Satoshi Kono

Expanding the clinical phenotype of SNCA duplication carriers.

SNCA duplication is a recognized cause of familial Parkinsons disease (PD). We aimed to explore the genetic and clinical variability in the disease manifestation. Molecular characterization was performed using real‐time PCR, SNP arrays, and haplotype analysis. We further studied those patients who were found to harbor SNCA duplication with olfactory function tests, polysomnography, and PET. We identified four new families and one sporadic patient with SNCA duplication. Eleven symptomatic patients from these four families presented with parkinsonism, of which three subsequently developed dementia. The lifetime estimate of overall penetrance was 43.8%. FDG–PET study of symptomatic patients showed hypometabolism in the occipital lobe, whereas asymptomatic carriers of SNCA duplication demonstrated normal glucose metabolism. Symptomatic patients showed abnormal olfactory function and polysomnography and asymptomatic carriers showed normal results. The clinical features of SNCA duplication include parkinsonism with or without dementia. Asymptomatic carriers displayed normal test results with the eldest individual aged 79 years; thus, even a carrier of SNCA duplication may escape the development of PD. This difference in age‐associated penetrance may be due to the genetic background or environmental exposures. Further studies of SNCA duplication carriers will help identify disease‐modifiers and may open novel avenues for future treatment.

Mutations in a Thiamine-Transporter Gene and Wernicke's-like Encephalopathy

To the Editor: We report on two previously healthy Japanese brothers with a newly discovered recessively inherited syndrome similar to Wernickes encephalopathy that developed in the second decade ...

Iron accumulation in the liver of male patients with Wilson's disease

OBJECTIVES:There is accumulating evidence that ceruloplasmin, a copper protein with ferroxidase activity, plays an important role in iron metabolism. The genetic disorder, aceruloplasminemia, can lead to tissue storage of iron as in hemochromatosis. Because most patients with Wilsons disease, a genetic copper toxicosis, have hypoceruloplasminemia, some could be affected by iron overload.METHODS:Four male patients with Wilsons disease were enrolled in this study of pre- and post-treatment iron metabolism.RESULTS:Pretreatment copper contents of the liver were high in all four male patients studied as diagnostic of Wilsons disease. Genetic analysis supported their clinical diagnosis of Wilsons disease without a background of hemochromatosis. Pretreatment serum ceruloplasmin levels were <20 mg/dl in all four patients. A standard penicillamine treatment for 3–8.5 yr further decreased their serum ceruloplasmin levels. Post-treatment serum ferroxidase activity was low as was the serum ceruloplasmin protein. Copper contents in the liver decreased after treatment in all subjects. In contrast, nonheme iron in the liver increased during treatment. Pretreatment liver specimens were positive for histochemical iron in two patients, and post-treatment specimens were positive in all four patients. In two patients, serum aminotransferase levels rebounded with elevation of serum ferritin concentration during the treatment period. Subsequent iron reduction by phlebotomy ameliorated their biochemical liver damage.CONCLUSION:Iron overload related to hypoceruloplasminemia may be clinically important, particularly in male patients with Wilsons disease.

Cerebellar ataxia associated with heteroallelic ceruloplasmin gene mutation

Background: Aceruloplasminemia, an autosomal recessive disorder that affects human iron metabolism, is caused by mutation of the ceruloplasmin gene. Heterozygous individuals with a partial ceruloplasmin deficiency may have normal iron metabolism and no clinical symptoms. Methods: The authors clinically characterized three Japanese patients from two families who had cerebellar ataxia with hypoceruloplasminemia from the fourth decade of life. Genetic analysis, restriction fragment length polymorphism analysis, and a pathologic study were performed. Results: All three patients presented with cerebellar dysfunction that included relatively nondisabling gait ataxia and dysarthria, as well as hyperreflexia. Brain and abdomen MRI showed cerebellar atrophy and no low-signal intensities in the basal ganglia, thalamus, and liver. Direct mutational analysis excluded SCA-1, SCA-2, SCA-3, SCA-6, SCA-7, SCA-8, SCA-12, and DRPLA. The patients partially lacked serum ceruloplasmin, and the protein concentrations and ferroxidase activities ranged from 36% to 41% of the control values; moreover, they were heterozygous for a nonsense mutation of the ceruloplasmin gene (Trp858ter). Serum iron concentration and transferrin saturation were normal. At autopsy, pathologic and biochemical examinations showed marked loss of Purkinje cells, a large iron deposition in the cerebellum, and small depositions in the basal ganglia, thalamus, and liver. Conclusion: Cerebellar ataxia reflects the site of iron deposition. Being heterozygous for mutation of the ceruloplasmin gene may result in cerebellar ataxia.

Biological effects of mutant ceruloplasmin on hepcidin-mediated internalization of ferroportin.

Ceruloplasmin plays an essential role in cellular iron efflux by oxidizing ferrous iron exported from ferroportin. Ferroportin is posttranslationally regulated through internalization triggered by hepcidin binding. Aceruloplasminemia is an autosomal recessive disorder of iron homeostasis resulting from mutations in the ceruloplasmin gene. The present study investigated the biological effects of glycosylphosphatidylinositol (GPI)-linked ceruloplasmin on the hepcidin-mediated internalization of ferroportin. The prevention of hepcidin-mediated ferroportin internalization was observed in the glioma cells lines expressing endogenous ceruloplasmin as well as in the cells transfected with GPI-linked ceruloplasmin under low levels of hepcidin. A decrease in the extracellular ferrous iron by an iron chelator and incubation with purified ceruloplasmin in the culture medium prevented hepcidin-mediated ferroportin internalization, while the reconstitution of apo-ceruloplasmin was not able to prevent ferroportin internalization. The effect of ceruloplasmin on the ferroportin stability was impaired due to three distinct properties of the mutant ceruloplasmin: namely, a decreased ferroxidase activity, the mislocalization in the endoplasmic reticulum, and the failure of copper incorporation into apo-ceruloplasmin. Patients with aceruloplasminemia exhibited low serum hepcidin levels and a decreased ferroportin protein expression in the liver. The in vivo findings supported the notion that under low levels of hepcidin, mutant ceruloplasmin cannot stabilize ferroportin because of a loss-of-function in the ferroxidase activity, which has been reported to play an important role in the stability of ferroportin. The properties of mutant ceruloplasmin regarding the regulation of ferroportin may therefore provide a therapeutic strategy for aceruloplasminemia patients.

Measurement of serum hepcidin-25 levels as a potential test for diagnosing hemochromatosis and related disorders

BackgroundIron overload syndromes include a wide spectrum of genetic and acquired conditions. Recent studies suggest suppressed hepcidin synthesis in the liver to be the molecular basis of hemochromatosis. However, a liver with acquired iron overload synthesizes an adequate amount of hepcidin. Thus, hepcidin could function as a biochemical marker for differential diagnosis of iron overload syndromes.MethodsWe measured serum iron parameters and hepcidin-25 levels followed by sequencing HFE, HJV, HAMP, TFR2, and SLC40A1 genes in 13 Japanese patients with iron overload syndromes. In addition, we performed direct measurement of serum hepcidin-25 levels using liquid chromatography–tandem mass spectrometry in 3 Japanese patients with aceruloplasminemia and 4 Italians with HFE hemochromatosis.ResultsOne patient with HJV hemochromatosis, 2 with TFR2 hemochromatosis, and 3 with ferroportin disease were found among the 13 Japanese patients. The remaining 7 Japanese patients showed no evidence for genetic basis of iron overload syndrome. As far as the serum hepcidin-25 was concerned, seven patients with hemochromatosis and 3 with aceruloplasminemia showed markedly decreased serum hepcidin-25 levels. In contrast, 3 patients with ferroportin disease and 7 with secondary iron overload syndromes showed serum hepcidin levels parallel to their hyperferritinemia. Patients with iron overload syndromes were divided into 2 phenotypes presenting as low and high hepcidinemia. These were then associated with their genotypes.ConclusionDetermining serum hepcidin-25 levels may aid differential diagnosis of iron overload syndromes prior to genetic analysis.

Functional brain imaging in glucocerebrosidase mutation carriers with and without Parkinsonism

Mutations in the glucocerebrosidase gene (GBA) increase the risk for Parkinsons disease and are also associated with an earlier onset of the disease and an akinetic parkinsonian phenotype. To investigate the underlying pathogenesis of this condition, we assessed cerebral metabolism using positron emission tomography (PET) in GBA mutation carriers with and without parkinsonism. [18F]‐fluorodeoxyglucose (FDG)‐PET using a three‐dimensional stereotactic surface projection analysis was used to measure the cerebral metabolic rates of glucose (CMRGlc) in a patient with parkinsonism and Gaucher disease (GD) and five subjects with a heterozygous GBA mutation, including three patients with parkinsonism and three asymptomatic carriers in comparison to 10 healthy controls in the same age range. Dopaminergic neuronal activity was investigated using [11C] CFT‐ and [11C] raclopride‐PET. All GBA mutation carriers displayed a significant CMRGlc decrease in the supplemental motor area (SMA). The carriers with parkinsonism showed additional hypometabolism in the parietooccipital cortices. The CFT and raclopride PET images in the asymptomatic carriers demonstrated the CFT binding to be within normal values in the putamen and a significant increase was observed in the caudate nucleus while raclopride binding in the striatum was in the normal range. An advanced parkinsonian carrier showed decreased CFT binding and increased raclopride binding in the striatum. The decreased CMRGlc in the SMA was characteristic of the GBA mutation carriers. The hypometabolism in the SMA may, therefore, be involved in the clinical characteristics of parkinsonism associated with GBA mutations when the carriers manifest parkinsonism.

Direct Comparison of Manganese Detoxification/Efflux Proteins and Molecular Characterization of ZnT10 Protein as a Manganese Transporter

Manganese homeostasis involves coordinated regulation of specific proteins involved in manganese influx and efflux. However, the proteins that are involved in detoxification/efflux have not been completely resolved nor has the basis by which they select their metal substrate. Here, we compared six proteins, which were reported to be involved in manganese detoxification/efflux, by evaluating their ability to reduce manganese toxicity in chicken DT40 cells, finding that human ZnT10 (hZnT10) was the most significant contributor. A domain swapping and substitution analysis between hZnT10 and the zinc-specific transporter hZnT1 showed that residue Asn43, which corresponds to the His residue constituting the potential intramembranous zinc coordination site in other ZnT transporters, is necessary to impart hZnT10s unique manganese mobilization activity; residues Cys52 and Leu242 in transmembrane domains II and V play a subtler role in controlling the metal specificity of hZnT10. Interestingly, the His → Asn reversion mutant in hZnT1 conferred manganese transport activity and loss of zinc transport activity. These results provide important information about manganese detoxification/efflux mechanisms in vertebrate cells as well as the molecular characterization of hZnT10 as a manganese transporter.

Dopaminergic neuronal dysfunction associated with parkinsonism in both a Gaucher disease patient and a carrier

A clinical association between Gaucher disease and parkinsonism has been demonstrated. We herein report a Japanese patient with type 3 Gaucher disease who was compound heterozygous for F213I and L444P mutations in the glucocerebrosidase gene while his father was heterozygous for the L444P mutation. They both presented with parkinsonism characterized by a predominance of akinetic-rigid signs and a favorable response to anti-Parkinson therapies. We investigated the dopaminergic neuronal function using positron emission tomography (PET) with radioligands, [(11)C] CFT and [(11)C] raclopride. PET studies of both patients demonstrated the [(11)C] CFT uptake to be severely decreased in the putamen and the caudate nucleus, however, the [(11)C] raclopride uptake was normal in the basal ganglia. Although the majority of Gaucher disease patients with parkinsonism tend to be refractory to anti-Parkinson therapies. The clinical features and the findings of the PET studies suggest that patients with parkinsonism associated with the mutation in the glucocerebrosidase gene, even in heterozygosis, may be related to the presynaptic dopaminergic neuronal dysfunction reported in Parkinsons disease. A PET study to evaluate the dopaminergic neuronal function in Gaucher disease would provide both a better understanding of the effects of anti-Parkinson therapies and a help to improve our ability to make an early diagnosis of parkinsonism associated with Gaucher disease.

Case of presymptomatic aceruloplasminemia treated with deferasirox.

Aceruloplasminemia is an autosomal recessive disease characterized by an abnormal iron metabolism. The absence of ferroxidase activity caused by mutation of ceruloplasmin leads to iron overload in the brain, liver and other organs. We report a 35‐year‐old man who was diagnosed with aceruloplasminemia without neurological manifestation despite the accumulation of iron in the brain and liver. To prevent the development of neurodegenerative disorder related to iron toxicity, iron depletion therapy was performed. Iron chelator deferasirox was effective in reducing serum ferritin level and to prevent the progression of the disease.