I-cell Disease Research Articles

Profiling oligosaccharidurias by electrospray tandem mass spectrometry: Quantifying reducing oligosaccharides

A method to semiquantify urinary oligosaccharides from patients suffering from oligosaccharidurias is presented. 1-Phenyl-3-methyl-5-pyrazolone has been used to derivatize urinary oligosaccharides prior to analysis by electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Disease-specific oligosaccharides were identified for several oligosaccharidurias, including G M1 gangliosidosis, G M2 gangliosidosis, sialic acid storage disease, sialidase/neuraminidase deficiency, galactosialidosis, I-cell disease, fucosidosis, Pompe and Gaucher diseases, and α-mannosidosis. The oligosaccharides were referenced against the internal standard, methyl lactose, to produce ratios for comparison with control samples. Elevations in specific urinary oligosaccharides were indicative of lysosomal disease and the defective catabolic enzyme. This method has been adapted to enable assay of large sample numbers and could readily be extended to other oligosaccharidurias and to monitor oligosaccharide levels in patients receiving treatment. It also has immediate potential for incorporation into a newborn screening program.

Prenatal mucolipidosis type II (I‐cell disease) can present as Pacman dysplasia

Pacman dysplasia has been previously reported to be a lethal skeletal dysplasia with epiphyseal stippling and osteoclastic overactivity. We report on a sibling of a fetus previously reported as Pacman dysplasia. This infant has a clinical course consistent with mucolipidosis type II (I-cell disease) along with confirmatory biochemical, cytologic, and radiographic evidence. This case expands the phenotypic spectrum of mucolipidosis type II. Having redefined the diagnosis in one of the original cases of Pacman dysplasia, we suggest that what is called Pacman dysplasia could very well be Mucolipidosis type II (ML-II) in other published reports.

Gingivectomy for gingival enlargement in a child with I-cell disease: a report of case

I-cell disease is a rare autorecessive metabolic disorder that is classified as one of the lysosomal storage diseases. Gingival enlargement is a representative oral manifestation of patients with I-cell disease. This report describes a case with a satisfactory prognosis after gingivectomy for gingival enlargement accompanying I-cell disease in a 2-year-old boy. The chief complaints were both eating disorders and night terrors accompanied by gingival enlargement of both the maxillary and mandibular alveolar gingivae, especially in the region of the first deciduous molars. Although it was supposed that there were various hazards associated with gingivectomy caused by aortic incompetence, sigmoidal spinal curvature and hypertrophy of the laryngopharynx, gingivectomy with an internal bevel incision was performed under general anesthesia to improve the chief complaints. A piece of the enlarged gingivae dissected during the operation was examined histopathologically, and the histopathological diagnosis was gingival hyperplasia. The patient's signs and symptoms of the eating disorders and night terrors have improved since the gingivectomy operation. Recurrence of the gingival enlargement has not been identified up to 18 months after the surgery. It is therefore concluded that gingivectomy for gingival enlargement accompanying I-cell disease was effective for this 2-year-old boy.

Gingivectomy for gingival enlargement in a child with I-cell disease: a report of case

Gingivectomy for gingival enlargement in a child with I-cell disease: a report of case

Acid Sphingomyelinase: Relation of 93Lysine Residue on the Ratio of Intracellular to Secreted Enzyme Activity

Acid sphingomyelinase (ASM) is the lysosomal enzyme responsible for the hydrolysis of sphingomyelin to ceramide and phosphocholine. An inherited deficiency of this enzymatic activity results in the Type A and B forms of Niemann-Pick disease (NPD). ASM is also readily secreted from cultured cells and can rapidly move from lysosomes to the cell surface upon stimulation by cytokines and other factors. Recent interest has focused on the role of this secreted/cell surface enzyme in ceramide-mediated signal transduction. We therefore sought to understand the mechanism(s) that might regulate intracellular targeting and secretion of this important hydrolase. Most lysosomal proteins are targeted to lysosomes in mammalian cells via the mannose 6-phosphate recognition system. Using cultured skin fibroblasts from I-cell disease patients, in which one of the enzymes responsible for mannose phosphorylation, GlcNAc-phosphotransferase, is deficient, we determined ASM activities in cell homogenates and media. The ratio of secreted to intracellular activity was approximately 8-fold greater in I-cell than in normal cells, indicating that mannose phosphorylation is important in the trafficking of this hydrolase. Most of the secreted activity required Zn+2 for full activity, supporting the concept that intracellular exposure of ASM to zinc within lysosomes is required for enzymatic activation. The recognition of lysosomal proteins by GlcNAc-phosphotransferase is mediated by protein structure, and a specific three-dimensional arrangement of lysine residues exposed on the surface of several enzymes has been shown to be critical for mannose phosphorylation. Alanine scanning mutagenesis of thirteen lysine residues in ASM demonstrated that 93lysine residue plays a critical role in ASM targeting since the K93A mutant had reduced intracellular activity, but enhanced secreted activity that was zinc responsive.

Mucolipidosis II presenting as severe neonatal hyperparathyroidism

Mucolipidosis II (ML II or I-cell disease ) (OMIM 252500) is an autosomal recessive lysosomal enzyme targeting disorder that usually presents between 6 and 12 months of age with a clinical phenotype resembling Hurler syndrome and a radiological picture of dysostosis multiplex. When ML II is severe enough to be detected in the newborn period, the radiological changes have been described as similar to hyperparathyroidism or rickets. The biological basis of these findings has not been explored and few biochemical measurements have been recorded. We describe three unrelated infants with ML II who had radiological features of intrauterine hyperparathyroidism and biochemical findings consistent with severe secondary neonatal hyperparathyroidism (marked elevation of serum parathyroid hormone and alkaline phosphatase levels). The vitamin D metabolites were not substantially different from normal and repeatedly normal calcium concentrations excluded vitamin D deficiency rickets and neonatal severe hyperparathyroidism secondary to calcium-sensing receptor gene mutations (OMIM 239200). The pathogenesis of severe hyperparathyroidism in the fetus and newborn with ML II is unexplained. We hypothesize that the enzyme targeting defect of ML II interferes with transplacental calcium transport leading to a calcium starved fetus and activation of the parathyroid response to maintain extracellular calcium concentrations within the normal range. Newborns with mucolipidosis II can present with radiological and biochemical signs of hyperparathyroidism. Awareness of this phenomenon may help in avoiding diagnostic pitfalls and establishing a proper diagnosis and therapy.

Mannose 6-Phosphorylated Proteins Are Required for Tumor Necrosis Factor-induced Apoptosis: DEFECTIVE RESPONSE IN I-CELL DISEASE FIBROBLASTS

Whereas caspases are essential components in apoptosis, other proteases seem to be involved in programmed cell death. This study investigated the role of lysosomal mannose 6-phosphorylated proteins in tumor necrosis factor (TNF)-induced apoptosis. We report that fibroblasts isolated from patients affected with inclusion-cell disease (ICD), having a deficient activity of almost all lysosomal hydrolases, are resistant to the toxic effect of TNF. These mutant cells exhibited a defect in TNF-induced caspase activation, Bid cleavage, and release of cytochrome c. In contrast, TNF-induced p42/p44 MAPK activation and CD54 expression remained unaltered. Human ICD lymphoblasts and fibroblasts derived from mice nullizygous for Igf2 and the two mannose 6-phosphate (M6P) receptors, Mpr300 and Mpr46, which develop an ICD-like phenotype, were also resistant to CD95 ligand and TNF, respectively. Moreover, correction of the lysosomal enzyme defect of ICD fibroblasts, using a medium enriched in M6P-containing proteins, enabled restoration of sensitivity to TNF. This effect was blocked by exogenous M6P but not by cathepsin B or L inhibitors. Altogether, these findings suggest that some M6P-bearing glycoproteins modulate the susceptibility to TNF-induced apoptosis. As a matter of fact, exogenous tripeptidyl peptidase 1, a lysosomal carboxypeptidase, could sensitize ICD fibroblasts to TNF. These observations highlight the hitherto unrecognized role of some mannose 6-phosphorylated proteins such as tripeptidyl peptidase 1 in the apoptotic cascade triggered by TNF.

Allogeneic stem cell transplantation for the treatment of lysosomal and peroxisomal metabolic diseases.

This is a review of the clinical responses and prospectus of new therapies following use of allogeneic hematopoietic stem cell transplantation for the treatment of the following disorders: Hurlers syndrome (MPS 1-H), globoid cell leukodystrophy (GLD; Krabbes disease), adrenoleukodystrophy, metachromatic leukodystrophy, Wolmans disease, I-cell disease (mucolipidosis II; MLS-II), alpha-mannosidosis, fucosidosis, Niemann-Pick B/A disease, Slys disease (MPS VII), Gauchers disease (Gaucher-II-III), Battens disease, Farbers disease, Sanfilippo syndrome (MPS-III), Hunters disease (MPS-II), Maroteaux-Lamy syndrome (MPS-VI), and aspartylglucosaminuria (AGU). Over 500 patients with lysosomal and peroxisomal metabolic storage diseases due to deficiency of primary enzymes have been treated with hematopoietic stem cell transplantation since the initial patient was treated a quarter of century ago. Normal enzymatic activity has been robust and continuous over these years without the need for any medication. Proof of principle has been reported for multiple positive effects including that of the reconstruction of the central nervous system. Furthermore, the excellent engraftment rate along with significantly diminished graft-vs-host-disease needs to be emphasized. The genetic diseases enumerated above have remarkable differences from those discussed elsewhere in this issue of Seminars in Immunopathology. Each has a greater genetic heterogeneity. Misdiagnosis resulting in delay of treatment and further decline of function and ultimate quality of life occurs almost all the time. Neonatal screening of these diseases will be mandatory to vastly improve outcomes. Plans are being implemented to use dried blood spots on filter paper, as is commonly done for many other genetic diseases. Many new therapies are being adopted which should enhance positivity and acceptance of treatment by hematopoietic stem cell transplantation.

The trafficking of prosaposin (SGP-1) and GM2AP to the lysosomes of TM4 Sertoli cells is mediated by sortilin and monomeric adaptor proteins.

Prosaposin (SGP-1) and GM2 activator protein (GM2AP) are soluble sphingolipid activator proteins (SAPs) that are targeted to the lysosomal compartment of Sertoli cells to aid hydrolases in the breakdown of glycosphingolipids. To reach the lysosome, most soluble proteins must interact with the mannose 6-phosphate receptor (MPR). To be sorted from the Golgi, the MPR must bind to the Golgi associated, gamma-adaptin homologous, ARF binding proteins (GGAs), a group of monomeric adaptor proteins responsible for the recruitment of clathrin. It is well established, however, that the lysosomes of I-cell disease (ICD) patients have near normal levels of several lysosomal proteins, including prosaposin and GM2AP. ICD results from a mutation in the phosphotransferase that adds mannose 6-phosphate to hydrolases. Thus, prosaposin and GM2AP can traffic to lysosomes in a MPR independent manner. Previous work has demonstrated that an interaction with sphingomyelin in the Golgi membrane is necessary for the targeting of prosaposin by an unknown receptor. Using a TM4 Sertoli cell line, we tested the hypothesis that prosaposin and GM2AP are targeted to the lysosomal compartment via the sortilin receptor, which has been recently shown to have a GGA binding motif. Interestingly, dominant-negative GGAs, unable to bind clathrin to shuttle from the Golgi, prevented the trafficking of prosaposin and GM2AP to lysosomes. A dominant negative construct of sortilin lacking the GGA binding domain retained prosaposin and GM2AP in the Golgi. In conclusion, our results showed that the trafficking of prosaposin and GM2AP to the lysosome is dependent on sortilin.

The lysosomal trafficking of sphingolipid activator proteins (SAPs) is mediated by sortilin

Most soluble lysosomal proteins bind the mannose 6-phosphate receptor (M6P-R) to be sorted to the lysosomes. However, the lysosomes of I-cell disease (ICD) patients, a condition resulting from a mutation in the phosphotransferase that adds mannose 6-phosphate to hydrolases, have near normal levels of several lysosomal proteins, including the sphingolipid activator proteins (SAPs), GM2AP and prosaposin. We tested the hypothesis that SAPs are targeted to the lysosomal compartment via the sortilin receptor. To test this hypothesis, a dominant-negative construct of sortilin and a sortilin small interfering RNA (siRNA) were introduced into COS-7 cells. Our results showed that both the truncated sortilin and the sortilin siRNA block the traffic of GM2AP and prosaposin to the lysosomal compartment. This observation was confirmed by a co-immunoprecipitation, which demonstrated that GM2AP and prosaposin are interactive partners of sortilin. Furthermore, a dominant-negative mutant GGA prevented the trafficking of prosaposin and GM2AP to lysosomes. In conclusion, our results show that the trafficking of SAPs is dependent on sortilin, demonstrating a novel lysosomal trafficking.

Inheritance, biochemical abnormalities, and clinical features of feline mucolipidosis II: the first animal model of human I-cell disease.

Mucolipidosis II (ML II), also called I-cell disease, is a unique lysosomal storage disease caused by deficient activity of the enzyme N-acetylglucosamine-1-phosphotransferase, which leads to a failure to internalize enzymes into lysosomes. We report on a colony of domestic shorthair cats with ML II that was established from a half-sibling male of an affected cat. Ten male and 9 female kittens out of 89 kittens in 26 litters born to clinically normal parents were affected; this is consistent with an autosomal recessive mode of inheritance. The activities of three lysosomal enzymes from affected kittens, compared to normal adult control cats, were high in serum (11-73 times normal) but low in cultured fibroblasts (9-56% of normal range) that contained inclusion bodies (I-cells), reflecting the unique enzyme defect in ML II. Serum lysosomal enzyme activities of adult obligate carriers were intermediate between normal and affected values. Clinical features in affected kittens were observed from birth and included failure to thrive, behavioral dullness, facial dysmorphia, and ataxia. Radiographic lesions included metaphyseal flaring, radial bowing, joint laxity, and vertebral fusion. In contrast to human ML II, diffuse retinal degeneration leading to blindness by 4 months of age was seen in affected kittens. All clinical signs were progressive and euthanasia or death invariably occurred within the first few days to 7 months of life, often due to upper respiratory disease or cardiac failure. The clinical and radiographic features, lysosomal enzyme activities, and mode of inheritance are homologous with ML II in humans. Feline ML II is currently the only animal model in which to study the pathogenesis of and therapeutic interventions for this unique storage disease.

Abnormal fetal head shape: diagnosis and management

An abnormal head shape is an uncommon finding on prenatal ultrasound, associated most commonly with spina bifida, aneuploidy or oligohydramnios. In other cases diagnosis can be difficult. The objective of this study was to define management pathways for the investigation of fetuses with an abnormal head shape. Fetuses with an abnormal skull shape seen over a 10-year period in our unit were identified by searching the computerised database. Sonographic findings, diagnosis and outcome were reviewed. Three hundred and thirty-one cases were identified, the majority being associated with spina bifida (30%, lemon-shaped), aneuploidy (12%, strawberry-shaped) or dolicocephaly (18%) secondary to fetal position or oligohydramnios. Of the remainder, eight had craniosynostosis, three of which had a skeletal dysplasia. There was also one fetus each with Aperts syndrome, Saethre Chotzen syndrome and I-cell disease and two with an as yet undefined craniosynostosis sydrome.

Cathepsin-L, a Key Molecule in the Pathogenesis of Drug-Induced and I-Cell Disease-Mediated Gingival Overgrowth: A Study with Cathepsin-L-Deficient Mice

Drug-induced gingival overgrowth, the chronic side effect of calcium antagonists, is frequently seen due to the increase in patients with hypertension, although the etiology of the disease is largely unknown. I-cell disease, which accompanies gingival overgrowth, is characterized by a deficiency in UDP-N-acetyl-glucosamine and is classified as one of the lysosomal storage diseases. Here, we hypothesized that a common mechanism may underlie the etiology of gingival overgrowth seen in patients treated with calcium antagonist and in patients with I-cell disease. A calcium antagonist, nifedipine, specifically suppressed cathepsin-L activity and mRNA expression, but not that of cathepsin-B in cultured gingival fibroblasts. The activity of cathepsin-L was suppressed up to 50% at 24 hours after treatment of the cells with the reagent. The selective suppression of cathepsin-L activity appeared not to be dependent on Ca(2+), since treatment of the cells with thapsigargin suppressed both cathepsin-B and -L activity. Mice deficient in the cathepsin-L gene manifested enlarged gingivae. Histological observation of the gingivae demonstrated typical features of acanthosis, a phenotype very similar to that of experimentally induced gingival overgrowth. Since cathepsin-L deficiency was reported to be associated with thickening of the skin, impaired cathepsin-L activity may play a key role in the establishment of skin and gingival abnormalities seen in I-cell disease. In addition, reduced cathepsin-L activity may play an important role in inducing drug-induced gingival overgrowth.

Clinical and genetic aspects of trigonocephaly: A study of 25 cases

We reviewed 25 patients ascertained through the finding of trigonocephaly/metopic synostosis as a prominent manifestation. In 16 patients, trigonocephaly/metopic synostosis was the only significant finding (64%); 2 patients had metopic/sagittal synostosis (8%) and in 7 patients the trigonocephaly was part of a syndrome (28%). Among the nonsyndromic cases, 12 were males and 6 were females and the sex ratio was 2 M:1 F. Only one patient with isolated trigonocephaly had an affected parent (5.6%). All nonsyndromic patients had normal psychomotor development. In 2 patients with isolated metopic/sagittal synostosis, FGFR2 and FGFR3 mutations were studied and none were detected. Among the syndromic cases, two had Jacobsen syndrome associated with deletion of chromosome 11q 23 (28.5%). Of the remaining five syndromic cases, different conditions were found including Say-Meyer syndrome, multiple congenital anomalies and bilateral retinoblastoma with no detectable deletion in chromosome 13q14.2 by G-banding chromosomal analysis and FISH, I-cell disease, a new acrocraniofacial dysostosis syndrome, and Opitz C trigonocephaly syndrome. The last two patients were studied for cryptic chromosomal rearrangements, with SKY and subtelomeric FISH probes. Also FGFR2 and FGFR3 mutations were studied in two syndromic cases, but none were found. This study demonstrates that the majority of cases with nonsyndromic trigonocephaly are sporadic and benign, apart from the associated cosmetic implications. Syndromic trigonocephaly cases are causally heterogeneous and associated with chromosomal as well as single gene disorders. An investigation to delineate the underlying cause of trigonocephaly is indicated because of its important implications on medical management for the patient and the reproductive plans for the family.

Mucolipidoses II (I‐cell disease): case report

Mucolipidoses II (I‐cell disease): case report

Biosynthesis of lysosomal proteinases in health and disease.

Proteolytic maturation of lysosomal proteinases is initiated after receptor-mediated targeting to prelysosomal compartments, while terminal processing occurs upon delivery to lysosomes. These late processing events are impaired in patients suffering from inherited lysosomal disorders, such as sialic acid storage disease and mucolipidosis II (I-cell disease). Lysosomes in the affected cells display marked changes in their physiological and morphological properties, with features reminiscent of prelysosomal compartments. This indicates that the absence of mature lysosomes interferes with the final processing steps during the biosynthesis of lysosomal proteinases. Thus, impaired proteinase maturation reflects an incompetent lysosomal apparatus and as such can be seen as a hallmark of lysosomal storage diseases.

Human Acid Ceramidase: PROCESSING, GLYCOSYLATION, AND LYSOSOMAL TARGETING

The biosynthesis of human acid ceramidase (hAC) starts with the expression of a single precursor polypeptide of approximately 53-55 kDa, which is subsequently processed to the mature, heterodimeric enzyme (40 + 13 kDa) in the endosomes/lysosomes. Secretion of hAC by either fibroblasts or acid ceramidase cDNA-transfected COS cells is extraordinarily low. Both lysosomal targeting and endocytosis critically depend on a functional mannose 6-phosphate receptor as judged by the following criteria: (i) hAC-precursor secretion by NH(4)Cl-treated fibroblasts and I-cell disease fibroblasts, (ii) inhibition of the formation of mature heterodimeric hAC in NH(4)Cl-treated fibroblasts or in I-cell disease fibroblasts, and (iii) blocked endocytosis of hAC precursor by mannose 6-phosphate receptor-deficient fibroblasts or the addition of mannose 6-phosphate. The influence of the six individual potential N-glycosylation sites of human acid ceramidase on targeting, processing, and catalytic activity was determined by site-directed mutagenesis. Five glycosylation sites (sites 1-5 from the N terminus) are used. The elimination of sites 2, 4, and 6 has no influence on lysosomal processing or enzymatic activity of recombinant ceramidase. The removal of sites 1, 3, and 5 inhibits the formation of the heterodimeric enzyme form. None of the mutant ceramidases gave rise to an increased rate of secretion, suggesting that lysosomal targeting does not depend on one single carbohydrate chain.

The cation-dependent mannose 6-phosphate receptor.

The 46kDa cation-dependent mannose 6-phosphate receptor (CD-MPR) and the 300kDa cation-independent mannose 6-phosphate receptor (CI-MPR) are the sole members of the P-type family of lectins, which derive their name from their ability to bind phosphorylated mannose residues. The MPRs are found ubiquitously in higher eukaryotes, and most cell types express both receptors. A key function mediated by the MPRs is the targeting of newly synthesized soluble acid hydrolases bearing mannose 6-phosphate (Man-6-P) residues to the lysosome, an acidified organelle that is responsible for the degradation of both internalized and endogenous macromolecules (de Duve 1963). The generation of functional lysosomes is essential for the survival of the organism as evidenced by the autosomal recessive human lysosomal storage disorder, mucolipidosis II (I-cell disease; Neufeld 1991), a disease characterized by severe psychomotor retardation, hepatomegaly, and cardiomegaly that results in death within the first decade of life (Kornfeld and Sly 1995). I-cell disease is caused by the absence of the enzyme (i.e., phosphotransferase) which generates the Man-6-P recognition marker on lysosomal enzymes, resulting in the mistargeting of these enzymes into the secretory pathway. As expected, patients affected with this disease exhibit elevated levels of lysosomal enzymes in their serum and extracellular fluids and their cells contain numerous dense vacuoles filled with storage material.KeywordsLysosomal EnzymeAcid Hydro LasesEndoplasmic ReticPhosphate OxygenBovine TestisThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Metabolic cardiomyopathies.

The energy needed by cardiac muscle to maintain proper function is supplied by adenosine Ariphosphate primarily (ATP) production through breakdown of fatty acids. Metabolic cardiomyopathies can be caused by disturbances in metabolism, for example diabetes mellitus, hypertrophy and heart failure or alcoholic cardiomyopathy. Deficiency in enzymes of the mitochondrial beta-oxidation show a varying degree of cardiac manifestation. Aberrations of mitochondrial DNA lead to a wide variety of cardiac disorders, without any obvious correlation between genotype and phenotype. A completely different pathogenetic model comprises cardiac manifestation of systemic metabolic diseases caused by deficiencies of various enzymes in a variety of metabolic pathways. Examples of these disorders are glycogen storage diseases (e.g. glycogenosis type II and III), lysosomal storage diseases (e.g. Niemann-Pick disease, Gaucher disease, I-cell disease, various types of mucopolysaccharidoses, GM1 gangliosidosis, galactosialidosis, carbohydrate-deficient glycoprotein syndromes and Sandhoff's disease). There are some systemic diseases which can also affect the heart, for example triosephosphate isomerase deficiency, hereditary haemochromatosis, CD 36 defect or propionic acidaemia.

Protein Glycosylation and Diseases: Blood and Urinary Oligosaccharides as Markers for Diagnosis and Therapeutic Monitoring

N- and O-oligosaccharide variants on glycoproteins (glycoforms) can lead to alterations in protein activity or function that may manifest themselves as overt disease. This review summarizes those diseases that are known to be the result of an inherited or acquired glycoprotein oligosaccharide structural alteration and that are diagnosed in blood or urine by chemical characterization of that oligosaccharide alteration. The biochemical synthesis steps and catabolic pathways important in determining glycoprotein function are outlined with emphasis on alterations that lead to modified function. Clinical and biochemical aspects of the diagnosis are described for inherited diseases such as I-cell disease, congenital disorders of glycosylation, leukocyte adhesion deficiency type II, hereditary erythroblastic multinuclearity with a positive acidified serum test, and Wiskott-Aldrich syndrome. We also review the laboratory use of measurements of glycoforms related to acquired diseases such as alcoholism and cancer. Identification of glycoprotein glycoforms is becoming an increasingly important laboratory contribution to the diagnosis and management of human diseases as more diseases are found to result from glycan structural alterations.