Biomedical subjects

S Tonegawa

Publications and source records attributed to S Tonegawa.

At least 55 records · Page 3Linked to original sources

PubMed1997

Dopamine D3 receptor mutant mice exhibit increased behavioral sensitivity to concurrent stimulation of D1 and D2 receptors.

The dopamine D3 receptor is expressed primarily in regions of the brain that are thought to influence motivation and motor functions. To specify in vivo D3 receptor function, we generated mutant mice lacking this receptor. Our analysis indicates that in a novel environment, D3 mutant mice are transiently more active than wild-type mice, an effect not associated with anxiety state. Moreover, D3 mutant mice exhibit enhanced behavioral sensitivity to combined injections of D1 and D2 class receptor agonists, cocaine and amphetamine. However, the combined electrophysiological effects of the same D1 and D2 agonists on single neurons within the nucleus accumbens were not altered by the D3 receptor mutation. We conclude that one function of the D3 receptor is to modulate behaviors by inhibiting the cooperative effects of postsynaptic D1 and other D2 class receptors at systems level.

Amphetamine↗

PubMed1997

Persistent multiple climbing fiber innervation of cerebellar Purkinje cells in mice lacking mGluR1.

Most of the cerebellar Purkinje cells (PCs) of an adult animal are innervated individually by a single climbing fiber (CF) that forms strong excitatory synapses with the PCs. This one-to-one relationship between a PC and a CF is a consequence of a developmentally regulated regression of the innervation of PCs by CFs. We found that, in mice deficient in the type 1 metabotropic glutamate receptor (mGluR1), the regression of supernumerary CFs ceases by the end of the second postnatal week, which is about one week earlier than in normal mice. Consequently, about one third of PCs in the mGluR1 mutant mice are innervated by multiple CFs in adulthood. We conclude that the regression of CFs normally occurs in two developmental phases and that mGluR1 plays a crucial role in the second phase.

Aging↗

PubMed1997

Molecular genetic analysis of synaptic plasticity, activity-dependent neural development, learning, and memory in the mammalian brain.

Recently, dozens of mutant mice generated with gene targeting or transgenic technologies have been shown to exhibit a distinct set of impairments in the brain and behavior. In this review, we discuss how studies of mutant mice have helped elucidate the mechanisms that underlie synaptic plasticity and the relationship of these synaptic mechanisms to the activity-dependent phase of neural development and learning and memory. We focus on the recent progress in the analysis of whisker-related pattern formation, elimination of climbing fibers, long-term potentiation, long-term depression, and various learning and memory tasks in mutant mice.

Animals↗

PubMed1996

Subregion- and cell type-restricted gene knockout in mouse brain.

Using the phage P1-derived Cre/loxP recombination system, we have developed a method to create mice in which the deletion (knockout) of virtually any gene of interest is restricted to a subregion or a specific cell type in the brain such as the pyramidal cells of the hippocampal CA1 region. The Cre/loxP recombination-based gene deletion appears to require a certain level of Cre protein expression. The brain subregional restricted gene knockout should allow a more precise analysis of the impact of a gene mutation on animal behaviors.

Animals↗

PubMed1996

The essential role of hippocampal CA1 NMDA receptor-dependent synaptic plasticity in spatial memory.

We have produced a mouse strain in which the deletion of the NMDAR1 gene is restricted to the CA1 pyramidal cells of the hippocampus by using a new and general method that allows CA1-restricted gene knockout. The mutant mice grow into adulthood without obvious abnormalities. Adult mice lack NMDA receptor-mediated synaptic currents and long-term potentiation in the CA1 synapses and exhibit impaired spatial memory but unimpaired nonspatial learning. Our results strongly suggest that activity-dependent modifications of CA1 synapses, mediated by NMDA receptors, play an essential role in the acquisition of spatial memories.

Animals↗

PubMed1996

Impaired hippocampal representation of space in CA1-specific NMDAR1 knockout mice.

To investigate the role of synaptic plasticity in the place-specific firing of the hippocampus, we have applied multiple electrode recording techniques to freely behaving mice with a CA1 pyramidal cell-specific knockout of the NMDAR1 gene. We have discovered that although the CA1 pyramidal cells of these mice retain place-related activity, there is a significant decrease in the spatial specificity of individual place fields. We have also found a striking deficit in the coordinated firing of pairs of neurons tuned to similar spatial locations. Pairs have uncorrelated firing even if their fields overlap. These results demonstrate that NMDA receptor-mediated synaptic plasticity is necessary for the proper representation of space in the CA1 region of the hippocampus.

Action Potentials↗

PubMed1996

Expression of alpha v and beta 3 integrin chains on murine lymphocytes.

The vitronectin receptor is a member of the integrin family of adhesion protein receptors and binds a broad spectrum of ligands, including fibronectin and fibrinogen in addition to vitronectin. We have generated four mAbs that recognize the murine alpha v beta 3 vitronectin receptor. Biochemical and expression analyses showed that two of the mAbs are specific for the alpha v chain, and two are specific for the beta 3 chain. The mAbs are effective blocking reagents and inhibited cell adhesion to vitronectin, fibrinogen, and fibronectin. Staining analysis revealed expression of alpha v and beta 3 on certain populations of murine thymocytes, splenocytes, and bone marrow cells. The expression of alpha v and beta 3 appeared to be modulated at specific stages of thymocyte development, suggesting a possible function for the alpha v beta 3 vitronectin receptor in T cell development.

Animals↗

PubMed1996

Cellular responses to psychomotor stimulant and neuroleptic drugs are abnormal in mice lacking the D1 dopamine receptor.

Stimulation of dopamine D1 receptors has profound effects on addictive behavior, movement control, and working memory. Many of these functions depend on dopaminergic systems in the striatum and D1-D2 dopamine receptor synergies have been implicated as well. We show here that deletion of the D1 dopamine receptor produces a neural phenotype in which amphetamine and cocaine, two addictive psychomotor stimulants, can no longer stimulate neurons in the striatum to express cFos or JunB or to regulate dynorphin. By contrast, haloperidol, a typical neuroleptic that acts preferentially at D2-class receptors, remains effective in inducing catalepsy and striatal Fos/Jun expression in the D1 mutants, and these behavioral and neural effects can be blocked by D2 dopamine receptor agonists. These findings demonstrate that D2 dopamine receptors can function without the enabling role of D1 receptors but that D1 dopamine receptors are essential for the control of gene expression and motor behavior by psychomotor stimulants.

Amphetamine↗

PubMed1996

Spinocerebellar mossy fiber terminal topography in the NR2C/PKC gamma double mutant cerebellum.

The spatiotemporal expression patterns of the NR2C subunit of the NMDA receptor and PKC gamma isoform during cerebellar development suggests that both proteins are involved in the molecular mechanisms of synaptogenesis. However, the topographic distribution of WGA-HRP labeled spinocerebellar mossy fiber terminals in NR2C/PKC gamma double mutants (n = 4) appears similar to controls (n = 3). While the results do not rule out a role for NR2C receptor subunits and the PKC gamma isoform in cerebellar synaptogenesis, they indicate that neither is necessary for the formation or maintenance of normal spinocerebellar mossy fiber afferent maps.

Animals↗

PubMed1996

Domains of the TCR beta-chain required for early thymocyte development.

The T cell receptor beta (TCR beta) chain controls the developmental transition from CD4-CD8- to CD4+8+thymocytes. We show that the extracellular constant region and the transmembrane region, but not the variable domain or cytoplasmic tail of the TCR beta chain are required for this differentiation step. TCR beta mutant chains lacking the cytoplasmic tail can be found at the cell surface both in functional TCR/CD3 complexes and in a GPI-anchored monomeric form indicating that the cytoplasmic tail of the TCR beta chain functions as an ER retention signal. The concordance between cell surface expression of the mutant chains as TCR/CD3 complexes and their capacity to mediate thymocyte differentiation supports the CD3 mediated feedback model in which preTCR/CD3 complexes control the developmental transition from CD4-CD8- to CD4+CD8+thymocytes.

Animals↗

PubMed1996

A genetic approach to study mechanisms of cocaine action.

The brain dopamine system is thought to be the major target for the neuropharmacological actions of psychomotor stimulants such as cocaine. To investigate the mechanisms of cocaine action, we used a genetic approach, the gene-targeting technique, and generated D1 dopamine receptor mutant mice. Locomotor activity analysis in response to cocaine indicates that, in contrast to control mice which showed a dose-dependent increase in locomotion, D1 receptor mutant mice exhibited a dose-dependent decrease, suggesting that D1 receptors play an essential role in mediating such effects. Extracellular single unit recording of dopamine sensitive nucleus accumbens neurons in the D1 receptor mutant mice and control mice revealed a marked reduction in the inhibitory effects of cocaine and dopamine on the generation of action potentials, suggesting that D1 receptors play a fundamental role in cocaine- and dopamine-mediated neurophysiological effects within the nucleus accumbens. From these analyses, we conclude that the D1 dopamine receptor plays essential roles in mediating these effects of cocaine. In the future, the use of this powerful genetic approach will be essential for elucidating the molecular components of the signal transduction pathway leading to anatomical, cellular and behavioral changes upon cocaine administration and dopamine neurotransmission.

Animals↗

PubMed1996

Modification of NMDA receptor channels and synaptic transmission by targeted disruption of the NR2C gene.

A novel strain of mutant mouse has been generated with a deletion of the gene encoding the NR2C subunit of the NMDA receptor, which is primarily expressed in cerebellar granule cells. Patch-clamp recordings from granule cells in thin cerebellar slices were used to assess the consequences of the gene deletion. In granule cells of wild-type animals, a wide range of single-channel conductances were observed (19-60 pS). The disruption of the NR2C gene results in the disappearance of low-conductance NMDA receptor channels ( < 37 pS) normally expressed in granule cells during developmental maturation. The NMDA receptor-mediated synaptic current is markedly potentiated in amplitude, but abbreviated in duration (with no net difference in total charge), and the non-NMDA component of the synaptic current was reduced. We conclude that the NR2C subunit contributes to functional heteromeric NMDA receptor-subunit assemblies at the mossy fiber synapse and extrasynaptic sites during maturation, and the conductance level exhibited by a given receptor macromolecule may reflect the stochiometry of subunit composition.

Animals↗

PubMed1996

gamma/delta T cell-deficient mice have impaired mucosal immunoglobulin A responses.

Mucosal tissues of mice are enriched in T cells that express the gamma/delta T cell receptor. Since the function of these cells remains unclear, we have compared mucosal immune responses in gamma/delta T cell receptor-deficient (TCRdelta-/-) mice versus control mice of the same genetic background. The frequency of intestinal immunoglobulin (Ig) A plasma cells as well as IgA levels in serum, bile, saliva, and fecal samples were markedly reduced in TCRdelta-/- mice. The TCRdelta-/- mice produced much lower levels of IgA antibodies when immunized orally with a vaccine of tetanus toxoid plus cholera toxin as adjuvant. Conversely, the antigen-specific IgM and IgG antibody responses were comparable to orally immunized control mice. Direct assessment of the cells forming antibodies against the tetanus toxoid and cholera toxin antigens indicated that significantly lower numbers of IgA antibody-producing cells were present in the intestinal lamina propria and Peyer's patches of TCRdelta-/- mice compared with the orally immunized control mice. The selective reduction of IgA responses to ingested antigens in the absence of gamma/delta T cells suggests a specialized role for gamma/delta cells in mucosal immunity.

Animals↗

PubMed1996

Neural tube defects and abnormal brain development in F52-deficient mice.

F52 is a myristoylated, alanine-rich substrate for protein kinase C. We have generated F52-deficient mice by the gene targeting technique. These mutant mice manifest severe neural tube defects that are not associated with other complex malformations, a phenotype reminiscent of common human neural tube defects. The neural tube defects observed include both exencephaly and spina bifida, and the phenotype exhibits partial penetrance with about 60% of homozygous embryos developing neural tube defects. Exencephaly is the prominent type of defect and leads to high prenatal lethality. Neural tube defects are observed in a smaller percentage of heterozygous embryos (about 10%). Abnormal brain development and tail formation occur in homozygous mutants and are likely to be secondary to the neural tube defects. Disruption of F52 in mice therefore identifies a gene whose mutation results in isolated neural tube defects and may provide an animal model for common human neural tube defects.

Animals↗

PubMed1996

Cytokine imbalance and autoantibody production in T cell receptor-alpha mutant mice with inflammatory bowel disease.

Spontaneous inflammatory bowel disease (IBD) resembling human ulcerative colitis develops in mice mutant for the T cell receptor alpha gene (TCR-alpha-/-). TCR-alpha-/- mice lack TCR-alpha/beta+ cells but contain TCR-gamma/delta+ cells and a small population of a unique CD4+, TCR-alpha-/beta+(low) cells. Since all the immunoglobulin (Ig) classes are present in these mice, help to B cells must be provided by cells other than TCR-alpha/beta+ cells. In the present study, we found serum levels of IgG1 and IgG2 to be markedly increased in TCR-alpha-/- mice with IBD as compared to TCR-alpha-/- mice without IBD or TCR-alpha+/- controls. An increase in IgG1-, IgG2a- and IgA- but not IgM-secreting mesenteric lymph node (MLN) B cells was detected in TCR-alpha-/- mutant mice. There was also a marked increase in MLN B cells secreting autoantibody (IgG) to tropomyosin, a cytoskeletal protein. Examination of the hyperplastic MLN showed a marked increase in the number of B, TCR-delta+, and CD4+ TCR-alpha-/beta+ cells, similar to the cell population observed at the site of colonic inflammation. Analysis of spontaneous cytokine production by MLN cells using an enzyme-linked immunospot assay, immunohistochemistry, and reverse transcription/polymerase chain reaction showed a decrease of interleukin 2 (IL-2) but a marked increase of IL-4 and interferon gamma (IFN-gamma) production in TCR-alpha-/- mice with IBD as compared to TCR-alpha-/- mice without IBD and TCR alpha+/- control mice. Both TCR-alpha-/beta+ and TCR-delta+ cells were found to be capable of producing IL-4; IFN-gamma was produced mostly by non-T cells, many of which were shown to be CD3- NK 1.1+ cells. We propose that the cytokine imbalance present in these mice results in expansion of B cells, production and switching of autoantibodies to IgG2 subclass, and development of IBD. It is possible that the unusual CD4+ TCR-alpha-/beta+ population and expanded TCR-gamma/delta+ population present in TCR-alpha-/- mice plays a central role in this abnormal immune response.

Animals↗

PubMed1996

Hippocampal lesions impair contextual fear conditioning in two strains of mice.

Two different strains of mice, C57BL/6J and BALB/c, with hippocampal, cortical, or sham lesions, underwent contextual fear conditioning. In both strains, contextual fear, as measured by the freezing response, was significantly impaired in hippocampus-lesioned animals compared with sham control animals. Fear conditioning was not affected in the cortical-lesioned group. Moreover, there was a strain difference in fear conditioning: The C57BL/6J mice exhibited freezing more frequently than the BALB/c mice. Consistent with previous hippocampal lesion studies in rats, these results indicate that contextual fear conditioning in mice also requires the intact hippocampus. This study provides a basis for evaluating hippocampal synaptic mechanisms in relation to contextual fear conditioning in widely available gene knockout or transgenic mice.

Animals↗

PubMed1996

Rearrangement and expression of Vzeta1, Vzeta2 and Vzeta3 TCR zeta genes in C57BL/6 mice.

We have recently described a mAb (2.11) that recognizes the Vgamma1-Jgamma4-Cgamma4 chain. With this mAb and an anti-delta mAb we separated gammadelta+ 2.11(+) and gammadelta+ 2.11(-) intraepithelial lymphocytes (i-IEL) by FACS. Transcripts of rearranged TCR Vgamma1 and Vdelta2 genes in both i-IEL populations were analyzed by PCR followed by sequence analysis of cDNA spanning the junction of variable (V) and joining (J) genes. Roughly the same number of Vgamma1 and Vgamma2 transcripts were found in the 2.11(+) population while >90% of the transcripts in the 2.11(-)population contained a Vgamma gene sequence. Furthermore, gamma transcripts in the 2.11+ population were functional, while only 30-40% of the Vgamma transcripts in either population contained an in-frame sequence. The observed frequency of transcripts is what would be expected from cell populations that have not gone through cellular selection mediated by the RCR. Expression of Vgamma mRNA in RCRalphabeta and TCRgammadelta thymocytes was studied by a technique that analyzed populations of transcripts of rearranged genes. In both T cell population similar levels of Vgamma transcripts were found and about two out of three transcripts were out-of-frame. During the cloning and sequence analysis, we indentified a clone that expresses the Vgamma segment rearranged to the Jgamma3-Cgamma region in C57BL/6 mice. Together with the PCR cloning and sequencing of the complete Cgamma region in C57BL/6 mice these data demonstrate that the Jgamma-Cgamma gene is functional in this strain. Taken together, these studies revealed that: (i) cells expressing the Vgamma1 chain are an important subset of the gammadelta i-IEL population and that they show extensive junctional diversity; (ii) there is no correlation between expression of in-frame Vgamma transcripts and expression of Vgamma2 chains at the cell surface; and (iii) cells expressing the Vgamma3 chain might be a minor subset of the gammadelta T cell population in C57BL/6 mice.

Amino Acid Sequence↗

PubMed1996

Alteration of a polyclonal to an oligoclonal immune response to cecal aerobic bacterial antigens in TCR alpha mutant mice with inflammatory bowel disease.

Since lumenal bacteria have been postulated to play an important role in the pathogenesis of inflammatory bowel disease (IBD), we investigated the humoral response to cecal aerobic bacterial antigens by Western blot analysis in TCR alpha -/- mice which spontaneously develop IBD. The sera from TCR alpha -/- mice revealed an alteration of the recognition pattern against aerobic bacterial antigens from polyclonal to oligoclonal with age. This alteration was not observed in TCR delta -/- and TCR alpha +/- mice. The alteration of the recognition pattern in TCR alpha -/- mice was associated with production of autoantibodies against tropomyosin and the development of IBD. The unique population of CD4+ TCR alpha -beta + cells in TCR alpha -/- mice may be involved in the recognition of these bacterial antigens and the absence of the alpha chain may result in the alteration of immune response.

Aging↗