Complete nanopore repeat sequencing of SCA27B (GAA-FGF14 ataxia) in Japanese.

BACKGROUND: Although pure GAA expansion is considered pathogenic in SCA27B, non-GAA repeat motif is mostly mixed into longer repeat sequences. This study aimed to unravel the complete sequencing of FGF14 repeat expansion to elucidate its repeat motifs and pathogenicity. METHODS: We screened FGF14 repeat expansion in a Japanese cohort of 460 molecularly undiagnosed adult-onset cerebellar ataxia patients and 1022 controls, together with 92 non-Japanese controls, and performed nanopore sequencing of FGF14 repeat expansion. RESULTS: In the Japanese population, the GCA motif was predominantly observed as the non-GAA motif, whereas the GGA motif was frequently detected in non-Japanese controls. The 5'-common flanking variant was observed in all Japanese GAA repeat alleles within normal length, demonstrating its meiotic stability against repeat expansion. In both patients and controls, pure GAA repeat was up to 400 units in length, whereas non-pathogenic GAA-GCA repeat was larger, up to 900 units, but they evolved from different haplotypes, as rs534066520, located just upstream of the repeat sequence, completely discriminated them. Both (GAA)≥250 and (GAA)≥200 were enriched in patients, whereas (GAA-GCA)≥200 was similarly observed in patients and controls, suggesting the pathogenic threshold of (GAA)≥200 for cerebellar ataxia. We identified 14 patients with SCA27B (3.0%), but their single-nucleotide polymorphism genotype indicated different founder alleles between Japanese and Caucasians. The low prevalence of SCA27B in Japanese may be due to the lower allele frequency of (GAA)≥250 in the Japanese population than in Caucasians (0.15% vs 0.32%-1.26%). CONCLUSIONS: FGF14 repeat expansion has unique features of pathogenicity and allelic origin, as revealed by a single ethnic study.

Clinical Features and Neuroimaging Findings of Neuropil Antibody-Positive Idiopathic Sporadic Ataxia of Unknown Etiology.

Idiopathic sporadic ataxia (ISA) is the clinical term for nonfamilial ataxia with adult-onset and a slowly progressive course. However, immune-mediated cerebellar ataxia cannot be completely excluded from ISA. The current study investigated the neuropil antibodies against cell-surface antigens and clarified the clinical features and neuroimaging findings of patients with these antibodies. Using tissue-based immunofluorescence assays (TBAs), we examined antibodies against the cerebellum in serum samples from 67 patients who met the ISA diagnostic criteria, including 30 patients with multiple system atrophy with predominant cerebellar features (MSA-C) and 20 patients with hereditary ataxia (HA), and 18 healthy control subjects. According to the TBA results, we divided subjects into three groups: subjects positive for neuropil antibodies, subjects positive for intracellular antibodies only, and subjects negative for antibodies. We compared clinical features and neuroimaging findings in ISA patients among these three groups. The prevalence of neuropil antibodies in ISA (17.9%) was significantly higher than that in MSA-C (3.3%), HA (0%), or healthy subjects (0%). The neuropil antibody-positive ISA patients showed pure cerebellar ataxia more frequently than the other ISA patients. Two neuropil antibody-positive patients showed significant improvement of cerebellar ataxia after immunotherapy. We detected neuropil antibodies in 17.9% of ISA patients. Characteristic clinical features of neuropil antibody-positive ISA patients were pure cerebellar ataxia. Some cases of neuropil antibody-positive ISA responded to immunotherapy.

Repeat conformation heterogeneity in cerebellar ataxia, neuropathy, vestibular areflexia syndrome.

Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is a late-onset, slow-progressing multisystem neurodegenerative disorder. Biallelic AAGGG repeat expansion in RFC1 has been identified as causative of this disease, and repeat conformation heterogeneity (ACAGG repeat) was also recently implied. To molecularly characterize this disease in Japanese patients with adult-onset ataxia, we accumulated and screened 212 candidate families by an integrated approach consisting of flanking PCR, repeat-primed PCR, Southern blotting and long-read sequencing using Sequel II, GridION or PromethION. We identified 16 patients from 11 families, of whom seven had ACAGG expansions [(ACAGG)exp/(ACAGG)exp] (ACAGG homozygotes), two had ACAGG and AAGGG expansions [(ACAGG)exp/(AAGGG)exp] (ACAGG/AAGGG compound heterozygotes) and seven had AAGGG expansions [(AAGGG)exp/(AAGGG)exp] (AAGGG homozygotes). The overall detection rate was 5.2% (11/212 families including one family having two expansion genotypes). Long-read sequencers revealed the entire sequence of both AAGGG and ACAGG repeat expansions at the nucleotide level of resolution. Clinical assessment and neuropathology results suggested that patients with ACAGG expansions have similar clinical features to previously reported patients with homozygous AAGGG expansions, although motor neuron involvement was more notable in patients with ACAGG expansions (even if one allele was involved). Furthermore, a later age of onset and slower clinical progression were implied in patients with ACAGG/AAGGG compound heterozygous expansions compared with either ACAGG or AAGGG homozygotes in our very limited cohort. Our study clearly shows the occurrence of repeat conformation heterogeneity, with possible different impacts on the affected nervous systems. The difference in disease onset and progression between compound heterozygotes and homozygotes might also be suspected but with very limited certainty due to the small sample number of cases in our study. Studies of additional patients are needed to confirm this.

Gait training with a wearable powered robot during stroke rehabilitation: a randomized parallel-group trial.

BACKGROUND: We have developed a wearable rehabilitation robot, "curara®," and examined its immediate effect in patients with spinocerebellar degeneration and stroke, but its rehabilitative effect has not been clarified. The purpose of this study was to examine the effect of this device on gait training in stroke patients. METHODS: Forty stroke patients were enrolled in this study. The participants were divided randomly into two groups (groups A and B). The participants assigned to group A received RAGT with curara® type 4, whereas those in group B received conventional therapist-assisted gait training. The clinical trial period was 15 days. The participants performed 10 sessions of gait training (5 times per week) each lasting 30 ± 5 min per day. The 10-m walking time (10mWT), and 6-minute walking distance (6MWD) were evaluated as the main outcomes. Timed up and go and Berg Balance Scale (BBS) were also examined. Gait parameters (stride duration and length, standard deviation of stride duration and length, cadence, ratio of the stance/swing phases, minimum/maximum knee joint angle, and minimum/maximum hip joint angle) were measured using a RehaGait®. The items other than BBS were measured on days 0, 7, and 14, whereas BBS was measured on days 0 and 14. The improvement rate was calculated as the difference of values between days 14 and 0 divided by the value on day 0. The improvement rates of the 10mWT and 6MWD were set as the main outcomes. RESULTS: The data of 35 participants were analyzed. There was no significant difference in the main outcomes between both groups at the end of gait training. As for intragroup changes, gait speed, stride length, stride duration, and cadence were improved significantly between days 0 and 14 in each group. When examining the interaction effect between the day of measurement and group, stride duration (p = 0.006) and cadence (p = 0.012) were more significantly improved in group A than in group B. CONCLUSIONS: This novel wearable powered robot may have the potential to improve gait speed of individuals in stroke rehabilitation. TRIAL REGISTRATION: Japan Registry of Clinical Trials (jRCTs032180163). Registered on February 22, 2019; https://jrct.niph.go.jp/en-latest-detail/jRCTs032180163 . UMIN CLINICAL TRIALS REGISTRY (UMIN000034237): Registered on September 22, 2018; https://center6.umin.ac.jp/cgi-open-bin/icdr/ctr_view.cgi?recptno=R000038939 .

Stress-Inducible SCAND Factors Suppress the Stress Response and Are Biomarkers for Enhanced Prognosis in Cancers.

The cell stress response is an essential system present in every cell for responding and adapting to environmental stimulations. A major program for stress response is the heat shock factor (HSF)-heat shock protein (HSP) system that maintains proteostasis in cells and promotes cancer progression. However, less is known about how the cell stress response is regulated by alternative transcription factors. Here, we show that the SCAN domain (SCAND)-containing transcription factors (SCAN-TFs) are involved in repressing the stress response in cancer. SCAND1 and SCAND2 are SCAND-only proteins that can hetero-oligomerize with SCAN-zinc finger transcription factors, such as MZF1(ZSCAN6), for accessing DNA and transcriptionally co-repressing target genes. We found that heat stress induced the expression of SCAND1, SCAND2, and MZF1 bound to HSP90 gene promoter regions in prostate cancer cells. Moreover, heat stress switched the transcript variants' expression from long noncoding RNA (lncRNA-SCAND2P) to protein-coding mRNA of SCAND2, potentially by regulating alternative splicing. High expression of HSP90AA1 correlated with poorer prognoses in several cancer types, although SCAND1 and MZF1 blocked the heat shock responsiveness of HSP90AA1 in prostate cancer cells. Consistent with this, gene expression of SCAND2, SCAND1, and MZF1 was negatively correlated with HSP90 gene expression in prostate adenocarcinoma. By searching databases of patient-derived tumor samples, we found that MZF1 and SCAND2 RNA were more highly expressed in normal tissues than in tumor tissues in several cancer types. Of note, high RNA expression of SCAND2, SCAND1, and MZF1 correlated with enhanced prognoses of pancreatic cancer and head and neck cancers. Additionally, high expression of SCAND2 RNA was correlated with better prognoses of lung adenocarcinoma and sarcoma. These data suggest that the stress-inducible SCAN-TFs can function as a feedback system, suppressing excessive stress response and inhibiting cancers.

Reproduction of the Antitumor Effect of Cisplatin and Cetuximab Using a Three-dimensional Spheroid Model in Oral Cancer.

Background/Aim: Cancer research has been conducted using cultured cells as part of drug discovery testing, but conventional two-dimensional culture methods are unable to reflect the complex tumor microenvironment. On the other hand, three-dimensional cultures have recently been attracting attention as in vitro models that more closely resemble the in vivo physiological environment. The purpose of this study was to establish a 3D culture method for oral cancer and to verify its practicality. Materials and Methods: Three-dimensional cultures were performed using several oral cancer cell lines. Western blotting was used for protein expression analysis of the collected cell masses (spheroids), and H-E staining was used for structural observation. The cultures were exposed to cisplatin and cetuximab and the morphological changes of spheroids over time and the expression changes of target proteins were compared. Results: Each cell line formed spheroidal cell aggregates and showed enhancement of cell adhesion molecules over time. H-E staining showed tumor tissue-like structures specific to each cell line. Cisplatin showed concentration-dependent antitumor effects due to loss of cell adhesion and spheroid disruption in each cell line, while cetuximab exhibited antitumor effects that correlated with EGFR expression in each cell line. Conclusion: Spheroids made from oral cancer cell lines appeared to have tumor-like characteristics that may reflect their clinical significance. In the future, it may become possible to produce tumor spheroids from tissue samples of oral cancer patients, and then apply them to drug screening and to develop individualized diagnostic and treatment methods.

MTCL1 plays an essential role in maintaining Purkinje neuron axon initial segment.

The axon initial segment (AIS) is a specialized domain essential for neuronal function, the formation of which begins with localization of an ankyrin-G (AnkG) scaffold. However, the mechanism directing and maintaining AnkG localization is largely unknown. In this study, we demonstrate that in vivo knockdown of microtubule cross-linking factor 1 (MTCL1) in cerebellar Purkinje cells causes loss of axonal polarity coupled with AnkG mislocalization. MTCL1 lacking MT-stabilizing activity failed to restore these defects, and stable MT bundles spanning the AIS were disorganized in knockdown cells. Interestingly, during early postnatal development, colocalization of MTCL1 with these stable MT bundles was observed prominently in the axon hillock and proximal axon. These results indicate that MTCL1-mediated formation of stable MT bundles is crucial for maintenance of AnkG localization. We also demonstrate that Mtcl1 gene disruption results in abnormal motor coordination with Purkinje cell degeneration, and provide evidence suggesting possible involvement of MTCL1 dysfunction in the pathogenesis of spinocerebellar ataxia.

Gait training with a wearable curara® robot for cerebellar ataxia: a single-arm study.

BACKGROUND: Ataxic gait is one of the most common and disabling symptoms in people with degenerative cerebellar ataxia. Intensive and well-coordinated inpatient rehabilitation improves ataxic gait. In addition to therapist-assisted gait training, robot-assisted gait training has been used for several neurological disorders; however, only a small number of trials have been conducted for degenerative cerebellar ataxia. We aimed to validate the rehabilitative effects of a wearable "curara®" robot developed in a single-arm study of people with degenerative cerebellar ataxia. METHODS: Twenty participants with spinocerebellar ataxia or multiple system atrophy with predominant cerebellar ataxia were enrolled. The clinical trial duration was 15 days. We used a curara® type 4 wearable robot for gait training. We measured the following items at days 0, 7, and 14: Scale for the Assessment and Rating of Ataxia, 10-m walking time (10 mWT), 6-min walking distance (6 mWD), and timed up and go test. Gait parameters (i.e., stride duration and length, standard deviation of stride duration and length, cadence, ratio of the stance and swing phases, minimum and maximum knee joint angles, and minimum and maximum hip joint angles) were obtained using a RehaGait®. On days 1-6 and 8-13, the participants were instructed to conduct gait training for 30 ± 5 min with curara®. We calculated the improvement rate as the difference of values between days 14 and 0 divided by the value on day 0. Differences in the gait parameters were analyzed using a generalized linear mixed model with Bonferroni's correction. RESULTS: Data from 18 participants were analyzed. The mean improvement rate of the 10 mWT and 6 mWD was 19.0% and 29.0%, respectively. All gait parameters, except the standard deviation of stride duration and length, improved on day 14. CONCLUSIONS: Two-week RAGT with curara® has rehabilitative effects on gait function comparable to those of therapist-assisted training. Although the long-term effects after a month of RAGT with curara® are unclear, curara® is an effective tool for gait training of people with degenerative ataxia. Trial registration jRCT, jRCTs032180164. Registered: 27 February 2019; retrospectively registered. https://jrct.niph.go.jp/en-latest-detail/jRCTs032180164 .

Taste disorder in facial onset sensory and motor neuronopathy: a case report.

BACKGROUND: Taste disorder is a common symptom in the general population. Several studies have shown that patients with neurological disorders, such as amyotrophic lateral sclerosis and Parkinson's disease, develop taste disturbance. Facial onset sensory and motor neuronopathy (FOSMN) is a rare disease characterized by sensory disturbance and weakness spreading from the face to the limbs caudally. We describe a patient with FOSMN who showed taste disorder as the sole initial symptom. CASE PRESENTATION: A 49-year-old man who smoked cigarettes developed taste disturbance. Despite using zinc supplements, an herbal medication, and an ointment, his taste disorder worsened. 4 years later, a tingling feeling emerged at the tip of his tongue and gradually spread to his entire lips. At 55 years of age, he showed difficulty in swallowing, followed by facial paresthesia, muscle atrophy, and weakness in the face and upper limbs without apparent upper motor neuron sign. Cessation of smoking did not improve his taste disturbance, and he was unable to discriminate different tastes on the entire tongue. In an electrogustometric study, electrical stimulation did not induce any type of taste sensation. Blink reflex showed delayed or diminished R2 responses. Needle electromyography revealed severe chronic neurogenic changes in the tongue and masseter muscles. Mild chronic neurogenic changes were also observed in the limbs. In the thoracic paraspinal muscles, active neurogenic changes were detected. Findings of hematological and cerebrospinal fluid analyses, and magnetic resonance images of the brain and spinal cord were unremarkable. One cycle of intravenous immunoglobulin therapy did not improve his symptoms. We diagnosed him as having FOSMN with the sole initial symptom of taste disorder. Nine years after the onset of taste disorder, he developed impaired sensation of touch in the right upper limb and required tube feeding and ventilator support. CONCLUSION: Taste disorder can be the initial manifestation of FOSMN and might involve the solitary nucleus.

Long-Term Suppression of Disabling Tremor by Thalamic Stimulation in a Patient with Spinocerebellar Ataxia Type 2.

The beneficial effect of thalamic deep brain stimulation (DBS) on action tremor has been reported in a few cases of spinocerebellar ataxia (SCA); however, several factors should be taken into account regarding the indication for DBS in advanced cases. We performed DBS of the ventral intermediate nucleus (Vim) of the thalamus for treatment of coarse action tremor in a patient with SCA2 (spinocerebellar ataxia type 2) in the wheelchair-bound stage. Although improvement of the tremor of the proximal part was incomplete, the patient regained substantial parts of daily functioning. The effect lasted for more than 6 years, and the suppression of tremor significantly contributed to maintaining the level of the patient's expression into the bedridden stage. Vim DBS can be a treatment option for tremor in SCA patients, even in the advanced stage, as long as the tremor is depriving the patient of behavioral expression. As residual proximal tremor may hamper functional recovery, DBS of other targets or multi-targets should be further explored to attain a better outcome.

A Japanese Family of Spinocerebellar Ataxia Type 21: Clinical and Neuropathological Studies.

Spinocerebellar ataxia type 21 (SCA21) is a rare subtype of autosomal dominant cerebellar ataxias, which was first identified in a French family and has been reported almost exclusively in French ancestry so far. We here report the first Japanese family with SCA21, in which all affected members examined carried a heterozygous c.509C > T:p.Pro170Leu variant in TMEM240. Their clinical features were summarized as a slowly progressive ataxia of young-adult onset (5-48 years) associated with various degree of psychomotor retardation or cognitive impairment. The MR images revealed atrophy in the cerebellum, but not in the cerebrum or brainstem. These clinical findings were consistent with those in the original French families with SCA21. Neuropathological findings in one autopsied patient showed a prominent decrease of cerebellar Purkinje cells, but no specific abnormalities outside the cerebellum.

Effects of gait support in patients with spinocerebellar degeneration by a wearable robot based on synchronization control.

BACKGROUND: Spinocerebellar degeneration (SCD) mainly manifests a cerebellar ataxic gait, leading to marked postural sway and the risk of falling down. Gait support using a wearable robot is expected to be an effective solution to maintaining the status quo and/or delaying symptom progression. The aim of this study was to evaluate the effects of gait support in patients with SCD by using a wearable robotic system called curara ®; while undergoing walking tests. METHODS: The curara system assists both the hip and knee joints and supports the wearer's rhythmic gait using a synchronization control based on a central pattern generator. The system reflects the wearer's intended motion in response to the gait support by detecting an interactive force that is generated from slight movements of the wearer. The degree of coordinated motion between the robot and the wearer can be adjusted by modifying the synchronization gain. In this study, we provided gait support using three high-gain conditions (A, B, C) to more easily follow the wearer's movement in each joint. The synchronization gains for both the hip and knee joints (i.e., Ch and Ck) were set at 0.5 for condition A and at 0.4 for condition B. Condition C had different gains for the hip and knee joints (i.e., Ch=0.4 and Ck=0.5). With the walking test, we assessed the effects of the gait support provided by the curara system on walking smoothness (measured using the harmonic ratio: HR) and spatiotemporal parameters (gait speed, stride length, cadence) in SCD patients (n=12). We compared the performance between the three high-gain conditions and without assistance from the robot. RESULTS: Under condition C, the HRs in the anteroposterior, mediolateral, and vertical directions (HR-AP, HR-ML, and HR-V) were especially high compared with those under conditions A and B. The results of the statistical analyses using repeated measures analysis of variance followed by Tukey's test showed that gait support with condition C results in a statistically significant increase in the HR-AP (2.04 ±0.52; p=0.025) and HR-V (2.06 ±0.37; p=0.032) when compared with walking without assistance from the system. In contrast, the gait speed, stride length, and cadence under condition C were no major changes in most patients, compared with the patient's walking without assistance. CONCLUSIONS: The significantly increased HR indicates that gait support under condition C achieved smoother walking than when not wearing the power unit of the system. Consequently, we suggest that gait support using the curara system has the potential to improve walking smoothness in patients with SCD.

Inter-generational instability of inserted repeats during transmission in spinocerebellar ataxia type 31.

The causative mutation for spinocerebellar ataxia type 31 (SCA31) is an intronic insertion containing pathogenic pentanucleotide repeats, (TGGAA)n. We examined to what degree the inserted repeats were unstable during transmission. In 14 parent-child pairs, the average change of onset age was -6.4±7.3 years (mean±s.d.) in the child generation when compared with the parent generation. Of the 11 pairs analyzed, six showed expansion of inserted repeat length during transmission, and five showed contraction. On average, the inserted repeats expanded by 12.2±32.7 bp during transmission, but their mean length (with a 95% confidence interval) was not significantly different between parent and child generations. We consider that the length of the inserted repeats in SCA31 is changeable during transmission, but inter-generational instability is not marked, as far as the current sizing method can determine.

Natural History of Spinocerebellar Ataxia Type 31: a 4-Year Prospective Study.

Spinocerebellar ataxia type 31 (SCA31) is known as a late-onset, relatively pure cerebellar form of ataxia, but a longitudinal prospective study on the natural history of SCA31 has not been done yet. In this prospective cohort study, we enrolled 44 patients (mean ± standard deviation 73.6 ± 8.5 years) with genetically confirmed SCA31 from 10 ataxia referral centers in the Nagano area, Japan. Patients were evaluated every year for 4 years using the Scale for the Assessment and Rating of Ataxia (SARA) and the Barthel Index (BI). Of the 176 follow-up visits (91.5%), 161 were completed in this study. Five patients (11.4%) died during the follow-up period, and two patients (4.5%) were lost to follow-up. The annual progression of the SARA score was 0.8 ± 0.1 points/year and that of the BI was -2.3 ± 0.4 points/year (mean ± standard error). Shorter disease duration at baseline was associated with faster progression of the SARA score. Our study indicated the averaged clinical course of SCA31 as follows: the patients develop ataxic symptoms at 58.5 ± 10.3 years, become wheelchair bound at 79.4 ± 1.7 years, and died at 88.5 ± 0.7 years. Our prospective dataset provides important information for clinical trials of forthcoming disease-modifying therapies for cerebellar ataxia. It also represents a useful resource for SCA31 patients and their family members in genetic counseling sessions.

Principal component analysis for ataxic gait using a triaxial accelerometer.

BACKGROUND: It is quite difficult to evaluate ataxic gait quantitatively in clinical practice. The aim of this study was to analyze the characteristics of ataxic gait using a triaxial accelerometer and to develop a novel biomarker of integrated gate parameters for ataxic gait. METHODS: Sixty-one patients with spinocerebellar ataxia (SCA) or multiple system atrophy with predominant cerebellar ataxia (MSA-C) and 57 healthy control subjects were enrolled. The subjects were instructed to walk 10 m for a total of 12 times on a flat floor at their usual walking speed with a triaxial accelerometer attached to their back. Gait velocity, cadence, step length, step regularity, step symmetry, and degree of body sway were evaluated. Principal component analysis (PCA) was used to analyze the multivariate gait parameters. The Scale for the Assessment and Rating of Ataxia (SARA) was evaluated on the same day of the 10-m walk trial. RESULTS: PCA divided the gait parameters into four principal components in the controls and into two principal components in the patients. The four principal components in the controls were similar to those found in earlier studies. The second principal component in the patients had relevant factor loading values for gait velocity, step length, regularity, and symmetry in addition to the degree of body sway in the medio-lateral direction. The second principal component score (PCS) in the patients was significantly correlated with disease duration and the SARA score of gait (ρ = -0.363, p = 0.004; ρ = -0.574, p < 0.001, respectively). CONCLUSIONS: PCA revealed the main component of ataxic gait. The PCS of the main component was significantly different between the patients and controls, and it was well correlated with disease duration and the SARA score of gait in the patients. We propose that this score provides a novel method to assess the severity of ataxic gait quantitatively using a triaxial accelerometer.

Elevation of serum heat-shock protein levels in amyotrophic lateral sclerosis.

Heat-shock proteins (HSPs) have been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). In this study, we aimed to examine whether the serum levels of HSPs (HSP27, HSP70, and HSP90) are altered in patients with ALS. We included 58 patients diagnosed with ALS and 85 control individuals. Serum HSP levels of patients and controls were determined using enzyme-linked immunosorbent assay. The serum levels of HSP70 and HSP90 were significantly higher in patients than in controls. In contrast, serum levels of HSP27 did not differ significantly between the patient and control groups. Moreover, serum levels of HSP70 and HSP90 in patients remained high throughout the duration of the disease. Taken together, our findings suggest that HSPs might have a role in ALS progression throughout the course of the disease. Further studies are needed to clarify the role of HSPs in the pathogenesis of ALS.

[Iron accumulation and neurodegenerative diseases].

Iron, as well as copper, is essential for a wide variety of biological processes in living organisms, however, dysregulation of iron homeostasis may lead to oxidative stress via redox cycling reactions. Therefore, cellular and systemic iron homeostasis is tightly regulated by a number of iron metabolism proteins. The brain is susceptible to iron-mediated oxidative damage because of a relatively high content of iron and high consumption of oxygen. Iron-mediated neurotoxicity is symbolically seen in neurodegeneration with brain iron accumulation (NBIA) in which iron accumulates mainly in the basal ganglia. Furthermore, iron accumulation is considered to play important roles in the pathophysiology of other, more prevalent neurodegenerative diseases such as Parkinson's disease (PD). Here, from the standpoint of iron dyshomeostasis, current understandings and therapeutic approaches in NBIA and PD are briefly discussed.

Variable expression of microglial DAP12 and TREM2 genes in Nasu-Hakola disease.

Nasu-Hakola disease (NHD) is a form of presenile dementia associated with sclerosing leukoencephalopathy and polycystic lipomembranous osteodysplasia. This extremely rare inherited disease is caused by mutations in either DAP12 or TREM2. The present study was designed to assess the relationship between DAP12/TREM2 genotype, mRNA and protein expression levels by both Western blotting and immunohistochemistry, and the tissue distribution and pathomorphological phenotype of the microglia. Molecular genetic testing performed in three NHD cases confirmed that two cases had mutations in DAP12 and that one case carried a mutation in TREM2. Protein levels were analyzed in four cases. Interestingly, significant DAP12 expression was found in numerous microglia in one NHD case with a homozygous DAP12 single-base substitution, and both real-time PCR and Western blotting confirmed the finding. In contrast, levels of both DAP12 and TREM2, respectively, were much lower in the other cases. Immunohistochemistry using established microglial markers revealed consistently mild activation of microglia in the cerebral white matter although there was no or only little expression of DAP12 in three of the NHD cases. The highly different expression of DAP12 represents the first description of such variable expressivity in NHD microglia. It raises important questions regarding the mechanisms underlying dementia and white matter damage in NHD.

Exome sequencing reveals a homozygous SYT14 mutation in adult-onset, autosomal-recessive spinocerebellar ataxia with psychomotor retardation.

Autosomal-recessive cerebellar ataxias (ARCAs) are clinically and genetically heterogeneous disorders associated with diverse neurological and nonneurological features that occur before the age of 20. Currently, mutations in more than 20 genes have been identified, but approximately half of the ARCA patients remain genetically unresolved. In this report, we describe a Japanese family in which two siblings have slow progression of a type of ARCA with psychomotor retardation. Using whole-exome sequencing combined with homozygosity mapping, we identified a homozygous missense mutation in SYT14, encoding synaptotagmin XIV (SYT14). Expression analysis of the mRNA of SYT14 by a TaqMan assay confirmed that SYT14 mRNA was highly expressed in human fetal and adult brain tissue as well as in the mouse brain (especially in the cerebellum). In an in vitro overexpression system, the mutant SYT14 showed intracellular localization different from that of the wild-type. An immunohistochemical analysis clearly showed that SYT14 is specifically localized to Purkinje cells of the cerebellum in humans and mice. Synaptotagmins are associated with exocytosis of secretory vesicles (including synaptic vesicles), indicating that the alteration of the membrane-trafficking machinery by the SYT14 mutation may represent a distinct pathomechanism associated with human neurodegenerative disorders.

Autosomal-recessive complicated spastic paraplegia with a novel lysosomal trafficking regulator gene mutation.

BACKGROUND: Autosomal-recessive hereditary spastic paraplegias (AR-HSP) consist of a genetically diverse group of neurodegenerative diseases characterised by pyramidal tracts dysfunction. The causative genes for many types of AR-HSP remain elusive. We tried to identify the gene mutation for AR-HSP with cerebellar ataxia and neuropathy. METHODS: This study included two patients in a Japanese family with their parents who are first cousins. Neurological examination and gene analysis were conducted in the two patients and two normal family members. We undertook genome-wide linkage analysis employing single nucleotide polymorphism arrays using the two patients' DNAs and exome sequencing using one patient's sample. RESULTS: We detected a homozygous missense mutation (c.4189T>G, p.F1397V) in the lysosomal trafficking regulator (LYST) gene, which is described as the causative gene for Chédiak-Higashi syndrome (CHS). CHS is a rare autosomal-recessive syndrome characterised by hypopigmentation, severe immune deficiency, a bleeding tendency and progressive neurological dysfunction. This mutation was co-segregated with the disease in the family and was located at well-conserved amino acid. This LYST mutation was not found in 200 Japanese control DNAs. Microscopic observation of peripheral blood in the two patients disclosed large peroxidase-positive granules in both patients' granulocytes, although they had no symptoms of immune deficiency or bleeding tendency. CONCLUSIONS: We diagnosed these patients as having adult CHS presenting spastic paraplegia with cerebellar ataxia and neuropathy. The clinical spectrum of CHS is broader than previously recognised. Adult CHS must be considered in the differential diagnosis of AR-HSP.