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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. The disease is caused by the deficient activity of the lysosomal enzyme glycosylasparaginase (aspartylglucosaminidase, AGA), which leads to a disorder in the degradation of glycoasparagines – aspartylglucosamine or other glycoconjugates with an aspartylglucosamine moiety at their reducing end – and accumulation of these undegraded glycoasparagines in tissues and body fluids. A single nucleotide change in the AGA gene resulting in a cysteine to serine substitution (C163S) in the AGA enzyme protein causes the deficiency of the glycosylasparaginase activity in the Finnish population. Homozygosity for the single nucleotide change causing the C163S mutation is responsible for 98% of the AGU cases in Finland simplifying the carrier detection and prenatal diagnosis of the disorder in the Finnish population. A mouse strain, which completely lacks the Aga activity has been generated through targeted disruption of the Aga gene in embryonic stem cells. These Aga -deficient mice share most of the clinical, histopathologic and biochemical characteristics of human AGU disease. Treatment of AGU mice with recombinant AGA resulted in rapid correction of the pathophysiologic characteristics of AGU in non-neuronal tissues of the animals. The accumulation of aspartylglucosamine was reduced by up to 40% in the brain tissue of the animals depending on the age of the animals and the therapeutic protocol. Enzyme replacement trials on human AGU patients have not been reported so far. Allogenic stem cell transplantation has not proved effective in curing AGU.
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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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Early initiation of enzyme replacement therapy improves metabolic correction in the brain tissue of Aspartylglycosaminuria mice
Journal of Inherited Metabolic Disease, 2010Co-Authors: Ulla Dunder, Pirjo Valtonen, Eira Kelo, Ilkka MononenAbstract:Aspartylglycosaminuria (AGU) is a lysosomal storage disease caused by deficient activity of glycosylasparaginase (AGA), and characterized by motor and mental retardation. Enzyme replacement therapy (ERT) in adult AGU mice with AGA removes the accumulating substance aspartylglucosamine from and reverses pathology in many somatic tissues, but has only limited efficacy in the brain tissue of the animals. In the current work, ERT of AGU mice was initiated at the age of 1 week with three different dosage schedules of recombinant glycosylasparaginase. The animals received either 3.4 U of AGA/kg every second day for 2 weeks (Group 1), 1.7 U/kg every second day for 9 days followed by an enzyme injection once a week for 4 weeks (Group 2) or 17 U/kg at the age of 7 and 9 days (Group 3). In the Group 1 and Group 3 mice, ERT reduced the amount of aspartylglucosamine by 34 and 41% in the brain tissue, respectively. No therapeutic effect was observed in the brain tissue of Group 2 mice. As in the case of adult AGU mice, the AGA therapy was much more effective in the somatic tissues than in the brain tissue of the newborn AGU mice. The combined evidence demonstrates that a high dose ERT with AGA in newborn AGU mice is up to twofold more effective in reducing the amount of the accumulated storage material from the brain tissue than ERT in adult AGU animals, indicating the importance of early detection and treatment of the disease.
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Massive accumulation of Man2GlcNAc2-Asn in nonneuronal tissues of glycosylasparaginase-deficient mice and its removal by enzyme replacement therapy.
Glycobiology, 2004Co-Authors: Eira Kelo, Ulla Dunder, Ilkka MononenAbstract:Aspartylglycosaminuria (AGU) is caused by deficient enzymatic 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)-bD-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 especially 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 GlcNAcAsn. In contrast to GlcNAc-Asn, the storage of Man2GlcNAc2-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.
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human leukocyte glycosylasparaginase cell to cell transfer and properties in correction of Aspartylglycosaminuria
FEBS Letters, 2001Co-Authors: Ulla Dunder, Ilkka MononenAbstract:Aspartylglycosaminuria (AGU), a severe lysosomal storage disease, is caused by the deficiency of the lysosomal enzyme, glycosylasparaginase (GA), and accumulation of aspartylglucosamine (GlcNAc-Asn) in tissues. Here we show that human leukocyte glycosylasparaginase can correct the metabolic defect in Epstein–Barr virus (EBV)-transformed AGU lymphocytes rapidly and effectively by mannose-6-phosphate receptor-mediated endocytosis or by contact-mediated cell-to-cell transfer from normal EBV-transformed lymphocytes, and that 2–7% of normal activity is sufficient to correct the GlcNAc-Asn metabolism in the cells. Cell-to-cell contact is obligatory for the transfer of GA since normal transformed lymphocytes do not excrete GA into extracellular medium. The combined evidence indicates that cell-to-cell transfer of GA plays a main role in enzyme replacement therapy of AGU by normal lymphocytes.
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, Nora Heisterkamp, John Groffen, Pirjo Valtonen, Eira Vaananen, Velimatti 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, Nora Heisterkamp, John Groffen, 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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A mouse model for the human lysosomal disease Aspartylglycosaminuria
Nature Medicine, 1996Co-Authors: Vesa Kaartinen, Ilkka Mononen, Nora Heisterkamp, Jan Willem Voncken, Tiina Noronkoski, Ignacio Gonzalez-gomez, John GroffenAbstract:Aspartylglycosaminuria (AGU), the most common disorder of glycoprotein degradation in humans, is caused by mutations in the gene encoding the lysosomal enzyme glycosylasparaginase (Aga)^1. The resulting enzyme deficiency allows aspartylglucosamine (GlcNAc–Asn) and other glycoasparagines to accumulate in tissues and body fluids, from early fetal life onward^1. The clinical course is characterized by normal early development, slowly progressing to severe mental and motor retardation in early adulthood^2,3. The exact pathogenesis of AGU in humans is unknown and neither therapy nor an animal model for this debilitating and ultimately fatal disease exists. Through targeted disruption of the mouse Aga gene in embryonic stem cells, we generated mice that completely lack Aga activity. At the age of 5–10 months a massive accumulation of GlcNAc–Asn was detected along with lysosomal vacuolization, axonal swelling in the gracile nucleus and impaired neuromotor coordination. A significant number of older male mice had massively swollen bladders, which was not caused by obstruction, but most likely related to the impaired function of the nervous system. These findings are consistent with the pathogenesis of AGU and provide further data explaining the impaired neurological function in AGU patients.
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localization of the disulfide bond involved in post translational processing of glycosylasparaginase and disrupted by a mutation in the finnish type Aspartylglycosaminuria
Journal of Biological Chemistry, 1995Co-Authors: Ashley L Mccormack, Ilkka Mononen, Vesa Kaartinen, John R YatesAbstract:Abstract The heavy chain of human glycosylasparaginase (N4-(β-N-acetylglucosaminyl)-L-asparaginase (EC 3.5.1.26)) has five cysteinyl residues (Cys-61, Cys-64, Cys-69, Cys-163, and Cys-179). A Cys-163 to serine substitution due to a point mutation in the glycosylasparaginase gene causes the most common disorder of glycoprotein degradation, the Finnish-type Aspartylglycosaminuria. To localize the potential disulfide bonds, the isolated heavy chain of human leukocyte glycosylasparaginase was treated with the enzyme α-chymotrypsin, and the resulting peptides were separated by high performance liquid chromatography prior to and after reduction and S-carboxymethylation. The peptide containing the Cys-163 residue and the peptide to which it is connected with a disulfide were structurally characterized by mass spectrometry. The disulfide bond crucial for catalytic activity, subunit processing, and biological transport of glycosylasparaginase was located close to the carboxyl terminus of the heavy chain at positions 163 and 179.
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enzymatic diagnosis of Aspartylglycosaminuria by fluorometric assay of glycosylasparaginase in serum plasma or lymphocytes
Clinical Chemistry, 1994Co-Authors: Ilkka Mononen, Vesa Kaartinen, Tarja Mononen, Paivi Ylikangas, Kari SavolainenAbstract:Serum, plasma, and lymphocytes from Aspartylglycosaminuria (AGU) patients and carriers and from normal controls were incubated with a fluorescent glycosylasparaginase substrate, L-aspartic acid beta-(7-amido-4-methylcoumarin), and the release of 7-amino-4-methylcoumarin was measured fluorometrically after incubation for 1-4 h. The mean glycosylasparaginase (EC 3.5.1.26) activity in normal serum, plasma, and lymphocytes was 20.2 (SD 5.0) mU/L (n = 24), 17.5 (SD 5.0) mU/L (n = 24), and 242 (SD 108) mU/g protein (n = 17), respectively. The corresponding values in the Finnish AGU patients were 0.7 (SD 0.4) mU/L (n = 10), 0.3 (SD 0.3) mU/L (n = 10), and 6.0 (SD 4.6) mU/g protein (n = 7). No overlapping values were obtained between the AGU patients and the carriers in any of the samples, but the values between the carriers and controls were overlapping in 28 of 29 serum, 22 of 29 plasma, and 4 of 21 lymphocyte samples. Thus, the fluorometric glycosylasparaginase assay in various blood samples allows specific detection of the enzyme defect in AGU, but cannot be used for reliable detection of carriers of the disease.
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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Glycosylation and Phosphorylation of Lysosomal Glycosylasparaginase
Archives of Biochemistry and Biophysics, 1996Co-Authors: Hyejeong Park, Michelle Vettese-dadey, Nathan N AronsonAbstract:Abstract Glycosylasparaginase (EC 3.5.1.26) is a lysosomal amidase which hydrolyzes the bond between asparagine and the sugar moiety in N-linked glycoproteins. Deficiency of the enzyme results in Aspartylglycosaminuria (AGU), the most common disorder of glycoprotein degradation. Mature enzyme is formed by two proteolytic cleavage steps subsequent to removal of its signal peptide: (1) an activation cleavage in the ER of the initial single-chain 49-kDa polypeptide into a 27-kDa α- and 19-kDa β-subunit; (2) a cleavage in lysosomes which removes 10 amino acids from the C-terminus of the α-subunit without affecting enzyme activity. Each subunit of glycosylasparaginase contains one N-linked oligosaccharide (N38, α-subunit; N308, β-subunit). Both oligosaccharides were phosphorylated and releasable by Endo-H digestion, indicating they were of the high-mannose type. These glycosylation sequenons were mutagenized to determine the role of the oligosaccharide at each site in proper folding and transport of glycosylasparaginase. An N38D mutant underwent the lysosomal processing step, indicating that targeting to lysosomes can be via the phosphorylated β-subunit oligosaccharide alone. Deletion of the β-subunit oligosaccharide at N308 by an aspartic acid substitution resulted in very little protein or enzyme activity in the transfected cells, reemphasizing that glycosylation of the β-subunit site is important for efficient folding and/or targeting. A different mutation to eliminate the same N-glycosylation sequenon (T310A) yielded more protein and enzyme activity, and a double mutant N38D/T310A yielded the same results as the single β-subunit substitution. Yield of enzyme for all mutants was increased in cells treated with brefeldin A. The N308 glycosylation site of the β-subunit appears to be more important in maintaining normal transport and stability of human glycosylasparaginase.
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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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characterization of three alleles causing Aspartylglycosaminuria two from a british family and one from an american patient
Biochemical Journal, 1993Co-Authors: Hyejeong Park, Krishna J Fisher, A. H. Fensom, M B Vettese, Nathan N AronsonAbstract:Aspartylglycosaminuria (AGU) is a lysosomal storage disease principally occurring in Finland that results from mutations in the structural gene for glycosylasparaginase (AGU). This work characterizes the inheritance of two previously reported AGU mutations in a British patient [Ikonen, Aula, Gron, Tollersrud, Halila, Manninen, Syvanen and Peltonen (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 11222-11226]. Use of the PCR determined the glycosylasparaginase cDNA sequence from both parents of the British patient and his AGU-affected brother. The father of the British AGU-affected siblings was found to be a heterozygote carrier for a C-->T point mutation which causes an Ala-->Val amino-acid substitution, while the mother was heterozygous for a 7 bp deletion that results in premature translational termination. The brother of the previously studied patient was similarly shown to be a compound heterozygote. Expression in COS-1 cells revealed the paternal Ala-->Val amino-acid substitution destroyed glycosylasparaginase catalytic activity, prevented transport of the mutant protein to the lysosome, and prevented maturation of the enzyme precursor to its native subunit structure. The Ala-->Val mutation therefore affects glycosylasparaginase in a manner similar to the Finnish AGU Cys-->Ser substitution, further supporting a linkage of glycosylasparaginase catalytic activity to its lysosomal transport and subunit processing [Fisher and Aronson (1991) J. Biol. Chem. 266, 12105-12113]. In addition, a 5 bp deletion mutation from an American patient with AGU has been characterized. The deleted sequence occurs at the beginning of the glycosylasparaginase coding sequence, resulting in an extremely truncated polypeptide. The American 5 bp deletion and the British maternal 7 bp deletion possibly decrease mRNA stability.
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, Nora Heisterkamp, John Groffen, Pirjo Valtonen, Eira Vaananen, Velimatti 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, Nora Heisterkamp, John Groffen, 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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A mouse model for the human lysosomal disease Aspartylglycosaminuria
Nature Medicine, 1996Co-Authors: Vesa Kaartinen, Ilkka Mononen, Nora Heisterkamp, Jan Willem Voncken, Tiina Noronkoski, Ignacio Gonzalez-gomez, John GroffenAbstract:Aspartylglycosaminuria (AGU), the most common disorder of glycoprotein degradation in humans, is caused by mutations in the gene encoding the lysosomal enzyme glycosylasparaginase (Aga)^1. The resulting enzyme deficiency allows aspartylglucosamine (GlcNAc–Asn) and other glycoasparagines to accumulate in tissues and body fluids, from early fetal life onward^1. The clinical course is characterized by normal early development, slowly progressing to severe mental and motor retardation in early adulthood^2,3. The exact pathogenesis of AGU in humans is unknown and neither therapy nor an animal model for this debilitating and ultimately fatal disease exists. Through targeted disruption of the mouse Aga gene in embryonic stem cells, we generated mice that completely lack Aga activity. At the age of 5–10 months a massive accumulation of GlcNAc–Asn was detected along with lysosomal vacuolization, axonal swelling in the gracile nucleus and impaired neuromotor coordination. A significant number of older male mice had massively swollen bladders, which was not caused by obstruction, but most likely related to the impaired function of the nervous system. These findings are consistent with the pathogenesis of AGU and provide further data explaining the impaired neurological function in AGU patients.
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recombinant glycosylasparaginase and in vitro correction of Aspartylglycosaminuria
The FASEB Journal, 1995Co-Authors: Ilkka Mononen, Nora Heisterkamp, Ulla Dunder, E L Romppanen, T Noronkoski, I Kuronen, 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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Chromosomal localization of the human glycoasparaginase gene to 4q32-q33.
Human Genetics, 1992Co-Authors: Christine M. Morris, Julian C Williams, Nora Heisterkamp, John Groffen, Ilkka MononenAbstract:Glycoasparaginase cleaves the N-glycosidic linkage between asparagine and N-acetylglucosamine in the degradation of glycoproteins. In humans, a deficient activity of glycoasparaginase results in accumulation of glycoasparagines, causing the lysosomal storage disease Aspartylglycosaminuria. Recombinant plasmid containing the cDNA insert encoding human glycoasparaginase was used to localize the enzyme to chromosome 4q32–q33 by in situ hybridization to metaphase chromosomes prepared from normal human lymphocytes.
Nora Heisterkamp - 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, Nora Heisterkamp, John Groffen, Pirjo Valtonen, Eira Vaananen, Velimatti 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, Nora Heisterkamp, John Groffen, 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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A mouse model for the human lysosomal disease Aspartylglycosaminuria
Nature Medicine, 1996Co-Authors: Vesa Kaartinen, Ilkka Mononen, Nora Heisterkamp, Jan Willem Voncken, Tiina Noronkoski, Ignacio Gonzalez-gomez, John GroffenAbstract:Aspartylglycosaminuria (AGU), the most common disorder of glycoprotein degradation in humans, is caused by mutations in the gene encoding the lysosomal enzyme glycosylasparaginase (Aga)^1. The resulting enzyme deficiency allows aspartylglucosamine (GlcNAc–Asn) and other glycoasparagines to accumulate in tissues and body fluids, from early fetal life onward^1. The clinical course is characterized by normal early development, slowly progressing to severe mental and motor retardation in early adulthood^2,3. The exact pathogenesis of AGU in humans is unknown and neither therapy nor an animal model for this debilitating and ultimately fatal disease exists. Through targeted disruption of the mouse Aga gene in embryonic stem cells, we generated mice that completely lack Aga activity. At the age of 5–10 months a massive accumulation of GlcNAc–Asn was detected along with lysosomal vacuolization, axonal swelling in the gracile nucleus and impaired neuromotor coordination. A significant number of older male mice had massively swollen bladders, which was not caused by obstruction, but most likely related to the impaired function of the nervous system. These findings are consistent with the pathogenesis of AGU and provide further data explaining the impaired neurological function in AGU patients.
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recombinant glycosylasparaginase and in vitro correction of Aspartylglycosaminuria
The FASEB Journal, 1995Co-Authors: Ilkka Mononen, Nora Heisterkamp, Ulla Dunder, E L Romppanen, T Noronkoski, I Kuronen, 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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Chromosomal localization of the human glycoasparaginase gene to 4q32-q33.
Human Genetics, 1992Co-Authors: Christine M. Morris, Julian C Williams, Nora Heisterkamp, John Groffen, Ilkka MononenAbstract:Glycoasparaginase cleaves the N-glycosidic linkage between asparagine and N-acetylglucosamine in the degradation of glycoproteins. In humans, a deficient activity of glycoasparaginase results in accumulation of glycoasparagines, causing the lysosomal storage disease Aspartylglycosaminuria. Recombinant plasmid containing the cDNA insert encoding human glycoasparaginase was used to localize the enzyme to chromosome 4q32–q33 by in situ hybridization to metaphase chromosomes prepared from normal human lymphocytes.
