Publications by authors named "Thomas C Südhof"

335 Publications

Latrophilin GPCR signaling mediates synapse formation.

Elife 2021 Mar 1;10. Epub 2021 Mar 1.

Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, United States.

Neural circuit assembly in the brain requires precise establishment of synaptic connections, but the mechanisms of synapse assembly remain incompletely understood. Latrophilins are postsynaptic adhesion-GPCRs that engage in trans-synaptic complexes with presynaptic teneurins and FLRTs. In mouse CA1-region neurons, Latrophilin-2 and Latrophilin-3 are essential for formation of entorhinal-cortex-derived and Schaffer-collateral-derived synapses, respectively. However, it is unknown whether latrophilins function as GPCRs in synapse formation. Here, we show that Latrophilin-2 and Latrophilin-3 exhibit constitutive GPCR activity that increases cAMP levels, which was blocked by a mutation interfering with G-protein and arrestin interactions of GPCRs. The same mutation impaired the ability of Latrophilin-2 and Latrophilin-3 to rescue the synapse-loss phenotype in Latrophilin-2 and Latrophilin-3 knockout neurons . Our results suggest that Latrophilin-2 and Latrophilin-3 require GPCR signaling in synapse formation, indicating that latrophilins promote synapse formation in the hippocampus by activating a classical GPCR-signaling pathway.
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http://dx.doi.org/10.7554/eLife.65717DOI Listing
March 2021

Multiple signaling pathways are essential for synapse formation induced by synaptic adhesion molecules.

Proc Natl Acad Sci U S A 2021 Jan;118(3)

Department of Molecular and Cellular Physiology, Stanford University Medical School, Stanford, CA 94305;

Little is known about the cellular signals that organize synapse formation. To explore what signaling pathways may be involved, we employed heterologous synapse formation assays in which a synaptic adhesion molecule expressed in a nonneuronal cell induces pre- or postsynaptic specializations in cocultured neurons. We found that interfering pharmacologically with microtubules or actin filaments impaired heterologous synapse formation, whereas blocking protein synthesis had no effect. Unexpectedly, pharmacological inhibition of c-jun N-terminal kinases (JNKs), protein kinase-A (PKA), or AKT kinases also suppressed heterologous synapse formation, while inhibition of other tested signaling pathways-such as MAP kinases or protein kinase C-did not alter heterologous synapse formation. JNK and PKA inhibitors suppressed formation of both pre- and postsynaptic specializations, whereas AKT inhibitors impaired formation of post- but not presynaptic specializations. To independently test whether heterologous synapse formation depends on AKT signaling, we targeted PTEN, an enzyme that hydrolyzes phosphatidylinositol 3-phosphate and thereby prevents AKT kinase activation, to postsynaptic sites by fusing PTEN to Homer1. Targeting PTEN to postsynaptic specializations impaired heterologous postsynaptic synapse formation induced by presynaptic adhesion molecules, such as neurexins and additionally decreased excitatory synapse function in cultured neurons. Taken together, our results suggest that heterologous synapse formation is driven via a multifaceted and multistage kinase network, with diverse signals organizing pre- and postsynaptic specializations.
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http://dx.doi.org/10.1073/pnas.2000173118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7826368PMC
January 2021

A simple Ca-imaging approach to neural network analyses in cultured neurons.

J Neurosci Methods 2021 Feb 17;349:109041. Epub 2020 Dec 17.

Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA.

Background: Ca-imaging is a powerful tool to measure neuronal dynamics and network activity. To monitor network-level changes in cultured neurons, neuronal activity is often evoked by electrical or optogenetic stimulation and assessed using multi-electrode arrays or sophisticated imaging. Although such approaches allow detailed network analyses, multi-electrode arrays lack single-cell precision, whereas optical physiology generally requires advanced instrumentation that may not be universally available.

New Method: Here we developed a simple, stimulation-free protocol with associated Matlab algorithms that enables scalable analyses of spontaneous network activity in cultured human and mouse neurons. The approach allows analysis of the overall network activity and of single-neuron dynamics, and is amenable to screening purposes.

Results: We validated the new protocol by assessing human neurons with a heterozygous conditional deletion of Munc18-1, and mouse neurons with a homozygous conditional deletion of neurexins. The approach described enabled identification of differential changes in these mutant neurons, allowing quantifications of the synchronous firing rate at the network level and of the amplitude and frequency of Ca-spikes at the single-neuron level. These results demonstrate the utility of the approach.

Comparision With Existing Methods: Compared with current imaging platforms, our method is simple, scalable, accessible, and easy to implement. It enables quantification of more detailed parameters than multi-electrode arrays, but does not have the resolution and depth of more sophisticated yet labour-intensive methods, such as patch-clamp electrophysiology.

Conclusion: The method reported here is scalable for a rapid direct assessment of neuronal function in culture, and can be applied to both human and mouse neurons. Thus, the method can serve as a basis for phenotypical analysis of mutations and for drug discovery efforts.
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http://dx.doi.org/10.1016/j.jneumeth.2020.109041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7853247PMC
February 2021

Persistent transcriptional programmes are associated with remote memory.

Nature 2020 11 11;587(7834):437-442. Epub 2020 Nov 11.

Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA.

The role of gene expression during learning and in short-term memories has been studied extensively, but less is known about remote memories, which can persist for a lifetime. Here we used long-term contextual fear memory as a paradigm to probe the single-cell gene expression landscape that underlies remote memory storage in the medial prefrontal cortex. We found persistent activity-specific transcriptional alterations in diverse populations of neurons that lasted for weeks after fear learning. Out of a vast plasticity-coding space, we identified genes associated with membrane fusion that could have important roles in the maintenance of remote memory. Unexpectedly, astrocytes and microglia also acquired persistent gene expression signatures that were associated with remote memory, suggesting that they actively contribute to memory circuits. The discovery of gene expression programmes associated with remote memory engrams adds an important dimension of activity-dependent cellular states to existing brain taxonomy atlases and sheds light on the elusive mechanisms of remote memory storage.
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http://dx.doi.org/10.1038/s41586-020-2905-5DOI Listing
November 2020

SPARCL1 Promotes Excitatory But Not Inhibitory Synapse Formation and Function Independent of Neurexins and Neuroligins.

J Neurosci 2020 10 24;40(42):8088-8102. Epub 2020 Sep 24.

Department of Molecular and Cellular Physiology

Emerging evidence supports roles for secreted extracellular matrix proteins in boosting synaptogenesis, synaptic transmission, and synaptic plasticity. SPARCL1 (also known as Hevin), a secreted non-neuronal protein, was reported to increase synaptogenesis by simultaneously binding to presynaptic neurexin-1α and to postsynaptic neuroligin-1B, thereby catalyzing formation of trans-synaptic neurexin/neuroligin complexes. However, neurexins and neuroligins do not themselves mediate synaptogenesis, raising the question of how SPARCL1 enhances synapse formation by binding to these molecules. Moreover, it remained unclear whether SPARCL1 acts on all synapses containing neurexins and neuroligins or only on a subset of synapses, and whether it enhances synaptic transmission in addition to boosting synaptogenesis or induces silent synapses. To explore these questions, we examined the synaptic effects of SPARCL1 and their dependence on neurexins and neuroligins. Using mixed neuronal and glial cultures from neonatal mouse cortex of both sexes, we show that SPARCL1 selectively increases excitatory but not inhibitory synapse numbers, enhances excitatory but not inhibitory synaptic transmission, and augments NMDAR-mediated synaptic responses more than AMPAR-mediated synaptic responses. None of these effects were mediated by SPARCL1-binding to neurexins or neuroligins. Neurons from triple or from quadruple conditional KO mice that lacked all neurexins or all neuroligins were fully responsive to SPARCL1. Together, our results reveal that SPARCL1 selectively boosts excitatory but not inhibitory synaptogenesis and synaptic transmission by a novel mechanism that is independent of neurexins and neuroligins. Emerging evidence supports roles for extracellular matrix proteins in boosting synapse formation and function. Previous studies demonstrated that SPARCL1, a secreted non-neuronal protein, promotes synapse formation in rodent and human neurons. However, it remained unclear whether SPARCL1 acts on all or on only a subset of synapses, induces functional or largely inactive synapses, and generates synapses by bridging presynaptic neurexins and postsynaptic neuroligins. Here, we report that SPARCL1 selectively induces excitatory synapses, increases their efficacy, and enhances their NMDAR content. Moreover, using rigorous genetic manipulations, we show that SPARCL1 does not require neurexins and neuroligins for its activity. Thus, SPARCL1 selectively boosts excitatory synaptogenesis and synaptic transmission by a novel mechanism that is independent of neurexins and neuroligins.
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http://dx.doi.org/10.1523/JNEUROSCI.0454-20.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7574652PMC
October 2020

A Trio of Active Zone Proteins Comprised of RIM-BPs, RIMs, and Munc13s Governs Neurotransmitter Release.

Cell Rep 2020 08;32(5):107960

Institute of Neurophysiology, Charité - Universitätsmedizin, 10117 Berlin, Germany; NeuroCure Cluster of Excellence, Charité - Universitätsmedizin, 10117 Berlin, Germany. Electronic address:

At the presynaptic active zone, action-potential-triggered neurotransmitter release requires that fusion-competent synaptic vesicles are placed next to Ca channels. The active zone resident proteins RIM, RBP, and Munc13 are essential contributors for vesicle priming and Ca-channel recruitment. Although the individual contributions of these scaffolds have been extensively studied, their respective functions in neurotransmission are still incompletely understood. Here, we analyze the functional interactions of RIMs, RBPs, and Munc13s at the genetic, molecular, functional, and ultrastructural levels in a mammalian synapse. We find that RBP, together with Munc13, promotes vesicle priming at the expense of RBP's role in recruiting presynaptic Ca channels, suggesting that the support of RBP for vesicle priming and Ca-secretion coupling is mutually exclusive. Our results demonstrate that the functional interaction of RIM, RBP, and Munc13 is more profound than previously envisioned, acting as a functional trio that govern basic and short-term plasticity properties of neurotransmission.
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http://dx.doi.org/10.1016/j.celrep.2020.107960DOI Listing
August 2020

Deorphanizing FAM19A proteins as pan-neurexin ligands with an unusual biosynthetic binding mechanism.

J Cell Biol 2020 Sep;219(9)

Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA.

Neurexins are presynaptic adhesion molecules that organize synapses by binding to diverse trans-synaptic ligands, but how neurexins are regulated is incompletely understood. Here we identify FAM19A/TAFA proteins, "orphan" cytokines, as neurexin regulators that interact with all neurexins, except for neurexin-1γ, via an unusual mechanism. Specifically, we show that FAM19A1-A4 bind to the cysteine-loop domain of neurexins by forming intermolecular disulfide bonds during transport through the secretory pathway. FAM19A-binding required both the cysteines of the cysteine-loop domain and an adjacent sequence of neurexins. Genetic deletion of neurexins suppressed FAM19A1 expression, demonstrating that FAM19As physiologically interact with neurexins. In hippocampal cultures, expression of exogenous FAM19A1 decreased neurexin O-glycosylation and suppressed its heparan sulfate modification, suggesting that FAM19As regulate the post-translational modification of neurexins. Given the selective expression of FAM19As in specific subtypes of neurons and their activity-dependent regulation, these results suggest that FAM19As serve as cell type-specific regulators of neurexin modifications.
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http://dx.doi.org/10.1083/jcb.202004164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7480106PMC
September 2020

Dysfunction of parvalbumin neurons in the cerebellar nuclei produces an action tremor.

J Clin Invest 2020 10;130(10):5142-5156

Department of Molecular and Cellular Physiology and.

Essential tremor is a common brain disorder affecting millions of people, yet the neuronal mechanisms underlying this prevalent disease remain elusive. Here, we showed that conditional deletion of synaptotagmin-2, the fastest Ca2+ sensor for synaptic neurotransmitter release, from parvalbumin neurons in mice caused an action tremor syndrome resembling the core symptom of essential tremor patients. Combining brain region-specific and cell type-specific genetic manipulation methods, we found that deletion of synaptotagmin-2 from excitatory parvalbumin-positive neurons in cerebellar nuclei was sufficient to generate an action tremor. The synaptotagmin-2 deletion converted synchronous into asynchronous neurotransmitter release in projections from cerebellar nuclei neurons onto gigantocellular reticular nucleus neurons, which might produce an action tremor by causing signal oscillations during movement. The tremor was rescued by completely blocking synaptic transmission with tetanus toxin in cerebellar nuclei, which also reversed the tremor phenotype in the traditional harmaline-induced essential tremor model. Using a promising animal model for action tremor, our results thus characterized a synaptic circuit mechanism that may underlie the prevalent essential tremor disorder.
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http://dx.doi.org/10.1172/JCI135802DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7524475PMC
October 2020

A Synaptic Circuit Required for Acquisition but Not Recall of Social Transmission of Food Preference.

Neuron 2020 07 4;107(1):144-157.e4. Epub 2020 May 4.

Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA. Electronic address:

During social transmission of food preference (STFP), the combination of an olfactory sensory input with a social cue induces long-term memory of a food odor. How a social cue produces long-term learning of an olfactory input, however, remains unknown. Here we show that the neurons of the anterior olfactory nucleus (AON), which form abundant synaptic projections onto granule cells in the olfactory bulb (OB), express the synaptogenic molecule C1ql3. Deletion of C1ql3 in the dorsolateral AON impaired synaptic AON→OB connections and abolished acquisition, but not recall, of STFP memory without significantly affecting basal olfaction. Moreover, deletion in granule cells of the OB of Bai3, a postsynaptic GPCR that binds C1ql3, similarly suppressed synaptic transmission at AON→OB projections and abolished acquisition, but not recall, of STFP memory. Thus, synaptic AON→OB connections are selectively required for STFP memory acquisition and are formed by an essential interaction of presynaptic C1ql3 with postsynaptic Bai3.
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http://dx.doi.org/10.1016/j.neuron.2020.04.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7351611PMC
July 2020

Alternative splicing controls teneurin-latrophilin interaction and synapse specificity by a shape-shifting mechanism.

Nat Commun 2020 05 1;11(1):2140. Epub 2020 May 1.

Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.

The trans-synaptic interaction of the cell-adhesion molecules teneurins (TENs) with latrophilins (LPHNs/ADGRLs) promotes excitatory synapse formation when LPHNs simultaneously interact with FLRTs. Insertion of a short alternatively-spliced region within TENs abolishes the TEN-LPHN interaction and switches TEN function to specify inhibitory synapses. How alternative-splicing regulates TEN-LPHN interaction remains unclear. Here, we report the 2.9 Å resolution cryo-EM structure of the TEN2-LPHN3 complex, and describe the trimeric TEN2-LPHN3-FLRT3 complex. The structure reveals that the N-terminal lectin domain of LPHN3 binds to the TEN2 barrel at a site far away from the alternatively spliced region. Alternative-splicing regulates the TEN2-LPHN3 interaction by hindering access to the LPHN-binding surface rather than altering it. Strikingly, mutagenesis of the LPHN-binding surface of TEN2 abolishes the LPHN3 interaction and impairs excitatory but not inhibitory synapse formation. These results suggest that a multi-level coincident binding mechanism mediated by a cryptic adhesion complex between TENs and LPHNs regulates synapse specificity.
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http://dx.doi.org/10.1038/s41467-020-16029-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7195488PMC
May 2020

Pro-neuronal activity of Myod1 due to promiscuous binding to neuronal genes.

Nat Cell Biol 2020 04 30;22(4):401-411. Epub 2020 Mar 30.

Institute for Stem Cell Biology and Regenerative Medicine, Department of Pathology, Stanford University, Stanford, CA, USA.

The on-target pioneer factors Ascl1 and Myod1 are sequence-related but induce two developmentally unrelated lineages-that is, neuronal and muscle identities, respectively. It is unclear how these two basic helix-loop-helix (bHLH) factors mediate such fundamentally different outcomes. The chromatin binding of Ascl1 and Myod1 was surprisingly similar in fibroblasts, yet their transcriptional outputs were drastically different. We found that quantitative binding differences explained differential chromatin remodelling and gene activation. Although strong Ascl1 binding was exclusively associated with bHLH motifs, strong Myod1-binding sites were co-enriched with non-bHLH motifs, possibly explaining why Ascl1 is less context dependent. Finally, we observed that promiscuous binding of Myod1 to neuronal targets results in neuronal reprogramming when the muscle program is inhibited by Myt1l. Our findings suggest that chromatin access of on-target pioneer factors is primarily driven by the protein-DNA interaction, unlike ordinary context-dependent transcription factors, and that promiscuous transcription factor binding requires specific silencing mechanisms to ensure lineage fidelity.
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http://dx.doi.org/10.1038/s41556-020-0490-3DOI Listing
April 2020

Latrophilin-2 and latrophilin-3 are redundantly essential for parallel-fiber synapse function in cerebellum.

Elife 2020 03 23;9. Epub 2020 Mar 23.

Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States.

Latrophilin-2 (Lphn2) and latrophilin-3 (Lphn3) are adhesion GPCRs that serve as postsynaptic recognition molecules in CA1 pyramidal neurons of the hippocampus, where they are localized to distinct dendritic domains and are essential for different sets of excitatory synapses. Here, we studied Lphn2 and Lphn3 in the cerebellum. We show that latrophilins are abundantly and differentially expressed in the cerebellar cortex. Using conditional KO mice, we demonstrate that the Lphn2/3 double-deletion but not the deletion of Lphn2 or Lphn3 alone suppresses parallel-fiber synapses and reduces parallel-fiber synaptic transmission by ~50% without altering release probability. Climbing-fiber synapses, conversely, were unaffected. Even though ~50% of total cerebellar Lphn3 protein is expressed in Bergmann glia, Lphn3 deletion from Bergmann glia did not detectably impair excitatory or inhibitory synaptic transmission. Our studies demonstrate that Lphn2 and Lphn3 are selectively but redundantly required in Purkinje cells for parallel-fiber synapses.
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http://dx.doi.org/10.7554/eLife.54443DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7089768PMC
March 2020

Neurexins cluster Ca channels within the presynaptic active zone.

EMBO J 2020 04 5;39(7):e103208. Epub 2020 Mar 5.

Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA, USA.

To achieve ultrafast neurotransmission, neurons assemble synapses with highly organized presynaptic and postsynaptic nanomachines that are aligned by synaptic adhesion molecules. How functional assembly of presynaptic active zones is controlled via trans-synaptic interactions remains unknown. Here, we conditionally deleted all three neurexin adhesion molecules from presynaptic neurons of the calyx of Held in the mouse auditory system, a model synapse that allows precise biophysical analyses of synaptic properties. The pan-neurexin deletion had no effect on synapse development or the basic release machinery, but dramatically impaired fast neurotransmitter release. The overall properties of presynaptic calcium ion channels appeared normal, as reflected by the similar characteristics of calcium currents recorded at the nerve terminals. However, the pan-neurexin deletion significantly impaired the tight coupling of calcium influx to exocytosis, thereby suppressing neurotransmitter release. Furthermore, the pan-neurexin deletion reduced the function of calcium-activated BK potassium channels, whose activation depends on their tight association with presynaptic calcium channels. Together, these results suggest that neurexins perform a major function at the calyx synapse in coupling presynaptic calcium channels to release sites.
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http://dx.doi.org/10.15252/embj.2019103208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7110102PMC
April 2020

Evolution of the Autism-Associated Neuroligin-4 Gene Reveals Broad Erosion of Pseudoautosomal Regions in Rodents.

Mol Biol Evol 2020 05;37(5):1243-1258

Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA.

Variants in genes encoding synaptic adhesion proteins of the neuroligin family, most notably neuroligin-4, are a significant cause of autism spectrum disorders in humans. Although human neuroligin-4 is encoded by two genes, NLGN4X and NLGN4Y, that are localized on the X-specific and male-specific regions of the two sex chromosomes, the chromosomal localization and full genomic sequence of the mouse Nlgn4 gene remain elusive. Here, we analyzed the neuroligin-4 genes of numerous rodent species by direct sequencing and bioinformatics, generated complete drafts of multiple rodent neuroligin-4 genes, and examined their evolution. Surprisingly, we find that the murine Nlgn4 gene is localized to the pseudoautosomal region (PAR) of the sex chromosomes, different from its human orthologs. We show that the sequence differences between various neuroligin-4 proteins are restricted to hotspots in which rodent neuroligin-4 proteins contain short repetitive sequence insertions compared with neuroligin-4 proteins from other species, whereas all other protein sequences are highly conserved. Evolutionarily, these sequence insertions initiate in the clade eumuroidea of the infraorder myomorpha and are additionally associated with dramatic changes in noncoding sequences and gene size. Importantly, these changes are not exclusively restricted to neuroligin-4 genes but reflect major evolutionary changes that substantially altered or even deleted genes from the PARs of both sex chromosomes. Our results show that despite the fact that the PAR in rodents and the neuroligin-4 genes within the rodent PAR underwent massive evolutionary changes, neuroligin-4 proteins maintained a highly conserved core structure, consistent with a substantial evolutionary pressure preserving its physiological function.
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http://dx.doi.org/10.1093/molbev/msaa014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7182215PMC
May 2020

LAR receptor phospho-tyrosine phosphatases regulate NMDA-receptor responses.

Elife 2020 Jan 27;9. Epub 2020 Jan 27.

Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, United States.

LAR-type receptor phosphotyrosine-phosphatases (LAR-RPTPs) are presynaptic adhesion molecules that interact trans-synaptically with multitudinous postsynaptic adhesion molecules, including SliTrks, SALMs, and TrkC. Via these interactions, LAR-RPTPs are thought to function as synaptogenic wiring molecules that promote neural circuit formation by mediating the establishment of synapses. To test the synaptogenic functions of LAR-RPTPs, we conditionally deleted the genes encoding all three LAR-RPTPs, singly or in combination, in mice before synapse formation. Strikingly, deletion of LAR-RPTPs had no effect on synaptic connectivity in cultured neurons or in vivo, but impaired NMDA-receptor-mediated responses. Deletion of LAR-RPTPs decreased NMDA-receptor-mediated responses by a trans-synaptic mechanism. In cultured neurons, deletion of all LAR-RPTPs led to a reduction in synaptic NMDA-receptor EPSCs, without changing the subunit composition or the protein levels of NMDA-receptors. In vivo, deletion of all LAR-RPTPs in the hippocampus at birth also did not alter synaptic connectivity as measured via AMPA-receptor-mediated synaptic responses at Schaffer-collateral synapses monitored in juvenile mice, but again decreased NMDA-receptor mediated synaptic transmission. Thus, LAR-RPTPs are not essential for synapse formation, but control synapse properties by regulating postsynaptic NMDA-receptors via a trans-synaptic mechanism that likely involves binding to one or multiple postsynaptic ligands.
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http://dx.doi.org/10.7554/eLife.53406DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6984820PMC
January 2020

Continuous and Discrete Neuron Types of the Adult Murine Striatum.

Neuron 2020 02 5;105(4):688-699.e8. Epub 2019 Dec 5.

Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Department of Applied Physics, Stanford University, Stanford, CA 94305, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA. Electronic address:

The mammalian striatum is involved in many complex behaviors and yet is composed largely of a single neuron class: the spiny projection neuron (SPN). It is unclear to what extent the functional specialization of the striatum is due to the molecular specialization of SPN subtypes. We sought to define the molecular and anatomical diversity of adult SPNs using single-cell RNA sequencing (scRNA-seq) and quantitative RNA in situ hybridization (ISH). We computationally distinguished discrete versus continuous heterogeneity in scRNA-seq data and found that SPNs in the striatum can be classified into four major discrete types with no implied spatial relationship between them. Within these discrete types, we find continuous heterogeneity encoding spatial gradients of gene expression and defining anatomical location in a combinatorial mechanism. Our results suggest that neuronal circuitry has a substructure at far higher resolution than is typically interrogated, which is defined by the precise identity and location of a neuron.
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http://dx.doi.org/10.1016/j.neuron.2019.11.004DOI Listing
February 2020

Neuromodulator Signaling Bidirectionally Controls Vesicle Numbers in Human Synapses.

Cell 2019 10;179(2):498-513.e22

Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA.

Neuromodulators bind to pre- and postsynaptic G protein-coupled receptors (GPCRs), are able to quickly change intracellular cyclic AMP (cAMP) and Ca levels, and are thought to play important roles in neuropsychiatric and neurodegenerative diseases. Here, we discovered in human neurons an unanticipated presynaptic mechanism that acutely changes synaptic ultrastructure and regulates synaptic communication. Activation of neuromodulator receptors bidirectionally controlled synaptic vesicle numbers within nerve terminals. This control correlated with changes in the levels of cAMP-dependent protein kinase A-mediated phosphorylation of synapsin-1. Using a conditional deletion approach, we reveal that the neuromodulator-induced control of synaptic vesicle numbers was largely dependent on synapsin-1. We propose a mechanism whereby non-phosphorylated synapsin-1 "latches" synaptic vesicles to presynaptic clusters at the active zone. cAMP-dependent phosphorylation of synapsin-1 then removes the vesicles. cAMP-independent dephosphorylation of synapsin-1 in turn recruits vesicles. Synapsin-1 thereby bidirectionally regulates synaptic vesicle numbers and modifies presynaptic neurotransmitter release as an effector of neuromodulator signaling in human neurons.
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http://dx.doi.org/10.1016/j.cell.2019.09.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7159982PMC
October 2019

Structures of neurexophilin-neurexin complexes reveal a regulatory mechanism of alternative splicing.

EMBO J 2019 11 30;38(22):e101603. Epub 2019 Sep 30.

Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA.

Neurexins are presynaptic, cell-adhesion molecules that specify the functional properties of synapses via interactions with trans-synaptic ligands. Neurexins are extensively alternatively spliced at six canonical sites that regulate multifarious ligand interactions, but the structural mechanisms underlying alternative splicing-dependent neurexin regulation are largely unknown. Here, we determined high-resolution structures of the complex of neurexophilin-1 and the second laminin/neurexin/sex-hormone-binding globulin domain (LNS2) of neurexin-1 and examined how alternative splicing at splice site #2 (SS2) regulates the complex. Our data reveal a unique, extensive, neurexophilin-neurexin binding interface that extends the jelly-roll β-sandwich of LNS2 of neurexin-1 into neurexophilin-1. The SS2A insert of LNS2 augments this interface, increasing the binding affinity of LNS2 for neurexophilin-1. Taken together, our data reveal an unexpected architecture of neurexophilin-neurexin complexes that accounts for the modulation of binding by alternative splicing, which in turn regulates the competition of neurexophilin for neurexin binding with other ligands.
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http://dx.doi.org/10.15252/embj.2019101603DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6856630PMC
November 2019

A toolbox of nanobodies developed and validated for use as intrabodies and nanoscale immunolabels in mammalian brain neurons.

Elife 2019 09 30;8. Epub 2019 Sep 30.

Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, United States.

Nanobodies (nAbs) are small, minimal antibodies that have distinct attributes that make them uniquely suited for certain biomedical research, diagnostic and therapeutic applications. Prominent uses include as intracellular antibodies or intrabodies to bind and deliver cargo to specific proteins and/or subcellular sites within cells, and as nanoscale immunolabels for enhanced tissue penetration and improved spatial imaging resolution. Here, we report the generation and validation of nAbs against a set of proteins prominently expressed at specific subcellular sites in mammalian brain neurons. We describe a novel hierarchical validation pipeline to systematically evaluate nAbs isolated by phage display for effective and specific use as intrabodies and immunolabels in mammalian cells including brain neurons. These nAbs form part of a robust toolbox for targeting proteins with distinct and highly spatially-restricted subcellular localization in mammalian brain neurons, allowing for visualization and/or modulation of structure and function at those sites.
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http://dx.doi.org/10.7554/eLife.48750DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6785268PMC
September 2019

Differential Signaling Mediated by ApoE2, ApoE3, and ApoE4 in Human Neurons Parallels Alzheimer's Disease Risk.

J Neurosci 2019 09 22;39(37):7408-7427. Epub 2019 Jul 22.

Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, Stanford, California 94305,

In blood, apolipoprotein E (ApoE) is a component of circulating lipoproteins and mediates the clearance of these lipoproteins from blood by binding to ApoE receptors. Humans express three genetic ApoE variants, ApoE2, ApoE3, and ApoE4, which exhibit distinct ApoE receptor-binding properties and differentially affect Alzheimer's disease (AD), such that ApoE2 protects against, and ApoE4 predisposes to AD. In brain, ApoE-containing lipoproteins are secreted by activated astrocytes and microglia, but their functions and role in AD pathogenesis are largely unknown. Ample evidence suggests that ApoE4 induces microglial dysregulation and impedes Aβ clearance in AD, but the direct neuronal effects of ApoE variants are poorly studied. Extending previous studies, we here demonstrate that the three ApoE variants differentially activate multiple neuronal signaling pathways and regulate synaptogenesis. Specifically, using human neurons (male embryonic stem cell-derived) cultured in the absence of glia to exclude indirect glial mechanisms, we show that ApoE broadly stimulates signal transduction cascades. Among others, such stimulation enhances APP synthesis and synapse formation with an ApoE4>ApoE3>ApoE2 potency rank order, paralleling the relative risk for AD conferred by these ApoE variants. Unlike the previously described induction of transcription, however, ApoE-induced synaptogenesis involves CREB activation rather than cFos activation. We thus propose that in brain, ApoE acts as a glia-secreted signal that activates neuronal signaling pathways. The parallel potency rank order of ApoE4>ApoE3>ApoE2 in AD risk and neuronal signaling suggests that ApoE4 may in an apparent paradox promote AD pathogenesis by causing a chronic increase in signaling, possibly via enhancing APP expression. Humans express three genetic variants of apolipoprotein E (ApoE), ApoE2, ApoE3, and ApoE4. ApoE4 constitutes the most important genetic risk factor for Alzheimer's disease (AD), whereas ApoE2 protects against AD. Significant evidence suggests that ApoE4 impairs microglial function and impedes astrocytic Aβ clearance in brain, but the direct neuronal effects of ApoE are poorly understood, and the differences between ApoE variants in these effects are unclear. Here, we report that ApoE acts on neurons as a glia-secreted signaling molecule that, among others, enhances synapse formation. In activating neuronal signaling, the three ApoE variants exhibit a differential potency of ApoE4>ApoE3>ApoE2, which mirrors their relative effects on AD risk, suggesting that differential signaling by ApoE variants may contribute to AD pathogenesis.
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http://dx.doi.org/10.1523/JNEUROSCI.2994-18.2019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6759032PMC
September 2019

Synaptic neurexin-1 assembles into dynamically regulated active zone nanoclusters.

J Cell Biol 2019 08 1;218(8):2677-2698. Epub 2019 Jul 1.

Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA

Neurexins are well-characterized presynaptic cell adhesion molecules that engage multifarious postsynaptic ligands and organize diverse synapse properties. However, the precise synaptic localization of neurexins remains enigmatic. Using super-resolution microscopy, we demonstrate that neurexin-1 forms discrete nanoclusters at excitatory synapses, revealing a novel organizational feature of synaptic architecture. Synapses generally contain a single nanocluster that comprises more than four neurexin-1 molecules and that also includes neurexin-2 and/or neurexin-3 isoforms. Moreover, we find that neurexin-1 is physiologically cleaved by ADAM10 similar to its ligand neuroligin-1, with ∼4-6% of neurexin-1 and ∼2-3% of neuroligin-1 present in the adult brain as soluble ectodomain proteins. Blocking ADAM10-mediated neurexin-1 cleavage dramatically increased the synaptic neurexin-1 content, thereby elevating the percentage of Homer1(+) excitatory synapses containing neurexin-1 nanoclusters from 40-50% to ∼80%, and doubling the number of neurexin-1 molecules per nanocluster. Taken together, our results reveal an unexpected nanodomain organization of synapses in which neurexin-1 is assembled into discrete presynaptic nanoclusters that are dynamically regulated via ectodomain cleavage.
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http://dx.doi.org/10.1083/jcb.201812076DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6683742PMC
August 2019

Neuroligin-4 Regulates Excitatory Synaptic Transmission in Human Neurons.

Neuron 2019 08 27;103(4):617-626.e6. Epub 2019 Jun 27.

Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA. Electronic address:

The autism-associated synaptic-adhesion gene Neuroligin-4 (NLGN4) is poorly conserved evolutionarily, limiting conclusions from Nlgn4 mouse models for human cells. Here, we show that the cellular and subcellular expression of human and murine Neuroligin-4 differ, with human Neuroligin-4 primarily expressed in cerebral cortex and localized to excitatory synapses. Overexpression of NLGN4 in human embryonic stem cell-derived neurons resulted in an increase in excitatory synapse numbers but a remarkable decrease in synaptic strength. Human neurons carrying the syndromic autism mutation NLGN4-R704C also formed more excitatory synapses but with increased functional synaptic transmission due to a postsynaptic mechanism, while genetic loss of NLGN4 did not significantly affect synapses in the human neurons analyzed. Thus, the NLGN4-R704C mutation represents a change-of-function mutation. Our work reveals contrasting roles of NLGN4 in human and mouse neurons, suggesting that human evolution has impacted even fundamental cell biological processes generally assumed to be highly conserved.
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http://dx.doi.org/10.1016/j.neuron.2019.05.043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6706319PMC
August 2019

SynGO: An Evidence-Based, Expert-Curated Knowledge Base for the Synapse.

Neuron 2019 07 3;103(2):217-234.e4. Epub 2019 Jun 3.

Department of Functional Genomics, CNCR, VU University and UMC Amsterdam, 1081 HV Amsterdam, the Netherlands. Electronic address:

Synapses are fundamental information-processing units of the brain, and synaptic dysregulation is central to many brain disorders ("synaptopathies"). However, systematic annotation of synaptic genes and ontology of synaptic processes are currently lacking. We established SynGO, an interactive knowledge base that accumulates available research about synapse biology using Gene Ontology (GO) annotations to novel ontology terms: 87 synaptic locations and 179 synaptic processes. SynGO annotations are exclusively based on published, expert-curated evidence. Using 2,922 annotations for 1,112 genes, we show that synaptic genes are exceptionally well conserved and less tolerant to mutations than other genes. Many SynGO terms are significantly overrepresented among gene variations associated with intelligence, educational attainment, ADHD, autism, and bipolar disorder and among de novo variants associated with neurodevelopmental disorders, including schizophrenia. SynGO is a public, universal reference for synapse research and an online analysis platform for interpretation of large-scale -omics data (https://syngoportal.org and http://geneontology.org).
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http://dx.doi.org/10.1016/j.neuron.2019.05.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6764089PMC
July 2019

Ablation of All Synaptobrevin vSNAREs Blocks Evoked But Not Spontaneous Neurotransmitter Release at Neuromuscular Synapses.

J Neurosci 2019 07 3;39(31):6049-6066. Epub 2019 Jun 3.

Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas 75390, and

Synaptic transmission occurs when an action potential triggers neurotransmitter release via the fusion of synaptic vesicles with the presynaptic membrane, driven by the formation of SNARE complexes composed of the vesicular (v)-SNARE synaptobrevin and the target (t)-SNAREs Snap-25 and syntaxin-1. Neurotransmitters are also released spontaneously, independent of an action potential, through the fusion of synaptic vesicles with the presynaptic membrane. The major neuronal vSNAREs, synaptobrevin-1 and synaptobrevin-2, are expressed at the developing neuromuscular junction (NMJ) in mice, but their specific roles in NMJ formation and function remain unclear. Here, we examine the NMJs in mutant mouse embryos lacking either synaptobrevin 1 ( ) or synaptobrevin 2 (), and those lacking both (). We found that, compared with controls: (1) the number and size of NMJs was markedly increased in and mice, but not in mice; (2) synaptic vesicle density was markedly reduced in NMJs; and (3) evoked neurotransmission was markedly reduced in NMJs and completely abolished in NMJs. Surprisingly, however, spontaneous neurotransmission persists in the absence of both Syb1 and Syb2. Furthermore, spontaneous neurotransmission remains constant in NMJs despite changing Ca levels. These findings reveal an overlapping role for Syb1 and Syb2 (with Syb2 being dominant) in developing NMJs in mice. Moreover, because spontaneous release becomes Ca-insensitive in NMJs, our findings suggest that synaptobrevin-based SNARE complexes play a critical role in conferring Ca sensitivity during spontaneous release. Neurotransmitters can be released at synapses with (evoked) or without (spontaneous) the influence of action potentials. Whereas evoked neurotransmission requires Ca influx, those underlying the spontaneous neurotransmission may occur with or without Ca Our findings show that, in the absence neuronal vSNARE synaptobrevin-1 and synaptobrevin-2, evoked neurotransmission is completely abolished; however, spontaneous synaptic transmission not only persists but even increased. Furthermore, spontaneous synaptic transmission that is normally highly Ca-sensitive became Ca-independent upon deletion of vSNARE synaptobrevin-1 and synaptobrevin-2. These findings reveal distinct mechanisms for evoked and spontaneous neurotransmitter release. Moreover, these findings suggest that synaptobrevin-based SNARE complexes play critical roles in conferring Ca sensitivity during spontaneous neurotransmission at developing neuromuscular synapses in mice.
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http://dx.doi.org/10.1523/JNEUROSCI.0403-19.2019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6668203PMC
July 2019

Specific factors in blood from young but not old mice directly promote synapse formation and NMDA-receptor recruitment.

Proc Natl Acad Sci U S A 2019 06 3;116(25):12524-12533. Epub 2019 Jun 3.

Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305;

Aging drives a progressive decline in cognition and decreases synapse numbers and synaptic function in the brain, thereby increasing the risk for neurodegenerative disease. Pioneering studies showed that introduction of blood from young mice into aged mice reversed age-associated cognitive impairments and increased synaptic connectivity in brain, suggesting that young blood contains specific factors that remediate age-associated decreases in brain function. However, whether such factors in blood from young animals act directly on neurons to enhance synaptic connectivity, or whether they act by an indirect mechanism remains unknown. Moreover, which factors in young blood mediate cognitive improvements in old mice is incompletely understood. Here, we show that serum extracted from the blood of young but not old mice, when applied to neurons transdifferentiated from human embryonic stem cells, directly increased dendritic arborization, augmented synapse numbers, doubled dendritic spine-like structures, and elevated synaptic -methyl-d-aspartate (NMDA) receptors, thereby increasing synaptic connectivity. Mass spectrometry revealed that thrombospondin-4 (THBS4) and SPARC-like protein 1 (SPARCL1) were enriched in serum from young mice. Strikingly, recombinant THBS4 and SPARCL1 both increased dendritic arborization and doubled synapse numbers in cultured neurons. In addition, SPARCL1 but not THBS4 tripled NMDA receptor-mediated synaptic responses. Thus, at least two proteins enriched in young blood, THBS4 and SPARCL1, directly act on neurons as synaptogenic factors. These proteins may represent rejuvenation factors that enhance synaptic connectivity by increasing dendritic arborization, synapse formation, and synaptic transmission.
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http://dx.doi.org/10.1073/pnas.1902672116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6589664PMC
June 2019

Direct Reprogramming of Human Neurons Identifies MARCKSL1 as a Pathogenic Mediator of Valproic Acid-Induced Teratogenicity.

Cell Stem Cell 2019 07 30;25(1):103-119.e6. Epub 2019 May 30.

Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA. Electronic address:

Human pluripotent stem cells can be rapidly converted into functional neurons by ectopic expression of proneural transcription factors. Here we show that directly reprogrammed neurons, despite their rapid maturation kinetics, can model teratogenic mechanisms that specifically affect early neurodevelopment. We delineated distinct phases of in vitro maturation during reprogramming of human neurons and assessed the cellular phenotypes of valproic acid (VPA), a teratogenic drug. VPA exposure caused chronic impairment of dendritic morphology and functional properties of developing neurons, but not those of mature neurons. These pathogenic effects were associated with VPA-mediated inhibition of the histone deacetylase (HDAC) and glycogen synthase kinase-3 (GSK-3) pathways, which caused transcriptional downregulation of many genes, including MARCKSL1, an actin-stabilizing protein essential for dendritic morphogenesis and synapse maturation during early neurodevelopment. Our findings identify a developmentally restricted pathogenic mechanism of VPA and establish the use of reprogrammed neurons as an effective platform for modeling teratogenic pathways.
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http://dx.doi.org/10.1016/j.stem.2019.04.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6609489PMC
July 2019

Alternative Splicing of Presynaptic Neurexins Differentially Controls Postsynaptic NMDA and AMPA Receptor Responses.

Neuron 2019 06 17;102(5):993-1008.e5. Epub 2019 Apr 17.

Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA; Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA. Electronic address:

AMPA- and NMDA-type glutamate receptors mediate distinct postsynaptic signals that differ characteristically among synapses. How postsynaptic AMPA- and NMDA-receptor levels are regulated, however, remains unclear. Using newly generated conditional knockin mice that enable genetic control of neurexin alternative splicing, we show that in hippocampal synapses, alternative splicing of presynaptic neurexin-1 at splice site 4 (SS4) dramatically enhanced postsynaptic NMDA-receptor-mediated, but not AMPA-receptor-mediated, synaptic responses without altering synapse density. In contrast, alternative splicing of neurexin-3 at SS4 suppressed AMPA-receptor-mediated, but not NMDA-receptor-mediated, synaptic responses, while alternative splicing of neurexin-2 at SS4 had no effect on NMDA- or AMPA-receptor-mediated responses. Presynaptic overexpression of the neurexin-1β and neurexin-3β SS4+ splice variants, but not of their SS4- splice variants, replicated the respective SS4+ knockin phenotypes. Thus, different neurexins perform distinct nonoverlapping functions at hippocampal synapses that are independently regulated by alternative splicing. These functions transsynaptically control NMDA and AMPA receptors, thereby mediating presynaptic control of postsynaptic responses.
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http://dx.doi.org/10.1016/j.neuron.2019.03.032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6554035PMC
June 2019

Neuroligin-1 Signaling Controls LTP and NMDA Receptors by Distinct Molecular Pathways.

Neuron 2019 05 11;102(3):621-635.e3. Epub 2019 Mar 11.

Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA. Electronic address:

Neuroligins, postsynaptic cell adhesion molecules that are linked to neuropsychiatric disorders, are extensively studied, but fundamental questions about their functions remain. Using in vivo replacement strategies in quadruple conditional knockout mice of all neuroligins to avoid heterodimerization artifacts, we show, in hippocampal CA1 pyramidal neurons, that neuroligin-1 performs two key functions in excitatory synapses by distinct molecular mechanisms. N-methyl-D-aspartate (NMDA) receptor-dependent LTP requires trans-synaptic binding of postsynaptic neuroligin-1 to presynaptic β-neurexins but not the cytoplasmic sequences of neuroligins. In contrast, postsynaptic NMDA receptor (NMDAR)-mediated responses involve a neurexin-independent mechanism that requires the neuroligin-1 cytoplasmic sequences. Strikingly, deletion of neuroligins blocked the spine expansion associated with LTP, as monitored by two-photon imaging; this block involved a mechanism identical to that of the role of neuroligin-1 in NMDAR-dependent LTP. Our data suggest that neuroligin-1 performs two mechanistically distinct signaling functions and that neurolign-1-mediated trans-synaptic cell adhesion signaling critically regulates LTP.
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http://dx.doi.org/10.1016/j.neuron.2019.02.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6509009PMC
May 2019

Synaptotagmin-11 mediates a vesicle trafficking pathway that is essential for development and synaptic plasticity.

Genes Dev 2019 03 26;33(5-6):365-376. Epub 2019 Feb 26.

Department of Neuroscience, Scripps Research, La Jolla, California 92037, USA.

Synaptotagmin-11 (Syt11) is a Synaptotagmin isoform that lacks an apparent ability to bind calcium, phospholipids, or SNARE proteins. While human genetic studies have linked mutations in the gene to schizophrenia and Parkinson's disease, the localization or physiological role of Syt11 remain unclear. We found that in neurons, Syt11 resides on abundant vesicles that differ from synaptic vesicles and resemble trafficking endosomes. These vesicles recycle via the plasma membrane in an activity-dependent manner, but their exocytosis is slow and desynchronized. Constitutive knockout mice lacking Syt11 died shortly after birth, suggesting Syt11-mediated membrane transport is required for survival. In contrast, selective ablation of Syt11 in excitatory forebrain neurons using a conditional knockout did not affect life span but impaired synaptic plasticity and memory. Syt11-deficient neurons displayed normal secretion of fast neurotransmitters and peptides but exhibited a reduction of long-term synaptic potentiation. Hence, Syt11 is an essential component of a neuronal vesicular trafficking pathway that differs from the well-characterized synaptic vesicle trafficking pathway but is also essential for life.
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http://dx.doi.org/10.1101/gad.320077.118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6411015PMC
March 2019

Latrophilin GPCRs direct synapse specificity by coincident binding of FLRTs and teneurins.

Science 2019 02;363(6429)

Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA 94305, USA.

Bidirectional signaling by cell adhesion molecules is thought to mediate synapse formation, but the mechanisms involved remain elusive. We found that the adhesion G protein-coupled receptors latrophilin-2 and latrophilin-3 selectively direct formation of perforant-path and Schaffer-collateral synapses, respectively, to hippocampal CA1-region neurons. Latrophilin-3 binds to two transcellular ligands: fibronectin leucine-rich repeat transmembrane proteins (FLRTs) and teneurins. In transgenic mice in vivo, both binding activities were required for input-specific synapse formation, which suggests that coincident binding of both ligands is necessary for synapse formation. In cultured neurons in vitro, teneurin or FLRT alone did not induce excitatory synapse formation, whereas together they potently did so. Thus, postsynaptic latrophilins promote excitatory synapse formation by simultaneous binding of two unrelated presynaptic ligands, which is required for formation of synaptic inputs at specific dendritic localizations.
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http://dx.doi.org/10.1126/science.aav7969DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6636343PMC
February 2019