Fuyuki Mitsuyama

Stimulation-Dependent Intraspinal Microtubules and Synaptic Failure in Alzheimer's Disease: A Review

There are many microtubules in axons and dendritic shafts, but it has been thought that there were fewer microtubules in spines. Recently, there have been four reports that observed the intraspinal microtubules. Because microtubules originate from the centrosome, these four reports strongly suggest a stimulation-dependent connection between the nucleus and the stimulated postsynaptic membrane by microtubules. In contrast, several pieces of evidence suggest that spine elongation may be caused by the polymerization of intraspinal microtubules. This structural mechanism for spine elongation suggests, conversely, that the synapse loss or spine loss observed in Alzheimers disease may be caused by the depolymerization of intraspinal microtubules. Based on this evidence, it is suggested that the impairment of intraspinal microtubules may cause spinal structural change and block the translocation of plasticity-related molecules between the stimulated postsynaptic membranes and the nucleus, resulting in the cognitive deficits of Alzheimers disease.

Localization of ca2+ -calmodulin to the kinetochore of C6 glioma cells: an investigation of the anti-tumour effects of calmodulin antagonists in the treatment of brain tumours

As part of our research on the anti-tumour effects of calmodulin antagonists, we examined the localization of Ca(2+)-calmodulin in mitotic C6 glioma cells. Monoclonal anticalmodulin antibodies which require Ca2+ for binding and CREST serum which recognizes kinetochores were used to stain ultrathin frozen sections. By indirect immunofluorescence and immunoelectron microscopy of colcemid-treated cells, Ca(2+)-calmodulin was present in the kinetochore region of the cell. By double label indirect immunofluorescence using anticalmodulin antibodies and CREST serum to stain untreated cells, calmodulin was found to colocalize with kinetochores. On the basis of these results, we hypothesize that Ca(2+)-calmodulin in the kinetochore depolymerizes the microtubules which are transported by dynein in the kinetochore during metaphase oscillating and anaphase poleward chromosomal movements. This hypothesis, which is currently under further investigation, may help explain a mechanism for the antitumour effects of calmodulin antagonists in the treatment of brain tumours.

Clinical investigation of the acute cerebrovascular disease

CT上確定診断された脳幹出血16例, 脳幹硬塞17例につき, CT上病変が主に橋に限局するものと, 中脳まで及んでいるものに分け, そのCT所見, 臨床症状及び予後の相違について検討した.結果 : 1) CT上認められた脳幹出血の死亡率は31%であり, 従来言われていたほど絶対的予後不良ではなかった.2) その中でも中脳病変を有する脳幹出血の生命予後が不良であった.3) 脳幹硬塞例は全例が生存しており, その生命予後は非常に良好であった.4) 脳幹硬塞ではその硬塞巣が, 中脳よりも橋から下部に認められるものの機能予後が不良であった.5) このようなCTによる脳幹病変の部位決定も, reconstruction像の応用, CT angleの選択, mortion artifactを排除するための努力, 工夫, 頻回のfollow upCTなどにより, ある程度まで可能な時代となっている.

MICROTUBULE-ASSOCIATED PROTEIN 1B RESCUES MEMORY DECLINE IN ALZHEIMER’S DISEASE MODEL MICE

Background: The classic pathologies seen in Alzheimer’s disease (AD) are amyloid plaques and neurofi brillary tangles, but synapse and spine loss have been recognised as new pathologies. Microtubules are thought to be less plentiful in spines, so it has been thought that spine shape change and molecular transportation in spines is performed mainly by actin. However, reports of the intraspinal invasion of microtubules, alternative mechanisms require investigation. Microtubule-associated protein 1B has microtubule conserving and polymerising effects and is overexpressed in Fragile X syndrome, in which spines are thin and elongated. Fragile X protein is an mRNA-binding protein and as mRNA is transported along microtubules as RNA granules by kinesine family, we suspected that Fragile X protein is conjugated with kinesin family tail and RNA granules. As a result, the mutation of this protein may cause impairment of mRNA transport to spines. This could result in low local protein synthesis in spines that may induce thin spines, and fi nally inducing MAP1B overexpression by a negative feedback mechanism. As a result, intraspinal microtubules may be elongated and spines may be elongated. It is speculated that the polymerisation of these intraspinal microtubules by MAP1B may restore spine integrity and rescue AD symptoms, however, this has not yet been proven. Method: We injected a Map1b-lentivirus chimera to the hemi-hippocampus of AD-model mice. The spatial working memory was assessed by the Y-maze and compared with non-injected mice. The change in spines by MAP1B overexpression in cultured neurons was investigated. Results: The overexpression of Map1b to the hemi-hippocampus of AD model mice rescues memory impairment. Spatial working memory assessed by the Y-maze in injected mice improved to almost normal levels within 2 days of the injection. The overexpression produced microtubule-dense remarkably enlarged spines in the cultured neurons. Map1b-lentivirus chimera injection also restored reduced postsynaptic densities in AD model mice, as assessed by protein immunoblots. Conclusions: These results suggest that MAP1B-dependent intraspinal microtubules may enhance the structural integrity of spines, restoring spine shrinkage, improving the bidirectional transportation of memory-facilitating molecules, and rescuing memory impairment in AD model mice. Research Article Microtubule-associated protein 1B rescues memory decline in Alzheimer’s disease model mice Yoshimi Mitsuyama1, Tadashi Koide2, Tetsuo Kanno3, Shizuko Nagao4, Takayuki Manabe5-7 and Fuyuki Mitsuyama3,8* 1Misuzukai, Nagoya, Japan 2Fukuyu Medical Institute, Nagoya, Japan 3Department of Neurosurgery, Fujita Health University, Aichi, Japan 4Education and Research Center of Animal Models of Human Diseases, Fujita Health University, Aichi, Japan 5Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Aichi, Japan 6Laboratory for Neuroanatomy and Neuropharmacology, Research Field of Professional Basic Medicine, Department of Nursing, Faculty of Nursing, Chukyogakuin University, Gifu, Japan 7Department of Child Development and Molecular Brain Science (Osaka University), United Graduate School of Child Development, Osaka University, Kanazawa University, Hamamatsu University School of Medicine, Chiba University, University of Fukui, Osaka, Japan 8Department of Internal Medicine, Tenjyu Hospital, Nagoya, Japan Received: 10 September, 2018 Accepted: 17 September, 2018 Published: 18 September, 2018 *Corresponding author: Dr. Fuyuki Mitsuyama, Department of Neurosurgery, Fujita-Health University, 1-98 Kutsukake, Toyoake, Aichi 470-1192, Japan, Tel: 81-562-93-9253, E-mail: https://www.peertechz.com

Amyloid beta: A putative intraspinal microtubule-depolymerizer to induce synapse loss or spinal shortening in Alzheimer's disease

Background: It has been proposed that deregulation of neuronal glycogen synthase kinase 3 (GSK3) activity, may be a key feature in Alzheimer disease pathogenesis. We have previously generated transgenic mice that conditionally overexpress GSK3b, mainly in dentate gyrus (DG), a region involved in learning and memory acquisition. We have found that a consequence of GSK3 overexpression was DG degeneration. Methods: To study whether pathology induced by GSK3b overexpression could be the consequence of the appearance of hyperphosphorylated tau, or if the modification of other GSK3 sustrates may play a more important role in that pathology, we have isolated a genetic modified mice lacking tau protein and overexpressing GSK3b. The triple transgenic mice, Tet/GSK3b/tau-/-, were generated by crossing mice expressing Tet/GSK3b and tau knockout mice. Tet/GSK3b/tau-/mice gene expression, as well as that of its controls (wild type, tau-/and Tet/ GSK3b), was confirmed. Cognitive function of 3 month-old Tet/GSK3b/ tau-/mice and wild type, tau-/and Tet/GSK3b littermates was determined in the Morris water maze. Thionine-stained brain sections, from each type of mice were analyzed in 3 and 18 months old mice to measure the DG volume. We performed immunohistochemistry with GFAP and IBA-1 antibodies to analyze reactive gliosis in the hippocampus. Results: Tet/ GSK3b/tau-/mice showed behavioural deficit in the Morris water maze, compared to wild type and tau-/mice, but it performed the task better than Tet/GSK3b mice. This result correlates with the lower DG atrophy observed in the Tet/GSK3b/tau-/mice compared to Tet/GSK3b. This degeneration in the hippocampus of Tet/GSK3b/tau-/mice was accompanied by reactive gliosis. We analyzed bcatenin levels in nucleus and cytoplasm of hippocampal neurons and we observed a reduction in bcatenin level in the nuclear fraction of Tet/GSK3b and Tet/GSK3b/tau-/compared to wild type or tau-/littermates, although the nuclear bcatenin level for Tet/GSK3b/tau-/was even slightly lower than that of Tet/GSK3 mice. Conclusions: Our results indicate that the toxic effect of GSK3 overexpression is milder in the absence of tau. Thus, we suggest that the presence of phosphotau could mediate, at least in part, the pathology observed by overexpression of GSK3 in mouse brain.