Correction of metachromatic leukodystrophy in the mouse model by transplantation of genetically modified hematopoietic stem cells.
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Gene-based delivery can establish a sustained supply of therapeutic proteins within the nervous system. For diseases characterized by extensive CNS and peripheral nervous system (PNS) involvement, widespread distribution of the exogenous gene may be required, a challenge to in vivo gene transfer strategies. Here, using lentiviral vectors (LVs), we efficiently transduced hematopoietic stem cells (HSCs) ex vivo and evaluated the potential of their progeny to target therapeutic genes to the CNS and PNS of transplanted mice and correct a neurodegenerative disorder, metachromatic leukodystrophy (MLD). We proved extensive repopulation of CNS microglia and PNS endoneurial macrophages by transgene-expressing cells. Intriguingly, recruitment of these HSC-derived cells was faster and more robust in MLD mice. By transplanting HSCs transduced with the arylsulfatase A gene, we fully reconstituted enzyme activity in the hematopoietic system of MLD mice and prevented the development of motor conduction impairment, learning and coordination deficits, and neuropathological abnormalities typical of the disease. Remarkably, ex vivo gene therapy had a significantly higher therapeutic impact than WT HSC transplantation, indicating a critical role for enzyme overexpression in the HSC progeny. These results indicate that transplantation of LV-transduced autologous HSCs represents a potentially efficacious therapeutic strategy for MLD and possibly other neurodegenerative disorders. (+info)
Very low arylsulfatase A and cerebroside sulfatase activities in leukocytes of healthy members of metachromatic leukodystrophy family.
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Very low levels of arylsulfatase A (ASA) have been found in the leukocytes of healthy members of a metachromatic leukodystrophy (MLD) family. The cerebroside sulfate sulfatase (CSS) activities in the same individuals are about 10% of the control level. Arguments favoring a dominant mutation different from that of classical MLD are presented. This report reinforces the relationship between the two enzymatic activities. (+info)
Adult metachromatic leukodystrophy: disorganized schizophrenia-like symptoms and postpartum depression in 2 sisters.
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We describe the cases of 2 sisters with adult metachromatic leukodystrophy (MLD). Whereas one sister presented with disorganized schizophrenia-like symptoms as the initial manifestation of MLD, the other remained symptom free except for a 4-week period of postpartum depression. In both patients, there was some residual activity of leukocyte arylsulfatase A (1.7% and 5.5% of normal), and a marked increase in urinary sulfatides was present, as measured by tandem mass spectrometry. An arylsulfatase A pseudodeficiency was therefore excluded. The most common mutations of the adult phenotype, Ile-179-Ser and Pro-426-Leu, were not found. In the literature, only 1 case of adult MLD manifesting as disorganized schizophrenia-like symptoms has been described, whereas postpartum depression has been so far unknown as a presenting symptom of MLD. (+info)
Missense mutations as a cause of metachromatic leukodystrophy. Degradation of arylsulfatase A in the endoplasmic reticulum.
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Metachromatic leukodystrophy is a lysosomal storage disorder caused by a deficiency of arylsulfatase A (ASA). Biosynthesis studies of ASA with various structure-sensitive monoclonal antibodies reveal that some epitopes of the enzyme form within the first minutes of biosynthesis whereas other epitopes form later, between 10 and 25 min. When we investigated 12 various ASAs, with amino acid substitutions according to the missense mutations found in metachromatic leukodystrophy patients, immunoprecipitation with monoclonal antibodies revealed folding deficits in all 12 mutant ASA enzymes. Eleven of the 12 mutants show partial expression of the early epitopes, but only six of these show, in addition, incomplete expression of late epitopes. In none of the mutant enzymes were the late forming epitopes found in the absence of early epitopes. Thus, data from the wild-type and mutant enzymes indicate that the enzyme folds in a sequential manner and that the folding of early forming epitopes is a prerequisite for maturation of the late epitopes. All mutant enzymes in which the amino acid substitution prevents the expression of the late forming epitopes are retained in the endoplasmic reticulum (ER). In contrast, all mutants in which a single late epitope is at least partially expressed can leave the ER. Thus, irrespective of the missense mutation, the expression of epitopes forming late in biosynthesis correlates with the ability of the enzyme to leave the ER. The degradation of ER-retained enzymes can be reduced by inhibitors of the proteasome and ER alpha1,2-mannosidase I, indicating that all enzymes are degraded via the proteasome. Inhibition of degradation did not lead to an enhanced delivery from the ER for any of the mutant enzymes. (+info)
Histopathologic correlates of radial stripes on MR images in lysosomal storage disorders.
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BACKGROUND AND PURPOSE: Radially oriented hypointense stripes in hyperintense cerebral white matter are recognized on T2-weighted images of certain lysosomal storage disorders. We compared in vivo and postmortem MR imaging with histopathologic findings in three patients with metachromatic leukodystrophy (MLD), globoid cell leukodystrophy (GLD), and infantile GM1 gangliosidosis (GM1) to understand this characteristic MR imaging pattern. METHODS: The in vivo MR imaging protocol comprised T1- and T2-weighted spin-echo and fluid-attenuated inversion recovery imaging. Postmortem MR imaging, including coronal 1-cm-thick brain sections, was performed after at least 5 weeks of formalin fixation and included T2-weighted spin-echo images and 3D fluid-attenuated inversion recovery images with high spatial resolution. Afterward, the sections were embedded in paraffin, whole-mount sections were made, and neuropathologic stains were applied. RESULTS: Similar imaging features were found in the three patients on in vivo and postmortem images, with more prominent stripes in GLD and MLD than in GM1. Neuropathologic examination revealed that the stripes were related to relative sparing of myelin in the perivenular regions in GM1 and MLD, but lipid-containing glial cells were also present in these areas in MLD. Perivenular clusters of globoid cells containing lipid material in absence of any myelin corresponded to the stripes in GLD. CONCLUSION: Results of our postmortem study showed that radial stripes of white matter on MR images represented relative myelin sparing in some lysosomal storage disorders, but they may also represent lipid storage. (+info)
Enzyme replacement improves nervous system pathology and function in a mouse model for metachromatic leukodystrophy.
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A deficiency of arylsulfatase A (ASA) causes the lysosomal storage disease metachromatic leukodystrophy, which is characterized by accumulation of the sphingolipid 3-O-sulfogalactosylceramide (sulfatide). Sphingolipid storage results in progressive demyelination and severe neurologic symptoms. The disease is lethal, and curative therapy is not available. To assess the therapeutic potential of enzyme replacement therapy (ERT), ASA knockout mice were treated by intravenous injection of recombinant human ASA. Plasma levels of ASA declined with a half-time of approximately 40 min, and enzyme was detectable in tissues within minutes after injection. The uptake of injected enzyme was high into liver, moderate into peripheral nervous system (PNS) and kidney and very low into brain. The apparent half-life of endocytosed enzyme was approximately 4 days. A single injection led to a time- and dose-dependent decline of the excess sulfatide in PNS and kidney by up to 70%, but no reduction was seen in brain. Four weekly injections with 20 mg/kg body weight not only reduced storage in peripheral tissues progressively, but also were surprisingly effective in reducing sulfatide storage in brain and spinal cord. The histopathology of kidney and central nervous system was ameliorated. Improved neuromotor coordination capabilities and normalized peripheral compound motor action potential demonstrate the benefits of ERT on the nervous system function. Enzyme replacement may therefore be a promising therapeutic option in this devastating disease. (+info)
Adult metachromatic leukodystrophy with an unusual relapsing-remitting course.
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A 46 year old woman had a relapsing-remitting course of hemiparesis, disorientation, paraparesis and seizures, followed by progressive dementia, spasticity and ataxia. Computed tomography at onset showed a parietotemporal hypodense area with diffuse mottled enhancement obliterating the lateral ventricle. Subsequent scans demonstrated symmetric periventricular non-enhancing hypodensities, progressive ventricular enlargement and atrophy. Adult metachromatic leukodystrophy was diagnosed on the basis of low leukocyte arylsulphatase A level and metachromatic material accumulation at neural nerve biopsy. (+info)
Peripheral neuropathy in metachromatic leucodystrophy. A study of 40 cases from south India.
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BACKGROUND: There is a paucity of literature from India on metachromatic leucodystrophy (MLD), a rare metabolic disorder of childhood resulting from aryl sulfatase A (ASA) deficiency.Patients/ METHODS: Case records of histopathologically verified cases of MLD, evaluated over a period of 12 years at the National Institute of Mental Health and Neurosciences, Bangalore, India, were reviewed. RESULTS: The late infantile group (36) manifested with regression of milestones (all), delayed mile stones (14), gait abnormalities (14), and seizures (11). Despite spasticity (29), there was hypo/areflexia in 25 patients. Optic atrophy (six) was rare. Consanguinity was noted in 25 children and four had a history of similar illness in siblings. Behavioural problems dominated in the juvenile group (four), but associated cognitive decline and hyporeflexia provided a clue to the diagnosis. Low serum ASA (seven of 20), raised cerebrospinal fluid protein (five of 12), and urinary metachromatic granules (two of 32) were infrequent. Electrophysiological evidence of severe demyelinating and length dependent sensory motor neuropathy was observed in all, even in the presence of hyper-reflexia. In addition to metachromatic dysmyelinating neuropathy in all patients, sural nerve biopsy in 20 patients revealed orthochromatic deposits within perivascular macrophages, particularly among those patients with normal ASA values (11 of 14), suggesting the accumulation of other glycosphingolipids. CONCLUSIONS: This study produced some noteworthy observations: the high degree of consanguinity associated with MLD in India, the existence of MLD with normal serum concentrations of ASA, the deposition of orthochromatic lipids, and electrophysiological evidence of a partial conduction block. (+info)