Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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Mucopolysaccharidosis Type I (MPS I) is the lysosomal storage disease caused by the deficient activity of alpha-L-iduronidase (IDUA). In man, MPS I can occur in severe, mild, or intermediate forms known as the Hurler, Scheie, or Hurler/Scheie syndromes, respectively. MPS I also has been described in cats, dogs, and mice. This manuscript reports the identification and characterization of the mutation causing MPS I in cats. To obtain wild-type feline IDUA cDNAs, two PCR-based strategies were used. PCR primers were constructed from a conserved region of the published human and dog sequences and used to amplify a 224-bp IDUA fragment from normal cat genomic DNA. This fragment was then used to screen a feline uterus cDNA library. PCR also was used to directly amplify IDUA fragments from the same cDNA library. Two overlapping feline IDUA cDNAs encoding 466 amino acid residues of the feline IDUA polypeptide ( approximately 85% of the mature protein based on comparison to the human, dog, and mouse sequences) were obtained by these strategies. To identify the mutation causing MPS I in cats, DNA sequencing was carried out on the corresponding IDUA region from several affected animals. A 3-bp deletion was found on both IDUA alleles in each of the MPS I animals, predicting the deletion of a single aspartate residue from the feline IDUA polypeptide. To confirm the authenticity of this mutation, heteroduplex, SSCP, and transient expression studies were carried out. Over 100 animals from the MPS I colony were screened for the presence of the mutation by heteroduplex and SSCP analyses-in all cases the presence of the 3-bp deletion was 100% concordant with the disease phenotype. For transient expression studies, the two partial, overlapping feline cDNAs were combined and joined in-frame to the 5' end of the canine IDUA cDNA. This wild-type, hybrid cDNA expressed IDUA activity up to sixfold over endogenous levels after transfection into COS-1 cells. A modified full-length IDUA cDNA containing the 3-bp deletion did not express IDUA activity in a transient expression system, providing proof that this lesion was the cause of feline MPS I.
Mol Genet Metab 1999 Jun
PMID:Identification and characterization of the molecular lesion causing mucopolysaccharidosis type I in cats. 1035 9

Metachromatic leukodystrophy (MLD) is a lysosomal storage disease resulting from the deficient activity of arylsulfatase A (ASA) and the accumulation of sulfatides. The disease is characterized by several subtypes, designated by age at onset: the late-infantile-, juvenile-, and adult-onset variants. Mutation analysis of genomic DNA from a proband with each variant was performed to identify and characterize their causative ASA mutations. Two sisters with the infantile-onset disease were homoallelic for the missense mutation D335V, a juvenile-onset proband was heteroallelic for two novel missense mutations, P148L and P191T, and an adult-onset patient was heteroallelic for the H397Y and P426L mutations. The novel mutations were not identified in 108 normal alleles indicating that these base substitutions were not common polymorphisms. To further characterize the mutant gene products, the mutant enzymes were partially purified from cultured fibroblasts and their molecular weights and charges were compared by immunoblotting following SDS-PAGE or isoelectric focusing (IEF). Normal fibroblast ASA had a single, broad band at 54 kDa. The enzyme from the late-infantile-onset patient had distinct bands of 36 and 78 kDa, but lacked the normal 54-kDa species. The juvenile- and adult-onset patients each had a faint band of 54 kDa and several other bands ranging from 29 to 64 kDa. IEF revealed several bands for the partially purified normal enzyme with a relatively narrow pH range around 4.0, whereas numerous bands with a wider range of isoelectric points were observed with the enzymes from the juvenile- and adult-onset fibroblasts. In contrast, the enzyme from the late-infantile-onset proband had four bands with more acidic isoelectric points, none corresponding to those of the normal enzyme. These results document changes in both size and charge of the mutant enzymes from patients with different mutations and MLD subtypes.
Mol Genet Metab 1999 Jul
PMID:Metachromatic leukodystrophy: subtype genotype/phenotype correlations and identification of novel missense mutations (P148L and P191T) causing the juvenile-onset disease. 1038 28

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.
Hum Mol Genet 1999 Aug
PMID:Targeted disruption of the lysosomal alpha-mannosidase gene results in mice resembling a mild form of human alpha-mannosidosis. 1040 Sep 83

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder in which oculocutaneous albinism, bleeding tendency and a ceroid-lipofuscin lysosomal storage disease result from defects of multiple cytoplasmic organelles: melanosomes, platelet dense granules and lysosomes. The HPS polypeptide, a 700 amino acid protein which is unrelated to any known proteins, is likely to be involved in the biogenesis of these different organelles. Here, we show that HPS is a non-glycosylated, non-membrane protein which is a component of two distinct high molecular weight complexes. In non-melanotic cells the HPS protein is contained almost entirely in an approximately 200 kDa complex that is widely distributed throughout the cytosol. In melanotic cells the HPS protein is partitioned between this cytosolic complex and a >500 kDa complex that appears to consist of the approximately 200 kDa complex in association with membranous components. Subcellular fractionation, immunofluorescence and immunoelectron microscopy studies indicate that the membrane-associated HPS complex of melanotic cells is associated with tubulovesicular structures, small non-coated vesicles, and nascent and early-stage melanosomes. These findings suggest that the HPS complex is involved in the biogenesis of early melanosomes.
Hum Mol Genet 2000 Feb 12
PMID:The Hermansky-Pudlak syndrome (HPS) protein is part of a high molecular weight complex involved in biogenesis of early melanosomes. 1065 47

Juvenile neuronal ceroid lipofuscinosis (JNCL), Batten disease, is an autosomal recessive lysosomal storage disease associated with mutations in CLN3. CLN3 has no known homology to other proteins and a function has not yet been described. The predominant mutation in CLN3 is a 1.02 kb genomic deletion that accounts for nearly 85% of the disease alleles. In this mutation, truncation of the protein by a premature stop codon results in the classical phenotype. Additional missense and nonsense mutations have been described. Some missense substitutions result in a protracted phenotype, with delays in the onset of classical clinical features, whereas others lead to classical JNCL. In this study, we examined the effect of naturally occurring point mutations on the intracellular localization of CLN3 and their ability to complement the CLN3-deficient yeast, btn1-Delta. We also examined a putative farnesylation motif thought to be involved in CLN3 trafficking. All of the point mutations, like wild-type CLN3, were highly associated with lysosome-associated membrane protein II in non-neuronal cells and with synaptophysin in neuronal cell lines. In the yeast functional assay, point mutations correlating with a mild phenotype also demonstrated CLN3 activity, whereas the mutations associated with severe disease failed to restore CLN3 function completely. CLN3 with a mutation in the farnesylation motif trafficked normally but was functionally impaired. These data suggest that these clinically relevant point mutations, causative of Batten disease, do not affect protein trafficking but rather exert their effects by impairing protein function.
Hum Mol Genet 2000 Mar 22
PMID:Batten disease: evaluation of CLN3 mutations on protein localization and function. 1074 80

Although renal disease is the most prominent feature of the lysosomal storage disease cystinosis, corneal cystine crystal formation remains a major complication, leading to photophobia, corneal erosions, and keratopathies. Moreover, the extent of corneal crystal accumulation reflects the course and severity of the disease itself, and the cornea is accessible to direct examination. Therefore, we employed a scoring system, based on a library of slit-lamp photographs of corneas with increasing crystal densities (0.00-3.00), to assess the degree of crystal accumulation in 170 patients with nephropathic cystinosis examined at the National Institutes of Health between 1976 and 2000. None of the patients had received topical cystine-depleting therapy at the time of the evaluation. In this natural history study, infants in the first year of life had absent or minimal corneal crystals, i.e., a corneal cystine crystal score (CCCS) of 0 or 0.25. However, the CCCS increased linearly with age, such that every patient had visible crystals by 16 months of age, and plateaued at approximately 3.00 by early adolescence. Longitudinal studies in representative patients support the cross-sectional results. Individuals homozygous for the common 57-kb deletion involving the cystinosis gene (CTNS) displayed the same course of corneal crystal accumulation as did individuals not bearing the large deletion. Patients with ocular or nonnephropathic cystinosis had CCCSs that were, in general, half those expected for patients with nephropathic cystinosis of the same age. Administration of 0.55% cysteamine eyedrops, given 6 to 12 times per day, dissolved corneal cystine crystals in 10 representative patients with nephropathic cystinosis aged 1 to 32 years within 8 to 41 months.
Mol Genet Metab
PMID:Corneal crystals in nephropathic cystinosis: natural history and treatment with cysteamine eyedrops. 1100 3

Gene therapy has been at least partially effective in several mouse disease models, but treatment of large mammals has been more difficult to achieve. One major limitation is that only low levels of expression of the corrective gene are often maintained in vivo. In a mouse model of the lysosomal storage disease mucopolysaccharidosis (MPS) type VII (Sly disease) with a null mutation in beta-glucuronidase, gene transfer experiments have shown that only 1-2% of normal beta-glucuronidase can correct the storage in some major organs. In contrast, MPS VII dogs, cats, and humans that have residual beta-glucuronidase activity levels in this range are affected. Thus, higher levels of transferred gene expression may be needed to achieve a therapeutic effect in large animals and humans. We tested this by examining liver pathology in MPS VII dogs after intraperitoneal transplantation of neo-organs containing retrovirus vector-corrected autologous fibroblasts that expressed low levels of beta-glucuronidase. The enzyme secreted from the neo-organs was taken up by the liver and significantly reduced the substrate content compared with untreated dogs. This suggests that small amounts of normal enzyme, when delivered to target tissues, may be therapeutically effective in human MPS VII patients.
Mol Ther 2000 Dec
PMID:Gene transfer of low levels of beta-glucuronidase corrects hepatic lysosomal storage in a large animal model of mucopolysaccharidosis VII. 1112 56

Hurler syndrome is the most severe form of a lysosomal storage disease caused by loss of the enzyme alpha-L-iduronidase (encoded by the IDUA gene), which participates in the degradation of glycosaminoglycans (GAGs) within the lysosome. In some populations, premature stop mutations represent roughly two-thirds of the mutations that cause Hurler syndrome. In this study we investigated whether the aminoglycoside gentamicin can suppress stop mutations within the IDUA gene. We found that a Hurler syndrome fibroblast cell line heterozygous for the IDUA stop mutations Q70X and W402X showed a significant increase in alpha-L-iduronidase activity when cultured in the presence of gentamicin, resulting in the restoration of 2.8% of normal alpha-L-iduronidase activity. Determination of alpha-L-iduronidase protein levels by an immunoquantification assay indicated that gentamicin treatment produced a similar increase in alpha-L-iduronidase protein in Hurler cells. Both the alpha-L-iduronidase activity and protein level resulting from this treatment have previously been correlated with mild Hurler phenotypes. Although Hurler fibroblasts contain a much higher level of GAGs than normal, we found that gentamicin treatment reduced GAG accumulation in Hurler cells to a normal level. We also found that a reduced GAG level could be sustained for at least 2 days after gentamicin treatment was discontinued. The reduction in the GAG level was also reflected in a marked reduction in lysosomal vacuolation. Taken together, these results suggest that the suppression of premature stop mutations may provide an effective treatment for Hurler syndrome patients with premature stop mutations in the IDUA gene.
Hum Mol Genet 2001 Feb 01
PMID:Gentamicin-mediated suppression of Hurler syndrome stop mutations restores a low level of alpha-L-iduronidase activity and reduces lysosomal glycosaminoglycan accumulation. 1115 48

Mucopolysaccharidosis type VII (MPS VII) is a lysosomal storage disease caused by the lack of beta-glucuronidase (GUSB) activity. GUSB deficiency leads to the progressive accumulation of undegraded glycosaminoglycans (GAGs) in cells of most tissues, including the brain, and is associated with mental retardation. Reduction of lysosomal storage in the central nervous system and prevention of cognitive dysfunction may require intracranial delivery of a therapeutic agent during the newborn period that provides a continuous source of GUSB. Therefore, we injected recombinant adeno-associated virus encoding human GUSB into both the anterior cortex and the hippocampus of newborn MPS VII mice. Total GUSB activity in the brain approached normal levels by 18 weeks. Although GUSB activity was concentrated near the injection sites, lysosomal distension was reduced in most areas of the brain. In addition to histopathologic evidence of GAG reduction, the previously undescribed accumulation of GM2 and GM3 gangliosides in the brain was also prevented. Furthermore, GUSB expression and reduced lysosomal distension correlated with improvements in cognitive function as measured in the Morris Water Maze test. These findings indicate that localized overexpression of GUSB has positive effects on the pathology and cognitive function and does not have overt toxicity.
Mol Ther 2001 Mar
PMID:Intracranial injection of recombinant adeno-associated virus improves cognitive function in a murine model of mucopolysaccharidosis type VII. 1127 77

A deficiency of functional aspartylglucosaminidase (AGA) causes a lysosomal storage disease, aspartylglucosaminuria (AGU). The recessively inherited disease is enriched in the Finnish population, where 98% of AGU alleles contain one founder mutation, AGU(Fin). Elsewhere in the world, we and others have described 18 different sporadic AGU mutations. Many of these are predicted to interfere with the complex intracellular maturation and processing of the AGA polypeptide. Proper initial folding of AGA in the endoplasmic reticulum (ER) is dependent on intramolecular disulfide bridge formation and dimerization of two precursor polypeptides. The subsequent activation of AGA occurs autocatalytically in the ER and the protein is transported via the Golgi to the lysosomal compartment using the mannose-6-phosphate receptor pathway. Here we use the three-dimensional structure of AGA to predict structural consequences of AGU mutations, including six novel mutations, and make an effort to characterize every known disease mutation by dissecting the effect of mutations on intracellular stability, maturation, transport and the activity of AGA. Most mutations are substitutions replacing the original amino acid with a bulkier residue. Mutations of the dimer interface prevent dimerization in the ER, whereas active site mutations not only destroy the activity but also affect maturation of the precursor. Depending on their effects on the AGA polypeptide the mutations can be categorized as mild, moderate or severe. These data contribute to the expanding body of knowledge pertaining to molecular pathogenesis of AGU.
Hum Mol Genet 2001 Apr 15
PMID:Molecular pathogenesis of a disease: structural consequences of aspartylglucosaminuria mutations. 1130 71


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