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  • Society for Neuroscience  (2)
  • 1
    In: The Journal of Neuroscience, Society for Neuroscience, Vol. 27, No. 42 ( 2007-10-17), p. 11279-11288
    Abstract: Long-lasting changes in synaptic function are thought to be the cellular basis for learning and memory and for activity-dependent plasticity during development. Long-term potentiation (LTP) and long-term depression (LTD) are two opposing forms of synaptic plasticity that help fine tune neural connections and possibly serve to store information in the brain. Eph receptor tyrosine kinases and their transmembrane ligands, the ephrinBs, have essential roles in certain forms of synaptic plasticity. At the CA3–CA1 hippocampal synapse, EphB2 and EphA4 receptors are critically involved in long-term plasticity independent of their cytoplasmic domains, suggesting that ephrinBs are the active signaling partners. In cell-based assays, ephrinB reverse signaling was previously shown to involve phosphotyrosine-dependent and postsynaptic density-95/Discs large/zona occludens-1 (PDZ) domain interaction-dependent pathways. Which reverse signaling mode is required at hippocampal synapses is unknown. To address this question, we used knock-in mice expressing mutant isoforms of ephrinB2 that are deficient in specific aspects of reverse signaling. Our analysis revealed that tyrosine phosphorylation sites in ephrinB2 are required to mediate normal hippocampal LTP, but not for LTD. Conversely, ephrinB2 lacking the C-terminal PDZ interaction site, but competent to undergo tyrosine phosphorylation, cannot mediate either form of long-term plasticity. Our results provide the first evidence for phosphotyrosine-dependent ephrinB reverse signaling in a neuronal network and for differential ephrinB2 reverse signaling in two forms of synaptic plasticity.
    Type of Medium: Online Resource
    ISSN: 0270-6474 , 1529-2401
    Language: English
    Publisher: Society for Neuroscience
    Publication Date: 2007
    detail.hit.zdb_id: 1475274-8
    SSG: 12
    Location Call Number Limitation Availability
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  • 2
    In: The Journal of Neuroscience, Society for Neuroscience, Vol. 34, No. 12 ( 2014-03-19), p. 4187-4199
    Abstract: Normal brain function requires balanced development of excitatory and inhibitory synapses. An imbalance in synaptic transmission underlies many brain disorders such as epilepsy, schizophrenia, and autism. Compared with excitatory synapses, relatively little is known about the molecular control of inhibitory synapse development. We used a genetic approach in mice to identify the Ig superfamily member IgSF9/Dasm1 as a candidate homophilic synaptic adhesion protein that regulates inhibitory synapse development. IgSF9 is expressed in pyramidal cells and subsets of interneurons in the CA1 region of hippocampus. Electrophysiological recordings of acute hippocampal slices revealed that genetic inactivation of the IgSF9 gene resulted in fewer functional inhibitory synapses; however, the strength of the remaining synapses was unaltered. These physiological abnormalities were correlated with decreased expression of inhibitory synapse markers in IgSF9 −/− mice, providing anatomical evidence for a reduction in inhibitory synapse numbers, whereas excitatory synapse development was normal. Surprisingly, knock-in mice expressing a mutant isoform of IgSF9 lacking the entire cytoplasmic domain ( IgSF9 ΔC/ΔC mice) had no defects in inhibitory synapse development, providing genetic evidence that IgSF9 regulates synapse development via ectodomain interactions rather than acting itself as a signaling receptor. Further, we found that IgSF9 mediated homotypic binding and cell aggregation, but failed to induce synapse formation, suggesting that IgSF9 acts as a cell adhesion molecule (CAM) to maintain synapses. Juvenile IgSF9 −/− mice exhibited increased seizure susceptibility indicative of an imbalance in synaptic excitation and inhibition. These results provide genetic evidence for a specific role of IgSF9 in inhibitory synapse development/maintenance, presumably by its CAM-like activity.
    Type of Medium: Online Resource
    ISSN: 0270-6474 , 1529-2401
    Language: English
    Publisher: Society for Neuroscience
    Publication Date: 2014
    detail.hit.zdb_id: 1475274-8
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
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