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Ilkka Mononen - One of the best experts on this subject based on the ideXlab platform.
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aspartylglycosaminuria a review
Orphanet Journal of Rare Diseases, 2016Co-Authors: Maria Arvio, Ilkka MononenAbstract:Aspartylglucosaminuria (AGU), a recessively inherited lysosomal storage disease, is the most common disorder of glycoprotein degradation with a high prevalence in the Finnish population. It is a lifelong condition affecting on the patient’s appearance, cognition, adaptive skills, physical growth, personality, body structure, and health. An infantile growth spurt and development of macrocephalia associated to hernias and respiratory infections are the key signs to an early identification of AGU. Progressive intellectual and physical disability is the main symptom leading to death usually before the age of 50 years.
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Massive accumulation of Man2GlcNAc2-Asn in nonneuronal tissues of glycosylasparaginase-deficient mice and its removal by enzyme replacement therapy
2004Co-Authors: Eira Kelo, Ulla Dunder, Ilkka MononenAbstract:Aspartylglycosaminuria (AGU) is caused by deficient enzy-matic activity of glycosylasparaginase (GA). The disease is characterized by accumulation of aspartylglucosamine (GlcNAc-Asn) and other glycoasparagines in tissues and body fluids of AGU patients and in an AGU mouse model. In the current study, we characterized a glycoasparagine carrying the tetrasaccharide moiety of a-D-Man-(1!6)-b-D-Man-(1!4)-b-D-GlcNAc-(1!4)-b-D-GlcNAc-(1!N)-Asn (Man2GlcNAc2-Asn) in urine of an AGU patient and also in the tissues of the AGU mouse model. Quantitative analysis demonstrated a massive accumulation of the compound espe-cially in nonneuronal tissues of the AGU mice, in which the levels of Man2GlcNAc2-Asn were typically 30–87 % of those of GlcNAc-Asn. The highest level of Man2GlcNAc2-Asn was found in the liver, spleen, and heart tissues of the AGU mice, the respective amounts being 87%, 76%, and 57 % of the GlcNAc-Asn levels. In the brain tissue of AGU mice the Man2GlcNAc2-Asn storage was only 9 % of that of GlcNAc-Asn. In contrast to GlcNAc-Asn, the storage of Man2-GlcNAc2-Asn markedly increased in the liver and spleen tissues of AGU mice as they grew older. Enzyme replacement therapy with glycosylasparaginase for 3.5 weeks reduced the amount of Man2GlcNAc2-Asn by 66–97 % in nonneuronal tissues, but only by 13 % in the brain tissue of the AGU mice. In conclusion, there is evidence for a role for storage of glycoasparagines other than aspartylglucosamine in the pathogenesis of AGU, and this possibility should be taken into consideration in the treatment of the disease. Key words: Aspartylglucosaminuria/enzyme replacement/ lysosomal enzymes/lysosomal storage/N-linked oligosaccharid
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Carriers of the Aspartylglucosaminuria genetic mutation and chronic arthritis.
Annals of the Rheumatic Diseases, 2002Co-Authors: Maria Arvio, M Peippo, P Leino, O. Kaipiainen-seppänen, Markku Kauppi, Kari Laiho, Hannu Kautiainen, Ilkka MononenAbstract:Methods: A group of 173 unrelated patients with rheuma- toid arthritis (RA) but with no family members with AGU each gave a blood sample for AGUFin major mutation DNA analysis. A group of 131 AGU carriers who were parents of patients with AGU completed a questionnaire on joint symptoms and gave a blood sample for rheumatoid factor (RF) analysis. Eight RF positive parents with prolonged joint symptoms had a rheumatological evaluation. Results: Six patients (1/28) with RA were carriers of the AGUFin major mutation, whereas the carrier frequency among Finns in general is 1/50 to 1/85. Three AGU car- riers had chronic arthritis (2.3%), and 17 (13%) were RF positive; the respective percentages among Finns in general are 1.4% and 5%. Conclusion: As for AGU disease, carrier status may also predispose to chronic arthritis.
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enzyme replacement therapy in a mouse model of aspartylglycosaminuria
The FASEB Journal, 2000Co-Authors: Ulla Dunder, Vesa Kaartinen, Pirjo Valtonen, Eira Vaananen, John Groffen, Nora Heisterkamp, Veli-matti Kosma, Ilkka MononenAbstract:Aspartylglycosaminuria (AGU), the most common lysosomal disorder of glycoprotein degradation, is caused by deficient activity of glycosylasparaginase (AGA). AGA-deficient mice share most of the clinical, biochemical and histopathologic characteristics of human AGU disease. In the current study, recombinant human AGA administered i.v. to adult AGU mice disappeared from the systemic circulation of the animals in two phases predominantly into non-neuronal tissues, which were rapidly cleared from storage compound aspartylglucosamine. Even a single AGA injection reduced the amount of aspartylglucosamine in the liver and spleen of AGU mice by 90% and 80%, respectively. Quantitative biochemical analyses along with histological and immunohistochemical studies demonstrated that the pathophysiologic characteristics of AGU were effectively corrected in non-neuronal tissues of AGU mice during 2 wk of AGA therapy. At the same time, AGA activity increased to 10% of that in normal brain tissue and the accumulation of as...
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progressive neurodegeneration in aspartylglycosaminuria mice
American Journal of Pathology, 1998Co-Authors: Ignacio Gonzalezgomez, Ilkka Mononen, John Groffen, Nora Heisterkamp, Vesa KaartinenAbstract:Aspartylglycosaminuria (AGU) is one of the most common lysosomal storage disorders in humans. A mouse model for AGU has been recently generated through targeted disruption of the glycosylasparaginase gene, and at a young age the glycosyl asparaginase-deficient mice demonstrated many pathological changes found in human AGU patients (Kaartinen V, Mononen I, Voncken J-W, Gonzalez-Gomez I, Heisterkamp N, Groffen J: A mouse model for aspartylglycosaminuria. Nat Med 1996, 2:1375–1378). Our current findings demonstrate that after the age of 10 months, the general condition of null mutant mice gradually deteriorated. They suffered from a progressive motoric impairment and impaired bladder function and died prematurely. A widespread lysosomal hypertrophy in the central nervous system was detected. This neuronal vacuolation was particularly severe in the lateral thalamic nuclei, medullary reticular nuclei, vestibular nuclei, inferior olivary complex, and deep cerebellar nuclei. The oldest animals (20 months old) displayed a clear neuronal loss and gliosis, particularly in those regions, where the most severe vacuolation was found. The severe ataxic gait of the older mice was likely due to the dramatic loss of Purkinje cells, intensive astrogliosis and vacuolation of neurons in the deep cerebellar nuclei, and the severe vacuolation of the cells in vestibular and cochlear nuclei. The impaired bladder function and subsequent hydronephrosis were secondary to involvement of the central nervous system. These findings demonstrate that the glycosylasparaginase-deficient mice share many neuropathological features with human AGU patients, providing a suitable animal model to test therapeutic strategies in the treatment of the central nervous system effects in AGU.
Leena Peltonen - One of the best experts on this subject based on the ideXlab platform.
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a novel Aspartylglucosaminuria mutation affects translocation of aspartylglucosaminidase
Human Mutation, 2004Co-Authors: Jani Saarela, Leena Peltonen, Carina Von Schantz, Anu JalankoAbstract:The AGA gene is mutated in patients with Aspartylglucosaminuria (AGU), a lysosomal storage disease enriched in the Finnish population. The disease mechanism of AGU and the biochemistry and cell biology of the lysosomal aspartylglucosaminidase (AGA) enzyme are well characterized. Here, we have investigated a novel AGU mutation found in a Finnish patient. The mutation was detected as a compound heterozygote with the Finnish major mutation in the other allele. The novel point mutation, c.44T>G, causes the L15R amino acid substitution in the signal sequence of the AGA enzyme. The mutated AGA enzyme was here analyzed by over expression in BHK and COS-1 cells. The L15R AGA protein was only faintly detectable by immunofluorescence analysis and observed in the endoplasmic reticulum. Metabolic labeling and immunoprecipitation revealed only a small amount of AGA polypeptides but the specific activity of the mutant enzyme was surprisingly high, 37% of the wild type. The amino acid substitution probably affects translocation of AGA polypeptides by altering a critical hydrophobic core structure of the signal sequence. It appears that the small amounts of active enzyme are not able to reach the lysosomes thus explaining the development of AGU disease in the patient. © 2004 Wiley-Liss, Inc.
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molecular pathogenesis of a disease structural consequences of Aspartylglucosaminuria mutations
Human Molecular Genetics, 2001Co-Authors: Jani Saarela, Minna Laine, Anu Jalanko, Carina Von Schantz, Carita Oinonen, Juha Rouvinen, Leena PeltonenAbstract:A deficiency of functional aspartylglucosaminidase (AGA) causes a lysosomal storage disease, Aspartylglucosaminuria (AGU). The recessively inherited disease is enriched in the Finnish population, where 98% of AGU alleles contain one founder mutation, AGU Fin . Elsewhere in the world, we and others have described 18 different sporadic AGU mutations. Many of these are predicted to interfere with the complex intracellular maturation and processing of the AGA polypeptide. Proper initial folding of AGA in the endoplasmic reticulum (ER) is dependent on intramolecular disulfide bridge formation and dimerization of two precursor polypeptides. The subsequent activation of AGA occurs autocatalytically in the ER and the protein is transported via the Golgi to the lysosomal compartment using the mannose-6-phosphate receptor pathway. Here we use the three-dimensional structure of AGA to predict structural consequences of AGU mutations, including six novel mutations, and make an effort to characterize every known disease mutation by dissecting the effect of mutations on intracellular stability, maturation, transport and the activity of AGA. Most mutations are substitutions replacing the original amino acid with a bulkier residue. Mutations of the dimer interface prevent dimerization in the ER, whereas active site mutations not only destroy the activity but also affect maturation of the precursor. Depending on their effects on the AGA polypeptide the mutations can be categorized as mild, moderate or severe. These data contribute to the expanding body of knowledge pertaining to molecular pathogenesis of AGU.
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toward understanding the neuronal pathogenesis of Aspartylglucosaminuria expression of aspartylglucosaminidase in brain during development
Molecular Genetics and Metabolism, 1999Co-Authors: Annukka Uusitalo, Matti Haltia, Anu Jalanko, Kai Tenhunen, O Heinonen, Jukka Hiltunen, Mart Saarma, Leena PeltonenAbstract:The deficiency of a lysosomal enzyme, aspartylglucosaminidase, results in a lysosomal storage disorder, Aspartylglucosaminuria, manifesting as progressive mental retardation. To understand tissue pathogenesis and disease progression we analyzed the developmental expression of the enzyme, especially in brain, which is the major source of the pathological symptoms. Highest mRNA levels in brain were detected during embryogenesis, the levels decreased neonatally and started to increase again from Day 7 on. In Western analyses, a defective processing of aspartylglucosaminidase was observed in brain as compared to other tissues, resulting in very low levels of the mature, active form of the enzyme. Interestingly immunohistochemical analyses of mouse brain revealed that aspartylglucosaminidase immunoreactivity closely mimicked the myelin basic protein immunostaining pattern. The only evident neuronal staining was observed in the developing Purkinje cells of the cerebellum from Days 3 to 10, reflecting well the mRNA expression. In human infant brain, the immunostaining was also present in myelinated fibers as well as in the Purkinje cells and, additionally, in the soma and extensions of other neurons. In the adult human brain neurons and oligodendrocytes displayed immunoreactivity whereas myelinated fibers were not stained. Our results of aspartylglucosaminidase immunostaining in myelinated fibers of infant brain might imply the involvement of aspartylglucosaminidase in the early myelination process. This is consistent with previous magnetic resonance imaging findings in the brains of Aspartylglucosaminuria patients, revealing delayed myelination in childhood.
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Prospects of Carrier Screening of Aspartylglucosaminuria in Finland
European Journal of Human Genetics, 1993Co-Authors: Marja Hietala, Kristiina Grön, Ann-christine Syvänen, Leena Peltonen, Pertti AulaAbstract:The frequency of carriers of the AGU_Fin mutation, the predominant mutation causing Aspartylglucosaminuria in Finland, was determined in a population sample comprising 553 newborns from a delivery hospital in southern Finland, and 607 from a hospital in northern Finland. The AGU_Fin point mutation was identified from cord blood samples using the PCR-based, solid-phase minisequencing method. Nineteen carriers of the AGU_Fin mutation were detected, 8 (1:69) in the sample from the southern and 11 (1:55) from the northern population, respectively. The solid-phase minisequencing method proved to be rapid and convenient for the detection of the AGU_Fin mutation, and can readily be applied in large-scale carrier screening at the population level.
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dissection of the molecular pathology of Aspartylglucosaminuria provides the basis for dna diagnostics and future therapeutic interventions
Scandinavian Journal of Clinical & Laboratory Investigation, 1993Co-Authors: Elina Ikonen, Ann-christine Syvänen, Leena PeltonenAbstract:Aspartylglucosaminuria (AGU) is exceptional among lysosomal storage diseases since it represents the only known amidase deficiency in man, being caused by an inadequate function of aspartylglucosaminidase (AGA, E.C. 3.5.1.26.). This amidase is essential in one of the final steps in the ordered breakdown of glycoproteins since it cleaves Asn from the residual N-acetylglucosamines (for reviews see 1, 2). The deficiency of the enzyme activity results in the typical lysosomal accumulation of the abnormal degradation products (mainly aspartylglucosamine, 2-acetamido-1-β-L-aspartamido-1,2-dideoxyglucose) in patients' cells and tissues [3,4]. The diagnosis of AGU has so far been based on the detection of abnormal metabolites in urine and decreased enzyme activity in the cultured fibroblasts or isolated lymphocytes [3,5]. Prenatal diagnosis has been possible by demonstrating the deficient enzyme activity of amniocytes or chorion villus biopsies [6,7]. Identification of carriers has been difficult and unreliable d...
Nathan N Aronson - One of the best experts on this subject based on the ideXlab platform.
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aspartylglycosaminuria biochemistry and molecular biology
Biochimica et Biophysica Acta, 1999Co-Authors: Nathan N AronsonAbstract:Abstract Aspartylglucosaminuria (AGU, McKusick 208400) is an autosomal recessive lysosomal storage disease caused by defective degradation of Asn-linked glycoproteins. AGU mutations occur in the gene (AGA) for glycosylasparaginase, the enzyme necessary for hydrolysis of the protein–oligosaccharide linkage in Asn-linked glycoprotein substrates undergoing metabolic turnover. Loss of glycosylasparaginase activity leads to accumulation of the linkage unit Asn–GlcNAc in tissue lysosomes. Storage of this fragment affects the pathophysiology of neuronal cells most severely. The patients notably suffer from decreased cognitive abilities, skeletal abnormalities and facial grotesqueness. The progress of the disease is slower than in many other lysosomal storage diseases. The patients appear normal during infancy and generally live from 25 to 45 years. A specific AGU mutation is concentrated in the Finnish population with over 200 patients. The carrier frequency in Finland has been estimated to be in the range of 2.5–3% of the population. So far there are 20 other rare family AGU alleles that have been characterized at the molecular level in the world’s population. Recently, two knockout mouse models for AGU have been developed. In addition, the crystal structure of human leukocyte glycosylasparaginase has been determined and the protein has a unique αββα sandwich fold shared by a newly recognized family of important enzymes called N-terminal nucleophile (Ntn) hydrolases. The nascent single-chain precursor of glycosylase araginase self-cleaves into its mature α- and β-subunits, a reaction required to activate the enzyme. This interesting biochemical feature is also shared by most of the Ntn-hydrolase family of proteins. Many of the disease-causing mutations prevent proper folding and subsequent activation of the glycosylasparaginase.
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lysosomal storage disease aspartylglycosaminuria
1997Co-Authors: Nathan N Aronson, Ilkka ManonenAbstract:This is a review of aspartylglycosaminuria (AGU), which is one of the most common lysosomal diseases worldwide. It gives an overview of the disease from its discovery and early history to recent developments. It also provides detailed reference material for clinical specialists and researchers working in the field of inborn errors of metabolism, in particular on lysosomal diseases.
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aspartylglycosaminuria protein chemistry and molecular biology of the most common lysosomal storage disorder of glycoprotein degradation
The FASEB Journal, 1993Co-Authors: Ilkka Mononen, Vesa Kaartinen, Krishna J Fisher, Nathan N AronsonAbstract:Aspartylglycosaminuria (AGU) (McKusick 20840) is the most common disorder of glycoprotein degradation caused by the failure of lysosomes to digest the protein-to-carbohydrate linkage of Asn-linked ...
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deletion of exon 8 causes glycosylasparaginase deficiency in an african american Aspartylglucosaminuria agu patient
FEBS Letters, 1991Co-Authors: Krishna J Fisher, Nathan N AronsonAbstract:Abstract We have indentified a G T-to- T T transversion at the splice donor site of intron 8 in the glycosylasparaginase gene from an African American Aspartylglucosaminuria (AGU) patient, This mutation causes abnormal splicing of glycosylasparaginase pre-mRNA by joining exon 7 to 9 and excluding 134 bp exon 8. The effect of the mutation is compounded by a frame shift that occurs after the deletion site resulting in premature translational termination. The truncated AGU protein was neither catalytically active nor processed into mature α and β subunits. Both this and a previously characterized Finnish AGU mutation appear to affect folding of the single-chain precursor of glycosylasparaginase and thereby prevent transport of the enzyme to lysosomes.
Vesa Kaartinen - One of the best experts on this subject based on the ideXlab platform.
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enzyme replacement therapy in a mouse model of aspartylglycosaminuria
The FASEB Journal, 2000Co-Authors: Ulla Dunder, Vesa Kaartinen, Pirjo Valtonen, Eira Vaananen, John Groffen, Nora Heisterkamp, Veli-matti Kosma, Ilkka MononenAbstract:Aspartylglycosaminuria (AGU), the most common lysosomal disorder of glycoprotein degradation, is caused by deficient activity of glycosylasparaginase (AGA). AGA-deficient mice share most of the clinical, biochemical and histopathologic characteristics of human AGU disease. In the current study, recombinant human AGA administered i.v. to adult AGU mice disappeared from the systemic circulation of the animals in two phases predominantly into non-neuronal tissues, which were rapidly cleared from storage compound aspartylglucosamine. Even a single AGA injection reduced the amount of aspartylglucosamine in the liver and spleen of AGU mice by 90% and 80%, respectively. Quantitative biochemical analyses along with histological and immunohistochemical studies demonstrated that the pathophysiologic characteristics of AGU were effectively corrected in non-neuronal tissues of AGU mice during 2 wk of AGA therapy. At the same time, AGA activity increased to 10% of that in normal brain tissue and the accumulation of as...
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progressive neurodegeneration in aspartylglycosaminuria mice
American Journal of Pathology, 1998Co-Authors: Ignacio Gonzalezgomez, Ilkka Mononen, John Groffen, Nora Heisterkamp, Vesa KaartinenAbstract:Aspartylglycosaminuria (AGU) is one of the most common lysosomal storage disorders in humans. A mouse model for AGU has been recently generated through targeted disruption of the glycosylasparaginase gene, and at a young age the glycosyl asparaginase-deficient mice demonstrated many pathological changes found in human AGU patients (Kaartinen V, Mononen I, Voncken J-W, Gonzalez-Gomez I, Heisterkamp N, Groffen J: A mouse model for aspartylglycosaminuria. Nat Med 1996, 2:1375–1378). Our current findings demonstrate that after the age of 10 months, the general condition of null mutant mice gradually deteriorated. They suffered from a progressive motoric impairment and impaired bladder function and died prematurely. A widespread lysosomal hypertrophy in the central nervous system was detected. This neuronal vacuolation was particularly severe in the lateral thalamic nuclei, medullary reticular nuclei, vestibular nuclei, inferior olivary complex, and deep cerebellar nuclei. The oldest animals (20 months old) displayed a clear neuronal loss and gliosis, particularly in those regions, where the most severe vacuolation was found. The severe ataxic gait of the older mice was likely due to the dramatic loss of Purkinje cells, intensive astrogliosis and vacuolation of neurons in the deep cerebellar nuclei, and the severe vacuolation of the cells in vestibular and cochlear nuclei. The impaired bladder function and subsequent hydronephrosis were secondary to involvement of the central nervous system. These findings demonstrate that the glycosylasparaginase-deficient mice share many neuropathological features with human AGU patients, providing a suitable animal model to test therapeutic strategies in the treatment of the central nervous system effects in AGU.
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aspartylglycosaminuria protein chemistry and molecular biology of the most common lysosomal storage disorder of glycoprotein degradation
The FASEB Journal, 1993Co-Authors: Ilkka Mononen, Vesa Kaartinen, Krishna J Fisher, Nathan N AronsonAbstract:Aspartylglycosaminuria (AGU) (McKusick 20840) is the most common disorder of glycoprotein degradation caused by the failure of lysosomes to digest the protein-to-carbohydrate linkage of Asn-linked ...
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a fluorometric assay for glycosylasparaginase activity and detection of aspartylglycosaminuria
Analytical Biochemistry, 1993Co-Authors: Ilkka Mononen, Vesa Kaartinen, Julian C. WilliamsAbstract:Abstract Recent experimental work on the mechanism of action of glycosylasparaginase suggests that the enzyme specifically reacts toward the L-asparagine or L-aspartic acid moiety of its substrates. Based on this, a new sensitive assay for glycosylasparaginase activity has been developed using L-aspartic acid β-(7-amido-4-methylcoumarin) as substrate. Release of 7-amino-4-methylcoumarin was determined fluorometrically. At pH 7.5, Km = 93 μM, and as little as 1 ng of glycosylasparaginase could be detected with the assay. Hydrolysis of the substrate was inhibited by diazo-oxonorvaline, a specific inhibitor of glycosylasparaginase. In biological samples, the fluorometric assay is 40-100 times more sensitive than other published methods for glycosylasparaginase. This new assay enables a rapid enzymatic diagnosis of aspartylglycosaminuria-a genetic deficiency of glycosylasparaginase activity-with leukocyte and fibroblast samples.
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aspartylglycosaminuria in the finnish population identification of two point mutations in the heavy chain of glycoasparaginase
Proceedings of the National Academy of Sciences of the United States of America, 1991Co-Authors: Ilkka Mononen, Vesa Kaartinen, Nora Heisterkamp, Julian C. Williams, John R Yates, Patrick R Griffin, Leroy Hood, John GroffenAbstract:Abstract Aspartylglycosaminuria is an inherited lysosomal storage disease caused by deficiency of glycoasparaginase (EC 3.5.1.26) and occurs with higher frequency among Finns than other populations. We have purified human glycoasparaginase and determined about 90% of the amino acid sequence of its light subunit and greater than 70% of that of its heavy subunit by Edman degradation and mass spectrometry. Additional sequence data were obtained from the cloning and subsequent nucleotide analysis of a cDNA corresponding to the normal human glycoasparaginase gene. The enzyme is encoded by a single mRNA as a single polypeptide that is posttranslationally processed to generate the subunits and is glycosylated. After preparing first-strand cDNA from leukocyte and fibroblast total RNA, we used the polymerase chain reaction to amplify the glycoasparaginase cDNA of eight Finnish aspartylglycosaminuria patients. We demonstrate that the Finnish patients' mRNA sequence differed from the normal sequence by two single-base changes six nucleotides apart from one another in the heavy chain of glycoasparaginase. The first change resulted in the replacement of arginine by glutamine (R161Q), whereas the second change resulted in a cysteine to serine substitution (C163S). Both mutations resulted in novel restriction endonuclease sites and were present in all eight Finnish aspartylglycosaminuria patients originating from different pedigrees, but they were absent from Finnish and non-Finnish controls and a non-Finnish case of aspartylglycosaminuria. These results indicate molecular homogeneity in aspartylglycosaminuria alleles in the Finnish population.
John Groffen - One of the best experts on this subject based on the ideXlab platform.
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enzyme replacement therapy in a mouse model of aspartylglycosaminuria
The FASEB Journal, 2000Co-Authors: Ulla Dunder, Vesa Kaartinen, Pirjo Valtonen, Eira Vaananen, John Groffen, Nora Heisterkamp, Veli-matti Kosma, Ilkka MononenAbstract:Aspartylglycosaminuria (AGU), the most common lysosomal disorder of glycoprotein degradation, is caused by deficient activity of glycosylasparaginase (AGA). AGA-deficient mice share most of the clinical, biochemical and histopathologic characteristics of human AGU disease. In the current study, recombinant human AGA administered i.v. to adult AGU mice disappeared from the systemic circulation of the animals in two phases predominantly into non-neuronal tissues, which were rapidly cleared from storage compound aspartylglucosamine. Even a single AGA injection reduced the amount of aspartylglucosamine in the liver and spleen of AGU mice by 90% and 80%, respectively. Quantitative biochemical analyses along with histological and immunohistochemical studies demonstrated that the pathophysiologic characteristics of AGU were effectively corrected in non-neuronal tissues of AGU mice during 2 wk of AGA therapy. At the same time, AGA activity increased to 10% of that in normal brain tissue and the accumulation of as...
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progressive neurodegeneration in aspartylglycosaminuria mice
American Journal of Pathology, 1998Co-Authors: Ignacio Gonzalezgomez, Ilkka Mononen, John Groffen, Nora Heisterkamp, Vesa KaartinenAbstract:Aspartylglycosaminuria (AGU) is one of the most common lysosomal storage disorders in humans. A mouse model for AGU has been recently generated through targeted disruption of the glycosylasparaginase gene, and at a young age the glycosyl asparaginase-deficient mice demonstrated many pathological changes found in human AGU patients (Kaartinen V, Mononen I, Voncken J-W, Gonzalez-Gomez I, Heisterkamp N, Groffen J: A mouse model for aspartylglycosaminuria. Nat Med 1996, 2:1375–1378). Our current findings demonstrate that after the age of 10 months, the general condition of null mutant mice gradually deteriorated. They suffered from a progressive motoric impairment and impaired bladder function and died prematurely. A widespread lysosomal hypertrophy in the central nervous system was detected. This neuronal vacuolation was particularly severe in the lateral thalamic nuclei, medullary reticular nuclei, vestibular nuclei, inferior olivary complex, and deep cerebellar nuclei. The oldest animals (20 months old) displayed a clear neuronal loss and gliosis, particularly in those regions, where the most severe vacuolation was found. The severe ataxic gait of the older mice was likely due to the dramatic loss of Purkinje cells, intensive astrogliosis and vacuolation of neurons in the deep cerebellar nuclei, and the severe vacuolation of the cells in vestibular and cochlear nuclei. The impaired bladder function and subsequent hydronephrosis were secondary to involvement of the central nervous system. These findings demonstrate that the glycosylasparaginase-deficient mice share many neuropathological features with human AGU patients, providing a suitable animal model to test therapeutic strategies in the treatment of the central nervous system effects in AGU.
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recombinant glycosylasparaginase and in vitro correction of aspartylglycosaminuria
The FASEB Journal, 1995Co-Authors: Ilkka Mononen, Ulla Dunder, Eeva-liisa Romppanen, T Noronkoski, Ilpo Kuronen, Nora Heisterkamp, John GroffenAbstract:Aspartylglycosaminuria (AGU) is the most common disorder of glycoprotein degradation. AGU patients are deficient in glycosylasparaginase (GA), which results in accumulation of aspartylglucosamine in body fluids and tissues. Human glycosylasparaginase was stably overexpressed in NIH-3T3 mouse fibroblasts, in which the unusual posttranslational processing and maturation of the enzyme occurred in a high degree. The recombinant enzyme was isolated as two isoforms, which were both phosphorylated, and actively transported into AGU fibroblasts and lymphoblasts through mannose-6-phosphate receptor-mediated endocytosis. The rate of uptake into fibroblasts was half-maximal when the concentration of GA in the medium was 5 x 10(-8) M. Immunofluorescence microscopy suggested compartmentalization of the recombinant enzyme in the lysosomes. Supplementation of culture medium with either isoform cleared AGU lymphoblasts of stored aspartylglucosamine when glycosylasparaginase activity in the cells reached 3-4% of that in n...
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aspartylglycosaminuria in a non finnish patient caused by a donor splice mutation in the glycoasparaginase gene
Journal of Biological Chemistry, 1992Co-Authors: I Mononen, Tarja Mononen, N Heisterkamp, V Kaartinen, J C Williams, John GroffenAbstract:Abstract Aspartylglycosaminuria is a lysosomal storage disease caused by deficient activity of glycoasparaginase (EC 3.5.1.26), and it occurs with a high frequency among Finns. We have recently shown that the molecular defect in all Finnish aspartylglycosaminuria patients examined to date consists of two single base changes in the heavy chain of glycoasparaginase (Mononen, I., Heisterkamp, N., Kaartinen, V., Williams, J. C., Yates, J. R., III, Griffin, P. R., Hood, L. E., and Groffen, J. (1991) Proc. Natl. Acad. Sci U.S.A. 88, 2941-2945). This is the first report on the identification of the molecular defect causing aspartylglycosaminuria in a patient of non-Finnish origin. Total RNA from fibroblasts of a black American aspartylglycosaminuria patient was isolated, first-strand cDNA was synthesized, and the cDNA encoding glycoasparaginase was amplified by the polymerase chain reaction. The patient's mRNA nucleotide sequence was different from the normal sequence by a deletion of 134 nucleotides at positions 807-940. Nucleotide sequence analysis of the normal glycoasparaginase gene demonstrated that the deletion corresponded precisely to a 134-base pair exon. Moreover, analysis of the splice sites demonstrated a single base change, G to T, that altered the donor splice site of the exon deleted in the patient's mRNA. This change led to an exon-skipping event resulting in a frame shift and generation of a stop codon.
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aspartylglycosaminuria in the finnish population identification of two point mutations in the heavy chain of glycoasparaginase
Proceedings of the National Academy of Sciences of the United States of America, 1991Co-Authors: Ilkka Mononen, Vesa Kaartinen, Nora Heisterkamp, Julian C. Williams, John R Yates, Patrick R Griffin, Leroy Hood, John GroffenAbstract:Abstract Aspartylglycosaminuria is an inherited lysosomal storage disease caused by deficiency of glycoasparaginase (EC 3.5.1.26) and occurs with higher frequency among Finns than other populations. We have purified human glycoasparaginase and determined about 90% of the amino acid sequence of its light subunit and greater than 70% of that of its heavy subunit by Edman degradation and mass spectrometry. Additional sequence data were obtained from the cloning and subsequent nucleotide analysis of a cDNA corresponding to the normal human glycoasparaginase gene. The enzyme is encoded by a single mRNA as a single polypeptide that is posttranslationally processed to generate the subunits and is glycosylated. After preparing first-strand cDNA from leukocyte and fibroblast total RNA, we used the polymerase chain reaction to amplify the glycoasparaginase cDNA of eight Finnish aspartylglycosaminuria patients. We demonstrate that the Finnish patients' mRNA sequence differed from the normal sequence by two single-base changes six nucleotides apart from one another in the heavy chain of glycoasparaginase. The first change resulted in the replacement of arginine by glutamine (R161Q), whereas the second change resulted in a cysteine to serine substitution (C163S). Both mutations resulted in novel restriction endonuclease sites and were present in all eight Finnish aspartylglycosaminuria patients originating from different pedigrees, but they were absent from Finnish and non-Finnish controls and a non-Finnish case of aspartylglycosaminuria. These results indicate molecular homogeneity in aspartylglycosaminuria alleles in the Finnish population.
