Ryoma Morigaki

Identification and localization of a neuron-specific isoform of TAF1 in rat brain: implications for neuropathology of DYT3 dystonia.

The neuron-specific isoform of the TAF1 gene (N-TAF1) is thought to be involved in the pathogenesis of DYT3 dystonia, which leads to progressive neurodegeneration in the striatum. To determine the expression pattern of N-TAF1 transcripts, we developed a specific monoclonal antibody against the N-TAF1 protein. Here we show that in the rat brain, N-TAF1 protein appears as a nuclear protein within subsets of neurons in multiple brain regions. Of particular interest is that in the striatum, the nuclei possessing N-TAF1 protein are largely within medium spiny neurons, and they are distributed preferentially, though not exclusively, in the striosome compartment. The compartmental preference and cell type-selective distribution of N-TAF1 protein in the striatum are strikingly similar to the patterns of neuronal loss in the striatum of DYT3 patients. Our findings suggest that the distribution of N-TAF1 protein could represent a key molecular characteristic contributing to the pattern of striatal degeneration in DYT3 dystonia.

Defects in the striatal neuropeptide Y system in X-linked dystonia-parkinsonism.

Neuropeptide Y is a novel bioactive substance that plays a role in the modulation of neurogenesis and neurotransmitter release, and thereby exerts a protective influence against neurodegeneration. Using a sensitive immunohistochemical method with a tyramide signal amplification protocol, we performed a post-mortem analysis to determine the striatal localization profile of neuropeptide Y in neurologically normal individuals and in patients with X-linked dystonia-parkinsonism, a major representative of the neurodegenerative diseases that primarily involve the striatum. All of the patients examined were genetically verified as having X-linked dystonia-parkinsonism. In normal individuals, we found a scattered distribution of neuropeptide Y-positive neurons and numerous nerve fibres labelled for neuropeptide Y in the striatum. Of particular interest was a differential localization of neuropeptide Y immunoreactivity in the striatal compartments, with a heightened density of neuropeptide Y labelling in the matrix compartment relative to the striosomes. In patients with X-linked dystonia-parkinsonism, we found a significant decrease in the number of neuropeptide Y-positive cells accompanied by a marked loss of their nerve fibres in the caudate nucleus and putamen. The patients with X-linked dystonia-parkinsonism also showed a lack of neuropeptide Y labelling in the subventricular zone, where a marked loss of progenitor cells that express proliferating cell nuclear antigen was found. Our results indicate a neostriatal defect of the neuropeptide Y system in patients with X-linked dystonia-parkinsonism, suggesting its possible implication in the mechanism by which a progressive loss of striatal neurons occurs in X-linked dystonia-parkinsonism.

Olfactory type G-protein α subunit in striosome-matrix dopamine systems in adult mice

There is a growing body of evidence that striosome-matrix dopamine systems are tightly linked with motor and behavioral brain functions and disorders. In this study, we used an immunohistochemical method to show differential expression of the olfactory type G-protein alpha subunit (Galphaolf) that involves in the coupling of dopamine D1 receptor with adenylyl cyclase in the striatal compartments of adult mice, and observed heightened density of Galphaolf labeling in the striosomes relative to the matrix compartment. Our findings suggest that Galphaolf could be one of the key molecules for controlling differential responses of the striosome and matrix compartments to dopamine D1 receptor signaling in the striatum of adult mice.

Up-regulation of endogenous PML induced by a combination of interferon-beta and temozolomide enhances p73/YAP-mediated apoptosis in glioblastoma

Interferon-beta (IFN-β) is reported to augment anti-tumor effects by temozolomide in glioblastoma via down-regulation of MGMT. Promyelocytic leukemia (PML), a gene induced by IFN-β, is a tumor suppressor. Here, we report for the first time that in combination therapy, an IFN-β-induced increase in endogenous PML contributes to anti-tumor effects in p53 wild- and mutant glioma cells in a xenograft mice model. The increased PML promoted the accumulation of p73, a structural and functional homolog of p53, to fuse the coactivator Yes-associated-protein in the PML nuclear bodies. The adjuvant therapy targeted at PML may be a promising therapeutic strategy for glioblastoma.

Brush Sign on 3-T T2*-Weighted MRI as a Potential Predictor of Hemorrhagic Transformation After Tissue Plasminogen Activator Therapy

Background and Purpose— The brush sign (BS) is the enlargement of medullary veins on 3-T T2*-weighted MRI seen in patients with ischemic stroke because of major cerebral artery occlusion. However, the clinical relevance of BS in patients with acute stroke remains unclear. We assessed the correlation between detecting BS with the development of hemorrhagic transformation after intravenous thrombolysis. Methods— We enrolled consecutive patients with M1 or M2 occlusion treated with intravenous tissue plasminogen activator. We classified the patients into 2 groups: the group positive for BS (P-BS) and the group negative for BS (N-BS). We investigated the differences in MRI findings and the clinical outcome between the 2 groups. Results— The subjects consisted of 36 patients (19 men; mean age, 74.7 years). Twenty-one patients (58%) had M1 occlusion, and 15 (42%) had M2 occlusion. Twenty-five patients (69%) were classified into the P-BS group and 11 (31%) into the N-BS group. Recanalization was observed in 15 (60%) and 10 (90%) patients in the P-BS and N-BS groups, respectively (P=0.116). Hemorrhagic transformation on MRI was observed more frequently in the P-BS group than in the N-BS group (64% versus 18%; P=0.027). A good outcome (mRS, 0–1) at discharge was found in 24% of patients in the P-BS group and in 45% of patients in the N-BS group (P=0.152). A multivariate logistic regression analysis revealed that the presence of BS (odds ratio, 9.08; 95% confidence interval, 1.4–59.8; P=0.022) was independently associated with hemorrhagic transformation. Conclusions— BS may predict the development of hemorrhagic transformation in patients with acute stroke treated with intravenous tissue plasminogen activator.

A novel tyrosine kinase inhibitor AMN107 (nilotinib) normalizes striatal motor behaviors in a mouse model of Parkinson's disease.

Abnormal motor behaviors in Parkinson’s disease (PD) result from striatal dysfunction due to an imbalance between dopamine and glutamate transmissions that are integrated by dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32). c-Abelson tyrosine kinase (c-Abl) phosphorylates cyclin-dependent kinase 5 (Cdk5) at Tyr15 to increase the activity of Cdk5, which reduces the efficacy of dopaminergic signaling by phosphorylating DARPP-32 at Thr75 in the striatum. Here, we report that in the mouse striatum, a novel c-Abl inhibitor, nilotinib (AMN107), inhibits phosphorylation of both Cdk5 at Tyr15 and DARPP-32 at Thr75, which is negatively regulated by dopamine receptor activation through a D2 receptor-mediated mechanism. Like a D2-agonist, nilotinib synergizes with a D1-agonist for inducing striatal c-Fos expression. Moreover, systemic administration of nilotinib normalizes striatal motor behaviors in a mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. These findings suggest that nilotinib could possibly serve as a new and alternative agent for treating PD motor symptoms.

Deep Brain Stimulation of the Thalamic Ventral Lateral Anterior Nucleus for DYT6 Dystonia

Background: A missense mutation of the THAP1 gene results in DYT6 primary dystonia. While deep brain stimulation (DBS) of the internal globus pallidus (GPi) is effective in treating primary dystonia, recent reports indicate that GPi DBS is only mildly effective for DYT6 dystonia. Objective: To describe a patient with DYT6 dystonia who underwent thalamic ventral lateral anterior (VLa) nucleus DBS. Patient: A 35-year-old Japanese man had been experiencing upper limb dystonia and spasmodic dysphonia since the age of 15. His dystonic symptoms progressed to generalized dystonia. He was diagnosed as having DYT6 dystonia with mutations in the THAP1 gene. Because his dystonic symptoms were refractory to pharmacotherapy and pallidal DBS, he underwent thalamic VLa DBS. Results: Continuous bilateral VLa stimulation with optimal parameter settings ameliorated the patients dystonic symptoms. At the 2-year follow-up, his Burke-Fahn-Marsden Dystonia Rating Scale total score decreased from 71 to 11, an improvement of more than 80%. Conclusions: The thalamic VLa nucleus could serve as an alternative target in DBS therapy for DYT6 dystonia.

Response of striosomal opioid signaling to dopamine depletion in 6-hydroxydopamine-lesioned rat model of Parkinson's disease : a potential compensatory role

The opioid peptide receptors consist of three major subclasses, namely, μ, δ, and κ (MOR, DOR, and KOR, respectively). They are involved in the regulation of striatal dopamine functions, and increased opioid transmissions are thought to play a compensatory role in altered functions of the basal ganglia in Parkinsons disease (PD). In this study, we used an immunohistochemistry with tyramide signal amplification (TSA) protocols to determine the distributional patterns of opioid receptors in the striosome-matrix systems of the rat striatum. As a most striking feature of striatal opioid anatomy, MORs are highly enriched in the striosomes and subcallosal streak. We also found that DORs are localized in a mosaic pattern in the dorsal striatum (caudate-putamen), with heightened labeling for DOR in the striosomes relative to the matrix compartment. In the 6-hydroxydopamine-lesioned rat model of PD, lesions of the nigrostriatal pathways caused a significant reduction of striatal labeling for both the MOR and DOR in the striosomes, but not in the matrix compartment. Our results suggest that the activities of the striosome and matrix compartments are differentially regulated by the opioid signals involving the MORs and DORs, and that the striosomes may be more responsive to opioid peptides (e.g., enkephalin) than the matrix compartment. Based on a model in which the striosome compartment regulates the striatal activity, we propose a potent compensatory role of striosomal opioid signaling under the conditions of the striatal dopamine depletion that occurs in PD.

Cell type-specific localization of optineurin in the striatal neurons of mice: implications for neuronal vulnerability in Huntington's disease

Striatal neuropathology of Huntingtons disease (HD) involves primary and progressive degeneration of the medium-sized projection neurons, with relative sparing of the local circuit interneurons. The mechanism for such a patterned cell loss in the HD striatum continues to remain unclear. Optineurin (OPTN) is one of the proteins interacting with huntingtin and plays a protective role in several neurodegenerative disorders. To determine the cellular localization pattern of OPTN in the mouse striatum, we employed a highly sensitive immunohistochemistry with the tyramide signal amplification system. In this study, we show that OPTN appeared as a cytoplasmic protein within the subsets of the striatal neurons. Of particular interest was that OPTN was abundantly expressed in the interneurons, whereas low levels of OPTN were observed in the medium projection neurons. This cell type-specific distribution of OPTN in the striatum is strikingly complementary to the pattern of neuronal loss typically observed in the striatum of patients with HD. We suggest that OPTN abundance is an important cellular factor in considering the cell type-specific vulnerability of striatal neurons in HD.

Spinal Central Effects of Peripherally Applied Botulinum Neurotoxin A in Comparison between Its Subtypes A1 and A2.

Because of its unique ability to exert long-lasting synaptic transmission blockade, botulinum neurotoxin A (BoNT/A) is used to treat a wide variety of disorders involving peripheral nerve terminal hyperexcitability. However, it has been a matter of debate whether this toxin has central or peripheral sites of action. We employed a rat model in which BoNT/A1 or BoNT/A2 was unilaterally injected into the gastrocnemius muscle. On time-course measurements of compound muscle action potential (CMAP) amplitudes after injection of BoNT/A1 or BoNT/A2 at doses ranging from 1.7 to 13.6 U, CMAP amplitude for the ipsilateral hind leg was markedly decreased on the first day, and this muscle flaccidity persisted up to the 14th day. Of note, both BoNT/A1 and BoNT/A2 administrations also resulted in decreased CMAP amplitudes for the contralateral leg in a dose-dependent manner ranging from 1.7 to 13.6 U, and this muscle flaccidity increased until the fourth day and then slowly recovered. Immunohistochemical results revealed that BoNT/A-cleaved synaptosomal-associated protein of 25 kDa (SNAP-25) appeared in the bilateral ventral and dorsal horns 4 days after injection of BoNT/A1 (10 U) or BoNT/A2 (10 U), although there seemed to be a wider spread of BoNT/A-cleaved SNAP-25 associated with BoNT/A1 than BoNT/A2 in the contralateral spinal cord. This suggests that the catalytically active BoNT/A1 and BoNT/A2 were axonally transported via peripheral motor and sensory nerves to the spinal cord, where they spread through a transcytosis (cell-to-cell trafficking) mechanism. Our results provide evidence for the central effects of intramuscularly administered BoNT/A1 and BoNT/A2 in the spinal cord, and a new insight into the clinical effects of peripheral BoNT/A applications.