Gaucher Disease: Our primary interest is to understand the pathogenesis of the neurological involvement in this disease and to test novel therapeutic approaches. In collaboration with our Israeli colleagues we showed that agonist-induced calcium-release is significantly enhanced in brain microsomes from the acute neuronopathic form of Gaucher disease (type 2). These findings suggest that defective calcium homeostasis may be a mechanism responsible for neuropathophysiology in Gaucher disease. This mechanism may enable the development of novel therapeutic approaches. We have further delineated the pathologic and clinical abnormalities of the variant of Gaucher disease with parkinsonism. We found that patients with type 1 GD and parkinsonism had numerous synuclein positive inclusions, similar to brainstem-type Lewy bodies found in Parkinson disease, were also found in hippocampal CA2-4 neurons. We identified ten unrelated families of patients with Gaucher disease were obligate or confirmed carriers of glucocerebrosidase mutations developed parkinsonism. These observations indicate that mutant glucocerebrosidase, even in heterozygotes, may be a risk factor for the development of parkinsonism. Understanding the relationship between altered glucocerebrosidase and the development of parkinsonian manifestations are likely to provide insights into the genetics, pathogenesis and treatment of Parkinson disease as well as Gaucher disease. We completed the accrual of patients for a randomized controlled trial of OGT 918 (N-Butyldeoxynojirimycin, Zaveska) for the treatment of patients with neuronopathic Gaucher disease. In this study we are testing the hypothesis that substrate reduction will reverse the neurological abnormalities, and in particular the slow eye movements of these patients. Thus far, this medication is well tolerated and the levels of the drug in the cerebrospinal fluid are up to 66% of its concentration in plasma, suggesting that the brain is exposed to effective amounts of this glycolipid synthesis inhibitor. Fabry Disease: One of the major goals of the Branch is to develop effective treatment for patients with hereditary neurometabolic disorders. Second to Gaucher disease, the most prevalent condition in this category is Fabry disease. Patients with this disorder have a severely painful peripheral neuropathy, premature strokes and myocardial infarctions, and ultimately, complete renal failure. We have been exploring enzyme replacement therapy (ERT) for Fabry disease. Patients treated for up to 3.5 years, had significant reduction in pain, improvement in sensing cold and warm and in their sweat function. However, ERT did not reduce the incidence of stroke. We therefore performed extensive studies on the pathogenesis of stroke in Fabry disease. We found that the white matter brain lesions occur in ?prior? hypometabolic and hyperperfused brain regions. We further found that this hyperperfusion is reduced by infusions of vitamin C. This finding and the low vitamin C blood level in these patients suggest that increased cerebrovascular perfusion is associated with increased production of reactive oxygen species. We also found markedly elevated blood myeloperoxidase in Fabry disease, a potential pathogenic marker for the disease and its response to treatment. Further indication of reactive oxygen species production was found in the markedly increased staining for 4-nitrotyrosine in dermal blood vessels compared to unaffected controls. These abnormalities were significantly improved but did not completely normalize by enzyme replacement therapy. We also recently found evidence for accelerated atherosclerosis in patients. These observations have implications regarding oxidative processes contributing to accelerated atherosclerosis in Fabry disease, and should contribute to the general understanding of both pathologies. In view of the incomplete response of adult patients to ERT we hypothesized that initiation of ERT during childhood will improve the outcome of these patients. We therefore began an ERT study in pediatric Fabry patients. Initial observations indicate that ERT is safe, decreases pain and improves sweating and quality of life in children 7-17 years of age with Fabry disease. Mucolipidosis IV: We investigated 35 patients with this autosomal recessive neurogenetic disorder and identified mutations the protein mucolipin in all of them. All of the patients had a constitutive achlorhydria with elevated plasma gastrin level, and 12 had iron deficiency anemia. MRI of the head showed consistent characteristic findings of a thin corpus callosum. This condition remained unchanged during the follow-up period extending over several years. Prominent abnormalities of speech, hand-usage, and swallowing were also noted. Correlation of the genotype with the neurological handicap and the degree of dysplasia of the corpus callosum was observed. We identified 21 mutations in this disease. In one family we found an in-frame insertion of a 93bp segment from mitochondrial NADH dehydrogenase 5. This is the first identification of an inherited transfer of mitochondrial nuclear DNA causing a genetic disease. Using electroretinography and visual evoked potential we quantified the decline of retinal function in MLIV. This ongoing study will be useful to identify the optimal stage for therapeutic intervention to prevent progression of the retinal dystrophy in MLIV. It is therefore evident that mucolipidosis IV is both a developmental and a degenerative disorder. The presentation as a cerebral palsy-like encephalopathy may delay the correct diagnosis of this condition. Leukodystrophies: We demonstrated mutations in subunits of the eucaryotic initiation factor 2B (eIF2B) in patients with a leukodystrophy that was first identified by DMNB in 1994 which at the time was called Childhood Ataxia with CNS Hypomyelination (CACH). Patients with CACH develop a progressive neurological deterioration in childhood, adolescence and sometimes in adulthood. The clinical decline is often initiated or worsens after stresses such as a mild head trauma or an intercurrent febrile illness. eIF2B is a protein complex that is essential for the regulation of protein synthesis, particularly in response to stress. Over the past year we showed that the eIF2B mutations lead to decreased guanine nucleotide exchange factor activity in transformed lymphoblasts from patients. A lower eIF2B activity was associated with earlier onset of clinical disease. We also found that the disease severity significantly correlated with age of onset but not with the type of the mutated subunit or with the position of the mutation within the protein. Nevertheless, mutations R113H in the epsilon subunit and E213G in the beta subunit were associated with significantly milder forms. We also found that patients with another leukodystrophy we described in 1997 and termed ovarioleukodystrophy also have mutations in subunits of the protein eIF2B. This neurogenetic complex comprises one of the most common leukodystrophy syndromes. We also found that insertion of mutant proteolipid protein results in misdistribution of myelin proteins in the myelin sheath, thus discovering a novel mechanism by which a mutant protein can affect the entire organization of myelin structure. Finally, we identified two additional leukodystrophy syndromes with distinct patterns of white matter abnormalities on cerebral MRI. One of these combines a leukodystrophy and hypogonadotrphic hypogonadism and is associated with peripheral nervous system dysmyelination. It is likely that these investigations will lead to a better understanding of myelination and maintenance of the myelin sheath.
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