Quantification of the D2-glycoprotein in amniotic fluid and serum from pregnancies with fetal neural tube defects

Progression in multiple sclerosis is associated with low endogenous NCAM

Multiple sclerosis (MS) is a CNS disorder characterized by demyelination and neurodegeneration. Although hallmarks of recovery (remyelination and repair) have been documented in early MS, the regenerative capacity of the adult CNS per se remains uncertain with the wide held belief that it is either limited or non-existent. The neural cell adhesion molecule (NCAM) is a cell adhesion molecule that has been widely implicated in axonal outgrowth, guidance and fasciculation. Here, we used in vitro and in vivo of MS to investigate the role of NCAM in disease progression. We show that in health NCAM levels decrease over time, but this occurs acutely after demyelination and remains reduced in chronic disease. Our findings suggest that depletion of NCAM is one of the factors associated with or possibly responsible for disease progression in MS.

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.

Maternal low-level lead exposure reduces the expression of PSA-NCAM and the activity of sialyltransferase in the hippocampi of neonatal rat pups

Highly polysialylated neural cell adhesion molecule (PSA-NCAM) is transiently expressed specifically in newly generated cells, and is important for cell migration and neurite outgrowth. Developmental lead (Pb) exposure has been considered to affect the expression of PSA-NCAM, which contributes to the neurotoxicity of Pb exposure. However, the effect of maternal low-level Pb exposure on the expression of PSA-NCAM in neonatal rat pups has not been reported. In the present study, female Wistar rats were exposed to vehicle or different dosages of lead chloride (0.5-4mM PbCl2) 2 weeks before and during pregnancy. This exposure protocol resulted in neonatal rat pups blood Pb levels up to 12.12+/-0.38 microg/dl, and hippocampal Pb levels up to 9.22+/-0.81 microg/g at postnatal day 1 (PND 1). Immunohistochemistry analysis and Western blot analysis revealed that the expressions of PSA-NCAM and NCAM in the hippocampi of neonatal rat pups at PND 1 were significantly reduced by the maternal low-level Pb exposures. Furthermore, the mRNA levels of NCAM and polysialyltransferases (STX and PST), measured by the fluorescent real-time quantitative RT-PCR, dosage-dependently and significantly decreased by 13.26-37.62%, 25.17-59.67%, and 10.78-47.81%, respectively. In addition, the sialyltransferase activity in neonatal rat pups was significantly reduced by 6.23-32.50% in the presence of the low-level Pb exposure, too. Taken together, these results suggest that maternal low-level Pb exposure reduces the expression of PSA-NCAM, NCAM, and the activity of sialyltransferase in the hippocampi of neonatal rat pups, which might contribute to the learning and memory impairments in the developmental pups following maternal low-level Pb exposure.

Alcohol exposure alters the expression pattern of neural cell adhesion molecules during brain development

Neural cell adhesion molecules (NCAMs) play critical roles during development of the nervous system. The aim of this study is to investigate the possible effect of ethanol exposure on the pattern of expression and sialylation of NCAM isoforms during postnatal rat brain development because alterations in NCAM content and distribution have been associated with defects in cell migration, synapse formation, and memory consolidation, and deficits in these processes have been observed after in utero alcohol exposure. The expression of NCAM isoforms in the developing cerebral cortex of pups from control and alcohol-fed mothers was assessed by western blotting, ribonuclease protection assay, and immunocytochemistry. The highly sialylated form of NCAM [polysialic acid (PSA)-NCAM] is mainly expressed during the neonatal period and then is down-regulated in parallel with the appearance of NCAM 180 and NCAM 140. Ethanol exposure increases PSA-NCAM levels during the neonatal period, delays the loss of PSA-NCAM, decreases the amount of NCAM 180 and NCAM 140 isoforms, and reduces sialyltransferase activity during postnatal brain development. Neuraminidase treatment of ethanol-exposed neonatal brains leads to more intense band degradation products, suggesting a higher content of NCAM polypeptides carrying PSA in these samples. However, NCAM mRNA levels are not changed by ethanol. Immunocytochemical analysis demonstrates that ethanol triggers an increase in PSA-NCAM immunolabeling in the cytoplasm of astroglial cells, accompanied by a decrease in immunogold particles over the plasma membrane. These findings indicate that ethanol exposure during brain development alters the pattern of NCAM expression and suggest that modification of NCAM could affect neuronal-glial interactions that might contribute to the brain defects observed after in utero alcohol exposure.

Polysialylated neural cell adhesion molecule in childhood rhabdomyosarcoma

Rhabdomyosarcoma (RMS) cells express the polysialylated (PSA) form of the neural cell adhesion molecule (NCAM). During embryogenesis, PSA-NCAM is widespread and dynamically regulates embryonal developing processes, whereas postnatally, PSA-NCAM becomes restricted to a few regions of neural plasticity and regenerating neural tissues. Recently, PSA-NCAM has been shown to be a diagnostic and prognostic marker in adult patients with small cell lung cancer and multiple myeloma, both PSA-NCAM-expressing tumors. In this study, we determined the amount of PSA-NCAM in tumor specimens of nine children with different histologic types and clinical stages of RMS immunohistochemically, using the polysialic acid-specific MAb 735. In seven children, serum levels were investigated by an immunoluminescence assay using the same MAb. Patients with extensive disease showed strong staining of the tumor specimens, whereas patients with limited stages or after chemotherapy had distinctly a lesser amount of PSA-NCAM or almost no staining. Simultaneously, the serum levels were very high (up to 9-fold) in patients with extensive disease, whereas patients with limited disease or after successful therapy had normal serum levels. We conclude that PSA-NCAM expression is high in tumor specimens and serum of patients with advanced stages of RMS and decreases during successful therapy. PSA-NCAM might therefore serve as a marker for diagnosis and monitoring childhood RMS.

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.

A monoclonal antibody against Meningococcus group B polysaccharides used to immunocapture and quantify polysialylated NCAM in tissues and biological fluids

Polysialylated isoforms of neural cell adhesion molecule (PSA-NCAM) are transiently expressed in many tissues during development and in discrete areas of the adult central nervous system. In pathological situations, they are expressed by poorly differentiated tumor cells of neuroectodermal origin and by regenerating muscle. An ELISA is introduced here to estimate the relative concentrations of PSA-NCAM expressed by tissues or released into biological fluids. In this double-sandwich assay, an anti-PSA antibody (anti-MenB) was adsorbed onto plastic plates and permitted the immunocapture of PSA-bearing molecules. It is demonstrated that these molecules are major NCAM. The second antibody was directed against an amino acid sequence shared by NCAM isoforms in several species. The standard curves were established using Nonidet P40 extracts of human or mouse embryonic brain known to be rich in PSA-NCAM. The sensitivity of the assay allows for quantitation of PSA-NCAM in muscle during regeneration and in small samples of cerebrospinal fluid from patients with medulloblastoma metastasis.

Detection of the neural cell adhesion molecule (NCAM) in serum of patients with small-cell lung cancer (SCLC) with "limited" or "extensive" disease, and bone-marrow infiltration

The neural cell adhesion molecule (NCAM) is a tumour-related antigen found on the surface of small-cell lung cancer (SCLC). NCAM exists in several molecular forms, including a soluble isoform. We have measured serum levels of NCAM using an enzyme immunoassay with 2 antibodies, NCC-LU-246 and NCC-LU-243, that react with different epitopes on the NCAM molecule. NCAM activity from 83 patients with active SCLC, either pre-treatment, progressing or in relapse was significantly higher than in 70 patients on follow-up. Overall, 40% of patients with active SCLC and 7% patients on follow-up had serum levels of NCAM > 2SD above controls; 61% of patients with relapsed SCLC had elevated levels of NCAM. Pre-treatment NCAM levels were significantly higher in 35 patients with "extensive" disease than in 19 patients with "limited" disease. Serum NCAM activity was also significantly higher in patients with tumour infiltration of the bone marrow. This difference could not be explained solely by the presence of "extensive" disease. Serum NSE levels in these patients were correlated with NCAM activity. The presence of raised serum NCAM in active disease and in patients in relapse suggests that this antigen could be used as a target for antibody-directed therapy of micrometastases.

Intact transmembrane isoforms of the neural cell adhesion molecule are released from the plasma membrane

Three soluble neural cell adhesion molecule (NCAM) polypeptide classes of M(r) values 190,000 (NCAM-s1), 135,000 (NCAM-s2) and 115,000-110,000 (NCAM-s3) have been demonstrated in rat brain and cerebrospinal fluid [Krog, Olsen, Dalseg, Roth and Bock (1992) J. Neurochem. 59, 838-847]. NCAM-s3 is known to arise from released glycosylphosphatidylinositol (GPI)-linked NCAM [He, Finne and Goridis (1987) J. Cell. Biol. 105, 2489-2500] as well as from extracellularly cleaved transmembrane NCAM isoforms [Nybroe, Linnemann and Bock (1989) J. Neurochem. 53, 1372-1378]. In this study the origin of NCAM-s1 and NCAM-s2 and the function of soluble NCAM forms were investigated. It was shown that all three soluble forms could be released from brain membranes with M(r) values identical to the three major membrane-associated forms: the large transmembrane 190,000-M(r) form (NCAM-A), the smaller transmembrane 135,000-M(r) form (NCAM-B) and the GPI-anchored 115,000-110,000-M(r) form (NCAM-C). A polyclonal antibody, directed against transmembrane and cytoplasmic epitopes common to NCAM-A and NCAM-B, was shown to react with NCAM-s1 and NCAM-s2. Furthermore, NCAM-B was shown to be shed in a presumably intact soluble form from membranes of cells transfected with this isoform. Thus, NCAM-s1 and NCAM-s2 probably represent intact released transmembrane NCAM-A and NCAM-B. The soluble transmembrane forms are likely to exist in vivo, as NCAM-s1 and NCAM-s2 were readily demonstrated in cerebrospinal fluid. By density-gradient centrifugation it was shown that shed transmembrane NCAM-B was present in fractions of high, as well as low, density, indicating that a fraction of the shed NCAM is associated with minor plasma membrane fragments. Finally, it was shown that isolated soluble NCAM inhibited cell binding to an immobilized NCAM substratum, attributing a pivotal role to soluble NCAM in vivo as a modulator of NCAM-mediated cell behaviour.

Evaluation of serum neural cell adhesion molecule as a new tumor marker in small cell lung cancer

BACKGROUND

Small cell lung cancer (SCLC) is distinguished from other histologic types of lung cancer by possessing a variety of neuroendocrine properties. Neuron-specific enolase (NSE) is the most frequently elevated tumor marker for patients with SCLC at diagnosis. To assess the value of neural cell adhesion molecules (NCAM), another possible tumor marker for small cell lung cancer, NCAM was evaluated in the sera of patients with histologically confirmed SCLC in two prospective multicenter trials.

METHODS

The study includes 221 patients with SCLC, normal human blood donors (n = 34), patients with benign lung disease (n = 53), and patients with non-small cell lung cancer (n = 28). NCAM was determined by means of an enzyme immunoassay, NSE by a radioimmunoassay.

RESULTS

The data show the following: (1) 51% (113 of 221) of all patients with SCLC had NCAM levels higher than 20 U/ml, 34% (75 of 221) had NSE levels higher than 25 ng/ml; (2) levels of both markers significantly differ between limited and extensive disease patients; (3) patients with pathologic NCAM and NSE levels have significantly shorter survival times; (4) a positive correlation between pretreatment NSE and NCAM levels was found (n = 221, r = 0.60); and (5) a correlation between serum marker levels and clinical status was found in follow-up studies of 19 patients.

CONCLUSIONS

From these data, it is concluded that NCAM is, along with NSE, a potential tumor marker for SCLC.

CSF and serum brain-specific creatine kinase isoenzyme (CK-BB), neuron-specific enolase (NSE) and neural cell adhesion molecule (NCAM) as prognostic markers for hypoxic brain injury after cardiac arrest in man

Creatine kinase (CK) and its brain-specific isoenzyme (CK-BB), neuron-specific enolase (NSE), neural cell adhesion molecule (NCAM) and the ions sodium, potassium, chloride and calcium were measured both in CSF and serum and inorganic phosphate in CSF in order to assess their prognostic value in total brain ischemia due to cardiac arrest. The samples were collected at 4, 28 and 76 h after resuscitation. Twenty consecutive patients resuscitated from ventricular fibrillation or asystole were included in the study. Nine of the patients recovered consciousness (recovered) but eleven remained comatose (disabled). The follow-up period was 2 years after which only one patient was still alive. The earliest statistically significant differences between neurologically recovered and disabled patient groups were seen in CSF inorganic phosphate (P = 0.030) already at 4 h and CK-BB (P = 0.046) and NSE (P = 0.020) activity at 28 h. Later, at 76 h after the resuscitation CSF NSE differentiated the groups most clearly (P = 0.014). The values were higher in the disabled patients. A negative correlation between CSF parameters and Glasgow Coma scores was also seen at these timepoints. Statistically significant differences between the groups were seen in both CSF and blood pCO2, pO2, base excess (BE) and actual bicarbonate (HCO3-). CSF or serum NCAM has no prognostic value in anoxic-ischemic coma. The results suggest that in CSF CK-BB and NSE are useful prognostic indicators of hypoxic brain injury when measured 28-76 h after cardiac arrest whereas blood samples have no prognostic value.

Biosynthesis and expression of the myelin-associated glycoprotein in cultured oligodendrocytes from adult bovine brain

The biosynthesis and expression of myelin-associated glycoprotein (MAG) were investigated in cultured oligodendrocytes isolated from adult bovine brain. Western blotting revealed two prominent MAG bands that were present in comparable amounts; the larger component electrophoresed above the 97 kD standard but was slightly smaller than the MAG band in purified bovine myelin, and the smaller component electrophoresed below the 97 kD standard. In comparison to other precursors of oligosaccharides, inorganic [35S]sulfate was a relatively specific isotope for labeling MAG relative to other glycoproteins in the cells. Sulfate labeled only the larger of the two MAG components, which contains complex N-linked oligosaccharides, but which appears to be glycosylated to a lesser extent than MAG in vivo. The smaller MAG band in the cells is a form with high-mannose oligosaccharides and was not detected in purified bovine myelin. Both the large and small MAG components were expressed on the oligodendrocyte surface as indicated by their sensitivity to neuraminidase and/or trypsin treatment of live cells. MAG was also released by the oligodendrocytes into the culture medium. The MAG in the medium was slightly smaller than that in the cells, suggesting that it may be released from the cell surface by limited proteolysis. The release of MAG by myelin-forming cells could be relevant to physiological roles that have been postulated for soluble forms of MAG and other adhesion proteins.

Characterization of soluble neural cell adhesion molecule in rat brain, CSF, and plasma

The polypeptide composition and glycosylation of soluble isoforms of neural cell adhesion molecule (NCAM) in developing rat brain, CSF, and plasma were characterized. Soluble NCAM in rat brain consisted of several glycosylated isoforms. The degree of glycosylation was developmentally regulated. After desialylation, four polypeptides of M(r) values of approximately 190,000 (s1), 135,000 (s2), 115,000 (s3), and 110,000 (s4) were observed. Polypeptides s1, s2, and s3 were also present in CSF, whereas only s3 and s4 were observed in plasma. Treatment of soluble brain NCAM with N-glycosidase F, which removes N-linked carbohydrates, produced polypeptides of M(r) values of approximately 190,000, 125,000, and 108,000-97,000. The monoclonal antibody OB11, which recognizes an epitope on the cytoplasmic part of transmembrane forms of NCAM, did not react with any of the soluble isoforms. Purified soluble NCAM, consisting mainly of s3, contained an N-terminal sequence identical to that of membrane-associated NCAM. Gel filtration of s3 indicated that it was present as a dimer under the chosen conditions. NCAM-expressing glioma cells adhered specifically to immobilized soluble NCAM. This implies that functionally significant soluble forms of NCAM are present in the extracellular fluid.

Interactions of the neural cell adhesion molecule and the myelin-associated glycoprotein with collagen type I: involvement in fibrillogenesis

To gain insights into the functional role of the molecular association between neural adhesion molecules and extracellular matrix constituents, soluble forms of the myelin-associated glycoprotein (MAG) and the neural cell adhesion molecule (N-CAM), representing most of the extracellular domains of the molecules, were investigated in their ability to modify fibrillogenesis of collagen type I. MAG and N-CAM retarded the rate of fibril formation, as measured by changes in turbidity, and increased the diameter of the fibrils formed, but did not change the banding pattern when compared to collagen type I in the absence of adhesion molecules. Scatchard plot analysis of the binding of MAG and N-CAM to the fibril-forming collagen types I, II, III, and V suggest one binding site for N-CAM and two binding sites for MAG. Binding of MAG, but not of N-CAM, to collagen type I was decreased during fibril formation, probably due to a reduced accessibility of one binding site for MAG during fibrillogenesis. These results indicate that the neural adhesion molecules can influence the configuration of extracellular matrix constituents, thus, implicating them in the modulation of cell-substrate interactions.

Cell adhesion molecules and the regulation of development

Cell adhesion molecules, in conjunction with the other morphoregulatory molecules, substrate adhesion molecules and cell junctional molecules, are dynamically expressed in coordinate patterns throughout development. Their activities are linked to a variety of cellular processes, and their ability to influence mechanochemical processes allows them to influence a variety of other fundamental developmental events. The clinical significance of these molecules remains to be determined, but they are clearly involved in a number of pathologic conditions and could become the focus of a wide range of diagnostic techniques and eventually even therapeutic designs.

Neural cell adhesion molecule expression, neuroendocrine differentiation and prognosis in lung carcinoma

We investigated the expression of the neural cell adhesion molecule (NCAM) in a series of surgically resected lung carcinomas of various histological subtypes by means of a panel of monoclonal antibodies recognising different N-CAM epitopes. In a subgroup of 56 tumours, the results of immunostaining with MAb 123C3--the antibody studied most extensively in our material--were compared to the ultrastructure, and in 231 radically resected non-small cell carcinomas, with histological tumour type and with clinical follow-up data. N-CAM expression was not limited to neuroendocrine tumours, as assessed ultrastructurally. Non-small cell lung carcinomas positive for MAb 123C3 showed post-operative overall and disease-free survival times significantly shorter than 123C3-negative non-small cell carcinomas.

Heterogeneity of soluble neural cell adhesion molecule

Soluble neural cell adhesion molecule (NCAM) from rat brain neuronal cell culture media consists predominantly of a polypeptide of Mr approximately 115,000. Minor amounts of a polypeptide of Mr approximately 180,000 and two inconsistently appearing components of Mr 160,000 and 145,000 are also observed. The Mr 115,000 component is derived from the neuronal membrane NCAM components NCAM-A of Mr 190,000, NCAM-B of Mr 140,000, or both. Thus, as a part of the catabolism of membrane NCAM-A plus -B, a minor fraction is posttranslationally cleaved and recovered in the media as discernible soluble NCAM polypeptides. The half-life of membrane NCAM-A plus -B is less than 24 h. Astrocyte culture media contains a predominant soluble NCAM component of Mr 120,000 derived from membrane-associated NCAM-C. A close comparison of deglycosylated soluble NCAM from astrocyte and neuronal cultures showed a small but consistent difference in Mr, a result suggesting that different NCAM polypeptides are released from the membrane of neurons and astrocytes. In contrast to the Mr 115,000-120,000 NCAM polypeptides, the Mr 180,000 polypeptide from neuronal culture media does not seem to be derived from membrane-attached NCAM and may therefore represent a secreted NCAM isoform.

Expression of the embryonal neural cell adhesion molecule N-CAM in lung carcinoma. Diagnostic usefulness of monoclonal antibody 735 for the distinction between small cell lung cancer and non-small cell lung cancer

Paraffin sections of 19 surgically resected small cell lung carcinomas (SCLC), 33 non-small cell lung carcinomas (NSCLC) of various types, and four bronchial carcinoids were immunostained with monoclonal antibodies (MoAbs) 735 and anti-Leu 7, both recognizing some sugar epitopes present on the neural cell adhesion molecule N-CAM. With MoAb 735, all SCLC were stained focally or diffusely, and one carcinoid was stained focally. Only three of the 33 NSCLC were faintly and focally positive with MoAb 735; these three tumours showed relatively small tumour cells and small, oval nuclei. Anti-Leu 7 stained all the carcinoids, only eight SCLC, sometimes focally, and eight NSCLC. MoAb 735 was thus superior to anti-Leu 7 in distinguishing between SCLC and NSCLE. Since MoAb 735 stained all SCLC strongly and is applicable on paraffin sections, it provides a well-needed addition to the immunomarkers used in the diagnostic distinction of SCLC and NSCLC.

Soluble neural cell adhesion molecule in brain, cerebrospinal fluid and plasma in the developing rat

Neural cell adhesion molecule (NCAM) is a glycoprotein found in neurons, glial cells and muscle cells. In this report we describe the polypeptide composition and amount of soluble NCAM in brain, cerebrospinal fluid (CSF) and plasma in rats of various ages. One-two percent of total NCAM in rat brain was shown to be buffer-soluble. Soluble NCAM in brain, extracted at pH 7.2, constituted an increasing relative proportion of total NCAM during development, whereas the concentration of soluble NCAM in both CSF and plasma decreased in the same period. By radioiodination of brain extracts, CSF, and plasma, soluble NCAM was found to be composed of up to five polypeptides with molecular weights (Mr) of 200,000, 170,000, 150,000, 115,000 and 80,000. The relative composition did not vary significantly with age. The major forms in brain were the polypeptides with Mr of 200,000 and 115,000, whereas in CSF all forms seemed to appear in equal amounts. In plasma the 200,000 and the 170,000 Mr polypeptides were not observed and here the major forms were the 150,000 and 115,000 Mr polypeptides.

Alternative splicing generates a secreted form of N-CAM in muscle and brain

A number of different membrane associated isoforms of the neural cell adhesion molecule (N-CAM) have previously been identified. Here the structure of a novel secreted isoform of N-CAM is established by analysis of a cDNA corresponding to an N-CAM mRNA from human skeletal muscle. The mRNA incorporates a novel sequence block into the extracellular domain, which introduces an in-frame stop codon and thus prematurely terminates the coding sequence, generating a truncated N-CAM polypeptide. Analysis of genomic clones indicates that the inserted sequence is present as a discrete exon within the human N-CAM gene, and Northern analysis shows it to be associated specifically with a 5.2 kb mRNA species from skeletal muscle and brain. Stable transfectants expressing the secreted isoform accumulate it in the cytoplasm and release it to the culture medium. In contrast, cells transfected with cDNA encoding lipid-tailed N-CAM express it predominantly at the cell surface. The existence of a secreted isoform may further expand the spectrum of N-CAM function beyond its known involvement in intercellular adhesion to extracellular matrix interactions.

Characterization of soluble forms of NCAM

Neural cell adhesion molecule (NCAM) has been described as a family of membrane glycoproteins. However, soluble NCAM immunoreactivity has long been recognized. We here show that soluble NCAM is composed of two quantitatively major polypeptides of Mr 180,000 and 115,000 and two minor components of Mr 160,000 and 145,000. Soluble NCAM was immunochemically identical to membrane NCAM, was polysialylated and carried the HNK-1 epitope. It only constituted 0.8% of total NCAM in newborn rat brain. Soluble NCAM appeared in neuronal cell culture medium 15-30 min after the start of synthesis preceding accumulation of membrane-associated NCAM on the cell surface. This indicates that soluble NCAM contains a secreted component.

Characterization of neural cell adhesion molecules (NCAM) expressed by Ewing and neuroblastoma cell lines

The status of the neural cell adhesion molecule NCAM gene which is mapped to human chromosome 11q23-24 has been investigated in Ewing-tumor-derived cell lines which present the t(11;22)(q23-24;q12) translocation characteristic of this malignancy. No rearrangement was detected when 2 different non-overlapping probes to mouse NCAM were used. The expression of the NCAM gene was analysed at both the protein and messenger levels in material extracted from Ewing cell lines, human neuroblastoma cell line and fetal mouse brain. Immune blot and immunoprecipitation studies showed that the neuroblastoma cell line contained more NCAM material than the Ewing lines. In neuroblastoma but not in Ewing, the NCAM material had the electrophoretic characteristics of molecules with long polysialic acid chains. After treatment with endosialidase, the diffusely migrating neuroblastoma material was resolved into 3 discrete bands of 120, 140 and 180 kDa. In Ewing extract, high-molecular-weight NCAM species were also detected with a 3-band pattern more reminiscent of mature brain. Endoglycosidase F treatment of Ewing NCAM indicated that all 3 species were largely N-glycosylated. Northern blot analysis confirmed that NCAM was expressed more abundantly in neuroblastoma than in Ewing cell lines. Among the 4 NCAM messengers (7.0, 6.5, 4.3 and 4.1 kb) detected in the neuroblastoma, the 6.5 kb species was largely predominant. The Ewing messenger RNA pattern was clearly different as the largest 7.0-kb species was virtually absent and the other bands were of similar intensities.

Determination of neuron specific enolase in amniotic fluid and maternal serum for the prenatal diagnosis of fetal neural tube defects

Maternal serum neuron-specific enolase was tested as a marker for fetal nural tube defect. In around 50% of pregnancies with affected fetus the level was elevated. The increase was also found in the amniotic fluids. Normal fetal serum did not display elevation of neuron-specific enolase.

Glial fibrillary acidic protein in amniotic fluids from pregnancies with fetal neural tube defects

The glial fibrillary acidic protein (GFAP) is the subunit protein of intermediate filaments in astrocytes and closely related cell types. By means of an enzyme immunoassay we have determined the concentration of GFAP in amniotic fluids from normal pregnancies and from pregnancies complicated by various fetal malformations. The group of 20 cases of fetal anencephaly had a significantly higher mean amniotic fluid GFAP concentration (115 micrograms/l +/- 133.6 (S.D.), range 6-378 micrograms/l) than the control group of 117 normal pregnancies (13 micrograms/l +/- 5.5 (S.D.), range 0-31 micrograms/l), (P less than 0.001). Two cases of fetal encephalocele likewise had very high amniotic fluid GFAP concentrations. None of the other cases of fetal malformations investigated, including 12 cases of spina bifida, had increased amniotic fluid GFAP concentrations. We conclude that determination of the amniotic fluid GFAP concentration may give additional information in the prenatal diagnosis of fetal nervous system malformations.

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.

Low cerebrospinal fluid concentration of brain-specific protein D2 in patients with normal pressure hydrocephalus

The synaptic membrane glycoprotein D2 was measured in cerebrospinal fluid (CSF) and plasma in 13 patients with normal pressure hydrocephalus (NPH), in 14 patients with primary degenerative dementia of Alzheimer type (PDD), and in 24 patients without evidence of organic nervous disease (controls). Mean CSF D2 concentration was significantly lower in NPH patients: 299 +/- 48 ng/ml (SEM) (P less than 0.001) than in PDD patients: 658 +/- 50 ng/ml (SEM) and in controls 641 +/- 45 ng/ml (SEM). Plasma D2 concentrations were higher in PDD patients compared with those found in controls. Determination of CSF D2 concentrations might be of diagnostic value in discrimination between patients with NPH and PDD patients with enlarged ventricles associated with diffuse brain atrophy.