Browsing by keyword "neurexin"

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    • Differential expression of neurexin genes in the mouse brain
      Uchigashima, Motokazu; Cheung, Amy; Suh, Julie; Watanabe, Masahiko; Futai, Kensuke (2019-02-13)
      Synapses, highly specialized membrane junctions between neurons, connect presynaptic neurotransmitter release sites and postsynaptic ligand-gated channels. Neurexins (Nrxns), a family of presynaptic adhesion molecules, have been characterized as major regulators of synapse development and function. Via their extracellular domains, Nrxns bind to different postsynaptic proteins, generating highly diverse functional readouts through their postsynaptic binding partners. Not surprisingly given these versatile protein interactions, mutations and deletions of Nrxn genes have been identified in patients with autism spectrum disorders, intellectual disabilities, and schizophrenia. Therefore, elucidating the expression profiles of Nrxns in the brain is of high significance. Here, using chromogenic and fluorescent in situ hybridization, we characterize the expression patterns of Nrxn isoforms throughout the brain. We found that each Nrxn isoform displays a unique expression profile in a region-, cell type-, and sensory system-specific manner. Interestingly, we also found that alphaNrxn1 and alphaNrxn2 mRNAs are expressed in non-neuronal cells, including astrocytes and oligodendrocytes. Lastly, we found diverse expression patterns of genes that encode Nrxn binding proteins, such as Neuroligins (Nlgns), Leucine-rich repeat transmembrane neuronal protein (Lrrtms) and Latrophilins (Adgrls), suggesting that Nrxn proteins can mediate numerous combinations of trans-synaptic interactions. Together, our anatomical profiling of Nrxn gene expression reflects the diverse roles of Nrxn molecules.

    • Molecular Mechanisms Directing Spine Outgrowth and Synaptic Partner Selection in Caenorhabditis elegans
      Oliver, Devyn; Alexander, Kellianne; Francis, Michael M. (2018-12-02)
      The development of the nervous system requires precise outgrowth, extension, and wiring of both axons and dendrites to generate properly functioning neural circuits. The molecular mechanisms that shape neurite development, in particular dendritic development, remain incompletely understood. Dendrites are often highly branched and coated with actin-filled, thorny protrusions, called dendritic spines, that allow for increased numbers of synaptic contacts with neighboring neurons. Disruptions in dendritic spine development have been implicated in many neurological disorders such as autism, schizophrenia, and Alzheimer's disease. Although the development of dendritic spines is vital for cognitive function, understanding the mechanisms driving their outgrowth and stabilization in vivo remains a challenge. Our recent work identifies the presence of dendritic spine-like structures in the nematode Caenorhabditis elegans and provides initial insights into mechanisms promoting spine outgrowth in this system. Specifically, we show that neurexin/nrx-1 is a critical molecular component in directing the development of synaptic connections and promoting spine outgrowth. Our investigation provides important insights into the molecular machinery that sculpt synaptic connectivity, and continuing efforts in this system offer the potential for identifying new mechanisms governing both synaptic partner selection and dendritic spine outgrowth.

    • The Role of Neurexins in Serotonin Signaling and Complex Behaviors
      Cheung, Amy (2021-04-27)
      Extensive serotonin (5-HT) fiber innervation throughout the brain corroborates 5-HT’s modulatory role in numerous behaviors including social behavior, emotion regulation, and learning and memory. Abnormal brain 5-HT levels and function are implicated in Autism Spectrum Disorder (ASD) which often co-occurs with other neuropsychiatric conditions. While 5-HT therapeutics are used to treat ASD, variable improvements in symptomatology require further investigation of 5-HT-mediated pathology. Neurexins (Nrxns) are presynaptic cell adhesion molecules that maintain synapse function for proper neural circuit assembly. Given that aberrant Nrxn and 5-HT function independently contribute to signaling pathology and behavioral impairments, it is critical to understand how Nrxn-mediated 5-HT neurotransmission participates in pathological mechanisms underlying ASD. Using fluorescence in situ hybridization, I found that the three Nrxn genes (Nrxn1, Nrxn2, and Nrxn3) are differentially expressed in 5-HT neurons in the dorsal raphe nucleus (DRN) and median raphe nucleus which contain the primary source of 5-HT neurons in the brain. Our lab generated a mouse model with selective deletion of Nrxns in 5-HT neurons to investigate the function of Nrxns in 5-HT signaling. The loss of Nrxns at 5-HT release sites reduced 5-HT release in the DRN and hippocampus and altered 5-HT innervation in specific brain regions. The lack of 5-HTergic Nrxns also reduced sociability and increased depressive-like behavior in males. This mouse model provides mechanisms to shed new light on 5-HT neurotransmission in the generation of complex behaviors.