Masashi Takanashi

Mitochondrial dysfunction associated with increased oxidative stress and α-synuclein accumulation in PARK2 iPSC-derived neurons and postmortem brain tissue

BackgroundParkinson’s disease (PD) is a neurodegenerative disease characterized by selective degeneration of dopaminergic neurons in the substantia nigra (SN). The familial form of PD, PARK2, is caused by mutations in the parkin gene. parkin-knockout mouse models show some abnormalities, but they do not fully recapitulate the pathophysiology of human PARK2.ResultsHere, we generated induced pluripotent stem cells (iPSCs) from two PARK2 patients. PARK2 iPSC-derived neurons showed increased oxidative stress and enhanced activity of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. iPSC-derived neurons, but not fibroblasts or iPSCs, exhibited abnormal mitochondrial morphology and impaired mitochondrial homeostasis. Although PARK2 patients rarely exhibit Lewy body (LB) formation with an accumulation of α-synuclein, α-synuclein accumulation was observed in the postmortem brain of one of the donor patients. This accumulation was also seen in the iPSC-derived neurons in the same patient.ConclusionsThus, pathogenic changes in the brain of a PARK2 patient were recapitulated using iPSC technology. These novel findings reveal mechanistic insights into the onset of PARK2 and identify novel targets for drug screening and potential modified therapies for PD.

Sept4, a Component of Presynaptic Scaffold and Lewy Bodies, Is Required for the Suppression of α-Synuclein Neurotoxicity

In Parkinson disease (PD), alpha-synuclein aggregates called Lewy bodies often involve and sequester Septin4 (Sept4), a polymerizing scaffold protein. However, the pathophysiological significance of this phenomenon is unclear. Here, we show the physiological association of Sept4 with alpha-synuclein, the dopamine transporter, and other presynaptic proteins in dopaminergic neurons; mice lacking Sept4 exhibit diminished dopaminergic neurotransmission due to scarcity of these presynaptic proteins. These data demonstrate an important role for septin scaffolds in the brain. In transgenic mice that express human alpha-synuclein(A53T) (a mutant protein responsible for familial PD), loss of Sept4 significantly enhances neuropathology and locomotor deterioration. In this PD model, insoluble deposits of Ser129-phosphorylated alpha-synuclein(A53T) are negatively correlated with the dosage of Sept4. In vitro, direct association with Sept4 protects alpha-synuclein against self-aggregation and Ser129 phosphorylation. Taken together, these data show that Sept4 may be involved in PD as a dual susceptibility factor, as its insufficiency can diminish dopaminergic neurotransmission and enhance alpha-synuclein neurotoxicity.

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.

Expression of 8-oxoguanine DNA glycosylase (OGG1) in Parkinson’s disease and related neurodegenerative disorders

Oxidative stress including DNA oxidation is implicated in Parkinson’s disease (PD). We postulated that DNA repair enzymes such as 8-oxoguanosine DNA glycosylase (OGG1) are involved in the PD process. We performed immunohistochemical and biochemical studies on brains of patients with PD and those of patients with progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) as disease controls, and control subjects. We found higher expression levels of mitochondrial isoforms of OGG1 enzymes in the substantia nigra (SN) in cases of PD. Furthermore, Western blot analysis revealed high OGG1 levels in the SN of the patients with PD. Our results indicate the importance of oxidative stress within the susceptible lesions in the pathogenesis of PD.

CLINICOPATHOLOGIC STUDY OF A SNCA GENE DUPLICATION PATIENT WITH PARKINSON DISEASE AND DEMENTIA

There is evidence that α-synuclein gene ( SNCA ) point mutations and gene multiplications play a pivotal role in the development of Lewy bodies (LBs) and Lewy neuritic (LN) pathology. Dysregulation of the production/degradation of the α-synuclein protein, a major component of LBs and LNs, is speculated to result in its accumulation and produce the neuropathological features of SNCA -related neurodegeneration.1 The identification of SNCA multiplications in families with parkinsonism suggests that SNCA gene dosage may play a role in the onset of Parkinson disease (PD).2 Most patients with SNCA triplication develop cognitive and autonomic dysfunction in early stage of the disease.3,4 However, three families with SNCA duplication have been reported with symptoms more reminiscent of typical PD.5,6 Interestingly, a recent study reported that one triplication (a Swedish-American pedigree) and one duplication pedigree have a common ancestor.7 As a common mechanism of multiplications, the area including the SNCA-MMRN1 locus could play a role in multiple copy numbers. Another multiplication family has been reported also to have the rearrangement change in the same region indicating the SNCA-MMRN1 locus may be fragile.2,5–7 With regard to clinical aspects, patients with SNCA duplication tend to have milder symptoms compared to those with triplication.5–7 The onset of disease in SNCA duplication patients occurs approximately 15 years later (50 years of age) than that of SNCA triplication families (35 years of age). These features suggest that differences in genetic copy numbers could influence the clinical features of PD. Recently, we identified two families of Japanese origin with SNCA duplications.8 One patient from Family B (named as B-1) developed severe parkinsonism and dementia. These findings indicate that SNCA duplication also causes PD with dementia (PDD). Three copies of the locus SNCA-MMRN1 were identified in the two duplication families. The length of …

A novel L266V mutation of the tau gene causes frontotemporal dementia with a unique tau pathology

We report a novel mutation of tau (L266V missense mutation in exon 9) which may cause a type of familial frontotemporal dementia. The brain of a patient showed Pick body–like inclusions and unique tau‐positive, argyrophilic astrocytes with stout filaments and naked, round, or irregular argyrophilic inclusions with deposits of both three‐repeat and four‐repeat tau. Recombinant tau with a L266V mutation showed a reduced ability to promote microtubule assembly, which may be the primary effect of the mutation. Ann Neurol 2003;53:000–000

Analyses of the MAPT, PGRN, and C9orf72 mutations in Japanese patients with FTLD, PSP, and CBS

BACKGROUND Mutations in the microtubule associated protein tau (MAPT) and progranulin (PGRN) have been identified in several neurodegenerative disorders, such as frontotemporal lobar degeneration (FTLD), progressive supranuclear palsy (PSP), and corticobasal syndrome (CBS). Recently, C9orf72 repeat expansion was reported to cause FTLD and amyotrophic lateral sclerosis (ALS). To date, no comprehensive analyses of mutations in these three genes have been performed in Asian populations. The aim of this study was to investigate the genetic and clinical features of Japanese patients with MAPT, PGRN, or C9orf72 mutations. METHODS MAPT and PGRN were analyzed by direct sequencing and gene dosage assays, and C9orf72 repeat expansion was analyzed by repeat-primed PCR in 75 (48 familial, 27 sporadic) Japanese patients with FTLD, PSP, or CBS. RESULTS We found four MAPT mutations in six families, one novel PGRN deletion/insertion, and no repeat expansion in C9orf72. Intriguingly, we identified a de novo MAPT p.S285R mutation. All six patients with early-onset PSP and the abnormal eye movements that are not typical of sporadic PSP had MAPT mutations. The gene dosages of MAPT and PGRN were normal. DISCUSSION MAPT p.S285R is the first reported de novo mutation in a sporadic adult-onset patient. MAPT mutation analysis is recommended in both familial and sporadic patients, especially in early-onset PSP patients with these abnormal eye movements. Although PGRN and C9orf72 mutations were rare in this study, the PGRN mutation was found in this Asian FTLD. These genes should be studied further to improve the clinicogenetic diagnoses of FTLD, PSP, and CBS.

Motor and non-motor symptoms of 1453 patients with Parkinson's disease: Prevalence and risks

PURPOSE We examined the prevalence and risk of clinical symptoms in a large number of Japanese patients with Parkinsons disease (PD) (n = 1453; 650 males). METHODS Events were analyzed using Kaplan-Meier survival curves, logistic regression, and Cox proportional-hazards models. RESULTS The mean age (SD) was 67.7 (10.0), age of onset was 58.0 (11.5), and disease duration was 9.7 (6.6) years. The mean modified Hoehn and Yahr stage was 2.8 (1.2). Most patients (88.9%) received levodopa (547.7 (257.6) mg/day). A large proportion (81.3%) received dopamine agonists (136.2 (140.7) mg/day). About 23.4% received pain treatment 6.9 (5.1) years after the onset; females (p < 0.05) and patients with late-onset PD (≥60 years, p < 0.001) were more likely to be affected. About 44.7% of patients had wearing-off 7.5 (4.7) years after the onset, and it was more common in females (p < 0.001) and patients with early-onset PD (p < 0.001). Camptocormia was found in 9.5% of patients 8.1 (6.2) years after the onset, and it was more common in females (p < 0.05) and patients with late-onset PD (p < 0.05). About 28.6% of patients developed psychosis 9.0 (5.4) years after the onset, and it was more likely to occur in patients with late-onset PD (p < 0.001). Late-onset PD and cerebrovascular disease were also associated with increased risk of pneumonia. CONCLUSIONS Considering that very few studies have assessed numerous clinical symptoms in the same report, these data provide a useful reference for the clinical course of PD.

Expression patterns of tau mRNA isoforms correlate with susceptible lesions in progressive supranuclear palsy and corticobasal degeneration.

Deposition of hyperphosphorylated tau (p-tau) has been observed in several neurodegenerative diseases. The six isoforms of tau are divided into two main groups including three repeat (3R) and four repeat (4R) microtubule-binding domains. Using quantitative RT-PCR method and immunohistochemistry with phosphorylation dependent anti-tau antibody (AT8), we investigated the expression level of tau mRNA isoforms in the frontal cortex and globus pallidus of patients with progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) to determine whether altered expression patterns of tau mRNA isoforms correlate with p-tau accumulation. The 4R/3R ratios in frontal cortices of CBD and globus pallidus of PSP and CBD were significantly higher than the control (P<0.05). There was no correlation between the expression patterns of tau mRNA isoforms and p-tau accumulation. Our findings suggest that neurodegeneration of PSP and CBD could be regulated by alternative splicing of tau mRNA to yield high 4R/3R ratio. In addition, the lack of correlation between the expression pattern of tau mRNA isoforms and p-tau accumulation suggests that not only alternative splicing of tau mRNA, but also other factors such as post-transcriptional or translational modifications may play a role in the pathogenesis of specific neurodegeneration in PSP and CBD.

Lewy bodies in progressive supranuclear palsy.

Abstract. Lewy bodies (LBs), whose major component is α-synuclein, are a pathological hallmark of Parkinsons disease (PD) but have rarely been reported in progressive supranuclear palsy (PSP). Whether LBs in PSP represent the aging process or the coexistence of PD remains unclear. We found LBs in 5 of 16 patients with PSP. In 4 patients LBs were distributed widely throughout the brain stem and cerebrum in a pattern similar to that in PD. In the remaining patient one LB was found in the pontine reticular formation. Semiquantitative analysis showed that neuronal loss in the locus coeruleus and the dorsal vagal nucleus was more severe in patients with LBs than in patients without LBs. Double-labeling immunohistochemical studies showed co-localization of α-synuclein and tau in some neurons. Our study suggests that patients who have PSP with LBs constitute a subset of patients with PSP in whom Lewy body disease is also present.