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Social animals actively engage in contact with conspecifics and experience stress upon isolation. However, the neural mechanisms coordinating the sensing and seeking of social contacts are unclear. Here we report that amylin-calcitonin receptor (Calcr) signaling in the medial preoptic area (MPOA) mediates affiliative social contacts among adult female mice. Isolation of females from free social interactions first induces active contact-seeking, then depressive-like behavior, concurrent with a loss of Amylin mRNA expression in the MPOA. Reunion with peers induces physical contacts, activates both amylin- and Calcr-expressing neurons, and leads to a recovery of Amylin mRNA expression. Chemogenetic activation of amylin neurons increases and molecular knockdown of either amylin or Calcr attenuates contact-seeking behavior, respectively. Our data provide evidence in support of a previously postulated origin of social affiliation in mammals. The mechanisms coordinating the sensing and seeking of social contacts are unclear. Here, the authors show that amylin-calcitonin receptor signalling in the media preoptic area mediates affiliative social behaviors in female mice. [ABSTRACT FROM AUTHOR]

Reduced expression of glutamate decarboxylase 67 (GAD67), encoded by the Gad1 gene, is a consistent finding in postmortem brains of patients with several psychiatric disorders, including schizophrenia, bipolar disorder and major depressive disorder. The dysfunction of GAD67 in the brain is implicated in the pathophysiology of these psychiatric disorders; however, the neurobiological consequences of GAD67 dysfunction in mature brains are not fully understood because the homozygous Gad1 knockout is lethal in newborn mice. We hypothesized that the tetracycline-controlled gene expression/suppression system could be applied to develop global GAD67 knockdown mice that would survive into adulthood. In addition, GAD67 knockdown mice would provide new insights into the neurobiological impact of GAD67 dysfunction. Here, we developed Gad1tTA/STOP−tetO biallelic knock-in mice using Gad1STOP−tetO and Gad1tTA knock-in mice, and compared them with Gad1+/+ mice. The expression level of GAD67 protein in brains of Gad1tTA/STOP−tetO mice treated with doxycycline (Dox) was decreased by approximately 90%. The GABA content was also decreased in the brains of Dox-treated Gad1tTA/STOP−tetO mice. In the open-field test, Dox-treated Gad1tTA/STOP−tetO mice exhibited hyper-locomotor activity and decreased duration spent in the center region. In addition, acoustic startle responses were impaired in Dox-treated Gad1tTA/STOP−tetO mice. These results suggest that global reduction in GAD67 elicits emotional abnormalities in mice. These GAD67 knockdown mice will be useful for elucidating the neurobiological mechanisms of emotional abnormalities, such as anxiety symptoms associated with psychiatric disorders. [ABSTRACT FROM AUTHOR]

Opalin, a central nervous system-specific myelin protein phylogenetically unique to mammals, has been suggested to play a role in mammalian-specific myelin. To elucidate the role of Opalin in mammalian myelin, we disrupted the Opalin gene in mice and analyzed the impacts on myelination and behavior. Opalin-knockout (Opalin−/−) mice were born at a Mendelian ratio and had a normal body shape and weight. Interestingly, Opalin−/− mice had no obvious abnormalities in major myelin protein compositions, expression of oligodendrocyte lineage markers, or domain organization of myelinated axons compared with WT mice (Opalin+/+) mice. Electron microscopic observation of the optic nerves did not reveal obvious differences between Opalin+/+ and Opalin−/− mice in terms of fine structures of paranodal loops, transverse bands, and multi-lamellae of myelinated axons. Moreover, sensory reflex, circadian rhythm, and locomotor activity in the home cage, as well as depression-like behavior, in the Opalin−/− mice were indistinguishable from the Opalin+/+ mice. Nevertheless, a subtle but significant impact on exploratory activity became apparent in Opalin−/− mice exposed to a novel environment. These results suggest that Opalin is not critical for central nervous system myelination or basic sensory and motor activities under conventional breeding conditions, although it might be required for fine-tuning of exploratory behavior. [ABSTRACT FROM AUTHOR]

Synaptic cell adhesion molecules are increasingly gaining attention for conferring specific properties to individual synapses. Netrin-G1 and netrin-G2 are trans-synaptic adhesion molecules that distribute on distinct axons, and their presence restricts the expression of their cognate receptors, NGL1 and NGL2, respectively, to specific subdendritic segments of target neurons. However, the neural circuits and functional roles of netrin-G isoform complexes remain unclear. Here, we use netrin-G-KO and NGL-KO mice to reveal that netrin-G1/ NGL1 and netrin-G2/NGL2 interactions specify excitatory synapses in independent hippocampalpathways. In the hippocampal CA1 area, netrin-G1/NGL1 and netrin-G2/NGL2 were expressed in the temporoammonic and Schaffer collateral pathways, respectively. The lack of presynaptic netrin-Gs led to the dispersion of NGLs from postsynaptic membranes. In accord, netrin-G mutant synapses displayed opposing phenotypes in long-term and short-term plasticity through discrete biochemical pathways. The plasticity phenotypes in netrin-G-KOs were phenocopied in NGL-KOs, with a corresponding loss of netrin-Gs from presynaptic membranes. Our findings show that netrin-G/NGL interactions differentially control synaptic plasticity in distinct circuits via retrograde signaling mechanisms and explain how synaptic inputs are diversified to control neuronal activity. [ABSTRACT FROM AUTHOR]

J. Neurochem. (2010) 112, 1035–1044. To identify a novel regulatory factor involved in brain development or synaptic plasticity, we applied the differential display PCR method to mRNA samples from NMDA-stimulated and un-stimulated neocortical cultures. Among 64 cDNA clones isolated, eight clones were novel genes and one of them encodes a novel zinc-finger protein, HIT-4, which is 317 amino acid residues (36–38 kDa) in length and contains seven C2H2 zinc-finger motifs. Rat HIT-4 cDNA exhibits strong homology to human ZNF597 (57% amino acid identity and 72% homology) and identity to rat ZNF597 at the carboxyl region. Furthermore, genomic alignment of HIT-4 cDNA indicates that the alternative use of distinct promoters and exons produces HIT-4 and ZNF597 mRNAs. Northern blotting revealed that HIT-4 mRNA (∼6 kb) is expressed in various tissues such as the lung, heart, and liver, but enriched in the brain, while ZNF597 mRNA (∼1.5 kb) is found only in the testis. To evaluate biological roles of HIT-4/ZNF597, targeted mutagenesis of this gene was performed in mice. Homozygous (−/−) mutation was embryonic lethal, ceasing embryonic organization before cardiogenesis at embryonic day 7.5. Heterozygous (+/−) mice were able to survive but showing cell degeneration and vacuolization of the striatum, cingulate cortex, and their surrounding white matter. These results reveal novel biological and pathological roles of HIT-4 in brain development and/or maintenance. [ABSTRACT FROM AUTHOR]

Down syndrome cell adhesion molecule (DSCAM) is a neural adhesion molecule that plays diverse roles in neural development. We disrupted the Dscam locus in mice and found that the null mutants (Dscam-/-) died within 24 h after birth. Whole-body plethysmography showed irregular respiration and lower ventilatory response to hypercapnia in the null mutants. Furthermore, a medulla-spinal cord preparation of Dscam-/- mice showed that the C4 ventral root activity, which drives diaphragm contraction for inspiration, had an irregular rhythm with frequent apneas. Optical imaging of the preparation using voltage-sensitive dye revealed that the pre-inspiratory neurons located in the rostral ventrolateral medulla and belonging to the rhythm generator for respiration, lost their synchroneity in Dscam-/- mice. Dscam-/- mice, which survived to adulthood without any overt abnormalities, also showed irregular respiration but milder than Dscam-/- mice. These results suggest that DSCAM plays a critical role in central respiratory regulation in a dosagedependent manner. [ABSTRACT FROM AUTHOR]

Ca2+-dependent activator protein for secretion 2 (CAPS2/CADPS2) is a secretory granule-associated protein that is abundant at the parallel fiber terminals of granule cells in the mouse cerebellum and is involved in the release of neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF), both of which are required for cerebellar development. The human homolog gene on chromosome 7 is located within susceptibility locus 1 of autism, a disease characterized by several cerebellar morphological abnormalities. Here we report that CAPS2 knock-out mice are deficient in the release of NT-3 and BDNF, and they consequently exhibit suppressed phosphorylation of Trk receptors in the cerebellum; these mice exhibit pronounced impairments in cerebellar development and functions, including neuronal survival, differentiation and migration of postmitotic granule cells, dendritogenesis of Purkinje cells, lobulation between lobules VI and VII, structure and vesicular distribution of parallel fiber--Purkinje cell synapses, paired-pulse facilitation at parallel fiber--Purkinje cell synapses, rotarod motor coordination, and eye movement plasticity in optokinetic training. Increased granule cell death of the external granular layer was noted in lobules VI-VII and IX, in which high BDNF and NT-3 levels are specifically localized during cerebellar development. Therefore, the deficiency of CAPS2 indicates that CAPS2-mediated neurotrophin release is indispensable for normal cerebellar development and functions, including neuronal differentiation and survival, morphogenesis, synaptic function, and motor leaning/control. The possible involvement of the CAPS2 gene in the cerebellar deficits of autistic patients is discussed. [ABSTRACT FROM AUTHOR]

Synaptotagmin-like protein (Slp) 2-a is a putative Rab27A/B-effector protein and is implicated in intracellular membrane transport. However, the precise tissue distribution of Slp2-a protein and its functions remain largely unknown. In this study we used a specific anti-Slp2-a antibody to investigate the tissue distribution of Slp2-a in mice and found that Slp2-a is most abundantly expressed in mouse stomach. Co-immunoprecipitation experiments indicated that Slp2-a interacts with Rab27A/B in vivo. We also discovered that Slp2-a and Rab27A/B are predominantly localized at the apical region of gastric-surface mucous cells, where mucus granules are accumulated. Analysis of Slp2-a mutant mice generated by homologous recombination showed a reduced number of mucus granules, a deficiency of granule docking with the apical plasma membrane in the gastric-surface mucous cells and reduction of mucus secretion by Slp2-a-deficient gastric primary cells. Based on these results, we propose that Slp2-a is part of the mucin secretory machinery in surface mucous cells of mouse stomach. [ABSTRACT FROM AUTHOR]

Abstract Background: Glial fibrillary acidic protein (GFAP) is the principal component of intermediate filaments (IFs) in mature astrocytes in the central nervous system (CNS). Like other IF proteins, GFAP has multiple phosphorylation sites in the N-terminal head domain. The distribution of phospho-GFAP in vivo has not been elucidated. Results: We generated Gfap hwt knock-in mice, in which the coding region for the head domain of GFAP is replaced with the corresponding human sequence. In combination with a series of monoclonal antibodies (mAbs) reactive to human phospho-GFAP, we visualized the distribution of phospho-GFAP in vivo in mice. GFAP phosphorylated at Thr7, Ser8 and/or Ser13 increased postnatally in the CNS of these mice. Limited populations of GFAP-positive astrocytes were labelled with anti-phospho-GFAP mAbs in most brain areas, whereas almost all the astrocytes in the optic nerve and spinal cord were labelled. Astrocytes in the subventricular zone and rostral migratory stream preferentially contained phospho-GFAP. In a cold injury model of the cerebral cortex, we detected phospho-GFAP in reactive astrocytes at 2–3 weeks after the injury. Conclusions: Phospho-GFAP provides a molecular marker indicating the heterogeneity of astrocytes, and Gfaphwt knock-in mice will aid in monitoring intracellular conditions of astrocytes, under various conditions. Our results suggest that the phosphorylation of GFAP plays a role in non-dividing astrocytes in vivo. [ABSTRACT FROM AUTHOR]

Background: Mutations of the SCN2A gene encoding a voltage-gated sodium channel alpha-II subunit Nav1.2 are associated with neurological disorders such as epilepsy, autism spectrum disorders, intellectual disability, and schizophrenia. However, causal relationships and pathogenic mechanisms underlying these neurological defects, especially social and psychiatric features, remain to be elucidated. Methods: We investigated the behavior of mice with a conventional or conditional deletion of Scn2a in a comprehensive test battery including open field, elevated plus maze, light-dark box, three chambers, social dominance tube, resident-intruder, ultrasonic vocalization, and fear conditioning tests. We further monitored the effects of the positive allosteric modulator of AMPA receptors CX516 on these model mice. Results: Conventional heterozygous Scn2a knockout mice (Scn2aKO/+) displayed novelty-induced exploratory hyperactivity and increased rearing. The increased vertical activity was reproduced by heterozygous inactivation of Scn2a in dorsal-telencephalic excitatory neurons but not in inhibitory neurons. Moreover, these phenotypes were rescued by treating Scn2aKO/+ mice with CX516. Additionally, Scn2aKO/+ mice displayed mild social behavior impairment, enhanced fear conditioning, and deficient fear extinction. Neuronal activity was intensified in the medial prefrontal cortex of Scn2aKO/+ mice, with an increase in the gamma band. Conclusions: Scn2aKO/+ mice exhibit a spectrum of phenotypes commonly observed in models of schizophrenia and autism spectrum disorder. Treatment with the CX516 ampakine, which ameliorates hyperactivity in these mice, could be a potential therapeutic strategy to rescue some of the disease phenotypes. [ABSTRACT FROM AUTHOR]

The mammalian cerebral cortex consists of six layers that are generated via coordinated neuronal migration during the embryonic period. Recent studies identified specific phases of radial migration of cortical neurons. After the final division, neurons transform from a multipolar to a bipolar shape within the subventricular zone-intermediate zone (SVZ-IZ) and then migrate along radial glial fibres. Mice lacking Cdk5 exhibit abnormal corticogenesis owing to neuronal migration defects. When we introduced GFP into migrating neurons at E14.5 by in utero electroporation, we observed migrating neurons in wild-type but not in Cdk5-/- embryos after 3-4 days. Introduction of the dominant-negative form of Cdk5 into the wild-type migrating neurons confirmed specific impairment of the multipolar-to-bipolar transition within the SVZ-IZ in a cell-autonomous manner. Cortex-specific Cdk5 conditional knockout mice showed inverted layering of the cerebral cortex and the layer V and callosal neurons, but not layer VI neurons, had severely impaired dendritic morphology. The amount of the dendritic protein Map2 was decreased in the cerebral cortex of Cdk5-deficient mice, and the axonal trajectory of cortical neurons within the cortex was also abnormal. These results indicate that Cdk5 is required for proper multipolar-to-bipolar transition, and a deficiency of Cdk5 results in abnormal morphology of pyramidal neurons. In addition, proper radial neuronal migration generates an inside-out pattern of cerebral cortex formation and normal axonal trajectories of cortical pyramidal neurons. [ABSTRACT FROM AUTHOR]

Astrogliosis is a pathological hallmark of the epileptic brain. The identification of mechanisms that link astrogliosis to neuronal dysfunction in epilepsy may provide new avenues for therapeutic intervention. Here we show that astrocyte-expressed adenosine kinase (ADK), a key negative regulator of the brain inhibitory molecule adenosine, is a potential predictor and modulator of epileptogenesis. In a mouse model of focal epileptogenesis, in which astrogliosis is restricted to the CA3 region of the hippocampus, we demonstrate that upregulation of ADK and spontaneous focal electroencephalographic seizures were both restricted to the affected CA3. Furthermore, spontaneous seizures in CA3 were mimicked in transgenic mice by overexpression of ADK in this brain region, implying that overexpression of ADK without astrogliosis is sufficient to cause seizures. Conversely, after pharmacological induction of an otherwise epileptogenesis-precipitating acute brain injury, transgenic mice with reduced forebrain ADK were resistant to subsequent epileptogenesis. Likewise, ADK-deficient ES cell-derived brain implants suppressed astrogliosis, upregulation of ADK, and spontaneous seizures in WT mice when implanted after the epileptogenesis-precipitating brain injury. Our findings suggest that astrocyte-based ADK provides a critical link between astrogliosis and neuronal dysfunction in epilepsy. [ABSTRACT FROM AUTHOR]

Abstract: The M5 muscarinic acetylcholine receptor (M5R) has been shown to play a crucial role in mediating acetylcholine-dependent dilation of cerebral blood vessels. We show that male M5R −/− mice displayed constitutive constriction of cerebral arteries using magnetic resonance angiography in vivo. Male M5R −/− mice exhibited a significantly reduced cerebral blood flow (CBF) in the cerebral cortex, hippocampus, basal ganglia, and thalamus. Cortical and hippocampal pyramidal neurons from M5R −/− mice showed neuronal atrophy. Hippocampus-dependent spatial and nonspatial memory was also impaired in M5R −/− mice. In M5R −/− mice, CA3 pyramidal cells displayed a significantly attenuated frequency of the spontaneous postsynaptic current and long-term potentiation was significantly impaired at the mossy fiber-CA3 synapse. Our findings suggest that impaired M5R signaling may play a role in the pathophysiology of cerebrovascular deficits. The M5 receptor may represent an attractive novel therapeutic target to ameliorate memory deficits caused by impaired cerebrovascular function. [Copyright &y& Elsevier]

Background: The netrin-G1 (NTNG1) and -G2 (NTNG2) genes, recently cloned from mouse, play a role in the formation and/or maintenance of glutamatergic neural circuitry. Accumulating evidence strongly suggests that disturbances of neuronal development and the N-methyl-d-aspartate receptor–mediated signaling system might represent a potential pathophysiology in schizophrenia. We therefore set out to examine the genetic contribution of human NTNG1 and NTNG2 to schizophrenia. Methods: Twenty-one single nucleotide polymorphisms (SNPs) from NTNG1 and 10 SNPs from NTNG2 were analyzed in 124 schizophrenic pedigrees. All genotypes were determined with the TaqMan assay. The expression levels of NTNG1 and NTNG2 were examined in the frontal (Brodmann’s Area [BA]11 and BA46) and temporal (BA22) cortices from schizophrenic and control postmortem brains. The isoform-specific expression of NTNG1 splice variants was assessed in these samples. Results: Specific haplotypes encompassing alternatively spliced exons of NTNG1 were associated with schizophrenia, and concordantly, messenger ribonucleic acid isoform expression was significantly different between schizophrenic and control brains. An association between NTNG2 and schizophrenia was also observed with SNPs and haplotypes that clustered in the 5′ region of the gene. Conclusions: The NTNG1 and NTNG2 genes might be relevant to the pathophysiology of schizophrenia. [Copyright &y& Elsevier]

Metabotropic glutamate receptor subtype 1 (mGluR1) plays an essential role in the cerebellar long-term depression (LTD). We examined the dynamic characteristics and adaptability of horizontal vestibulo-ocular reflex (HVOR) and optokinetic response (HOKR) eye movements in mGluR1 knockout mice. A mild difference was seen in the HOKR/HVOR dynamics between the wild-type and mGluR1(−/−) mice. Exposure to 1 h of sustained screen oscillation, which induced HOKR adaptation in wild-type mice, induced no change in mutant mice. These results suggest that the mGluR1 plays an essential role in the adaptation of HOKR, and LTD underlies the adaptation of ocular reflexes. [Copyright &y& Elsevier]

Classical members of the UNC6/netrin family are secreted proteins which play a role as long-range cues for directing growth cones. We here identified in mice a novel member netrin-G2 which constitute a subfamily with netrin-G1 among the UNC6/netrin family. Both of these netrin-Gs are characterized by glycosyl phosphatidyl-inositol linkage onto cells, molecular variants presumably generated by alternative splicing and lack of any appreciable affinity to receptors for classical netrins. These genes are preferentially expressed in the central nervous system with complementary distribution in most brain areas, that is netrin-G1 in the dorsal thalamus, olfactory bulb and inferior colliculus, and netrin-G2 in the cerebral cortex, habenular nucleus and superior colliculus. Consistently, immunohistochemical analysis revealed that netrin-G1 molecules are present on thalamocortical but not corticothalamic axons. Thalamic and neocortical neurons extended long neurites on immobilized recombinant netrin-G1 or netrin-G2 in vitro. Immobilized anti-netrin-G1 antibodies altered shapes of cultured thalamic neurons. We propose that netrin-Gs provide short-range cues for axonal and/or dendritic behavior through bi-directional signaling. [Copyright &y& Elsevier]