Affinage

MDGA1

MAM domain-containing glycosylphosphatidylinositol anchor protein 1 · UniProt Q8NFP4

Length
955 aa
Mass
105.8 kDa
Annotated
2026-04-28
26 papers in source corpus 16 papers cited in narrative 16 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

MDGA1 is a GPI-anchored immunoglobulin superfamily cell adhesion molecule that functions as a negative regulator of inhibitory synaptogenesis by binding neuroligin-2 in cis on the postsynaptic membrane and sterically occluding neurexin access, thereby suppressing GABAergic synapse formation and gephyrin scaffold assembly (PMID:28641112, PMID:28641111, PMID:39284869). Crystal structures reveal that two MDGA1 molecules span the neuroligin-2 dimer via Ig1–Ig3 domains, with the compact triangular conformation of the full ectodomain required for functional concealment of neuroligin-2 from neurexin-1β; disease-associated mutations that disrupt this conformation abolish synaptic regulation and produce ASD-relevant behavioral deficits in knockin mice (PMID:36889589, PMID:41862769). Beyond inhibitory synapse control, MDGA1 interacts with amyloid precursor protein through its MAM domain to mediate compartment-specific disinhibition at distal dendrites, is proteolytically cleaved by BACE1 in its juxtamembrane region, and acts cell-autonomously during cortical development to regulate radial neuronal migration and basal progenitor proliferation through a complex with Connexin43 (PMID:35074912, PMID:31908000, PMID:16641224, PMID:26776515). Genetic deletion of MDGA1 selectively increases hippocampal inhibitory synapse density and transmission, confers seizure resistance, impairs LTP and spatial memory, and in the lateral habenula protects against stress-induced depressive behaviors (PMID:29281813, PMID:39897557).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 2005 Medium

    Establishing that MDGA1 is a GPI-anchored, lipid-raft-resident glycoprotein resolved how it is tethered to the cell surface and positioned within membrane microdomains relevant for signaling.

    Evidence Cell fractionation, detergent-resistant membrane isolation, PI-PLC treatment, and glycosylation assays in human cells

    PMID:15922729

    Open questions at the time
    • Functional consequence of lipid-raft localization uncharacterized
    • Identity of signaling partners in raft microdomains unknown
  2. 2006 High

    Demonstrating that MDGA1 knockdown arrests radial migration of superficial cortical neurons—rescued by exogenous MDGA1—established a cell-autonomous developmental role independent of its later synaptic functions.

    Evidence In utero electroporation of RNAi with GFP tracking and rescue with rat MDGA1 construct

    PMID:16641224

    Open questions at the time
    • Downstream effectors mediating migration were not identified
    • Relationship between migration role and synaptic organizer function unclear
  3. 2006 Medium

    Domain-mapping binding assays showed that the MAM domain and Ig domain regions mediate distinct heterophilic interactions with axon-rich and muscle regions, establishing that MDGA1 uses different extracellular domains for context-dependent binding.

    Evidence Truncated protein binding assays in embryonic chick spinal cord

    PMID:16782075

    Open questions at the time
    • Specific binding partners for each domain were not identified
    • Single species/single method limits generalizability
  4. 2016 High

    Discovery that MDGA1 complexes with Connexin43 in basal progenitors and that its conditional deletion reduces progenitor proliferation and cortical neuron production revealed a non-synaptic developmental function in SVZ neurogenesis.

    Evidence Conditional knockout with floxed MDGA1 allele, co-immunoprecipitation with Connexin43, BrdU proliferation assay

    PMID:26776515

    Open questions at the time
    • Mechanism by which MDGA1–Connexin43 interaction promotes proliferation is unknown
    • Whether this complex involves gap junction channel function was not tested
  5. 2017 High

    Two independent crystal structures resolved how MDGA1 suppresses inhibitory synaptogenesis: two MDGA1 molecules bind the neuroligin-2 dimer through three Ig1–Ig3 contact interfaces, with Ig1 directly competing with neurexins for the same binding site on neuroligin-2, providing an atomic-resolution mechanism for steric occlusion.

    Evidence Crystal structures of MDGA1–NLGN2 complexes with mutagenesis validation and cell-based synaptogenesis assays from two independent groups

    PMID:28641111 PMID:28641112

    Open questions at the time
    • Why MDGA1 selectively associates with NLGN2 over NLGN1 in vivo despite similar in vitro affinities remained unexplained
    • Whether conformational dynamics of the full ectodomain beyond Ig1-3 matter was unknown
  6. 2017 High

    Germline knockout established that MDGA1 loss selectively elevates perisomatic inhibitory synapse density and GABAergic transmission in hippocampal CA1 without affecting excitatory synapses, linking the structural mechanism to circuit-level and behavioral outcomes including seizure resistance and memory deficits.

    Evidence Mdga1 knockout mouse with electrophysiology, immunostaining, behavioral testing (Morris water maze, contextual fear conditioning, seizure induction)

    PMID:29281813

    Open questions at the time
    • Why perisomatic but not distal dendritic inhibitory synapses are affected was unexplained
    • Compensation by MDGA2 was not assessed
  7. 2019 High

    Identification of MDGA1 as a BACE1 substrate cleaved in its juxtamembrane domain introduced regulated proteolysis as a mechanism controlling MDGA1 surface levels and potentially its synaptic function.

    Evidence Quantitative proteomics of BACE1 KO vs. WT mouse brains, immunoblot validation in primary neurons, cleavage site mapping

    PMID:31908000

    Open questions at the time
    • Functional consequence of BACE1 cleavage on inhibitory synapse regulation not tested
    • Whether cleavage is activity-dependent is unknown
  8. 2022 High

    Demonstrating that the MDGA1 MAM domain directly binds amyloid precursor protein and that presynaptic APP in interneurons is required for MDGA1-mediated disinhibition at distal dendrites revealed a trans-synaptic signaling axis for compartment-specific inhibitory synapse regulation.

    Evidence Co-immunoprecipitation, domain deletion mutants, electrophysiology, behavioral testing, protein infusion

    PMID:35074912

    Open questions at the time
    • Whether APP–MDGA1 interaction is regulated by BACE1 cleavage of either partner is unknown
    • Mechanism by which this interaction suppresses inhibitory synapses at distal dendrites is not resolved
  9. 2023 High

    Electron microscopy and designer mutants revealed that the full MDGA1 ectodomain samples compact and extended conformations, and that the compact triangular conformation is essential for concealing neuroligin-2 from neurexin in a cellular context, even though soluble ectodomain binding affinity is preserved in mutants—establishing that global 3D shape, not just local binding interfaces, gates function.

    Evidence Electron microscopy, surface plasmon resonance, cell-based binding and presynaptic differentiation assays with conformation-altering mutants

    PMID:36889589

    Open questions at the time
    • In vivo relevance of conformational regulation not tested at the time
    • What controls the equilibrium between compact and extended states is unknown
  10. 2023 Medium

    In a neuropathic pain model, upregulated spinal MDGA1 shifts neuroligin-2 interactions from inhibitory (gephyrin) to excitatory (PSD-95) scaffolding and increases surface AMPA receptors, with MDGA1 knockdown reversing pain hypersensitivity—extending MDGA1 function beyond development to adult spinal cord plasticity.

    Evidence Co-immunoprecipitation, synaptosomal fractionation, intrathecal siRNA, behavioral pain testing after spinal nerve ligation

    PMID:37955815

    Open questions at the time
    • Single lab finding; independent replication needed
    • Whether MDGA1 directly engages PSD-95 or indirectly re-routes NL2 is unclear
  11. 2024 High

    Genetic epistasis with Nlgn2 knockout demonstrated that MDGA1 loss ameliorates gephyrin aggregation defects and anxiety-like behavior caused by Nlgn2 deletion, while double deletion exacerbates layer-specific gephyrin puncta loss, formally establishing MDGA1 as a modulator of NLGN2-dependent gephyrin scaffold assembly.

    Evidence Double knockout mouse genetics, electrophysiology, gephyrin immunostaining, behavioral anxiety tests

    PMID:39284869

    Open questions at the time
    • Molecular mechanism by which MDGA1 influences gephyrin aggregation independently of neurexin–NLGN2 bridging is unclear
    • Layer-specific differences in double KO phenotype not mechanistically explained
  12. 2025 High

    MDGA1–NLGN2 interaction in the lateral habenula is elevated by chronic stress, and disrupting this interaction (by MDGA1 knockout or NLGN2 binding-deficient knockin) increases inhibitory transmission and confers resilience to stress-induced depressive behavior, extending the MDGA1 mechanism to mood-related circuitry.

    Evidence Conditional knockout/re-expression via viral Cre, Nlgn2 variant knockin, electrophysiology, chemogenetics, behavioral depression tests

    PMID:39897557

    Open questions at the time
    • How chronic stress upregulates the MDGA1–NLGN2 interaction is unknown
    • Whether BACE1 cleavage of MDGA1 modulates this stress-sensitive interaction is not addressed
  13. 2025 High

    Disease-associated MDGA1 mutations that disrupt the triangular ectodomain conformation abolish GABAergic synapse regulation and produce ASD-relevant behavioral deficits in knockin mice, directly linking the structural mechanism to neurodevelopmental disease and validating the conformational requirement in vivo.

    Evidence Structural analysis of mutant proteins, in utero electroporation, slice electrophysiology, knockin mouse behavioral phenotyping, proteomics

    PMID:41862769

    Open questions at the time
    • Whether pharmacological restoration of ectodomain conformation is feasible beyond bazedoxifene is untested
    • Proteomics-identified downstream changes not functionally validated

Open questions

Synthesis pass · forward-looking unresolved questions
  • Major open questions include: what controls the equilibrium between compact and extended MDGA1 conformations, how BACE1-mediated cleavage feeds back on inhibitory synapse regulation, the basis of in vivo selectivity for NLGN2 over NLGN1, and how MDGA1's developmental roles in migration and progenitor proliferation relate mechanistically to its synaptic organizer function.
  • No mechanism linking conformational dynamics to specific signaling or activity-dependent triggers
  • BACE1 cleavage functional consequences not characterized
  • In vivo NLGN2 selectivity mechanism unresolved

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 5 GO:0098631 cell adhesion mediator activity 3
Localization
GO:0005886 plasma membrane 2 GO:0005829 cytosol 1
Pathway
R-HSA-112316 Neuronal System 5 R-HSA-1500931 Cell-Cell communication 3 R-HSA-1266738 Developmental Biology 2
Partners
APPBACE1GJA1NLGN2NRXN1

Evidence

Reading pass · 16 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2017 MDGA1 Ig1-Ig2 binds NLGN2 with nanomolar affinity; crystal structure of the complex shows two MDGA1 Ig1-Ig2 molecules spanning the entire NLGN2 dimer, with Ig1 occupying the same region on NLGN2 as neurexins do, establishing that MDGA1 sterically blocks neurexin access to neuroligin-2 to regulate trans-synaptic bridge formation. Crystal structure determination, nanomolar binding affinity measurement, site-directed mutagenesis confirming interaction interface Neuron High 28641112
2017 Crystal structures of human NL2/MDGA1 Ig1-3 complex reveal a 2:2 arrangement with three interaction interfaces; all three contact patches are required for MDGA1's negative regulation of NL2-mediated synaptogenic activity; MDGA1 Ig1 domain competes with neurexins for NL2 binding; despite similar affinities for NL1 and NL2 in vitro, MDGA1 selectively associates with NL2 but not NL1 in vivo. Crystal structure determination, cell-based synaptogenesis assays with structure-guided site-directed mutants, binding affinity measurements Neuron High 28641111
2017 Genetic deletion of MDGA1 in vivo selectively elevates hippocampal CA1 inhibitory (but not excitatory) synapse density and transmission; MDGA1 is expressed by pyramidal neurons and regulates perisomatic but not distal dendritic inhibitory synapses; Mdga1-/- mice show resistance to induced seizures, impaired hippocampal LTP, and deficits in spatial and context-dependent learning and memory. Germline knockout mouse, electrophysiology, immunostaining, behavioral tests (Morris water maze, contextual fear conditioning), seizure induction Cell reports High 29281813
2006 RNAi knockdown of MDGA1 in vivo blocks proper radial migration of superficial layer (2/3) cortical neurons; the migration defect is rescued by cotransfection of rat MDGA1, confirming cell-autonomous requirement for MDGA1 in cortical neuron migration. In utero electroporation of RNAi constructs, GFP reporter tracking, rescue experiment with rat MDGA1 construct The Journal of neuroscience High 16641224
2006 MDGA1 interacts heterophilically with axon-rich regions primarily through its MAM domain, and with differentiating muscle through its N-terminal Ig domain region, suggesting domain-specific binding partners in the developing nervous system. Binding assays with distinct truncated protein constructs (MAM domain vs. Ig domain regions) in embryonic chick spinal cord Brain research Medium 16782075
2005 Human MDGA1 is a GPI-anchored protein that localizes to the plasma membrane via the secretory pathway; it resides specifically in lipid raft microdomains and undergoes N-glycosylation as a post-translational modification; GPI anchor is cleavable by phospholipase C (PI-PLC). Cell fractionation, detergent-resistant membrane isolation, PI-PLC treatment, glycosylation assays, immunofluorescence Experimental cell research Medium 15922729
2016 MDGA1 is expressed in basal progenitor (BP) cell membranes where it co-localizes and forms a complex with the gap junction protein Connexin43; deletion of MDGA1 from BPs reduces BP proliferation, reduces SVZ size, causes ectopic BP positioning, and diminishes cortical layer neuron production. Conditional knockout using floxed MDGA1 allele, co-immunoprecipitation with Connexin43, immunostaining, BrdU proliferation assay Cell reports High 26776515
2019 MDGA1 is a substrate of the Alzheimer's disease protease BACE1 in vivo; BACE1 cleaves MDGA1 within its juxtamembrane domain; inhibition or deletion of BACE1 in primary neurons causes accumulation of full-length MDGA1. Isotope-label quantitative proteomics of BACE1 KO vs. wild-type mouse brains, immunoblot validation in primary neurons and mouse brains, cleavage site mapping FASEB journal High 31908000
2022 The MDGA1 MAM domain directly interacts with the extension domain of amyloid precursor protein (APP); MDGA1-mediated synaptic disinhibition requires the MAM domain and is prominent at distal dendrites of hippocampal CA1 pyramidal neurons; presynaptic APP in interneurons is required for MDGA1-mediated disinhibition; overexpression of wild-type or MAM-only MDGA1, but not MAM-deleted MDGA1, impairs novel object-recognition memory. Co-immunoprecipitation, domain deletion mutants, electrophysiology, behavioral testing, protein infusion experiments PNAS High 35074912
2023 WT MDGA1 can adopt both compact and extended 3D conformations while binding NLGN2; designer mutants targeting molecular elbows alter the distribution of 3D conformations without changing NLGN2 binding affinity of soluble ectodomains, but in cellular context impair binding to NLGN2, decrease capacity to conceal NLGN2 from NRXN1β, and suppress NLGN2-mediated inhibitory presynaptic differentiation, demonstrating that global 3D conformation of the full MDGA1 ectodomain is critical for function. Electron microscopy of conformational states, surface plasmon resonance, cell-based binding assays, presynaptic differentiation assays with designer mutants Journal of Biological Chemistry High 36889589
2024 Loss of MDGA1 (but not heterozygous MDGA2 deletion) ameliorates abnormal cytosolic gephyrin aggregation, reduction in inhibitory synaptic transmission, and exacerbated anxiety in Nlgn2 knockout mice; combined Nlgn2 and MDGA1 deletion causes exacerbated layer-specific loss of gephyrin puncta, establishing MDGA1 as a functional modulator of NLGN2-dependent gephyrin scaffold assembly and GABAergic synapse organization. Double knockout mouse genetics (epistasis), electrophysiology, immunostaining for gephyrin puncta, behavioral tests Communications biology High 39284869
2023 Endogenous MDGA1 (using epitope-tagged knock-in mice) is enriched at excitatory, not inhibitory, synapses; shRNA knockdown and CRISPR/Cas9 knockout of MDGA1 causes cell-autonomous impairment of AMPA receptor-mediated excitatory synaptic transmission without affecting GABAergic transmission. Epitope-tagged knock-in mice, shRNA knockdown, CRISPR/Cas9 knockout, slice electrophysiology bioRxiv (preprint)preprint Medium 37720016
2023 After spinal nerve ligation, upregulated spinal MDGA1 alters neuroligin-2 interactions: it increases the excitatory scaffolding interaction between NL2 and PSD-95, decreases the inhibitory interaction between NL2 and Gephyrin, and increases surface delivery of GluR1 AMPA receptor subunits in the dorsal horn; MDGA1 siRNA knockdown reverses these changes and reduces pain hypersensitivity. Co-immunoprecipitation, synaptosomal fractionation, western blot, intrathecal siRNA injection, behavioral pain testing Neurochemical research Medium 37955815
2025 MDGA1 and Nlgn2 selectively interact in the lateral habenula (LHb); their interaction is elevated following chronic restraint stress; germline MDGA1 knockout or introduction of an Nlgn2 variant incapable of binding MDGA1 increases inhibitory transmission and GABAergic synapse density in LHb; MDGA1 deficiency in adult LHb confers resistance to stress-induced depressive behaviors, establishing MDGA1–Nlgn2 interaction as a regulator of inhibitory synapse strength in depression-relevant circuitry. Conditional knockout/re-expression using viral Cre, knockin Nlgn2 variant, electrophysiology, immunostaining, chemogenetic LH activation, behavioral depression tests Theranostics High 39897557
2010 MDGA1 overexpression in MDCK cells increases cell motility and cell-cell adhesion but reduces adhesion to extracellular matrix proteins (especially collagen IV); domain dissection shows both Ig and MAM domains contribute to motility, while MAM domain mediates heterophilic cell-cell adhesion; siRNA silencing of MDGA1 increases adhesion to collagen IV. Stable cell line overexpression of full-length and domain-truncated constructs, siRNA knockdown, migration assays, adhesion assays Cancer microenvironment Medium 21505559
2025 The MDGA1 Tyr635Cys/Glu756Gln double mutation disrupts the triangular extracellular domain structure of MDGA1 and abolishes its ability to impact GABAergic synapses; in utero overexpression of the Val116Met/Ala688Val variant alters cortical neuron migration; male knockin mice carrying Tyr636Cys/Glu751Gln show impaired GABAergic synaptic strength and ASD-relevant behavioral deficits reversible by bazedoxifene. Structural analysis of mutant proteins, in utero electroporation, electrophysiology in cultured neurons and CA1 slices, knockin mouse behavioral phenotyping, proteomics EMBO molecular medicine High 41862769

Source papers

Stage 0 corpus · 26 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2008 Association analysis of schizophrenia on 18 genes involved in neuronal migration: MDGA1 as a new susceptibility gene. American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics 103 18384059
2017 Molecular Mechanism of MDGA1: Regulation of Neuroligin 2:Neurexin Trans-synaptic Bridges. Neuron 61 28641112
2017 Structural Insights into Modulation of Neurexin-Neuroligin Trans-synaptic Adhesion by MDGA1/Neuroligin-2 Complex. Neuron 57 28641111
2006 Radial migration of superficial layer cortical neurons controlled by novel Ig cell adhesion molecule MDGA1. The Journal of neuroscience : the official journal of the Society for Neuroscience 53 16641224
2017 Loss of Synapse Repressor MDGA1 Enhances Perisomatic Inhibition, Confers Resistance to Network Excitation, and Impairs Cognitive Function. Cell reports 49 29281813
2010 The MDGA1 gene confers risk to schizophrenia and bipolar disorder. Schizophrenia research 36 21146959
2006 Novel IgCAM, MDGA1, expressed in unique cortical area- and layer-specific patterns and transiently by distinct forebrain populations of Cajal-Retzius neurons. Cerebral cortex (New York, N.Y. : 1991) 34 16959869
2006 MDGA1, an IgSF molecule containing a MAM domain, heterophilically associates with axon- and muscle-associated binding partners through distinct structural domains. Brain research 28 16782075
2022 MDGA1 negatively regulates amyloid precursor protein-mediated synapse inhibition in the hippocampus. Proceedings of the National Academy of Sciences of the United States of America 27 35074912
2019 Mouse brain proteomics establishes MDGA1 and CACHD1 as in vivo substrates of the Alzheimer protease BACE1. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 21 31908000
2005 Characterization of MDGA1, a novel human glycosylphosphatidylinositol-anchored protein localized in lipid rafts. Experimental cell research 18 15922729
2016 Formation of the Cortical Subventricular Zone Requires MDGA1-Mediated Aggregation of Basal Progenitors. Cell reports 17 26776515
2009 Characterization of teleost Mdga1 using a gene-trap approach in medaka (Oryzias latipes). Genesis (New York, N.Y. : 2000) 12 19422017
2022 Differential expression of MDGA1 in major depressive disorder. Brain, behavior, & immunity - health 11 36247836
2023 Designer molecules of the synaptic organizer MDGA1 reveal 3D conformational control of biological function. The Journal of biological chemistry 10 36889589
2010 Expression of Human MDGA1 Increases Cell Motility and Cell-Cell Adhesion and Reduces Adhesion to Extracellular Matrix Proteins in MDCK Cells. Cancer microenvironment : official journal of the International Cancer Microenvironment Society 10 21505559
2024 Functional Neuroligin-2-MDGA1 interactions differentially regulate synaptic GABAARs and cytosolic gephyrin aggregation. Communications biology 8 39284869
2025 Chronic stress induces depression through MDGA1-Neuroligin2 mediated suppression of inhibitory synapses in the lateral habenula. Theranostics 7 39897557
2023 Contrastsing synaptic roles of MDGA1 and MDGA2. bioRxiv : the preprint server for biology 6 37720016
2023 Upregulation of Spinal MDGA1 in Rats After Nerve Injury Alters Interactions Between Neuroligin-2 and Postsynaptic Scaffolding Proteins and Increases GluR1 Subunit Surface Delivery in the Spinal Cord Dorsal Horn. Neurochemical research 4 37955815
2024 Impaired Hippocampal Long-Term Potentiation and Memory Deficits upon Haploinsufficiency of MDGA1 Can Be Rescued by Acute Administration of D-Cycloserine. International journal of molecular sciences 3 39273620
2025 Preliminary findings of DNA hypermethylation of MDGA1 in idiopathic restless legs syndrome. Sleep medicine 1 40058148
2026 Localization and Functional Characterization of MDGA1 in Mouse Hippocampus. The Journal of neuroscience : the official journal of the Society for Neuroscience 0 41530055
2026 Bazedoxifene reverses sexually dimorphic autistic-like abnormalities in biallelic MDGA1-mutant mice. EMBO molecular medicine 0 41862769
2025 MDGA1 Gene Variants and Risk for Restless Legs Syndrome. International journal of molecular sciences 0 40724952
2009 WITHDRAWN: Common polymorphisms in the MDGA1 gene are associated with bipolar disorder and schizophrenia in the Chinese Han population. Progress in neuro-psychopharmacology & biological psychiatry 0 20036297