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The Galloway-Mowat syndrome consists of early onset nephrotic syndrome and central nervous system anomalies. Additional anomalies including hiatal hernias have been reported but are not consistently present. Various renal histopathologic changes have been reported and it is unclear whether these represent heterogeneity within the syndrome or different stages of disease progression. We describe a patient with Galloway- Mowat syndrome who had a renal biopsy at 9 months that showed minimal changes. She died at 42 months at which time the renal autopsy finding was diffuse mesangial sclerosis. Neuropathologic findings included a small brain with cerebral dysplasia, leukomalacia and absence of the cerebellar granular layer without leptomeningeal heterotopia. The autopsy also revealed bilateral ovarian agenesis. This is the first report of serial histopathologic changes and ovarian agenesis in Galloway-Mowat syndrome.

Agrin is a heparan sulfate proteoglycan (HSPG) that is highly concentrated in the synaptic basal lamina at the neuromuscular junction (NMJ). Agrin-like immunoreactivity is also detected outside the NMJ. Here we show that agrin is a major HSPG component of the human glomerular basement membrane (GBM). This is in addition to perlecan, a previously characterized HSPG of basement membranes. Antibodies against agrin and against an unidentified GBM HSPG produced a strong staining of the GBM and the NMJ, different from that observed with anti-perlecan antibodies. In addition, anti-agrin antisera recognized purified GBM HSPG and competed with an anti-GBM HSPG monoclonal antibody in ELISA. Furthermore, both antibodies recognized a molecule that migrated in SDS-PAGE as a smear and had a molecular mass of approximately 200-210 kD after deglycosylation. In immunoelectron microscopy, agrin showed a linear distribution along the GBM and was present throughout the width of the GBM. This was again different from perlecan, which was exclusively present on the endothelial side of the GBM and was distributed in a nonlinear manner. Quantitative ELISA showed that, compared with perlecan, the agrin-like GBM HSPG showed a sixfold higher molarity in crude glomerular extract. These results show that agrin is a major component of the GBM, indicating that it may play a role in renal ultrafiltration and cell matrix interaction. (J Histochem Cytochem 46:19-27, 1998)

We determined the specificity of two hamster monoclonal antibodies and a sheep polyclonal antiserum against heparan sulfate proteoglycan isolated from rat glomerular basement membrane. The antibodies were characterized by enzyme-linked immunosorbent assay on various basement membrane components and immunoprecipitation with heparan sulfate proteoglycan with or without heparitinase pre-treatment. These experiments showed that the antibodies specifically recognize approximately 150-, 105-, and 70-kDa core proteins of rat glomerular basement membrane heparan sulfate proteoglycan. Recently, we showed that agrin is a major heparan sulfate proteoglycan in the glomerular basement membrane (Groffen, A. J. A., Ruegg, M. A., Dijkman, H. B. P. M., Van der Velden, T. J., Buskens, C. A., van den Born, J., Assmann, K. J. M., Monnens, L. A. H., Veerkamp, J. H., and van den Heuvel, L. P. W. J. (1998) J. Histochem. Cytochem. 46, 19-27). Therefore, we tested whether our antibodies recognize agrin. To this end, we evaluated staining of Chinese hamster ovary cells transfected with constructs encoding full-length or the C-terminal half of rat agrin by analysis on a fluorescence-activated cell sorter. Both hamster monoclonals and the sheep antiserum clearly stained cells transfected with the construct encoding full-length agrin, whereas wild type cells and cells transfected with the construct encoding the C-terminal part of agrin were not recognized. A panel of previously characterized monoclonals, directed against C-terminal agrin, clearly stained cells transfected with either of the constructs but not wild type cells. This indicates that both hamster monoclonals and the sheep antiserum recognize epitopes on the N- terminal half of agrin. By immunohistochemistry on rat renal tissue, we compared distribution of N-terminal agrin with that of C-terminal agrin. The monoclonal antibodies against C-terminal agrin stained almost exclusively the glomerular basement membrane, whereas the anti-N-terminal agrin antibodies recognized all renal basement membranes, including tubular basement membranes. Based on these results, we hypothesize that full-length agrin is predominantly expressed in the glomerular basement membrane, whereas in most other renal basement membranes a truncated isoform of agrin is predominantly found that misses (part of) the C terminus, which might be due to alternative splicing and/or posttranslational processing. The possible significance of this finding is discussed.

Heparan sulfate proteoglycans (HSPGs) are essential components of the glomerular basement membrane (GBM) carrying a strong anionic charge. A well- characterized extracellular HSPG is perlecan, ubiquitously expressed in basement membranes. A cDNA construct encoding domains I and II of human perlecan was expressed as a fusion protein with glmathione S-transferase. This fusion protein was used to generate monoclonal antibody 95J10. We compared the staining pattern of 95J10 with that of M215, a previously prepared mAb that recognizes HSPG isolated from human GBM. In kidney cortex, the antiperlecan mAb 95J10 showed a strong staining of the mesangium, Bowman's capsule, the tubular basement membrane, and stained the GBM only slightly. In contrast, M215 predominantly stained the GBM in a linear fashion. Immunoelectron microscopy supported these results, showing concentrations of perlecan in some regions of the GBM, whereas the unidentified M215 antigen was homogemously distributed throughout the GBM. In other human tissues, both antibodies also produced a different staining pattern. Furthermore, a polyclonal antiserum recognizing HSPG isolated from the GBM did not recognize perlecan from EHS tumors. These results provide evidence for the presence of another HSPG in the GBM that is immunologically distinct froth perlecan. The absence of perlecan splice variants in the kidney suggests that this component is encoded by a different gene than perlecan. Given its marked expression in the GBM, this component could be a determining factor in the maintenance of selective glomerular permeability.

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Renal failure in the newborn infant is mainly determined by vascular causes. In this report we describe a patient with a particular vascular cause of renal failure. The patients was the product of a twin pregnancy in which the twin partner died in utero. In retrospect, the twins appeared to be monozygotic. As the pregnancy was studied carefully prenatally by ultrasound, we were able to observe the development of this condition, characterized by oliguria, oligohydramnios, and lung hypoplasia; the oligohydramnios sequence. After organ development had been normal initially, renal function was lost and the oligohydramnios sequence developed in the survivor after the cotwin had died in utero.

We present the in vitro expression and purification of N-terminal fragments of human perlecan in insect cells. Three tailored fragments of human perlecan cDNA were introduced into the polyhedrin locus of baculovirus expression vectors (BEVs) encoding amino acids 1-196 (domain I), 1-404 (domain I + IIa) and 1-506 (domain I + IIab). The integrity of the BEVs was checked by DNA sequencing, polymerase chain reaction, restriction enzyme analysis and Southern blotting. Northern hybridization and metabolic labeling with [35S]methionine showed that expression of the perlecan-(1-404)- and the -(1-506)-peptide was successful, but in the case of the perlecan-(1-196)-peptide no recombinant protein was produced. Immunoblotting showed that both the (1-404)-peptide and (1-506)-peptide are recognized by 95J10, a monoclonal antibody that was previously raised against perlecan-(24-404)-peptide expressed in Escherichia coli. Gel permeation and anion-exchange chromatography were applied to purify the recombinant proteins. Glycosaminoglycans were demonstrated to be present. Deglycosylation with chondroitinase ABC showed that the perlecan-(1-404)-peptide was glycosylated with chondroitin sulfate residues. Consistent with these results, glycosaminoglycans isolated from the perlecan-(1-404)-peptide were identified as chondroitin sulfate by agarose gel electrophoresis. Furthermore the perlecan-(1-404)-peptide showed affinity to immobilized basic fibroblast growth factor. The availability of baculovirusderived recombinant perlecan fragments will facilitate domain-specific investigation of the structural and functional properties of perlecan in the future.

Item does not contain fulltext KUN, 09 februari 1999 Promotores : Monnens, L.A.H., Veerkamp, J.H. Co-promotor : Heuvel, L.P.W.J. van den

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Agrin is a heparan sulfate proteoglycan involved in the development of the neuromuscular junction during embryogenesis. In addition to this well- characterized function, agrin may have additional functions in other tissues and during other stages in development. In this study we present the cDNA sequence of human agrin, and demonstrate a high agrin content in adult basement membranes. The N-terminal domain of human agrin is highly similar to that of chick agrin, suggesting a similar function in laminin binding. The presence of three SGXG sequences supports serine-linked glycosylation of the core protein, two sites being particularly favorable for heparan sulfate attachment. Comparison of levels of agrin mRNA in fetal and adult human tissues showed a remarkable upregulation in adult kidney and lung. In both tissues truncated agrin transcripts were detected, lacking the region that encodes the laminin-binding domain. The high transcription levels in lung and kidney corresponded with the accumulation of agrin in the alveolar and glomerular basement membranes, suggesting a filtration-associated function. These data provide new directions for investigating the role of agrin in its different physiological environments, including the basement membranes of the neuromuscular junction, kidney and lung.

In vivo and in vitro findings have shown that plasma of patients with idiopathic nephrotic syndrome (INS) contain factors that increase glomerular permeability to proteins. The effects of these factors on proteoglycan synthesis by glomerular cells are unknown. To investigate the effect of plasma from patients with INS (n = 23) and other glomerulopathies (n = 12) on the amount of proteoglycans synthesized by cultured rat mesangial cells and human glomerular epithelial cells, glomerular cells were cultured for 24 h with plasma from patients or control subjects, and incorporation of Na2(35)SO4 in chondroitin dermatan sulfate and heparan sulfate was assessed using a cationic nylon membrane. The mean ratio of glycosaminoglycan produced by rat mesangial cells when in contact with plasma (5%) from INS patients to the amount produced when in contact with control plasma was 0.70+/-0.06. The mean ratio of heparan sulfate was 0.58+/-0.08. The decrease of heparan sulfate production was present in the cellular and in the extracellular fraction. It was observed when the cells were in contact with plasma from patients in relapse but not when in remission. No decrease of heparan sulfate production was observed with four of the five patients with membranous glomerulonephritis (ratio of 1.27+/-0.03), IgA nephropathy (n = 5, ratio of 1.27+/-0.03), and membranoproliferative glomerulonephritis (n = 2, ratio of 1.39+/-0.34). When human glomerular epithelial cells were exposed to 5% plasma from INS patients in relapse (n = 9), the mean ratio of heparan sulfate was 0.62+/-0.06 in the cellular fraction and 0.72+/-0.08 in the medium. When in contact with plasma from patients in remission, no difference of glycosaminoglycan production was observed. A factor present in plasma from patients with INS during initial episodes or relapses is able to decrease the proteoglycan production of glomerular cells.

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The aim of this multicentre study was to analyse the long-term outcome of idiopathic membranoproliferative glomerulonephritis (MPGN) according to histological type and to the presence of C3 nephritic factor. Fifty patients aged 2-14 years at the onset of the study were followed over 2-20 years; 26 patients had MPGN type I, 17 had type II and 7 had type III. Treatment was variable. At the last observation, 30 patients had reached terminal and four pre-terminal renal failure. The median survival probability until renal death was 15.3, 8.7 and 15.9 years for disease types I, II and III respectively (difference between MPGN types I + III versus type II: p = 0.013). The presence of an initial nephrotic syndrome was associated with a more rapid progression (p = 0.018). C3 nephritic factor was of no prognostic value. We conclude that the outcome of MPGN mainly depends on the histological type observed.

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