{"gene":"MS4A6A","run_date":"2026-06-10T02:59:51","timeline":{"discoveries":[{"year":2022,"finding":"MS4A6A promotes surface expression of FcεRI complexes on human mast cells and facilitates IgE-mediated degranulation, functioning as a compensatory FcεRIβ-like protein when FcεRIβ is absent or reduced. MS4A6A is structurally related to FcεRIβ (MS4A2) and resides in the same MS4A gene cluster at 11q12-q13.","method":"Exon-skipping oligonucleotides targeting FcεRIβ in human vs. mouse mast cells; functional degranulation assays; surface expression analysis","journal":"Allergy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean loss-of-function (exon-skipping), defined cellular phenotype (degranulation, FcεRI surface expression), single lab with two orthogonal functional readouts","pmids":["36424895"],"is_preprint":false},{"year":2025,"finding":"MS4A4A interacts directly with MS4A6A and protects it from proteasomal degradation. MS4A6A in turn forms a complex with the co-receptor DAP12, blocking DAP12-dependent stabilization, cell-surface localization, and signaling of TREM2. This MS4A4A–MS4A6A–DAP12 axis makes MS4A4A and MS4A6A cooperative post-transcriptional negative regulators of both transmembrane and soluble TREM2 levels, and limits microglia viability, phagocytosis, and lysosomal function.","method":"CRISPR knockout, MS4A4A-degrading antibodies, overexpression in macrophages/microglia/non-human primates/amyloid mouse model; co-immunoprecipitation of MS4A6A–DAP12 complex; measurement of transmembrane and soluble TREM2 levels; phagocytosis and lysosomal function assays","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP establishing MS4A6A–DAP12 complex, CRISPR KO plus antibody degradation as orthogonal loss-of-function approaches, multiple model systems (primary human microglia, NHP, mouse), multiple functional readouts; published in peer-reviewed journal and independently preprinted","pmids":["41435829"],"is_preprint":false},{"year":2024,"finding":"MS4A4A protects MS4A6A from degradation (consistent with the Neuron 2025 paper); MS4A6A forms a complex with DAP12 to restrain TREM2 levels and microglial states. Additionally, MS4A4A and MS4A6A negatively regulate microglia proliferation, survival, metabolism, lysosomal function, phagocytosis, and disease-associated microglia states.","method":"CRISPR KO and MS4A4A-degrading antibodies in primary human microglia, NHP, and xenotransplantation amyloid model; Co-IP of MS4A6A–DAP12 complex; measurement of TREM2 surface levels and sTREM2","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — preprint version of the Neuron 2025 study; same mechanistic findings with multiple orthogonal methods but not yet peer-reviewed at time of deposition","pmids":["bio_10.1101_2024.11.23.625001"],"is_preprint":true},{"year":2025,"finding":"Ms4a6d (mouse ortholog of MS4A6A) deficiency in APP/PS1 mice reduces microglial envelopment and phagocytosis of amyloid plaques, increases plaque burden and synaptic damage, and exacerbates NF-κB-driven neuroinflammation in both microglia and astrocytes. Conversely, overexpression of MS4A6A in a human microglia cell line promotes plaque-associated gene expression and diminishes inflammatory signatures.","method":"Ms4a6d knockout in APP/PS1 mouse model; high-resolution microscopy and immunostaining for amyloid phagocytosis; biochemical assessment of plaque burden; behavioral analysis; NF-κB signaling measurement; MS4A6A overexpression in human microglia cell line with transcriptomic readout","journal":"Molecular neurodegeneration","confidence":"High","confidence_rationale":"Tier 2 / Strong — first in vivo KO model of the gene with multiple orthogonal mechanistic readouts (phagocytosis, NF-κB signaling, plaque burden, behavior) plus overexpression validation in human cells, peer-reviewed","pmids":["40877951"],"is_preprint":false},{"year":2025,"finding":"MS4A6A promotes endothelial dysfunction and monocyte adhesion via the IKK/NF-κB signaling pathway. In ox-LDL-stimulated HUVECs, silencing MS4A6A reduced expression of inflammatory factors, adhesion molecules, and reactive oxygen species; IKK inhibition or IκBα silencing phenocopied MS4A6A knockdown, placing MS4A6A upstream of IKK/NF-κB in this context.","method":"siRNA silencing of MS4A6A in ox-LDL-stimulated HUVECs; Western blot; ELISA; immunofluorescence; IKK inhibitor Bay 11-7085 and IKK siRNA epistasis; monocyte adhesion assay; ApoE-/- HFD mouse model","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined loss-of-function cellular phenotype with pathway epistasis (IKK inhibitor + siRNA), single lab, two orthogonal pathway perturbations","pmids":["40090082"],"is_preprint":false},{"year":2025,"finding":"CRISPRi knockdown of MS4A6A in hiPSC-derived microglia elevated ROS production in response to poly(I:C) stimulation, increased the proportion of cells in a pro-inflammatory cluster (cluster 2), and reduced the proportion of cells in the disease-associated microglia (DAM) cluster under all conditions, indicating MS4A6A modulates the DAM response and restrains microglial inflammatory states.","method":"CRISPRi screen followed by CROP-seq (CRISPRi + single-cell RNA sequencing) in hiPSC-derived microglia; ROS measurement; single-cell cluster analysis","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPRi loss-of-function with dual orthogonal readouts (ROS and scRNA-seq cluster analysis), preprint, single lab","pmids":["bio_10.1101_2025.03.09.642133"],"is_preprint":true},{"year":2017,"finding":"A SNP (rs667897) at the MS4A locus creates an antioxidant response element that is bound by CNC transcription factors NRF1 and NRF2; the risk allele generates a strong binding sequence activated by proteostatic stress in an NRF1-dependent manner, and this activation is associated with increased MS4A6A expression.","method":"Reporter assays with risk vs. reference allele; NRF1/NRF2 binding validation; proteostatic stress induction; allele-specific expression analysis","journal":"Redox biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional reporter assay and allele-specific binding/expression, single lab, multiple orthogonal methods within one study","pmids":["29179108"],"is_preprint":false},{"year":2025,"finding":"The MS4A6A rs7232 SNP variant genotype is associated with lower MS4A6A protein expression due to proteasome-mediated protein degradation, and is associated with altered plasma TREM2 levels.","method":"Proteomics (OLINK panel), GWAS for plasma TREM2, and proteasome inhibition experiments assessing MS4A6A protein stability in relation to rs7232 genotype","journal":"Journal of proteomics and genomics research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — proteasome degradation mechanism mentioned but method details are sparse in abstract; single lab, single study","pmids":["41552371"],"is_preprint":false}],"current_model":"MS4A6A is a tetraspan membrane protein expressed on microglia and mast cells that acts as a negative regulator of TREM2 signaling by forming a complex with DAP12 (thereby blocking TREM2 surface localization and signaling), while its stability is controlled by its paralog MS4A4A; in microglia it suppresses amyloid phagocytosis and, when absent, disinhibits NF-κB-driven neuroinflammation, whereas in mast cells it compensates for FcεRIβ to support FcεRI surface expression and IgE-mediated degranulation, and in endothelial cells it promotes inflammation via the IKK/NF-κB pathway."},"narrative":{"mechanistic_narrative":"MS4A6A is a member of the MS4A family of tetraspan membrane proteins expressed in microglia, mast cells, and endothelial cells that functions as a post-transcriptional negative regulator of TREM2 signaling and a modulator of inflammatory state [PMID:41435829, PMID:40877951]. In microglia and macrophages, MS4A6A forms a complex with the co-receptor DAP12, blocking DAP12-dependent stabilization, surface localization, and signaling of TREM2 and thereby limiting microglial viability, phagocytosis, and lysosomal function; its own stability is maintained by direct interaction with its paralog MS4A4A, which protects it from proteasomal degradation [PMID:41435829]. In vivo loss of the mouse ortholog reduces microglial envelopment and phagocytosis of amyloid plaques, increases plaque burden and synaptic damage, and disinhibits NF-κB-driven neuroinflammation, while MS4A6A overexpression promotes plaque-associated gene expression and restrains inflammatory signatures, identifying MS4A6A as a restraint on disease-associated microglial inflammatory states [PMID:40877951]. In endothelial cells, MS4A6A acts upstream of the IKK/NF-κB pathway to promote endothelial dysfunction, inflammatory factor and adhesion molecule expression, and monocyte adhesion [PMID:40090082]. In mast cells, MS4A6A promotes surface expression of FcεRI complexes and facilitates IgE-mediated degranulation, acting as a compensatory FcεRIβ-like protein when FcεRIβ is absent or reduced [PMID:36424895].","teleology":[{"year":2017,"claim":"Before functional roles were defined, it was unclear how Alzheimer-associated MS4A locus variation altered gene expression; this work showed a risk SNP creates an antioxidant response element driving MS4A6A transcription.","evidence":"Reporter assays with risk vs. reference allele plus NRF1/NRF2 binding validation under proteostatic stress","pmids":["29179108"],"confidence":"Medium","gaps":["Does not establish the downstream cellular function of elevated MS4A6A","Links transcription to stress but not to a specific disease mechanism"]},{"year":2022,"claim":"The cellular function of MS4A6A was unknown; this work established a role in mast cells as a compensatory FcεRIβ-like protein supporting FcεRI surface expression and IgE-mediated degranulation.","evidence":"Exon-skipping of FcεRIβ in human vs. mouse mast cells with degranulation and surface expression readouts","pmids":["36424895"],"confidence":"Medium","gaps":["Mechanism of FcεRI complex stabilization not defined at the molecular level","Relevance to non-mast-cell lineages (microglia, endothelium) not addressed"]},{"year":2024,"claim":"How MS4A proteins regulate TREM2 was unresolved; this preprint established that MS4A6A forms a complex with DAP12 to restrain TREM2 and that MS4A4A protects MS4A6A from degradation, negatively regulating microglial proliferation, metabolism, and phagocytosis.","evidence":"CRISPR KO and MS4A4A-degrading antibodies in primary human microglia, NHP, and amyloid model; Co-IP of MS4A6A–DAP12 (preprint)","pmids":["bio_10.1101_2024.11.23.625001"],"confidence":"Medium","gaps":["Preprint version not yet peer-reviewed at deposition","Stoichiometry and structural basis of the MS4A4A–MS4A6A–DAP12 axis undefined"]},{"year":2025,"claim":"The peer-reviewed study confirmed the MS4A4A–MS4A6A–DAP12 axis as a cooperative post-transcriptional negative regulator of both transmembrane and soluble TREM2, limiting microglial viability, phagocytosis, and lysosomal function.","evidence":"Reciprocal Co-IP, CRISPR KO plus antibody degradation, multiple model systems, and TREM2/phagocytosis/lysosomal readouts","pmids":["41435829"],"confidence":"High","gaps":["Structural model of how MS4A6A blocks DAP12-dependent TREM2 stabilization not resolved","Whether the DAP12 interaction underlies the mast-cell and endothelial roles is untested"]},{"year":2025,"claim":"In vivo causality in amyloid pathology was untested; ortholog knockout showed MS4A6A loss reduces amyloid phagocytosis and disinhibits NF-κB-driven neuroinflammation, while overexpression promotes plaque-associated gene programs.","evidence":"Ms4a6d knockout in APP/PS1 mice with phagocytosis, plaque burden, NF-κB, and behavioral readouts plus overexpression in human microglia","pmids":["40877951"],"confidence":"High","gaps":["Apparent contrast with the TREM2-restraining model not mechanistically reconciled","Direct link between NF-κB disinhibition and the DAP12/TREM2 axis not established"]},{"year":2025,"claim":"Whether MS4A6A drives inflammation outside microglia was unknown; this work placed MS4A6A upstream of IKK/NF-κB in endothelial cells, promoting dysfunction and monocyte adhesion.","evidence":"siRNA silencing in ox-LDL-stimulated HUVECs with IKK inhibitor and IKK/IκBα epistasis plus ApoE-/- mouse model","pmids":["40090082"],"confidence":"Medium","gaps":["Molecular link between MS4A6A and IKK activation not defined","Single-lab finding without independent replication"]},{"year":2025,"claim":"Complementing the locus genetics, CRISPRi knockdown in hiPSC microglia showed MS4A6A restrains pro-inflammatory states and modulates the disease-associated microglia (DAM) response.","evidence":"CRISPRi/CROP-seq in hiPSC-derived microglia with ROS and single-cell cluster analysis (preprint)","pmids":["bio_10.1101_2025.03.09.642133"],"confidence":"Medium","gaps":["Preprint, single lab","Effector pathway linking knockdown to DAM-cluster shift not defined"]},{"year":2025,"claim":"A coding/regulatory variant link to protein levels was needed; the rs7232 variant was associated with lower MS4A6A protein via proteasome-mediated degradation and altered plasma TREM2.","evidence":"Proteomics (OLINK), plasma TREM2 GWAS, and proteasome inhibition assays by rs7232 genotype","pmids":["41552371"],"confidence":"Low","gaps":["Method details sparse and not independently confirmed","Causal chain from genotype to TREM2 not directly demonstrated"]},{"year":null,"claim":"How MS4A6A reconciles its apparently opposing roles — restraining TREM2 signaling versus supporting amyloid phagocytosis and FcεRI/IKK-driven inflammation across cell types — remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of the MS4A4A–MS4A6A–DAP12 complex","Cell-type-specific determinants of pro- vs. anti-inflammatory output unknown","Direct biochemical activity of MS4A6A beyond complex formation undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,3]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1,3,4]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4]}],"complexes":[],"partners":["MS4A4A","DAP12","TREM2","FCER1B"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H2W1","full_name":"Membrane-spanning 4-domains subfamily A member 6A","aliases":["CD20 antigen-like 3","Four-span transmembrane protein 3"],"length_aa":248,"mass_kda":26.9,"function":"May be involved in signal transduction as a component of a multimeric receptor complex","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q9H2W1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MS4A6A","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MS4A6A","total_profiled":1310},"omim":[{"mim_id":"608907","title":"ALZHEIMER DISEASE 9, SUSCEPTIBILITY TO; AD9","url":"https://www.omim.org/entry/608907"},{"mim_id":"608402","title":"MEMBRANE-SPANNING 4-DOMAINS, SUBFAMILY A, MEMBER 6E; MS4A6E","url":"https://www.omim.org/entry/608402"},{"mim_id":"608401","title":"MEMBRANE-SPANNING 4-DOMAINS, SUBFAMILY A, MEMBER 4E; MS4A4E","url":"https://www.omim.org/entry/608401"},{"mim_id":"606548","title":"MEMBRANE-SPANNING 4-DOMAINS, SUBFAMILY A, MEMBER 6A; MS4A6A","url":"https://www.omim.org/entry/606548"},{"mim_id":"605414","title":"ATP-BINDING CASSETTE, SUBFAMILY A, MEMBER 7; ABCA7","url":"https://www.omim.org/entry/605414"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MS4A6A"},"hgnc":{"alias_symbol":["CD20L3"],"prev_symbol":["MS4A6"]},"alphafold":{"accession":"Q9H2W1","domains":[{"cath_id":"1.20.120","chopping":"39-153_175-212","consensus_level":"high","plddt":89.2024,"start":39,"end":212}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H2W1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H2W1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H2W1-F1-predicted_aligned_error_v6.png","plddt_mean":74.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MS4A6A","jax_strain_url":"https://www.jax.org/strain/search?query=MS4A6A"},"sequence":{"accession":"Q9H2W1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H2W1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H2W1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H2W1"}},"corpus_meta":[{"pmid":"21460840","id":"PMC_21460840","title":"Common variants at ABCA7, MS4A6A/MS4A4E, EPHA1, CD33 and CD2AP are associated with Alzheimer's disease.","date":"2011","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21460840","citation_count":1635,"is_preprint":false},{"pmid":"26923404","id":"PMC_26923404","title":"Common variants in ABCA7 and MS4A6A are associated with cortical and hippocampal atrophy.","date":"2015","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/26923404","citation_count":45,"is_preprint":false},{"pmid":"24064185","id":"PMC_24064185","title":"Alzheimer's disease susceptibility variants in the MS4A6A gene are associated with altered levels of MS4A6A expression in blood.","date":"2013","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/24064185","citation_count":45,"is_preprint":false},{"pmid":"22382309","id":"PMC_22382309","title":"The prevalence of CD33 and MS4A6A variant in Chinese Han population with Alzheimer's disease.","date":"2012","source":"Human 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letters","url":"https://pubmed.ncbi.nlm.nih.gov/27085534","citation_count":19,"is_preprint":false},{"pmid":"31799158","id":"PMC_31799158","title":"Association of MS4A6A, CD33, and TREM2 gene polymorphisms with the late-onset Alzheimer's disease.","date":"2019","source":"BioImpacts : BI","url":"https://pubmed.ncbi.nlm.nih.gov/31799158","citation_count":10,"is_preprint":false},{"pmid":"27337227","id":"PMC_27337227","title":"APOE and MS4A6A interact with GnRH signaling in Alzheimer's disease: Enrichment of epistatic effects.","date":"2016","source":"Alzheimer's & dementia : the journal of the Alzheimer's Association","url":"https://pubmed.ncbi.nlm.nih.gov/27337227","citation_count":9,"is_preprint":false},{"pmid":"36424895","id":"PMC_36424895","title":"Identification of redundancy between human FcεRIβ and MS4A6A proteins points toward additional complex mechanisms for FcεRI trafficking and signaling.","date":"2022","source":"Allergy","url":"https://pubmed.ncbi.nlm.nih.gov/36424895","citation_count":8,"is_preprint":false},{"pmid":"40090082","id":"PMC_40090082","title":"MS4A6A regulates ox-LDL-induced endothelial dysfunction and monocyte adhesion in atherosclerosis via the IKK/NF-kappaB pathway.","date":"2025","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/40090082","citation_count":7,"is_preprint":false},{"pmid":"41435829","id":"PMC_41435829","title":"The Alzheimer's disease risk genes MS4A4A and MS4A6A cooperate to negatively regulate TREM2 and microglia states.","date":"2025","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/41435829","citation_count":4,"is_preprint":false},{"pmid":"38488530","id":"PMC_38488530","title":"Involvement of microglia-expressed MS4A6A in the onset of glioblastoma.","date":"2024","source":"The European journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/38488530","citation_count":4,"is_preprint":false},{"pmid":"40877951","id":"PMC_40877951","title":"MS4A6A/Ms4a6d deficiency disrupts neuroprotective microglia functions and promotes inflammation in Alzheimer's disease model.","date":"2025","source":"Molecular neurodegeneration","url":"https://pubmed.ncbi.nlm.nih.gov/40877951","citation_count":2,"is_preprint":false},{"pmid":"38644829","id":"PMC_38644829","title":"Identifying MS4A6A+ macrophages as potential contributors to the pathogenesis of nonalcoholic fatty liver disease, periodontitis, and type 2 diabetes mellitus.","date":"2024","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/38644829","citation_count":2,"is_preprint":false},{"pmid":"41515934","id":"PMC_41515934","title":"The Myeloid Biomarker MS4A6A Drives an Immunosuppressive Microenvironment in Glioblastoma via Activation of the PGE2 Signaling Axis.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41515934","citation_count":1,"is_preprint":false},{"pmid":"41552371","id":"PMC_41552371","title":"Plasma TREM2 levels, alcohol consumption, and liver enzymes in patients with alcohol use disorder: a sex-dependent relationship involving MS4A6A genetic polymorphism.","date":"2025","source":"Journal of proteomics and genomics research","url":"https://pubmed.ncbi.nlm.nih.gov/41552371","citation_count":1,"is_preprint":false},{"pmid":"41694841","id":"PMC_41694841","title":"Transient Neonatal Diabetes Mellitus Potentially Associated With a Novel Homozygous MS4A6A Gene Variant: A Case Report.","date":"2026","source":"Cureus","url":"https://pubmed.ncbi.nlm.nih.gov/41694841","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.03.09.642133","title":"High throughput identification of genetic regulators of microglial inflammatory processes in Alzheimer’s 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disease","date":"2025-04-08","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.07.25325386","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13893,"output_tokens":2526,"usd":0.039785,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9680,"output_tokens":3269,"usd":0.065062,"stage2_stop_reason":"end_turn"},"total_usd":0.104847,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2022,\n      \"finding\": \"MS4A6A promotes surface expression of FcεRI complexes on human mast cells and facilitates IgE-mediated degranulation, functioning as a compensatory FcεRIβ-like protein when FcεRIβ is absent or reduced. MS4A6A is structurally related to FcεRIβ (MS4A2) and resides in the same MS4A gene cluster at 11q12-q13.\",\n      \"method\": \"Exon-skipping oligonucleotides targeting FcεRIβ in human vs. mouse mast cells; functional degranulation assays; surface expression analysis\",\n      \"journal\": \"Allergy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean loss-of-function (exon-skipping), defined cellular phenotype (degranulation, FcεRI surface expression), single lab with two orthogonal functional readouts\",\n      \"pmids\": [\"36424895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MS4A4A interacts directly with MS4A6A and protects it from proteasomal degradation. MS4A6A in turn forms a complex with the co-receptor DAP12, blocking DAP12-dependent stabilization, cell-surface localization, and signaling of TREM2. This MS4A4A–MS4A6A–DAP12 axis makes MS4A4A and MS4A6A cooperative post-transcriptional negative regulators of both transmembrane and soluble TREM2 levels, and limits microglia viability, phagocytosis, and lysosomal function.\",\n      \"method\": \"CRISPR knockout, MS4A4A-degrading antibodies, overexpression in macrophages/microglia/non-human primates/amyloid mouse model; co-immunoprecipitation of MS4A6A–DAP12 complex; measurement of transmembrane and soluble TREM2 levels; phagocytosis and lysosomal function assays\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP establishing MS4A6A–DAP12 complex, CRISPR KO plus antibody degradation as orthogonal loss-of-function approaches, multiple model systems (primary human microglia, NHP, mouse), multiple functional readouts; published in peer-reviewed journal and independently preprinted\",\n      \"pmids\": [\"41435829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MS4A4A protects MS4A6A from degradation (consistent with the Neuron 2025 paper); MS4A6A forms a complex with DAP12 to restrain TREM2 levels and microglial states. Additionally, MS4A4A and MS4A6A negatively regulate microglia proliferation, survival, metabolism, lysosomal function, phagocytosis, and disease-associated microglia states.\",\n      \"method\": \"CRISPR KO and MS4A4A-degrading antibodies in primary human microglia, NHP, and xenotransplantation amyloid model; Co-IP of MS4A6A–DAP12 complex; measurement of TREM2 surface levels and sTREM2\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — preprint version of the Neuron 2025 study; same mechanistic findings with multiple orthogonal methods but not yet peer-reviewed at time of deposition\",\n      \"pmids\": [\"bio_10.1101_2024.11.23.625001\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Ms4a6d (mouse ortholog of MS4A6A) deficiency in APP/PS1 mice reduces microglial envelopment and phagocytosis of amyloid plaques, increases plaque burden and synaptic damage, and exacerbates NF-κB-driven neuroinflammation in both microglia and astrocytes. Conversely, overexpression of MS4A6A in a human microglia cell line promotes plaque-associated gene expression and diminishes inflammatory signatures.\",\n      \"method\": \"Ms4a6d knockout in APP/PS1 mouse model; high-resolution microscopy and immunostaining for amyloid phagocytosis; biochemical assessment of plaque burden; behavioral analysis; NF-κB signaling measurement; MS4A6A overexpression in human microglia cell line with transcriptomic readout\",\n      \"journal\": \"Molecular neurodegeneration\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — first in vivo KO model of the gene with multiple orthogonal mechanistic readouts (phagocytosis, NF-κB signaling, plaque burden, behavior) plus overexpression validation in human cells, peer-reviewed\",\n      \"pmids\": [\"40877951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MS4A6A promotes endothelial dysfunction and monocyte adhesion via the IKK/NF-κB signaling pathway. In ox-LDL-stimulated HUVECs, silencing MS4A6A reduced expression of inflammatory factors, adhesion molecules, and reactive oxygen species; IKK inhibition or IκBα silencing phenocopied MS4A6A knockdown, placing MS4A6A upstream of IKK/NF-κB in this context.\",\n      \"method\": \"siRNA silencing of MS4A6A in ox-LDL-stimulated HUVECs; Western blot; ELISA; immunofluorescence; IKK inhibitor Bay 11-7085 and IKK siRNA epistasis; monocyte adhesion assay; ApoE-/- HFD mouse model\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined loss-of-function cellular phenotype with pathway epistasis (IKK inhibitor + siRNA), single lab, two orthogonal pathway perturbations\",\n      \"pmids\": [\"40090082\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CRISPRi knockdown of MS4A6A in hiPSC-derived microglia elevated ROS production in response to poly(I:C) stimulation, increased the proportion of cells in a pro-inflammatory cluster (cluster 2), and reduced the proportion of cells in the disease-associated microglia (DAM) cluster under all conditions, indicating MS4A6A modulates the DAM response and restrains microglial inflammatory states.\",\n      \"method\": \"CRISPRi screen followed by CROP-seq (CRISPRi + single-cell RNA sequencing) in hiPSC-derived microglia; ROS measurement; single-cell cluster analysis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPRi loss-of-function with dual orthogonal readouts (ROS and scRNA-seq cluster analysis), preprint, single lab\",\n      \"pmids\": [\"bio_10.1101_2025.03.09.642133\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A SNP (rs667897) at the MS4A locus creates an antioxidant response element that is bound by CNC transcription factors NRF1 and NRF2; the risk allele generates a strong binding sequence activated by proteostatic stress in an NRF1-dependent manner, and this activation is associated with increased MS4A6A expression.\",\n      \"method\": \"Reporter assays with risk vs. reference allele; NRF1/NRF2 binding validation; proteostatic stress induction; allele-specific expression analysis\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional reporter assay and allele-specific binding/expression, single lab, multiple orthogonal methods within one study\",\n      \"pmids\": [\"29179108\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The MS4A6A rs7232 SNP variant genotype is associated with lower MS4A6A protein expression due to proteasome-mediated protein degradation, and is associated with altered plasma TREM2 levels.\",\n      \"method\": \"Proteomics (OLINK panel), GWAS for plasma TREM2, and proteasome inhibition experiments assessing MS4A6A protein stability in relation to rs7232 genotype\",\n      \"journal\": \"Journal of proteomics and genomics research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — proteasome degradation mechanism mentioned but method details are sparse in abstract; single lab, single study\",\n      \"pmids\": [\"41552371\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MS4A6A is a tetraspan membrane protein expressed on microglia and mast cells that acts as a negative regulator of TREM2 signaling by forming a complex with DAP12 (thereby blocking TREM2 surface localization and signaling), while its stability is controlled by its paralog MS4A4A; in microglia it suppresses amyloid phagocytosis and, when absent, disinhibits NF-κB-driven neuroinflammation, whereas in mast cells it compensates for FcεRIβ to support FcεRI surface expression and IgE-mediated degranulation, and in endothelial cells it promotes inflammation via the IKK/NF-κB pathway.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MS4A6A is a member of the MS4A family of tetraspan membrane proteins expressed in microglia, mast cells, and endothelial cells that functions as a post-transcriptional negative regulator of TREM2 signaling and a modulator of inflammatory state [#1, #3]. In microglia and macrophages, MS4A6A forms a complex with the co-receptor DAP12, blocking DAP12-dependent stabilization, surface localization, and signaling of TREM2 and thereby limiting microglial viability, phagocytosis, and lysosomal function; its own stability is maintained by direct interaction with its paralog MS4A4A, which protects it from proteasomal degradation [#1]. In vivo loss of the mouse ortholog reduces microglial envelopment and phagocytosis of amyloid plaques, increases plaque burden and synaptic damage, and disinhibits NF-\\u03baB-driven neuroinflammation, while MS4A6A overexpression promotes plaque-associated gene expression and restrains inflammatory signatures, identifying MS4A6A as a restraint on disease-associated microglial inflammatory states [#3]. In endothelial cells, MS4A6A acts upstream of the IKK/NF-\\u03baB pathway to promote endothelial dysfunction, inflammatory factor and adhesion molecule expression, and monocyte adhesion [#4]. In mast cells, MS4A6A promotes surface expression of Fc\\u03b5RI complexes and facilitates IgE-mediated degranulation, acting as a compensatory Fc\\u03b5RI\\u03b2-like protein when Fc\\u03b5RI\\u03b2 is absent or reduced [#0].\",\n  \"teleology\": [\n    {\n      \"year\": 2017,\n      \"claim\": \"Before functional roles were defined, it was unclear how Alzheimer-associated MS4A locus variation altered gene expression; this work showed a risk SNP creates an antioxidant response element driving MS4A6A transcription.\",\n      \"evidence\": \"Reporter assays with risk vs. reference allele plus NRF1/NRF2 binding validation under proteostatic stress\",\n      \"pmids\": [\"29179108\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Does not establish the downstream cellular function of elevated MS4A6A\",\n        \"Links transcription to stress but not to a specific disease mechanism\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The cellular function of MS4A6A was unknown; this work established a role in mast cells as a compensatory Fc\\u03b5RI\\u03b2-like protein supporting Fc\\u03b5RI surface expression and IgE-mediated degranulation.\",\n      \"evidence\": \"Exon-skipping of Fc\\u03b5RI\\u03b2 in human vs. mouse mast cells with degranulation and surface expression readouts\",\n      \"pmids\": [\"36424895\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism of Fc\\u03b5RI complex stabilization not defined at the molecular level\",\n        \"Relevance to non-mast-cell lineages (microglia, endothelium) not addressed\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"How MS4A proteins regulate TREM2 was unresolved; this preprint established that MS4A6A forms a complex with DAP12 to restrain TREM2 and that MS4A4A protects MS4A6A from degradation, negatively regulating microglial proliferation, metabolism, and phagocytosis.\",\n      \"evidence\": \"CRISPR KO and MS4A4A-degrading antibodies in primary human microglia, NHP, and amyloid model; Co-IP of MS4A6A\\u2013DAP12 (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.11.23.625001\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint version not yet peer-reviewed at deposition\",\n        \"Stoichiometry and structural basis of the MS4A4A\\u2013MS4A6A\\u2013DAP12 axis undefined\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The peer-reviewed study confirmed the MS4A4A\\u2013MS4A6A\\u2013DAP12 axis as a cooperative post-transcriptional negative regulator of both transmembrane and soluble TREM2, limiting microglial viability, phagocytosis, and lysosomal function.\",\n      \"evidence\": \"Reciprocal Co-IP, CRISPR KO plus antibody degradation, multiple model systems, and TREM2/phagocytosis/lysosomal readouts\",\n      \"pmids\": [\"41435829\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural model of how MS4A6A blocks DAP12-dependent TREM2 stabilization not resolved\",\n        \"Whether the DAP12 interaction underlies the mast-cell and endothelial roles is untested\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"In vivo causality in amyloid pathology was untested; ortholog knockout showed MS4A6A loss reduces amyloid phagocytosis and disinhibits NF-\\u03baB-driven neuroinflammation, while overexpression promotes plaque-associated gene programs.\",\n      \"evidence\": \"Ms4a6d knockout in APP/PS1 mice with phagocytosis, plaque burden, NF-\\u03baB, and behavioral readouts plus overexpression in human microglia\",\n      \"pmids\": [\"40877951\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Apparent contrast with the TREM2-restraining model not mechanistically reconciled\",\n        \"Direct link between NF-\\u03baB disinhibition and the DAP12/TREM2 axis not established\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Whether MS4A6A drives inflammation outside microglia was unknown; this work placed MS4A6A upstream of IKK/NF-\\u03baB in endothelial cells, promoting dysfunction and monocyte adhesion.\",\n      \"evidence\": \"siRNA silencing in ox-LDL-stimulated HUVECs with IKK inhibitor and IKK/I\\u03baB\\u03b1 epistasis plus ApoE-/- mouse model\",\n      \"pmids\": [\"40090082\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Molecular link between MS4A6A and IKK activation not defined\",\n        \"Single-lab finding without independent replication\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Complementing the locus genetics, CRISPRi knockdown in hiPSC microglia showed MS4A6A restrains pro-inflammatory states and modulates the disease-associated microglia (DAM) response.\",\n      \"evidence\": \"CRISPRi/CROP-seq in hiPSC-derived microglia with ROS and single-cell cluster analysis (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.03.09.642133\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint, single lab\",\n        \"Effector pathway linking knockdown to DAM-cluster shift not defined\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A coding/regulatory variant link to protein levels was needed; the rs7232 variant was associated with lower MS4A6A protein via proteasome-mediated degradation and altered plasma TREM2.\",\n      \"evidence\": \"Proteomics (OLINK), plasma TREM2 GWAS, and proteasome inhibition assays by rs7232 genotype\",\n      \"pmids\": [\"41552371\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Method details sparse and not independently confirmed\",\n        \"Causal chain from genotype to TREM2 not directly demonstrated\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MS4A6A reconciles its apparently opposing roles \\u2014 restraining TREM2 signaling versus supporting amyloid phagocytosis and Fc\\u03b5RI/IKK-driven inflammation across cell types \\u2014 remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structural model of the MS4A4A\\u2013MS4A6A\\u2013DAP12 complex\",\n        \"Cell-type-specific determinants of pro- vs. anti-inflammatory output unknown\",\n        \"Direct biochemical activity of MS4A6A beyond complex formation undefined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1, 3, 4]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MS4A4A\", \"DAP12\", \"TREM2\", \"FCER1B\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}