Enrichment of high mannose-type glycans in nervous tissue glycoproteins in neuronal ceroid-lipofuscinosis

The contribution of multicellular model organisms to neuronal ceroid lipofuscinosis research

The NCLs (neuronal ceroid lipofuscinosis) are forms of neurodegenerative disease that affect people of all ages and ethnicities but are most prevalent in children. Commonly known as Batten disease, this debilitating neurological disorder is comprised of 13 different subtypes that are categorized based on the particular gene that is mutated (CLN1-8, CLN10-14). The pathological mechanisms underlying the NCLs are not well understood due to our poor understanding of the functions of NCL proteins. Only one specific treatment (enzyme replacement therapy) is approved, which is for the treating the brain in CLN2 disease. Hence there remains a desperate need for further research into disease-modifying treatments. In this review, we present and evaluate the genes, proteins and studies performed in the social amoeba, nematode, fruit fly, zebrafish, mouse and large animals pertinent to NCL. In particular, we highlight the use of multicellular model organisms to study NCL protein function, pathology and pathomechanisms. Their use in testing novel therapeutic approaches is also presented. With this information, we highlight how future research in these systems may be able to provide new insight into NCL protein functions in human cells and aid in the development of new therapies.

Comparative transcriptomics reveals mechanisms underlying cln3-deficiency phenotypes in Dictyostelium

Mutations in CLN3 cause a juvenile form of neuronal ceroid lipofuscinosis (NCL). This devastating neurological disorder, commonly known as Batten disease, is currently untreatable due to a lack of understanding of the physiological role of the protein. Recently, work in the social amoeba Dictyostelium discoideum has provided valuable new insight into the function of CLN3 in the cell. More specifically, research has linked the Dictyostelium homolog (gene: cln3, protein: Cln3) to protein secretion, adhesion, and aggregation during starvation, which initiates multicellular development. In this study, we used comparative transcriptomics to explore the mechanisms underlying the aberrant response of cln3^- cells to starvation. During starvation, 1153 genes were differentially expressed in cln3^- cells compared to WT. Among the differentially expressed genes were homologs of other human NCL genes including TPP1/CLN2, CLN5, CTSD/CLN10, PGRN/CLN11, and CTSF/CLN13. STRING and GO term analyses revealed an enrichment of genes linked to metabolic, biosynthetic, and catalytic processes. We then coupled the findings from the RNA-seq analysis to biochemical assays, specifically showing that loss of cln3 affects the expression and activity of lysosomal enzymes, increases endo-lysosomal pH, and alters nitric oxide homeostasis. Finally, we show that cln3^- cells accumulate autofluorescent storage bodies during starvation and provide evidence linking the function of Cln3 to Tpp1 and CtsD activity. In total, this study enhances our knowledge of the molecular mechanisms underlying Cln3 function in Dictyostelium.

Brain lysosomal hydrolases in neuronal ceroid-lipofuscinoses

Although the neuronal ceroid-lipofuscinoses (NCLs) are often referred to as lysosomal storage disorders, information on brain lysosomal hydrolases in NCLs is not available. We have determined the specific activities of several acid hydrolases in postmortem brain gray matter of infantile (INCL), late infantile (LINCL), juvenile (JNCL), and adult (ANCL) forms of NCL, patients affected with other neurological disorders (ON), and normal controls. The specific activities of beta-hexosaminidase A and B were significantly high in JNCL gray matter, whereas in LINCL, the increase is significant only in beta-hexosaminidase compared to the controls. A significant increase in the activities of alpha-mannosidase, beta-glucuronidase, and acid phosphatase was also observed in LINCL and JNCL patients compared to the control values. beta-galactosidase activity was also found to be elevated in JNCL brains over the controls. In contrast, activities of beta-glucosidase and sialidase appeared to be lowered in INCL and LINCL. On the other hand, alpha-fucosidase, beta-mannosidase, and sulfatase were unaffected in NCLs brains. Thus, the present data indicate NCLs related abnormalities in some of the acid hydrolases in brain gray matter, which are primarily glycoproteins of lysosomal origin. These data in conjuction with the reported association of sphingolipid activator proteins (SAP) A and D and lysosomal glycoproteins with NCL storage bodies imply abberations in the glycoconjugate metabolism and lysosomal function.

Childhood neuronal ceroid-lipofuscinoses in Argentina

We report on 30 cases of neuronal ceroid lipofuscinoses (NCL), mainly diagnosed in 1985-1993 in Argentina, whose population is predominantly of European descent. Twenty-four cases were late infantile Jansky-Bielschowsky (LINCL) and 6 were juvenile Spielmeyer-Vogt (JNCL). Sex ratio was female:male, 20:10. Age range and mean at onset and at diagnosis for the LINCL cases were 1-6 years, mean 3.1, and 2-11 years, mean 5.5, and for the JNCL cases, 5-9 years, mean 7, and 9-18 years, mean 13, respectively. Cases were referred for biopsy after neurological examination, and most included complete electrophysiological [electroencephalography (EEG) with photic stimulation, electroretinography (ERG), and visual-evoked potential (VEP)], neuroimaging, and neurometabolic investigation. NCL was the first suspected clinical diagnosis, followed by mitochondrial encephalopathy in some cases of recent onset. Except for 1 case, clinical findings were homogeneous in LINCL, characterized by refractive epilepsy, mental regression and progressive deterioration, ataxia, myoclonia, and visual loss. Abnormal VEP, ERG, and EEG, with polyphasic high-voltage spikes when photic stimulation was performed at low frequency, were observed. Visual impairment and retinitis pigmentosa were early manifestations in 4/6 JNCL, followed by mental abnormalities, motor deterioration, and myoclonic jerks, while 2/4 followed an atypical course. In both variants inheritance was autosomal-recessive. Five out of 27 families had more than 1 affected member, 3 of whom were included in our series. Diagnosis was initially performed in conjunctival biopsy in 3 cases, skin in 5, muscle in 17, and brain in 5, though most cases had a concomitant biopsy from another tissue including nerve, and there was a single brain autopsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycoprotein metabolism in neuronal ceroid lipofuscinosis fibroblasts

Human skin fibroblast lines of the infantile form of neuronal ceroid lipofuscinosis and control lines were cultured in the presence of [3H]glucosamine plus [3H]mannose and [35S]methionine. The labeled glycoconjugates were compared by quantitative polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The infantile form of the disease showed a 75% decrease of four glycoprotein components of M(r) 120-140 kDa. These components appeared to be N-linked glycoproteins as peptide-N4-(N-acetyl-beta-glucosaminyl) asparagine amidase (PNGase F) released 86-96% of the labeled carbohydrate from the labeled protein. These results suggest that the infantile form of this disease may be characterized by abnormalities in glycoconjugate metabolism leading to reduction of specific glycoproteins.

Biochemical studies on the juvenile form of ceroid-lipofuscinosis

Accumulation of oligosaccharyl diphosphodolichols (oligo-PP-Dol) in brains of patients with various forms of ceroid-lipofuscinoses (CL) is one of the most reproducible biochemical changes known so far. The objective of this study is to understand the biochemical basis of this observation. The biosynthesis of oligo-PP-Dol was studied by the incorporation of labelled glucose from UDP [14C]glucose into oligo-PP-Dol in cultured skin fibroblasts, and showed no changes in the level of synthesis. The level of labelled glucose incorporated into glycoproteins was also unchanged, suggesting that there is no decrease in the oligosaccharide transfer to proteins in this disorder. Since the biosynthesis and utilization of oligo-PP-dol are unaffected, a defect in the catabolism may be the only possibility for the storage of this compound in CL. Since terminal mannose residues are present in the accumulating oligo-PP-Dol, mannosidase activities at pH 4.4 and 6.0 were determined in cultured skin fibroblasts. Both mannosidase activities were unchanged in skin fibroblasts of juvenile CL. Endo-beta-N-acetylglucosaminidase-1 activities were determined in cultured skin fibroblasts using dansylated Man6GlcNAcGlcNAc-Asn as substrate. In three patients, a drastic reduction in the level of the pH 4.5 enzyme was shown, while the neutral pH enzyme activity was unaffected. A deficiency of the endo-beta-N-acetylglucosaminidase-1 will not only explain the accumulation of oligo-PP-Dol but also the known storage of high-mannose glycoproteins.

Altered protein patterns in brains of children with neuronal ceroid lipofuscinosis

The neuronal ceroid lipofuscinoses (NCL) are a group of inherited neurodegenerative diseases characterized by massive intralysosomal accumulation of storage materials. We have studied the protein patterns in 5 NCL, 5 control, and one Alzheimer disease brains. When protein patterns in NCL and control brain gray matter homogenates were examined by SDS-PAGE, NCL brains showed an absence or greatly reduced amounts of the Mr 160-180 kDa component and reduced amounts of the Mr 29-36 kDa component. Concomitantly, an increase in several components with Mrs of 45-50 kDa was noted. The 180 kDa polypeptide appears to be a glycoprotein because it was bound to the lectins concanavalin A and Ulex europaeus. Recently, the abnormal processing of amyloid protein precursor (APP) and its potential role in NCL have been suggested. Possible defects in tissue proteases and protease inhibitors may be considered responsible for the presence of these amyloid beta protein precursor fragments. To examine this possibility we are using polyclonal antibodies to the C terminal 672-695 (APP) and monoclonal antibodies to inter-alpha-trypsin inhibitor. Polypeptides with molecular weights of approximately 35-38 kDa were detected in the NCL brain, but not in controls in both cases. These findings suggest abnormal protein processing in NCL brain tissue, disturbances in protein and glycoconjugate metabolism, impaired lysosomal function (i.e., metabolic enzyme and/or proteases/proteinase inhibitor abnormalities), and the involvement of improperly processed APP.

Lectin histochemistry in brains with juvenile form of neuronal ceroid-lipofuscinosis (Batten disease)

Defective utilization of dolichols in the synthesis of glycoprotein leads to an accumulation of the storage, pigment "ceroid" lipofuscin, containing high-mannose-type glycoconjugates, in brains affected by neuronal ceroid-lipofuscinoses (NCL). We have employed lectin histochemistry to study the distribution of such compounds and the composition of other glycoconjugates in brains of patients with a juvenile form of the disease (JNCL). Concanavalin A detected the high-mannose glycoconjugates in all neurons of brains with JNCL, in lipofuscin-containing neurons of aging brains and in some neurons of age-matched control brains. Three other lectins (soybean agglutinin, Peanut agglutinin and Ulex europaeus agglutinin-I) recognized sugar moieties in neurons containing lipofuscin in patients only with JNCL and not in age-matched or aging brains. The results led to the conclusion, that the binding pattern of these three lectins may differentiate between storage materials of NCL and aging brains.

Glycoconjugates in storage cytosomes from ceroid-lipofuscinosis (Batten's disease) and in lipofuscin from old-age brain

The ceroid-lipofuscinoses (CL) are a group of inherited diseases characterised by the accumulation, in brain, of autofluorescent storage cytosomes which have similar histochemical staining properties to lipofuscin, the neuronal wear and tear pigment of old-age brain. The storage cytosomes stain strongly with periodic acid-Schiff reagent (PAS), indicating the presence of carbohydrate. In brain from each childhood form of CL, concentrations of phosphorylated dolichol (Dol-P) are 10- to 20- fold higher than in age-matched controls. Brain Dol-P concentrations are also increased between 2 and 5- fold in several different lipidoses and in elderly subjects. Much of the Dol-P which accumulates is located within the storage cytosomes. Dol-P constitutes 2-3% of the dry weight of storage cytosomes from juvenile and late-infantile CL, and 0.3-0.7% of storage cytosomes from infantile CL, ovine CL and of lipofuscin isolated from old age brain. The bulk of the Dol-P in CL brain and in isolated storage cytosomes is present as dolichyl pyrophosphoryl oligosaccharides (Dol-PP-OS). The constitutions of the oligosaccharide moieties differ in the various forms of the disease. Histochemical analysis of frozen sections of unfixed brain after extraction by various lipid solvents indicates that the major part of the PAS positive intraneuronal material in CL brain and in old-age brain has the extraction properties of Dol-PP-OS. Carbohydrate represents 4-7% of the dry weight of CL storage cytosomes and of lipofuscin. The major monosaccharide components are mannose, N-acetyl glucosamine, glucose and galactose. Depending on the form of the disease studied, up to 40% of this material can be accounted for by Dol-PP-OS. Polyacrylamide gel electrophoresis of storage cytosomes followed by lectin blotting demonstrates several low molecular weight components which bind concanavalin A. These do not coelute with the major protein components and may well be Dol-PP-OS. We conclude that Dol-PP-OS are concentrated in storage cytosomes in CL and are one of their major glycoconjugate components.

Comparison of the clinical courses in patients with juvenile neuronal ceroid lipofuscinosis receiving antioxidant treatment and those without antioxidant treatment

Juvenile neuronal ceroid-lipofuscinosis (JNCL) is a progressive encephalopathy characterized by a neural and extraneural accumulation of ceroid and lipofuscin like storage cytosomes and by an autosomal recessive inheritance. It begins with a gradual loss of vision at the age of 4-7 years and is accompanied by epilepsy, a loss of motor function, and a progressive dementia (Santavuori 1988). We have studied 26 Finnish JNCL patients treated with vitamins E, B2, B6 and sodium selenite (antioxidant treatment) by using a JNCL disease specific scoring system introduced by Kohlschütter et al. (1988). Scores were given for the problems of vision, intellect, language, motor function, as well as epilepsy, and compared with the data of 17 German JNCL patients not treated with antioxidants (Kohlschütter et al. 1988). Loss of vision began at the same time among the Finnish and the German JNCL patients. However, loss of intellectual, language, and motor functions and total blindness occurred later among the group of Finnish JNCL patients treated with antioxidants. Courses of the epileptic seizures were rather heterogenous and slightly favouring the Finnish patients. This study supports the theory that antioxidant treatment retards JNCL disease. The study design, however, contains many possible biases, so that the results must be interpreted cautiously.

Lectin histochemical study of lipopigments: results with concanavalin A

Concanavalin A (Con A) binding to lipopigments (LPs) of the lipofuscin type was proved to be due to the high content of mannose. Two mannose bearing compounds could be recognized due to their different organic solvent solubility. One was best soluble in modified chloroform-methanol-water mixture (10:10:3) and corresponded most probably to the oligosaccharyl disphosphodolichol (oligo-PP-Dol) described to be significantly increased in LPs of inherited type. The second one, organic solvent insoluble corresponded to a glycoprotein (GP). The ratio of the two components varied. The deposition of the typical lipofuscin (age pigment) was dominated by the GP component. Its amount was greatest in neurolipofuscin (especially in the olivary nucleus) but very little in hepatocytic lipofuscin. In human neuronal ceroid lipofuscinoses (of early juvenile, and juvenile types) both components were found in large quantities in the storage granules of the affected neurons. The "protein type variant" of the storage material (Elleder, 1978) displayed the highest degree of lipid-bound mannose accumulation, the GP component being absent. In the late infantile, infantile and Kufs variants studied in paraffin sections only, the GP component was detectable, too as in the case of the secondary neuronal LP in mucopolysaccharidoses and gangliosidoses. In the canine model of NCL lipid bound mannose clearly predominated, the GP component being in low amount on average. Neither of the Con A reactive glycoconjugates could be identified as the component responsible for autofluorescence. However, both are most probably responsible for PAS positivity of lipofuscins. There were no detectable Con A reactive glycoconjugates in the histiocytic ceroid.

Lectin histochemical study of lipopigments with special regard to neuronal ceroid-lipofuscinosis. Results with concanavalin A

Concanavalin A (ConA) binding to lipopigments (LPs) of the lipofuscin type was proved to be due to the high content of mannose. The nature of the mannose bearing compound was twofold. One part was soluble in modified chloroform-methanol-water mixture (10:10:3) corresponding possibly to the oligosaccharyl diphosphodolichol (oligo-PP-Dol) described to be increased in LPs especially of inherited types. The second part, most probably a glycoprotein (GP), was entirely resistant to various extraction procedures. The ratio of the two components varied. The deposition of the typical lipofuscin (age pigment) was dominated by the GP component. Its amount was greatest in neurolipofuscin (especially in the olivary nucleus) and in the myocardium but very little in hepatocytic lipofuscin. In human neuronal ceroid lipofuscinoses (of early juvenile, and juvenile types) both components were found in large quantities in the storage granules of the affected neurons. The "protein type variant" of the storage material (Elleder 1978) displayed the highest degree of lipid-bound mannose accumulation, the GP component being extremely low or entirely absent. In the late infantile, infantile and Kufs variants studied in paraffin sections only, the GP component was detectable, too as in the case of the secondary neuronal LP in mucopolysaccharidoses and gangliosidoses. In the dog model of NCL lipid bound mannose clearly predominated, the GP component being concentrated in the cytoplasm and on the periphery od some storage granules. The nature of the GP component, a new finding of LP analysis, is discussed. The metabolic relationship between the two components is uncertain. Neither could be identified as the component resposible for autofluorescence.(ABSTRACT TRUNCATED AT 250 WORDS)

Experience over 17 years with antioxidant treatment in Spielmeyer-Sjögren disease

During the last 17 yr, 74 patients with Spielmeyer-Sjögren disease were treated in Finland with antioxidant supplementation. Twenty-seven patients received a combination of vitamin E, vitamin C, methionine and BHT. As the disease began to progress, the treatment was changed to a combination of sodium selenite and vitamin E in 14 of the 27 patients. The same combination was also given to 47 children (During the last 5-6 yr, vitamins B2 and B6 were also added.) who had not received previous antioxidant supplementation. The latter combination (called the Westermarck formula) appeared to be helpful to some patients. Statistical correlations between various neurological items and relevant laboratory data were sought. In the older patients a significant correlation was found between neurological dysfunction and ceruloplasmin, and also between epilepsy and ceruloplasmin, while a negative correlation was noticed between neurological dysfunction and glutathione peroxidase. In the younger patients, a negative correlation was observed between superoxide dismutase and epilepsy. Serum apolipoprotein B levels were below the normal range in the 6 patients investigated. So far the Westermarck formula seems to have been the best treatment devised yet in Spielmeyer-Sjögren disease, but further studies are needed for a better understanding of the pathogenesis of neuronal ceroid-lipofuscinoses disorders.

Clinico-pathological variability in the childhood neuronal ceroid-lipofuscinoses and new observations on glycoprotein abnormalities

Our 86 cases of neuronal ceroid-lipofuscinosis (NCL) included 7 children with the infantile variant, 28 with the late infantile variant, and 51 with the juvenile variant. Thirty-one cases were drawn from a NCL registry and were not evaluated personally by the authors. Another 30 cases from the registry were not included because of inadequate data. The clinical course was subacute in most children with the infantile and late infantile variants and chronic in the juvenile variant. Sixteen of 86 cases (19%) were considered to be atypical clinically [3/7 (43%) with the infantile variant, 3/28 (11%) with the late infantile variant, and 10/51 (20%) with the juvenile variant]. Clinical variability among and between families was most striking in the juvenile variant. Pathological investigations of skin, buffy coat and/or brain showed atypical and/or more than one type of cytoplasmic inclusions in 10/50 (20%) of late infantile and juvenile variants. All of the children with the infantile variant had granular, osmiophilic profile in tissues. Biochemical studies on the glycoproteins of cultured fibroblasts in three cases of juvenile NCL showed that there was a higher proportion of one size class of N-linked oligosaccharides and a higher proportion of mannose-containing glycoproteins in NCL than in control cells. This supports previous lectin histochemical studies of glycoconjugates in skin of juvenile NCL [Wisniewski and Szumanska, 1986] and suggests that there may be defects in the processing of N-linked oligosaccharides in the glycoproteins of juvenile NCL.

Neuronal ceroid-lipofuscinoses in childhood

Neuronal Childhood types of ceroid-lipofuscinoses (NCL) are reviewed. All three main types, infantile, late infantile and juvenile, are progressive encephalopathies characterized by neural and extraneural accumulation of ceroid- and lipofuscin like storage cytosomes. The pathogenesis of NCL is unknown. A disturbance of the peroxidation of polyunsaturated fatty acids and a defect in the processing and turn-over of the glycoproteins in the lysosomal membrane are those hypotheses which have been most widely investigated. Reduced membrane lipids and reduced membrane fluidity have recently been detected. Prenatal diagnosis, based on the characteristic ultrastructural findings, is possible in all types.

Bleomycin-detectable iron and phenanthroline-detectable copper in the cerebrospinal fluid of patients with neuronal ceroid-lipofuscinoses

The neuronal ceroid-lipofuscinoses (NCLs) are a group of recessively inherited neurodegenerative lysosomal storage diseases, the pathogenesis of which is unknown. In the present study, we have measured iron and cooper in cerebrospinal fluids (CSF) using methods that detect these metals in a "loosely bound" form, complexable to the chelators bleomycin and 1,10-phenanthroline. We studied 25 children with NCL, 21 children with encephalopathy of some other type, and 5 control children without neurological complications. The CSF concentrations of loosely bound iron at neutral pH values and of loosely bound copper did not correlate with the clinical diagnosis of the patients, nor did they parallel degenerative symptoms in NCL, such as mental impairment, visual loss, motor handicap, and epilepsy. However, the concentrations of loosely bound iron and copper increased significantly with the age of the patient; this is a novel finding and may represent increasing tissue destruction with age. Our present findings do not support a major role for primary iron toxicity in the development of neuronal degeneration. To investigate any secondary pathological role for malplaced transition metals, further research is required.