Takao Kiriyama

DNA single-strand break repair is impaired in aprataxin-related ataxia

Early‐onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH)/ataxia with oculomotor apraxia type 1 (AOA1) is an autosomal recessive form of cerebellar ataxia. The causative protein for EAOH/AOA1, aprataxin (APTX), interacts with X‐ray repair cross‐complementing 1 (XRCC1), a scaffold DNA repair protein for single‐strand breaks (SSBs). The goal of this study was to prove the functional involvement of APTX in SSB repair (SSBR).

Characteristic Neuroimaging in Patients with Tumefactive Demyelinating Lesions Exceeding 30 mm

Features of tumefactive demyelinating lesion (TDL) on magnetic resonance imaging (MRI) can facilitate the differential diagnosis of TDL and neoplastic lesions, but vary considerably among patients. The larger TDL grows, the more difficult it becomes to differentiate TDL from neoplastic lesions. The purpose of this study was to elucidate typical MRI features in 12 patients with large TDL (>30 mm in diameter).

Restoration of nuclear-import failure caused by triple A syndrome and oxidative stress.

Triple A syndrome is an autosomal recessive neurological disease, mimicking motor neuron disease, and is caused by mutant ALADIN, a nuclear-pore complex component. We recently discovered that the pathogenesis involved impaired nuclear import of DNA repair proteins, including DNA ligase I and the cerebellar ataxia causative protein aprataxin. Such impairment was overcome by fusing classical nuclear localization signal (NLS) and 137-aa downstream sequence of XRCC1, designated stretched NLS (stNLS). We report here that the minimum essential sequence of stNLS (mstNLS) is residues 239-276, downsized by more than 100 aa. mstNLS enabled efficient nuclear import of DNA repair proteins in patient fibroblasts, functioned under oxidative stress, and reduced oxidative-stress-induced cell death, more effectively than stNLS. The stress-tolerability of mstNLS was also exerted in control fibroblasts and neuroblastoma cells. These findings may help develop treatments for currently intractable triple A syndrome and other oxidative-stress-related neurological diseases, and contribute to nuclear compartmentalization study.

Protein kinase Cγ, a protein causative for dominant ataxia, negatively regulates nuclear import of recessive-ataxia-related aprataxin

Spinocerebellar ataxia type 14 (SCA14) is an autosomal dominant disease caused by mutations in the gene encoding protein kinase C gamma (PKC gamma). We report an SCA14 family with a novel deletion of a termination-codon-containing region, resulting in a missense change and a C-terminal 13-amino-acid extension with increased kinase activity. Notably, one patient with a severe phenotype is the first homozygote for the mutation causing SCA14. We show the novel molecular consequences of increased kinase activities of mutants: aprataxin (APTX), a DNA repair protein causative for autosomal recessive ataxia, was found to be a preferential substrate of mutant PKC gamma, and phosphorylation inhibited its nuclear entry. The phosphorylated residue was Thr111, located adjacent to the nuclear localization signal, and disturbed interactions with importin alpha, a nuclear import adaptor. Decreased nuclear APTX increased oxidative stress-induced DNA damage and cell death. Phosphorylation-resistant APTX, kinase inhibitors, and antioxidants may be therapeutic options for SCA14.

Renin-angiotensin system blockers affect cognitive decline and serum adipocytokines in Alzheimer's disease.

Accumulating evidence indicates an association of Alzheimers disease (AD) with the metabolic syndrome (MetS), characterized by visceral fat accumulation with insulin resistance and altered secretion of adipocytokines such as adiponectin and leptin. The renin‐angiotensin system (RAS) regulates blood pressure and insulin resistance. Recent studies suggest that the RAS plays crucial roles in cognitive functions and that adipocytokines exert neuroprotective activity in the brain. We investigated whether RAS blockers (RASB) affect adipocytokines and cognitive function in patients with AD.

Risk of Falling in Parkinson’s Disease at the Hoehn-Yahr Stage III

Background: It is difficult to predict the risk of falling, especially in patients with good motor ability, and the mechanisms underlying the relation between gait patterns and falling in Parkinson’s disease (PD) remain unclear. We investigated factors related to falling, including walking speed and time, in patients with Hoehn-Yahr stage III PD. Methods: We performed clinical assessments and evaluated balance in 30 patients with PD. Information on falling was obtained from questionnaires and personal interviews. Gait patterns were analyzed with the use of an originally designed, suddenly narrowed path. Results: Gait velocity was slower in fallers than in non-fallers (p = 0.047). Unified Parkinson’s Disease Rating Scale part II (UPDRS part II) score, fear of falling, and gait velocity were significantly related to falling on analysis with a single logistic model. When a multiple logistic model was used, the UPDRS part II score was significantly related to falling (OR: 1.48, p = 0.037, 95% CI: 1.02–2.16). Conclusions: Patients with Hoehn-Yahr stage III PD showed slow gait velocity attributed to fear of falling before arrival at a narrowed entrance or while walking on a narrowed path. The UPDRS part II score is significantly related to the risk of future falls.

Short half-lives of ataxia-associated aprataxin proteins in neuronal cells

Early-onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH)/ataxia with oculomotor apraxia type 1 (AOA1) is caused by mutations in the gene encoding aprataxin (APTX). Although several in vitro findings proposed that impaired enzymatic activities of APTX are responsible for EAOH/AOA1, potential instability of mutant proteins has also been suggested as the pathogenesis based on in vivo finding that mutant proteins are almost undetectable in EAOH/AOA1 tissues or cells. The present study aimed to experimentally prove instability of mutant proteins in neuronal cells, the cell type preferentially affected by this disease. Results of pulse-chase experiments demonstrated that all of the disease-associated mutants had extremely shorter half-lives than the WT. We further found that mutants were targeted for rapid proteasome-mediated degradation. These results help establish pathogenic and physiological protein characteristics of APTX in neuronal cells.

Myasthenia gravis can cause camptocormia

Camptocormia is characterised by an abnormal posture of the trunk with marked flexion of the thoracolumbar spine. The spinal curvature resolves when the affected individual lies in the supine position. Camptocormia can be associated with metabolic, spinal, neuromuscular, psychiatric, neurogenic and movement disorders.1 We describe an unusual patient with myasthenia gravis (MG) who had camptocormia that responded to edrophonium. In February 2009, a 75-year-old woman with a history of hypertension and angina noticed lower extremity weakness, numbness below the trunk and forward flexion of the lumbar spine. In April, she underwent surgery to treat ossified thoracic yellow ligaments, and the numbness resolved. However, weakness and forward flexion of the lumbar spine gradually worsened, and in August she required a cane to walk. In October, she presented with dropped head. The severity of forward …

Can Postural Instability Respond to Galvanic Vestibular Stimulation in Patients with Parkinson’s Disease?

Objective Galvanic vestibular stimulation (GVS) activates the vestibular afferents, and these changes in vestibular input exert a strong influence on the subject’s posture or standing balance. In patients with Parkinson’s disease (PD), vestibular dysfunction might contribute to postural instability and gait disorders. Methods Current intensity was increased to 0.7 mA, and the current was applied to the patients for 20 minutes. To perform a sham stimulation, the current intensity was increased as described and then decreased to 0 mA over the course of 10 seconds. The patient’s status was recorded continuously for 20 minutes with the patient in the supine position. Results Three out of 5 patients diagnosed with PD with postural instability and/or abnormal axial posture showed a reduction in postural instability after GVS. The score for item 12 of the revised Unified Parkinson’s Disease Rating Scale part 3 was decreased in these patients. Conclusions The mechanism of postural instability is complex and not completely understood. In 2 out of the 5 patients, postural instability was not changed in response to GVS. Nonetheless, the GVS-induced change in postural instability for 3 patients in our study suggests that GVS might be a therapeutic option for postural instability.

Naturally- and experimentally-designed restorations of the Parkin gene deficit in autosomal recessive juvenile parkinsonism.

Intranuclear events due to mutations in the Parkin gene remain elusive in autosomal recessive juvenile parkinsonism (ARJP). We identified a mutant PARKIN protein in fibroblast cultures from a pair of siblings with ARJP who were homozygous for the exon 4-deleted Parkin gene. Disease was mild in one patient and debilitating in the other. The detected mutant, encoded by a transcript lacking exon 3 as well as exon 4, is an in-frame deletion that removes 121 aa, resulting in a 344-aa protein (PaDel3,4). Cell culture and transfection studies revealed negative correlations between expression levels of PaDel3,4 and those of cell cycle proteins, including cyclin E, CDK2, ppRb, and E2F-1, and demonstrated that GFP-PaDel3,4 entered nucleus and ubiquitinated cyclin E as a part of SCF(hSel-10) ligase complex in the patient cells. In addition, nuclear localization signal-tagged PaDel3,4 expressed in the transfected patient cells most effectively ubiquitinated cyclin E and reduced DNA damage, protecting cells from oxidative stress. Antisense-oligonucleotide treatment promoted skipping of exon 3 and thus generated PaDel3,4, increasing cell survival. Collectively, we propose that naturally- and experimentally-induced exon skipping at least partly restores the mutant Parkin gene deficit, providing a molecular basis for the development of therapeutic exon skipping.