Serum antibodies to heparan sulfate glycosaminoglycans in Guillain-Barré syndrome and other demyelinating polyneuropathies

We tested for serum antibodies to glycosaminoglycans (GAGs), including heparan sulfate, in patients with Guillain-Barré syndrome (GBS) and other disorders. We used ELISA methods that optimize immunoglobulin binding to carbohydrate antigens to measure serum antibodies to heparan sulfate GAGs in GBS, and control neuromuscular and immune disorders. We found serum IgM or IgG antibodies to heparan sulfate GAGs in 34% of patients with GBS. Serum IgM binding to heparan sulfate GAGs was also found in some chronic demyelinating polyneuropathies, with the highest frequency (33%) in patients with IgM anti-MAG M-proteins. Antibodies to heparan sulfate GAGs were rare (1%) in control serums from patients with other disorders. This result is the first demonstration of high titer serum antibodies to a specific antigen in a substantial group of, and with some specificity for, patients with the classically described GBS syndrome of acute-onset, motor-sensory polyneuropathy with demyelinating features.

Novel pluripotential neural progenitor lines exhibiting rapid controlled differentiation to neurotransmitter receptor-expressing neurons and glia

The immortalization of progenitor cells from embryonic murine hippocampus using oncogene-carrying retroviral vectors is described. Use of a vector encoding the oncogene v-myc results in lines of nestin-positive progenitor cells. Limited differentiation ensues if the cells are cultured in the presence of dibutyryl cyclic adenosine monophosphate. In contrast, use of a vector in which the extracellular portion of the epidermal growth factor (EGF) receptor is fused to the neu tyrosine kinase generates lines of pluripotential nestin-positive progenitor cells, which differentiate upon withdrawal of EGF into neurons and glia. Differentiated neurons expressing action potentials and neurotransmitter receptors make up a high proportion of the cells. These cell lines are useful tools to investigate the characteristics of differentiating neurons and glia, as well as to screen neuroactive drugs. This work has been reported in preliminary form as an abstract (1996 Society for Neuroscience Abstract, #606.20, p. 1537).

Thymic carcinoids in multiple endocrine neoplasia type 1

OBJECTIVE

To study the clinical, pathologic, and genetic features of thymic carcinoids in the setting of multiple endocrine neoplasia type 1 (MEN1) and to study means for detection and prevention of this tumor in patients with MEN1.

SUMMARY BACKGROUND DATA

Thymic carcinoid is a rare malignancy, with approximately 150 cases reported to date. It may be associated with MEN1 and carries a poor prognosis, with no effective treatment. Its underlying etiology is unknown.

METHODS

Ten patients with MEN1 from eight families with anterior mediastinal tumors were included in a case series study at tertiary referring hospitals. Clinicopathologic studies were done on these patients, with a review of the literature. Mutation analysis was performed on the MEN1 gene in families with clusterings of the tumor to look for genotype-phenotype correlation. Loss of heterozygosity was studied in seven cases to look for genetic abnormalities.

RESULTS

Histologic studies of all tumors were consistent with the diagnosis of thymic carcinoid. Clustering of this tumor was found in some of the families-three pairs of brothers and three families with first- or second-degree relatives who had thymic carcinoid. All patients described here were men, with a mean age at detection of 44 years (range 31 to 66). Most of the patients had chest pain or were asymptomatic; none had Cushing's or carcinoid syndrome. All tumors were detected by computed tomography (CT) or magnetic resonance imaging (MRI) of the chest. The results of octreoscans performed in three patients were all positive. Histopathologic studies were consistent with the diagnosis of thymic carcinoid and did not stain for ACTH. Mutation analysis of the families with clustering revealed mutations in different exons/introns of the MEN1 gene. Loss of heterozygosity (LOH) studies of seven tumors did not show LOH in the MEN1 region, but two tumors showed LOH in the 1p region.

CONCLUSIONS

MEN1-related thymic carcinoids constitute approximately 25% of all cases of thymic carcinoids. In patients with MEN1, this is an insidious tumor not associated with Cushing's or carcinoid syndrome. Local invasion, recurrence, and distant metastasis are common, with no known effective treatment. We propose that CT or MRI of the chest, as well as octreoscanning, should be considered as part of clinical screening in patients with MEN1. We also propose performing prophylactic thymectomy during subtotal or total parathyroidectomy on patients with MEN1 to reduce the risks of thymic carcinoid and recurrence of hyperparathyroidism. Its male predominance, the absence of LOH in the MEN1 region, clustering in close relatives, and the presence of different MEN1 mutations in these families suggest the involvement of modifying genes in addition to the MEN1 gene. A putative tumor suppressor gene in 1p may be involved.

Transcripts for secreted and GPI-anchored brevican are differentially distributed in rat brain

Brevican is a member of the aggrecan/versican family of proteoglycans. In contrast to the other family members, brevican occurs both as soluble isoforms secreted into the extracellular space and membrane-bound isoforms which are anchored to the cell surface via a glycosylphosphatidylinositol (GPI) moiety. Expression of both variants, which are encoded by two differentially processed transcripts from the same gene, is confined to the nervous system. In the current study, we have used in situ hybridization to examine the cellular sites of synthesis for both mRNAs during postnatal development of the rat brain. Whereas the 3.6-kb transcript encoding secreted brevican displays a widespread distribution in grey matter structures, including cerebellar and cerebral cortex, hippocampus and thalamic nuclei with silver grains accumulating over neuronal cell bodies, the smaller transcript (3.3 kb) encoding GPI-anchored isoforms appears to be largely confined to white matter tracts and diffusely distributed glial cells. This expression pattern is further confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR) experiments with RNA from different glial cell cultures, and by biochemical data demonstrating that the crude membrane fraction from isolated optic nerve contains high amounts of phosphatidylinositol-specific phospholipase C (PI-PLC)-sensitive brevican immunoreactivity. During ontogenetic development, both brevican transcripts are generally up-regulated. However, the expression of glypiated brevican is delayed by about 1 week, compared with the expression of the secreted isoform. This late appearance of GPI-linked brevican, its predominant expression in glial cells and its tight association with brain myelin fractions suggest a functional role in neuroglia.

Isolation and characterization of an oligodendrocyte precursor-derived B-cell epitope in multiple sclerosis

In a search for possible central nervous system-specific autoantigens in multiple sclerosis (MS), a lambda-phage protein expression library was constructed from an oligodendrocyte-precursor cell line. The library was screened with pooled cerebrospinal fluid (CSF) from 54 patients with definite MS according to the criteria of Poser. Pooled CSF samples from 44 patients with other neurological diseases including bacterial meningitis and viral encephalitis were used as control. A total of 1,000,000 colonies were screened and 6 positive clones were detected. At the DNA level none of the sequences showed significant homology to a known coding sequence. All 6 clones contained an open reading frame for small peptides ranging from 14 to 38 amino acids. It was noteworthy that 5 clones contained a common sequence of 7 amino acids, which was highly homologous to a translated consensus Alu repeat epitope. Screening of sera and CSF from patients with MS showed that approximately 44% reacted with these so-called Alu peptides, end-point antibody titers in their sera ranging from 1:1,000 to 1:25,000. In addition, some samples selected by their reactivity with Alu peptides stained intensively the cytoplasm of oligodendrocyte precursors but not of astrocytes ex vivo. We postulate that autoantibodies to a hitherto unknown oligodendrocyte precursor-derived B-cell epitope could contribute to the pathogenesis in a subgroup of MS patients.

Lectin-binding properties of oligodendrocyte lineage cells aid in defining functionally important surface proteins

Oligodendrocytes are the myelin-forming cells of the central nervous system. They develop from migratory and proliferative precursor cells, which differentiate to mature myelinating cells. As a first step toward investigating the expression of cell surface glycoproteins by oligodendrocyte lineage cells, we tested 14 different lectins for their binding to oligodendrocyte lineage cells. Peanut agglutinin (PNA) was the only lectin used that showed a differentiation stage-dependent binding to oligodendrocytes. PNA-binding molecules are specifically expressed by oligodendrocyte precursor cells, downregulated with differentiation, and reexpressed by mature oligodendrocytes. It was additionally observed that PNA stimulates the proliferation of oligodendrocyte precursor cells. PNA may therefore be a useful tool for isolating and characterizing important cell surface glycoproteins expressed by oligodendrocyte lineage cells.