Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

GUSB, the gene for beta-glucuronidase, has been localized to the proximal long arm of chromosome 7 between 7q11.2 and 7q22. Deficiency of beta-glucuronidase results in mucopolysaccharidosis type VII (MPS VII, Sly syndrome). The enzymatic defect has been demonstrated in cultured skin fibroblasts, leukocytes and serum of affected patients. An 8-yr-old boy presented with manifestations similar to MPS VII (mental retardation, short stature, "coarse" facial appearance, mild skeletal involvement and recurrent lower respiratory tract infection) but other, discrepant abnormalities, e.g., bilateral iris colobomata and cleft palate. Normal activity of beta-glucuronidase was found in the patient's leukocytes. Chromosome analysis disclosed an interstitial deletion of 7q with one breakpoint at the interface between bands 11.22 and 11.23 and the other breakpoint within band 21.1. DNA from this patient's leukocytes was analyzed for dosage of GUSB sequences. This locus appeared to be present at the normal diploid level. These findings suggest that GUSB is not in the portion of chromosome 7 deleted in our case, narrowing the smallest region of overlap to 7q21.1----7q22. We therefore assign the beta-glucuronidase gene to 7q21.1----7q22.
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PMID:Deletion mapping of the beta-glucuronidase gene. 337 95

Many metabolic diseases affecting the central nervous system are refractory to treatment because the blood-brain barrier restricts entry of therapeutic molecules. It may be possible to deliver therapeutic gene products directly to the brain by transplantation of neural progenitor cells, which can integrate into the murine central nervous system in a cytoarchitecturally appropriate manner. We tested this approach in mucopolysaccharidosis VII (Sly disease), a lysosomal storage disorder of humans, dogs and mice caused by an inherited deficiency of beta-glucuronidase. Lysosomal accumulation of glycosaminoglycans occurs in the brain and other tissues, causing a fatal progressive degenerative disorder, including mental retardation. Treatments are designed to provide a source of normal enzyme for uptake by diseased cells. We report here that by transplanting beta-glucuronidase-expressing neural progenitors into the cerebral ventricles of newborn mice, donor cells engrafted throughout the neuraxis. At maturity, donor-derived cells were present as normal constituents of diverse brain regions. beta-Glucuronidase activity was expressed along the entire neuraxis, resulting in widespread correction of lysosomal storage in neurons and glia in affected mice.
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PMID:Neural progenitor cell engraftment corrects lysosomal storage throughout the MPS VII mouse brain. 788 77

The genetic mucopolysaccharidoses (MPS) are a family of lysosomal storage diseases resulting from the partial catabolism of several glycosaminoglycans (GAGs). Depending on the particular enzyme deficient in activity, the MPS syndromes are defined into groups MPS I through VII, with several subgroups for a total of 10 disorders. In humans, clinical features include dysostosis multiplex, hepatosplenomegaly, hypertelorism, macroglossia, hypoplastic and irregularly shaped teeth, hyperplastic lips and gingiva, facial dysmorphia, corneal clouding, and mental retardation. MPS I (alpha-L-iduronidase deficiency) and VI (arylsulfatase B deficiency) have been described in cats, MPS VII (beta-glucuronidase deficiency) in dogs. Biochemically, these syndromes appear the same as their human counterparts and have similar clinical characteristics. All are inherited as autosomal recessive traits. The purpose of this study was to analyze the craniofacial aspects of these diseases in the animal models and compare these data with descriptions of the human syndromes. A total of 28 live animals were examined. Thirty-one skulls prepared from postmortem specimens were measured directly and radiographed. Controls were closely related family members of the same sex and similar age without the disease, clinically or biochemically. The data indicated that, as in the human syndromes, each is distinct, and the skull bones most severely affected are those of endochondral origin.
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PMID:Craniofacial abnormalities in animal models of mucopolysaccharidoses I, VI, and VII. 800 22

A deficiency of beta-glucuronidase (GUSB) causes the multisystem progressive degenerative syndrome, mucopolysaccharidosis (MPS) type VII (Sly disease), which includes mental retardation. Animal homologues of MPS VII (ref. 3, 4) are models for testing somatic gene transfer approaches to treat the central nervous system in this and other lysosomal storage disorders. Previous attempts to correct murine MPS VII by gene therapy have successfully treated lesions in some organs but not in the brain. Other experimental modalities have forestalled some disease progression in the brain, but only if done at birth, before the onset of severe lesions, when the animals are phenotypically normal. We tested whether therapeutic amounts of GUSB could be delivered to the diseased adult brain by transplanting cells engineered to super-secrete the normal enzyme for export to surrounding neural tissues. Lysosomal distention was cleared from neurons and glial cells in the vicinity of the grafts, showing that the secreted enzyme could reach the diseased cells and reverse lesions in the severely diseased brain. The ability to correct established lesions will be important for the treatment of many lysosomal storage diseases affecting the brain, because most patients are not diagnosed until lesions are advanced enough to affect phenotype or developmental milestones in early childhood, and some forms of the diseases do not become apparent until later in life.
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PMID:Decreased lysosomal storage in the adult MPS VII mouse brain in the vicinity of grafts of retroviral vector-corrected fibroblasts secreting high levels of beta-glucuronidase. 921 92

Mucopolysaccharidosis type VII (MPS VII; Sly syndrome) is one of a group of lysosomal storage diseases that share many clinical features, including mental retardation and hearing loss. Lysosomal storage in neurons of the brain and the associated behavioral abnormalities characteristic of a murine model of MPS VII have not been shown to be corrected by either bone marrow transplantation or gene therapy. However, intravenous injections of recombinant beta-glucuronidase initiated at birth reduce the pathological evidence of disease in MPS VII mice. In this study we present evidence that enzyme replacement initiated at birth improved the behavioral performance and reduced hearing loss in MPS VII mice. Enzyme-treated MPS VII mice performed similarly to normal mice and significantly better than mock- treated MPS VII mice in every phase of the Morris Water Maze test. In addition, the auditory function of treated MPS VII mice was dramatically improved, and was indistinguishable from normal mice. These data indicate that some of the learning, memory, and hearing deficits can be prevented in MPS VII mice if enzyme replacement therapy is initiated early in life. These data also provide functional correlates to the biochemical and histopathological improvements observed after enzyme replacement therapy.
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PMID:Enzyme replacement therapy for murine mucopolysaccharidosis type VII leads to improvements in behavior and auditory function. 952 82

Most lysosomal storage diseases, including mucopolysaccharidosis, affect the central nervous system (CNS). They often induce severe and progressive mental retardation. Replacement therapy by purified enzyme infusions is a promising approach for the treatment of peripheral organs but without effect on CNS pathology because the enzyme cannot cross the blood-brain barrier. Intracranial injection of recombinant adeno-associated virus (AAV) vectors offers an alternative for sustained local enzyme delivery from genetically engineered cells. We stereotactically injected an AAV vector containing the human beta-glucuronidase cDNA into the striatum of adult mice severely affected by mucopolysaccharidosis type VII at the time of treatment. Six weeks later, beta-glucuronidase activity in the injected hemisphere was comparable to that of heterozygous mice, which have a normal phenotype. Areas staining positive for enzyme activity enlarged with time, representing more than 10% of the hemisphere volume by 16 weeks. A complete reversion of lysosomal storage lesions was evident in these areas, as well as in most neurons located in surrounding negative areas and in the noninjected hemisphere. Thus, a single intracerebral injection of AAV vectors could achieve a broad and sustained lysosomal enzyme delivery, allowing for stable reversion of storage lesions in a significant fraction of the adult brain.
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PMID:Long-term and significant correction of brain lesions in adult mucopolysaccharidosis type VII mice using recombinant AAV vectors. 1093 13

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.
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PMID:Intracranial injection of recombinant adeno-associated virus improves cognitive function in a murine model of mucopolysaccharidosis type VII. 1127 77

In 471 adult mentally retarded adult patients (mean age 46 years; 92.6% males) living in an institution for the mentally retarded, a clinical examination, cytogenetic and molecular studies were done. 306 patients were screened for metabolic disorders. In 7 additional patients a metabolic disorder (phenylketonuria (n = 5), mucopolysaccharidosis type III (Sanfilippo syndrome, type A) (n = 1) and mucopolysaccharidosis type VII (Sly syndrome) (n = 1)) was diagnosed in the past. The abnormal metabolic findings in this group of 313 patients were classified in three categories and the clinical findings are reported: 1. metabolic disorders as the cause of mental retardation (MR), 2. metabolic disorders not explaining the MR, and 3. metabolic abnormalities of unknown significance. The first two groups included 16 patients, i.e. 26.2% of the group of monogenic disorders and 3.4% of the total population: phenylketonuria (PKU) (n = 5), S-sulfocysteinuria (n = 3), mucopolysaccharidosis type III (Sanfilippo syndrome, type A) (n = 1) and Gm1-gangliosidosis type 3 (n = 1) (first group), and mucopolysaccharidosis type VII (Sly syndrome) (n = 1), Niemann-Pick syndrome, type B (n = 1), cystinuria (n = 1) and hyperprolinemia type 1 (n = 3) (second group). The third group included patients with citrullinemia (n = 2), methionine sulphoxide reductase deficiency (n = 1), ornithinemia (n = 1), glycinuria (n = 20), neuraminaciduria (n = 8), uraciluria (n = 6) and diabetes mellitus (n = 2). Screening for Congenital Disorders of Glycosylation (CDG) in 144 patients and for Smith-Lemli-Opitz syndrome (SLO) in a selected group of 6 patients was normal. Of the total group of 306 patients screened for inborn errors of metabolism, only 5 (1.6%) were found with a true metabolic disorder. These 5 patients presented clinical symptoms, neurodegenerative or behavioural problems, indicating further metabolic screening. The present study illustrates that a selected group of patients with mental retardation of unknown origin are candidates for metabolic screening, especially if aberrant behaviour, neurodegenerative problems or dysmorphic features are present.
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PMID:Metabolic studies in older mentally retarded patients: significance of metabolic testing and correlation with the clinical phenotype. 1133 72

Mucopolysaccharidosis type VII (MPS VII) is a heritable lysosomal storage disease caused by a deficiency in beta-glucuronidase (GUSB) activity, leading to progressive accumulation of undegraded glycosaminoglycans in many tissues. Clinical features include growth and mental retardation, hearing and visual defects, shortened lifespan, and skeletal deformities. A murine model of MPS VII has been described that shares many of the manifestations of the human disease, including the skeletal dysplasia. In this study we describe abnormalities in the cellular morphology and function of osteoclasts and a localized defect in bone formation rate in the MPS VII mouse. Ultrastructural analysis revealed that MPS VII osteoclasts fail to form ruffled border membranes and many appeared to be detached from the bone surface. Following bone marrow transplantation, osteoclasts derived from wild-type donors showed normal morphology and were closely associated with the bone surface in MPS VII recipients. In vitro bone resorption assays demonstrated that MPS VII osteoclasts formed significantly smaller and fewer pits than those formed by osteoclasts derived from normal mice of the same strain. Although osteoclast morphology and function appeared to be abnormal in the MPS VII mouse, interleukin-1 (IL-1)-induced osteoclastogenesis in vivo was not affected. In addition to the osteoclast defects, MPS VII mice demonstrated a slower rate of bone matrix deposition in the epiphysis by in vivo calcein labeling experiments. These data suggest that abnormal morphology and function of MPS VII osteoclasts, combined with deficient matrix deposition, may contribute to the skeletal defects observed in this lysosomal storage disease.
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PMID:Abnormal osteoclast morphology and bone remodeling in a murine model of a lysosomal storage disease. 1185 42

Mucopolysaccharidosis type VII (MPS VII, Sly syndrome) is caused by dysfunction of the acid hydrolase beta-D-glucuronidase. The defect results in the accumulation of incompletely degraded glycosaminoglycans within lysosomes of a wide array of cell types. MPS VII is associated with mixed (conductive and sensorineural) hearing loss, vision defects, shortened stature, mental retardation and decreased lifespan. Whether the sensorineural component of hearing loss in MPS VII involves degeneration of cochlear sensory cells is not yet clear. The MPS VII mouse resembles its human counterpart in all major aspects, and has been the focus of extensive research seeking to correct MPS VII and other lysosomal storage diseases. The value of potential treatments for this hearing loss can be determined only if cochlear pathology in this model is well characterized. We examined threshold sensitivity, frequency tuning, hair cell density and the appearance of the cochlea and vestibular organs in MPS VII mice ranging from 1.0 to 7.5 months of age. At all ages, lysosomal storage is pronounced within cells of spiral limbus, spiral prominence, spiral ligament and glial cells, but not within organ of Corti, stria vascularis, or neurons. Within the vestibular maculae and cristae, both hair cells and supporting cells also show lysosomal storage. Although hearing thresholds are never normal, reduction in the sharpness of frequency tuning is not apparent until 2.5 months of age, suggesting that the sensorineural component of hearing loss begins in adulthood. No evidence was found for cell loss within the organ of Corti, or any other structure, however. Our results suggest that sensorineural hearing loss in the MPS VII mouse is not caused by degeneration, but may arise from alterations in mass and stiffness of cochlear structures or impaired sensory cell function. They also indicate a possible vestibular component in MPS VII.
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PMID:Inner ear pathology in the mucopolysaccharidosis VII mouse. 1212 41


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