forming Schwann cells expressed 07, 08 and 09. In the cervical sympathetic trunk, the developmental expression of these 3 lipids was essentially complete by postnatal day 20, whereas in the sciatic nerve, expression was not complete until days 40-60. The results show that the biochemical maturation in non-myelin forming Schwann cells differs greatly between different nerves, and may not be completed until several weeks postnatally. The results also demonstrate that in addition to galactocerebroside, other similarities exist in the lipid composition of myelin and the plasma membrane of non-myelin forming Schwann cells since the lipids defined by 08 and 09 antibodies are found among both Schwann cell variants.

Endocrine cells share expression of N-CAM with neurones

The expression of the neural cell adhesion molecule, N-CAM, was examined in the anterior lobe of rat hypophysis by immunocytochemistry at light and electron microscope levels. In addition, N-CAM antigenic determinants present in adrenal medulla, anterior hypophysis and PC12 cells were compared by immunoblotting with those found in cerebellum. All secretory cells in the anterior hypophysis were found to be N-CAM positive on their surfaces, but not all of the three polypeptide determinants typical of cerebellum were present in the endocrine tissues or cell line tested. In addition, a new N-CAM determinant of 49 kDa not present in cerebellum was found in adrenal medulla and hypophysis, although it was absent from PC12 cells. The possible implications of these data are discussed.

Changes in neural cell adhesion molecule (NCAM) structure during vertebrate neural development

Changes in carbohydrate and polypeptide form of the neural cell adhesion molecule (NCAM) have been documented during the development of central nervous system tissue in both chicken and frog. The carbohydrate variations reflect a high and low content of polysialic acid, and for the two vertebrates examined the expression of these forms is similar. At very early stages of neural development NCAM with a low content of polysialic acid is present, during histogenesis of the central nervous system NCAM with a high content of polysialic acid dominates, and there is a gradual return to NCAM with a low content of polysialic acid as the animals approach maturity. In contrast, the order of expression of the major NCAM polypeptide forms is different in the chicken and frog. These findings suggest that changes in sialic acid are a fundamental aspect of the function of NCAM in development, whereas NCAM polypeptide differences may affect events associated with a particular vertebrate. Studies have demonstrated that a decreased sialic acid content enhances the adhesion properties of NCAM. On this basis, we propose that NCAM with a low content of polysialic acid functions both to maintain integrity of neuroepithelium during morphogenesis of the early embryo and to stabilize differentiated structures in the adult, while the decreased adhesive function of NCAM with a high content of polysialic acid provides more plasticity in cell interactions during cell migration, axon outgrowth, and formation of neural circuits.

The N-CAM D2-protein as marker for synaptic remodelling in the red nucleus

We have followed the time-course of changes in the concentration of 3 neuronal and one glial antigen in the red nucleus in rats after unilateral lesion of the cerebellorubral connections. The neuronal markers were the neuronal cell adhesion molecule (N-CAM) D2-protein which is prevalent in newly formed neuronal membranes, and the D1- and D3-proteins, which are found mainly in mature neuronal membranes. The glial marker was S-100, a cytoplasmic protein. Six days after the lesion no changes in the concentration of the markers were found in the partially deafferentiated red nucleus. However, 10 days after the lesion the D2-protein concentration was significantly increased, in contrast to the D1-protein concentration which was decreased. After a further 3 days the D2-protein concentration began to decrease, approaching the still significantly decreased D1-protein concentration. Twenty-one days after the lesion the marker protein concentrations were not significantly changed from normal. However, whereas the concentrations of neuronal membrane markers were lower, the glial S-100 concentration showed a tendency to increase. Furthermore, although the changes in D3-protein concentration were unable to reach statistical significance alone they always followed the direction of D1-protein and were significantly in variance with the changes in D2-protein and S-100 concentrations. Our results support the notion of the N-CAM D2-protein as a useful marker for synaptic turnover in adult brain.

Protein changes in the rat's prefrontal and "inferotemporal" cortex after exposure to visual problems

The proteins D2 (N-CAM) and D3, both markers for brain neuronal membranes, MM, a marker for mitochondria, and CM, a cytoplasmic marker protein, were studied in the prefrontal (anteromedial) cortex and "inferotemporal" (Te2) cortex of rats by crossed immunoelectrophoresis. Three experimental groups were investigated: Rats trained to criterion in a visual pattern discrimination test (learning), those run as yoked controls and finally, rats kept in individual cages and not subjected to any training (passive). Statistical analysis indicated that behavioral procedures and marker proteins contributed significantly to the variation. Further analysis indicated that the significant changes occurred in the D3- and MM-protein and that both the learning and yoked control groups had significantly increased concentrations of these two proteins when compared to the passive group. Furthermore, the concentration of D3- and MM-protein in the yoked control group was significantly higher than that of the learning group. The results seem to indicate that changes in concentration of these proteins can be more easily related to the activity of "searching for an adequate behavioral strategy" than to the formation of an "engram".

Distribution of the adhesion molecules N-CAM and L1 on peripheral neurons and glia in adult rats

There is considerable evidence that the cell surface glycoproteins N-CAM and L1 are important mediators of cell-cell adhesion in the nervous system, at least during development. Numerous studies have been devoted to the molecular properties of these proteins and their adhesion role in embryonic and early postnatal development. Much less is known about their importance in mature tissues. A rigorous and comprehensive description of the cell distribution of these molecules in the adult nervous system would clearly form a useful baseline for functional and biochemical studies. In the present work we have addressed this issue and studied the distribution of N-CAM and L1 throughout adult, as opposed to developing, rat peripheral nervous tissue. Particular attention was paid to the ganglia of the enteric nervous system, since adhesion mechanisms within these ganglia are likely to be placed under unusual demands. We report, for the first time, the presence of N-CAM and L1 on mature sensory, sympathetic and enteric neurons in adult rats. Thus, immunostaining of cell suspensions or short-term cultures showed N-CAM and L1 surface labelling on sympathetic and both large and small dorsal root sensory neurons. Both antigens were also present on the surface of enteric neurons in cultures prepared from 10-day-old rats and neonatal guinea pigs. Immunostaining of sections of enteric ganglia from adults indicated that both molecules were also expressed by mature enteric neurons. In sections of mature sciatic nerve neither N-CAM nor L1 immunoreactivity were detected at the site where the plasma membrane of myelinated axons meets the ad-axonal plasma membrane of the myelin-forming Schwann cell. Thus, both N-CAM and L1 were detected on all major classes of peripheral neurons, while their levels in the plasma membrane of myelinated axons may be significantly down-regulated. Similarly, both N-CAM and L1 were present on all major classes of non-myelin-forming peripheral glia in adult rats. This includes the enteric glial cells of the myenteric ganglia, non-myelin-forming Schwann cells in the sciatic nerve, sympathetic trunk and fine autonomic nerves in the gut wall, and the satellite glial cells of sympathetic and dorsal root sensory ganglia. In contrast, myelin-forming Schwann cells did not express detectable levels of N-CAM and only very low levels of L1, which was mainly located near the nodes of Ranvier.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth cone localization of neural cell adhesion molecule on central nervous system neurons in vitro

Ultrastructural analysis of colloidal gold immunocytochemical staining and immunofluorescence microscopy has been used to study the presence of neural cell adhesion molecule (NCAM) on the surface of neuronal growth cones. The studies were carried out with cultures of rat hypothalamic and ventral mesencephalic cells, using morphology and expression of tyrosine hydroxylase, neurofilaments, and glial fibrillary acidic protein as differential markers for neurons and glia. NCAM was found on all plasmalemmal surfaces of neurons including perikarya and neurites. The density of NCAM varied for different neurons growing in the same culture dish, and neurons had at least 25 times more colloidal gold particles on their plasmalemmal membranes than astroglia. Of particular interest in the present study was a strong labeling for NCAM on all parts of neuritic growth cones, including the lamellar and filopodial processes that extend from the tip of the axon. The density of NCAM was similar on different filopodia of the same growth cone. Therefore, in situations where homophilic (NCAM-NCAM) binding might contribute to axon pathfinding, a choice in direction is more likely to reflect differences in the NCAM content of the environment, rather than the distribution of NCAM within a growth cone. On the other hand, the variation in NCAM levels between single neurons in culture was significant and could provide a basis for selective responses of growing neurites.

Gamma-aminobutyric acid affects the developmental expression of neuron-associated proteins in cerebellar granule cell cultures

The effect of gamma-aminobutyric acid (GABA) on the expression of the neuron-associated D2 and neuron-specific enolase (NSE) was studied during development in culture of cerebellar granule cells. It was found that the presence of GABA during culture development increased the overall protein content. D2 content was also increased but not above the general increase in protein whereas NSE increased above the general level of protein. The presence of GABA in the growth medium also appeared to accelerate the changes in molecular forms of D2 and NSE seen during neuronal development. This suggests that GABA promotes or accelerates the general maturation of neurons, as these two neuron-associated proteins otherwise differ from each other with respect to their subcellular localization and their physiological and biochemical properties.

Normal and malignant neural cells: a comprehensive survey of human and murine nervous system markers

Tumor-associated neural markers are finding increased application in diagnostic histopathology and in the development of brain tumor therapy. The major cell-type-specific markers and monoclonal antibodies that identify murine and human neural cells are reviewed in this study. Monoclonal antibodies, raised against fetal and adult neural tissue, neuroectodermal tumor tissue, or cell line immunogens which recognize epitopes on brain tumors are comprehensively described including antigens common to the nervous, hematopoietic, and immune systems. The clinical application of neural cell markers and monoclonal antibodies for the diagnosis, localization, and treatment of neuroectodermal tumors is reviewed.

Localization of the neuronal cell adhesion molecule D2-protein in explant cultures of dorsal root ganglia by use of the colloidal-gold immunocytochemical technique

The localization of the neuronal cell adhesion molecule (N-CAM), D2-protein, in explant cultures of rat dorsal root ganglia was investigated at the electron microscope level by the use of 17-nm-diameter colloidal gold particles coated with swine anti-rabbit immunoglobulin molecules. The minimum amount of IgG needed to coat the gold particles and the pH optimal for coating were both determined. Immunocytochemical studies of cultures revealed the binding of gold particles to the neuronal plasma membrane, especially on neuritic processes. Schwann cells were not labeled, and the level of unspecific background staining was very low.

Glial cells express N-CAM/D2-CAM-like polypeptides in vitro

The joining together of neurites to form fascicles and the growth of axons along glial surfaces during early development suggest that neurone-neurone and neurone-glial adhesion interactions are of considerable importance for defining nerve tracts. In vitro studies have indicated that adhesion between neurones involves a glycoprotein that has been independently studied under the names of N-CAM (for neural cell adhesion molecule), D2-CAM and BSP-2 (refs 10, 11). As N-CAM/D2-CAM appears to be a homophilic ligand that binds to N-CAM/D2-CAM polypeptide on adjacent cells, this glycoprotein is potentially important in adhesion interactions between any two N-CAM/D2-CAM-expressing cells. While it has been suggested that neurone-glial adhesion involves molecules other than N-CAM/D2-CAM, it is known that N-CAM/D2-CAM antigenic determinants are expressed by glial cells in vivo and that injection of anti-N-CAM antibodies into the eye-cup of chick embryos disrupts normal patterns of neuritic apposition to glial endfeet in the developing optic stalk. Do the molecules expressed by glia share restricted antigenic determinants, or binding domains, with N-CAM/D2-CAM, or are N-CAM/D2-CAM polypeptides expressed by glia? Here we present immunocytochemical evidence which suggests that all classes of macroglia express N-CAM/D2-CAM antigenic determinants on their surfaces and immunochemical analyses which indicate that the molecules expressed by purified astrocytes are closely similar, or identical, to at least some forms of N-CAM/D2-CAM obtained from whole brain or purified neurones. However, our results also suggest that different N-CAM/D2-CAM polypeptides may be separately expressed by neurones and astrocytes.

Cell-surface antigens of developing rat cerebellar neurons: identification with monoclonal antibodies

Three monoclonal antibodies (Mab's), named 3C5.59, 3G5.34, and 3G6.41, that recognize cell-surface antigens found on embryonic and postnatal neurons were selected for study from among a group generated against adult rat synaptic plasma membranes (SPM's). Immunofluorescence staining with these 3 antibodies showed strong reactivity of the processes and much weaker staining of the cell bodies of the small neurons cultured from early postnatal rat cerebella. Mab 3G6.41 also reacted with flat astrocyte-like cells cultured from cerebellum. In contrast Mab's 3C5.59 and 3G5.34 appeared to specifically recognize only the neurons in these cultures. In situ staining of cryostat sections with 3G5.34 and 3G6.41 demonstrated immunoreactivity that was predominantly localized to the molecular layer of the cerebellum in the early postnatal through adult stages, in agreement with the strong staining of neurites seen in primary neuronal cultures. Quantitative analysis of Mab binding to particulate protein preparations from various tissues of the adult rat indicated that each of the antigens is restricted to the nervous system in the adult. Binding studies also indicated that each antigen was enriched approximately 1.5-fold in the SPM fractions compared to total particulate fractions from cerebellum. All 3 Mab's recognize membrane-bound molecules that can be solubilized by non-ionic detergent. Mab 3G6.41 immunoprecipitated two polypeptides of 140,000 and 185,000 apparent molecular weight from detergent-solubilized cerebellar cells that were surface-iodinated in culture. These antibodies should prove useful in the further analysis of the expression and function of individual cell surface antigens during the differentiation of cerebellar granule cells.

Identification of rectal ganglion cells using monoclonal antibodies

A monoclonal antibody has been developed that reacts specifically with ganglion cells of the myenteric and submucous plexuses of the gastrointestinal tract. This antibody also recognizes an axonal antigen that is distributed throughout the circular muscle of normal colon and rectum. Aganglionic segments of colon and rectum from patients with Hirschsprung's disease showed no specific antibody binding using a fluorescent labelled assay. The use of monoclonal antibodies should provide further insights into the pathophysiology of Hirschsprung's disease and allied disorders.

A developmentally modified neurone-specific marker in rodent cerebellum

Out of several monoclonal antibodies secreted by hybridomas resulting from the fusion of a mouse myeloma cell line with spleen cells from mice immunized with cerebellar membranes from 12 day old rats, one, called 11.9, produced an unusual immunolabelling pattern when tested on sections of rat cerebellum. The cerebellar distribution of the antigenic sites recognized by this antibody using an immunoperoxidase technique at the optical and ultrastructural levels is described in detail in this report. The immunoreaction product was found in the adult rat to be associated with the microtubules and the zone immediately beneath the plasma membrane of parallel fibres. In young animals the density of immunostaining appears to be higher than in the adult, and the staining is detectable in addition in the perikaryal cytoplasm of granule cells. Biochemical studies using the Western immunoblot technique demonstrate that the antigens consist of two polypeptides of molecular weights 120 and 185 kD. The possible relation of the antigens to cytoskeletal structures is discussed and the labelling pattern is compared with that produced by other known monoclonal antibodies.

Astrocytic cell clones derived from established cultures of 8-day postnatal mouse cerebella

Clonal permanent cell lines with astrocytic properties have been established from explant cultures of 8-day postnatal mouse cerebella after in vitro spontaneous transformation, i.e. without the addition of carcinogens or oncogenic viruses. The cell lines were derived in a multistage process. Slowly proliferating foci with several morphologies appeared 4 months after initiation of the cultures and became progressively enriched by cells with a homogeneous appearance. These cells could be established into permanent cell lines from which many clones were obtained. Some of these cloned cell lines bound anti-GFAP sera and therefore appeared to be astrocytic. According to their morphology, 3 separate types of these GFAP-positive clones could be distinguished. Type I and II cells had small somata; type I had several short processes, while type II had two processes, one of which was very thin and long (greater than 200 microns). Type III cells had large flat somata and no processes. The three types of clonal cell lines were labeled by monoclonal antibodies which bind to astrocytes in vivo. In particular, three monoclonal antibodies (BSP-3, M2 and M3) bound only to type II cells in a distinct pattern. Type I and II astrocytes are pseudodiploid and type III, heteroploid. The properties of these different clonal cell lines are very stable. We have thus obtained permanently established clonal cultures of mouse cerebellum astrocyte-like cells, which might be the in vitro counterparts of fibrous (type I), or velamentous (type III) astrocytes and of Golgi epithelial cells (type II).

Studies on the transmembrane disposition of the neural cell adhesion molecule N-CAM. A monoclonal antibody recognizing a cytoplasmic domain and evidence for the presence of phosphoserine residues

The N-CAMs are a group of surface glycoproteins involved in adhesive interactions of neurones. Related molecules of the mouse nervous system, identified in our laboratory, have been called BSP-2 and shown to act as ligands in adhesion of neuroblastoma cells. Results presented in this report show that they are immunochemically identical with N-CAM. A monoclonal anti-(N-CAM) antibody, that recognized a determinant accessible only after permeabilization of intact cells, was used to define the mode of association of the N-CAMs with the plasma membrane. This antibody bound a 35 000-Mr fragment in lysates of trypsin-treated neuroblastoma cells. It is concluded that the antibody reacts with a transmembrane or cytoplasmic domain of the molecules. The same antibody recognized the Mr-180 000 and Mr-140 000 proteins but not the Mr-120 000 chain, which co-purify from adult mouse brain. The latter polypeptide was detected in the cytosol and could be partially released from brain membranes by osmotic shock. Part or all of the Mr-120 000 protein may thus lack a transmembrane segment. Our conclusion that the N-CAM forms of higher Mr are transmembrane proteins was further corroborated by our finding that they contain phosphoserine residues, which can be labeled with (32P)phosphate in intact neuroblastoma cells.

Identification of novel neural- and neural retina-specific antigens with a monoclonal antibody

A fluorescence-activated cell sorter screening method has been used to identify hybridomas that secrete monoclonal antibodies that can bind to viable subpopulations of embryonic chicken neural retina cells. One monoclonal antibody, C1H3, recognizes two nervous tissue-specific polypeptides that exhibit distinct developmental patterns. The monoclonal antibody reacts with a 140-kilodalton (kDa) polypeptide that is present at early stages of development (day 7) but is detected by immunoblotting in only negligible amounts at later times (day 17). In contrast, a 170-kDa polypeptide is first detectable by immunoblotting at day 10 and is the predominant C1H3 antigen at day 17. Analysis of proteolytic fragments of the two proteins indicates that the polypeptides are distinct molecules that share a common antigenetic determinant. Both polypeptides are neural-specific; the 140-kDa polypeptide appears to be retina-specific, while the 170-kDa polypeptide is also present in other areas of the nervous system. Metabolic labeling of retina cells in situ at early embryonic stages reveals only the synthesis of the 140-kDa polypeptide. When such cells are dissociated and labeled in vitro, they synthesize primarily the 170-kDa polypeptide. Thus, the differential rate of synthesis of these two polypeptides is controlled by environmental factors that possibly include cell-cell contacts or an unknown systemic factor. The 140-kDa polypeptide is a unique marker for early neural retina cells.

Immunocytological and biochemical characterization of a new neuronal cell surface component (L1 antigen) which is involved in cell adhesion

Monoclonal and polyclonal L1 antibodies react by indirect immunofluorescence with the cell surface of cultured tetanus toxin-positive neurons from post-natal cerebella of mice, but not with glial fibrillary acidic protein-positive astrocytes, O4 antigen-positive oligodendrocytes or fibronectin-positive fibroblasts or fibroblast-like cells. During cerebellar development L1 antigen is detectable on tetanus toxin-positive cells as early as embryonic day 13 after 3 days in culture. In sections of the early post-natal cerebellum, L1 antigen is found on pre-migratory neurons in the internal, but not in the external part of the external granular layer. In the adult cerebellum, L1 antigen is predominantly localized in the molecular layer and around Purkinje cells. Fibers in white matter and the granular layer are also L1 antigen-positive. Granule cell bodies and synaptic glomeruli are weakly antigen-positive. Several cell lines derived from neuroblastoma C1300 also express L1 antigen. The antigen is not detectable by enzyme-linked immunosorbent assay in tissue homogenates of liver, kidney, lung, heart, sperm or thymus. With polyclonal L1 antibodies, cross-reactive determinants are found in brains of rat, guinea pig, hamster, chicken, rabbit and man, but not in frog, while monoclonal antibody reacts detectably only with mouse brain. The molecular species recognized by both monoclonal and polyclonal antibodies display two prominent bands by SDS-PAGE under reducing and non-reducing conditions with apparent mol. wts. of 140 and 200 kd. L1 antigen isolated from cultured cerebellar cells consists mainly of a band in the 200-kd range and a faint one at 140 kd. L1 antigen from neuroblastoma N2A shows two bands with slightly higher apparent mol. wts. All molecular forms of L1 antigen can be labeled by [3H]fucose and [3H]glucosamine. Ca2+-independent re-aggregation of cerebellar cells from early post-natal C57BL/6J mice and of the continuous cell line N2A derived from the murine neuroblastoma C1300 is inhibited by Fab fragments of the polyclonal, but not of monoclonal antibody, both of which are known to react with the surface membrane of these cells.

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.

Enzyme-linked immunosorbent assay of the D2-glycoprotein

D2 is a glycoprotein enriched in neuronal membranes and probably involved in intercellular adhesion. An immunochemical relationship between D2 and the neuronal cell adhesion molecule from chick has been demonstrated. Changes in D2 concentration in human body fluids correlate to certain neurological diseases. We here report the purification of the D2 membrane proteins from fetal and adult human brain and the demonstration of physicochemical differences between the two proteins. Enrichments of 133 times (fetal D2) and 350 times (adult D2) were found. Specific rabbit antisera against the purified D2 proteins were produced, and this enabled the setting up of an enzyme-linked immunosorbent assay for D2 quantification in human brain extracts, cerebrospinal fluids, sera, and amniotic fluids.

Molecular heterogeneity and structural evolution during cerebellar ontogeny detected by monoclonal antibody of the mouse cell surface antigen BSP-2

The monoclonal antibody anti-BSP-2 defines a set of glycoproteins present on the neuronal cell surface in dissociated mouse cerebellar cultures and on neurons and astrocytes in sections of the mouse cerebellum. This antibody was used in the present study to characterize the antigens recognized in cerebellar cultures and in the developing and adult mouse cerebellum in vivo. In extracts from cerebellar cultures and from late postnatal or adult cerebellum, the anti-BSP-2 antibody reacted with a triplet of glycosylated polypeptide chains of 180,000, 140,000 and 120,000 mol. wt. Early postnatal cerebellum contained a different form of BSP-2 antigen which migrated as one broad or several closely spaced diffuse bands in the 190,000-250,000 mol. wt. region of SDS polyacrylamide gels. During cerebellar ontogeny, the adult pattern emerged gradually between postnatal days 5 and 13. The cellular expression of the BSP-2 antigen was studied by immunohistochemistry on sections of the developing cerebellum. At postnatal day 3, the antigen was found mainly on cell bodies and fibers of the Bergmann glia and on astrocytes of the granular layer. Immature granule cells of the outer zone of the external granular layer lacked the antigen, but they appeared to acquire the antigen during their migration to the internal granular layer. At postnatal day 13, the immunofluorescence pattern was not different from the one seen in the adult. These results suggest that the neonatal 190,000-250,000 mol. wt. form of BSP-2 may at least in part be expressed by astroglial cells and they show a close correlation between the emergence of the adult forms of the antigen and the appearance of labeled granule cells in the internal granular layer. In vitro degradation implying cleavage of sialic acid residues, but probably also proteolysis and/or cleavage of different glycans converted the neonatal form of BSP-2 into the triplet pattern and ultimately into a p120 component. Neuraminidase digestion of the adult antigens produced small molecular weight shifts without converting one band into the other, but endogenous enzyme activities were capable of degrading the p180 and p140 bands by converting them into the p120 protein. Our findings support the idea that distinct, but structurally similar surface glycoproteins created by post-translational modifications from a common precursor molecule may be expressed by different cell types or during different developmental stages. As shown by sequential immunoprecipitation experiments, BSP-2 and the rat neuronal membrane protein D2 may belong to the same family of surface glycoproteins.

Tissue- and developmental stage-specific forms of a neural cell surface antigen linked to differences in glycosylation of a common polypeptide

We have previously identified a cell surface glycoprotein of the mouse nervous system named brain cell surface protein-2 (BSP-2). Here we report that this antigen is not a single, discrete entity, but a family of antigenically and structurally related molecules. Three components of 180, 140, and 120 K were characteristic for more mature nervous tissues. Adult cerebral cortex contained the 140-K and 120-K antigens, adult spinal cord only the 120-K, and dorsal root ganglia from young mice mainly the 180-K component. Very different forms of the antigen that migrated as a diffuse zone from 180-250-K in SDS-polyacrylamide gels were found in immature nervous tissues. A molecule different from the previous ones was found in a neuroblastoma line. Evidence is presented that the structural diversity of BSP-2 is due to differences in glycosylation. This result indicates that cell type- and developmental stage-specific glycoprotein patterns previously found in the nervous system may in part be due to different glycosylation of identical polypeptides. The finding that a neural cell surface protein may be glycosylated in different ways has important implications for the generation of cell surface specificity.