Cell type specificity and developmental expression of the L2/HNK-1 epitopes in mouse cerebellum

Functions of Small Organic Compounds that Mimic the HNK-1 Glycan

Because of the importance of the HNK-1 carbohydrate for preferential motor reinnervation after injury of the femoral nerve in mammals, we screened NIH Clinical Collection 1 and 2 Libraries and a Natural Product library comprising small organic compounds for identification of pharmacologically useful reagents. The reason for this attempt was to obviate the difficult chemical synthesis of the HNK-1 carbohydrate and its isolation from natural sources, with the hope to render such compounds clinically useful. We identified six compounds that enhanced neurite outgrowth from cultured spinal motor neurons at nM concentrations and increased their neurite diameter, but not their neurite branch points. Axons of dorsal root ganglion neurons did not respond to these compounds, a feature that is in agreement with their biological role after injury. We refer to the positive functions of some of these compounds in animal models of injury and delineate the intracellular signaling responses elicited by application of compounds to cultured murine central nervous system neurons. Altogether, these results point to the potential of the HNK-1 carbohydrate mimetics in clinically-oriented settings.

Receptor tyrosine phosphatase beta (RPTPbeta) activity and signaling are attenuated by glycosylation and subsequent cell surface galectin-1 binding

O-Mannosyl-linked glycosylation is abundant within the central nervous system, yet very few glycoproteins with this glycan modification have been identified. Congenital diseases with significant neurological defects arise from inactivating mutations found within the glycosyltransferases that act early in the O-mannosyl glycosylation pathway. The N-acetylglucosaminyltransferase known as GnT-Vb or -IX is highly expressed in brain and branches O-mannosyl-linked glycans. Our results using SH-SY5Y neuroblastoma cells indicate that GnT-Vb activity promotes the addition of the O-mannosyl-linked HNK-1 modification found on the developmentally regulated and neuron-specific receptor protein-tyrosine phosphatase beta (RPTPbeta). These changes in glycosylation accompany decreased cell-cell adhesion and increased rates of migration on laminin. In addition, we show that expression of GnT-Vb promotes its dimerization and inhibits RPTPbeta intrinsic phosphatase activity, resulting in higher levels of phosphorylated beta-catenin, suggesting a mechanism by which GnT-Vb glycosylation couples to changes in cell adhesion. GnT-Vb-mediated glycosylation of RPTPbeta promotes galectin-1 binding and RPTPbeta levels of retention on the cell surface. N-Acetyllactosamine, but not sucrose, treatment of cells results in decreased RPTP retention, showing that galectin-1 binding contributes to the increased retention after GnT-Vb expression. These results place GnT-Vb as a regulator of RPTPbeta signaling that influences cell-cell and cell-matrix interactions in the developing nervous system.

A novel role of the Mad family member Mad3 in cerebellar granule neuron precursor proliferation

During development, Sonic hedgehog (Shh) regulates the proliferation of cerebellar granule neuron precursors (GNPs) in part via expression of Nmyc. We present evidence supporting a novel role for the Mad family member Mad3 in the Shh pathway to regulate Nmyc expression and GNP proliferation. Mad3 mRNA is transiently expressed in GNPs during proliferation. Cultured GNPs express Mad3 in response to Shh stimulation in a cyclopamine-dependent manner. Mad3 is necessary for Shh-dependent GNP proliferation as measured by bromodeoxyuridine incorporation and Nmyc expression. Furthermore, Mad3 overexpression, but not that of other Mad proteins, is sufficient to induce GNP proliferation in the absence of Shh. Structure-function analysis revealed that Max dimerization and recruitment of the mSin3 corepressor are required for Mad3-mediated GNP proliferation. Surprisingly, basic-domain-dependent DNA binding of Mad3 is not required, suggesting that Mad3 interacts with other DNA binding proteins to repress transcription. Interestingly, cerebellar tumors and pretumor cells derived from patched heterozygous mice express high levels of Mad3 compared with adjacent normal cerebellar tissue. Our studies support a novel role for Mad3 in cerebellar GNP proliferation and possibly tumorigenesis, and they challenge the current paradigm that Mad3 should antagonize Nmyc by competition for direct DNA binding via Max dimerization.

Isolation of neural stem cells from the postnatal cerebellum

The cerebellum is critical for motor coordination and cognitive function and is the target of transformation in medulloblastoma, the most common malignant brain tumor in children. Although the development of granule cells, the most abundant neurons in the cerebellum, has been studied in detail, the origins of other cerebellar neurons and glia remain poorly understood. Here we show that the murine postnatal cerebellum contains multipotent neural stem cells (NSCs). These cells can be prospectively isolated based on their expression of the NSC marker prominin-1 (CD133) and their lack of markers of neuronal and glial lineages (lin-). Purified prominin+ lin- cells form self-renewing neurospheres and can differentiate into astrocytes, oligodendrocytes and neurons in vitro. Moreover, they can generate each of these lineages after transplantation into the cerebellum. Identification of cerebellar stem cells has important implications for the understanding of cerebellar development and the origins of medulloblastoma.

Cerebellar granule cell precursors can differentiate into astroglial cells

During CNS development, multipotent neural stem cells give rise first to various kinds of specified precursor cells, which proliferate extensively before terminally differentiating into either neurons or glial cells. It is still not clear, however, whether the specified precursor cells are irreversibly determined to differentiate into their particular cell types. In this study, we show that isolated mouse cerebellar granule cell precursors from the outermost, proliferative zone of the external germinal layer can differentiate into astroglial cells when exposed to sonic hedgehog (Shh) and bone morphogenetic proteins. These induced cells initially expressed both glial fibrillary acidic protein and neuronal markers, but they then lost their neuronal markers and acquired S100-beta, a marker of differentiated astroglial cells. These results indicate that at least some granule cell precursors are not irreversibly committed to neuronal development but can be induced to differentiate into astroglial cells by appropriate extracellular signals.

Growth arrest specific gene 1 is a positive growth regulator for the cerebellum

Postnatal cerebellum development involves the generation of granule cells and Bergmann glias (BGs). The granule cell precursors are located in the external germinal layer (EGL) and the BG precursors are located in the Purkinje layer (PL). BGs extend their glial fibers into the EGL and facilitate granule cells' inward migration to their final location. Growth arrest specific gene 1 (Gas1) has been implicated in inhibiting cell-cycle progression in cell culture studies (G. Del Sal et al., 1992, Cell 70, 595--607). However, its growth regulatory function in the CNS has not been described. To investigate its role in cerebellar growth, we analyzed the Gas1 mutant mice. At birth, wild-type and mutant mice have cerebella of similar size; however, mature mutant cerebella are less than half the size of wild-type cerebella. Molecular and cellular examinations indicate that Gas1 mutant cerebella have a reduced number of granule cells and BG fibers. We provide direct evidence that Gas1 is required for normal levels of proliferation in the EGL and the PL, but not for their differentiation. Furthermore, we show that Gas1 is specifically and coordinately expressed in both the EGL and the BGs postnatally. These results support Gas1 as a common genetic component in coordinating EGL cell and BG cell proliferation, a link which has not been previously appreciated.

The HNK-1 carbohydrate epitope in the eye: basic science and functional implications

The HNK-1 carbohydrate epitope is part of many cell membrane and extracellular matrix molecules. It has been implicated in cell to cell and cell to extracellular matrix adhesion, and antibodies to the HNK-1 epitope are emerging as a versatile tool in eye research. They have been used to identify a novel cell type in the human eye, the subepithelial matrix cells that reside in the inner connective tissue layer (ICTL) of the ciliary body. Although these cells resemble fibroblasts in ultrastructure, they form a distinct cell population that differs in its antigenic profile from fibroblasts of other tissues. These cells are associated with the elastic fiber system of the ICTL. Other structures in the human eye that harbor the HNK-1 epitope in a nonrandom pattern are the ciliary and iris epithelia, the zonular lamella, the lens capsule, the retina, glial cells of the optic and ciliary nerves, and scleral fibroblasts. The HNK-1 epitope in the eye appears early during embryonic development and is phylogenetically conserved, but many interspecies differences exist in its distribution. The role of the HNK-1 epitope may be to structurally stabilize the ciliary body and the retina, and to participate in zonular attachments. The HNK-1 epitope has been linked with many common eye diseases. The subepithelial matrix cells seem to be susceptible to undergo irreversible damage as a result of glaucoma, thermal injury, and tissue compression. This epitope has proved to be useful in identifying intraocular deposits of exfoliation syndrome. It can explain the adhesiveness of exfoliation material. Intraocular exfoliation material differs in HNK-1 immunoreactivity from the extraocular fibrillopathy of exfoliation syndrome and its presence in fellow eyes also argues against the concept of unilateral exfoliation syndrome. The HNK-1 epitope is found in the extracellular matrix of secondary cataract and anterior subcapsular cataract, and it may contribute to their pathogenesis. Finally, the HNK-1 epitope can be used to trace neuroepithelial derivatives of the optic vesicle in developmental anomalies and in tumors of the eye. Eventual identification of molecules that bear the HNK-1 epitope in the eye will likely shed light on many aspects of ocular physiology and pathobiology

Control of neuronal precursor proliferation in the cerebellum by Sonic Hedgehog

Cerebellar granule cells are the most abundant type of neuron in the brain, but the molecular mechanisms that control their generation are incompletely understood. We show that Sonic hedgehog (Shh), which is made by Purkinje cells, regulates the division of granule cell precursors (GCPs). Treatment of GCPs with Shh prevents differentiation and induces a potent, long-lasting proliferative response. This response can be inhibited by basic fibroblast growth factor or by activation of protein kinase A. Blocking Shh function in vivo dramatically reduces GCP proliferation. These findings provide insight into the mechanisms of normal growth and tumorigenesis in the cerebellum.

Expression of HNK-1 carbohydrate and its binding protein, SBP-1, in apposing cell surfaces in cerebral cortex and cerebellum

Sulfoglucuronyl carbohydrate is the terminal moiety of neolacto-oligosaccharides, expressed on several glycoproteins of the immunoglobulin superfamily involved in cell-cell recognition and on two glycolipids. Sulfoglucuronyl carbohydrate is temporally and spatially regulated in the developing nervous system. It appears to be involved in neural cell recognition and in cell adhesion processes through its interaction with specific proteins on cell surfaces. Previously we have characterized a specific sulfoglucuronyl carbohydrate-binding protein in rat brain. Sulfoglucuronyl carbohydrate binding protein-1 is structurally similar to a 30,000 mol. wt adhesive and neurite outgrowth promoting protein amphoterin [Rauvala and Pihlaskari (1987) J. biol. Chem. 262, p. 16,625]. The pattern of expression of sulfoglucuronyl carbohydrate binding protein-1 in developing rat nervous system was studied to understand the significance of its interaction with sulfoglucuronyl carbohydrate-bearing molecules. Biochemical analyses showed that the expression of sulfoglucuronyl carbohydrate binding protein-1 was developmentally regulated similarly to sulfoglucuronyl carbohydrate. Immunocytochemical localization of sulfoglucuronyl carbohydrate binding protein-1 and sulfoglucuronyl carbohydrate was performed by bright-field and fluorescent confocal laser scanning microscopy. In postnatal day 7 rat cerebellum, sulfoglucuronyl carbohydrate binding protein-1 was primarily associated with neurons of the external and internal granule cell layers. The sulfoglucuronyl carbohydrate binding protein-1 immunoreactivity was absent in Purkinje cell bodies and their dendrites in the molecular layer, as well as in Bergmann glial fibres and in white matter. In contrast, sulfoglucuronyl carbohydrate (reactive with HNK-1 antibody) was localized in processes surrounding granule neurons in the internal granule cell layer. Sulfoglucuronyl carbohydrate was also expressed in Purkinje neurons and their dendrites in the molecular layer and their axonal processes in the white matter. To a lesser extent Bergmann glial fibres were also positive for sulfoglucuronyl carbohydrate. In the cerebral cortex, at embryonic day 21, sulfoglucuronyl carbohydrate binding protein-1 was mainly observed in immature neurons of the cortical plate and subplate and dividing cells near the ventricular zone. Whereas, sulfoglucuronyl carbohydrate was strongly expressed in the fibres of the subplate and marginal zone. Sulfoglucuronyl carbohydrate was also found in the processes surrounding the sulfoglucuronyl carbohydrate binding protein-1-expressing neuronal cell bodies in the cortical plate and in ventricular zone. The specific localization of sulfoglucuronyl carbohydrate binding protein- in cerebellar granule neurons and neurons of the cerebral cortex was also confirmed by immunocytochemistry of the dissociated tissue cell cultures. The complementary localization of sulfoglucuronyl carbohydrate and sulfoglucuronyl carbohydrate binding protein-1, both in cerebral cortex and cerebellum, in apposing cellular structures indicate possible interaction between the two and signalling during the process of cell migration and arrest of migration.

Expression cloning of a cDNA encoding a sulfotransferase involved in the biosynthesis of the HNK-1 carbohydrate epitope

The HNK-1 carbohydrate epitope is expressed on several neural adhesion glycoproteins and as a glycolipid, and is involved in cell interactions. The structural element of the epitope common to glycoproteins and glycolipids has been determined to be sulfate-3-GlcAbeta1--> 3Galbeta1-->4GlcNAc. The glucuronyltransferase and sulfotransferase are considered to be the key enzymes in the biosynthesis of this epitope because the rest of the structure occurs often in glycoconjugates. Here we describe the isolation of the rat sulfotransferase cDNA via an expression cloning strategy. The clone finally isolated predicts a protein of 356 amino acids, with characteristics of a type II transmembrane protein and with no sequence similarity to other known sulfotransferases. Both the enzyme expressed as a soluble fusion protein and homogenates of cells transfected with the full-length cDNA could transfer sulfate from a sulfate donor to acceptor substrates containing terminal glucuronic acid.

N-Acetylglucosaminyl transferase regulates the expression of the sulfoglucuronyl glycolipids in specific cell types in cerebellum during development

In the adult cerebellum, sulfoglucuronyl glycolipids (SGGLs) are specifically localized in Purkinje cells and their dendrites in the molecular layer. Other major cell types such as granule neurons and glial cells lack SGGLs. To explain the cell specific localization and the known biphasic expression of SGGLs, enzymic activities of four glycosyltransferases involved in the biosynthesis of SGGLs were studied in murine cerebellar mutants, in distinct cellular layers of rat cerebellum, and in isolated granule neurons during development. The enzymes studied were lactosylceramide: N-acetylglucosaminyl transferase (GlcNAc-Tr), lactotriaosylceramide:galactosyltransferase, neolactotetraosylceramide:glucuronyltransferase, and glucuronylglycolipid:sulfotransferase. In the cerebellum of Purkinje cell-deficient mutants, such as (pcd/pcd) and lurcher (Lc/+) where Purkinje cells are lost, GlcNAc-Tr was absent, but the other three glycosyltransferase were not severely affected. This indicated that the latter three enzymes were localized in other cell types, such as in mature granule neurons and glial cells, in addition to that in Purkinje cells, and the lack of SGGLs in these mutants was due to absence of GlcNAc-Tr. Analyses of the enzymes in the specific micro-dissected cellular layers also showed that Purkinje cell layer and molecular layer (where Purkinje cell dendrites are localized) contained all four enzymes. However, granule neurons and glial cells in the white matter lacked GlcNAc-Tr, but expressed the other three enzymes. It was concluded that the absence of SGGLs in adult granule neurons and glial cells was due to specific deficiency of the GlcNAc-Tr. Although adult granule neurons lacked GlcNAc-Tr and therefore SGGLs, isolated granule neurons from the neonatal cerebellum contained all four enzymes necessary for the synthesis of SGGLs. With development, the activity of GlcNAc-Tr in the isolated granule neurons declined but the other enzymes were not as affected, indicating that immature granule neurons were capable of synthesizing SGGLs and with maturation the synthesis was down-regulated. This also explains the biphasic expression of SGGLs in the developing cerebellum.

Expression of neolactoglycolipids: sialosyl-, disialosyl-, O-acetyldisialosyl- and fucosyl- derivatives of neolactotetraosyl ceramide and neolactohexaosyl ceramide in the developing cerebral cortex and cerebellum

The following neolacto glycolipids were identified and their developmental expression was studied in the rat cerebral cortex and cerebellum: Fuc alpha 1-3IIInLcOse4Cer,Fuc alpha 1-3VnLcOse6Cer and (Fuc)2 alpha 1-3III,3VnLcOse6Cer, as well as acidic glycolipids, NeuAc alpha 2-3IVnLcOse4Cer [nLM1], (NeuAc)2 alpha 2-3IVnLcOse4Cer [nLD1], O-acetyl (NeuAc)2 alpha 2-3IVnLcOse4Cer [OAc-nLD1] and their higher neolactosaminyl homologues NeuAc alpha 2-3VlnLcOse6Cer [nHM1] and (NeuAc)2 alpha 2-3VlnLcOse6Cer [nHD1]. These glycolipids were expressed in the cerebral cortex only during embryonic stages and disappeared postnatally. This loss was ascribed to the down regulation of the synthesis of the key precursor LcOse3Cer which is synthesized by the enzyme lactosylceramide: N-acetylglucosaminyl transferase. On the other hand in the cerebellum, these glycolipids increased with postnatal development due to increasing availability of LcOse3Cer. In the cerebellum, only nLM1 and fucosyl-neolactoglycolipids declined after postnatal day 10-15, perhaps due to regulation by other glycosyltransferases. Also, in the cerebellum, nLD1 and nHD1 were shown to be specifically associated with Purkinje cells and their dendrites in the molecular layer and with their axon terminals in the deep cerebellar nuclei, similar to other neolactoglycolipids shown previously.

Expression and biological functions of sulfoglucuronyl glycolipids (SGGLs) in the nervous system--a review

Sulfoglucuronyl carbohydrate linked to neolactotetraose reacts with HNK-1 antibody. The HNK-1 carbohydrate epitope is found in two major glycolipids, several glycoproteins and in some proteoglycans of the nervous system. Most of the HNK-1 reactive glycoproteins so far identified are neural cell adhesion molecules and/or are involved in cell-cell interactions. HNK-1 carbohydrate is highly immunogenic. Several HNK-1-like antibodies, including IgM of some patients with plasma cell abnormalities and having peripheral neuropathy, have been described. This article summarizes published work mainly on sulfoglucuronyl glycolipids, SGGLs and covers: structural requirements of the carbohydrate epitope for binding to HNK-1 and human antibodies, expression of the lipids in various neural areas, stage and region specific developmental expression in CNS and PNS, immunocytochemical localization, loss of expression in Purkinje cell abnormality murine mutations, biosynthetic regulation of expression by a single enzyme N-acetylglucosaminyl transferase, identification of receptor-like carbohydrate binding neural proteins (lectins), and perceived role of the carbohydrate in physiological functions. The latter includes role in: pathogenesis of certain peripheral neuropathies, in migration of neural crest cells, as a ligand in cell-cell adhesion/interaction and as a promoter of neurite outgrowth for motor neurons. Multiple expression of HNK-1 carbohydrate in several molecules and in various neural cell types at specific stages of nervous system development has puzzled investigators as to its specific biological function, but this may also suggest its importance in multiple systems during cell differentiation and migration processes.

Oligodendrocyte reactions and cell proliferation markers in human demyelinating diseases

We have carried out immunocytochemical reactions using antibodies to markers of oligodendrocytes, astrocytes, microglia and proliferating cells (PCNA) in sections of human brain in a variety of demyelinating conditions and human immunodeficiency virus (HIV) infection. In the acute phases of demyelinating diseases we found marked reactive changes in oligodendrocytes with hyperplasia and an increased cytoplasmic reaction using antibodies to enzymes involved in myelin formation. Proliferative responses were implied by the hyperplasia and the common finding of clusters of two or three adjacent oligodendrocytes at sites of acute myelin damage. This was borne out by studies using the PCNA antibody which gave negative reactions in normal brain but positive reactions in acute demyelination. Double staining for PCNA and cell markers showed that cells that had entered the cell proliferation cycle were to be found among astrocytes, microglia/macrophages and oligodendrocytes. In chronic demyelinating conditions, numbers of oligodendrocytes were reduced and cells in the proliferative cycle were not present, suggesting that the reactive potential of oligodendrocytes or their precursors and their capacity to respond to demyelination is limited.

Immunocytochemical and ultrastructural characterization of type 1 astrocytes and 0-2A lineage cells in long-term co-cultures

We examined cultures of purified type 1 astrocytes and mixed glial co-cultures containing type 1 astrocytes and 0-2A lineage cells in media containing fetal calf serum at 5 days in vitro (DIV), 12 DIV, and 30 DIV, using cell-specific immunocytochemical markers and electron microscopy. At all three time points and in both culture systems, the polygonal-shaped type 1 astrocytes were A2B5-, GFAP+, and GalC-(specific markers for 0-2A lineage cells, and mature astrocytes and oligodendrocytes, respectively). From 5 to 30 DIV, the type 1 astrocytes increased markedly in size and the appearance of the cytoskeleton changed dramatically, with the amount of glial filaments increasing and microtubules decreasing. At 5, 12, and 30 DIV, the 0-2A lineage cells were multipolar, A2B5 +, HNK-1 +, GFAP-, and GalC-. The 0-2 lineage cells could not be distinguished as either astrocytes or oligodendrocytes on the basis of immunocytochemical or ultrastructural characteristics. These cells had dense cytoplasm, very few intermediate filaments, and a large number of vacuoles and dense bodies. The general characteristics of the cultured astrocytes at 12 DIV and 30 DIV were similar to mature and aged astrocytes in vivo, respectively. These findings suggest that the culture environment in this study accelerated aging of type 1 astrocytes. 0-2A lineage cells, on the other hand, appeared unable to differentiate into either type 2 astrocytes or oligodendrocytes when cultured in the presence of both type 1 astrocytes and fetal calf serum.

Antigenic compartmentation in the mouse cerebellar cortex: zebrin and HNK-1 reveal a complex, overlapping molecular topography

Two monoclonal antibodies--anti-zebrin I and anti-HNK-1--have been used to study the compartmentation of the mouse cerebellar cortex. As in other species, the pattern of localization of the Purkinje cell specific antigen zebrin I is confined to a subset of Purkinje cells that are organized into parasagittal bands. The basic pattern consists of two abutting paramedian bands (P1+) and up to three additional vermal bands on either side (P2(+)-P4+). This pattern is altered in the vermal regions of lobules X and VI-VII where all Purkinje cells are immunoreactive. In the hemisphere there are three additional bands present (P5(+)-P7+) plus two shorter bands in the paravermal area (P4b+ and P5a+) that extend from the paramedian lobule through the lobulus simplex. This pattern is very similar, but perhaps not identical, to that previously described for the rat. These results suggest a common mammalian plan for the expression and localization of zebrin I. By using a monoclonal antibody to an epitope associated with HNK-1, we have now identified a novel pattern of compartmentation in mouse cerebellum. The HNK-1 epitope is expressed most notably on Purkinje cells and Golgi cells. The molecular layer immunoreactivity associated with the Purkinje cell dendrites varies in intensity in a systematic and reproducible fashion. This reveals a novel cerebellar compartmentation that is sometimes complementary, sometimes overlapping, to that revealed by anti-zebrin. As a result, it is now possible to subdivide the cerebellar cortex into a still finer mosaic of antigenic patches and bands than was possible by using zebrins alone.

Cellular and subcellular distribution of HNK-1 immunoreactivity in the neural tube of Xenopus

The HNK-1 antigen, a carbohydrate moiety bound to many cell adhesion and recognition molecules, is implicated in cell-cell and cell-substrate interactions during neural development. HNK-1 immunoreactivity (HNK1-IR) appears on neurons of the Xenopus neural tube very early in their development (Nordlander, Devel. Brain Res., 50:147-153, 1989). The distribution and onset of expression of the HNK-1 epitope on and within individual neurons is examined in this study. HNK-1 labels developing neurons and their processes, and focal areas of other structures which are directly contacted by neurons, such as neuroepithelial cell surfaces, basal lamina, and culture surfaces. HNK1-IR first appears in the Golgi apparatus and subsequently on the cell surface and in streams of punctate material directed toward the site of axon initiation and into the developing axon and its growth cone. The entire neuron is coated with a thin (20-30 nm) surface layer of HNK1-IR. In addition, the surface is dotted with small (100-250 nm) boluses of HNK1-IR material. Such boluses also occur within cytoplasmic vesicles, and extracellularly on basal lamina and culture substrata in proximity to neurons or their processes. The subcellar distribution of HNK1-IR in this tissue is compatible with a role for the HNK-1 epitope in axonal outgrowth and guidance.

In vivo CNS remyelination: HNK-1 labels newly differentiated oligodendrocytes but not precursors

The possibility that HNK-1 antibody might identify oligodendrocyte precursors in vivo was investigated using a combined immunocytochemical and ultrastructural analysis of remyelination in the cat optic nerve after demyelination induced by local injection of antiserum against galactocerebroside. HNK-1 antibody, in addition to antisera to galactocerebroside, glial fibrillary acidic protein, vimentin and myelin basic protein, was applied to early and late premyelinative lesions within which we have recently identified a putative precursor for the remyelinating oligodendrocyte termed the small glial cell. HNK-1 labelled oligodendrocytes in normal optic nerve and newly differentiated oligodendrocytes within lesions but did not label the small glial cells.

Perineuronal satellitosis in the human hippocampal formation

A previously unreported example of perineuronal satellitosis in the medial CA1 and adjacent subiculum in the human hippocampal formation is described. This phenomenon is characterized by a clustering of glial cells in relation to the perikarya of a subpopulation of neurons in the deep pyramidal layer and around most neurons scattered in the stratum oriens and subcortical white matter. Most of the perineuronal satellite glia were identified as oligodendrocytes based on their nuclear chromatin patterns and antigenic properties. Satellite oligodendrocytes were mostly of the medium dense variety. A type of satellite glia with nuclear features of the dark oligodendrocyte could not be identified unequivocally using the antigenic criteria employed in this study.

Bi-modal differentiation pattern in a new human neuroblastoma cell line in vitro

We have isolated a human neuroblastoma (NB) cell line, HTLA230, from the bone-marrow aspirate of a patient with stage-IV disease. Subcutaneous tumors after inoculation of HTLA230 cells into nude mice were composed of primitive neuroblasts which rarely contained neuro-secretory granules. Cytogenetic studies of the cell line demonstrated 2 distinct populations of cells with common chromosomal markers. Stable sub-clones with a differentiated or undifferentiated cell morphology were isolated, demonstrating phenotypical heterogeneity of the HTLA230 parental cell line. Treatment with retinoic acid (RA) induced extensive neurite outgrowth in the parental cell line and in phenotypically differentiated sub-clones, but rarely in undifferentiated ones. Long-term treatment with RA was not associated with down-modulation of mycN-gene expression, which could be achieved only in cultures treated additionally with aphidicolin, a DNA-synthesis inhibitor, thus eliminating growing NB cells. A RA resistant subclone (CI-5) was isolated from parental HTLA230 cells grown at clonal cell density. Cells originally showed a homogeneously differentiated morphology; however, flat cells (F-cells) appeared with time and were subsequently separately propagated. Transdifferentiation of isolated F-cells into cells with neuron-like (N-cell) morphology was observed. Immunohistochemical analysis demonstrated that F-cells had lost the expression of neuronal markers, including HNK-I and A2B5, and expressed the intermediate filament, vimentin. Furthermore, F-cells showed high incorporation of [methyl-3H] thymidine (3H-TdR) by autoradiography but no mycN protein could be detected, although present in the parental cell line. These results then suggest that the isolated NB cell line and the RA-resistant variant line represent an excellent in vitro model with which the bi-modal differentiation pathway of NB can be analyzed on a molecular biological level.

Developmental expression of HNK-1-reactive antigens in rat cerebral cortex and molecular heterogeneity of sulfoglucuronylneolactotetraosylceramide in CNS versus PNS

Monoclonal antibody HNK-1 reacts with a carbohydrate epitope present in proteins, proteoglycans, and sulfoglucuronylglycolipids (SGGLs). On high-performance TLC plates, SGGLs of the CNS from several species migrated consistently slower than those from the PNS, a result indicating possible differences in the structures. The structural characteristics of the major SGGL, sulfoglucuronylneolactotetraosylceramide (SGGL-1), from CNS was compared with those of SGGL-1 from PNS. Although the composition, sequence, and linkages of the carbohydrate moiety of the SGGL-1 species were identical, SGGL-1 from CNS contained mainly short-chain fatty acids, 16:0, 18:0, and 18:1, amounting to 85% of the total fatty acids, whereas SGGL-1 from PNS contained large proportions (59%) of long-chain fatty acids (greater than 18:0). These differences in the fatty acid composition accounted for the different migration pattern observed. The developmental expression of SGGLs and HNK-1-reactive proteins was studied in rat cerebral cortex between embryonic day (ED) 15 to adulthood. SGGLs in the rat cortex were maximally expressed around ED 19 and almost completely disappeared by postnatal day (PD) 20. This expression was contrary to their increasing expression in the cerebellum and sciatic nerve with postnatal development. Six to eight protein bands with a molecular mass of greater than 160 kDa were HNK-1 reactive in the rat cerebral cortex at different ages. The major HNK-1 reactivity to the 160-kDa protein band seen in ED 19 to PD 10 cortex decreased and completely disappeared from the adult cortex, whereas several other proteins remained HNK-1 reactive even in the adult. Western blot analyses of the neural cell adhesion molecules (N-CAMs) during development of the rat cortex with a polyclonal anti-N-CAM antibody showed that the major HNK-1-reactive protein bands were not N-CAMs. Between PD 1 and 10, 190-200-kDa N-CAM was the major N-CAM, and between PD 15 to adulthood, 180-kDa N-CAM was the only N-CAM present in the rat cortex.

Developmental expression of HNK-1-reactive antigens in the rat cerebellum and localization of sulfoglucuronyl glycolipids in molecular layer and deep cerebellar nuclei

Monoclonal antibody HNK-1-reactive carbohydrate epitope is expressed on proteins, proteoglycans, and sulfoglucuronyl glycolipids (SGGLs). The developmental expression of these HNK-1-reactive antigens was studied in rat cerebellum. The expression of sulfoglucuronyl lacto-N-neotetraosylceramide (SGGL-1) was biphasic with an initial maximum at postnatal day one (PD 1), followed by a second rise in the level at PD 20. The level of sulfoglucuronyl lacto-N-norhexaosyl ceramide (SGGL-2) in cerebellum was low until PD 15 and then increased to a plateau at PD 20. The levels of SGGLs increased during postnatal development of the cerebellum, contrary to their diminishing expression in the cerebral cortex. The expression of HNK-1-reactive glycoproteins decreased with development of the rat cerebellum from PD 1. Several HNK-1-reactive glycoproteins with apparent molecular masses between 150 and 325 kDa were visualized between PD 1 and PD 10. However, beyond PD 10, only two HNK-1-reactive bands at 160 and 180 kDa remained. The latter appeared to be neural cell adhesion molecule, N-CAM-180. A diffuse HNK-1-reactive band seen at the top of polyacrylamide electrophoretic gels was due mostly to proteoglycans. This band increased in its reactivity to HNK-1 between PD 15 and PD 25 and then decreased in the adult cerebellum. The lipid antigens were shown by two complementary methodologies to be localized primarily in the molecular layer and deep cerebellar nuclei as opposed to the granular layer and white matter. A fixation procedure which eliminates HNK-1-reactive epitope on glycoproteins and proteoglycans, but does not affect glycolipids, allowed selective immunoreactivity in the molecular layer and deep cerebellar nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigenic staining patterns of human glioma cultures: primary cultures, long-term cultures and cell lines

The immunocytochemical staining patterns of cultured glioma cells were investigated. Fifty nine individual cases were stained at different in vitro ages for glial fibrillary acidic protein, fibronectin, galactocerebroside, HNK-1/Leu 7, A2B5, vimentin, factor VIII and A4. Histologically, the cases were composed of eight low-grade astrocytomas, 11 high-grade astrocytomas, four low-grade oligodendrogliomas, seven high-grade oligodendrogliomas and 29 glioblastomas. The 45 cases were analysed within the first 3 weeks of culture, many of them as primary cultures. In 11 cases stainings were performed repeatedly at intervals of up to 6 months. Glial fibrillary acidic protein staining was positive in most of the early cultures of astrocytomas (low and high grade) and glioblastomas; expression in more than 50% of the cells was found in 1 of 5 low-grade astrocytomas, 5 of 11 high-grade astrocytomas and 14 of 29 glioblastomas. Two of the high-grade astrocytomas were stained once more after 6 weeks in culture and were found to be only 1% positive for glial fibrillary acidic protein but strongly positive for fibronectin. The same was true for five of the glioblastoma cases. Two of these cases remained glial fibrillary acid protein positive and developed into stable permanent cell lines. Only one case started with 1% of glial fibrillary acidic protein positive cells and later developed into a 99% glial fibrillary acidic protein positive cell line. Neither HNK-1/Leu 7 expression nor A2B5 staining appeared to have a relationship to the glial fibrillary acidic protein staining. It was observed that glial fibrillary acidic protein and HNK-1/Leu 7 were both 100% in some cases but that later one of the two antigens disappeared but not the other. The amount of glial fibrillary acidic protein staining does not allow the prediction of A2B5 staining. The study shows that initiation of primary cultures on an extracellular matrix yields more glial fibrillary acidic protein positive cells in primary cultures than have been found in other studies. It is concluded that only a rigid standardization of culture conditions will ensure the validity of comparisons of in vitro data obtained in primary cultures.

Boundaries during normal and abnormal brain development: in vivo and in vitro studies of glia and glycoconjugates

This paper focuses on transient boundaries of glia and glycoconjugates during development of the mouse central nervous system (CNS). Lectin-bound glycoconjugates, glial fibrillary acidic protein, and the J1/tenascin glycoprotein are distributed coextensively within boundaries around developing substructural arrangements (e.g., developing nuclei, and at a finer level, somatosensory cortical "barrels" related to individual facial vibrissae) throughout the CNS during pattern formation events. Electron microscopy has shown that the J1/tenascin glycoprotein, for example, is present in immature astrocytes, on glial and neuronal plasma membranes, and within the pericellular space that could be extracellular matrix (ECM). The findings presented on the expression of this well-characterized ECM molecule suggest that previously described glial and glycoconjugate boundaries reported by our group are in part composed of specific recognition molecules. The J1/tenascin glycoprotein, a chondroitin sulfate-containing antigen termed the 473 proteoglycan, and the adhesion molecule on glia are expressed within discrete boundary regions and associated axonal pathways. There, they may sculpture fine aspects of functional cytoarchitectonic arrangements and help guide axons to specific targets. The expression and developmental regulation of glycoproteins such as J1/tenascin may thus be integral events during pattern formation and synaptogenesis in the CNS. The presence of abnormal glial arrangements and glycoconjugate boundaries in the cortices of the genetic mutant mouse reeler, and findings on plasticity of boundaries following various perturbations, suggest that boundary expression is controlled by both genetic and epigenetic factors. Some future directions for studying developmental boundaries, including use of cultured explants for in vitro "bioassays," are also discussed.

Establishment and characterization of multipotent neural cell lines using retrovirus vector-mediated oncogene transfer

Neural cell lines were produced by retroviral vector-mediated transduction of the avian myc oncogene. Target cells were mitotic progenitor cells of postnatal mouse olfactory bulb and cerebellum, and postnatal rat cerebral cortex. Infection of the first two areas, where neurogenesis and gliogenesis occur postnatally, produced multipotent clonal lines that exhibited phenotypes of both neuronal and glial cells, and one line with a stable neuronal phenotype. Infection of cerebral cortex, where gliogenesis, but not neurogenesis, occurs postnatally, generated mortal clones that exhibited cells of glial phenotype. These lines should prove valuable for both in vitro and in vivo studies aimed at understanding the control of cell fate and differentiation of neural progenitors.

Recurrent medulloepithelioma of the ciliary body. Immunohistochemical characteristics

A predominantly benign medulloepithelioma of the ciliary body was diagnosed in an 8-year-old girl and resected by iridocyclectomy. It recurred twice during 30 months. Highly malignant histopathologic features developed, and the eye finally perforated and had to be enucleated. No recurrence or metastases have subsequently developed. Histologically, the tumor was a nonteratoid medulloepithelioma consisting of elements resembling embryonic retina, nonpigmented ciliary epithelium, and neuroblasts, but had also areas of obvious glial and neuronal differentiation as judged by immunohistochemistry. The neuroepithelial tumor cells were positive for neuron-specific enolase, vimentin, and often for S-100 protein. The neuroblastic cells were generally positive for neuron-specific enolase and synaptophysin, but were intermixed with glia-like tumor cells positive for vimentin, glial fibrillary acidic protein, and S-100 protein. The results suggest that even a nonteratoid medulloepithelioma may be, unlike retinoblastoma, a truly multipotential tumor.

Detection of the L2/HNK-1 carbohydrate epitope on glycoproteins and acidic glycolipids of the insect Calliphora vicina

The same or a very similar carbohydrate determinant, as represented by some sulfated, glucuronic acid-containing glycosphingolipids of human peripheral nerve, occurs on several adhesion molecules in the mammalian nervous system. In the present study, the occurrence of this epitope on glycoproteins and glycolipids of the fly, Calliphora vicina, was investigated by Western blot analysis and thin-layer chromatogram immunostaining. Several monoclonal antibodies recognizing an epitope on various neural cell adhesion molecules, designated L2 (334, 336, 349, and 412); the monoclonal antibody HNK-1 (recognizing an epitope on human natural killer cells); and a human IgM M-protein were found to react by Western blot analysis with various glycoproteins from larval and adult brains, although the intensity of staining of bands recognized by each antibody varied. Acidic glycolipids from pupae were also recognized, but only by the L2 antibody 334 and IgM M-protein. After desulfation of the acidic glycolipid fraction, the immunostaining pattern remained the same, an observation suggesting that the L2/HNK-1 epitope on insect acidic glycolipids contains a nonsulfated, glucuronic acid moiety. These observations indicate that the L2/HNK-1 carbohydrate structure occurs not only in vertebrates but also in insects on both glycoproteins and glycolipids, a finding suggesting a high degree of phylogenetic stability of this functionally important carbohydrate.

Immunocytological localization of the major peripheral nervous system glycoprotein P0 and the L2/HNK-1 and L3 carbohydrate structures in developing and adult mouse sciatic nerve

Immunocytological localization of the major glycoprotein of peripheral myelin P0 and its associated carbohydrate structures L2/HNK-1 and L3 was performed at the light- and electron-microscopic levels in mouse sciatic nerves at several developmental stages and in adulthood. P0 was first expressed on Schwann cells at the time that Schwann cells associated with axons on a 1:1 basis. P0 remains expressed at all times of myelin formation and in compact myelin. After cessation of myelination P0 is no longer detectable in the uncompacted parts of myelin, i.e., Schmidt-Lanterman incisures, paranodal loops, and outer and inner mesaxons. P0 is not detectable on basement membranes, interstitial collagens, and non-myelin-forming Schwann cells. The associated carbohydrate epitope L2 does not follow the expression of P0 at any developmental or adult stage. Until 21 days the L2 epitope is confined to nonmyelinated fibers. In sciatic nerves of mice older than 8 weeks, however, only a few nonmyelinated fibers remain L2-positive. L2 immunoreactivity is clearly seen in a subpopulation of compact myelin figures largely associated with motor fibers. The L3 epitope is never detectable on nonmyelinated fibers and becomes first visible when compact myelin is discerned. Unlike the L2 epitope L3 is present in most, if not all, compact myelin figures. These observations suggest that P0 may be involved in ensheathment of axons by Schwann cells at the decisive stages of initiation of myelination and later on, possibly in conjunction with the L3 carbohydrate structure, in maintenance of compact myelin. The appearance of the L2 carbohydrate epitopes in compact myelin of largely motor and fewer sensory nerve fibers at times when morphogenesis of myelin has ceased remains to be elucidated in functional terms.

Sulfoglucuronyl neolactoglycolipids in adult cerebellum: specific absence in murine mutants with Purkinje cell abnormality

It is shown here that glycolipids of the sulfoglucuronyl neolacto series (SGGLs) are present in the adult rodent cerebellum. SGGLs were not detected in the cerebellar murine mutants lurcher, Purkinje cell degeneration, and staggerer, in which Purkinje cell loss is the primary defect. SGGLs were present, however, in normal amounts in weaver and reeler mutants, in which there is a major and relatively specific loss of granule cells without obvious deficiency in Purkinje cells. In the myelin-deficient quaking mutant, the expression of SGGLs also was nearly normal. The loss of SGGLs in Purkinje cell-deficient mutants was specific, since most of the major lipids were not affected significantly and only the percentage composition of other lipids, such as sulfatides and gangliosides, was altered in the mutants. These and other results strongly suggest that SGGLs and other glycolipids of the paragloboside family are localized specifically in Purkinje cells and their arbors in the adult cerebellum. This is the first demonstration of the localization of a specific glycolipid and its analogs in a specific cell type in the nervous system.

Distribution of glucuronic acid-and-sulfate-containing glycoproteins in the central nervous system of the adult mouse

The distribution of glucuronic acid-and-sulfate-containing carbohydrate (GSC) epitope recognized by two monoclonal antibodies, HNK-1 and 4F4, was studied by immunocytochemistry in adult mouse brain. Both antibodies recognized proteins ranging in molecular weight from 60 to above 250 kDa in Western blot but no glycolipid was recognized in the adult brain. With both light and electron microscopic study, two patterns of staining are observed: diffuse neuropil staining, and individual neuronal somata staining. The diffuse neuropil staining is concentrated in discrete anatomically defined areas. At the EM level, this immunoreactivity is associated with numerous dendrites or astrocytic processes. At cell somata, most of neurons are stained only at Golgi apparatus (type 2); however, a distinct population of cells showed membranous staining (type 1) as well. Type 1 membranous immunoreactivity is observed only in membrane adjacent to astrocytic processes. In the cerebral cortex, type 1 neurons are found in layers III and V-VIa of somatosensory cortex, but only in layers V-VIa in most other cortical fields. Other areas containing type 1 neurons include the globus pallidus, the thalamic reticular nucleus, the hippocampus, the deep cerebellar nuclei, and a majority of the primary sensory and motor nuclei in the brainstem. The subpopulation of type 1 neurons show an overlap in distribution and morphology with some GABA-containing cells.

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.

Integrin, the cell surface receptor for fibronectin and laminin, expresses the L2/HNK-1 and L3 carbohydrate structures shared by adhesion molecules

On the basis of recent evidence that the carbohydrate structures designated L2/HNK-1 and L3 are shared by several neural adhesion molecules including L1, N-CAM, the myelin-associated glycoprotein and J1, we have suggested that other members of the L2/HNK-1 and L3 families are adhesion molecules. Here we show by Western blot analysis that integrin, the cell surface receptor for the extracellular matrix constituents fibronectin and laminin in chicken, also expresses the L2/HNK-1 and L3 epitopes and thus is another family member proven to be involved in adhesion.

Monoclonal antibody detects carbohydrate microheterogeneity on the murine cell adhesion molecule L1

The cell surface glycoprotein L1 is involved in neural cell interactions and shares with other adhesion molecules, i.e. the neural cell adhesion molecule N-CAM, the myelin-associated glycoprotein MAG and the J1 glycoproteins, an unusual carbohydrate structure designated L2/HNK-1. Recent evidence suggests that the L2/HNK-1 carbohydrate participates in adhesion. Since indirect evidence indicated that the L2/HNK-1 carbohydrate is not present on all molecules within a particular species of glycoproteins, it seemed pertinent to investigate this more directly by sequential immunoprecipitations. Here we show that the L2/HNK-1 epitope appears to be present on 35% of the L1 glycoproteins isolated from mouse brain. The epitope is restricted to the proteolytic fragment of L1 at the aminoterminal, extracellular domain in that it is detectable on L1-200 and L1-140, but absent from L1-80 and L1-50.

Myelin-associated glycoprotein, a member of the L2/HNK-1 family of neural cell adhesion molecules, is involved in neuron-oligodendrocyte and oligodendrocyte-oligodendrocyte interaction

A monoclonal antibody to the myelin-associated glycoprotein (MAG) was prepared and characterized to probe for the involvement of MAG in cell surface interactions among neural cells in vitro. The antibody reacts specifically with oligodendrocyte cell surface and myelin-rich brain regions as expected from previous investigations. Not all O4 antigen-positive oligodendrocytes express MAG in vitro. Fab fragments of the antibody interfere with neuron to oligodendrocyte and oligodendrocyte to oligodendrocyte adhesion, but not with oligodendrocyte to astrocyte adhesion. MAG-containing liposomes bind to the cell surfaces of the appropriate target cells by a mechanism that is specifically inhibitable by Fab fragments of monoclonal MAG antibodies, demonstrating that MAG is a neural cell adhesion molecule.

Localization of the L2 monoclonal antibody binding site on chicken neural cell adhesion molecule (NCAM) and evidence for its role in NCAM-mediated cell adhesion

Recent studies have described the localization of functional and structural domains on the neural cell adhesion molecule NCAM. In the present study we have extended these observations to examine the location of the carbohydrate epitope recognized by the L2 monoclonal antibody. This carbohydrate moiety is localized to the 65,000-dalton amino-terminal fragment of NCAM (previously designated Fr1), but is not present in the amino-terminal 25,000-dalton region of NCAM that contains the heparin-binding domain. We have also examined the role of this domain in NCAM-mediated cell adhesion, and have shown that incubation of an NCAM substratum with L2 monoclonal antibody inhibits cell attachment to this substratum. These data therefore suggest that the carbohydrate moiety recognized by L2 monoclonal antibody may be involved in the modulation of NCAM-mediated cell adhesion.

Immunoelectron microscopic localization of the neural cell adhesion molecules L1 and N-CAM during postnatal development of the mouse cerebellum

The cellular and subcellular localization of the neural cell adhesion molecules L1 and N-CAM was studied by pre- and postembedding immunoelectron microscopic labeling procedures in the developing mouse cerebellar cortex. The salient features of the study are: L1 displays a previously unrecognized restricted expression by particular neuronal cell types (i.e., it is expressed by granule cells but not by stellate and basket cells) and by particular subcellular compartments (i.e., it is expressed on axons but not on dendrites or cell bodies of Purkinje cells). L1 is always expressed on fasciculating axons and on postmitotic, premigratory, and migrating granule cells at sites of neuron-neuron contact, but never at contact sites between neuron and glia, thus strengthening the view that L1 is not involved in granule cell migration as a neuron-glia adhesion molecule. While N-CAM antibodies reacting with the three major components of N-CAM (180, 140, and 120 kD) show a rather uniform labeling of all cell types, antibodies to the 180-kD component (N-CAM180) stain only the postmigratory granule cell bodies supporting the notion that N-CAM180, the N-CAM component with the longest cytoplasmic domain, is not expressed before stable cell contacts are formed. Furthermore, N-CAM180 is only transiently expressed on Purkinje cell dendrites. N-CAM is present in synapses on both pre- and post-synaptic membranes. L1 is expressed only preterminally and not in the subsynaptic membranes. These observations indicate an exquisite degree of fine tuning in adhesion molecule expression during neural development and suggest a rich combinatorial repertoire in the specification of cell surface contacts.

The novel carbohydrate epitope L3 is shared by some neural cell adhesion molecules

The monoclonal L3 antibody reacts with an N-glycosidically linked carbohydrate structure on at least nine glycoproteins of adult mouse brain. Three out of the L3 epitope-carrying glycoproteins could be identified as the neural cell adhesion molecules L1 and myelin-associated glycoprotein, and the novel adhesion molecule on glia. Expression of the L3 carbohydrate epitope is regulated independently of the protein backbone of these three glycoproteins. Based on the observation that out of three functionally characterized L3 epitope-carrying glycoproteins three fulfill the operational definition of an adhesion molecule, we would like to suggest that they form a new family of adhesion molecules that is distinct from the L2/HNK-1 carbohydrate epitope family of neural cell adhesion molecules. Interestingly, some members in each family appear to be unique to one family while other members belong to the two families.

Sulfated glucuronic acid-containing glycoconjugates are temporally and spatially regulated antigens in the developing mammalian nervous system

Monoclonal antibody 4F4, which was raised against a cell suspension of embryonic rat forebrain, reacts with acidic glycolipids and several high-molecular-weight glycoproteins in rodent brain. The major reactive glycolipid is maximally expressed at Embryonic Day 15 (E15) and is no longer detectable at Postnatal Day 14 (P14) in the rat. 4F4 antibody reacts with a glucuronic acid- and sulfate-containing lipid isolated from human sciatic nerve as well as with lipids from mouse and rat embryonic brain tissue. Although the glycolipid disappears postnatally, the immunoreactive glycoproteins continue to be expressed in brain until adulthood. Both sciatic nerve and embryonic brain glycolipids are hydrolyzed by glucuronidase/sulfatase treatment but are insensitive to all other glycosidases tested. In addition, the observed 4F4 reactivity with extracted glycolipids, glycoproteins, and tissue sections of embryonic brain is identical to the reactivity demonstrated by HNK-1 antibodies. Immunocytochemical studies in developing brain showed stage-specific distribution of this carbohydrate antigen. At E10 in the mouse, immunoreactivity is associated with the mantle layer of the neural tube. At E15 in the cortex, the most intense staining is associated with the molecular layer and the subplate, and weaker staining is seen in the intermediate zone and cortical plate, suggesting that the antigen is highly concentrated on postmigratory cells in the embryonic nervous system.

Expression of the HNK-1 carbohydrate epitope in human retina and retinoblastoma. An immunohistochemical study with the anti-Leu-7 monoclonal antibody

Fifty formalin-fixed and paraffin-embedded retinoblastoma specimens and five normal human eyes were studied with the monoclonal anti-Leu-7 antibody, directed against the HNK-1 carbohydrate epitope that is shared by human natural killer cells and many neuronal, glial and neuroectodermal cells. The laboratory method was a sensitive immunohistochemical staining procedure, and neuroectodermal tumours that usually express this epitope were used as positive controls. In the human retina, Müller cell membranes were positively stained, but additional staining of neuronal cells was not excluded at the light microscopical level. A positive cytoplasmic reaction was also seen in ciliary and retinal pigment epithelial cells. All but one intraocular retinoblastomata studied contained cells staining positively for the HNK-1 epitope, but these cells were probably not neoplastic. Although positive reaction has previously been reported in three retinoblastomata, the present results suggest that positive cells are derived from entrapped and infiltrated retina. Staining of adjacent sections against leukocyte common antigen suggested that the positively staining cells were not natural killer cells.

Production and characterization of monoclonal antibodies against myelin-associated glycoprotein

Monoclonal antibodies against myelin-associated glycoprotein were generated by fusing mouse myeloma cells with spleen lymphocytes from BALB/c mice immunized with human myelin-associated glycoprotein purified from CNS myelin. Three groups of antibodies were identified: IgG antibodies recognizing the polypeptide moiety and IgG and IgM antibodies recognizing the carbohydrate moiety of the intact molecule. Properties of these antibodies were examined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the immunostaining technique using human CNS and peripheral nerve myelin, and ganglioside fractions isolated from human brain and peripheral nerve, and with immunohistochemical staining of human peripheral nerves. Part of human peripheral blood mononuclear cells was stained with the antibodies against the carbohydrate moiety, but not with IgG antibodies recognizing the polypeptide moiety. Natural killer activity was partially reduced after treatment of human peripheral blood lymphocytes with an IgM antibody and complement in vitro. The possibility that anti-myelin-associated glycoprotein antibodies might play a role in the pathogenesis of demyelinating diseases through modification of natural killer activity is discussed.

Demonstration of glucuronic acid on brain glycoproteins which react with HNK-1 antibody

Ependymins, a family of extracellular glycoproteins of goldfish and mammalian brain, were shown to contain N-linked complex glycan chains. These glycoproteins reacted with a monoclonal antibody, HNK-1 which recognizes a membrane antigen on a subset of human lymphocytes, myelin-associated glycoprotein glycoprotein epitope reacting with HNK-1 antibody was previously shown to include a terminal 3-sulfoglucuronosyl residue present in certain glycolipids of the nervous tissue (Chou et al., Biochem. Biophys. Res. Commun. 1985, 128, 383-388). In this report, the presence of glucuronic acid in ependymins was demonstrated by gas-liquid chromatography and mass spectrometry. We suggest that a 3-sulfoglucuronosyl residue may be the common epitope on HNK-1-reactive glycoproteins.

Molecular specialization of astrocyte processes at nodes of Ranvier in rat optic nerve

The HNK-1 and L2 monoclonal antibodies are thought to recognize identical or closely associated carbohydrate epitopes on a family of neural plasma membrane glycoproteins, including myelin-associated glycoprotein, the neural cell adhesion molecule, and the L1 and J1 glycoproteins, all of which have been postulated to play a part in mediating cell-cell interactions in the nervous system. We have used these two antibodies in immunofluorescence and immunogold-electron microscopic studies of semithin and ultrathin frozen sections of adult rat optic nerve, respectively, and we show that they bind mainly to astrocyte processes around nodes of Ranvier. Most other elements of the nerve, including astrocyte cell bodies and large astrocytic processes, are not labeled by the antibodies. To our knowledge, this is the first demonstration that perinodal astrocyte processes are biochemically specialized. We provide evidence that one of the HNK-1+/L2+ molecules concentrated around perinodal astrocyte processes is the J1 glycoprotein; our findings, taken together with previously reported observations, suggest that the other known HNK-1+/L2+ molecules are not concentrated on these processes. Since anti-J1 antibodies previously have been shown to inhibit neuron to astrocyte adhesion in vitro, we hypothesize that J1 may play an important part in the axon-glial interactions that presumably are involved in the assembly and/or maintenance of nodes of Ranvier.

Immunocytological localization of cell adhesion molecules L1 and N-CAM and the shared carbohydrate epitope L2 during development of the mouse neocortex

The expression of the two adhesion molecules L1 and N-CAM and their shared carbohydrate epitope recognized by monoclonal antibody L2, was studied during development of the embryonic mouse neocortex by immunohistology at light- and electron-microscopic levels between embryonic days 9 and 18. Throughout this time period N-CAM is expressed in all layers of the telencephalic anlage. L1 antigen shows a more restricted expression than N-CAM. It is not detectable at day 9. From day 10 onward it is expressed on young neurons in the marginal zone, but not in the ventricular layer. At embryonic day 13 L1 antigen appears also in the intermediate zone on afferent fibers from subcortical structures and on migrating neurons. Neuronal cell bodies in the cortical plate and subplate express L1 antigen only transiently on embryonic days 13-16. These observations suggest that L1 antigen does not play a prominent role in the initiation of neuronal migration in the ventricular zone, but could be functional during later stages of migration and in the aggregation of neuronal cell bodies at their final position in the cortical plate. The L2 epitope also shows a more restricted expression than N-CAM during the time period studied. Similar to L1 antigen, it first appears at embryonic day 10 in the marginal zone and remains undetectable in the ventricular layer also at later stages. In the marginal zone the L2 epitope is strongly expressed on neuroepithelial endfeet at the basal lamina. The basal lamina itself is L2 epitope-negative. From embryonic day 10 onward the L2 epitope is most strongly expressed in the marginal zone and subplate and more weakly in the cortical plate and intermediate zone. In the subplate it is not only associated with the surface membrane, but also with the extracellular matrix. These observations support previous biochemical data which show that the L2 epitope is not present on all N-CAM molecules of the embryonic or adult forms and suggest that the independent regulation or L2 epitope expression may have functional implications during development.

Neuronal influence on antigenic marker profile, cell shape and proliferation of cultured astrocytes obtained by microdissection of distinct layers from the early postnatal mouse cerebellum

To study the cellular heterogeneity of astrocytes from early postnatal mouse cerebellum in culture, Bergmann glia were enriched by hand-dissection of Purkinje, molecular and external granular layers ('outer' layer) and fibrous astrocytes of white matter and deep cerebellar nuclei ('inner' layer). Both populations of GFA protein and vimentin-positive astrocytes express N-CAM and the L2/HNK-1 epitope, but not tetanus toxin receptors or A2B5 antigen, at levels detectable by indirect immunofluorescence procedures. The two astrocyte populations are thus indistinguishable from each other. Expression of tetanus toxin receptors and A2B5 antigen in these astrocytes can, however, be induced by removal of neurons. The expression of tetanus toxin receptors is again reduced by readdition of purified populations of small cerebellar neurons. Morphology and proliferation of astrocytes from both layers is also dependent on the presence of neurons: removal of neurons leads to an epithelioid, rather than star-shaped morphology and a severalfold increase in proliferation. Readdition of neurons induces astrocytes to return to their star-shaped morphology. Epidermal growth factor increases proliferation in both populations of astrocytes. We conclude that neither antigenic marker profile, morphology nor proliferative responses serve to distinguish between enriched Bergmann glia and enriched fibrous astrocytes.

Differential inhibition of neurone-neurone, neurone-astrocyte and astrocyte-astrocyte adhesion by L1, L2 and N-CAM antibodies

The cell adhesion molecules L1, N-CAM and Ng-CAM have been implicated in cell-cell interactions among developing neural cells. L1 and N-CAM are structurally and functionally distinct molecular entities and act synergistically in mediating Ca2+-independent adhesion between re-aggregating early postnatal cerebellar cells. N-CAM has been reported to be neurone-specific in the chicken and to mediate fasciculation of neurites and of nerve-muscle interactions. L1, which in the central nervous system has been found only on post-mitotic neurones, mediates migration of granule cell neurones in the mouse cerebellar cortex. In view of the molecules' distinct effects on cell interactions, we wondered whether different neural cell types are involved in the actions of each molecule. Here we report that L1 antigen promotes neurone-neurone adhesion. N-CAM, which is expressed on both neurones and glia, mediates neurone-neurone, neurone-astrocyte and astrocyte-astrocyte adhesion. The L2 carbohydrate epitope shared between the two adhesion molecules seems to be involved in neurone-astrocyte and astrocyte-astrocyte adhesion and acts in a more than additive manner in N-CAM-mediated neurone-neurone adhesion.