|
PWS Articles PWS Research
Other |
[ Printable Page | Edit ]
Research Notes: Alpha-mannosidosisSee also: Congenital disorders of glycosylation
Immunity. 2007 Aug. Autoimmune diseases are prevalent and often life-threatening syndromes, yet the pathogenic triggers and mechanisms involved remain mostly unresolved. Protein asparagine linked- (N-) glycosylation produces glycan structures that substantially differ among the extracellular compartments of evolutionarily divergent organisms. Alpha-mannosidase-II (alphaM-II) deficiency diminishes complex-type N-glycan branching in vertebrates and induces an autoimmune disease in mice similar to human systemic lupus erythematosus. We found that disease pathogenesis provoking glomerulonephritis and kidney failure was nonhematopoietic in origin, independent of complement C3 and the adaptive immune system, mitigated by intravenous administration of immunoglobulin-G, and linked to chronic activation of the innate immune system. N-glycans produced in alphaM-II deficiency bear immune-stimulatory mannose-dependent ligands for innate immune lectin receptors, disrupting the phylogenic basis of this glycomic recognition mechanism. Thus, mammalian N-glycan branching safeguards against the formation of an endogenous immunologic signal of nonself that can provoke a sterile inflammatory response in the pathogenesis of autoimmune disease. J Biol Chem. 2007 Jan 26. There are three mammalian Golgi alpha1,2-mannosidases, encoded by different genes, that form Man5GlcNAc2 from Man(8-9)GlcNAc2 for the biosynthesis of hybrid and complex N-glycans. Northern blot analysis and in situ hybridization indicate that the three paralogs display distinct developmental and tissue-specific expression. The physiological role of Golgi alpha1,2-mannosidase IB was investigated by targeted gene ablation. The null mice have normal gross appearance at birth, but they display respiratory distress and die within a few hours. Histology of fetal lungs the day before birth indicate some delay in development, whereas neonatal lungs show extensive pulmonary hemorrhage in the alveolar region. No significant histopathological changes occur in other tissues. No remarkable ultrastructural differences are detected between wild type and null lungs. The membranes of a subset of bronchiolar epithelial cells are stained with lectins from Phaseolus vulgaris (leukoagglutinin and erythroagglutinin) and Datura stramonium in wild type lungs, but this staining disappears in lungs from null mice. Mass spectrometry of N-glycans from different tissues shows no significant changes in global N-glycans of null mice. Therefore, only a few glycoproteins required for normal lung function depend on alpha1,2-mannosidase IB for maturation. There are no apparent differences in the expression of several lung epithelial cell and endothelial cell markers between null and wild type mice. The alpha1,2-mannosidase IB null phenotype differs from phenotypes caused by ablation of other enzymes in N-glycan biosynthesis and from other mouse gene disruptions that affect pulmonary development and function. Clin Chim Acta. 2007 Jan. Alpha-mannosidosis is a recessively inherited disorder due to the deficiency of the lysosomal alpha-mannosidase. We report the molecular analysis performed in two patients with the late onset form of alpha-mannosidosis. Four new alleles were identified: three missense mutations involving highly conserved residues, c.597 C>A (p.H200N), c.1553 T>C (p.L518P) and c.2746 C>A (p.R916S) and a single nucleotide deletion, c.2660delC. In vitro expression studies in COS-1 cells demonstrated that pH200N, p.L518P and p.R916S proteins are expressed but retained no residual enzyme activity. These data are supported by structural 3D analysis which predicted that both p.L518P and p.R916S could affect the interaction of the small E-domain with the active site domain or the main body of the structure while the pH200N might alter substrate binding or other catalytic properties. Finally, the c.2660delC causes a frameshift introducing a premature stop codon (p.T887SfsX45), presuming to be a severe mutation. Biochem J. 2006 Nov 15. The endoplasmic-reticulum-associated degradation of misfolded (glyco)proteins ensures that only functional, correctly folded proteins exit from the endoplasmic reticulum and that misfolded ones are degraded by the ubiquitin-proteasome system. During the degradation of misfolded glycoproteins, they are deglycosylated by the PNGase (peptide:N-glycanase). The free oligosaccharides released by PNGase are known to be further catabolized by a cytosolic alpha-mannosidase, although the gene encoding this enzyme has not been identified unequivocally. The findings in the present study demonstrate that an alpha-mannosidase, Man2C1, is involved in the processing of free oligosaccharides that are formed in the cytosol. When the human Man2C1 orthologue was expressed in HEK-293 cells, most of the enzyme was localized in the cytosol. Its activity was enhanced by Co2+, typical of other known cytosolic alpha-mannosidases so far characterized from animal cells. The down-regulation of Man2C1 activity by a small interfering RNA drastically changed the amount and structure of oligosaccharides accumulating in the cytosol, demonstrating that Man2C1 indeed is involved in free oligosaccharide processing in the cytosol. The oligosaccharide processing in the cytosol by PNGase, endo-beta-N-acetylglucosaminidase and alpha-mannosidase may represent the common 'non-lysosomal' catabolic pathway for N-glycans in animal cells, although the molecular mechanism as well as the functional importance of such processes remains to be determined. Mol Genet Metab. 2006 Sep-Oct. alpha-Mannosidosis is a lysosomal storage disorder caused by deficient activity of lysosomal alpha-mannosidase and is characterised by massive accumulation of mannose-containing oligosaccharides in affected individuals. Patients develop behaviour and learning difficulties, skeletal abnormalities, immune deficiency and hearing impairment. Disease in alpha-mannosidosis guinea-pigs resembles the clinical, histopathological, biochemical and molecular features of the human disease. We have used the guinea-pig model to investigate efficacy of enzyme replacement therapy as a treatment for alpha-mannosidosis. Intravenous recombinant human lysosomal alpha-mannosidase, administered at a dose of 1mg/kg, was cleared from circulation with a half-life of 53 h, with significant enzyme activity (1.4x normal levels) detected in circulation one week post-injection. alpha-Mannosidase administered to alpha-mannosidosis guinea-pigs at 1mg/kg (onset at birth or approximately 30 days) and 10mg/kg (at birth) was distributed widely amongst tissues, including to capillary depleted brain. By monitoring with tandem mass spectrometry, enzyme replacement therapy was found to be effective in reducing stored substrates in peripheral tissues at both dose rates, and in brain by up to 39% at the 10mg/kg dose, compared with untreated alpha-mannosidosis controls. Reductions of up to 60% of urinary mannose containing oligosaccharides were also observed. No histological improvements were seen in the brain at either dose, however marked decreases in lysosomal vacuolation in liver, kidney, spleen and endocrine pancreas, as well as a significant reduction in trigeminal ganglion neurons were observed. Multiple injections of 1mg/kg recombinant enzyme in alpha-mannosidosis guinea-pigs induced a very rapid humoral immune response precluding long-term intravenous treatment. Neurobiol Dis. 2006 Aug. alpha-Mannosidosis is a lysosomal storage disorder caused by lysosomal alpha-mannosidase (LAMAN) deficiency that leads to neurocognitive dysfunctions, psychotic symptoms and emotional changes in human patients. A murine mannosidosis model, LAMAN-deficient mice, was examined on a behavioral task battery that included test for neuromotor, exploratory and neurocognitive (spatial learning and memory) abilities, and multivariate statistical analyses were used to identify behavioral and neurocognitive domains that are most heavily affected by LAMAN deficiency. In addition, we further investigated synaptic plasticity recordings on hippocampal slices that may relate to these behavioral alterations. Correlation analysis revealed significant intra- and intertask correlations and factor analysis that included all 21 behavioral variables identified three main factors (exploration/emotionality, locomotion and learning/memory abilities). Significant correlations were observed between genotype, and factor 1 (exploration/emotionality) and factor 3 (learning/memory abilities). Discriminant function analysis showed that "path length in the open field test" and "time spent in the target quadrant during the water maze probe trial" were the most decisive variables to distinguish between the genotypes. We therefore suggest that these variables would be especially important in forthcoming therapy assessment experiments using this murine mannosidosis model. LAMAN-deficient mice displayed severe changes in synaptic plasticity, which may have contributed to the neurocognitive impairments observed. The present report further shows that targeted deletion of the LAMAN gene in mice mimics many aspects of human alpha-mannosidosis, and these data provide a basis for future therapeutic experiments. J Pediatr Orthop B. 2006 May. Mannosidosis is an extremely rare genetic disease characterized by a deficiency of the lysosomal enzyme, alpha-mannosidase. This enzyme is necessary for cleavage of mannose from many glycoproteins. In the absence of this enzyme, mannose accumulates in cells throughout the body, including the joints and the synovium. This disease causes many skeletal changes including dysostosis multiplex, synovial hypertrophy, and Charcot-type joints. We report the case of a girl, aged 9 years and 6 months, who developed bilateral patellar dislocation and severe synovial hypertrophy secondary to alpha-mannosidase deficiency. Her disease was further complicated by Charcot elbow and bilateral hip and elbow avascular necrosis. Proc Natl Acad Sci U S A. 2006 Mar 7. The conserved oligomeric Golgi (COG) complex is a heterooctameric complex that regulates intraGolgi trafficking and the integrity of the Golgi compartment in eukaryotic cells. Here, we describe a patient with a mild form of congenital disorder of glycosylation type II (CDG-II) that is caused by a deficiency in the Cog1 subunit of the complex. This patient has a defect in both N- and O-glycosylation. Mass spectrometric analysis of the structures of the N-linked glycans released from glycoproteins from the patient's serum revealed a reduction in sialic acid and galactose residues. Peanut agglutinin (PNA) lectin staining revealed a decrease in sialic acids on core 1 mucin type O-glycans, indicating a combined defect in N- and O-glycosylation. Sequence analysis of the COG1 cDNA and gene identified a homozygous insertion of a single nucleotide (2659-2660insC), which is predicted to lead to a premature translation stop and truncation of the C terminus of the Cog1 protein by 80 amino acids. This mutation destabilizes several other COG subunits and alters their subcellular localization and hence the overall integrity of the COG complex. This results in reduced levels and/or altered Golgi localization of alpha-mannosidase II and beta-1,4 galactosyltransferase I, which links it to the glycosylation deficiency. Transfection of primary fibroblasts of this patient with the full length hemagglutinin-tagged Cog1 indeed restored beta-1,4 galactosyltransferase Golgi localization. We propose naming this disorder CDG-II/Cog1, or CDG-II caused by Cog1 deficiency. Graefes Arch Clin Exp Ophthalmol. 2005 Dec. alpha-Mannosidosis is a rare lysosomal storage disease that is caused by an inherited deficiency of the lysosomal alpha-mannosidase. Clinical symptoms include coarse facial features, skeletal involvement (dysostosis multiplex), hearing disabilities, mental retardation and hepatosplenomegaly. Only few cases with ocular symptoms have been reported, mainly with lenticular opacities. We report on two brothers with complex neurological symptoms who presented with late-onset retinal dystrophy and were followed up for 6 years. J Intellect Disabil Res. 2005 Nov. Alpha-mannosidosis is characterized by mild to moderate intellectual disability (ID), moderate to severe neurosensory hearing loss, frequent infections, psychomotor disturbances and skeletal dysmorphism. For the first time, a panel of nine alpha-mannosidosis patients with psychiatric symptoms is presented. The clinical picture has several similarities: a physical or psychological stressor precedes a rapid development of a state of confusion, delusions, hallucinations, anxiety and often depression leading to a severe loss of function. This usually lasts 3-12 weeks, and is followed by a period of somnolence and asthenia. It may be more prevalent in females. In four of the described patients search for organic causes of the syndrome was performed, but revealed only negative findings. Because of the limited number of cases no firm conclusion about the benefit of various psychotropic drugs can be drawn from our observation. Psychiatric symptoms could affect as many as 25% of patients with alpha-mannosidosis. First onset is typically in late puberty to early adolescence. The episodes may be recurrent, and of limited duration although medication may be necessary to alleviate symptoms. Our observations indicate that alpha-mannosidosis is associated with an increased risk of psychiatric symptoms. These should not be dismissed as part of the ID but should give rise to the initiation of adequate diagnostic work-up, treatment and support. J Neurosci. 2005 Jul 13. Mice with alpha-mannosidase gene inactivation provide an experimental model for alpha-mannosidosis, a lysosomal storage disease with severe neuropsychological and psychopathological complications. Neurohistological alterations in these mice were similar to those in patients and included vacuolations and axonal spheroids in the CNS and peripheral nervous system. Vacuolation was most prominent and evenly distributed in neuronal perikarya of the hippocampal CA2 and CA3 regions, whereas CA1 and dentate gyrus were weakly or not affected. Field potential recordings from CA1 region in hippocampal slices showed enhanced theta burst-induced long-term potentiation (LTP) in alpha-mannosidase-deficient mice. Longitudinal assessment in age-matched alpha-mannosidase-deficient and wild-type littermates, using an extended test battery, demonstrated a neurocognitive and psychotiform profile that may relate to the psychopathological alterations in clinical alpha-mannosidosis. Brainstem auditory-evoked potentials and basic neuromotor abilities were not impaired and did not deteriorate with age. Exploratory and conflict tests revealed consistent decreases in exploratory activity and emotional blunting in the knock-out group. alpha-Mannosidosis mice were also impaired in aversively motivated learning and acquisition of signal-shock associations. Acquisition and reversal learning in the water maze task, passive avoidance learning in the step-through procedure, as well as emotional response conditioning in an operant procedure were all impaired. Acquisition or shaping of an appetitive instrumental conditioning task was unchanged. Appetitive odor discrimination learning was only marginally impaired during shaping, whereas both the discrimination and reversal subtasks were normal. We propose that prominent storage and enhanced LTP in hippocampus have contributed to these specific behavioral alterations in alpha-mannosidase-deficient mice. Nervenarzt. 2005 Mar. We report the case of a 27-year-old female with recurrent paranoid-hallucinatory episodes who was initially diagnosed as suffering from schizophrenic psychosis. After 10 years of treatment under this diagnosis, alpha-mannosidosis was identified to be the underlying cause of her psychiatric symptoms. alpha-Mannosidosis is a rare autosomal recessive lysosomal storage disorder associated with decreased activity of the enzyme mannosidase. In the present case, diagnosis was made late in the illness after failure of a response to antipsychotic treatment and with the patient additionally showing progressive cognitive decline. Only after extensive investigation was the diagnosis made by showing decreased alpha-mannosidase enzyme activity in serum and blood leukocytes. This case demonstrates that an unusual clinical course or striking symptom patterns, especially in association with somatic comorbidity, in psychotic patients should lead to diagnostic consideration of inherited metabolic disease. Hum Mutat. 2005 Mar. Mutation analysis performed on six Italian families with alpha-mannosidosis type II allowed the identification of five new mutations in the MAN2B1 gene: c.157G>T, c.562C>T, c.599A>T, c.293dupA, c.2402G>A (p.E53X, p.R188X, p.H200L, p.Y99VfsX61, p.G801D). Protein residues G801 and H200 are conserved among the four mammalian alpha-mannosidases cloned to date: human, cattle, cat and mouse. In vitro expression studies demonstrated that both missense mutations expressed no residual alpha-mannosidase activity indicating that they are disease-causing mutations. Modelling into the three-dimensional structure revealed that the p.H200L could involve the catalytic mechanism, whereas p.G801D would affect the correct folding of the enzyme. Neurology. 2004 Nov 9. Alpha-mannosidosis is an inherited lysosomal storage disease. The authors report three siblings (ages 38 to 47 years) with the rare adult variant. All three had late-onset ataxia and retinal degeneration, adding to hearing loss, cognitive impairment, and dysotosis multiplex. One sibling also had psychosis. MRI revealed cerebellar atrophy and predominantly parieto-occipital white matter changes. MR spectroscopy showed no evidence for demyelination. It appears that the disabling course of adult alpha-mannosidosis is caused by lysosomal accumulation rather than demyelination. Hum Mol Genet. 2004 Sep 15. Alpha-mannosidosis is a lysosomal storage disorder which manifests itself in the excessive storage of mannose-containing oligosaccharides in the lysosomes of multiple peripheral tissues and in the brain. Here we report on the correction of storage in a mouse model of alpha-mannosidosis after intravenous administration of lysosomal acid alpha-mannosidase (LAMAN) from bovine kidney, and human and mouse recombinant LAMAN. The bovine and the human enzyme were barely phosphorylated, whereas the bulk of the mouse LAMAN contained mannose 6-phosphate recognition markers. The clearance decreased from bovine to human to mouse LAMAN with plasma half-times of 4, 8 and 12 min, respectively. The apparent half-life of the internalized enzyme was dependent on the enzyme source as well as tissue type and varied between 3 and 16 h. The corrective effect on the storage of neutral oligosaccharides was time-, tissue- and dose-dependent, and the effects were observed to be transient. After a single dose of LAMAN the maximum corrective effect was observed between 2 and 6 days after injection. In general the corrective effect of the human LAMAN was higher than that of the mouse LAMAN and lowest for the bovine LAMAN. Injection of 250 mU human LAMAN/g body weight followed by a subsequent injection 3.5 days later was sufficient to clear liver, kidney and heart from neutral oligosaccharides. Surprisingly a decrease in mannose containing oligosaccharides was also observed in the brain, with storage levels reported at <30% than that found in controls. These data clearly underline the efficacy of enzyme replacement therapy for the correction of storage in alpha-mannosidosis and suggest that this treatment can substantially decrease storage in the brain. J Pediatr. 2004 May. OBJECTIVES: To study the efficacy of hematopoietic stem cell transplantation (HCT) for ameliorating the clinical manifestations of alpha-mannosidosis. STUDY DESIGN: Four patients with alpha-mannosidosis underwent allogeneic HCT at the University of Minnesota. Diagnosis was established by assay of leukocyte alpha-mannosidase activity level. Physical features, donor engraftment, leukocyte alpha-mannosidase activity, neuropsychologic function, and hearing were monitored before and after transplantation, with follow-up ranging from 1 to 6 years. RESULTS: All 4 patients showed slowing of their neurocognitive development and sensorineural hearing loss before HCT. All patients are alive, with normalization of leukocyte enzyme activity after HCT. Intellectual function has stabilized, with improvement in adaptive skills and verbal memory function in 3 of 4 patients. Hearing has improved to normal or near normal for speech frequencies in 3 patients. No new skeletal abnormalities have developed. CONCLUSIONS: HCT can halt the progressive cognitive loss in patients with alpha-mannosidosis. Early diagnosis and treatment with HCT is critical for optimal results. Cell Mol Life Sci. 2004 May. Misfolded or incompletely assembled multisubunit glycoproteins undergo endoplasmic reticulum-associated degradation (ERAD) regulated in large measure by their N-linked polymannose oligosaccharides. In this quality control system lectin interaction with Glc(3)Man(9)GlcNAc(2) glycans after trimming with endoplasmic reticulum (ER) alpha-glucosidases and alpha-mannosidases sorts out persistently unfolded glycoproteins for N-deglycosylation and proteolytic degradation. Monoglucosylated (Glc(1)Man(9)GlcNAc(2)) glycoproteins take part in the calnexin/calreticulin glucosylation-deglucosylation cycle, while the Man(8)GlcNAc(2) isomer B product of ER mannosidase I interacts with EDEM. Proteasomal degradation requires retrotranslocation into the cytosol through a Sec61 channel and deglycosylation by peptide: N-glycosidase (PNGase); in alternate models both PNGase and proteasomes may be either free in the cytosol or ER membrane-imbedded/attached. Numerous proteins appear to undergo nonproteasomal degradation in which deglycosylation and proteolysis take place in the ER lumen. The released free oligosaccharides (OS) are transported to the cytosol as OS-GlcNAc(2) along with similar components produced by the hydrolytic action of the oligosaccharyltransferase, where they together with OS from the proteasomal pathway are trimmed to Man(5)GlcNAc(1) by the action of cytosolic endo-beta- N-acetylglucosaminidase and alpha-mannosidase before entering the lysosomes. Some misfolded glycoproteins can recycle between the ER, intermediate and Golgi compartments, where they are further processed before ERAD. Moreover, properly folded glycoproteins with mannose-trimmed glycans can be deglucosylated in the Golgi by endomannosidase, thereby releasing calreticulin and permitting formation of complex OS. A number of regulatory controls have been described, including the glucosidase-glucosyltransferase shuttle, which controls the level of Glc(3)Man(9)GlcNAc(2)-P-P-Dol, and the unfolded protein response, which enhances synthesis of components of the quality control system. Eur J Pediatr. 2004 Apr. Alpha-mannosidosis is an autosomal recessive disorder caused by deficiency of lysosomal alpha-mannosidase (LAMAN). Here, we report two sisters with alpha-mannosidosis who developed systemic lupus erythematosus (SLE). The sisters were both homozygous for a one bp deletion within the LAMAN gene resulting in a truncated gene product. The coincidence of alpha-mannosidosis and SLE are discussed with regard to both clinical and molecular findings. CONCLUSION: alpha-mannnosidosis may contribute to the onset of systemic lupus erythematosus in predisposed patients. Clin Rheumatol. 2004 Feb. Storage of oligosaccharides due to a deficiency of alpha-mannosidase can lead to joint destruction in children and young adults. Treating hip destruction with a prosthesis might be successful in some of these patients, although diminished bone quality increases the risk of loosening of the prosthesis. Bone Marrow Transplant. 2003 Aug. Alpha-mannosidosis (alpha-mannosidosis) is a lysosomal storage disease characterized by accumulation of oligosaccharides in various tissues leading to symptoms such as coarse facial features, dysostosis multiplex, hearing disabilities, mental developmental delay and skeletal involvement (dysostosis multiplex). Without treatment, the severe infantile onset form of this autosomal recessive disease leads to progressive neurodegeneration and sometimes to early death. Stem cell transplantation has been shown to be an effective treatment. In the five patients published so far, correction of skeletal abnormalities and improvement of neuropsychological capabilities have been observed. We report the first patient who received a T-cell-depleted peripheral blood stem cell transplantation (PBSCT) for alpha-mannosidosis. The diagnosis of alpha-mannosidosis was made at the age of 14 months. At the age of 24 months, he underwent PBSCT with T-cell depletion by CD34-positive selection from his HLA phenotypically identical mother. Conditioning was carried out with busulfan (20 mg/kg), cyclophosphamide (200 mg/kg), OKT3 and methylprednisolone. The patient is alive and well 27 months after PBSCT and has made significant developmental progress. The pattern of urinary oligosaccharides has returned to almost normal. CD34-positive-selected PBSCT is a feasible option to reduce risk for GVHD for these patients. Turk J Pediatr. 2003 Jan-Mar. We present a case of alpha-mannosidosis with its mutational analysis. She was referred to our hospital with the provisional diagnosis of mucolipidosis. She was the first child of second-degree relative parents. She had a coarse face with flat and wide nasal bridge, hepatosplenomegaly, umbilical hernia, lumbar gibbus, motor and mental retardation and deafness. On peripheral blood smear, lymphocytes revealed vacuoles and neutrophils contained some granules resembling Reilly bodies seen in mucopolysaccharidosis (MPS). Based on these findings, the diagnosis of alpha-mannosidosis was suspected. Her urine oligosaccharide chromatography showed an abnormal pattern with a heavy trisaccharide band. Enzyme studies on white cells confirmed a deficiency of alpha-mannosidase activity, which was 2.6 micromol/g/hr. Her DNA analysis showed a S453Y mutation. Biochim Biophys Acta. 2002 Dec 19. The maturation of N-glycans to complex type structures on cellular and secreted proteins is essential for the roles that these structures play in cell adhesion and recognition events in metazoan organisms. Critical steps in the biosynthetic pathway leading from high mannose to complex structures include the trimming of mannose residues by processing mannosidases in the endoplasmic reticulum (ER) and Golgi complex. These exo-mannosidases comprise two separate families of enzymes that are distinguished by enzymatic characteristics and sequence similarity. Members of the Class 2 mannosidase family (glycosylhydrolase family 38) include enzymes involved in trimming reactions in N-glycan maturation in the Golgi complex (Golgi mannosidase II) as well as catabolic enzymes in lysosomes and cytosol. Studies on the biological roles of complex type N-glycans have employed a variety of strategies including the treatment of cells with glycosidase inhibitors, characterization of human patients with enzymatic defects in processing enzymes, and generation of mouse models for the enzyme deficiency by selective gene disruption approaches. Corresponding studies on Golgi mannosidase II have employed swainsonine, an alkaloid natural plant product that causes "locoism", a phenocopy of the lysosomal storage disease, alpha-mannosidosis, as a result of the additional targeting of the broad-specificity lysosomal mannosidase by this compound. The human deficiency in Golgi mannosidase II is characterized by congenital dyserythropoietic anemia with splenomegaly and various additional abnormalities and complications. Mouse models for Golgi mannosidase II deficiency recapitulate many of the pathological features of the human disease and confirm that the unexpectedly mild effects of the enzyme deficiency result from a tissue-specific and glycoprotein substrate-specific alternate pathway for synthesis of complex N-glycans. In addition, the mutant mice develop symptoms of a systemic autoimmune disorder as a consequence of the altered glycosylation. This review will discuss the biochemical features of Golgi mannosidase II and the consequences of its deficiency in mammalian systems as a model for the effects of alterations in vertebrate N-glycan maturation during development. Mol Genet Metab. 2002 Dec. Beta-mannosidosis is an autosomal recessive lysosomal storage disease resulting from a deficiency of the lysosomal enzyme beta-mannosidase. The clinical manifestations of this disease in reported human cases are very heterogeneous ranging from relatively mild to moderately severe. This is in contrast with the severe prenatal onset seen in ruminant beta-mannosidosis. In humans, mental retardation, hearing loss, frequent infections, and behavioral problems are relatively common. Dysmorphology and skeletal involvement such as those seen in ruminants are unusual. The purpose of this study is to determine the range of clinical expression in human beta-mannosidosis resulting from null mutations. We determined that the beta-mannosidase gene consists of 17 exons. Intron-based PCR primers were designed and used to amplify each of the exons in genomic DNA isolated from patient fibroblasts. We identified two patients with null mutations. Results of the analysis showed that one patient was heterozygous for nonsense mutations G334T (E83X) in exon 2 and C1363T (Q426X) in exon 10, resulting in truncation of the deduced peptide sequence from 879 to 82 and 425 amino acids, respectively. The second patient was homozygous for a deletion mutation in exon 11 (1541delAT). This deletion causes a reading frame shift and 26 out of frame amino acids before a stop codon occurs in exon 12, resulting in truncation of the deduced peptide sequence from 879 to 510 amino acids. Because disease presentation in these patients with null mutations is very variable, ranging from mild to severe, we conclude that beta-mannosidosis in humans may indeed be milder than typical of other lysosomal storage disorders. Proc Natl Acad Sci USA. 2001 Jan 30. Autoimmune diseases are among the most prevalent of afflictions, yet the genetic factors responsible are largely undefined. Protein glycosylation in the Golgi apparatus produces structural variation at the cell surface and contributes to immune self-recognition. Altered protein glycosylation and antibodies that recognize endogenous glycans have been associated with various autoimmune syndromes, with the possibility that such abnormalities may reflect genetic defects in glycan formation. We show that mutation of a single gene, encoding alpha-mannosidase II, which regulates the hybrid to complex branching pattern of extracellular asparagine (N)-linked oligosaccharide chains (N-glycans), results in a systemic autoimmune disease similar to human systemic lupus erythematosus. alpha-Mannosidase II-deficient autoimmune disease is due to an incomplete overlap of two conjoined pathways in complex-type N-glycan production. Lymphocyte development, abundance, and activation parameters are normal; however, serum immunoglobulins are increased and kidney function progressively falters as a disorder consistent with lupus nephritis develops. Autoantibody reactivity and circulating immune complexes are induced, and anti-nuclear antibodies exhibit reactivity toward histone, Sm antigen, and DNA. These findings reveal a genetic cause of autoimmune disease provoked by a defect in the pathway of protein N-glycosylation. From the full text article: Autoimmune diseases afflict an estimated 5% of the human population, yet inherited genetic susceptibilities and causes are for the most part unknown (1, 2). The immune system recognizes glycan-dependent features in self-/non-self-discrimination, and distinct changes in protein glycosylation have been reported in various autoimmune syndromes (3-7). The first autoantibodies to be discovered were the cold agglutinins that bind to glycan chains (termed I/i antigens) and appear to be responsible for approximately 20% of human autoimmune hemolytic anemia cases (3). Elevated levels of autoantibodies to glycolipids are noted in various neurologic disorders, including motor neuron disease (3). Altered glycosylation may also affect immune complex formation. Immunoglobulins with affinity for the Fc region of IgG molecules are found in rheumatoid arthritis, and the severity of the disease is associated with the extent of galactose-deficient N-glycans on Fc (8). Human IgA nephropathy has been associated with altered O-glycosylation of the IgA1 hinge region and Ig deposition in the kidney (9, 10). Another possible role for aberrant glycan production in autoimmune disease includes Tn syndrome, in which reduced transcription of the core 1 O-glycan 1-3 GalT enzyme occurs among hematopoietic compartments. This reduced transcription results in exposure of the Tn antigen on cell surfaces, and some patients suffer hemolytic anemia, thrombopenia, and leukopenia, likely because of the presence of anti-Tn antibodies found in normal serum (11). Glycan structures can clearly participate in pathogenic processes. Yet determining whether glycan recognition and production abnormalities are a cause of autoimmune disease or are secondary events induced by lesions in other metabolic pathways has awaited studies involving in vivo genetic modifications of the glycosylation program itself. Golgi-resident glycosidase and glycosyltransferase enzymes operating in the glycan synthesis pathways are thereby hypothetically promising targets of genetic studies aimed at gaining further insights into the pathogenesis of autoimmune disease. The alpha-mannosidase II enzyme is encoded by a single gene in mammals and resides in the Golgi apparatus, where it trims two mannose residues from hybrid N-linked oligosaccharides. This trimming of the mannose residues allows the subsequent addition of multiple glycan branches by glycosyltransferases, as required for the generation of complex N-glycansthe most prevalent and diverse forms found on mammalian cell surfaces (12-15). Nonerythroid cells from mice lacking a functional alpha-mannosidase II gene were unexpectedly found to compensate for this defect by the activity of another alpha-mannosidase defining an alternative pathway (Fig. 1 and ref. 14). In erythroid cells, glycoproteins were expressed normally at the cell surface, but their portfolio of attached carbohydrate structures was altered with a loss of complex N-glycan branching concurrent with an induction of hybrid N-glycan forms. These animals exhibit a non-life-threatening dyserythropoiesis similar to human congenital dyserythropoietic anemia type II (14). We have since observed an increased morbidity of aged mice lacking alpha-mannosidase II and have therefore attempted to determine whether the loss of alpha-mannosidase II in some tissues is not fully compensated for by the alternative pathway and leads to physiologic defects among nonerythroid cell types. Our findings herein have revealed that alpha-mannosidase II is essential for promoting complex N-glycan branching to varying degrees in different tissues and cell types and on subsets of glycoproteins. The resulting alteration of N-glycan branching provokes a systemic autoimmune disease, indicating that inheritance of an abnormal protein N-glycosylation pathway is an etiologic factor in the pathogenesis of autoimmunity. ... A systemic autoimmune disease was indicated on further immunological analyses of -mannosidase II-deficient mice. At any one time, more than 60% of -mannosidase II-deficient mice with hematuria exhibited anti-nuclear antibody reactivity toward nucleolar as well as nuclear envelope epitopes (Fig. 5A). Antibodies that bound histone, Sm antigen, double-stranded DNA, and single-stranded DNA were also detected (Fig. 5B). In addition, circulating immune complexes were frequently elevated, indicating that some fraction of the immune deposition in the kidney may reflect immune complex trapping. Autoantibodies to autologous protein from the kidney, liver, and lung were also elevated (Fig. 5C). The increased titers of autoantibody reactivity were not significantly affected by the removal of N-glycans from denatured protein with the use of PNGase F (Fig. 5D). Although N-glycan-dependent reactivity to native N-glycosylated glycoprotein conformations cannot be determined, our findings suggest that most autoantibody is produced against a wide range of intracellular and nuclear proteins induced, perhaps by increased phagocytosis and self-antigen presentation that commonly appears in systemic autoimmune disease (2). Taken together with the above spectrum of phenotypic findings, our results reveal a systemic autoimmune disease that is remarkably similar to human systemic lupus erythematosus. ... Discussion Currently identified causes of autoimmune disease encompass modifications of lymphocyte activation or development, chemical or pathogenic exposure, and changes in histocompatibility complex expression (1, 28, 29). We have found that an autosomal recessive genetic defect in the pathway of protein N-glycosylation is also a unique factor capable of inducing systemic autoimmune disease exhibiting symptoms found in human systemic lupus erythematosus, including hematological disorder, immunological disorder (anti-DNA or anti-Sm), renal disorder, and anti-nuclear antibody (30). Examples of single gene lesions that provoke systemic autoimmune disease involve SHP-1, CD22, CTLA-4, IL-2, IL-4, PD-1, transforming growth factor-beta, Fas, Fas ligand, the T cell antigen receptor, and the lyn tyrosine kinase. These defects overtly alter lymphocyte development, abundance, viability, or immune responses (2). The emergence of systemic autoimmune disease can also reflect the involvement of multiple genes. For example, the NZB and NZB/NZW F1 autoimmune mouse models result from defects in multiple genes and exhibit B lymphocyte immune hyperactivity. alpha-Mannosidase II deficiency does not similarly alter lymphoid development, abundance, or proliferation in response to antigen receptor activation and thus is more similar to human systemic autoimmune diseases that also occur without such developmental and immune response abnormalities (2). Although the immune system is obviously the source of increased self-reactivity and thereby involved in the disease process, we have shown that lymphocytes lacking alpha-mannosidase II continue to produce complex N-glycans at the cell surface and at close to normal levels (14). Our findings support the view that the lymphoid population exists without cell-intrinsic defects that easily explain the origin of this systemic autoimmune disease. Additional studies by adoptive transfer, conditional mutagenesis, and transplantation approaches can further address this possibility. Although histocompatibility molecules were expressed normally in mice lacking alpha-mannosidase II, autoimmune disease emergence and severity can be modulated by major histocompatibility haplotypes in some animal models (2). We do not yet know whether MHC haplotype or N-glycosylation plays a role in disease etiology. When N-glycosylation of MHC is completely abrogated by tunicamycin or by mutagenesis of asparagine residues, unglycosylated MHC infrequently reaches the cell surface, being retained in the endoplasmic reticulum; however, those that are found on the cell surface appear to function normally (31). Several hundred Golgi-resident glycosidase and glycosyltransferase enzymes orchestrate the repertoire of cell surface glycan structures. Growth and differentiation signals provided during normal and pathologic metabolism regulate the expression of these enzymes (32). The changing enzyme expression levels in the Golgi of a given cell can alter glycan structures present on the cell surface. Nutritional modifications in humans have also been found to influence the extracellular N-glycan repertoire (33, 34). Interestingly, ingestion of the alpha-mannosidase II inhibitor Swainsonine has been reported to alleviate tumor-induced immune suppression, to increase the propensity for lymphocyte activation, and to inhibit tumor growth and metastasis (35). Whether a clinical regime of alpha-mannosidase II inhibitors can lead to autoimmune disease is not known. Autoimmunity has been divided into systemic and organ-specific types with common mechanistic underpinnings indicated (36). Systemic autoimmunity can lead to organ-specific disease (37), whereas molecular mimicry, histocompatibility haplotypes, and lymphoid involvement may be crucial for the emergence and progression of both disease types. However, antigens that evoke systemic autoimmune disease and factors influencing disease progression are not well understood (2, 24). The previous association of autoimmune syndromes with the induction of anti-carbohydrate antibodies and with carbohydrate structure abnormalities indicated the possibility that glycan recognition or structural alterations might be pathogenic in some circumstances. We can conclude that it is the altered N-glycosylation of one or more glycoproteins that is the cause of systemic autoimmune disease with symptoms of lupus nephritis in the absence of alpha-mannosidase II. It is possible that alterations in N-glycan branching among some glycoproteins and tissues may result in the formation of unusual epitopes that do not fully participate in the immune determination of self. We find that the alternative pathway in complex N-glycan production fails to sufficiently overlap with alpha-mannosidase II function and results in the production of unusual and sometimes unique hybrid glycan N-glycan branches among a subset of glycoproteins and cell types. It is also possible that this abnormal N-glycan expression varies in an age-dependent manner by a developmental change in glycoprotein substrate production and the efficacy of the alternative pathway in complex N-glycan formation. By whatever means, the loss of alpha-mannosidase II alters N-glycan branching and clearly attenuates the immune system's ability to maintain self-tolerance. It is further intriguing to consider whether alpha-mannosidase II inhibition bestows its antitumorigenic effect by modulating the immune-autoimmune threshold. Eur J Pediatr. 2000 Sep. Patients with the autosomal recessive lysosomal storage disease alpha-mannosidosis suffer from recurrent infections. To study the mechanisms of this immunodeficiency, six patients were matched against six healthy controls and their humoral and cellular immunocompetence investigated. No differences in the number of circulating leucocytes including B-cells, levels of immunoglobulin main classes, nor IgG subclasses were observed. However, post-immunisation serum levels of specific antibodies against poliovirus, diphtheria toxin and tetanus toxin were significantly reduced. In patients, the density of the complement-binding receptor CD11b and the Fc-receptor CD16 was significantly enhanced on monocytes and polymorphonuclear neutrophils (PMN) and the number of phagocytosing PMN was significantly increased in the presence of pooled human serum. This was not observed in the presence of autologous serum, indicating altered opsonic properties. Also in normal PMN, phagocytosis was inhibited by a factor in the serum from the patients. Despite maintained oxidative burst, patient PMN demonstrated insufficient intracellular bacterial killing. CONCLUSION: Our data indicate that patients with alpha-mannosidosis have an immunodeficiency at both the humoral and cellular level. Skeletal Radiol. 2000 Jun. We report on a case of a deforming arthropathy in a young man with a lysosomal storage disorder. A 31-year-old man with a known diagnosis of mannosidosis presented with a painful swollen right elbow. Radiographs of his right elbow showed a disorganised joint with multiple fragments resembling the appearances of a neuropathic joint. This case provides further evidence that a deforming arthropathy may occur as part of the spectrum of skeletal abnormalities seen in mannosidosis. Biochim Biophys Acta. 1999 Dec 6. Processing glycosidases play an important role in N-glycan biosynthesis in mammalian cells by trimming Glc(3)Man(9)GlcNAc(2) and thus providing the substrates for the formation of complex and hybrid structures by Golgi glycosyltransferases. Processing glycosidases also play a role in the folding of newly formed glycoproteins and in endoplasmic reticulum quality control. The properties and molecular nature of mammalian processing glycosidases are described in this review. Membrane-bound alpha-glucosidase I and soluble alpha-glucosidase II of the endoplasmic reticulum remove the alpha1,2-glucose and alpha1,3-glucose residues, respectively, beginning immediately following transfer of Glc(3)Man(9)GlcNAc(2) to nascent polypeptides. The alpha-glucosidases participate in glycoprotein folding mediated by calnexin and calreticulin by forming the monoglucosylated high mannose oligosaccharides required for the interaction with the chaperones. In some mammalian cells, Golgi endo alpha-mannosidase provides an alternative pathway for removal of glucose residues. Removal of alpha1,2-linked mannose residues begins in the endoplasmic reticulum where trimming of mannose residues in the endoplasmic reticulum has been implicated in the targeting of malfolded glycoproteins for degradation. Removal of mannose residues continues in the Golgi with the action of alpha1, 2-mannosidases IA and IB that can form Man(5)GlcNAc(2) and of alpha-mannosidase II that removes the alpha1,3- and alpha1,6-linked mannose from GlcNAcMan(5)GlcNAc(2) to form GlcNAcMan(3)GlcNAc(2). These membrane-bound Golgi enzymes have been cloned and shown to have very distinct patterns of tissue-specific expression. There are also broad specificity alpha-mannosidases that can trim Man(4-9)GlcNAc(2) to Man(3)GlcNAc(2), and provide an alternative pathway toward complex oligosaccharide formation. Cloning of the remaining alpha-mannosidases will be required to evaluate their specific functions in glycoprotein maturation. Glycobiology. 1999 Oct. We report the isolation of a novel human cDNA encoding a type II membrane protein of 79.5 kDa with amino acid sequence similarity to Class I alpha 1,2-mannosidases. The catalytic domain of the enzyme was expressed as a secreted protein in Pichia pastoris. The recombinant enzyme removes a single mannose residue from Man9GlcNAc and [1H]-NMR analysis indicates that the only product is Man8GlcNAc isomer B, the form lacking the middle-arm terminal alpha 1,2-mannose. Calcium is required for enzyme activity and both 1-deoxymannojirimycin and kifunensine inhibit the human alpha 1,2-mannosidase. The properties and specificity of this human alpha 1,2-mannosidase are identical to the endoplasmic reticulum alpha 1,2-mannosidase from Saccharomyces cerevisiae and differ from those of previously cloned Golgi alpha 1,2-mannosidases that remove up to four mannose residues from Man9GlcNAc2 during N-glycan maturation. Northern blot analysis showed that all human tissues examined express variable amounts of a 3 kb transcript. This highly specific alpha 1,2-mannosidase is likely to be involved in glycoprotein quality control since there is increasing evidence that trimming of Man9GlcNAc2 to Man8GlcNAc2 isomer B in yeast cells is important to target misfolded glycoproteins for degradation. Childs Nerv Syst. 1999 Aug. Neurological development over a period of 25 years and MRI findings are reported in two members of the same family affected by mannosidosis type II. Progressive axial and appendicular cerebellar syndrome, moderate hearing loss and deterioration of gait were present in both patients. Neuropsychological deficiency was severe, but progression over the years was not observed except in the woman's speech capacity. Neither of the patients showed clinical improvement. A progressive corticosubcortical atrophy stands out in the brain neuroimaging studies, especially at the vermian cerebellar level. The osseous cranial deformities are very characteristic and include brachycephaly, thickening of the calvaria at the expense of the diploe, and poor pneumatization of the sphenoid. Neither of our cases showed an empty sella turcica. Hum Mol Genet. 1999 Aug. Alpha-mannosidosis is a lysosomal storage disease with autosomal recessive inheritance caused by a deficiency of the lysosomal alpha-mannosidase, which is involved in the degradation of asparagine-linked carbohydrate cores of glycoproteins. An alpha-mannosidosis mouse model was generated by targeted disruption of the gene for lysosomal alpha-mannosidase. Homozygous mutant animals exhibit alpha-mannosidase enzyme deficiency and elevated urinary secretion of mannose-containing oligosaccharides. Thin-layer chromatography revealed an accumulation of oligosaccharides in liver, kidney, spleen, testis and brain. The cellular alterations were characterized by multiple membrane-limited cytoplasmic vacuoles as seen for instance in liver, exocrine pancreas, kidney, thyroid gland, smooth muscle cells, osteocytes and in various neurons of the central and peripheral nervous systems. The morphological lesions and their topographical distribution, as well as the biochemical alterations, closely resemble those reported for human alpha-mannosidosis. This mouse model will be a valuable tool for studying the pathogenesis of inherited alpha-mannosidosis and may help to evaluate therapeutic approaches for lysosomal storage diseases. Eur J Cell Biol. 1999 Jul. The Golgi apparatus is enriched in specific enzymes involved in the maturation of carbohydrates of glycoproteins. Among them, alpha-mannosidases IA, IB and II are type II transmembrane Golgi-resident enzymes that remove mannose residues at different stages of N-glycan maturation. alpha-Mannosidases IA and IB trim Man9GlcNAc2 to Man5GlcNAc2, while alpha-mannosidase II acts after GlcNAc transferase I to remove two mannose residues from GlcNAcMan5GlcNAc2 to form GlcNAcMan3GlcNAc2 prior to extension into complex N-glycans by Golgi glycosyltransferases. The objective of this study is to examine the expression as well as the subcellular localization of these Golgi enzymes in the various cells of the male rat reproductive system. Our results show distinct cell-and region-specific expression of the three mannosidases examined. In the testis, only alpha-mannosidase IA and II were detectable in the Golgi apparatus of Sertoli and Leydig cells, and while alpha-mannosidase IB was present in the Golgi apparatus of all germ cells, only the Golgi apparatus of steps 1-7 spermatids was reactive for alpha-mannosidase IA. In the epididymis, principal cells were unreactive for alpha-mannosidase II, but they expressed alpha-mannosidase IB in the initial segment and caput regions, and alpha-mannosidase IA in the corpus and cauda regions. Clear cells expressed alpha-mannosidase II in all epididymal regions, and alpha-mannosidase IB only in the caput and corpus regions. Ultrastructurally, alpha-mannosidase IB was localized mainly over cis saccules, alpha-mannosidase IA was distributed mainly over trans saccules, and alpha-mannosidase II was localized mainly over medial saccules of the Golgi stack. Thus, the cell-specific expression and distinct Golgi subcompartmental localization suggest that these three alpha-mannosidases play different roles during N-glycan maturation. Am J Hum Genet. 1999 Jan. alpha-Mannosidosis is an autosomal recessive disorder caused by deficiency of lysosomal alpha-mannosidase (LAMAN). The resulting intracellular accumulation of mannose-containing oligosaccharides leads to mental retardation, hearing impairment, skeletal changes, and immunodeficiency. Recently, we reported the first alpha-mannosidosis-causing mutation affecting two Palestinian siblings. In the present study 21 novel mutations and four polymorphic amino acid positions were identified by the screening of 43 patients, from 39 families, mainly of European origin. Disease-causing mutations were identified in 72% of the alleles and included eight splicing, six missense, and three nonsense mutations, as well as two small insertions and two small deletions. In addition, Southern blot analysis indicated rearrangements in some alleles. Most mutations were private or occurred in two or three families, except for a missense mutation resulting in an R750W substitution. This mutation was found in 13 patients, from different European countries, and accounted for 21% of the disease alleles. Although there were clinical variations among the patients, no significant LAMAN activity could be detected in any of the fibroblast cultures. In addition, no correlation between the types of mutations and the clinical manifestations was evident. Hum Mol Genet. 1997 May. a-Mannosidosis (MIM 248500) is an autosomal recessive lysosomal storage disorder resulting from deficient activity of lysosomal alpha-mannosidase (LAMAN) (EC 3.2.1.24). The disease is characterized by massive intracellular accumulation of mannose-rich oligosaccharides with resulting mental retardation, hearing loss, immune deficiency and skeletal changes. We report here the purification and characterization of human placenta LAMAN. The enzyme is synthesized as a single-chain precursor which is processed into three glycopeptides of 70, 42 and 15 kDa. The 70 kDa peptide is further partially proteolysed into three more peptides that are joined by disulfide bridges. The laman cDNA sequence was assembled from overlapping fragments obtained by PCR on human fibroblast and human lung cDNA. The deduced amino acid sequence contains a putative signal peptide of 48 amino acids followed by a polypeptide sequence of 962 amino acids. Northern blot analyses revealed a single transcript of approximately 3.5 kb present in all tissues examined but at varying levels. Two affected siblings of Palestinian origin were homozygous for a mutation that causes a His-->Leu replacement at a position which is conserved among class 2 alpha-mannosidases from several species. Pediatr Pol. 1996 Mar. A rare metabolic disease, alpha-mannosidosis, is described in two siblings. Psychomotoric deficiency, deafness, coarse face and radiological changes in the skeletal system indicated an inherited lysosomal storage disease. Eur J Biochem. 1995 Oct 15. Man9-mannosidase, an alpha 1,2-specific exo-enzyme involved in N-linked oligosaccharide processing, has been cloned recently from a human kidney cDNA library [Bause, E., Bieberich, E., Rolfs, A., Volker, C. & Schmidt, B. (1993) Eur. J. Biochem. 217, 533-540]. Transient expression in COS 1 cells of the enzyme resulted in a more than 20-fold increase of a catalytic activity cleaving specifically alpha 1,2-mannosidic linkages in [14C]Man9-GlcNAc2 or [14C]Man5-GlcNAc2. Man9-mannosidase is expressed as a N-glycoprotein with a molecular mass of 73 kDa. Its enzymic activity is metal ion dependent and inhibited strongly by 1-deoxymannojirimycin (50% at 100 microM). Proteolytic studies with the membrane-associated form of Man9-mannosidase support the view that the enzyme is a type II transmembrane protein as predicted from its cDNA sequence. Several lines of evidence suggest that Man9-mannosidase, as expressed, is N-glycosylated at one of three potential Asn-Xaa-Thr/Ser/Cys acceptor sites. Approximately 50% of the N-linked oligosaccharide chains are removed by endoglycosidase H treatment, whereas complete deglycosylation of the enzyme is observed, when transfected cells were cultured in the presence of the Golgi mannosidase II inhibitor swainsonine, indicating that the sugar moiety of Man9-mannosidase is processed partially by Golgi-resident enzymes. This observation is consistent with the results of indirect immunofluorescence studies, pointing to a localization of the Man9-mannosidase predominantly in the juxtanuclear Golgi region. This localization clearly differs from that of pig liver Man9-mannosidase which appears to be located in the endoplasmic reticulum and transient vesicles. Acta Paediatr Jpn. 1995 Apr. We describe a 10 month old boy with alpha-mannosidosis who presented with recurrent bronchopneumonia and diarrhea. Facial coarsening, deafness, hepatosplenomegaly, umbilical hernia, pectus carinatum and widespread Mongolian spots were distinguishing features. He also had mild skeletal deformities grouped together as 'dysostosis multiplex', and vacuolated lymphocytes on peripheral blood smear. These findings coupled with an abnormal urinary oligosaccharide pattern led to the suspicion of a lysosomal storage disease in the patient which proved to be alpha-mannosidosis. An exceptionally low level of alpha-mannosidase activity was subsequently found in serum and cultured skin fibroblasts. The patient's brother, who had died at the age of 10 months, had similar features. To the best of our knowledge, this is the first case reported from Turkey. J Neurosurg. 1995 Apr. The authors present an unusual case in which increased intracranial pressure developed because of multiple-suture craniosynostosis and megaloencephaly in a child with a previously undiagnosed lysosomal storage disease, alpha-D-mannosidase deficiency. This 3-year-old boy presented with a history of frequent naps, headaches, florid papilledema, enlarged head (> 95th percentile), elevated opening pressure by lumbar puncture, a "beaten copper" appearance on skull radiographs, and no hydrocephalus. Multiple synostectomies were performed. Postoperatively, the child's headaches and papilledema resolved and his level of physical activity increased dramatically. The authors discuss the paradoxical presentation of prematurely fused sutures and macrocrania in light of this lysosomal storage disease and its subsequent management. Tidsskr Nor Laegeforen. 1995 Feb 20. Alpha-mannosidosis is a rare autosomal recessively inherited lysosomal storage disorder. We describe three patients with alpha-mannosidosis who were born in Tromso between 1983 and 1987, in order to increase awareness of the disease. It is characterized by a typical facial look, with a prominent forehead, hypertelorism, small nose, flat nasal bridge and hypoplastic teeth. The patients are mentally retarded, often have dysostosis multiplex, recurrent infections and typically severe loss of hearing and delayed speech development. The disease is slowly progressive in the first decade, but shows considerable clinical variability. In most cases, the lymphocytes are vacuolized, but diagnosis depends on measurement of alpha-mannosidase activity in the lymphocytes. Prenatal diagnosis is available, based on chorionic villi sampling in the 9th to 11th week of pregnancy. No causal therapy is known, but establishment of the diagnosis is important to avoid complications, recognize hearing loss and provide speech therapy and special education. The specific diagnosis is critical for genetic counselling and prenatal diagnosis. The authors therefore outline the diagnostic strategy. J Oral Pathol Med. 1995 Feb. Alpha-mannosidosis is a rare storage disease with distinct biochemical, clinical, histological and ultrastructural features. The oro-facial findings in a 26-year-old man are described. Gingival and oral mucosal hyperplasias were studied using histology and transmission electron microscopy (TEM). The TEM findings were comparable to those of other tissues examined in previous reports, consisting of histiocytic cells containing storage vacuoles with fine reticulo-granular material. Acta Cytol. 1994 May-Jun. We report the histopathologic features of the knee bone and synovium and the cytologic features of the synovial fluid from a patient with alpha-mannosidosis. The synovium showed marked papillary hyperplasia with infiltration of foamy histiocytes containing periodic acid-Schiff-positive, diastase-resistant material. Severe degenerative changes were seen in the knee bone. The synovial fluid showed increased numbers of macrophages containing periodic acid-Schiff-positive, diastase-resistant material. The differential diagnostic considerations in the synovial fluid are also discussed. Proc Natl Acad Sci U S A. 1994 Apr 12. Neuronal storage disorders are fatal neurodegenerative diseases of humans and animals that are caused by inherited deficiencies of lysosomal hydrolase activity. Affected individuals often appear normal at birth but eventually develop progressive neurologic symptoms including sensory and motor deficits, mental retardation, and seizures. We have examined efficacy of bone marrow transplantation as a means of enzyme replacement, using cats with the lysosomal storage disease alpha-mannosidosis. Treated animals showed little or no progression of neurologic signs 1-2 years after transplant, whereas untreated cats became severely impaired and reached endstage disease by 6 months of age. Increased lysosomal alpha-mannosidase activity was found in brain tissue of the treated animals, and electron microscopy revealed no evidence of lysosomal storage within most neurons. Histochemical localization of acidic alpha-D-mannoside mannohydrolase (EC 3.2. 1.24), using 5-bromo-4-chloro-3-indolyl alpha-D-mannopyranoside, showed that functional enzyme was present in neurons, glial cells, and cells associated with blood vessels. This study provides direct evidence that bone marrow transplantation as treatment for a neuronal storage disease can lead to significant levels of a missing lysosomal hydrolase within neurons of the central nervous system and to compensation for the genetic metabolic defect. Am J Med Genet. 1993 Jun 1. Human alpha-mannosidosis is a lysosomal storage disorder characterized by mental retardation, dysostosis multiplex, and hepatosplenomegaly. Deficiency of the enzyme leads to accumulation of mannose-rich glycoconjugates in tissues. Zinc sulphate has been shown to stimulate alpha-mannosidase activity in vitro. Oral zinc therapy was attempted on a 4-year-old boy with alpha-mannosidosis for 3 years. After almost 10 years of follow-up on and off zinc therapy, we must conclude that oral zinc does not substantially affect the clinical course of alpha-mannosidosis. S Afr Med J. 1992 Aug. The first known case of alpha-mannosidosis in the RSA is reported. Presentation was classic, viz. delayed speech, kyphoscoliosis and hearing loss at the age of 4 years. Among the generally rare inherited lysosomal storage diseases, alpha-mannosidosis is regarded in Europe and the USA as one of the more common disorders. It is suggested that the apparent underdiagnosis in South Africa may stem from lack of clinical recognition of a condition, which is relatively simple to diagnose biochemically. The clinical and radiological features of the child are described in the hope that clinicians will develop an awareness of the disorder, and include it in the differential diagnosis of deaf children who may also have mild skeletal abnormalities. Antenatal diagnosis of this untreatable condition is possible, so the birth of further affected children in a family could be prevented. Genet Couns. 1992. Two patients, a 13-year-old boy and his 24-year-old sister, were diagnosed as mannosidosis type II cases, on the basis of both presenting extremely reduced plasma and white blood cell acid-alpha-mannosidase are reported. With the exception of mental retardation and neurosensory deafness the two siblings manifested a wide phenotypic variability. The boy had several facial features indicating a lysosomal storage disorder, as well as spondylolisthesis. His sister, apart from heavy eyebrows and lower jaw prognathism appeared normal. Virchows Arch B Cell Pathol Incl Mol Pathol. 1992. The gingival tissues of a male patient suffering from mannosidosis and presenting with gingival overgrowth have been studied. Routine histological assessment highlighted the presence of highly enlarged and vacuolated lymphocytes. The morphology of the connective tissues, fibroblasts and epithelium appeared normal. Immunohistochemical staining of the tissues for chondroitin sulfate proteoglycan demonstrated a normal distribution of this component throughout the connective tissues and intense staining associated with the vacuolated lymphocytes. In vitro studies indicated that fibroblasts isolated from the overgrown tissue did not differ from age and sex matched control fibroblasts with respect to proliferation, protein and proteoglycan synthesis. Taken together, these findings imply that the gingvial overgrowth noted in this patient was not due to a defect in the resident fibroblasts but rather reflected a secondary response to the tissues to impaired host defence mechanisms. HNO. 1990 Mar. The diagnosis of speech and hearing disorders should include lysosomal storage disorders in the differential diagnosis. The diagnostic and therapeutic aspects are described of a child with a deficiency of alpha-D-mannosidase. J Inherit Metab Dis. 1990. Clinical, pathological and biochemical findings in the mannosidoses are described. Family studies showed granulocyte-rich white cell fractions to be the tissue of choice for carrier detection in beta-mannosidosis. Metabolic labelling studies using [3H] mannose demonstrated accumulation of Man beta 1-4GlcNAc in cultured skin fibroblasts from a patient with this condition. Alternative methods of egress from lysosomes were suggested for this compound by its secretion into culture medium and apparent reduction of storage with time in cultures. beta-mannosidase deficient goats are not thought to be a true animal model of the human condition, as although they showed a similar enzyme deficiency, the clinical presentation is much more severe and the major storage material (Man beta 1-4GlcNAc beta 1-4GlcNAc) is different. Arch Neurol. 1989 May. Longitudinal assessments of three brothers with alpha-mannosidosis were performed biochemically by determining levels of leukocyte enzyme activity, and neurodevelopmentally by testing of general intelligence, language, visual spatial skills, and overall adaptive abilities. During the follow-up examination, enzyme activity was assessed in fibroblasts to evaluate the uniformity of biochemical deficits. The biochemical findings demonstrated profound deficits of leukocyte alpha-mannosidase that remained remarkably stable over time and were very similar to levels of the same enzyme activity in fibroblasts. The cognitive findings showed that the patients manifested mild cognitive deficits. Cognitive deficits were generally uniform with no signs of progressive deterioration, except receptive language abilities. Suggestions are made for careful follow-up of auditory abilities in patients with mannosidosis. Arch Dis Child. 1987 Oct. Bone marrow transplantation was performed in a patient with alpha-mannosidosis. To our knowledge this is the first time such treatment has been attempted. The patient died 18 weeks after successful grafting and specimens of tissues were obtained at necropsy. Alpha-mannosidase activity in spleen and liver was just below normal (spleen 102 mumol/g/hour, control 113-330; liver 29 mumol/g/hour, control 30-131). Splenic alpha-mannosidase activity was indistinguishable from the control enzyme with respect to the Michaelis constant, heat stability, and inhibition by cobalt ions, as was 86% of the liver enzyme. In brain tissue alpha-mannosidase activity was 7% of controls, and less than one third had the properties of the normal enzyme. Oligosaccharides were present only in small amounts in liver and spleen, whereas they were greatly increased in brain tissue. Electron microscopic pictures of liver and spleen tissue showed normal morphology, but brain tissue showed definite vacuolation. These findings suggest that transplantation reversed the somatic changes of alpha-mannosidosis but did not affect lysosomal storage within brain tissue. It is concluded that marrow transplantation may not be a suitable treatment for alpha-mannosidosis. Arch Neurol. 1986 Feb. Three brothers with mannosidosis were assessed both biochemically by levels of enzyme activities and developmentally by serial testing of language and cognitive development. The findings indicated that while the leukocyte enzyme activity of alpha-mannosidase was exceptionally low, only mild intellectual deficits were present that did not progress during a two-year follow-up. These results do not substantiate the expected relationship between the severities of enzyme deficiency and developmental delays. Language and cognitive deficits appeared uniform with no areas of strengths or weaknesses. Deficits in development did not progress during a two-year follow-up. Clin Genet. 1984 Mar. Mannose containing oligosaccharides (OS) excreted in the urine of patients with alpha-mannosidosis have been analyzed with high performance liquid chromatography (HPLC). The HPLC method provides a highly sensitive assay for detection of the urinary oligosaccharides and was employed for diagnosis of a fifteen-year-old female with an unusually mild presentation of the disease. Dysostosis multiplex and coarse facies were absent; mental impairment was particularly mild. The elution profile of the urinary OS from this patient and two, more severely affected, patients with mannosidosis were nearly identical, containing nine major OS fractions. The concentrations of the OS were eight fold lower in our patient but, when calculated relative to creatinine, the levels of the urinary OS of all patients were similar. Am J Surg Pathol. 1983 Jul. A 13-year-old female with biochemically proven alpha mannosidase deficiency (mannosidosis) developed a bilateral destructive synovitis of the ankle region, a hitherto unreported complication of this disease. Clinically, it was believed to be a pigmented villonodular synovitis. Histologically, the synovium was thrown into villous folds and was infiltrated with clear histiocytes having rare collections of PAS-positive, diastase-resistant material. Electron microscopy demonstrated numerous membrane bound vacuoles filled with granular, amorphous material. This lesion can be distinguished from pigmented villonodular synovitis by its bilaterally symmetrical distribution, the monomorphic population of cells, and the presence of material having the histochemical and ultrastructural properties of (neutral) oligosaccharides. Clin Genet. 1982 Nov. Two cases of mannosidosis are reported in brothers, one aged 41 years at death, the other aged 40 years and still alive. These patients are the oldest reported in the literature. Prolonged survival has previously been associated with the milder Type II phenotype. In addition to the characteristic clinical and radiological features of mannosidosis, both had severe joint destruction, which may be related to abnormal lysosomal enzymes in cartilage. The activity of acidic alpha-mannosidase was markedly reduced in plasma, leucocytes and fibroblasts, and the altered kinetic and physical properties are described. Ann Clin Res. 1982 Apr. The clinical course of mannosidosis was studied in eight patients. The age at onset of symptoms varied from 6 months to 3 years. The first symptom was usually delayed development of speech or motor or mental functions and was often accompanied by recurrent infections. All the patients were mentally retarded, with slightly coarse facial features, poor ability to speak, sensorineural hearing loss and dysostosis multiplex. Ataxia was seen in all but one case, appearing in childhood at the same time as the hearing loss. Follow-up observations suggested gradual impairment of mental and motor functions and speech with age. Other findings were stunted growth in adults, and vacuolated lymphocytes in the peripheral blood. Clin Genet. 1981 Sep. Two siblings with different degrees of mental retardation, skeletal dysplasia, coarse facies, delayed speech, motor incoordination, recurrent respiratory infections, and immunological abnormalities, were found to have deficient alpha-mannosidase activity. Cultured skin fibroblasts in one sib were markedly deficient in alpha-mannosidase while all other lysosomal enzymes tested were within the normal range. The more severely affected sib came to autopsy and was found to have "washed-out" appearing cortical neurons and marked histiocytosis effacing lymph node architecture and partially replacing the bone marrow. The post-mortem brain and liver samples demonstrated a deficiency in alpha-mannosidase relative to the elevations of other lysosomal enzymes. Although the patterns of abnormalities in the two cases closely match those of descriptions of "type II" and "type I" mannosidosis respectively, the variation should be due to genetic modifiers or environmental effects since the brothers must have shared similar alpha-mannosidase mutations. Immunologic abnormalities present in the more severely affected sib suggest that the differential survival seen in mannosidosis types I and II may be due to differences in their immune systems. Acta Paediatr Scand. 1980 Nov. A 4 1/2-year-old boy with a history of recurring respiratory tract infections and seizures, and evidence of severe retardation of psychomotor development and growth, lacked the coarse facial features, skeletal changes and other clinical stigmata generally associated with mannosidosis, but the total alpha-mannosidase activity in his leukocytes, cultured fibroblasts and liver were no more than 10% of the control mean. Studies of the residual alpha-mannosidase enzyme suggest a specific deficiency of the thermostable isoenzyme with an acidic pH optimum. The alpha-mannosidase in the fibroblasts of our and another (control) patient with mannosidosis had a reduced affinity for the substrate 4-methylumbelliferyl-alpha-D-mannoside. Light microscopy of the liver biopsy showed an increase in connective tissue often distorting the hepatic architecture; numerous tiny vacuoles, small dense and lipid bodies in most hepatocytes, and similar but more extensive changes in sinusoidal cells; and sinusoidal pools of hepatocytic debris. Electron microscopy of hepatocytes revealed vacuoles similar but not identical to those described in reported mannosidosis patients, and in addition several forms of secondary lysosomes; prominent peroxisomes (microbodies); increased numbers of profiles of smooth endoplasmic reticulum; dilated rough endoplasmic reticulum containing traces of fine granulo-fibrillar material; increased numbers of rosettes of alpha particles of glycogen and reduced numbers of mitochondria with alterations in their distribution, size and configuration. It is believed that the usual clinical and hepatic ultrastructural features in our patient reflect another variant of mannosidosis. Birth Defects Orig Artic Ser. 1980. Pediatr Res. 1978 Oct. A partial deficiency of alpha-mannosidase was found in cultured skin fibroblasts, serum, and extracts of leukoytes in two siblings with mild mental retardation, delayed speech, a suggestion of coarse or full facies, and limited mobility of the large joints. All other lysosomal enzymes tested were within the normal range. Their father demonstrated intermediate alpha-mannosidase activity. The addition of 2 mM Zn++ caused a 40% increase of the alpha-mannosidase activity in cell extracts of both patients and control subjects. pH profiles and Cellogel electrophoresis of the patients' cells indicated 20% residual activity of the acidic alpha-mannosidase isoenzyme (pH optimum at 4.0), whereas the activity of the isozyme with pH optimum of 6.0 was normal. Increasing substrate concentration (1-10 mM) demonstrated a 4 to 5-fold increase in the apparent Km of the acidic alpha-mannosidase in the patients' fibroblasts. This residual activity, however, was apparently not sufficient for the normal catabolism of mannose-containing molecules, since electron microscopic examination of the cultured fibroblasts demonstrated numerous lysosomal storage bodies. Medicine (Baltimore). 1977 Jul. Three brothers with mannosidosis were studied, and their clinical and biochemical manifestations are compared with those of 41 cases in the literature. All three boys have psychomotor and growth retardation, characteristic facies, recurrent respiratory infections, sensorineural deafness, craniosynostosis, protuberant abdomens, and thin limbs. Roentgenographic findings of mild dysostosis multiplex, thick calvaria, abnormally contoured vertebrae, coarse trabeculi and thin cortices are consistent with those of reported cases. The lymphocytes of peripheral blood and bone marrow are vacuolated. Alpha-mannosidase deficiency in leukocytes and cultured skin fibroblasts and glycoproteinuria have been documented. The biochemistry of this glycoproteinosis and the pitfalls in diagnosis, such as improper assay conditions of pH and substrate concentration, are discussed. Extrapolation of in vitro and animal model studies suggest that trace metal therapy may be more effective than attempts at enzyme replacement to treat this hereditary storage disease. Arch Neurol. 1977 Jan. Mannosidosis is a rare inborn error of metabolism characterized by deficiency of the lysosomal enzyme alpha-mannosidase and widespread storage of complex carbohydrate, which is enriched in mannose. Two affected unrelated males, aged 6 and 26 years, are reported. Both had a nonprogressive encephalopathy with moderately severe mental retardation. The older patient showed several unique features, including massive gingival hyperplasia associated with histiocytes containing large amounts of a material with the staining characteristics of glycoprotein. The best determinant of mannose storage proved to be the ratio of mannose to other carbohydrates in urinary polysaccharides. The enzyme deficiency in this disease is most convincingly demonstrated at pH values below 4.0. The ability of zinc to activate the mutant enzyme in vitro offers a possible mode of therapy for this disease. Retarded individuals with a Hurler-like appearance and gum hyperplasia of unknown cause should be screened for alpha-mannosidase deficiency. Am J Med. 1976 Dec. Mannosidosis is a partially defined disorder of glycoprotein metabolism; less than 20 cases have been reported in the literature. In this work, a longitudinal study of five new patients is presented in an attempt to delineate the phenotype and clinical course of this unusual storage disease. The data on our patients and those in the literature indicate that people with mannosidosis appear normal at birth and that their typical phenotype develops by two years of age. This is characterized by a distinctive coarse facies and dysostosis multiplex. Although recurrent infections, hearing loss and mental retardation occur, the course in this storage disorder generally is stable and is compatible with adult life. The diagnosis is confirmed by the presence of a deficiency in alpha-D-mannosidase activity in leukocytes or fibroblasts, by the presence of vacuolated lymphocytes in peripheral blood and foam cells in bone marrow, and an increased excretion of mannose-rich oligosaccharides in urine. Pediatr Res. 1976 Dec. The primary metabolic defect in mannosidosis is the deficiency of the acidic alpha-mannosidase A and B activites which results in the lysosomal accumulation of mannose-rich substrates. Out studies demonstrate that the enzymatic diagnosis of suspect homozygotes can be made reliably using plasma, isolated leukocytes, or cultured skin fibroblasts assayed carefully at the appropriate acidic pH. Immunologic studies of a mannosidosis homozygote revealed significant abnormalities of neutrophil function; these included a depressed chemotactic responsiveness and impaired phagocytosis of bacteria. Lymphocyte transformation studies showed a 20% of normal response to purified phytohemagglutinin and a 25% of normal response to concanavalin A. Three major components of alpha-mannosidase activity in normal human liver were resolved by ion exchange chromatography on DEAE-cellulose and electrophoresis on cellulose acetate gels. Electrophoresis of the liver extract from homozygote I with mannosidosis revealed only one band of activity which coelectrophoresed with the alpha-mannosidase C isozyme partially purified from normal liver. However, ion exchange chromatography revealed the presence of residual hepatic acidic activities; the residual A isozyme was eluted in a position corresponding to that of normal alpha-mannosidase A whereas the residual B activity was eluted at a slightly more electronegative position than that of normal B isozyme. The apparent Km values for alpha-mannosidase activity as determined from Linweaver-burk plots were 1.1 mM for normal liver and 0.9 mM for normal leukocytes. In contrast, the residual activity in these sources from homozygote 1 could not be saturated within the solubility range of the substrate; the apparent Km value was estimated at 15.4 mM in liver extracts. Zinc significantly lowered the apparent Km value of the acidic activity in normal liver (from 1.2 to 0.24 mM), whereas this metallic ion had little effect on the values for mannosidosis hepatic activity (from 15.4 to 12.3 mM). Unlike zinc, cobalt had its major effect on the acidic activity in the mannosidosis liver extract, lowering the apparent Km from 15.4 to 3.9 mM, whereas the apparent Km for the normal activity was increased from 1.2 to 1.9 mM. The residual acidic activities were markedly stimulated by zinc in both leukocytes (approximately 300%) and plasma ( approximately 400%) from the homozygotes and to a lesser extent in those sources from normal individuals. In contrast, cobalt enhanced the residual acidic activities in leukocytes (approximately 500%) and plasma (approximately 200%) from the homozygotes while inhibiting these acidic activities (78.9% and 47.7%, respectively) in normal individuals. J Pediatr. 1976 May. A three-year-old boy has coarse facial features, upper respiratory congestion, profound mental retardation, hepatosplenomegaly, increased height and head circumference, cataracts, a gibbus deformity, radiographic changes of dysostosis multiplex, and vacuolized peripheral lymphocytes. These findings are the most commonly reported clinical features in the previously described patients with mannosidosis. Our patient has a severe deficiency, and his parents have intermediate levels, of the acidic component of alpha-mannosidase in their cultured fibroblasts. Radiology. 1976 May. Skeletal changes seen in 12 patients with mannosidosis included thickened calvaria, ovoid configuration, flattening and hook-shaped deformity of the vertebral bodies, hypoplasia of the inferior portions of the ilia, and mild expansion of the short tubular bones of the hands. The pattern of skeletal changes is that of mild to moderate dysostosis multiplex with considerable intrafamilial variation. The skeletal abnormalities may decrease with age. Correlation of the skeletal abnormalities with clinical and biochemical findings is necessary for a specific diagnosis. Arch Fr Pediatr. 1976 Jan. Mannosidosis is a new and rare disorder. The following clinical symptoms should evolve its diagnosis: facial dysmorphy with slight mental retardation; bone deformities with abnormal L2 vertebra and craniosynostosis; biological abnormalities with vacuolized lymphocytes and absence of urinary mucopolysaccharides. Definite diagnosis relies upon detection of mannose oligosaccharides in the urine and serum deficiency of alpha-D-mannosidase. |