Multiple origins of the spinocerebellar ataxia 7 (SCA7) mutation revealed by linkage disequilibrium studies with closely flanking markers, including an intragenic polymorphism (G3145TG/A3145TG)

Spinocerebellar ataxia 7 (SCA7) is a neurodegenerative disease characterised by the association of cerebellar ataxia and, in most patients, progressive macular degeneration leading to loss of autonomy and blindness. The patients die after 5-30 years of evolution. The cause of the disease has been identified as a (CAG)n repeat expansion in the coding sequence of the SCA7 gene on chromosome 3p. De novo mutations occur on intermediate-sized alleles carrying from 28 to 35 CAG repeats. Neomutations explain the persistence of the disease in spite of the great instability of the repeat sequence which results in the appearance of juvenile onset patients and the extinction of the disease within families. This rare disorder has been reported in a wide variety of countries and ethnic groups. In a large number of SCA7 families (n = 41) of different origins, we have determined the haplotypes segregating with the mutation of several microsatellite markers close to the SCA7 gene and of a new intragenic polymorphism (G3145TG/A3145TG). Four different haplotypes were found for centromeric markers (G3145TG/A3145TG-D3S1287-D3S3635) in the majority of the kindreds from four different geographic regions: A-2-4 in Korea; A-3-6 in North Africa, B-3-6 in continental Europe and A-4-6 in the UK and USA. The haplotypes in the Jamaican, Filipino, Brazilian and German families were different, suggesting that independent regional founders are at the origin of the SCA7 mutation in each population. Two different haplotypes were observed, however, in two families from the same rural area in central Italy in which de novo SCA7 mutations on intermediate alleles have been observed, suggesting the existence of different pools of at-risk chromosomes in this population.

Expression pattern alterations of syndecans and glypican-1 in normal and pathological trophoblast

Syndecans (syn-1, -2, -3, -4) and glypican-1 are proteoglycans expressed during development in association with changes in tissue organization and differentiation. They participate in the modulation of growth factor actions and in cell-cell and cell-matrix adhesion. The expression of syn-1, -2, -3, -4, and glypican-1 has been studied in normal human placenta and in gestational trophoblastic disease such as hydatidiform mole, invasive mole, and choriocarcinoma, using immunohistochemistry and western blots. Syndecan-3 was not expressed in normal or pathological tissues. During normal gestation, the other proteoglycans showed a specific staining pattern, which for some was modified during pregnancy. For instance, syn-1 was only expressed in syncytiotrophoblast; syn-4 was mainly localized in the villous and extravillous cytotrophoblast in the first trimester, whereas at term it was expressed in the syncytiotrophoblast. The most striking results are the altered expression patterns of syndecans and glypican-1 in pathological tissues. These proteoglycans showed a progressive decrease of immunostaining related to the increase of severity of trophoblastic disease, in particular in invasive mole and choriocarcinoma. In addition, dysregulation in the localization of the expression patterns was observed for syn-2 and -4. Because changes in syndecan expression enable cells to become more or less responsive to their micro-environment, the down-regulation and/or dysregulation of syndecans in relation to the degree of severity of trophoblastic diseases provides new insights into the progression of these pathologies.

Structural basis of glycosaminoglycan modification and of heterotypic interactions of perlecan domain V

The C-terminal perlecan domain V of about 90 kDa consists of laminin-type G domain modules (LG) (25 kDa) and epidermal growth factor-like modules (EG) (4 kDa) in the tandem arrangement LG1-EG1-EG2-LG2-EG3-EG4-LG3. Several shorter fragments have been prepared by recombinant production in mammalian cells and used to map the single glycosaminoglycan (GAG) substitution site and the binding of several carbohydrate and protein ligands. This identified a Ser3511 residue located in a short link region between EG4 and LG3 as being involved in GAG attachment. Electron microscopy provided evidence that the same substitution exists in tissue forms of perlecan. Heparan sulphate attached to this site was shown to bind to the alpha1LG4 module of laminin-1, indicating a role in basement membrane assembly and cell-matrix interactions. This site is also close to an Asn-Asp bond which is readily cleaved by an endogenous protease that depends on the presence of Asp and the LG2 module. A weak heparin binding site was shown to include the EG2 module, which contains five basic residues. Binding to sulphatides and the alpha-dystroglycan receptor was much stronger and required at least two LG modules. However, single LG modules appear to be sufficient for the interaction with the laminin-nidogen complex, while EG3-4 and some flanking regions are apparently involved in fibulin-2 binding. These observations indicate that a complex modular structure is required for domain V in order to provide a rich repertoire of potential biological functions.

Expression of proteoglycan core proteins in human bone marrow stroma

Heparan sulphate proteoglycans (HSPGs) present on the surface of bone marrow stromal cells and in the extracellular matrix (ECM) have important roles in the control of adhesion and growth of haemopoietic stem and progenitor cells. The two main groups of proteoglycans which contain heparan sulphate chains are members of the syndecan and glypican families. In this study we have identified the main surface membrane and matrix-associated HSPGs present in normal human bone marrow stroma formed in long-term culture. Proteoglycans were extracted from the adherent stromal layers and treated with heparitinase and chondroitinase ABC. The core proteins were detected by Western blotting using antibodies directed against syndecans-1-4, glypican-1 and the ECM HSPG, perlecan. Stromal cell expression at the RNA level was detected by Northern blotting and by reverse transcription PCR. Glypican-1, syndecan-3 and syndecan-4 were the major cell-membrane HSPG species and perlecan was the major ECM proteoglycan. There was no evidence for expression of syndecan-1 protein. Syndecan-3 was expressed mainly as a variant or processed 50-55 kDa core protein and in lower amounts as the characteristic 125 kDa core protein. These results suggest that syndecan-3, syndecan-4 and glypican-1 present on the surface of marrow stromal cells, together with perlecan in the ECM, may be responsible for creating the correct stromal 'niche' for the maintenance and development of haemopoietic stem and progenitor cells. The detection of a variant form of syndecan-3 as a major stromal HSPG suggests a specific role for this syndecan in haemopoiesis.

Gerontological social work and the UN International Year of Older Persons. Interview by Stanley L. Witkin

To highlight the United Nations International Year of Older Persons and to increase awareness of social work issues related to older people, the editor of Social Work conducted an interview with four distinguished social workers involved in gerontological social work. The interviewees identified professional needs and various policy and practice issues for social work education and practice.

Heparin-binding protein targeted to mitochondrial compartments protects endothelial cells from apoptosis

Neutrophil-borne heparin-binding protein (HBP) is a multifunctional protein involved in the progression of inflammation. HBP is stored in neutrophil granules and released upon stimulation of the cells in proximity to endothelial cells. HBP affects endothelial cells in multiple ways; however, the molecular and cellular mechanisms underlying the interaction of HBP with these cells are unknown. Affinity isolation and enzymatic degradation demonstrated that HBP released from human neutrophils binds to endothelial cell-surface proteoglycans, such as syndecans and glypican. Flow cytometry indicated that a significant fraction of proteoglycan-bound HBP is taken up by the endothelial cells, and we used radiolabeled HBP to determine the internalization rate of surface-bound HBP. Confocal and electron microscopy revealed that internalized HBP is targeted to perinuclear compartments of endothelial cells, where it colocalizes with mitochondria. Western blotting of isolated mitochondria from HBP-treated endothelial cells showed that HBP is present in 2 forms - 28 and 22 kDa. Internalized HBP markedly reduced growth factor deprivation-induced caspase-3 activation and protected endothelial cells from apoptosis, suggesting that uptake and intracellular routing of exogenous HBP to mitochondria contributes to the sustained viability of endothelial cells in the context of locally activated neutrophils.

Glypican-6, a new member of the glypican family of cell surface heparan sulfate proteoglycans

The glypicans compose a family of glycosylphosphatidylinositol-anchored heparan sulfate proteoglycans. Mutations in dally, a gene encoding a Drosophila glypican, and in GPC3, the gene for human glypican-3, implicate glypicans in the control of cell growth and division. So far, five members of the glypican family have been identified in vertebrates. By sequencing expressed sequence tag clones and products of rapid amplifications of cDNA ends, we identified a sixth member of the glypican family. The glypican-6 mRNA encodes a protein of 555 amino acids that is most homologous to glypican-4 (identity of 63%). Expression of this protein in Namalwa cells shows a core protein of approximately 60 kDa that is substituted with heparan sulfate only. GPC6, the gene encoding human glypican-6, contains nine exons. Like GPC5, the gene encoding glypican-5, GPC6 maps to chromosome 13q32. Clustering of the GPC5/GPC6 genes on chromosome 13q32 is strongly reminiscent of the clustering of the GPC3/GPC4 genes on chromosome Xq26 and suggests GPCs arose from a series of gene and genome duplications. Based on similarities in sequence and gene organization, glypican-1, glypican-2, glypican-4, and glypican-6 appear to define a subfamily of glypicans, differing from the subfamily comprising so far glypican-3 and glypican-5. Northern blottings indicate that glypican-6 mRNA is widespread, with prominent expressions in human fetal kidney and adult ovary. In situ hybridization studies localize glypican-6 to mesenchymal tissues in the developing mouse embryo. High expressions occur in smooth muscle cells lining the aorta and other major blood vessels and in mesenchymal cells of the intestine, kidney, lung, tooth, and gonad. Growth factor signaling in these tissues might in part be regulated by the presence of glypican-6 on the cell surface.

Mitochondrial clearance of cytosolic Ca(2+) in stimulated lizard motor nerve terminals proceeds without progressive elevation of mitochondrial matrix [Ca(2+)]

This study used fluorescent indicator dyes to measure changes in cytosolic and mitochondrial [Ca(2+)] produced by physiological stimulation of lizard motor nerve terminals. During repetitive action potential discharge at 10-50 Hz, the increase in average cytosolic [Ca(2+)] reached plateau at levels that increased with increasing stimulus frequency. This stabilization of cytosolic [Ca(2+)] was caused mainly by mitochondrial Ca(2+) uptake, because drugs that depolarize mitochondria greatly increased the stimulation-induced elevation of cytosolic [Ca(2+)], whereas blockers of other Ca(2+) clearance routes had little effect. Surprisingly, during this sustained Ca(2+) uptake the free [Ca(2+)] in the mitochondrial matrix never exceeded a plateau level of approximately 1 microM, regardless of stimulation frequency or pattern. When stimulation ceased, matrix [Ca(2+)] decreased over a slow ( approximately 10 min) time course consisting of an initial plateau followed by a return to baseline. These measurements demonstrate that sustained mitochondrial Ca(2+) uptake is not invariably accompanied by progressive elevation of matrix free [Ca(2+)]. Both the plateau of matrix free [Ca(2+)] during stimulation and its complex decay after stimulation could be accounted for by a model incorporating reversible formation of an insoluble Ca salt. This mechanism allows mitochondria to sequester large amounts of Ca(2+) while maintaining matrix free [Ca(2+)] at levels sufficient to activate Ca(2+)-dependent mitochondrial dehydrogenases, but below levels that activate the permeability transition pore.

Resealing of transected myelinated mammalian axons in vivo: evidence for involvement of calpain

The mechanisms underlying resealing of transected myelinated rat dorsal root axons were investigated in vivo using an assay based on exclusion of a hydrophilic dye (Lucifer Yellow-biocytin conjugate). Smaller caliber axons (<5 microm outer diameter) resealed faster than larger axons. Resealing was Ca2+ dependent, requiring micromolar levels of extracellular [Ca2+] to proceed, and further accelerated in 1 mM Ca2+. Two hours after transection, 84% of axons had resealed in saline containing 2 mM Ca2+, 28% had resealed in saline containing no added Ca2+ and only 3% had resealed in the Ca2+ buffer BAPTA (3 mM). The enhancing effect of Ca2+ could be overcome by both non-specific cysteine protease inhibitors (e.g., leupeptin) and inhibitors specific for the calpain family of Ca2+ -activated proteases. Resealing in 2 mM Ca2+ was not inhibited by an inhibitor of phospholipase A2. Resealing in low [Ca2+] was not enhanced by agents which disrupt microtubules, but was enhanced by dimethylsulfoxide (0.5-5%). These results suggest that activation of endogenous calpain-like proteases by elevated intra-axonal [Ca2+] contributes importantly to membrane resealing in transected myelinated mammalian axons in vivo.

Inducible expression of the cell surface heparan sulfate proteoglycan syndecan-2 (fibroglycan) on human activated macrophages can regulate fibroblast growth factor action

Monocyte/macrophages play important roles in regulating tissue growth and angiogenesis through the controlled release of heparin-binding growth factors such as fibroblast growth factor (FGF), vascular endothelial growth factor, and heparin binding epidermal growth factor. The action of these potent growth mediators is known to be regulated by adsorption to heparan sulfate proteoglycans (HSPGs) on the surface and within the extracellular matrix of other neighboring cells, which respectively promote or restrict interactions with their signal-transducing receptors on target cells. Here we report on the nature of HSPGs inducibly expressed on the surface of macrophages that confer these cells with the capacity to regulate endogenous growth factor activity. We reveal that activated human macrophages express only a single major 48-kDa cell surface HSPG, syndecan-2 (fibroglycan) as the result of de novo RNA and protein synthesis. In addition, we demonstrate this macrophage HSPG selectively binds the macrophage-derived growth factors FGF-2, vascular endothelial growth factor and heparin binding EGF and can present FGF-2 in a form that transactivates receptor-bearing BaF32 cells. These results define a novel and unique proteoglycan profile for macrophages and imply a key role for syndecan-2 in the delivery of sequestered growth factors by inflammatory macrophages for productive binding to their appropriate target cells in vivo.

Molecular polymorphism of the syndecans. Identification of a hypo-glycanated murine syndecan-1 splice variant

We have identified a cDNA that encodes a variant form of murine syndecan-1. The variant cDNA lacks the sequence corresponding to the first 132 nucleotides of the third exon of the syndecan-1 gene. The corresponding message is rare. The alternative splice respects the reading frame and deletes 44 amino acids from the protein, joining the S45GS47GT sequence to a variant immediate downstream context. This sequence context initiates with alanine instead of glycine as residue 50, reducing the number of SGXG sequence motifs in the protein from two to one. Expression of this variant syndecan-1 in Madin-Darby canine kidney or MOLT-4 cells yielded a recombinant proteoglycan with a reduced number and clustering of the heparan sulfate chains. Both the conversions of Ala50 and of Lys53 into glycine enhanced the heparan sulfate substitution of the variant protein. These findings support the concept that serine-glycine dipeptide signals for glycosaminoglycan/heparan sulfate synthesis depend on sequence context (Zhang, L., David, G., and Esko, J. D. (1995) J. Biol. Chem. 270, 27127-27135) and imply that alternative splicing mechanisms may in part control the molecular polymorphism of syndecan-1 and, therefore, the efficiency and versatility of this protein in its co-receptor functions.

The syndecans, tuners of transmembrane signaling

Syndecans, a family of transmembrane proteoglycans, are putative integrators of extracellular signals. The interaction of syndecans with extracellular ligands via particular motifs in their heparan sulfate chains, their clustering, association with particular cytoskeletal structures, binding to cytoplasmic effectors, and intracellular phosphorylation represent as many means to bring this role to a successful conclusion. In this review, we will briefly address the characteristics of syndecans as heparan sulfate proteoglycans (HSPGs) and focus mainly on the properties, binding interactions, and potential signaling functions of the cytoplasmic domains of these molecules.

Molecular and clinical study of 18 families with ADCA type II: evidence for genetic heterogeneity and de novo mutation

The SCA7 mutation has been found in 54 patients and 7 at-risk subjects from 17 families who have autosomal dominant cerebellar ataxia (ADCA) II with progressive pigmentary maculopathy. In one isolated case, haplotype reconstruction through three generations confirmed a de novo mutation owing to paternal meiotic instability. Different disease-associated haplotypes segregated among the SCA7-positive kindreds, which indicated a multiple origin of the mutation. One family with the clinical phenotype of ADCA type II did not have the CAG expansion that indicated locus heterogeneity. The distribution of the repeat size in 944 independent normal chromosomes from controls, unaffected at-risk subjects, and one affected individual fell into two ranges. The majority of the alleles were in the first range of 7-19 CAG repeats. A second range could be identified with 28-35 repeats, and we provide evidence that these repeats represent intermediate alleles that are prone to further expansion. The repeat size of the pathological allele, the widest reported for all CAG-repeat disorders, ranged from 37 to approximately 220. The repeat size showed significant negative correlation with both age at onset and age at death. Analysis of the clinical features in the patients with SCA7 confirmed that the most frequently associated features are pigmentary maculopathy, pyramidal tract involvement, and slow saccades. The subjects with <49 repeats tended to have a less complicated neurological phenotype and a longer disease duration, whereas the converse applied to subjects with >/=49 repeats. The degree of instability during meiotic transmission was greater than in all other CAG-repeat disorders and was particularly striking in paternal transmission, in which a median increase in repeat size of 6 and an interquartile range of 12 were observed, versus a median increase of 3 and interquartile range of 3.5 in maternal transmission.

Glypican-1 is a VEGF165 binding proteoglycan that acts as an extracellular chaperone for VEGF165

Glypican-1 is a member of a family of glycosylphosphatidylinositol anchored cell surface heparan sulfate proteoglycans implicated in the control of cellular growth and differentiation. The 165-amino acid form of vascular endothelial growth factor (VEGF165) is a mitogen for endothelial cells and a potent angiogenic factor in vivo. Heparin binds to VEGF165 and enhances its binding to VEGF receptors. However, native HSPGs that bind VEGF165 and modulate its receptor binding have not been identified. Among the glypicans, glypican-1 is the only member that is expressed in the vascular system. We have therefore examined whether glypican-1 can interact with VEGF165. Glypican-1 from rat myoblasts binds specifically to VEGF165 but not to VEGF121. The binding has an apparent dissociation constant of 3 x 10(-10) M. The binding of glypican-1 to VEGF165 is mediated by the heparan sulfate chains of glypican-1, because heparinase treatment abolishes this interaction. Only an excess of heparin or heparan sulfates but not other types of glycosaminoglycans inhibited this interaction. VEGF165 interacts specifically not only with rat myoblast glypican-1 but also with human endothelial cell-derived glypican-1. The binding of 125I-VEGF165 to heparinase-treated human vascular endothelial cells is reduced following heparinase treatment, and addition of glypican-1 restores the binding. Glypican-1 also potentiates the binding of 125I-VEGF165 to a soluble extracellular domain of the VEGF receptor KDR/flk-1. Furthermore, we show that glypican-1 acts as an extracellular chaperone that can restore the receptor binding ability of VEGF165, which has been damaged by oxidation. Taken together, these results suggest that glypican-1 may play an important role in the control of angiogenesis by regulating the activity of VEGF165, a regulation that may be critical under conditions such as wound repair, in which oxidizing agents that can impair the activity of VEGF are produced, and in situations were the concentrations of active VEGF are limiting.

Heparan sulfate-modified CD44 promotes hepatocyte growth factor/scatter factor-induced signal transduction through the receptor tyrosine kinase c-Met

CD44 has been implicated in tumor progression and metastasis, but the mechanism(s) involved is as yet poorly understood. Recent studies have shown that CD44 isoforms containing the alternatively spliced exon v3 carry heparan sulfate side chains and are able to bind heparin-binding growth factors. In the present study, we have explored the possibility of a physical and functional interaction between CD44 and hepatocyte growth factor/scatter factor (HGF/SF), the ligand of the receptor tyrosine kinase c-Met. The HGF/SF-c-Met pathway mediates cell growth and motility and has been implicated in tumor invasion and metastasis. We demonstrate that a CD44v3 splice variant efficiently binds HGF/SF via its heparan sulfate side chain. To address the functional relevance of this interaction, Namalwa Burkitt's lymphoma cells were stably co-transfected with c-Met and either CD44v3 or the isoform CD44s, which lacks heparan sulfate. We show that, as compared with CD44s, CD44v3 promotes: (i) HGF/SF-induced phosphorylation of c-Met, (ii) phosphorylation of several downstream proteins, and (iii) activation of the MAP kinases ERK1 and -2. By heparitinase treatment and the use of a mutant HGF/SF with greatly decreased affinity for heparan sulfate, we show that the enhancement of c-Met signal transduction induced by CD44v3 was critically dependent on heparan sulfate moieties. Our results identify heparan sulfate-modified CD44 (CD44-HS) as a functional co-receptor for HGF/SF which promotes signaling through the receptor tyrosine kinase c-Met, presumably by concentrating and presenting HGF/SF. As both CD44-HS and c-Met are overexpressed on several types of tumors, we propose that the observed functional collaboration might be instrumental in promoting tumor growth and metastasis.

[Medicine seized by the principle of precaution]

The principle of precaution first appeared about ten years ago as a new type of action and responsibility in the environmental domain. It prescribes taking immediate action to avoid serious environmental consequences, rather than waiting for scientifically established proof of the danger. Some lawyers are now recommending that this approach be extended to the medical field. By recommending decisive action based on a purely hypothetical risk it goes well beyond classic preventive measures, which are introduced only after identification and proof risk. This new approach is presented as an added safety precaution. Radical application of this concept could, however, lead to an irrational approach to health security and constitute an obstacle to technical progress. Although the legal world has already adopted this new concept it is important that the medical world contribute to evaluating this new standard.

Heparan sulphate proteoglycan expression in human primary liver tumours

Heparan sulphate proteoglycans (HSPGs) play important biological roles in cell-matrix adhesion processes and are essential regulators of growth factor actions (e.g., as co-receptor for hepatocyte growth factor). Since in liver carcinogenesis, interactions between cells, the matrix, and growth factors play a major role, the aim of this study was to investigate whether the distribution pattern of HSPGs is altered in human primary liver tumours. Twenty-two primary liver tumours and five normal liver biopsies were studied, using specific monoclonal antibodies against syndecans-1, -2, -3, and -4; glypican; perlecan; and heparan sulphate chains. Cholangiocarcinomas as well as hepatocellular carcinomas showed an altered immunoreactivity pattern of the different HSPGs in comparison with normal liver parenchyma, probably reflecting the growth regulatory roles of HSPGs. Intracellular positivity for integral membrane HSPGs syndecan-1 and especially syndecan-4 was a constant finding in most tumours, suggesting increased synthesis or internalization of these HSPGs. Syndecan-3 and perlecan expression in tumours was found in an expected distribution pattern. The strong reactivity for syndecan-3 and perlecan in tumoral stromal vessels might suggest a role for these HSPGs in tumoral angiogenesis. In addition, perlecan probably exerts its known growth factor reservoir function also in the stroma of primary liver tumours.

Heparan sulphate proteoglycan expression in human primary liver tumours

Heparan sulphate proteoglycans (HSPGs) play important biological roles in cell-matrix adhesion processes and are essential regulators of growth factor actions (e.g., as co-receptor for hepatocyte growth factor). Since in liver carcinogenesis, interactions between cells, the matrix, and growth factors play a major role, the aim of this study was to investigate whether the distribution pattern of HSPGs is altered in human primary liver tumours. Twenty-two primary liver tumours and five normal liver biopsies were studied, using specific monoclonal antibodies against syndecans-1, -2, -3, and -4; glypican; perlecan; and heparan sulphate chains. Cholangiocarcinomas as well as hepatocellular carcinomas showed an altered immunoreactivity pattern of the different HSPGs in comparison with normal liver parenchyma, probably reflecting the growth regulatory roles of HSPGs. Intracellular positivity for integral membrane HSPGs syndecan-1 and especially syndecan-4 was a constant finding in most tumours, suggesting increased synthesis or internalization of these HSPGs. Syndecan-3 and perlecan expression in tumours was found in an expected distribution pattern. The strong reactivity for syndecan-3 and perlecan in tumoral stromal vessels might suggest a role for these HSPGs in tumoral angiogenesis. In addition, perlecan probably exerts its known growth factor reservoir function also in the stroma of primary liver tumours.

GPC4, the gene for human K-glypican, flanks GPC3 on xq26: deletion of the GPC3-GPC4 gene cluster in one family with Simpson-Golabi-Behmel syndrome

The glypicans constitute a growing family of cell surface heparan sulfate proteoglycans that may play a role in the control of cell division and growth regulation. Recently, deletions and translocations involving GPC3 (the gene for glypican-3, localized on Xq26) have been identified in patients with Simpson-Golabi-Behmel syndrome (SGBS). This X-linked syndrome is characterized by pre- and postnatal overgrowth, visceral and skeletal abnormalities, and a high risk for the development of embryonal tumors, mostly Wilms tumor and neuroblastoma. In the present report we show that the gene for human K-glypican/glypican-4 (GPC4) also maps to Xq26, centromeric to GPC3. The glypican-4 protein is encoded by nine exons. Establishment of a BAC/PAC contig physically linking GPC4 and GPC3 indicates that these two genes are arranged in a tandem array, the 5' end of GPC4 flanking the 3' end of GPC3. Unlike the glypican-3 message, the glypican-4 message is nearly ubiquitous. Analysis of DNA samples from eight patients with diagnosis of SGBS identified one individual with a deletion that involves the entire GPC4 gene and the last two exons of GPC3. The tight clustering of GPC3 and GPC4, with deletions that occasionally affect both genes, may be relevant for explaining the variability of the SGBS phenotype.

[Secondary cubital paralysis from prolonged thoracic drainage]

In intensive therapy patients, thoracic drains are usually inserted in the lateral part of thorax with the extension tube crossing the posterior aspect of the upper limb. We report the cases of two sedated patients who experienced ulnar palsy from a thoracic drain located behind their elbow.

A polymorphism in the major immediate-early gene delineates groups among cytomegalovirus clinical isolates

Major immediate-early gene exon 4 sequences were determined at codons 161-241 and 254-397 in 25 cytomegalovirus clinical strains and compared with those of reference strains AD169 and Towne. The nucleotide sequences at codon 161-241 segregated into three groups which could be determined by restriction mapping of a 247-nucleotide amplified target. AD169 and Towne belonged to the same group. Clustered variations and group-specific amino-acid motifs found in the deduced peptide sequence of the two immediate-early (IE) exon 4 regions raised a question is to the effects of polymorphism on IE1 function and/or immunogenicity. On the basis of restriction analysis of polymerase chain reaction (PCR) products, virus isolates were also classified into four glycoprotein B (gB) genotypes. Strain distribution in IE1 and gB genotypes showed a lack of concordance of the two grouping methods, and no preferential association was observed between the clinical context or kind of specimen and IE1 or gB groups. These data lead up to further prospective studies which could provide important information on the implication of the MIE gene region in virus pathogenesis and indicate whether linkage unbalance exists in particular clinical contexts between IE1 and gB loci.

Ligation of cell surface heparan sulfate proteoglycans by antibody-coated beads stimulates phagocytic uptake into epithelial cells: a model for cellular invasion by Neisseria gonorrhoeae

Binding of a particular opacity outer membrane protein (Opa) of Neisseria gonorrhoeae to cell surface heparan sulfate proteoglycans (HSPGs) of epithelial cells results in tight bacterial adherence; however, the role of this ligand-receptor interaction in triggering the subsequent bacterial internalization step is uncertain. Here we have used latex beads coated with HSPG-ligating antibodies as an in vitro model to study the role of HSPGs in gonococcal uptake into epithelial cells. Beads and gonococci showed the same cell line-specified adherence patterns and increase in phagocytic uptake mediated by serum or purified vitronectin (Vn). Heparitinase digestion as well as antibody competition experiments indicate that a critical level of HSPG ligation is necessary and sufficient to trigger phagocytic uptake into epithelial cells. Vn was found to specifically enhance HSPG-dependent phagocytic uptake while phagocytosis resulting from the ligation of other cell surface receptors was unaffected in the presence of Vn. Pharmacological studies with PKC inhibitors suggest a role for PKC in phagocytic uptake of HSPG-ligating beads. The use of drugs impairing cytoskeletal functions indicates that HSPG-dependent phagocytosis requires actin polymerization by a process distinct from receptor-mediated endocytosis.