Hidehiro Mizusawa

Spinocerebellar ataxia type 31 is associated with "inserted" penta-nucleotide repeats containing (TGGAA)n.

Spinocerebellar ataxia type 31 (SCA31) is an adult-onset autosomal-dominant neurodegenerative disorder showing progressive cerebellar ataxia mainly affecting Purkinje cells. The SCA31 critical region was tracked down to a 900 kb interval in chromosome 16q22.1, where the disease shows a strong founder effect. By performing comprehensive Southern blot analysis and BAC- and fosmid-based sequencing, we isolated two genetic changes segregating with SCA31. One was a single-nucleotide change in an intron of the thymidine kinase 2 gene (TK2). However, this did not appear to affect splicing or expression patterns. The other was an insertion, from 2.5-3.8 kb long, consisting of complex penta-nucleotide repeats including a long (TGGAA)n stretch. In controls, shorter (1.5-2.0 kb) insertions lacking (TGGAA)n were found only rarely. The SCA31 repeat insertions length inversely correlated with patient age of onset, and an expansion was documented in a single family showing anticipation. The repeat insertion was located in introns of TK2 and BEAN (brain expressed, associated with Nedd4) expressed in the brain and formed RNA foci in the nuclei of patients Purkinje cells. An electrophoretic mobility-shift assay showed that essential splicing factors, serine/arginine-rich splicing factors SFRS1 and SFRS9, bind to (UGGAA)n in vitro. Because (TGGAA)n is a characteristic sequence of paracentromeric heterochromatin, we speculate that the insertion might have originated from heterochromatin. SCA31 is important because it exemplifies human diseases associated with inserted microsatellite repeats that can expand through transmission. Our finding suggests that the ectopic microsatellite repeat, when transcribed, might cause a disease involving the essential splicing factors.

Depletion of Vitamin E Increases Amyloid β Accumulation by Decreasing Its Clearances from Brain and Blood in a Mouse Model of Alzheimer Disease

Increased oxidative damage is a prominent and early feature in Alzheimer disease. We previously crossed Alzheimer disease transgenic (APPsw) model mice with α-tocopherol transfer protein knock-out (Ttpa−/−) mice in which lipid peroxidation in the brain was significantly increased. The resulting double-mutant (Ttpa−/−APPsw) mice showed increased amyloid β (Aβ) deposits in the brain, which was ameliorated with α-tocopherol supplementation. To investigate the mechanism of the increased Aβ accumulation, we here studied generation, degradation, aggregation, and efflux of Aβ in the mice. The clearance of intracerebral-microinjected 125I-Aβ1–40 from brain was decreased in Ttpa−/− mice to be compared with wild-type mice, whereas the generation of Aβ was not increased in Ttpa−/−APPsw mice. The activity of an Aβ-degrading enzyme, neprilysin, did not decrease, but the expression level of insulin-degrading enzyme was markedly decreased in Ttpa−/− mouse brain. In contrast, Aβ aggregation was accelerated in Ttpa−/− mouse brains compared with wild-type brains, and well known molecules involved in Aβ transport from brain to blood, low density lipoprotein receptor-related protein-1 (LRP-1) and p-glycoprotein, were up-regulated in the small vascular fraction of Ttpa−/− mouse brains. Moreover, the disappearance of intravenously administered 125I-Aβ1–40 was decreased in Ttpa−/− mice with reduced translocation of LRP-1 in the hepatocytes. These results suggest that lipid peroxidation due to depletion of α-tocopherol impairs Aβ clearances from the brain and from the blood, possibly causing increased Aβ accumulation in Ttpa−/−APPsw mouse brain and plasma.

Intensity of chronic cerebral hypoperfusion determines white/gray matter injury and cognitive/motor dysfunction in mice.

We sought to establish a mouse model of subcortical ischemic vascular dementia (SIVD) that develops predominant white matter (WM) injury and cognitive dysfunction induced by chronic cerebral hypoperfusion. Adult C57Bl/6 male (n = 48) mice were subjected to bilateral common carotid artery stenosis with external microcoils (inner diameters: 0.16 mm, left; 0.18 mm, right). Mice were categorized according to left‐side cerebral blood flow (CBF) value on day 6 into those with severe cerebral hypoperfusion (SCH; n = 16, < 30% of preoperative CBF baseline value) or moderate cerebral hypoperfusion (MCH; n = 21, 30–50% of preoperative value). Another 15 mice were sham operated. Neurological dysfunction was evaluated by Morris water maze, rotating rod, and open field tests. Histopathological examination was performed on day 35 after surgery. MCH animals showed persistent hyperlocomotion with reduced anxiety and spatial reference memory dysfunction. Rarefaction and small necrotic lesions were predominantly confined to the WM, with reactive astrocytosis, microglial infiltration, axonal loss, and myelin disruption, and these changes were dominant on the left side. SCH animals had persistent hyperlocomotion and motor dysfunction, and their ischemic lesions extended from the WM to the hippocampus and cortex. In MCH animals, myelin basic protein and neurofilament fiber densities in the WM were correlated with the time spent in the correct area in the water maze probe trials. Our MCH mouse model with the development of several types of neurological dysfunction with high reproducibility would be useful for investigating the pathomechanisms of WM injury in human SIVD.

Intractable hiccup caused by medulla oblongata lesions: A study of an autopsy patient with possible neuromyelitis optica

We report the first autopsy verification of medulla oblongata lesions involving bilateral nucleus tractus solitarius (NTS) as a cause of intractable hiccup in an autopsy patient. The female patient first developed pain and weakness in the lower limbs and urinary incontinence at age 48, and was given a diagnosis of myelitis. Intractable hiccup was accompanied by urinary retention on the third attack. She died of respiratory failure when the fifth attack occurred at age 51. Autopsy disclosed severe involvement of the medulla oblongata and entire spinal cord. Optic nerve lesions were also identified unexpectedly. Dual involvement of the optic nerve and spinal cord, necrotic spinal cord lesions involving not only myelin but also neurons and axon, and marked extension of the spinal cord lesions in both the longitudinal and transverse directions suggested the diagnosis of neuromyelitis optica rather than multiple sclerosis. Although animal experiments have shown that NTS is a critical structure in the hiccup reflex, we demonstrated for the first time the involvement of the NTS in an autopsy patient with intractable hiccup.

Two region-dependent pathways of eosinophilic neuronal death after transient cerebral ischemia.

Various types of eosinophilic neurons (ENs) are found in the post‐ischemic brain. We examined the temporal profile of ENs in the core and peripheral regions of the ischemic cortex, and analyzed the relationship to the expression of various cell death‐related factors. Unilateral forebrain ischemia was induced in Mongolian gerbils by transient common carotid artery occlusions, and the brains from 3u2003h to 2 weeks post‐ischemia were prepared for morphometric and immunohistochemical analysis of ENs. ENs with minimally abnormal nuclei and swollen cell bodies appeared at 3u2003h in the ischemic core and at 12u2003h in the periphery. In both locations multiple cell death‐related factors including calcium, µ‐calpain, cathepsin D, 78u2003kDa glucose‐regulated protein (GRP78) and ubiquitin were activated. In the ischemic core, pyknosis and irregularly atrophic cytoplasm peaked at 12u2003h, which was associated with significant increases in staining for calcium and µ‐calpain. ENs with pyknosis and scant cytoplasm peaked at 4 days and were positive for TUNEL and calcium staining. In the ischemic periphery, ENs had slightly atrophic cytoplasm and sequentially developed pyknosis, karyorrhexis and karyolysis over 1 week. These cells were positive for TUNEL and calcium staining. All types of EN were negative for caspase 3. There may be two region‐dependent pathways of EN changes in the post‐ischemic brain: pyknosis with cytoplasmic shrinkage in the core, and nuclear disintegration with slightly atrophic cytoplasm in the periphery. This difference coordinates different activation patterns of cell death‐related factors in ENs.

Silencing efficiency differs among tissues and endogenous microRNA pathway is preserved in short hairpin RNA transgenic mice

In short hairpin RNA (shRNA) transgenic mice, the tissue difference in gene silencing efficiency and oversaturation of microRNA (miRNA) pathway have not been well assessed. We studied these problems in our previously‐reported anti‐copper/zinc superoxide dismutase (SOD1) shRNA transgenic mice. Although there was a tissue difference (liver and skeletal muscle, >95%; central nervous system and lung, ∼80%), the target gene silencing was systemic and our anti‐SOD1 shRNA transgenic mice recapitulated the SOD1‐null mice. Neither endogenous miRNAs nor their target gene levels were altered, indicating the preservation of endogenous miRNA pathways. We think that the shRNA transgenic mice can be utilized for gene analysis.

Aortic dissection as a possible cause of pure transient global amnesia: a case report and literature review

A 55-year-old man suddenly developed anterograde and retrograde amnesia. His colleagues witnessed the onset of the episode and reported that 2xa0h before the onset of the amnesic attack the patient transiently became pale. Physical examination was unremarkable and neurological examination revealed no focal neurological sign although a laboratory investigation revealed leukocytosis. Pure transient global amnesia (TGA) was diagnosed. The anterograde amnesia resolved 20xa0h after onset, but the causes of his transient paleness precedent to TGA and leukocytosis were unclear. Thirty-four hours after onset, the patient complained of sudden back pain and radiological studies revealed aortic dissection (AD; Stanford type B). We emphasize AD as a rare cause of pure TGA, because TGA in itself often has a benign natural history, but AD can be life-threatening if undiagnosed. The precedent pain, transient systemic symptoms, and leukocytosis can be red flags suggesting AD as an etiology of TGA.

Metastatic CNS lymphoma presenting with periventricular dissemination — MRI and neuropathological findings in an autopsy case

Metastatic CNS lymphoma usually manifests as pachymeningeal or leptomeningeal infiltrates, and periventricular dissemination is rare. A 70-year old man first noticed a mass in the left supraclavicular fossa, and then presented with bilateral parkinsonism, followed by consciousness disturbance. Fluid attenuated inversion recovery (FLAIR) image of brain MRI demonstrated hyperintensities at the parenchyma around the lateral ventricle, third ventricle, and fourth ventricle. Gadolinium-enhanced T1-weighted image demonstrated enhancement along the whole wall of the ventricle. Biopsy of the left supraclavicular lymph nodes established a diagnosis of diffuse large B-cell lymphoma. The patient died of multiple organ failure about 5 months after the onset. Autopsy disclosed periventricular dissemination of lymphoma cells that was most severe around the lateral ventricle. We considered that the lymphoma cells entered the ventricular system through the choroid plexus of the lateral ventricle, followed by dissemination of the periventricular parenchyma.

Japanese encephalitis - serial CT findings and neuropathology in an autopsy case.

The patient was a 17-year-old man, who developed Japanese encephalitis in the autumn of 1990 in Japan. He was admitted to our hospital 4 days after onset because of consciousness disturbance. On admission, neurological examination demonstrated left hemiparesis, neck stiffness, and Kernigs sign. He developed generalized tonico-clonic seizure, and required a respirator on the next day of admission. Brain CT 10 days after onset demonstrated hypodensities in the right hippocampus, and the CT obtained 39 days after onset showed whole brain atrophy and hypodensities in the anterior portion of the bilateral thalamus. He died 40 days after onset. Postmortem examination demonstrated perivascular and parenchymal infiltration of lymphocytes and macrophages, proliferation of microglia and astrocytes, and necrosis in the gray matter of the brain. Involvement of the hippocampus and thalamus on CT seemed to reflect the severe lesions characterized by cellular infiltration and necrosis. We discussed for the first time the correlation of CT and neuropathological findings in a patient with Japanese encephalitis.