{"gene":"NLGN2","run_date":"2026-04-29T11:37:57","timeline":{"discoveries":[{"year":2017,"finding":"MDGA1 binds NLGN2 with nanomolar affinity through its Ig1-Ig2 domains, which sterically block the same neurexin-binding region on NLGN2, thereby competitively inhibiting formation of NLGN2-neurexin trans-synaptic bridges.","method":"Crystal structure of MDGA1 Ig1-Ig2 alone and in complex with NLGN2 dimer, site-directed mutagenesis confirming interaction interface, binding affinity measurements","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus mutagenesis validation in single rigorous study","pmids":["28641112"],"is_preprint":false},{"year":2011,"finding":"The NLGN2 R215H missense mutation causes retention of NLGN2 protein in the endoplasmic reticulum, preventing transport to the cell membrane and abolishing its ability to induce GABAergic synaptogenesis.","method":"Immunocytochemistry (subcellular localization), electrophysiological recordings of GABAergic synaptic currents in neuron coculture assay with mutant vs. wild-type NLGN2","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1-2 — direct functional assay with mechanistic explanation (ER retention), replicated in knock-in mouse model in subsequent study","pmids":["21551456"],"is_preprint":false},{"year":2016,"finding":"NLGN2 function at inhibitory synapses requires its extracellular domain (which confers inhibitory-synapse specificity) and two distinct cytoplasmic tail domains: one gephyrin-dependent mechanism disrupted by the autism-associated R705 mutation, and one gephyrin-independent mechanism reliant on a putative phosphorylation site at S714.","method":"Chimeric and point-mutant NLGN2 constructs expressed in rat CA1 neurons; whole-cell electrophysiology measuring inhibitory synaptic transmission","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 — structure-function dissection with electrophysiology and mutagenesis in multiple constructs","pmids":["27805570"],"is_preprint":false},{"year":2025,"finding":"The extracellular domain of NLGN2 determines its exclusive localization to inhibitory synapses (versus excitatory), while the cytoplasmic sequence of NLGN2—including its gephyrin-binding motif—is essential for its synaptic function at inhibitory synapses but dispensable for the excitatory-synapse function of NLGN1, revealing distinct intracellular mechanisms despite shared binding motifs.","method":"Chimeric Nlgn1-Nlgn2 constructs expressed in cultured hippocampal neurons lacking all neuroligins; whole-cell electrophysiology rescue experiments; synaptic localization imaging","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1 — comprehensive structure-function rescue analysis with electrophysiology and localization readouts","pmids":["39747663"],"is_preprint":false},{"year":2019,"finding":"Neuroligin-2, when internalized to endosomes, interacts directly with the PDZ domain of SNX27 via its PDZ-binding motif, enabling SNX27-mediated membrane recycling that maintains synaptic NLGN2 clusters, stabilizes synaptic GABAA receptors, and sustains inhibitory synapse strength.","method":"Co-immunoprecipitation, co-localization imaging, SNX27 knockdown/overexpression with measurement of inhibitory synapse markers and inhibitory synaptic currents","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — reciprocal interaction assay plus functional KD phenotype with multiple readouts","pmids":["31775031"],"is_preprint":false},{"year":2011,"finding":"Truncating mutations in NRXN2 fail to bind NLGN2 in cell binding assays and fail to promote synaptic differentiation in neuron coculture, establishing that the NRXN2–NLGN2 interaction is required for neurexin-mediated synaptogenic activity.","method":"Cell binding assays (NLGN2 binding to truncated NRXN2), neuron coculture synaptogenesis assay","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct binding and synaptogenesis assays, single study","pmids":["21424692"],"is_preprint":false},{"year":2016,"finding":"NLGN2 is localized to the majority of inhibitory (perisomatic) synapses in the basal amygdala; its deletion selectively impairs postsynaptic structure at perisomatic inhibitory synapses and reduces inhibitory synaptic transmission, leading to excessive activation of CaMKII-positive projection neurons under anxiogenic conditions.","method":"Immunohistochemistry, whole-cell electrophysiology of inhibitory transmission in Nlgn2 KO mice, cFOS activation assay with anxiogenic stimulus","journal":"Neuropharmacology","confidence":"High","confidence_rationale":"Tier 2 — direct localization, electrophysiology, and circuit activation assay with clean KO","pmids":["26142252"],"is_preprint":false},{"year":2015,"finding":"Conditional knockout of Nlgn2 in adult medial prefrontal cortex causes major reductions in synaptic inhibition (but not immediately—only after 6-7 weeks), impairs behavioral stimulation of immediate-early gene expression in mPFC, and produces parallel cognitive and social behavioral impairments, demonstrating that NLGN2 is required for continuous maintenance of inhibitory synapses in the adult mPFC.","method":"Conditional KO (cKO) mice with stereotaxic viral Cre delivery; electrophysiology, immunostaining, behavioral battery, immediate-early gene expression","journal":"Molecular psychiatry","confidence":"High","confidence_rationale":"Tier 2 — adult-restricted region-specific KO with electrophysiology and multiple behavioral readouts","pmids":["25824299"],"is_preprint":false},{"year":2018,"finding":"NLGN2 physically associates with the serotonin transporter (SERT) in mouse midbrain in a calcium-independent (cis) interaction; loss of NLGN2 reduces midbrain and hippocampal SERT expression and function, decreases GABAA receptor-mediated IPSCs, and increases 5-HT1A autoreceptor sensitivity in dorsal raphe neurons.","method":"Proteomic analysis of SERT complexes, reciprocal co-immunoprecipitation, Western blot, dual-color in situ hybridization, immunocytochemistry, electrophysiology in Nlgn2 null mice","journal":"Frontiers in synaptic neuroscience","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP confirmed interaction, multiple orthogonal functional readouts in KO","pmids":["26793096"],"is_preprint":false},{"year":2018,"finding":"NLGN2 R215H knock-in mice show a significant loss of NL2 protein in vivo, reduced GABAergic transmission, and impaired hippocampal activation, recapitulating schizophrenia-like behaviors, confirming that the single point mutation causes loss-of-function at inhibitory synapses in vivo.","method":"Transgenic knock-in mouse model; Western blot, electrophysiology, behavioral battery, immunostaining","journal":"Molecular brain","confidence":"High","confidence_rationale":"Tier 2 — in vivo knock-in model with electrophysiology and protein quantification, independently generated from prior cell-based study","pmids":["29859117"],"is_preprint":false},{"year":2018,"finding":"Deletion of IgSF9b normalizes anxiety-related behaviors in Nlgn2 KO mice through differential effects at inhibitory synapses in the basal versus centromedial amygdala, placing IgSF9b downstream of or in a parallel pathway to NLGN2 in amygdala inhibitory circuit regulation; local IgSF9b deletion in CeM of Nlgn2 KO mice produces anxiolysis, establishing an epistatic relationship.","method":"Genetic epistasis (double KO), local viral KD in CeM, electrophysiology, behavioral assays, in vivo neural activity recordings","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with electrophysiology and circuit-level recordings","pmids":["30573727"],"is_preprint":false},{"year":2018,"finding":"NLGN2 overexpression in hippocampal neurons increases membrane localization of GABAergic postsynaptic proteins gephyrin and GABAARγ2, and the presynaptic marker VGAT, and increases parvalbumin-positive synaptic boutons co-localized with gephyrin, without affecting glutamatergic synaptic markers, demonstrating NLGN2 selectively drives trans-synaptic enhancement of GABAergic synapses.","method":"AAV-mediated NLGN2 overexpression in mouse hippocampus; immunofluorescence quantification of pre- and postsynaptic GABAergic and glutamatergic markers, behavioral battery","journal":"Behavioural brain research","confidence":"Medium","confidence_rationale":"Tier 2 — direct protein overexpression with synaptic marker analysis, single study","pmids":["30605713"],"is_preprint":false},{"year":2018,"finding":"FMRP associates with Nlgn2 mRNA and suppresses its local synaptic translation; in Fmr1 KO mice, elevated NLGN2 mRNA translation occurs at synapses; additionally, NLGN2 protein levels at synapses are rapidly reduced by proteolytic cleavage following NMDA receptor stimulation.","method":"RNA immunoprecipitation (RIP) in synaptoneurosomes, synaptic translation assay, Western blot of synaptic fractions in Fmr1 KO mice, NMDA receptor stimulation cleavage assay","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 — RIP plus functional synaptic translation assay, single lab","pmids":["30056576"],"is_preprint":false},{"year":2019,"finding":"In iPSC-derived cortical interneurons from schizophrenia patients, NLGN2 levels are reduced; NLGN2 overexpression rescues synaptic puncta deficits, while NLGN2 knockdown in healthy neurons reduces synaptic puncta density, establishing NLGN2 as a causal regulator of GABAergic synaptic connectivity in human cortical interneurons.","method":"iPSC-derived interneuron model; NLGN2 overexpression and knockdown; immunostaining of synaptic puncta density, action potential recordings","journal":"Translational psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 — bidirectional manipulation (OE and KD) with synaptic readout in human-derived cells","pmids":["31780643"],"is_preprint":false},{"year":2023,"finding":"MDGA1 designer mutants that shift MDGA1 from compact to extended 3D conformations—without altering MDGA1-NLGN2 binding affinity in solution—nonetheless reduce cellular NLGN2 binding, decrease MDGA1's capacity to conceal NLGN2 from NRXN1β, and suppress NLGN2-mediated inhibitory presynaptic differentiation, demonstrating that the global 3D conformation of the MDGA1 ectodomain (not just the Ig1-Ig2 binding site) is required for its functional regulation of NLGN2.","method":"Designer mutagenesis at MDGA1 molecular elbows; negative-stain EM for conformation analysis; cell-binding assays; inhibitory synaptogenesis assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — structure + mutagenesis + functional assay in single study","pmids":["36889589"],"is_preprint":false},{"year":2024,"finding":"Loss of MDGA1 (but not heterozygous deletion of MDGA2) in hippocampal CA1 ameliorates the abnormal cytosolic gephyrin aggregation, the reduction in inhibitory synaptic transmission, and the anxiety behavior characterizing Nlgn2 KO mice; combined Nlgn2 and MDGA1 deletion causes an exacerbated layer-specific loss of gephyrin puncta, establishing a functional antagonism between MDGA1 and NLGN2 at inhibitory synapses.","method":"Genetic double-KO (Nlgn2 KO × MDGA1 KO); electrophysiology, immunostaining of gephyrin puncta, behavioral anxiety tests","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with electrophysiology and morphological readouts","pmids":["39284869"],"is_preprint":false},{"year":2025,"finding":"MDGA1 and NLGN2 selectively interact in the lateral habenula (LHb); germline MDGA1 KO or introduction of an Nlgn2 variant incapable of binding MDGA1 increases inhibitory synaptic transmission and GABAergic synapse density in the LHb and confers resistance to chronic stress-induced depressive behaviors, demonstrating that MDGA1-mediated suppression of NLGN2 limits GABAergic synapse formation and facilitates depression.","method":"Transgenic conditional KO/knockin mouse models with viral Cre; electrophysiology, immunostaining, behavioral depression tests (chronic restraint stress paradigm), chemogenetic LH stimulation","journal":"Theranostics","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic models with electrophysiology and behavioral epistasis","pmids":["39897557"],"is_preprint":false},{"year":2014,"finding":"α-Dystroglycan binds both LNS2 and LNS6 domains of α-Nrxn1 via LARGE-dependent glycans, and its binding at LNS2 sterically prevents NLGN2 binding at LNS6, revealing that αDAG and NLGN2 compete for the same presynaptic α-neurexin molecule, providing a mechanism for regulating inhibitory synapse identity.","method":"Site-directed mutagenesis of Nrxn1α binding domains; cell-based binding competition assays; glycan manipulation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — mutagenesis plus binding competition assays, single lab","pmids":["25157101"],"is_preprint":false},{"year":2013,"finding":"Intra-hippocampal administration of neurolide-2 (a synthetic peptide spanning the NLGN2 neurexin-binding sequence) reduces sociability and increases aggression in rats, functionally linking hippocampal NLGN2–neurexin interaction to social behavior regulation.","method":"Stereotaxic intra-hippocampal peptide injection (neurolide-2); behavioral tests (sociability, aggression); Western blot and immunohistochemistry confirming endogenous NLGN2 reduction with chronic stress","journal":"Neuropsychopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — direct peptide disruption of NLGN2-neurexin binding with behavioral readout, single study","pmids":["24213355"],"is_preprint":false},{"year":2016,"finding":"In hyperalgesic priming (a model of chronic pain), nlgn2 expression in the spinal dorsal horn increases via upregulation of the nlgn2A splice variant that promotes inhibitory synaptogenesis; disruption of nlgn2 function with neurolide-2 reverses the switch in GABAergic pharmacology polarity associated with chronic pain maintenance.","method":"Western blot and RT-PCR of nlgn2 splice variants; intra-spinal neurolide-2 peptide injection; behavioral pain assays","journal":"Pain","confidence":"Medium","confidence_rationale":"Tier 2 — molecular mechanism (splice variant) plus functional peptide disruption, single study","pmids":["26859820"],"is_preprint":false},{"year":2018,"finding":"NLGN2 knockdown in dopamine D1-positive NAc neurons promotes stress susceptibility and subordination, whereas NLGN2 knockdown in dopamine D2-positive NAc neurons mediates active defensive behavior, establishing a cell-type-specific role for NLGN2 in stress and depression-related circuitry.","method":"Cell-type-specific viral KD (Cre-dependent shRNA in D1-Cre and D2-Cre mice); chronic social defeat stress; behavioral battery","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific bidirectional manipulation with defined behavioral phenotype","pmids":["29339486"],"is_preprint":false},{"year":2024,"finding":"NLGN2 localizes to tight junctions in pancreatic acinar cells; loss of NLGN2 in pancreatic intraepithelial neoplasia disrupts the PALS1/PATJ polarity complex, thereby releasing YAP from contact inhibition and driving PanIN progression.","method":"Immunolocalization of NLGN2 in acinar cells and PanINs; co-immunoprecipitation of PALS1/PATJ complex; YAP activity assays; NLGN2 loss-of-function in PanIN model","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization plus co-IP showing complex formation and functional consequence, single study in non-neuronal context","pmids":["38413734"],"is_preprint":false},{"year":2019,"finding":"HIV-1 Tat protein induces astrocytes to release extracellular vesicles containing miR-7, which is taken up by neurons and downregulates neuronal NLGN2 expression, leading to synaptic alterations that are reversible by PDGF-CC pretreatment.","method":"Astrocyte-neuron co-culture; EV isolation and miR-7 quantification; neuronal NLGN2 knockdown measured by Western blot; synaptic marker imaging; PDGF-CC rescue","journal":"Journal of neuroimmune pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic pathway (miR-7 → NLGN2) with rescue experiment, single study","pmids":["31401755"],"is_preprint":false},{"year":2024,"finding":"IgSF21 and NLGN2 regulate GABAergic presynaptic differentiation via distinct subcellular compartments and distinct downstream signaling: both require JNK-mediated signaling for synaptogenic activity, but NLGN2 additionally requires CaMKII and Src kinase activity while IgSF21 does not.","method":"Pharmacological inhibition of JNK, CaMKII, and Src kinase during synaptogenesis assay; monitoring presynaptic differentiation induced by IgSF21 vs. NLGN2 in vitro","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — direct pathway dissection with pharmacological inhibitors and synaptogenesis readout","pmids":["38571813"],"is_preprint":false},{"year":2013,"finding":"Regulatory sequences in the 5' region and exon 1 of NLGN2 act as promoter elements with transcriptional activity that differs between neuronal and non-neuronal cell lines; two CpG-rich elements show distinct methylation and MeCP2 binding, identifying NLGN2 transcriptional regulation as dependent on and independent of MeCP2.","method":"Reporter gene assays in heterologous and neuronal cell lines; methylation analysis; MeCP2 binding assays","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — functional promoter dissection with reporter assays and binding studies, single study","pmids":["23875667"],"is_preprint":false},{"year":2026,"finding":"Nlgn2-neurexin adhesion is required for the consolidation (but not induction) of inhibitory long-term potentiation (iLTP) at both somatostatin and parvalbumin inputs onto hippocampal CA1 pyramidal cells; disruption of this interaction during a brief 10-min post-induction window blocks gephyrin clustering and NLGN2 recruitment to GABAergic synapses during iLTP.","method":"Whole-cell recordings in hippocampal slices; neurolide-2 peptide blocking of Nlgn2-neurexin binding; temporally controlled peptide application; optogenetics to isolate SST and PV inputs; immunostaining of gephyrin and NLGN2 clusters","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — acute peptide intervention with temporal control, electrophysiology, and structural readouts; multiple orthogonal approaches","pmids":["41802868"],"is_preprint":false},{"year":2022,"finding":"The extracellular domain of human NLGN2, determined by cryo-EM, forms a homodimer with a distinct protomer rotation compared to NLGN3, which may differentially affect NLGN2 interactions with MDGAs.","method":"Cryo-electron microscopy structure determination of human NLGN2 and NLGN3; structural comparison with NLGN2-MDGA1 complex","journal":"Frontiers in endocrinology","confidence":"Medium","confidence_rationale":"Tier 1 — cryo-EM structure, but functional validation of the structural difference is inferential only","pmids":["36479216"],"is_preprint":false},{"year":2026,"finding":"The extracellular domain (ECD) of NLGN2 exists in a concentration-dependent equilibrium between monomeric and dimeric forms, with NLGN2 having intermediate homodimerization affinity between NLGN3 (highest) and NLGN1 (lowest), as revealed by mass photometry.","method":"Mass photometry of recombinant human NLGN1, NLGN2, NLGN3 ECDs at nM concentrations; size exclusion chromatography-MALS as comparator","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1 — biophysical measurement of oligomerization equilibrium, single study without functional consequence tested","pmids":["42033941"],"is_preprint":false},{"year":2018,"finding":"In endothelial cells, NLGN2 co-localizes with collybistin (a CDC42 guanine nucleotide exchange factor also expressed in endothelial cells) and modulates Angiopoietin-2 release by regulating Weibel-Palade body exocytosis; NLGN2-null mice display immature vasculature with reduced pericyte coverage and reduced Tie2 phosphorylation.","method":"NLGN2 siRNA knockdown and overexpression in endothelial cells; co-immunoprecipitation with collybistin; measurement of Ang2 in conditioned medium; retina and tumor xenograft vascular analysis in Nlgn2-null mice","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP showing NLGN2-collybistin interaction plus functional KD/OE with mechanistic readout, single study in non-canonical context","pmids":["29709479"],"is_preprint":false}],"current_model":"NLGN2 is a postsynaptic cell-adhesion molecule that localizes exclusively to GABAergic inhibitory synapses, where its extracellular domain binds presynaptic neurexins (β-Nrxn1 and α-Nrxn1) to form trans-synaptic bridges that are competitively blocked by MDGA1; its cytoplasmic tail recruits gephyrin to scaffold GABAA receptors, sustains inhibitory synapse formation and maintenance (including activity-dependent iLTP consolidation), and is regulated post-translationally by SNX27-mediated endosomal recycling and NMDA-receptor-triggered proteolytic cleavage, while its mRNA is locally translated under FMRP control; loss-of-function disrupts inhibitory transmission in multiple brain circuits (amygdala, hippocampus, mPFC, NAc, lateral habenula), producing anxiety, cognitive impairment, and altered social behavior."},"narrative":{"teleology":[{"year":2011,"claim":"Establishing that NLGN2 requires surface delivery for synaptogenic function: the R215H missense variant causes ER retention, abolishing GABAergic synaptogenesis, and NRXN2 truncations that cannot bind NLGN2 similarly fail to induce synaptic differentiation, defining the neurexin–NLGN2 trans-synaptic interaction as necessary for inhibitory synapse formation.","evidence":"Immunocytochemistry and electrophysiology in neuron coculture with mutant NLGN2 (R215H) and truncated NRXN2 constructs","pmids":["21551456","21424692"],"confidence":"High","gaps":["Mechanism of ER quality control for NLGN2 folding mutants undefined","Whether other NLGN2 missense variants cause similar retention unknown"]},{"year":2013,"claim":"Identifying transcriptional regulation of NLGN2: promoter dissection revealed CpG-rich elements with cell-type-specific activity and MeCP2-dependent and -independent regulation, while hippocampal peptide disruption of NLGN2–neurexin binding showed that this interaction regulates social behavior.","evidence":"Reporter gene assays with NLGN2 promoter constructs and MeCP2 binding analysis; intra-hippocampal neurolide-2 peptide injection with behavioral readouts in rats","pmids":["23875667","24213355"],"confidence":"Medium","gaps":["Endogenous transcription factor occupancy at NLGN2 promoter not mapped","Peptide specificity for NLGN2 versus other neuroligins not fully established"]},{"year":2014,"claim":"Revealing competitive binding on presynaptic neurexins: α-dystroglycan and NLGN2 compete for binding to α-neurexin-1 at overlapping LNS domains, providing a mechanism by which presynaptic factors gate inhibitory synapse identity.","evidence":"Site-directed mutagenesis of Nrxn1α LNS domains with cell-based binding competition assays","pmids":["25157101"],"confidence":"Medium","gaps":["In vivo relevance of dystroglycan–NLGN2 competition at inhibitory synapses not tested","Whether competition is regulated by activity unknown"]},{"year":2015,"claim":"Demonstrating that NLGN2 is required for ongoing maintenance—not just initial formation—of inhibitory synapses in the adult brain: conditional KO in adult mPFC caused progressive (6–7 week) loss of synaptic inhibition and cognitive/social impairment.","evidence":"Adult conditional KO via stereotaxic viral Cre delivery; electrophysiology, immunostaining, and behavioral battery over weeks","pmids":["25824299"],"confidence":"High","gaps":["Molecular cascade linking NLGN2 loss to delayed synapse disassembly unknown","Whether maintenance role generalizes beyond mPFC not established at this time point"]},{"year":2016,"claim":"Dissecting the domain logic of NLGN2: the extracellular domain confers inhibitory-synapse specificity and localization, while two distinct cytoplasmic mechanisms—gephyrin-dependent (disrupted by R705C) and gephyrin-independent (requiring S714)—are both essential for inhibitory synaptic function; in the amygdala, NLGN2 localizes to perisomatic inhibitory synapses and its deletion causes disinhibition of projection neurons under anxiogenic conditions.","evidence":"Chimeric and point-mutant NLGN2 constructs with electrophysiology in rat CA1; Nlgn2 KO mouse amygdala electrophysiology and cFOS mapping; spinal cord splice-variant analysis","pmids":["27805570","26142252","26859820"],"confidence":"High","gaps":["Kinase responsible for S714 phosphorylation not identified","Whether gephyrin-dependent and -independent pathways converge on same downstream effectors unknown"]},{"year":2017,"claim":"Structural basis for MDGA1-mediated NLGN2 regulation resolved: MDGA1 Ig1-Ig2 domains bind the NLGN2 dimer at the neurexin-binding surface with nanomolar affinity, sterically blocking trans-synaptic bridge formation.","evidence":"Crystal structure of MDGA1 Ig1-Ig2 in complex with NLGN2 dimer; site-directed mutagenesis and binding affinity measurements","pmids":["28641112"],"confidence":"High","gaps":["Whether MDGA1 binding is dynamically regulated at synapses unknown","Structure of full-length MDGA1–NLGN2 complex not resolved"]},{"year":2018,"claim":"Multiple studies established circuit-level and post-translational regulation: NLGN2 loss in D1 versus D2 NAc neurons produces opposite stress phenotypes; NLGN2 associates with SERT in midbrain modulating serotonergic function; FMRP binds Nlgn2 mRNA controlling local synaptic translation; NMDA receptor activation triggers NLGN2 proteolytic cleavage; IgSF9b operates epistatically with NLGN2 in amygdala anxiety circuits; R215H knock-in mice recapitulate schizophrenia-like phenotypes.","evidence":"Cell-type-specific viral KD in D1/D2-Cre mice; reciprocal Co-IP of NLGN2–SERT; RNA immunoprecipitation for FMRP–Nlgn2 mRNA; NMDA stimulation cleavage assay; double-KO epistasis (Nlgn2×IgSF9b); R215H knock-in mouse electrophysiology and behavior","pmids":["29339486","26793096","30056576","30573727","29859117","30605713"],"confidence":"High","gaps":["Protease responsible for NMDA-triggered NLGN2 cleavage not identified","Molecular link between IgSF9b and NLGN2 pathway unclear","Whether SERT interaction is direct or scaffold-mediated at atomic level unresolved"]},{"year":2019,"claim":"Endosomal recycling and human disease relevance established: SNX27 binds the NLGN2 PDZ-binding motif to recycle internalized NLGN2 back to the synaptic surface, maintaining GABAA receptor clusters; in iPSC-derived human cortical interneurons from schizophrenia patients, reduced NLGN2 levels correlate with synaptic deficits that are rescued by NLGN2 overexpression.","evidence":"Co-IP and SNX27 KD with electrophysiology readout; iPSC-derived interneurons with bidirectional NLGN2 manipulation and synaptic puncta quantification","pmids":["31775031","31780643"],"confidence":"High","gaps":["Whether SNX27-NLGN2 recycling is activity-dependent not tested","Genetic causality of NLGN2 reduction in schizophrenia patient lines not established"]},{"year":2022,"claim":"Cryo-EM structure of the human NLGN2 extracellular domain revealed a homodimeric architecture with a distinct protomer rotation compared to NLGN3, suggesting structural basis for differential MDGA recognition.","evidence":"Cryo-EM structure determination of NLGN2 and NLGN3 ectodomains with structural comparison","pmids":["36479216"],"confidence":"Medium","gaps":["Functional consequence of distinct protomer rotation not experimentally tested","Full-length structure including transmembrane and cytoplasmic domains lacking"]},{"year":2023,"claim":"The global 3D conformation of the MDGA1 ectodomain—not just its binding interface—is required for functional suppression of NLGN2: extended MDGA1 conformations fail to conceal NLGN2 from neurexin despite retaining binding affinity in solution.","evidence":"MDGA1 elbow mutagenesis; negative-stain EM conformational analysis; cell-binding and synaptogenesis assays","pmids":["36889589"],"confidence":"High","gaps":["How MDGA1 conformation is regulated in vivo unknown","Whether other MDGA family members use similar conformational gating unresolved"]},{"year":2024,"claim":"Genetic epistasis confirmed functional antagonism between MDGA1 and NLGN2 in vivo: MDGA1 KO rescued gephyrin aggregation, inhibitory transmission deficits, and anxiety in Nlgn2 KO mice; NLGN2 also functions outside the nervous system at tight junctions in pancreatic acinar cells, where its loss disrupts the PALS1/PATJ polarity complex and activates YAP during neoplasia.","evidence":"Double-KO (Nlgn2×MDGA1) with electrophysiology and gephyrin imaging; NLGN2 immunolocalization and Co-IP of PALS1/PATJ in pancreatic tissue with YAP activity assays","pmids":["39284869","38413734","38571813"],"confidence":"High","gaps":["Whether MDGA1-NLGN2 antagonism operates at all inhibitory synapse subtypes untested","Mechanism of NLGN2 interaction with PALS1/PATJ at tight junctions not structurally resolved"]},{"year":2025,"claim":"Domain-swap experiments definitively established that the NLGN2 extracellular domain is both necessary and sufficient for inhibitory-synapse targeting, while its cytoplasmic tail (including gephyrin-binding motif) is uniquely required for inhibitory but not excitatory synaptic function; in the lateral habenula, disrupting MDGA1–NLGN2 binding increases inhibitory synapse density and confers stress resilience.","evidence":"Chimeric Nlgn1-Nlgn2 rescue in neuroligin-null neurons with electrophysiology; MDGA1 KO and Nlgn2 MDGA1-binding-deficient knock-in in LHb with electrophysiology and chronic stress behavioral paradigm","pmids":["39747663","39897557"],"confidence":"High","gaps":["Identity of the extracellular determinant within the NLGN2 ECD that specifies inhibitory targeting not mapped to specific residues","Whether LHb MDGA1-NLGN2 axis is therapeutically targetable unknown"]},{"year":2026,"claim":"NLGN2–neurexin adhesion is specifically required during a brief consolidation window (~10 min post-induction) for inhibitory long-term potentiation at both SST and PV inputs onto CA1 pyramidal cells, during which NLGN2 and gephyrin are recruited to potentiated synapses; biophysically, the NLGN2 ectodomain shows intermediate homodimerization affinity among neuroligins.","evidence":"Temporally controlled neurolide-2 peptide application during whole-cell recordings with optogenetic isolation of SST/PV inputs; mass photometry of recombinant NLGN2 ECD","pmids":["41802868","42033941"],"confidence":"High","gaps":["Signaling cascade linking neurexin binding to gephyrin recruitment during iLTP not identified","Whether dimerization equilibrium is regulated at synapses in vivo unknown"]},{"year":null,"claim":"Key unresolved questions include the identity of the protease mediating NMDA-triggered NLGN2 cleavage, the specific extracellular residues that confer inhibitory-synapse targeting, the structural basis of the NLGN2–gephyrin cytoplasmic interaction, and whether the non-neuronal functions (pancreatic polarity, vascular regulation) share molecular mechanisms with synaptic NLGN2 function.","evidence":"","pmids":[],"confidence":"Low","gaps":["Protease identity for activity-dependent NLGN2 cleavage unknown","No atomic-resolution structure of full-length NLGN2 including transmembrane and cytoplasmic domains","Relationship between neuronal and non-neuronal NLGN2 functions mechanistically unexplored"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[0,2,3,5,6,25]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[2,3,4,11]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,2,3,4,6,11]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[4]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[2,3,6,7,8,10,11,20,25]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[0,5,6,14,16,25]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[23,28]}],"complexes":["NLGN2–neurexin trans-synaptic complex","NLGN2–MDGA1 cis complex","NLGN2–gephyrin postsynaptic scaffold"],"partners":["NRXN1","NRXN2","MDGA1","GPHN","SNX27","SERT","FMRP","IGSF9B"],"other_free_text":[]},"mechanistic_narrative":"NLGN2 is a postsynaptic cell-adhesion molecule that organizes and maintains GABAergic inhibitory synapses by forming trans-synaptic complexes with presynaptic neurexins and recruiting the scaffolding protein gephyrin and GABAA receptors to postsynaptic sites. Its extracellular cholinesterase-like domain, which homodimerizes and binds both α- and β-neurexins, determines exclusive inhibitory-synapse localization and is competitively regulated by MDGA1, whose compact ectodomain sterically occludes the neurexin-binding surface of the NLGN2 dimer [PMID:28641112, PMID:39284869, PMID:39747663]. The cytoplasmic tail operates through a gephyrin-dependent mechanism (disrupted by the autism-associated R705C mutation) and a parallel gephyrin-independent pathway involving S714 phosphorylation, while surface levels are sustained by SNX27-mediated endosomal recycling and regulated by NMDA-receptor-triggered proteolytic cleavage and FMRP-dependent translational control of Nlgn2 mRNA [PMID:27805570, PMID:31775031, PMID:30056576]. Loss of NLGN2 function—whether by knockout, the schizophrenia-linked R215H mutation that causes ER retention, or peptide disruption of the neurexin interface—reduces inhibitory transmission across brain regions including hippocampus, amygdala, mPFC, and nucleus accumbens, producing anxiety, cognitive impairment, altered social behavior, and stress susceptibility [PMID:21551456, PMID:29859117, PMID:25824299, PMID:29339486, PMID:41802868]."},"prefetch_data":{"uniprot":{"accession":"Q8NFZ4","full_name":"Neuroligin-2","aliases":[],"length_aa":835,"mass_kda":90.8,"function":"Transmembrane scaffolding protein involved in cell-cell interactions via its interactions with neurexin family members. Mediates cell-cell interactions both in neurons and in other types of cells, such as Langerhans beta cells. Plays a role in synapse function and synaptic signal transmission, especially via gamma-aminobutyric acid receptors (GABA(A) receptors). Functions by recruiting and clustering synaptic proteins. Promotes clustering of postsynaptic GABRG2 and GPHN. Promotes clustering of postsynaptic LHFPL4 (By similarity). Modulates signaling by inhibitory synapses, and thereby plays a role in controlling the ratio of signaling by excitatory and inhibitory synapses and information processing. Required for normal signal amplitude from inhibitory synapses, but is not essential for normal signal frequency. May promote the initial formation of synapses, but is not essential for this. In vitro, triggers the de novo formation of presynaptic structures. Mediates cell-cell interactions between Langerhans beta cells and modulates insulin secretion (By similarity)","subcellular_location":"Cell membrane; Postsynaptic cell membrane; Presynaptic cell membrane; Cell projection, dendritic spine; Cell projection, dendrite; Synapse","url":"https://www.uniprot.org/uniprotkb/Q8NFZ4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NLGN2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NLGN2","total_profiled":1310},"omim":[{"mim_id":"612541","title":"NEUTROPENIA, SEVERE CONGENITAL, 4, AUTOSOMAL RECESSIVE; SCN4","url":"https://www.omim.org/entry/612541"},{"mim_id":"611045","title":"GLUCOSE-6-PHOSPHATASE, CATALYTIC SUBUNIT 3; G6PC3","url":"https://www.omim.org/entry/611045"},{"mim_id":"606479","title":"NEUROLIGIN 2; NLGN2","url":"https://www.omim.org/entry/606479"},{"mim_id":"600568","title":"NEUROLIGIN 1; NLGN1","url":"https://www.omim.org/entry/600568"},{"mim_id":"600567","title":"NEUREXIN III; NRXN3","url":"https://www.omim.org/entry/600567"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Mitochondria","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/NLGN2"},"hgnc":{"alias_symbol":["KIAA1366"],"prev_symbol":[]},"alphafold":{"accession":"Q8NFZ4","domains":[{"cath_id":"3.40.50.1820","chopping":"40-50_66-128_177-603","consensus_level":"medium","plddt":94.6922,"start":40,"end":603}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NFZ4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NFZ4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NFZ4-F1-predicted_aligned_error_v6.png","plddt_mean":77.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NLGN2","jax_strain_url":"https://www.jax.org/strain/search?query=NLGN2"},"sequence":{"accession":"Q8NFZ4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NFZ4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NFZ4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NFZ4"}},"corpus_meta":[{"pmid":"21424692","id":"PMC_21424692","title":"Truncating mutations in NRXN2 and NRXN1 in autism spectrum disorders and schizophrenia.","date":"2011","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21424692","citation_count":224,"is_preprint":false},{"pmid":"23393157","id":"PMC_23393157","title":"Rare exonic deletions implicate the synaptic organizer Gephyrin (GPHN) in risk for autism, schizophrenia and seizures.","date":"2013","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23393157","citation_count":119,"is_preprint":false},{"pmid":"16077734","id":"PMC_16077734","title":"Analysis of four neuroligin genes as candidates for autism.","date":"2005","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/16077734","citation_count":113,"is_preprint":false},{"pmid":"21551456","id":"PMC_21551456","title":"Identification and functional characterization of rare mutations of the neuroligin-2 gene (NLGN2) associated with schizophrenia.","date":"2011","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21551456","citation_count":106,"is_preprint":false},{"pmid":"22820233","id":"PMC_22820233","title":"Developmental delays and reduced pup ultrasonic vocalizations but normal sociability in mice lacking the postsynaptic cell adhesion protein neuroligin2.","date":"2012","source":"Behavioural brain research","url":"https://pubmed.ncbi.nlm.nih.gov/22820233","citation_count":102,"is_preprint":false},{"pmid":"25824299","id":"PMC_25824299","title":"Conditional neuroligin-2 knockout in adult medial prefrontal cortex links chronic changes in synaptic inhibition to cognitive impairments.","date":"2015","source":"Molecular psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/25824299","citation_count":95,"is_preprint":false},{"pmid":"19607885","id":"PMC_19607885","title":"Prenatal exposure to valproic acid leads to reduced expression of synaptic adhesion molecule neuroligin 3 in mice.","date":"2009","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/19607885","citation_count":81,"is_preprint":false},{"pmid":"32661233","id":"PMC_32661233","title":"Tauopathy in the young autistic brain: novel biomarker and therapeutic target.","date":"2020","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/32661233","citation_count":77,"is_preprint":false},{"pmid":"27865048","id":"PMC_27865048","title":"Neuroligin 2 nonsense variant associated with anxiety, autism, intellectual disability, hyperphagia, and obesity.","date":"2016","source":"American journal of medical genetics. 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affinity measurements\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus mutagenesis validation in single rigorous study\",\n      \"pmids\": [\"28641112\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The NLGN2 R215H missense mutation causes retention of NLGN2 protein in the endoplasmic reticulum, preventing transport to the cell membrane and abolishing its ability to induce GABAergic synaptogenesis.\",\n      \"method\": \"Immunocytochemistry (subcellular localization), electrophysiological recordings of GABAergic synaptic currents in neuron coculture assay with mutant vs. wild-type NLGN2\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct functional assay with mechanistic explanation (ER retention), replicated in knock-in mouse model in subsequent study\",\n      \"pmids\": [\"21551456\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NLGN2 function at inhibitory synapses requires its extracellular domain (which confers inhibitory-synapse specificity) and two distinct cytoplasmic tail domains: one gephyrin-dependent mechanism disrupted by the autism-associated R705 mutation, and one gephyrin-independent mechanism reliant on a putative phosphorylation site at S714.\",\n      \"method\": \"Chimeric and point-mutant NLGN2 constructs expressed in rat CA1 neurons; whole-cell electrophysiology measuring inhibitory synaptic transmission\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — structure-function dissection with electrophysiology and mutagenesis in multiple constructs\",\n      \"pmids\": [\"27805570\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The extracellular domain of NLGN2 determines its exclusive localization to inhibitory synapses (versus excitatory), while the cytoplasmic sequence of NLGN2—including its gephyrin-binding motif—is essential for its synaptic function at inhibitory synapses but dispensable for the excitatory-synapse function of NLGN1, revealing distinct intracellular mechanisms despite shared binding motifs.\",\n      \"method\": \"Chimeric Nlgn1-Nlgn2 constructs expressed in cultured hippocampal neurons lacking all neuroligins; whole-cell electrophysiology rescue experiments; synaptic localization imaging\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — comprehensive structure-function rescue analysis with electrophysiology and localization readouts\",\n      \"pmids\": [\"39747663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Neuroligin-2, when internalized to endosomes, interacts directly with the PDZ domain of SNX27 via its PDZ-binding motif, enabling SNX27-mediated membrane recycling that maintains synaptic NLGN2 clusters, stabilizes synaptic GABAA receptors, and sustains inhibitory synapse strength.\",\n      \"method\": \"Co-immunoprecipitation, co-localization imaging, SNX27 knockdown/overexpression with measurement of inhibitory synapse markers and inhibitory synaptic currents\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal interaction assay plus functional KD phenotype with multiple readouts\",\n      \"pmids\": [\"31775031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Truncating mutations in NRXN2 fail to bind NLGN2 in cell binding assays and fail to promote synaptic differentiation in neuron coculture, establishing that the NRXN2–NLGN2 interaction is required for neurexin-mediated synaptogenic activity.\",\n      \"method\": \"Cell binding assays (NLGN2 binding to truncated NRXN2), neuron coculture synaptogenesis assay\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct binding and synaptogenesis assays, single study\",\n      \"pmids\": [\"21424692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NLGN2 is localized to the majority of inhibitory (perisomatic) synapses in the basal amygdala; its deletion selectively impairs postsynaptic structure at perisomatic inhibitory synapses and reduces inhibitory synaptic transmission, leading to excessive activation of CaMKII-positive projection neurons under anxiogenic conditions.\",\n      \"method\": \"Immunohistochemistry, whole-cell electrophysiology of inhibitory transmission in Nlgn2 KO mice, cFOS activation assay with anxiogenic stimulus\",\n      \"journal\": \"Neuropharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization, electrophysiology, and circuit activation assay with clean KO\",\n      \"pmids\": [\"26142252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Conditional knockout of Nlgn2 in adult medial prefrontal cortex causes major reductions in synaptic inhibition (but not immediately—only after 6-7 weeks), impairs behavioral stimulation of immediate-early gene expression in mPFC, and produces parallel cognitive and social behavioral impairments, demonstrating that NLGN2 is required for continuous maintenance of inhibitory synapses in the adult mPFC.\",\n      \"method\": \"Conditional KO (cKO) mice with stereotaxic viral Cre delivery; electrophysiology, immunostaining, behavioral battery, immediate-early gene expression\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — adult-restricted region-specific KO with electrophysiology and multiple behavioral readouts\",\n      \"pmids\": [\"25824299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"NLGN2 physically associates with the serotonin transporter (SERT) in mouse midbrain in a calcium-independent (cis) interaction; loss of NLGN2 reduces midbrain and hippocampal SERT expression and function, decreases GABAA receptor-mediated IPSCs, and increases 5-HT1A autoreceptor sensitivity in dorsal raphe neurons.\",\n      \"method\": \"Proteomic analysis of SERT complexes, reciprocal co-immunoprecipitation, Western blot, dual-color in situ hybridization, immunocytochemistry, electrophysiology in Nlgn2 null mice\",\n      \"journal\": \"Frontiers in synaptic neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP confirmed interaction, multiple orthogonal functional readouts in KO\",\n      \"pmids\": [\"26793096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"NLGN2 R215H knock-in mice show a significant loss of NL2 protein in vivo, reduced GABAergic transmission, and impaired hippocampal activation, recapitulating schizophrenia-like behaviors, confirming that the single point mutation causes loss-of-function at inhibitory synapses in vivo.\",\n      \"method\": \"Transgenic knock-in mouse model; Western blot, electrophysiology, behavioral battery, immunostaining\",\n      \"journal\": \"Molecular brain\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knock-in model with electrophysiology and protein quantification, independently generated from prior cell-based study\",\n      \"pmids\": [\"29859117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Deletion of IgSF9b normalizes anxiety-related behaviors in Nlgn2 KO mice through differential effects at inhibitory synapses in the basal versus centromedial amygdala, placing IgSF9b downstream of or in a parallel pathway to NLGN2 in amygdala inhibitory circuit regulation; local IgSF9b deletion in CeM of Nlgn2 KO mice produces anxiolysis, establishing an epistatic relationship.\",\n      \"method\": \"Genetic epistasis (double KO), local viral KD in CeM, electrophysiology, behavioral assays, in vivo neural activity recordings\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with electrophysiology and circuit-level recordings\",\n      \"pmids\": [\"30573727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"NLGN2 overexpression in hippocampal neurons increases membrane localization of GABAergic postsynaptic proteins gephyrin and GABAARγ2, and the presynaptic marker VGAT, and increases parvalbumin-positive synaptic boutons co-localized with gephyrin, without affecting glutamatergic synaptic markers, demonstrating NLGN2 selectively drives trans-synaptic enhancement of GABAergic synapses.\",\n      \"method\": \"AAV-mediated NLGN2 overexpression in mouse hippocampus; immunofluorescence quantification of pre- and postsynaptic GABAergic and glutamatergic markers, behavioral battery\",\n      \"journal\": \"Behavioural brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct protein overexpression with synaptic marker analysis, single study\",\n      \"pmids\": [\"30605713\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"FMRP associates with Nlgn2 mRNA and suppresses its local synaptic translation; in Fmr1 KO mice, elevated NLGN2 mRNA translation occurs at synapses; additionally, NLGN2 protein levels at synapses are rapidly reduced by proteolytic cleavage following NMDA receptor stimulation.\",\n      \"method\": \"RNA immunoprecipitation (RIP) in synaptoneurosomes, synaptic translation assay, Western blot of synaptic fractions in Fmr1 KO mice, NMDA receptor stimulation cleavage assay\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — RIP plus functional synaptic translation assay, single lab\",\n      \"pmids\": [\"30056576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In iPSC-derived cortical interneurons from schizophrenia patients, NLGN2 levels are reduced; NLGN2 overexpression rescues synaptic puncta deficits, while NLGN2 knockdown in healthy neurons reduces synaptic puncta density, establishing NLGN2 as a causal regulator of GABAergic synaptic connectivity in human cortical interneurons.\",\n      \"method\": \"iPSC-derived interneuron model; NLGN2 overexpression and knockdown; immunostaining of synaptic puncta density, action potential recordings\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — bidirectional manipulation (OE and KD) with synaptic readout in human-derived cells\",\n      \"pmids\": [\"31780643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MDGA1 designer mutants that shift MDGA1 from compact to extended 3D conformations—without altering MDGA1-NLGN2 binding affinity in solution—nonetheless reduce cellular NLGN2 binding, decrease MDGA1's capacity to conceal NLGN2 from NRXN1β, and suppress NLGN2-mediated inhibitory presynaptic differentiation, demonstrating that the global 3D conformation of the MDGA1 ectodomain (not just the Ig1-Ig2 binding site) is required for its functional regulation of NLGN2.\",\n      \"method\": \"Designer mutagenesis at MDGA1 molecular elbows; negative-stain EM for conformation analysis; cell-binding assays; inhibitory synaptogenesis assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — structure + mutagenesis + functional assay in single study\",\n      \"pmids\": [\"36889589\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Loss of MDGA1 (but not heterozygous deletion of MDGA2) in hippocampal CA1 ameliorates the abnormal cytosolic gephyrin aggregation, the reduction in inhibitory synaptic transmission, and the anxiety behavior characterizing Nlgn2 KO mice; combined Nlgn2 and MDGA1 deletion causes an exacerbated layer-specific loss of gephyrin puncta, establishing a functional antagonism between MDGA1 and NLGN2 at inhibitory synapses.\",\n      \"method\": \"Genetic double-KO (Nlgn2 KO × MDGA1 KO); electrophysiology, immunostaining of gephyrin puncta, behavioral anxiety tests\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with electrophysiology and morphological readouts\",\n      \"pmids\": [\"39284869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MDGA1 and NLGN2 selectively interact in the lateral habenula (LHb); germline MDGA1 KO or introduction of an Nlgn2 variant incapable of binding MDGA1 increases inhibitory synaptic transmission and GABAergic synapse density in the LHb and confers resistance to chronic stress-induced depressive behaviors, demonstrating that MDGA1-mediated suppression of NLGN2 limits GABAergic synapse formation and facilitates depression.\",\n      \"method\": \"Transgenic conditional KO/knockin mouse models with viral Cre; electrophysiology, immunostaining, behavioral depression tests (chronic restraint stress paradigm), chemogenetic LH stimulation\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic models with electrophysiology and behavioral epistasis\",\n      \"pmids\": [\"39897557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"α-Dystroglycan binds both LNS2 and LNS6 domains of α-Nrxn1 via LARGE-dependent glycans, and its binding at LNS2 sterically prevents NLGN2 binding at LNS6, revealing that αDAG and NLGN2 compete for the same presynaptic α-neurexin molecule, providing a mechanism for regulating inhibitory synapse identity.\",\n      \"method\": \"Site-directed mutagenesis of Nrxn1α binding domains; cell-based binding competition assays; glycan manipulation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis plus binding competition assays, single lab\",\n      \"pmids\": [\"25157101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Intra-hippocampal administration of neurolide-2 (a synthetic peptide spanning the NLGN2 neurexin-binding sequence) reduces sociability and increases aggression in rats, functionally linking hippocampal NLGN2–neurexin interaction to social behavior regulation.\",\n      \"method\": \"Stereotaxic intra-hippocampal peptide injection (neurolide-2); behavioral tests (sociability, aggression); Western blot and immunohistochemistry confirming endogenous NLGN2 reduction with chronic stress\",\n      \"journal\": \"Neuropsychopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct peptide disruption of NLGN2-neurexin binding with behavioral readout, single study\",\n      \"pmids\": [\"24213355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In hyperalgesic priming (a model of chronic pain), nlgn2 expression in the spinal dorsal horn increases via upregulation of the nlgn2A splice variant that promotes inhibitory synaptogenesis; disruption of nlgn2 function with neurolide-2 reverses the switch in GABAergic pharmacology polarity associated with chronic pain maintenance.\",\n      \"method\": \"Western blot and RT-PCR of nlgn2 splice variants; intra-spinal neurolide-2 peptide injection; behavioral pain assays\",\n      \"journal\": \"Pain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — molecular mechanism (splice variant) plus functional peptide disruption, single study\",\n      \"pmids\": [\"26859820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"NLGN2 knockdown in dopamine D1-positive NAc neurons promotes stress susceptibility and subordination, whereas NLGN2 knockdown in dopamine D2-positive NAc neurons mediates active defensive behavior, establishing a cell-type-specific role for NLGN2 in stress and depression-related circuitry.\",\n      \"method\": \"Cell-type-specific viral KD (Cre-dependent shRNA in D1-Cre and D2-Cre mice); chronic social defeat stress; behavioral battery\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific bidirectional manipulation with defined behavioral phenotype\",\n      \"pmids\": [\"29339486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NLGN2 localizes to tight junctions in pancreatic acinar cells; loss of NLGN2 in pancreatic intraepithelial neoplasia disrupts the PALS1/PATJ polarity complex, thereby releasing YAP from contact inhibition and driving PanIN progression.\",\n      \"method\": \"Immunolocalization of NLGN2 in acinar cells and PanINs; co-immunoprecipitation of PALS1/PATJ complex; YAP activity assays; NLGN2 loss-of-function in PanIN model\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization plus co-IP showing complex formation and functional consequence, single study in non-neuronal context\",\n      \"pmids\": [\"38413734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HIV-1 Tat protein induces astrocytes to release extracellular vesicles containing miR-7, which is taken up by neurons and downregulates neuronal NLGN2 expression, leading to synaptic alterations that are reversible by PDGF-CC pretreatment.\",\n      \"method\": \"Astrocyte-neuron co-culture; EV isolation and miR-7 quantification; neuronal NLGN2 knockdown measured by Western blot; synaptic marker imaging; PDGF-CC rescue\",\n      \"journal\": \"Journal of neuroimmune pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic pathway (miR-7 → NLGN2) with rescue experiment, single study\",\n      \"pmids\": [\"31401755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"IgSF21 and NLGN2 regulate GABAergic presynaptic differentiation via distinct subcellular compartments and distinct downstream signaling: both require JNK-mediated signaling for synaptogenic activity, but NLGN2 additionally requires CaMKII and Src kinase activity while IgSF21 does not.\",\n      \"method\": \"Pharmacological inhibition of JNK, CaMKII, and Src kinase during synaptogenesis assay; monitoring presynaptic differentiation induced by IgSF21 vs. NLGN2 in vitro\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct pathway dissection with pharmacological inhibitors and synaptogenesis readout\",\n      \"pmids\": [\"38571813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Regulatory sequences in the 5' region and exon 1 of NLGN2 act as promoter elements with transcriptional activity that differs between neuronal and non-neuronal cell lines; two CpG-rich elements show distinct methylation and MeCP2 binding, identifying NLGN2 transcriptional regulation as dependent on and independent of MeCP2.\",\n      \"method\": \"Reporter gene assays in heterologous and neuronal cell lines; methylation analysis; MeCP2 binding assays\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional promoter dissection with reporter assays and binding studies, single study\",\n      \"pmids\": [\"23875667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Nlgn2-neurexin adhesion is required for the consolidation (but not induction) of inhibitory long-term potentiation (iLTP) at both somatostatin and parvalbumin inputs onto hippocampal CA1 pyramidal cells; disruption of this interaction during a brief 10-min post-induction window blocks gephyrin clustering and NLGN2 recruitment to GABAergic synapses during iLTP.\",\n      \"method\": \"Whole-cell recordings in hippocampal slices; neurolide-2 peptide blocking of Nlgn2-neurexin binding; temporally controlled peptide application; optogenetics to isolate SST and PV inputs; immunostaining of gephyrin and NLGN2 clusters\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — acute peptide intervention with temporal control, electrophysiology, and structural readouts; multiple orthogonal approaches\",\n      \"pmids\": [\"41802868\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The extracellular domain of human NLGN2, determined by cryo-EM, forms a homodimer with a distinct protomer rotation compared to NLGN3, which may differentially affect NLGN2 interactions with MDGAs.\",\n      \"method\": \"Cryo-electron microscopy structure determination of human NLGN2 and NLGN3; structural comparison with NLGN2-MDGA1 complex\",\n      \"journal\": \"Frontiers in endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure, but functional validation of the structural difference is inferential only\",\n      \"pmids\": [\"36479216\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"The extracellular domain (ECD) of NLGN2 exists in a concentration-dependent equilibrium between monomeric and dimeric forms, with NLGN2 having intermediate homodimerization affinity between NLGN3 (highest) and NLGN1 (lowest), as revealed by mass photometry.\",\n      \"method\": \"Mass photometry of recombinant human NLGN1, NLGN2, NLGN3 ECDs at nM concentrations; size exclusion chromatography-MALS as comparator\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — biophysical measurement of oligomerization equilibrium, single study without functional consequence tested\",\n      \"pmids\": [\"42033941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In endothelial cells, NLGN2 co-localizes with collybistin (a CDC42 guanine nucleotide exchange factor also expressed in endothelial cells) and modulates Angiopoietin-2 release by regulating Weibel-Palade body exocytosis; NLGN2-null mice display immature vasculature with reduced pericyte coverage and reduced Tie2 phosphorylation.\",\n      \"method\": \"NLGN2 siRNA knockdown and overexpression in endothelial cells; co-immunoprecipitation with collybistin; measurement of Ang2 in conditioned medium; retina and tumor xenograft vascular analysis in Nlgn2-null mice\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP showing NLGN2-collybistin interaction plus functional KD/OE with mechanistic readout, single study in non-canonical context\",\n      \"pmids\": [\"29709479\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NLGN2 is a postsynaptic cell-adhesion molecule that localizes exclusively to GABAergic inhibitory synapses, where its extracellular domain binds presynaptic neurexins (β-Nrxn1 and α-Nrxn1) to form trans-synaptic bridges that are competitively blocked by MDGA1; its cytoplasmic tail recruits gephyrin to scaffold GABAA receptors, sustains inhibitory synapse formation and maintenance (including activity-dependent iLTP consolidation), and is regulated post-translationally by SNX27-mediated endosomal recycling and NMDA-receptor-triggered proteolytic cleavage, while its mRNA is locally translated under FMRP control; loss-of-function disrupts inhibitory transmission in multiple brain circuits (amygdala, hippocampus, mPFC, NAc, lateral habenula), producing anxiety, cognitive impairment, and altered social behavior.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NLGN2 is a postsynaptic cell-adhesion molecule that organizes and maintains GABAergic inhibitory synapses by forming trans-synaptic complexes with presynaptic neurexins and recruiting the scaffolding protein gephyrin and GABAA receptors to postsynaptic sites. Its extracellular cholinesterase-like domain, which homodimerizes and binds both α- and β-neurexins, determines exclusive inhibitory-synapse localization and is competitively regulated by MDGA1, whose compact ectodomain sterically occludes the neurexin-binding surface of the NLGN2 dimer [PMID:28641112, PMID:39284869, PMID:39747663]. The cytoplasmic tail operates through a gephyrin-dependent mechanism (disrupted by the autism-associated R705C mutation) and a parallel gephyrin-independent pathway involving S714 phosphorylation, while surface levels are sustained by SNX27-mediated endosomal recycling and regulated by NMDA-receptor-triggered proteolytic cleavage and FMRP-dependent translational control of Nlgn2 mRNA [PMID:27805570, PMID:31775031, PMID:30056576]. Loss of NLGN2 function—whether by knockout, the schizophrenia-linked R215H mutation that causes ER retention, or peptide disruption of the neurexin interface—reduces inhibitory transmission across brain regions including hippocampus, amygdala, mPFC, and nucleus accumbens, producing anxiety, cognitive impairment, altered social behavior, and stress susceptibility [PMID:21551456, PMID:29859117, PMID:25824299, PMID:29339486, PMID:41802868].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Establishing that NLGN2 requires surface delivery for synaptogenic function: the R215H missense variant causes ER retention, abolishing GABAergic synaptogenesis, and NRXN2 truncations that cannot bind NLGN2 similarly fail to induce synaptic differentiation, defining the neurexin–NLGN2 trans-synaptic interaction as necessary for inhibitory synapse formation.\",\n      \"evidence\": \"Immunocytochemistry and electrophysiology in neuron coculture with mutant NLGN2 (R215H) and truncated NRXN2 constructs\",\n      \"pmids\": [\"21551456\", \"21424692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of ER quality control for NLGN2 folding mutants undefined\", \"Whether other NLGN2 missense variants cause similar retention unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identifying transcriptional regulation of NLGN2: promoter dissection revealed CpG-rich elements with cell-type-specific activity and MeCP2-dependent and -independent regulation, while hippocampal peptide disruption of NLGN2–neurexin binding showed that this interaction regulates social behavior.\",\n      \"evidence\": \"Reporter gene assays with NLGN2 promoter constructs and MeCP2 binding analysis; intra-hippocampal neurolide-2 peptide injection with behavioral readouts in rats\",\n      \"pmids\": [\"23875667\", \"24213355\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous transcription factor occupancy at NLGN2 promoter not mapped\", \"Peptide specificity for NLGN2 versus other neuroligins not fully established\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealing competitive binding on presynaptic neurexins: α-dystroglycan and NLGN2 compete for binding to α-neurexin-1 at overlapping LNS domains, providing a mechanism by which presynaptic factors gate inhibitory synapse identity.\",\n      \"evidence\": \"Site-directed mutagenesis of Nrxn1α LNS domains with cell-based binding competition assays\",\n      \"pmids\": [\"25157101\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of dystroglycan–NLGN2 competition at inhibitory synapses not tested\", \"Whether competition is regulated by activity unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrating that NLGN2 is required for ongoing maintenance—not just initial formation—of inhibitory synapses in the adult brain: conditional KO in adult mPFC caused progressive (6–7 week) loss of synaptic inhibition and cognitive/social impairment.\",\n      \"evidence\": \"Adult conditional KO via stereotaxic viral Cre delivery; electrophysiology, immunostaining, and behavioral battery over weeks\",\n      \"pmids\": [\"25824299\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular cascade linking NLGN2 loss to delayed synapse disassembly unknown\", \"Whether maintenance role generalizes beyond mPFC not established at this time point\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Dissecting the domain logic of NLGN2: the extracellular domain confers inhibitory-synapse specificity and localization, while two distinct cytoplasmic mechanisms—gephyrin-dependent (disrupted by R705C) and gephyrin-independent (requiring S714)—are both essential for inhibitory synaptic function; in the amygdala, NLGN2 localizes to perisomatic inhibitory synapses and its deletion causes disinhibition of projection neurons under anxiogenic conditions.\",\n      \"evidence\": \"Chimeric and point-mutant NLGN2 constructs with electrophysiology in rat CA1; Nlgn2 KO mouse amygdala electrophysiology and cFOS mapping; spinal cord splice-variant analysis\",\n      \"pmids\": [\"27805570\", \"26142252\", \"26859820\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for S714 phosphorylation not identified\", \"Whether gephyrin-dependent and -independent pathways converge on same downstream effectors unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Structural basis for MDGA1-mediated NLGN2 regulation resolved: MDGA1 Ig1-Ig2 domains bind the NLGN2 dimer at the neurexin-binding surface with nanomolar affinity, sterically blocking trans-synaptic bridge formation.\",\n      \"evidence\": \"Crystal structure of MDGA1 Ig1-Ig2 in complex with NLGN2 dimer; site-directed mutagenesis and binding affinity measurements\",\n      \"pmids\": [\"28641112\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MDGA1 binding is dynamically regulated at synapses unknown\", \"Structure of full-length MDGA1–NLGN2 complex not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Multiple studies established circuit-level and post-translational regulation: NLGN2 loss in D1 versus D2 NAc neurons produces opposite stress phenotypes; NLGN2 associates with SERT in midbrain modulating serotonergic function; FMRP binds Nlgn2 mRNA controlling local synaptic translation; NMDA receptor activation triggers NLGN2 proteolytic cleavage; IgSF9b operates epistatically with NLGN2 in amygdala anxiety circuits; R215H knock-in mice recapitulate schizophrenia-like phenotypes.\",\n      \"evidence\": \"Cell-type-specific viral KD in D1/D2-Cre mice; reciprocal Co-IP of NLGN2–SERT; RNA immunoprecipitation for FMRP–Nlgn2 mRNA; NMDA stimulation cleavage assay; double-KO epistasis (Nlgn2×IgSF9b); R215H knock-in mouse electrophysiology and behavior\",\n      \"pmids\": [\"29339486\", \"26793096\", \"30056576\", \"30573727\", \"29859117\", \"30605713\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Protease responsible for NMDA-triggered NLGN2 cleavage not identified\", \"Molecular link between IgSF9b and NLGN2 pathway unclear\", \"Whether SERT interaction is direct or scaffold-mediated at atomic level unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Endosomal recycling and human disease relevance established: SNX27 binds the NLGN2 PDZ-binding motif to recycle internalized NLGN2 back to the synaptic surface, maintaining GABAA receptor clusters; in iPSC-derived human cortical interneurons from schizophrenia patients, reduced NLGN2 levels correlate with synaptic deficits that are rescued by NLGN2 overexpression.\",\n      \"evidence\": \"Co-IP and SNX27 KD with electrophysiology readout; iPSC-derived interneurons with bidirectional NLGN2 manipulation and synaptic puncta quantification\",\n      \"pmids\": [\"31775031\", \"31780643\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SNX27-NLGN2 recycling is activity-dependent not tested\", \"Genetic causality of NLGN2 reduction in schizophrenia patient lines not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Cryo-EM structure of the human NLGN2 extracellular domain revealed a homodimeric architecture with a distinct protomer rotation compared to NLGN3, suggesting structural basis for differential MDGA recognition.\",\n      \"evidence\": \"Cryo-EM structure determination of NLGN2 and NLGN3 ectodomains with structural comparison\",\n      \"pmids\": [\"36479216\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of distinct protomer rotation not experimentally tested\", \"Full-length structure including transmembrane and cytoplasmic domains lacking\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"The global 3D conformation of the MDGA1 ectodomain—not just its binding interface—is required for functional suppression of NLGN2: extended MDGA1 conformations fail to conceal NLGN2 from neurexin despite retaining binding affinity in solution.\",\n      \"evidence\": \"MDGA1 elbow mutagenesis; negative-stain EM conformational analysis; cell-binding and synaptogenesis assays\",\n      \"pmids\": [\"36889589\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How MDGA1 conformation is regulated in vivo unknown\", \"Whether other MDGA family members use similar conformational gating unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Genetic epistasis confirmed functional antagonism between MDGA1 and NLGN2 in vivo: MDGA1 KO rescued gephyrin aggregation, inhibitory transmission deficits, and anxiety in Nlgn2 KO mice; NLGN2 also functions outside the nervous system at tight junctions in pancreatic acinar cells, where its loss disrupts the PALS1/PATJ polarity complex and activates YAP during neoplasia.\",\n      \"evidence\": \"Double-KO (Nlgn2×MDGA1) with electrophysiology and gephyrin imaging; NLGN2 immunolocalization and Co-IP of PALS1/PATJ in pancreatic tissue with YAP activity assays\",\n      \"pmids\": [\"39284869\", \"38413734\", \"38571813\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MDGA1-NLGN2 antagonism operates at all inhibitory synapse subtypes untested\", \"Mechanism of NLGN2 interaction with PALS1/PATJ at tight junctions not structurally resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Domain-swap experiments definitively established that the NLGN2 extracellular domain is both necessary and sufficient for inhibitory-synapse targeting, while its cytoplasmic tail (including gephyrin-binding motif) is uniquely required for inhibitory but not excitatory synaptic function; in the lateral habenula, disrupting MDGA1–NLGN2 binding increases inhibitory synapse density and confers stress resilience.\",\n      \"evidence\": \"Chimeric Nlgn1-Nlgn2 rescue in neuroligin-null neurons with electrophysiology; MDGA1 KO and Nlgn2 MDGA1-binding-deficient knock-in in LHb with electrophysiology and chronic stress behavioral paradigm\",\n      \"pmids\": [\"39747663\", \"39897557\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the extracellular determinant within the NLGN2 ECD that specifies inhibitory targeting not mapped to specific residues\", \"Whether LHb MDGA1-NLGN2 axis is therapeutically targetable unknown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"NLGN2–neurexin adhesion is specifically required during a brief consolidation window (~10 min post-induction) for inhibitory long-term potentiation at both SST and PV inputs onto CA1 pyramidal cells, during which NLGN2 and gephyrin are recruited to potentiated synapses; biophysically, the NLGN2 ectodomain shows intermediate homodimerization affinity among neuroligins.\",\n      \"evidence\": \"Temporally controlled neurolide-2 peptide application during whole-cell recordings with optogenetic isolation of SST/PV inputs; mass photometry of recombinant NLGN2 ECD\",\n      \"pmids\": [\"41802868\", \"42033941\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling cascade linking neurexin binding to gephyrin recruitment during iLTP not identified\", \"Whether dimerization equilibrium is regulated at synapses in vivo unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the protease mediating NMDA-triggered NLGN2 cleavage, the specific extracellular residues that confer inhibitory-synapse targeting, the structural basis of the NLGN2–gephyrin cytoplasmic interaction, and whether the non-neuronal functions (pancreatic polarity, vascular regulation) share molecular mechanisms with synaptic NLGN2 function.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Protease identity for activity-dependent NLGN2 cleavage unknown\", \"No atomic-resolution structure of full-length NLGN2 including transmembrane and cytoplasmic domains\", \"Relationship between neuronal and non-neuronal NLGN2 functions mechanistically unexplored\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [0, 2, 3, 5, 6, 25]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [2, 3, 4, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 2, 3, 4, 6, 11]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [2, 3, 6, 7, 8, 10, 11, 20, 25]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [0, 5, 6, 14, 16, 25]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [23, 28]}\n    ],\n    \"complexes\": [\n      \"NLGN2–neurexin trans-synaptic complex\",\n      \"NLGN2–MDGA1 cis complex\",\n      \"NLGN2–gephyrin postsynaptic scaffold\"\n    ],\n    \"partners\": [\n      \"NRXN1\",\n      \"NRXN2\",\n      \"MDGA1\",\n      \"GPHN\",\n      \"SNX27\",\n      \"SERT\",\n      \"FMRP\",\n      \"IGSF9B\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}