In JoVE (1)

Other Publications (12)

Articles by Keiko Toyama in JoVE

 JoVE Biology

Dissection of Hippocampal Dentate Gyrus from Adult Mouse

1Japan Science and Technology Agency, Core Research for Evolutionary Science and Technology (CREST), 2Division of Systems Medical Science, Institute for Comprehensive Medical Science, Fujita Health University, 3Department of Psychiatry, Graduate School of Medicine, Kyoto University, 4Genetic Engineering and Functional Genomics Group, Horizontal Medical Research Organization, Graduate School of Medicine, Kyoto University, 5Center for Genetic Analysis of Behavior, National Institute for Physiological Sciences, National Institutes of Natural Sciences

Other articles by Keiko Toyama on PubMed

Remote Reperfusion Lung Injury is Associated with AMP Deaminase 3 Activation and Attenuated by Inosine Monophosphate

Circulation Journal : Official Journal of the Japanese Circulation Society. Apr, 2007  |  Pubmed ID: 17384464

Remote reperfusion lung injury occurs in patients with vascular occlusion and surgical procedures. Inosine monophosphate (IMP) produced by adenosine monophosphate deaminase (AMPD) 3 is involved in the remote reperfusion injury. The purpose of the present study was to identify whether IMP administration attenuated the remote reperfusion lung injury in a skeletal muscle ischemia-reperfusion model.

Comparative Genomics Approach to the Expression of Figalpha, One of the Earliest Marker Genes of Oocyte Differentiation in Medaka (Oryzias Latipes)

Gene. Nov, 2008  |  Pubmed ID: 18678233

We analyzed molecular cascades of sex differentiation in medaka gonads by examining the transcriptional regulation of the oocyte-expressed gene, figalpha. We first confirmed that figalpha is one of the earliest marker genes of oocyte differentiation by quantitative RT-PCR and in situ hybridization. Expression of putative figalpha target genes, zpc4 and zpb, followed that of figalpha. A meiosis-specific gene, scp3, showed expression temporally and spatially similar to figalpha. To characterize the cis-regulatory sequences of figalpha, we compared genomic organizations of vertebrate figalpha genes. Both number and sequence homology of the C-terminal exons showed divergence, suggesting their less important roles. In the frog, Xenopus tropicalis, and in many teleosts, figalpha is located between hexokinase 2 and beta-adducin. We compared this genomic region for potential cis-regulatory elements and found no DNA stretches with high homology. In spite of this lack of sequence similarities, fluorescent protein transgenes surrounded with figalpha flanking sequences from the compact genomes of fugu or Tetraodon faithfully reproduced the endogenous expression of figalpha in the medaka oocytes, indicating conserved regulatory mechanisms.

Alpha-CaMKII Deficiency Causes Immature Dentate Gyrus, a Novel Candidate Endophenotype of Psychiatric Disorders

Molecular Brain. 2008  |  Pubmed ID: 18803808

Elucidating the neural and genetic factors underlying psychiatric illness is hampered by current methods of clinical diagnosis. The identification and investigation of clinical endophenotypes may be one solution, but represents a considerable challenge in human subjects. Here we report that mice heterozygous for a null mutation of the alpha-isoform of calcium/calmodulin-dependent protein kinase II (alpha-CaMKII+/-) have profoundly dysregulated behaviours and impaired neuronal development in the dentate gyrus (DG). The behavioral abnormalities include a severe working memory deficit and an exaggerated infradian rhythm, which are similar to symptoms seen in schizophrenia, bipolar mood disorder and other psychiatric disorders. Transcriptome analysis of the hippocampus of these mutants revealed that the expression levels of more than 2000 genes were significantly changed. Strikingly, among the 20 most downregulated genes, 5 had highly selective expression in the DG. Whereas BrdU incorporated cells in the mutant mouse DG was increased by more than 50 percent, the number of mature neurons in the DG was dramatically decreased. Morphological and physiological features of the DG neurons in the mutants were strikingly similar to those of immature DG neurons in normal rodents. Moreover, c-Fos expression in the DG after electric footshock was almost completely and selectively abolished in the mutants. Statistical clustering of human post-mortem brains using 10 genes differentially-expressed in the mutant mice were used to classify individuals into two clusters, one of which contained 16 of 18 schizophrenic patients. Nearly half of the differentially-expressed probes in the schizophrenia-enriched cluster encoded genes that are involved in neurogenesis or in neuronal migration/maturation, including calbindin, a marker for mature DG neurons. Based on these results, we propose that an "immature DG" in adulthood might induce alterations in behavior and serve as a promising candidate endophenotype of schizophrenia and other human psychiatric disorders.

Impaired Long-term Memory Retention and Working Memory in Sdy Mutant Mice with a Deletion in Dtnbp1, a Susceptibility Gene for Schizophrenia

Molecular Brain. 2008  |  Pubmed ID: 18945333

Schizophrenia is a complex genetic disorder caused by multiple genetic and environmental factors. The dystrobrevin-binding protein 1 (DTNBP1: dysbindin-1) gene is a major susceptibility gene for schizophrenia. Genetic variations in DTNBP1 are associated with cognitive functions, general cognitive ability and memory function, and clinical features of patients with schizophrenia including negative symptoms and cognitive decline. Since reduced expression of dysbindin-1 has been observed in postmortem brains of patients with schizophrenia, the sandy (sdy) mouse, which has a deletion in the Dtnbp1 gene and expresses no dysbindin-1 protein, could be an animal model of schizophrenia. To address this issue, we have carried out a comprehensive behavioral analysis of the sdy mouse in this study.

Comprehensive Behavioral Phenotyping of Ryanodine Receptor Type 3 (RyR3) Knockout Mice: Decreased Social Contact Duration in Two Social Interaction Tests

Frontiers in Behavioral Neuroscience. 2009  |  Pubmed ID: 19503748

Dynamic regulation of the intracellular Ca2+ concentration is crucial for various neuronal functions such as synaptic transmission and plasticity, and gene expression. Ryanodine receptors (RyRs) are a family of intracellular calcium release channels that mediate calcium-induced calcium release from the endoplasmic reticulum. Among the three RyR isoforms, RyR3 is preferentially expressed in the brain especially in the hippocampus and striatum. To investigate the behavioral effects of RyR3 deficiency, we subjected RyR3 knockout (RyR3-/-) mice to a battery of behavioral tests. RyR3-/- mice exhibited significantly decreased social contact duration in two different social interaction tests, where two mice can freely move and make contacts with each other. They also exhibited hyperactivity and mildly impaired prepulse inhibition and latent inhibition while they did not show significant abnormalities in motor function and working and reference memory tests. These results indicate that RyR3 has an important role in locomotor activity and social behavior.

Abnormal Social Behavior, Hyperactivity, Impaired Remote Spatial Memory, and Increased D1-mediated Dopaminergic Signaling in Neuronal Nitric Oxide Synthase Knockout Mice

Molecular Brain. 2009  |  Pubmed ID: 19538708

Neuronal nitric oxide synthase (nNOS) is involved in the regulation of a diverse population of intracellular messenger systems in the brain. In humans, abnormal NOS/nitric oxide metabolism is suggested to contribute to the pathogenesis and pathophysiology of some neuropsychiatric disorders, such as schizophrenia and bipolar disorder. Mice with targeted disruption of the nNOS gene exhibit abnormal behaviors. Here, we subjected nNOS knockout (KO) mice to a battery of behavioral tests to further investigate the role of nNOS in neuropsychiatric functions. We also examined the role of nNOS in dopamine/DARPP-32 signaling in striatal slices from nNOS KO mice and the effects of the administration of a dopamine D1 receptor agonist on behavior in nNOS KO mice.

The Impact of Cytogenetic Abnormalities on the Prognosis of Primary Myelofibrosis: a Prospective Survey of 202 Cases in Japan

European Journal of Haematology. Oct, 2009  |  Pubmed ID: 19549278

Cytogenetic abnormalities were often observed in primary myelofibrosis patients. The presence of specific cytogenetic abnormalities, such as sole abnormalities of chromosome 13q-, 20q-, or -7/7q-, is reported to have the influence on the prognosis of primary myelofibrosis. We analyzed the data from the prospective survey of Japanese primary myelofibrosis patients which was conducted from 1999 to clarify the impact of cytogenetic abnormalities on the prognosis of primary myelofibrosis. A total of 202 primary myelofibrosis patients had the cytogenetic and the prognostic data. Eighty (40%) out of 202 cases had cytogenetic abnormalities, and an association was evident for platelet counts. Although the presence of an abnormal karyotype did not affect the prognosis, primary myelofibrosis patients with cytogenetic abnormalities other than 13q- and 20q- showed an inferior prognosis compared to patients with a normal karyotype or sole 13q- or 20q- abnormalities. Patients with an unfavorable cytogenetic profile (abnormal cytogenetics other than 13q- or 20q-) also had a greater tendency to transform to leukemia than patients with a favorable cytogenetic profile (normal cytogenetics, sole abnormalities of either chromosome 13q-, or 20q-). Abnormal cytogenetics other than 13q- or 20q- in primary myelofibrosis patients has the poor prognostic effect for both survival and the risk of leukemic transformation.

Neural Activity Changes Underlying the Working Memory Deficit in Alpha-CaMKII Heterozygous Knockout Mice

Frontiers in Behavioral Neuroscience. 2009  |  Pubmed ID: 19750198

The alpha-isoform of calcium/calmodulin-dependent protein kinase II (alpha-CaMKII) is expressed abundantly in the forebrain and is considered to have an essential role in synaptic plasticity and cognitive function. Previously, we reported that mice heterozygous for a null mutation of alpha-CaMKII (alpha-CaMKII+/-) have profoundly dysregulated behaviors including a severe working memory deficit, which is an endophenotype of schizophrenia and other psychiatric disorders. In addition, we found that almost all the neurons in the dentate gyrus (DG) of the mutant mice failed to mature at molecular, morphological and electrophysiological levels. In the present study, to identify the brain substrates of the working memory deficit in the mutant mice, we examined the expression of the immediate early genes (IEGs), c-Fos and Arc, in the brain after a working memory version of the eight-arm radial maze test. c-Fos expression was abolished almost completely in the DG and was reduced significantly in neurons in the CA1 and CA3 areas of the hippocampus, central amygdala, and medial prefrontal cortex (mPFC). However, c-Fos expression was intact in the entorhinal and visual cortices. Immunohistochemical studies using arc promoter driven dVenus transgenic mice demonstrated that arc gene activation after the working memory task occurred in mature, but not immature neurons in the DG of wild-type mice. These results suggest crucial insights for the neural circuits underlying spatial mnemonic processing during a working memory task and suggest the involvement of alpha-CaMKII in the proper maturation and integration of DG neurons into these circuits.

Comprehensive Behavioral Analysis of Calcium/calmodulin-dependent Protein Kinase IV Knockout Mice

PloS One. 2010  |  Pubmed ID: 20209163

Calcium-calmodulin dependent protein kinase IV (CaMKIV) is a protein kinase that activates the transcription factor CREB, the cyclic AMP-response element binding protein. CREB is a key transcription factor in synaptic plasticity and memory consolidation. To elucidate the behavioral effects of CaMKIV deficiency, we subjected CaMKIV knockout (CaMKIV KO) mice to a battery of behavioral tests. CaMKIV KO had no significant effects on locomotor activity, motor coordination, social interaction, pain sensitivity, prepulse inhibition, attention, or depression-like behavior. Consistent with previous reports, CaMKIV KO mice exhibited impaired retention in a fear conditioning test 28 days after training. In contrast, however, CaMKIV KO mice did not show any testing performance deficits in passive avoidance, one of the most commonly used fear memory paradigms, 28 days after training, suggesting that remote fear memory is intact. CaMKIV KO mice exhibited intact spatial reference memory learning in the Barnes circular maze, and normal spatial working memory in an eight-arm radial maze. CaMKIV KO mice also showed mildly decreased anxiety-like behavior, suggesting that CaMKIV is involved in regulating emotional behavior. These findings indicate that CaMKIV might not be essential for fear memory or spatial memory, although it is possible that the activities of other neural mechanisms or signaling pathways compensate for the CaMKIV deficiency.

Expression of Tryptophan 2,3-dioxygenase in Mature Granule Cells of the Adult Mouse Dentate Gyrus

Molecular Brain. 2010  |  Pubmed ID: 20815922

New granule cells are continuously generated in the dentate gyrus of the adult hippocampus. During granule cell maturation, the mechanisms that differentiate new cells not only describe the degree of cell differentiation, but also crucially regulate the progression of cell differentiation. Here, we describe a gene, tryptophan 2,3-dioxygenase (TDO), whose expression distinguishes stem cells from more differentiated cells among the granule cells of the adult mouse dentate gyrus. The use of markers for proliferation, neural progenitors, and immature and mature granule cells indicated that TDO was expressed in mature cells and in some immature cells. In mice heterozygous for the alpha-isoform of calcium/calmodulin-dependent protein kinase II, in which dentate gyrus granule cells fail to mature normally, TDO immunoreactivity was substantially downregulated in the dentate gyrus granule cells. Moreover, a 5-bromo-2'-deoxyuridine labeling experiment revealed that new neurons began to express TDO between 2 and 4 wk after the neurons were generated, when the axons and dendrites of the granule cells developed and synaptogenesis occurred. These findings indicate that TDO might be required at a late-stage of granule cell development, such as during axonal and dendritic growth, synaptogenesis and its maturation.

Expression of the AMPA Receptor Subunits GluR1 and GluR2 is Associated with Granule Cell Maturation in the Dentate Gyrus

Frontiers in Neuroscience. 2011  |  Pubmed ID: 21927594

The dentate gyrus produces new granule neurons throughout adulthood in mammals from rodents to humans. During granule cell maturation, defined markers are expressed in a highly regulated sequential process, which is necessary for directed neuronal differentiation. In the present study, we show that α-amino-3-hydroxy-5-methy-4-isoxazole propionate (AMPA) receptor subunits GluR1 and GluR2 are expressed in differentiated granule cells, but not in stem cells, in neonatal, and adult dentate gyrus. Using markers for neural progenitors, immature and mature granule cells, we found that GluR1 and GluR2 were expressed mainly in mature cells and in some immature cells. A time-course analysis of 5-bromo-2'-deoxyuridine staining revealed that granule cells express GluR1 around 3 weeks after being generated. In mice heterozygous for the alpha-isoform of calcium/calmodulin-dependent protein kinase II, a putative animal model of schizophrenia and bipolar disorder in which dentate gyrus granule cells fail to mature normally, GluR1 and GluR2 immunoreactivities were substantially downregulated in the dentate gyrus granule cells. In the granule cells of mutant mice, the expression of both presynaptic and postsynaptic markers was decreased, suggesting that GluR1 and GluR2 are also associated with synaptic maturation. Moreover, GluR1 and GluR2 were also expressed in mature granule cells of the neonatal dentate gyrus. Taken together, these findings indicate that GluR1 and GluR2 expression closely correlates with the neuronal maturation state, and that GluR1 and GluR2 are useful markers for mature granule cells in the dentate gyrus.

Proteinuria in AMPD2-deficient Mice

Genes to Cells : Devoted to Molecular & Cellular Mechanisms. Jan, 2012  |  Pubmed ID: 22212473

The AMPD2 gene, a member of the AMPD gene family encoding AMP deaminase, is widely expressed in nonmuscle tissues including kidney, although its functions have not been fully elucidated. In this study, we studied the function of the AMPD2 gene by establishing AMPD2-deficient model animal. We established AMPD2 knockout mice by using gene transfer and homologous recombination in murine ES cells and studied phenotypes and functions in the kidneys of these animals. AMPD activity was decreased from 22.9 mIU/mg protein to 2.5 mIU/mg protein in the kidneys of AMPD knockout mice. In addition to changes in nucleotide metabolism in the kidneys, proteinuria was found in 3-week-old AMPD2 knockout mice, followed by a further increment up to a peak level at 6 weeks old (up to 0.6 g/dL). The major protein component in the urine of AMPD2 knockout mice was found to be albumin, indicating that AMPD2 may have a key role in glomerular filtration. Indeed, an ultrastructure study of glomerulus specimens from these mice showed effacement of the podocyte foot processes, resembling minimal-change nephropathy in humans. Based on our results, we concluded that AMPD2 deficiency induces imbalanced nucleotide metabolism and proteinuria, probably due to podocyte dysfunction.

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