Conditional Calcineurin Knockout Mice Exhibit Multiple Abnormal Behaviors Related to Schizophrenia

Proceedings of the National Academy of Sciences of the United States of America. Jul, 2003  |  Pubmed ID: 12851457

Calcineurin (CN), a calcium- and calmodulin-dependent protein phosphatase, plays a significant role in the central nervous system. Previously, we reported that forebrain-specific CN knockout mice (CN mutant mice) have impaired working memory. To further analyze the behavioral effects of CN deficiency, we subjected CN mutant mice to a comprehensive behavioral test battery. Mutant mice showed increased locomotor activity, decreased social interaction, and impairments in prepulse inhibition and latent inhibition. In addition, CN mutant mice displayed an increased response to the locomotor stimulating effects of MK-801. Collectively, the abnormalities of CN mutant mice are strikingly similar to those described for schizophrenia. We propose that alterations affecting CN signaling could comprise a contributing factor in schizophrenia pathogenesis.

Evidence for Association of Schizophrenia with Genetic Variation in the 8p21.3 Gene, PPP3CC, Encoding the Calcineurin Gamma Subunit

Proceedings of the National Academy of Sciences of the United States of America. Jul, 2003  |  Pubmed ID: 12851458

Schizophrenia is a severe psychiatric disorder characterized by a complex mode of inheritance. Forebrain-specific CNB knockout mice display a spectrum of behavioral abnormalities related to altered behaviors observed in schizophrenia patients. To examine whether calcineurin dysfunction is involved in schizophrenia etiology, we undertook studies of an initial subset of calcineurin-related genes, prioritizing ones that map to loci previously implicated in schizophrenia by linkage studies. Transmission disequilibrium studies in a large sample of affected families detected association of the PPP3CC gene, which encodes the calcineurin gamma catalytic subunit, with disease. Our results identify PPP3CC, located at 8p21.3, as a potential schizophrenia susceptibility gene and support the proposal that alterations in calcineurin signaling contribute to schizophrenia pathogenesis.

Acceleration of Visually Cued Conditioned Fear Through the Auditory Pathway

Nature Neuroscience. Sep, 2004  |  Pubmed ID: 15322551

Defensive responses elicited by sensory experiences are critical for survival. Mice acquire a conditioned fear response rapidly to an auditory cue but slowly to a visual cue, a difference in learned behavior that is likely to be mediated by direct projections to the lateral amygdala from the auditory thalamus but mainly indirect ones from the visual thalamus. Here, we show that acquisition of visually cued conditioned fear is accelerated in 'rewired' mice that have retinal projections routed to the auditory thalamus. Visual stimuli induce expression of the immediate early gene Fos (also known as c-fos) in the auditory thalamus and the lateral amygdala in rewired mice, similar to the way auditory stimuli do in control mice. Thus, the rewired auditory pathway conveys visual information and mediates rapid activity-dependent plasticity in central structures that influence learned behavior.

M2 Muscarinic Acetylcholine Receptor Knock-out Mice Show Deficits in Behavioral Flexibility, Working Memory, and Hippocampal Plasticity

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Nov, 2004  |  Pubmed ID: 15537882

Muscarinic acetylcholine receptors are known to play key roles in facilitating cognitive processes. However, the specific roles of the individual muscarinic receptor subtypes (M1-M5) in learning and memory are not well understood at present. In the present study, we used wild-type (M2+/+) and M2 receptor-deficient (M2-/-) mice to examine the potential role of M2 receptors in learning and memory and hippocampal synaptic plasticity. M2-/- mice showed significant deficits in behavioral flexibility and working memory in the Barnes circular maze and the T-maze delayed alternation tests, respectively. The behavioral deficits of M2-/- mice were associated with profound changes in neuronal plasticity studied at the Schaffer-CA1 synapse of hippocampal slices. Strikingly, short-term potentiation (STP) was abolished, and long-term potentiation (LTP) was drastically reduced after high-frequency stimulation of M2-/- hippocampi. Treatment of M2-/- hippocampal slices with the GABA(A) receptor antagonist, bicuculline, restored STP and significantly increased LTP. Whole-cell recordings from CA1 pyramidal cells demonstrated a much stronger disinhibition of GABAergic than glutamatergic transmission in M2-/- hippocampi, which was particularly prominent during stimulus trains. Increased strength of GABAergic inhibition is thus a likely mechanism underlying the impaired synaptic plasticity observed with M2-/- hippocampi. Moreover, the persistent enhancement of excitatory synaptic transmission in CA1 pyramidal cells induced by the transient application of a low concentration of a muscarinic agonist (referred to as LTP(m)) was totally abolished in M2-/- mice. Because impaired muscarinic cholinergic neurotransmission is associated with Alzheimer's disease and normal aging processes, these findings should be of considerable therapeutic relevance.

Enhanced Cocaine Responsiveness and Impaired Motor Coordination in Metabotropic Glutamate Receptor Subtype 2 Knockout Mice

Proceedings of the National Academy of Sciences of the United States of America. Mar, 2005  |  Pubmed ID: 15753323

Extensive pharmacological studies have recently emerged indicating that group 2 metabotropic glutamate receptors (mGluRs) comprising mGluR2 and mGluR3 subtypes are associated with several neurological and psychiatric disorders. mGluR2 is widely distributed both presynaptically and postsynaptically in a variety of neuronal cells, but the physiological role of mGluR2 in brain function is poorly understood. This investigation involves a comprehensive behavioral analysis of mGluR2-/- knockout (KO) mice to explore the physiological role of mGluR2 in brain function. Although, under general observation, mGluR2-/- KO mice appeared to have no behavioral abnormalities, they exhibited several lines of behavioral alterations in the enforcing and defined behavioral tests. They showed a significant increase in locomotor sensitization and conditioned place preference in association with repeated cocaine administration, indicating that mGluR2 contributes to behavioral responses implicated in reinforcement and addiction of cocaine. Upon in vivo microdialysis analysis after cocaine administration, not only did extracellular levels of dopamine increase but also the response pattern of glutamate release markedly changed in the nucleus accumbens of mGluR2-/- KO mice. The mGluR2-/- KO mice also showed significant impairment in motor coordination in the accelerating rota-rod test and exhibited hyperlocomotion in novel environmental and stressful conditions, when assessed by the open-field and forced-swim tests. These results indicate that the inhibitory mGluR2 plays a pivotal role in synaptic regulation of glutamatergic transmission in the neural network.

Tight Junctions in Schwann Cells of Peripheral Myelinated Axons: a Lesson from Claudin-19-deficient Mice

The Journal of Cell Biology. May, 2005  |  Pubmed ID: 15883201

Tight junction (TJ)-like structures have been reported in Schwann cells, but their molecular composition and physiological function remain elusive. We found that claudin-19, a novel member of the claudin family (TJ adhesion molecules in epithelia), constituted these structures. Claudin-19-deficient mice were generated, and they exhibited behavioral abnormalities that could be attributed to peripheral nervous system deficits. Electrophysiological analyses showed that the claudin-19 deficiency affected the nerve conduction of peripheral myelinated fibers. Interestingly, the overall morphology of Schwann cells lacking claudin-19 expression appeared to be normal not only in the internodal region but also at the node of Ranvier, except that TJs completely disappeared, at least from the outer/inner mesaxons. These findings have indicated that, similar to epithelial cells, Schwann cells also bear claudin-based TJs, and they have also suggested that these TJs are not involved in the polarized morphogenesis but are involved in the electrophysiological "sealing" function of Schwann cells.

[Stress and Animal Model of Psychiatric Disease]

Nihon Yakurigaku Zasshi. Folia Pharmacologica Japonica. Sep, 2005  |  Pubmed ID: 16272762

NFAT Dysregulation by Increased Dosage of DSCR1 and DYRK1A on Chromosome 21

Nature. Jun, 2006  |  Pubmed ID: 16554754

Trisomy 21 results in Down's syndrome, but little is known about how a 1.5-fold increase in gene dosage produces the pleiotropic phenotypes of Down's syndrome. Here we report that two genes, DSCR1 and DYRK1A , lie within the critical region of human chromosome 21 and act synergistically to prevent nuclear occupancy of NFATc transcription factors, which are regulators of vertebrate development. We use mathematical modelling to predict that autoregulation within the pathway accentuates the effects of trisomy of DSCR1 and DYRK1A, leading to failure to activate NFATc target genes under specific conditions. Our observations of calcineurin-and Nfatc-deficient mice, Dscr1- and Dyrk1a-overexpressing mice, mouse models of Down's syndrome and human trisomy 21 are consistent with these predictions. We suggest that the 1.5-fold increase in dosage of DSCR1 and DYRK1A cooperatively destabilizes a regulatory circuit, leading to reduced NFATc activity and many of the features of Down's syndrome. More generally, these observations suggest that the destabilization of regulatory circuits can underlie human disease.

Schizophrenia-relevant Behavioral Testing in Rodent Models: a Uniquely Human Disorder?

Biological Psychiatry. Jun, 2006  |  Pubmed ID: 16797265

Animal models are extremely useful tools in defining pathogenesis and treatment of human disease. Creating adequate animal models of complex neuropsychiatric disorders such as schizophrenia represents a particularly difficult challenge. In the case of schizophrenia, little is certain regarding the etiology or pathophysiology of the human disease. In addition, many symptoms of the disorder are difficult to measure directly in rodents. These challenges have not daunted neuroscientists who are capitalizing on even subtle overlaps between this uniquely human disorder and rodent behavior. In this perspective, we detail the features of ideal animal models of schizophrenia, the potential utility of such models, and the rodent behaviors used to model certain aspects of schizophrenia. The development of such models will provide critical tools to understand the pathogenesis of schizophrenia and novel insights into therapeutic approaches to this complex disorder.

Investigating Gene-to-behavior Pathways in Psychiatric Disorders: the Use of a Comprehensive Behavioral Test Battery on Genetically Engineered Mice

Annals of the New York Academy of Sciences. Nov, 2006  |  Pubmed ID: 17185513

We have been investigating the relationships between genes and behaviors by conducting a systematic and well-defined behavioral test battery with mice that have a mutation on a gene of interest. The behavioral test battery covers a relatively broad range of various behavioral domains such as learning and memory, sensory-motor functions, emotion, motivation, and drug sensitivity/preference. Recently, we subjected mice lacking calcineurin (CN), a calcium/calmodulin protein phosphatase, to the comprehensive behavioral test battery. The mutant mice had a severe working memory deficit, increased locomotor activity, decreased social interaction, and impairments in prepulse and latent inhibition. The abnormalities of CN mutant mice were strikingly similar to those described for schizophrenic patients. Consistent with these findings, human genetics studies in a large sample of affected families detected a significant association of the PPP3CC gene, which encodes the CN gamma catalytic subunit with schizophrenia. The idea that abnormalities in the CN signaling pathway are involved in schizophrenia pathogenesis is consistent with traditional theories of schizophrenia and with many facts known about schizophrenia. A tremendous amount of knowledge about CN has accumulated and, by utilizing this information, the studies on the pathogenesis/pathophysiology of schizophrenia and its related mental disorders will be potentially accelerated. We discuss the potential impact of a large-scale mouse phenotyping project on the study of psychiatric disorders.

Sept4, a Component of Presynaptic Scaffold and Lewy Bodies, is Required for the Suppression of Alpha-synuclein Neurotoxicity

Neuron. Feb, 2007  |  Pubmed ID: 17296554

In Parkinson disease (PD), alpha-synuclein aggregates called Lewy bodies often involve and sequester Septin4 (Sept4), a polymerizing scaffold protein. However, the pathophysiological significance of this phenomenon is unclear. Here, we show the physiological association of Sept4 with alpha-synuclein, the dopamine transporter, and other presynaptic proteins in dopaminergic neurons; mice lacking Sept4 exhibit diminished dopaminergic neurotransmission due to scarcity of these presynaptic proteins. These data demonstrate an important role for septin scaffolds in the brain. In transgenic mice that express human alpha-synuclein(A53T) (a mutant protein responsible for familial PD), loss of Sept4 significantly enhances neuropathology and locomotor deterioration. In this PD model, insoluble deposits of Ser129-phosphorylated alpha-synuclein(A53T) are negatively correlated with the dosage of Sept4. In vitro, direct association with Sept4 protects alpha-synuclein against self-aggregation and Ser129 phosphorylation. Taken together, these data show that Sept4 may be involved in PD as a dual susceptibility factor, as its insufficiency can diminish dopaminergic neurotransmission and enhance alpha-synuclein neurotoxicity.

Mouse Liaison for Integrative Brain Research

Neuroscience Research. Jun, 2007  |  Pubmed ID: 17382419

Enriched Environments Influence Depression-related Behavior in Adult Mice and the Survival of Newborn Cells in Their Hippocampi

Behavioural Brain Research. Jun, 2007  |  Pubmed ID: 17397941

Major depression is a highly prevalent mental disorder and environmental factors have been strongly implicated in its pathophysiology. Clinical studies have demonstrated that stress or depression can lead to atrophy and cell loss in the hippocampus. Studies of animal models of depression have suggested that reduced neurogenesis in the adult hippocampus might contribute to such structural changes and to the behavior of these animals. On the other hand, increased hippocampal neurogenesis can be induced by the administration of antidepressants or electroconvulsive seizure, suggesting that increased neurogenesis might be related to the treatment of depression. Thus, an enriched environment (EE), which also enhances neurogenesis, is expected to have therapeutic effects on depression-related behaviors. To investigate the effects of an EE during adulthood on these behaviors, we subjected adult mice housed in an EE for five weeks to behavioral tests. In an open field test, EE mice exhibited a decrease in the distance traveled and an increase in the amount of time spent in the center. The startle response was smaller in EE mice than in control mice. EE mice also showed reduced immobility time in a forced swim test. The immobility time in EE mice was approximately half that observed in mice treated with a tricyclic antidepressant, imipramine. In our experimental condition, increased survival of newborn cells was observed in EE mice by 5-bromo-2'-deoxyuridine (BrdU)-labeled immunohistochemistry. Double-staining of BrdU and a mature neuron marker, NeuN, revealed that the majority of surviving cells were neurons. Our results suggest that EE, which enhanced the survival of newborn neurons, shows beneficial effects on behavioral despair and habituation to a novel environment.

Impact of Brain-behavior Phenotypying of Genetically-engineered Mice on Research of Neuropsychiatric Disorders

Neuroscience Research. Jun, 2007  |  Pubmed ID: 17524507

Despite massive research efforts, the exact pathogenesis and pathophysiology of psychiatric disorders, such as schizophrenia and bipolar disorder, remain largely unknown. Animal models can serve as essential tools for investigating the etiology and treatment of such disorders. Since the introduction of gene targeting techniques, the functions of more than 10% of all known mouse genes have been investigated by creating mutant mice. Some of these mutant mouse strains were found to exhibit behavioral abnormalities reminiscent of human psychiatric disorders. In this review, we discuss the general requirements for animal models of human psychiatric disorders. We also outline our unique approach of extrapolating findings in mice to humans, and present studies on forebrain-specific calcineurin knockout mice as an example. We also discuss the impact of a large-scale mouse phenotyping on studies of psychiatric disorders and the potential utility of an "animal-model-array" of psychiatric disorders for the development of suitable therapeutic agents.

Selective Impairment of Working Memory in a Mouse Model of Chronic Cerebral Hypoperfusion

Stroke; a Journal of Cerebral Circulation. Oct, 2007  |  Pubmed ID: 17761909

We recently designed a mouse model of chronic cerebral hypoperfusion, in which the cerebral white matter is damaged without significant gray matter lesions. The behavioral characteristics of these mice were studied using a test battery for neurological and cognitive functions.

Altered Sensitivities to Morphine and Cocaine in Scaffold Protein Tamalin Knockout Mice

Proceedings of the National Academy of Sciences of the United States of America. Sep, 2007  |  Pubmed ID: 17766434

Tamalin is a scaffold protein that interacts with metabotropic glutamate receptors and the kinase-deficient neurotrophin TrkCT1 receptor and forms a protein complex with multiple protein-trafficking and intracellular signaling molecules. In culture, tamalin promotes intracellular trafficking of group 1 metabotropic glutamate receptors through its interaction with guanine nucleotide exchange factor cytohesins and causes actin reorganization and membrane ruffling via the TrkCT1/cytohesin-2 signaling mechanism. However, how tamalin serves its physiological function in vivo has remained elusive. In this study, we generated tamalin knockout (Tam(-/-) KO) mice and investigated behavioral alterations resulting from their deficiency in functional tamalin. Targeted deletion of functional tamalin altered neither the overall brain architecture nor the general behavior of the mice under ordinary conditions. However, Tam(-/-) KO mice showed a decrease in sensitivity to acute morphine-induced hyperlocomotion and morphine analgesic effects in the hot-plate test. Furthermore, tamalin deficiency impaired the ability of the animals to show conditioned place preference after repeated morphine administration and to display locomotor sensitization by chronic cocaine treatment. Upon in vivo microdialysis analysis of the nucleus accumbens, Tam(-/-) KO and wild-type mice showed no genotypic differences in their response patterns of extracellular dopamine and glutamate before or after morphine administration. These results demonstrate that the tamalin scaffold protein plays a unique role in both acute and adaptive behavioral responses to morphine and cocaine and could regulate common neural substrates implicated in drugs of abuse.

Genetic Ablation of NMDA Receptor Subunit NR3B in Mouse Reveals Motoneuronal and Nonmotoneuronal Phenotypes

The European Journal of Neuroscience. Sep, 2007  |  Pubmed ID: 17880385

NR3B is a modulatory subunit of the NMDA receptor, abundantly expressed in both cranial and spinal somatic motoneurons and at lower levels in other regions of the brain as well. Recently, we found the human NR3B gene (GRIN3B) to be highly genetically heterogeneous, and that approximately 10% of the normal European-American population lacks NR3B due to homozygous occurrence of a null allele in the gene. Therefore, it is especially important to understand the phenotypic consequences of the genetic loss of NR3B in both humans and animal models. We here provide results of behavioral analysis of mice genetically lacking NR3B, which is an ideal animal model due to homogeneity in genetic and environmental background. The NR3B(-/-) mice are viable and fertile. Consistent with the expression of NR3B in somatic motoneurons, the NR3B(-/-) mice showed a moderate but significant impairment in motor learning or coordination, and decreased activity in their home cages. Remarkably, the NR3B(-/-) mice showed a highly increased social interaction with their familiar cage mates in their home cage but moderately increased anxiety-like behaviour and decreased social interaction in a novel environment, consistent with the inhibitory role of NR3B on the functions of NMDA receptors. This work is the first reporting of the functional significance of NR3B in vivo and may give insight into the contribution of genetic variability of NR3B in the phenotypic heterogeneity among human population.

Increased Social Interaction in Mice Deficient of the Striatal Medium Spiny Neuron-specific Phosphodiesterase 10A2

Journal of Neurochemistry. Apr, 2008  |  Pubmed ID: 18088367

Cyclic nucleotide phosphodiesterase 10A (PDE10A) is a member of phosphodiesterase families that degrade cAMP and/or cGMP in distinct intracellular sites. PDE10A has a dual activity on hydrolysis of both cAMP and cGMP, and is prominently expressed in the striatum and the testis. Previous studies suggested that PDE10A is involved in regulation of locomotor activity and potentially related to psychosis, but concrete physiological roles of PDE10A remains elusive yet. In this study, we genetically inactivated PDE10A2, a prominent isoform of PDE10A in the brain, in mice, and demonstrate that PDE10A2 deficiency results in increased social interaction without any major influence on different other behaviors, along with increased levels of striatal cAMP. We also demonstrate that PDE10A2 is selectively distributed in medium spiny neurons, but not interneurons, of the striatal complex. Thus, our results establish a physiological role for PDE10A2 in regulating cAMP pathway and social interaction, and suggest that cAMP signaling cascade in striatal medium spiny neurons might be involved in regulating social interaction behavior in mice.

Smaller Dendritic Spines, Weaker Synaptic Transmission, but Enhanced Spatial Learning in Mice Lacking Shank1

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Feb, 2008  |  Pubmed ID: 18272690

Experience-dependent changes in the structure of dendritic spines may contribute to learning and memory. Encoded by three genes, the Shank family of postsynaptic scaffold proteins are abundant and enriched in the postsynaptic density (PSD) of central excitatory synapses. When expressed in cultured hippocampal neurons, Shank promotes the maturation and enlargement of dendritic spines. Recently, Shank3 has been genetically implicated in human autism, suggesting an important role for Shank proteins in normal cognitive development. Here, we report the phenotype of Shank1 knock-out mice. Shank1 mutants showed altered PSD protein composition; reduced size of dendritic spines; smaller, thinner PSDs; and weaker basal synaptic transmission. Standard measures of synaptic plasticity were normal. Behaviorally, they had increased anxiety-related behavior and impaired contextual fear memory. Remarkably, Shank1-deficient mice displayed enhanced performance in a spatial learning task; however, their long-term memory retention in this task was impaired. These results affirm the importance of Shank1 for synapse structure and function in vivo, and they highlight a differential role for Shank1 in specific cognitive processes, a feature that may be relevant to human autism spectrum disorders.

Increased Anxiety-like Behavior in Neuropsin (kallikrein-related Peptidase 8) Gene-deficient Mice

Behavioral Neuroscience. Jun, 2008  |  Pubmed ID: 18513120

Neuropsin (kallikrein-related peptidase 8) is concentrated in the hippocampus, amygdala, olfactory bulb, and prefrontal cortex. Earlier studies showed that protease deficiency causes a significant impairment of early-phase long-term potentiation in the Schaffer collateral pathway and hippocampus-dependent memory in the Y maze and Morris water maze (Z. Chen et al., 1995; A. Hirata et al., 2001; H. Tamura et al., 2006). In addition to neuropsin's participation in the hippocampal memory, amygdalar and cortical localization of the gene suggests extrahippocampal behavioral function, and the authors therefore examined neuropsin-deficient mice, including tests of sensory motor reflex, open field, light-dark transition, Rota-Rod, elevated plus-maze, hot plate, startle response-prepulse inhibition, Porsolt forced swim, Barnes maze, eight-arm radial maze, and contextual and cued fear conditioning tests. Here, the authors found increased anxiety in neuropsin-deficient mice, suggesting the involvement of this protease in emotional responses.

[Investigating Genes-to-behavior Pathways in Psychiatric Diseases: an Approach Using a Comprehensive Behavioral Test Battery on Genetically Engineered Mice]

Nihon Shinkei Seishin Yakurigaku Zasshi = Japanese Journal of Psychopharmacology. Jun, 2008  |  Pubmed ID: 18646600

We have been investigating the relationships between genes and behaviors by conducting a systematic and well-defined behavioral test battery with mice that have a mutation on a gene of interest. The behavioral test battery covers a relatively broad range of various behavioral domains such as learning and memory, sensory-motor functions, emotion, motivation, and drug sensitivity/preference. Recently, we subjected mice lacking calcineurin (CN), a calcium/calmodulin protein phosphatase, to the comprehensive behavioral test battery. The mutant mice had a severe working memory deficit, increased locomotor activity, decreased social interaction, and impairments in prepulse and latent inhibition. The abnormalities of CN mutant mice were strikingly similar to those described for schizophrenic patients. Consistent with these findings, human genetics studies in a large sample of affected families detected a significant association of the PPP3CC gene, which encodes the CN gamma catalytic subunit with schizophrenia. The idea that abnormalities in the CN signaling pathway are involved in schizophrenia pathogenesis is consistent with traditional theories of schizophrenia and with many facts known about schizophrenia. A tremendous amount of knowledge about CN has accumulated and, by utilizing this information, the studies on the pathogenesis/pathophysiology of schizophrenia and its related mental disorders will be potentially accelerated. We discuss the potential impact of a large-scale mouse phenotyping project on the study of psychiatric disorders.

Mice Lacking the Schizophrenia-associated Protein FEZ1 Manifest Hyperactivity and Enhanced Responsiveness to Psychostimulants

Human Molecular Genetics. Oct, 2008  |  Pubmed ID: 18647754

FEZ1 (fasciculation and elongation protein zeta 1), a mammalian ortholog of Caenorhabditis elegans UNC-76, interacts with DISC1 (disrupted in schizophrenia 1), a schizophrenia susceptibility gene product, and polymorphisms of human FEZ1 have been associated with schizophrenia. We have now investigated the role of FEZ1 in brain development and the pathogenesis of schizophrenia by generating mice that lack Fez1. Immunofluorescence staining revealed FEZ1 to be located predominantly in gamma-aminobutyric acid-containing interneurons. The Fez1(-/-) mice showed marked hyperactivity in a variety of behavioral tests as well as enhanced behavioral responses to the psychostimulants MK-801 and methamphetamine. In vivo microdialysis revealed that the methamphetamine-induced release of dopamine in the nucleus accumbens was exaggerated in the mutant mice, suggesting that enhanced mesolimbic dopaminergic transmission contributes to their hyperactivity phenotype. These observations implicate impairment of FEZ1 function in the pathogenesis of schizophrenia.

Identification of YWHAE, a Gene Encoding 14-3-3epsilon, As a Possible Susceptibility Gene for Schizophrenia

Human Molecular Genetics. Oct, 2008  |  Pubmed ID: 18658164

Schizophrenia is a complex mental disorder with a fairly high degree of heritability. Although the causes of schizophrenia remain unclear, it is now widely accepted that it is a neurodevelopmental and neurodegenerative disorder involving disconnectivity and disorder of the synapses. Disrupted-in-schizophrenia 1 (DISC1) is a promising candidate susceptibility gene involved in neurodevelopment, including maturation of the cerebral cortex. To identify other susceptibility genes for schizophrenia, we screened for DISC1-interacting molecules [NudE-like (NUDEL), Lissencephaly-1 (LIS1), 14-3-3epsilon (YWHAE), growth factor receptor bound protein 2 (GRB2) and Kinesin family 5A of Kinesen1 (KIF5A)], assessing a total of 25 tagging single-nucleotide polymorphisms (SNPs) in a Japanese population. We identified a YWHAE SNP (rs28365859) that showed a highly significant difference between case and control samples, with higher minor allele frequencies in controls (P(allele) = 1.01 x 10(-5) and P(genotype) = 4.08 x 10(-5) in 1429 cases and 1728 controls). Both messenger RNA transcription and protein expression of 14-3-3epsilon were also increased in the lymphocytes of healthy control subjects harboring heterozygous and homozygous minor alleles compared with homozygous major allele subjects. To further investigate a potential role for YWHAE in schizophrenia, we studied Ywhae(+/-) mice in which the level of 14-3-3epsilon protein is reduced to 50% of that in wild-type littermates. These mice displayed weak defects in working memory in the eight-arm radial maze and moderately enhanced anxiety-like behavior in the elevated plus-maze. Our results suggest that YWHAE is a possible susceptibility gene that functions protectively in schizophrenia.

Roles of Continuous Neurogenesis in the Structural and Functional Integrity of the Adult Forebrain

Nature Neuroscience. Oct, 2008  |  Pubmed ID: 18758458

Neurogenesis occurs continuously in the forebrain of adult mammals, but the functional importance of adult neurogenesis is still unclear. Here, using a genetic labeling method in adult mice, we found that continuous neurogenesis results in the replacement of the majority of granule neurons in the olfactory bulb and a substantial addition of granule neurons to the hippocampal dentate gyrus. Genetic ablation of newly formed neurons in adult mice led to a gradual decrease in the number of granule cells in the olfactory bulb, inhibition of increases in the granule cell number in the dentate gyrus and impairment of behaviors in contextual and spatial memory, which are known to depend on hippocampus. These results suggest that continuous neurogenesis is required for the maintenance and reorganization of the whole interneuron system in the olfactory bulb, the modulation and refinement of the existing neuronal circuits in the dentate gyrus and the normal behaviors involved in hippocampal-dependent memory.

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.

Comprehensive Behavioral Phenotyping of Calpastatin-knockout Mice

Molecular Brain. 2008  |  Pubmed ID: 18803809

Calpastatin is an endogenous inhibitor of calpain, intracellular calcium-activated protease. It has been suggested to be involved in molecular mechanisms of long-term plasticity and excitotoxic pathways. However, functions of calpastatin in vivo are still largely unknown. To examine the physiological roles of calpastatin, we subjected calpastatin-knockout mice to a comprehensive behavioral test battery.

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.

Mice Lacking the Kf-1 Gene Exhibit Increased Anxiety- but Not Despair-like Behavior

Frontiers in Behavioral Neuroscience. 2008  |  Pubmed ID: 18958194

KF-1 was originally identified as a protein encoded by human gene with increased expression in the cerebral cortex of a patient with Alzheimer's disease. In mouse brain, kf-1 mRNA is detected predominantly in the hippocampus and cerebellum, and kf-1 gene expression is elevated also in the frontal cortex of rats after chronic antidepressant treatments. KF-1 mediates E2-dependent ubiquitination and may modulate cellular protein levels as an E3 ubiquitin ligase, though its target proteins are not yet identified. To elucidate the role of kf-1 in the central nervous system, we generated kf-1 knockout mice by gene targeting, using Cre-lox recombination. The resulting kf-1(-/-) mice were normal and healthy in appearance. Behavioral analyses revealed that kf-1(-/-) mice showed significantly increased anxiety-like behavior compared with kf-1(+/+) littermates in the light/dark transition and elevated plus maze tests; however, no significant differences were observed in exploratory locomotion using the open field test or in behavioral despair using the forced swim and tail suspension tests. These observations suggest that KF-1 suppresses selectively anxiety under physiological conditions probably through modulating protein levels of its unknown target(s). Interestingly, kf-1(-/-) mice exhibited significantly increased prepulse inhibition, which is usually reduced in human schizophrenic patients. Thus, the kf-1(-/-) mice provide a novel animal model for elucidating molecular mechanisms of psychiatric diseases such as anxiety/depression, and may be useful for screening novel anxiolytic/antidepressant compounds.

Down-regulation of Protocadherin-alpha A Isoforms in Mice Changes Contextual Fear Conditioning and Spatial Working Memory

The European Journal of Neuroscience. Oct, 2008  |  Pubmed ID: 18973563

Diverse protocadherins (Pcdhs), which are encoded as a large cluster (composed of alpha, beta and gamma clusters) in the genome, are localized to axons and synapses. The Pcdhs have been proposed to contribute to the generation of sophisticated neural networks and to regulate brain function. To address the molecular roles of Pcdhs in regulating individual behavior, here we generated knockdown mice of Pcdh-alpha proteins and examined their behavioral abnormalities. There are two alternative splicing variants of the Pcdh-alpha constant region, Pcdh-alpha A and B isoforms, with different cytoplasmic tails. Pcdh-alpha(DeltaBneo/DeltaBneo) mice, in which the Pcdh-alpha B splicing variant was absent and the Pcdh-alpha A isoforms were down-regulated to approximately 20% of the wild-type level, exhibited enhanced contextual fear conditioning and disparities in an eight-arm radial maze. Similar abnormalities were found in Pcdh-alpha(DeltaAneo/DeltaAneo) mice, which lacked 57 amino acids of the Pcdh-alpha A cytoplasmic tail. These learning abnormalities were, however, not seen in Pcdh-alpha(DeltaB/DeltaB) mice [in which the neomycin-resistance (neo) gene cassette was removed from the Pcdh-alpha(DeltaBneo/DeltaBneo) alleles], in which the expression level of the Pcdh-alpha A isoforms was recovered, although the Pcdh-alpha B isoforms were still completely missing in the brain. In addition, the amount of 5-hydroxytryptamine increased in the hippocampus of the hypomorphic Pcdh-alpha A mutant mice but not in recovery Pcdh-alpha(DeltaB/DeltaB). These results suggested that the level of Pcdh-alpha A isoforms in the brain has an important role in regulating learning and memory functions and the amount of 5-hydroxytryptamine in the hippocampus.

Normal Mitochondrial Respiratory Function is Essential for Spatial Remote Memory in Mice

Molecular Brain. 2008  |  Pubmed ID: 19087269

Mitochondrial DNA (mtDNA) with pathogenic mutations has been found in patients with cognitive disorders. However, little is known about whether pathogenic mtDNA mutations and the resultant mitochondrial respiration deficiencies contribute to the expression of cognitive alterations, such as impairments of learning and memory. To address this point, we used two groups of trans-mitochondrial mice (mito-mice) with heteroplasmy for wild-type and pathogenically deleted (Δ) mtDNA; the "low" group carried 50% or less ΔmtDNA, and the "high" group carried more than 50% ΔmtDNA.

[Genes, Behaviors and Psychiatric Disorders]

Tanpakushitsu Kakusan Koso. Protein, Nucleic Acid, Enzyme. Mar, 2008  |  Pubmed ID: 21089339

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.

Abnormal Behavior in a Chromosome-engineered Mouse Model for Human 15q11-13 Duplication Seen in Autism

Cell. Jun, 2009  |  Pubmed ID: 19563756

Substantial evidence suggests that chromosomal abnormalities contribute to the risk of autism. The duplication of human chromosome 15q11-13 is known to be the most frequent cytogenetic abnormality in autism. We have modeled this genetic change in mice by using chromosome engineering to generate a 6.3 Mb duplication of the conserved linkage group on mouse chromosome 7. Mice with a paternal duplication display poor social interaction, behavioral inflexibility, abnormal ultrasonic vocalizations, and correlates of anxiety. An increased MBII52 snoRNA within the duplicated region, affecting the serotonin 2c receptor (5-HT2cR), correlates with altered intracellular Ca(2+) responses elicited by a 5-HT2cR agonist in neurons of mice with a paternal duplication. This chromosome-engineered mouse model for autism seems to replicate various aspects of human autistic phenotypes and validates the relevance of the human chromosome abnormality. This model will facilitate forward genetics of developmental brain disorders and serve as an invaluable tool for therapeutic development.

Mice with Altered Myelin Proteolipid Protein Gene Expression Display Cognitive Deficits Accompanied by Abnormal Neuron-glia Interactions and Decreased Conduction Velocities

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Jul, 2009  |  Pubmed ID: 19571127

Conduction velocity (CV) of myelinated axons has been shown to be regulated by oligodendrocytes even after myelination has been completed. However, how myelinating oligodendrocytes regulate CV, and what the significance of this regulation is for normal brain function remain unknown. To address these questions, we analyzed a transgenic mouse line harboring extra copies of the myelin proteolipid protein 1 (plp1) gene (plp1(tg/-) mice) at 2 months of age. At this stage, the plp1(tg/-) mice have an unaffected myelin structure with a normally appearing ion channel distribution, but the CV in all axonal tracts tested in the CNS is greatly reduced. We also found decreased axonal diameters and slightly abnormal paranodal structures, both of which can be a cause for the reduced CV. Interestingly the plp1(tg/-) mice showed altered anxiety-like behaviors, reduced prepulse inhibitions, spatial learning deficits and working memory deficit, all of which are schizophrenia-related behaviors. Our results implicate that abnormalities in the neuron-glia interactions at the paranodal junctions can result in reduced CV in the CNS, which then induces behavioral abnormalities related to schizophrenia.

Intrauterine Environment-genome Interaction and Children's Development (4): Brain-behavior Phenotypying of Genetically-engineered Mice Using a Comprehensive Behavioral Test Battery on Research of Neuropsychiatric Disorders

The Journal of Toxicological Sciences. 2009  |  Pubmed ID: 19571483

Despite massive research efforts, the exact pathogenesis and pathophysiology of psychiatric disorders, such as schizophrenia and bipolar disorder, remain largely unknown. Animal models can serve as essential tools for investigating the etiology and treatment of such disorders. Some mutant mouse strains were found to exhibit behavioral abnormalities reminiscent of human psychiatric disorders. Here we outline our unique approach of extrapolating findings in mice to humans, and present studies on alpha-CaMKII heterozygous knockout (alpha-CaMKII+/-) mice as examples. Alpha-CaMKII+/- mice have profoundly dysregulated behavior 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. By conducting a series of experiments, we discovered that almost all the neurons in the mutant DG were very similar to the immature DG neurons of normal rodents. In other words, alpha-CaMKII+/- mice have an "immature DG". We proposed 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. The impact of a large-scale mouse phenotyping on studies of psychiatric disorders and the potential utility of an "animal-model-array" of psychiatric disorders for the development of suitable therapeutic agents is also discussed.

Inhibition of Calpain Increases LIS1 Expression and Partially Rescues in Vivo Phenotypes in a Mouse Model of Lissencephaly

Nature Medicine. Oct, 2009  |  Pubmed ID: 19734909

Lissencephaly is a devastating neurological disorder caused by defective neuronal migration. LIS1 (official symbol PAFAH1B1, for platelet-activating factor acetylhydrolase, isoform 1b, subunit 1) was identified as the gene mutated in individuals with lissencephaly, and it was found to regulate cytoplasmic dynein function and localization. Here we show that inhibition or knockdown of calpains protects LIS1 from proteolysis, resulting in the augmentation of LIS1 amounts in Lis1(+/-) mouse embryonic fibroblast cells and rescue of the aberrant distribution of cytoplasmic dynein, mitochondria and beta-COP-positive vesicles. We also show that calpain inhibitors improve neuronal migration of Lis1(+/-) cerebellar granular neurons. Intraperitoneal injection of the calpain inhibitor ALLN to pregnant Lis1(+/-) dams rescued apoptotic neuronal cell death and neuronal migration defects in Lis1(+/-) offspring. Furthermore, in utero knockdown of calpain by short hairpin RNA rescued defective cortical layering in Lis1(+/-) mice. Thus, calpain inhibition is a potential therapeutic intervention for lissencephaly.

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.

KF-1 Ubiquitin Ligase: An Anxiety Suppressor

Frontiers in Neuroscience. May, 2009  |  Pubmed ID: 19753093

Anxiety is an instinct that may have developed to promote adaptive survival by evading unnecessary danger. However, excessive anxiety is disruptive and can be a basic disorder of other psychiatric diseases such as depression. The KF-1, a ubiquitin ligase located on the endoplasmic reticulum (ER), may prevent excessive anxiety; kf-1(-/-) mice exhibit selectively elevated anxiety-like behavior against light or heights. It is surmised that KF-1 degrades some target proteins, responsible for promoting anxiety, through the ER-associated degradation pathway, similar to Parkin in Parkinson's disease (PD). Parkin, another ER-ubiquitin ligase, prevents the degeneration of dopaminergic neurons by degrading the target proteins responsible for PD. Molecular phylogenetic studies have revealed that the prototype of kf-1 appeared in the very early phase of animal evolution but was lost, unlike parkin, in the lineage leading up to Drosophila. Therefore, kf-1(-/-) mice may be a powerful tool for elucidating the molecular mechanisms involved in emotional regulation, and for screening novel anxiolytic/antidepressant compounds.

Abnormalities in Brain Structure and Behavior in GSK-3alpha Mutant Mice

Molecular Brain. 2009  |  Pubmed ID: 19925672

Glycogen synthase kinase-3 (GSK-3) is a widely expressed and highly conserved serine/threonine protein kinase encoded by two genes that generate two related proteins: GSK-3alpha and GSK-3beta. Mice lacking a functional GSK-3alpha gene were engineered in our laboratory; they are viable and display insulin sensitivity. In this study, we have characterized brain functions of GSK-3alpha KO mice by using a well-established battery of behavioral tests together with neurochemical and neuroanatomical analysis.

Nardilysin Regulates Axonal Maturation and Myelination in the Central and Peripheral Nervous System

Nature Neuroscience. Dec, 2009  |  Pubmed ID: 19935654

Axonal maturation and myelination are essential processes for establishing an efficient neuronal signaling network. We found that nardilysin (N-arginine dibasic convertase, also known as Nrd1 and NRDc), a metalloendopeptidase enhancer of protein ectodomain shedding, is a critical regulator of these processes. Nrd1-/- mice had smaller brains and a thin cerebral cortex, in which there were less myelinated fibers with thinner myelin sheaths and smaller axon diameters. We also found hypomyelination in the peripheral nervous system (PNS) of Nrd1-/- mice. Neuron-specific overexpression of NRDc induced hypermyelination, indicating that the level of neuronal NRDc regulates myelin thickness. Consistent with these findings, Nrd1-/- mice had impaired motor activities and cognitive deficits. Furthermore, NRDc enhanced ectodomain shedding of neuregulin1 (NRG1), which is a master regulator of myelination in the PNS. On the basis of these data, we propose that NRDc regulates axonal maturation and myelination in the CNS and PNS, in part, through the modulation of NRG1 shedding.

Ischemia-induced Neurogenesis of Neocortical Layer 1 Progenitor Cells

Nature Neuroscience. Feb, 2010  |  Pubmed ID: 20037576

Adult mammalian neurogenesis occurs in the hippocampus and the olfactory bulb, whereas neocortical adult neurogenesis remains controversial. Several occurrences of neocortical adult neurogenesis in injured neocortex were recently reported, suggesting that neural stem cells (NSCs) or neuronal progenitor cells (NPCs) that can be activated by injury are maintained in the adult brain. However, it is not clear whether or where neocortical NSCs/NPCs exist in the brain. We found NPCs in the neocortical layer 1 of adult rats and observed that their proliferation was highly activated by global forebrain ischemia. Using retrovirus-mediated labeling of layer 1 proliferating cells with membrane-targeted green fluorescent protein, we found that the newly generated neurons were GABAergic and that the neurons were functionally integrated into the neuronal circuitry. Our results suggest that layer 1 NPCs are a source of adult neurogenesis under ischemic conditions.

SDOP-DB: a Comparative Standardized-protocol Database for Mouse Phenotypic Analyses

Bioinformatics (Oxford, England). Apr, 2010  |  Pubmed ID: 20194625

This article reports the development of SDOP-DB, which can provide definite, detailed and easy comparison of experimental protocols used in mouse phenotypic analyses among institutes or laboratories. Because SDOP-DB is fully compliant with international standards, it can act as a practical foundation for international sharing and integration of mouse phenotypic information. AVAILABILITY: SDOP-DB (http://www.brc.riken.jp/lab/bpmp/SDOP/).

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.

Reversal of Hippocampal Neuronal Maturation by Serotonergic Antidepressants

Proceedings of the National Academy of Sciences of the United States of America. May, 2010  |  Pubmed ID: 20404165

Serotonergic antidepressant drugs have been commonly used to treat mood and anxiety disorders, and increasing evidence suggests potential use of these drugs beyond current antidepressant therapeutics. Facilitation of adult neurogenesis in the hippocampal dentate gyrus has been suggested to be a candidate mechanism of action of antidepressant drugs, but this mechanism may be only one of the broad effects of antidepressants. Here we show a distinct unique action of the serotonergic antidepressant fluoxetine in transforming the phenotype of mature dentate granule cells. Chronic treatments of adult mice with fluoxetine strongly reduced expression of the mature granule cell marker calbindin. The fluoxetine treatment induced active somatic membrane properties resembling immature granule cells and markedly reduced synaptic facilitation that characterizes the mature dentate-to-CA3 signal transmission. These changes cannot be explained simply by an increase in newly generated immature neurons, but best characterized as "dematuration" of mature granule cells. This granule cell dematuration developed along with increases in the efficacy of serotonin in 5-HT(4) receptor-dependent neuromodulation and was attenuated in mice lacking the 5-HT(4) receptor. Our results suggest that serotonergic antidepressants can reverse the established state of neuronal maturation in the adult hippocampus, and up-regulation of 5-HT(4) receptor-mediated signaling may play a critical role in this distinct action of antidepressants. Such reversal of neuronal maturation could affect proper functioning of the mature hippocampal circuit, but may also cause some beneficial effects by reinstating neuronal functions that are lost during development.

A Mouse Model Characterizing Features of Vascular Dementia with Hippocampal Atrophy

Stroke; a Journal of Cerebral Circulation. Jun, 2010  |  Pubmed ID: 20448204

We have previously described effects of chronic cerebral hypoperfusion in mice with bilateral common carotid artery stenosis (BCAS) using microcoils for 30 days. These mice specifically exhibit working memory deficits attributable to frontal-subcortical circuit damage without apparent gray matter changes, indicating similarities with subcortical ischemic vascular dementia. However, as subcortical ischemic vascular dementia progresses over time, the longer-term effects that characterize the mouse model are not known.

Case Reports: Painful Limbs/moving Extremities: Report of Two Cases

Clinical Orthopaedics and Related Research. Dec, 2010  |  Pubmed ID: 20585912

BACKGROUND: Painful limbs/moving extremities is a relatively rare condition characterized by aching pain in one limb and involuntary movement in the affected fingers or toes. Its pathomechanism is unknown. We report two patients with painful limbs/moving extremities. In one patient with a painful arm and moving fingers, the symptoms were resolved after surgery. CASE DESCRIPTIONS: Patient 1 was a 36-year-old man with a painful arm and moving fingers. Treatment with administration of analgesics was not effective. Postmyelographic CT showed stenosis of the right C5/C6 foramen attributable to cervical spondylosis and a defect of the contrast material at the foramen. He was treated with cervical foraminotomy. Patient 2 was a 26-year-old woman with a painful leg and moving toes. The pain and involuntary movement appeared 2 weeks after discectomy at L5/S1. Lumbar MRI and myelography showed no indications of nerve root compression. She was treated with a lumbar nerve root block. The pain and involuntary movement completely disappeared in both patients after treatment. LITERATURE REVIEW: Numerous studies report treatments for painful limbs/moving extremities, but few report successful treatment. Recently, botulinum toxin A injection and epidural spinal cord stimulation have been used and are thought to benefit this condition. Successful surgical treatment previously was reported for only one patient. PURPOSES AND CLINICAL RELEVANCE: If imaging indicates compression of nerve tissue, we believe surgical decompression should be considered for patients with painful limbs/moving extremities who do not respond to nonoperative treatment.

[Immature Dentate Gyrus As a Candidate Endophenotype of Psychiatric Disorders]

Nihon Shinkei Seishin Yakurigaku Zasshi = Japanese Journal of Psychopharmacology. Jun, 2010  |  Pubmed ID: 20666142

Despite massive research efforts, the exact pathogenesis and pathophysiology of psychiatric disorders, such as schizophrenia and bipolar disorder, remain largely unknown. Animal models can serve as essential tools for investigating the etiology and treatment of such disorders. Some mutant mouse strains were found to exhibit behavioral abnormalities reminiscent of human psychiatric disorders. Here we outline our unique approach of extrapolating findings in mice to humans, and present studies on alpha-CaMKII heterozygous knockout (alpha-CaMKII HKO) mice as examples. Alpha-CaMKII HKO mice have profoundly dysregulated behavior 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. By conducting a series of experiments, we discovered that almost all the neurons in the mutant DG were very similar to the immature DG neurons of normal rodents. In other words, alpha-CaMKII HKO mice have an "immature DG". We proposed 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.

Behavioral Profiles of Three C57BL/6 Substrains

Frontiers in Behavioral Neuroscience. 2010  |  Pubmed ID: 20676234

C57BL/6 inbred strains of mice are widely used in knockout and transgenic research. To evaluate the loss-of-function and gain-of-function effects of the gene of interest, animal behaviors are often examined. However, an issue of C57BL/6 substrains that is not always appreciated is that behaviors are known to be strongly influenced by genetic background. To investigate the behavioral characteristics of C57BL/6 substrains, we subjected C57BL/6J, C57BL/6N, and C57BL/6C mice to a behavior test battery. We performed both a regular scale analysis, in which experimental conditions were tightly controlled, and large-scale analysis from large number of behavioral data that we have collected so far through the comprehensive behavioral test battery applied to 700-2,200 mice in total. Significant differences among the substrains were found in the results of various behavioral tests, including the open field, rotarod, elevated plus maze, prepulse inhibition, Porsolt forced swim, and spatial working memory version of the eight-arm radial maze. Our results show a divergence of behavioral performance in C57BL/6 substrains, which suggest that small genetic differences may have a great influence on behavioral phenotypes. Thus, the genetic background of different substrains should be carefully chosen, equated, and considered in the interpretation of mutant behavioral phenotypes.

Stress-evoked Tyrosine Phosphorylation of Signal Regulatory Protein α Regulates Behavioral Immobility in the Forced Swim Test

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Aug, 2010  |  Pubmed ID: 20685990

Severe stress induces changes in neuronal function that are implicated in stress-related disorders such as depression. The molecular mechanisms underlying the response of the brain to stress remain primarily unknown, however. Signal regulatory protein alpha (SIRPalpha) is an Ig-superfamily protein that undergoes tyrosine phosphorylation and binds the protein tyrosine phosphatase Shp2. Here we show that mice expressing a form of SIRPalpha that lacks most of the cytoplasmic region manifest prolonged immobility (depression-like behavior) in the forced swim (FS) test. FS stress induced marked tyrosine phosphorylation of SIRPalpha in the brain of wild-type mice through activation of Src family kinases. The SIRPalpha ligand CD47 was important for such SIRPalpha phosphorylation, and CD47-deficient mice also manifested prolonged immobility in the FS test. Moreover, FS stress-induced tyrosine phosphorylation of both the NR2B subunit of the NMDA subtype of glutamate receptor and the K+-channel subunit Kvbeta2 was regulated by SIRPalpha. Thus, tyrosine phosphorylation of SIRPalpha is important for regulation of depression-like behavior in the response of the brain to stress.

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.

Decreased Exploratory Activity in a Mouse Model of 15q Duplication Syndrome; Implications for Disturbance of Serotonin Signaling

PloS One. 2010  |  Pubmed ID: 21179543

Autism spectrum disorders (ASDs) have garnered significant attention as an important grouping of developmental brain disorders. Recent genomic studies have revealed that inherited or de novo copy number variations (CNVs) are significantly involved in the pathophysiology of ASDs. In a previous report from our laboratory, we generated mice with CNVs as a model of ASDs, with a duplicated mouse chromosome 7C that is orthologous to human chromosome 15q11-13. Behavioral analyses revealed paternally duplicated (patDp/+) mice displayed abnormal behaviors resembling the symptoms of ASDs. In the present study, we extended these findings by performing various behavioral tests with C57BL/6J patDp/+ mice, and comprehensively measuring brain monoamine levels with ex vivo high performance liquid chromatography. Compared with wild-type controls, patDp/+ mice exhibited decreased locomotor and exploratory activities in the open field test, Y-maze test, and fear-conditioning test. Furthermore, their decreased activity levels overcame increased appetite induced by 24 hours of food deprivation in the novelty suppressed feeding test. Serotonin levels in several brain regions of adult patDp/+ mice were lower than those of wild-type control, with no concurrent changes in brain levels of dopamine or norepinephrine. Moreover, analysis of monoamines in postnatal developmental stages demonstrated reduced brain levels of serotonin in young patDp/+ mice. These findings suggest that a disrupted brain serotonergic system, especially during postnatal development, may generate the phenotypes of patDp/+ mice.

The Influence of Chronic Cerebral Hypoperfusion on Cognitive Function and Amyloid β Metabolism in APP Overexpressing Mice

PloS One. 2011  |  Pubmed ID: 21305033

Cognitive impairment resulting from cerebrovascular insufficiency has been termed vascular cognitive impairment, and is generally accepted to be distinct from Alzheimer's disease resulting from a neurodegenerative process. However, it is clear that this simple dichotomy may need revision in light of the apparent occurrence of several shared features between Alzheimer's disease and vascular cognitive impairment. Nevertheless, it still remains largely unknown whether the burden of vascular- and Alzheimer-type neuropathology are independent or interdependent. Therefore, we investigated whether chronic cerebral hypoperfusion influences cognitive ability or amyloid β deposition in amyloid precursor protein (APP) overexpressing transgenic mice.

Chronic Treatment with Fluoxetine for More Than 6 Weeks Decreases Neurogenesis in the Subventricular Zone of Adult Mice

Molecular Brain. 2011  |  Pubmed ID: 21385396

Recent studies indicate that chronic treatment with serotonergic antidepressants upregulates adult neurogenesis of the dentate gyrus (DG). In contrast, some studies claimed that there was very little alteration of neurogenesis in the subventricular zone (SVZ) by the antidepressants. Since almost all of those studies treated animals with drugs for 2 to 4 weeks as chronic treatment models of antidepressants, it is possible that antidepressant treatments for longer periods would affect adult neurogenesis in the SVZ.

Synaptic E3 Ligase SCRAPPER in Contextual Fear Conditioning: Extensive Behavioral Phenotyping of Scrapper Heterozygote and Overexpressing Mutant Mice

PloS One. 2011  |  Pubmed ID: 21390313

SCRAPPER, an F-box protein coded by FBXL20, is a subunit of SCF type E3 ubiquitin ligase. SCRAPPER localizes synapses and directly binds to Rab3-interacting molecule 1 (RIM1), an essential factor for synaptic vesicle release, thus it regulates neural transmission via RIM1 degradation. A defect in SCRAPPER leads to neurotransmission abnormalities, which could subsequently result in neurodegenerative phenotypes. Because it is likely that the alteration of neural transmission in Scrapper mutant mice affect their systemic condition, we have analyzed the behavioral phenotypes of mice with decreased or increased the amount of SCRAPPER. We carried out a series of behavioral test batteries for Scrapper mutant mice. Scrapper transgenic mice overexpressing SCRAPPER in the hippocampus did not show any significant difference in every test argued in this manuscript by comparison with wild-type mice. On the other hand, heterozygotes of Scrapper knockout [SCR (+/-)] mice showed significant difference in the contextual but not cued fear conditioning test. In addition, SCR (+/-) mice altered in some tests reflecting anxiety, which implies the loss of functions of SCRAPPER in the hippocampus. The behavioral phenotypes of Scrapper mutant mice suggest that molecular degradation conferred by SCRAPPER play important roles in hippocampal-dependent fear memory formation.

Forebrain-specific Constitutively Active CaMKKα Transgenic Mice Show Deficits in Hippocampus-dependent Long-term Memory

Neurobiology of Learning and Memory. Sep, 2011  |  Pubmed ID: 21558011

The Ca(2+)/calmodulin (CaM) kinase cascade is activated by Ca(2+) influx through the voltage-dependent Ca(2+) channels and the NMDA receptor. CaM kinase kinase (CaMKK), the most upstream kinase of the CaM kinase cascade, phosphorylates and activates both CaM kinase I (CaMKI) and CaMKIV, resulting in activation of cyclic AMP-responsive element binding protein (CREB)-dependent gene transcription. Using transgenic techniques, we created mutant mice in which a constitutively active form of CaMKK1, the autoinhibitory domain truncated protein, is over-expressed specifically in the forebrain. In these mice, although performance was normal in basal activity and short-term memory, specific impairments were shown in hippocampus-dependent long-term memory after training in spatial memory tasks and after contextual fear conditioning. In cultured neurons of these mice, phosphorylation of CaMKI was significantly increased in basal states, whereas the activity range of CaMKI phosphorylation by brain-derived neurotrophic factor (BDNF) and KCl stimulation was significantly diminished in mutant mice. Our results define a critical role for CaMKKα in synaptic plasticity and the retention of hippocampus-dependent long-term memory.

P301S Mutant Human Tau Transgenic Mice Manifest Early Symptoms of Human Tauopathies with Dementia and Altered Sensorimotor Gating

PloS One. 2011  |  Pubmed ID: 21698260

Tauopathies are neurodegenerative disorders characterized by the accumulation of abnormal tau protein leading to cognitive and/or motor dysfunction. To understand the relationship between tau pathology and behavioral impairments, we comprehensively assessed behavioral abnormalities in a mouse tauopathy model expressing the human P301S mutant tau protein in the early stage of disease to detect its initial neurological manifestations. Behavioral abnormalities, shown by open field test, elevated plus-maze test, hot plate test, Y-maze test, Barnes maze test, Morris water maze test, and/or contextual fear conditioning test, recapitulated the neurological deficits of human tauopathies with dementia. Furthermore, we discovered that prepulse inhibition (PPI), a marker of sensorimotor gating, was enhanced in these animals concomitantly with initial neuropathological changes in associated brain regions. This finding provides evidence that our tauopathy mouse model displays neurofunctional abnormalities in prodromal stages of disease, since enhancement of PPI is characteristic of amnestic mild cognitive impairment, a transitional stage between normal aging and dementia such as Alzheimer's disease (AD), in contrast with attenuated PPI in AD patients. Therefore, assessment of sensorimotor gating could be used to detect the earliest manifestations of tauopathies exemplified by prodromal AD, in which abnormal tau protein may play critical roles in the onset of neuronal dysfunctions.

Relaxin-3-deficient Mice Showed Slight Alteration in Anxiety-related Behavior

Frontiers in Behavioral Neuroscience. 2011  |  Pubmed ID: 21887138

Relaxin-3 is a neuropeptide belonging to the relaxin/insulin superfamily. Studies using rodents have revealed that relaxin-3 is predominantly expressed in neurons in the nucleus incertus (NI) of the pons, the axons of which project to forebrain regions including the hypothalamus. There is evidence that relaxin-3 is involved in several functions, including food intake and stress responses. In the present study, we generated relaxin-3 gene knockout (KO) mice and examined them using a range of behavioral tests of sensory/motor functions and emotion-related behaviors. The results revealed that relaxin-3 KO mice exhibited normal growth and appearance, and were generally indistinguishable from wild genotype littermates. There was no difference in bodyweight among genotypes until at least 28 weeks after birth. In addition, there were no significant differences between wild-type and KO mice in locomotor activity, social interaction, hot plate test performance, fear conditioning, depression-like behavior, and Y-maze test performance. However, in the elevated plus maze test, KO mice exhibited a robust increase in the tendency to enter open arms, although they exhibited normal performance in a light/dark transition test and showed no difference from wild-type mice in the time spent in central area in the open field test. On the other hand, a significant increase in the acoustic startle response was observed in KO mice. These results indicate that relaxin-3 is slightly involved in the anxiety-related behavior.

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.

DIP/WISH Deficiency Enhances Synaptic Function and Performance in the Barnes Maze

Molecular Brain. 2011  |  Pubmed ID: 22018352

DIP (diaphanous interacting protein)/WISH (WASP interacting SH3 protein) is a protein involved in cytoskeletal signaling which regulates actin cytoskeleton dynamics and/or microtubules mainly through the activity of Rho-related proteins. Although it is well established that: 1) spine-head volumes change dynamically and reflect the strength of the synapse accompanying long-term functional plasticity of glutamatergic synaptic transmission and 2) actin organization is critically involved in spine formation, the involvement of DIP/WISH in these processes is unknown.

Adenomatous Polyposis Coli Heterozygous Knockout Mice Display Hypoactivity and Age-dependent Working Memory Deficits

Frontiers in Behavioral Neuroscience. 2011  |  Pubmed ID: 22347851

A tumor suppressor gene, Adenomatous polyposis coli (Apc), is expressed in the nervous system from embryonic to adulthood stages, and transmits the Wnt signaling pathway in which schizophrenia susceptibility genes, including T-cell factor 4 (TCF4) and calcineurin (CN), are involved. However, the functions of Apc in the nervous system are largely unknown. In this study, as the first evaluation of Apc function in the nervous system, we have investigated the behavioral significance of the Apc gene, applying a battery of behavioral tests to Apc heterozygous knockout (Apc(+/-)) mice. Apc(+/-) mice showed no significant impairment in neurological reflexes or sensory and motor abilities. In various tests, including light/dark transition, open-field, social interaction, eight-arm radial maze, and fear conditioning tests, Apc(+/-) mice exhibited hypoactivity. In the eight-arm radial maze, Apc(+/-) mice 6-7 weeks of age displayed almost normal performance, whereas those 11-12 weeks of age showed a severe performance deficit in working memory, suggesting that Apc is involved in working memory performance in an age-dependent manner. The possibility that anemia, which Apc(+/-) mice develop by 17 weeks of age, impairs working memory performance, however, cannot be excluded. Our results suggest that Apc plays a role in the regulation of locomotor activity and presumably working memory performance.

Inactivation of Fibroblast Growth Factor Binding Protein 3 Causes Anxiety-related Behaviors

Molecular and Cellular Neurosciences. Jan, 2011  |  Pubmed ID: 20851768

The neurobiological mechanisms of emotional modulation and the molecular pathophysiology of anxiety disorders are largely unknown. The fibroblast growth factor (FGF) family has been implicated in the regulation of many physiological and pathological processes, which include the control of emotional behaviors. The present study examined mice with a targeted deletion of the fgf-bp3 gene, which encodes a novel FGF-binding protein, in animal models relevant to anxiety. To define the behavioral consequences of FGF-BP3 deficiency, we evaluated fgf-bp3-deficient mice using anxiety-related behavioral paradigms that provide a conflict between the desire to explore an unknown area or objects and the aversion to a brightly lit open space. The fgf-bp3-deficient mice exhibited alterations in time spent in the central area of the open-field arena, were less active in the lit areas of a light/dark transition test, and had a prolonged latency to feed during a novelty-induced hypophagia test. These changes were associated with alterations in light-induced orbitofrontal cortex (OFC) activation in an extracellular signal-regulated kinase (ERK) pathway-dependent manner. These results demonstrate that FGF-BP3 is a potent mediator of anxiety-related behaviors in mice and suggest that distinct pathways regulate emotional behaviors. Therefore, FGF-BP3 plays a critical role in the regulation of emotional states and in the development of anxiety disorders and should be investigated as a therapeutic target for anxiety disease in humans.

Right-hemispheric Dominance of Spatial Memory in Split-brain Mice

Hippocampus. Feb, 2012  |  Pubmed ID: 21069782

Left-right asymmetry of human brain function has been known for a century, although much of molecular and cellular basis of brain laterality remains to be elusive. Recent studies suggest that hippocampal CA3-CA1 excitatory synapses are asymmetrically arranged, however, the functional implication of the asymmetrical circuitry has not been studied at the behavioral level. In order to address the left-right asymmetry of hippocampal function in behaving mice, we analyzed the performance of "split-brain" mice in the Barnes maze. The "split-brain" mice received ventral hippocampal commissure and corpus callosum transection in addition to deprivation of visual input from one eye. In such mice, the hippocampus in the side of visual deprivation receives sensory-driven input. Better spatial task performance was achieved by the mice which were forced to use the right hippocampus than those which were forced to use the left hippocampus. In two-choice spatial maze, forced usage of left hippocampus resulted in a comparable performance to the right counterpart, suggesting that both hippocampal hemispheres are capable of conducting spatial learning. Therefore, the results obtained from the Barnes maze suggest that the usage of the right hippocampus improves the accuracy of spatial memory. Performance of non-spatial yet hippocampus-dependent tasks (e.g. fear conditioning) was not influenced by the laterality of the hippocampus. © 2010 Wiley Periodicals, Inc.

Comprehensive Behavioral Analysis of ENU-induced Disc1-Q31L and -L100P Mutant Mice

BMC Research Notes. Feb, 2012  |  Pubmed ID: 22348257

ABSTRACT: BACKGROUND: Disrupted-in-Schizophrenia 1 (DISC1) is considered to be a candidate susceptibility gene for psychiatric disorders, including schizophrenia, bipolar disorder, and major depression. A recent study reported that N-ethyl-N-nitrosourea (ENU)-induced mutations in exon 2 of the mouse Disc1 gene, which resulted in the amino acid exchange of Q31L and L100P, caused an increase in depression-like behavior in 31 L mutant mice and schizophrenia-like behavior in 100P mutant mice; thus, these are potential animal models of psychiatric disorders. However, remaining heterozygous mutations that possibly occur in flanking genes other than Disc1 itself might induce behavioral abnormalities in the mutant mice. Here, to confirm the effects of Disc1-Q31L and Disc1-L100P mutations on behavioral phenotypes and to investigate the behaviors of the mutant mice in more detail, the mutant lines were backcrossed to C57BL/6JJcl through an additional two generations and the behaviors were analyzed using a comprehensive behavioral test battery. RESULTS: Contrary to expectations, 31 L mutant mice showed no significant behavioral differences when compared with wild-type control mice in any of the behavioral tests, including the Porsolt forced swim and tail suspension tests, commonly used tests for depression-like behavior. Also, 100P mutant mice exhibited no differences in almost all of the behavioral tests, including the prepulse inhibition test for measuring sensorimotor gating, which is known to be impaired in schizophrenia patients; however, 100P mutant mice showed higher locomotor activity compared with wild-type control mice in the light/dark transition test. CONCLUSIONS: Although these results are partially consistent with the previous study in that there was hyperactivity in 100P mutant mice, the vast majority of the results are inconsistent with those of the previous study; this discrepancy may be explained by differences in the genetic background of the mice, the laboratory environment, experimental protocols, and more. Further behavioral studies under various experimental conditions are necessary to determine whether these Disc1 mutant mouse lines are suitable animal models of schizophrenia and major depression.