{"gene":"TREML4","run_date":"2026-04-28T21:42:59","timeline":{"discoveries":[{"year":2009,"finding":"TREML4 (Treml4) is a new TREM family member whose extracellular domain (fused to human IgG Fc) binds to late apoptotic or necrotic cells. It associates with the adaptor molecule DAP12 (DNAX activation protein 12 kDa) but not DAP10 or FcRγ. It is predominantly expressed on CD8α+ dendritic cells and splenic macrophages (red pulp and marginal metallophilic macrophages).","method":"Microarray identification, Fc-fusion protein binding assay to dying cells, new monoclonal antibody detection, co-immunoprecipitation with DAP12, flow cytometry and immunohistochemistry for localization","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (binding assay, Co-IP with adaptor, localization), single rigorous study","pmids":["19155473"],"is_preprint":false},{"year":2011,"finding":"Treml4 participates in antigen presentation in vivo: antigens (OVA, HIV GAGp24, HER2) engineered into anti-Treml4 monoclonal antibodies were efficiently presented to both CD8+ and CD4+ T cells, and anti-Treml4-GAGp24 induced Th1 responses and anti-tumor immunity. Loss of Treml4 (knockout mice) did not impair uptake of dying cells by CD8α+ DCs or cross-presentation, indicating functional redundancy for dead-cell uptake but a non-redundant role in targeted antigen delivery.","method":"Treml4 knockout mouse generation, in vivo antigen targeting with engineered anti-Treml4 antibody-antigen fusions, T cell priming assays, tumor challenge experiments","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with defined cellular phenotype plus antibody-targeting experiments with multiple antigens and orthogonal readouts","pmids":["22210914"],"is_preprint":false},{"year":2015,"finding":"TREML4 is an essential positive regulator of TLR7 signaling in macrophages. TREML4 deficiency impairs: (1) phosphorylation of STAT1 by p38 MAP kinase downstream of TLR7, and (2) recruitment of the adaptor MyD88 to TLR7. Loss of TREML4 reduces type I interferon production, inflammatory cytokines, and autoantibody production in lupus-prone MRL/lpr mice, and impairs antiviral response to influenza.","method":"Genome-scale shRNA screen, Treml4−/− mouse macrophage stimulation assays, phospho-STAT1/p38 western blotting, MyD88–TLR7 co-immunoprecipitation, in vivo lupus and influenza models","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 1-2 — unbiased genome-scale screen validated by KO mice, mechanistic biochemistry (Co-IP, phosphorylation assays), and in vivo disease models; multiple orthogonal methods","pmids":["25848864"],"is_preprint":false},{"year":2014,"finding":"TREML4 protein localizes to macrophages surrounding the necrotic core of coronary plaques complicated by calcification (but not in arteries with less advanced disease), and co-localizes with areas of microcalcification. rs2803496 acts as a TREML4 cis-eQTL with the minor allele conferring up to 6.5-fold increased relative risk of coronary artery calcification.","method":"Immunohistochemistry on human coronary plaques, von Kossa staining, RNA-seq eQTL analysis, integrative genomic/transcriptomic/proteomic strategy","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct protein localization in human tissue with functional disease association, but mechanistic pathway placement limited","pmids":["24975946"],"is_preprint":false},{"year":2020,"finding":"TREML4 regulates multiple aspects of innate immune cell function during polymicrobial sepsis: calcium homeostasis, inflammatory cytokine response, myeloperoxidase activation, endoplasmic reticulum stress response, and apoptotic cell death. Genetic ablation of Treml4 increased survival in both acute and chronic phases of sepsis in mice.","method":"Whole-genome CRISPR screen in mice, Treml4−/− mouse cecal ligation and puncture (CLP) sepsis model, calcium flux assays, cytokine measurement, myeloperoxidase activity assay, ER stress markers, apoptosis assays","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 1-2 — unbiased whole-genome CRISPR screen validated by KO mice with multiple orthogonal mechanistic readouts in defined disease model","pmids":["33020659"],"is_preprint":false},{"year":2020,"finding":"TREML4 expression in human M1 macrophages dysregulates inflammatory pathways related to leukocyte activation, apoptosis, and extracellular matrix degradation. In murine M1 macrophages, Treml4 controls expression of genes related to inflammation and lipid regulation; Treml4 deficiency in ApoE−/− mice reduces plaque burden, lesion complexity, macrophage content, and collagen deposition. In oxLDL-loaded macrophages, Treml4 represses genes related to carbohydrate, ion, and amino acid membrane transport, and its deficiency promotes beneficial iron homeostasis and glucose metabolism.","method":"Transcriptome analysis of human and murine macrophages with TREML4 manipulation, ApoE−/−/Treml4−/− double-knockout atherosclerosis model, metabolomic analysis, oxLDL treatment assays","journal":"Frontiers in immunology","confidence":"High","confidence_rationale":"Tier 2 — KO mouse in vivo disease model combined with transcriptomics and metabolomics across human and murine systems","pmids":["32292401"],"is_preprint":false},{"year":2022,"finding":"In pristane-induced lupus, TremL4 expression on Nr4a1-regulated Ly6Clo patrolling monocytes is regulated by Nr4a1 and is upregulated on novel CD138+ monocytes, which exuberantly produce TNFα in response to TLR7 stimulation. These Nr4a1-regulated Ly6Clo monocytes with high TremL4 expression were associated with diffuse alveolar hemorrhage susceptibility.","method":"Flow cytometry, genetic mouse models (Nr4a1-regulated monocyte tracking, pristane treatment), TLR7 stimulation assays, cytokine measurement, annexin-V staining","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct functional assays in genetic mouse models linking Treml4 to Nr4a1 regulation and TLR7 response, but no direct molecular mechanism of Nr4a1→Treml4 transcriptional regulation shown","pmids":["36264674"],"is_preprint":false},{"year":2023,"finding":"In diabetic keratitis, TREML4 is upregulated, and its siRNA-mediated knockdown protected T1DM corneas from Pseudomonas aeruginosa infection by suppressing necroptosis, placing TREML4 in a pathway that promotes RIPK3-dependent necroptotic cell death during bacterial infection.","method":"siRNA knockdown of Treml4 in mouse corneal infection model, RIPK3/caspase-8 inhibitor experiments, TUNEL staining, quantitative PCR, immunohistochemistry","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2-3 — KD with defined phenotypic rescue in vivo, pathway placement via inhibitor epistasis, but mechanistic link between TREML4 and RIPK3 not directly established","pmids":["37279395"],"is_preprint":false},{"year":2016,"finding":"TREML4 marks a committed Ly6Chi monocyte subset: Ly6Chi TREML4+ monocytes are committed to differentiate into Ly6Clo TREML4+ monocytes and cannot differentiate into Zbtb46+ monocyte-derived DCs capable of cross-priming, whereas Ly6Chi TREML4− monocytes can differentiate into cross-priming Mo-DCs in response to GM-CSF and IL-4.","method":"Cell sorting of TREML4+ vs TREML4− monocyte subsets, in vitro differentiation assays with GM-CSF/IL-4, flow cytometry, Zbtb46-GFP reporter mice","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 — prospective cell sorting and functional differentiation assays establish TREML4 as a lineage commitment marker with functional consequence","pmids":["27264183"],"is_preprint":false},{"year":2023,"finding":"NOTCH2 signaling (via DLL1) induces the transition of Ly6Chi TREML4− monocytes into Ly6Clo TREML4+ monocytes in vitro, and this transition requires IRF2 but can occur independently of NUR77 or BCL6, establishing a transcriptional hierarchy for Ly6Clo monocyte development in which TREML4 marks the mature nonclassical subset.","method":"In vitro NOTCH2/DLL1 differentiation assay, conditional knockout mice (BCL6, IRF2, NUR77 deletion from myeloid progenitors), flow cytometry tracking of TREML4 expression","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro reconstitution of differentiation step with genetic dissection of transcription factor requirements, TREML4 used as phenotypic marker of commitment","pmids":["37607223"],"is_preprint":false}],"current_model":"TREML4 is a DAP12-associated TREM family receptor expressed on myeloid cells (macrophages and dendritic cell subsets) that binds dead/necrotic cells, amplifies TLR7 signaling by facilitating MyD88 recruitment to TLR7 and downstream p38-STAT1 phosphorylation to drive type I interferon and inflammatory cytokine production, regulates calcium homeostasis and ER stress-linked apoptosis during sepsis, promotes inflammatory gene programs in macrophages relevant to atherosclerosis, and marks committed Ly6Clo nonclassical monocytes whose development is controlled by NOTCH2-IRF2 signaling."},"narrative":{"teleology":[{"year":2009,"claim":"Identification of TREML4 as a new TREM family receptor that binds dead cells and signals through DAP12 established its molecular identity as an activating innate immune receptor on specific myeloid cell subsets.","evidence":"Fc-fusion binding assay to apoptotic/necrotic cells, co-immunoprecipitation with DAP12, flow cytometry and immunohistochemistry on splenic macrophages and CD8α+ DCs","pmids":["19155473"],"confidence":"High","gaps":["Ligand(s) on dead cells not molecularly identified","Signaling downstream of DAP12 engagement not characterized","Function beyond dead-cell recognition unknown"]},{"year":2011,"claim":"Knockout mouse studies showed TREML4 is dispensable for dead-cell uptake and cross-presentation by CD8α+ DCs but can serve as an efficient antigen-delivery receptor for T cell priming, defining its non-redundant role in targeted antigen delivery rather than scavenging.","evidence":"Treml4 KO mice, anti-Treml4 antibody–antigen fusion targeting in vivo, T cell priming and tumor challenge experiments","pmids":["22210914"],"confidence":"High","gaps":["Mechanism by which anti-Treml4 targeting enhances antigen presentation not resolved at molecular level","Contribution to natural antigen presentation in physiological settings unclear"]},{"year":2014,"claim":"Localization of TREML4 protein to macrophages within necrotic cores of calcified coronary plaques, together with a cis-eQTL conferring increased coronary calcification risk, linked TREML4 to human atherosclerotic disease.","evidence":"Immunohistochemistry on human coronary arteries, eQTL analysis of rs2803496","pmids":["24975946"],"confidence":"Medium","gaps":["Causal mechanism connecting TREML4 expression to calcification not established","eQTL association not functionally validated by gene perturbation in human cells"]},{"year":2015,"claim":"An unbiased shRNA screen and KO validation revealed TREML4 as an essential amplifier of TLR7 signaling by promoting MyD88 recruitment to TLR7 and enabling p38–STAT1 phosphorylation, establishing its central signaling mechanism in type I interferon production and autoimmunity.","evidence":"Genome-scale shRNA screen, Treml4−/− macrophage stimulation, Co-IP of MyD88–TLR7, phospho-blotting, MRL/lpr lupus and influenza models","pmids":["25848864"],"confidence":"High","gaps":["Physical interaction between TREML4 and TLR7 not demonstrated","How DAP12 association connects to MyD88 recruitment mechanistically unclear","Whether TREML4 amplifies other TLR pathways untested"]},{"year":2016,"claim":"Prospective sorting demonstrated that TREML4 expression marks a committed Ly6Chi monocyte subset fated to become Ly6Clo nonclassical monocytes, separating it from progenitors that can generate cross-priming monocyte-derived DCs.","evidence":"TREML4+/− monocyte subset sorting, GM-CSF/IL-4 differentiation assays, Zbtb46-GFP reporter mice","pmids":["27264183"],"confidence":"Medium","gaps":["Whether TREML4 is functionally required for the Ly6Chi-to-Ly6Clo transition or merely a marker not resolved","Transcriptional regulation of TREML4 during monocyte commitment not identified"]},{"year":2020,"claim":"Two studies expanded TREML4's pathophysiological roles: a CRISPR screen showed TREML4 controls calcium homeostasis, ER stress, and apoptosis during sepsis (with KO mice surviving longer), while double-KO atherosclerosis models showed TREML4 drives inflammatory and lipid-regulatory gene programs in macrophages that promote plaque formation.","evidence":"Whole-genome CRISPR screen with CLP sepsis model, Treml4−/− calcium/ER stress/apoptosis assays; ApoE−/−Treml4−/− atherosclerosis model, transcriptomics, metabolomics","pmids":["33020659","32292401"],"confidence":"High","gaps":["Direct molecular targets linking TREML4 to calcium flux and ER stress pathways not identified","Contribution of TLR7 amplification versus other TREML4 functions to sepsis and atherosclerosis phenotypes not dissected"]},{"year":2022,"claim":"TREML4 was found to be upregulated on Nr4a1-regulated CD138+ Ly6Clo monocytes that produce exuberant TNFα upon TLR7 stimulation, linking TREML4-high patrolling monocytes to lupus-associated diffuse alveolar hemorrhage.","evidence":"Flow cytometry in pristane-induced lupus, Nr4a1-regulated monocyte genetic tracking, TLR7 stimulation assays","pmids":["36264674"],"confidence":"Medium","gaps":["Whether Nr4a1 directly regulates Treml4 transcription not shown","Functional requirement for TREML4 in hemorrhage pathogenesis not tested by loss-of-function"]},{"year":2023,"claim":"Two studies further defined TREML4 biology: NOTCH2/DLL1 signaling was shown to drive the Ly6Chi-to-Ly6Clo TREML4+ monocyte transition in an IRF2-dependent manner, while TREML4 knockdown in diabetic keratitis suppressed RIPK3-dependent necroptosis, placing TREML4 upstream of necroptotic cell death.","evidence":"In vitro NOTCH2/DLL1 differentiation assay with conditional KO mice (IRF2, NUR77, BCL6); siRNA knockdown in mouse corneal infection model with RIPK3 inhibitor epistasis","pmids":["37607223","37279395"],"confidence":"Medium","gaps":["Whether NOTCH2-IRF2 directly induces Treml4 transcription or acts indirectly not established","Direct biochemical link between TREML4 and RIPK3/necroptosis machinery not demonstrated","Relevance of TREML4-necroptosis axis beyond corneal infection unknown"]},{"year":null,"claim":"Key unresolved questions include the identity of the molecular ligand(s) on dead cells recognized by TREML4, the structural basis of TREML4–DAP12 signaling, the direct physical relationship between TREML4 and TLR7, and whether TREML4 has signaling functions independent of TLR7 amplification.","evidence":"","pmids":[],"confidence":"High","gaps":["No crystal structure or cryo-EM model of TREML4 or TREML4–DAP12 complex","Dead-cell ligand identity unknown","No direct TREML4–TLR7 physical interaction demonstrated","Human genetic loss-of-function studies absent"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,2]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,4]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,8]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,2,4,6]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,4]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[4,7]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[3,5]}],"complexes":[],"partners":["DAP12","TLR7","MYD88"],"other_free_text":[]},"mechanistic_narrative":"TREML4 is a DAP12-associated activating receptor of the TREM family expressed on macrophages and dendritic cell subsets that functions as a positive regulator of innate immune signaling, myeloid cell differentiation, and inflammatory responses. Its extracellular domain binds late apoptotic and necrotic cells, and it amplifies TLR7 signaling by facilitating MyD88 recruitment to TLR7 and promoting p38-dependent STAT1 phosphorylation, thereby driving type I interferon and inflammatory cytokine production critical for antiviral defense and lupus pathogenesis [PMID:19155473, PMID:25848864]. During sepsis, TREML4 regulates calcium homeostasis, ER stress, and apoptotic cell death, and its genetic ablation improves survival; in atherosclerosis, it promotes inflammatory gene programs in macrophages and its deficiency reduces plaque burden in ApoE-deficient mice [PMID:33020659, PMID:32292401]. TREML4 also serves as a lineage commitment marker distinguishing Ly6Chi monocytes fated to become Ly6Clo nonclassical monocytes, a transition driven by NOTCH2-DLL1 signaling and dependent on IRF2 [PMID:27264183, PMID:37607223]."},"prefetch_data":{"uniprot":{"accession":"Q6UXN2","full_name":"Trem-like transcript 4 protein","aliases":["Triggering receptor expressed on myeloid cells-like protein 4"],"length_aa":200,"mass_kda":21.9,"function":"Positively regulates Toll-like receptor TLR7 signaling in macrophages","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q6UXN2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TREML4","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/TREML4","total_profiled":1310},"omim":[{"mim_id":"614664","title":"TRIGGERING RECEPTOR EXPRESSED ON MYELOID CELLS-LIKE PROTEIN 4; TREML4","url":"https://www.omim.org/entry/614664"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"choroid plexus","ntpm":1.9}],"url":"https://www.proteinatlas.org/search/TREML4"},"hgnc":{"alias_symbol":["TLT4"],"prev_symbol":[]},"alphafold":{"accession":"Q6UXN2","domains":[{"cath_id":"2.60.40.10","chopping":"35-132","consensus_level":"high","plddt":96.8682,"start":35,"end":132}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6UXN2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q6UXN2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q6UXN2-F1-predicted_aligned_error_v6.png","plddt_mean":76.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TREML4","jax_strain_url":"https://www.jax.org/strain/search?query=TREML4"},"sequence":{"accession":"Q6UXN2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q6UXN2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q6UXN2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6UXN2"}},"corpus_meta":[{"pmid":"27264183","id":"PMC_27264183","title":"Distinct Transcriptional Programs Control Cross-Priming in Classical and Monocyte-Derived Dendritic Cells.","date":"2016","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/27264183","citation_count":169,"is_preprint":false},{"pmid":"25848864","id":"PMC_25848864","title":"The receptor TREML4 amplifies TLR7-mediated signaling during antiviral responses and autoimmunity.","date":"2015","source":"Nature immunology","url":"https://pubmed.ncbi.nlm.nih.gov/25848864","citation_count":60,"is_preprint":false},{"pmid":"33020659","id":"PMC_33020659","title":"TREML4 receptor regulates inflammation and innate immune cell death during polymicrobial sepsis.","date":"2020","source":"Nature immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33020659","citation_count":57,"is_preprint":false},{"pmid":"23535507","id":"PMC_23535507","title":"Novel genes detected by transcriptional profiling from whole-blood cells in patients with early onset of acute coronary syndrome.","date":"2013","source":"Clinica chimica acta; international journal of clinical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23535507","citation_count":52,"is_preprint":false},{"pmid":"29284304","id":"PMC_29284304","title":"Altered Long Non-Coding RNA Transcriptomic Profiles in Ischemic Stroke.","date":"2018","source":"Human gene therapy","url":"https://pubmed.ncbi.nlm.nih.gov/29284304","citation_count":49,"is_preprint":false},{"pmid":"19155473","id":"PMC_19155473","title":"A new triggering receptor expressed on myeloid cells (Trem) family member, Trem-like 4, binds to dead cells and is a DNAX activation protein 12-linked marker for subsets of mouse macrophages and dendritic cells.","date":"2009","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/19155473","citation_count":47,"is_preprint":false},{"pmid":"33108347","id":"PMC_33108347","title":"A longitudinal and transancestral analysis of DNA methylation patterns and disease activity in lupus patients.","date":"2020","source":"JCI insight","url":"https://pubmed.ncbi.nlm.nih.gov/33108347","citation_count":44,"is_preprint":false},{"pmid":"22210914","id":"PMC_22210914","title":"Treml4, an Ig superfamily member, mediates presentation of several antigens to T cells in vivo, including protective immunity to HER2 protein.","date":"2011","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/22210914","citation_count":35,"is_preprint":false},{"pmid":"27084067","id":"PMC_27084067","title":"Mutation analysis of the MS4A and TREM gene clusters in a case-control Alzheimer's disease data set.","date":"2016","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/27084067","citation_count":32,"is_preprint":false},{"pmid":"30538480","id":"PMC_30538480","title":"Aberrantly expressed long noncoding RNAs and genes in Parkinson's disease.","date":"2018","source":"Neuropsychiatric disease and 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It associates with the adaptor molecule DAP12 (DNAX activation protein 12 kDa) but not DAP10 or FcRγ. It is predominantly expressed on CD8α+ dendritic cells and splenic macrophages (red pulp and marginal metallophilic macrophages).\",\n      \"method\": \"Microarray identification, Fc-fusion protein binding assay to dying cells, new monoclonal antibody detection, co-immunoprecipitation with DAP12, flow cytometry and immunohistochemistry for localization\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (binding assay, Co-IP with adaptor, localization), single rigorous study\",\n      \"pmids\": [\"19155473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Treml4 participates in antigen presentation in vivo: antigens (OVA, HIV GAGp24, HER2) engineered into anti-Treml4 monoclonal antibodies were efficiently presented to both CD8+ and CD4+ T cells, and anti-Treml4-GAGp24 induced Th1 responses and anti-tumor immunity. Loss of Treml4 (knockout mice) did not impair uptake of dying cells by CD8α+ DCs or cross-presentation, indicating functional redundancy for dead-cell uptake but a non-redundant role in targeted antigen delivery.\",\n      \"method\": \"Treml4 knockout mouse generation, in vivo antigen targeting with engineered anti-Treml4 antibody-antigen fusions, T cell priming assays, tumor challenge experiments\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with defined cellular phenotype plus antibody-targeting experiments with multiple antigens and orthogonal readouts\",\n      \"pmids\": [\"22210914\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TREML4 is an essential positive regulator of TLR7 signaling in macrophages. TREML4 deficiency impairs: (1) phosphorylation of STAT1 by p38 MAP kinase downstream of TLR7, and (2) recruitment of the adaptor MyD88 to TLR7. Loss of TREML4 reduces type I interferon production, inflammatory cytokines, and autoantibody production in lupus-prone MRL/lpr mice, and impairs antiviral response to influenza.\",\n      \"method\": \"Genome-scale shRNA screen, Treml4−/− mouse macrophage stimulation assays, phospho-STAT1/p38 western blotting, MyD88–TLR7 co-immunoprecipitation, in vivo lupus and influenza models\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — unbiased genome-scale screen validated by KO mice, mechanistic biochemistry (Co-IP, phosphorylation assays), and in vivo disease models; multiple orthogonal methods\",\n      \"pmids\": [\"25848864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TREML4 protein localizes to macrophages surrounding the necrotic core of coronary plaques complicated by calcification (but not in arteries with less advanced disease), and co-localizes with areas of microcalcification. rs2803496 acts as a TREML4 cis-eQTL with the minor allele conferring up to 6.5-fold increased relative risk of coronary artery calcification.\",\n      \"method\": \"Immunohistochemistry on human coronary plaques, von Kossa staining, RNA-seq eQTL analysis, integrative genomic/transcriptomic/proteomic strategy\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct protein localization in human tissue with functional disease association, but mechanistic pathway placement limited\",\n      \"pmids\": [\"24975946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TREML4 regulates multiple aspects of innate immune cell function during polymicrobial sepsis: calcium homeostasis, inflammatory cytokine response, myeloperoxidase activation, endoplasmic reticulum stress response, and apoptotic cell death. Genetic ablation of Treml4 increased survival in both acute and chronic phases of sepsis in mice.\",\n      \"method\": \"Whole-genome CRISPR screen in mice, Treml4−/− mouse cecal ligation and puncture (CLP) sepsis model, calcium flux assays, cytokine measurement, myeloperoxidase activity assay, ER stress markers, apoptosis assays\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — unbiased whole-genome CRISPR screen validated by KO mice with multiple orthogonal mechanistic readouts in defined disease model\",\n      \"pmids\": [\"33020659\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TREML4 expression in human M1 macrophages dysregulates inflammatory pathways related to leukocyte activation, apoptosis, and extracellular matrix degradation. In murine M1 macrophages, Treml4 controls expression of genes related to inflammation and lipid regulation; Treml4 deficiency in ApoE−/− mice reduces plaque burden, lesion complexity, macrophage content, and collagen deposition. In oxLDL-loaded macrophages, Treml4 represses genes related to carbohydrate, ion, and amino acid membrane transport, and its deficiency promotes beneficial iron homeostasis and glucose metabolism.\",\n      \"method\": \"Transcriptome analysis of human and murine macrophages with TREML4 manipulation, ApoE−/−/Treml4−/− double-knockout atherosclerosis model, metabolomic analysis, oxLDL treatment assays\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse in vivo disease model combined with transcriptomics and metabolomics across human and murine systems\",\n      \"pmids\": [\"32292401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In pristane-induced lupus, TremL4 expression on Nr4a1-regulated Ly6Clo patrolling monocytes is regulated by Nr4a1 and is upregulated on novel CD138+ monocytes, which exuberantly produce TNFα in response to TLR7 stimulation. These Nr4a1-regulated Ly6Clo monocytes with high TremL4 expression were associated with diffuse alveolar hemorrhage susceptibility.\",\n      \"method\": \"Flow cytometry, genetic mouse models (Nr4a1-regulated monocyte tracking, pristane treatment), TLR7 stimulation assays, cytokine measurement, annexin-V staining\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct functional assays in genetic mouse models linking Treml4 to Nr4a1 regulation and TLR7 response, but no direct molecular mechanism of Nr4a1→Treml4 transcriptional regulation shown\",\n      \"pmids\": [\"36264674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In diabetic keratitis, TREML4 is upregulated, and its siRNA-mediated knockdown protected T1DM corneas from Pseudomonas aeruginosa infection by suppressing necroptosis, placing TREML4 in a pathway that promotes RIPK3-dependent necroptotic cell death during bacterial infection.\",\n      \"method\": \"siRNA knockdown of Treml4 in mouse corneal infection model, RIPK3/caspase-8 inhibitor experiments, TUNEL staining, quantitative PCR, immunohistochemistry\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — KD with defined phenotypic rescue in vivo, pathway placement via inhibitor epistasis, but mechanistic link between TREML4 and RIPK3 not directly established\",\n      \"pmids\": [\"37279395\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TREML4 marks a committed Ly6Chi monocyte subset: Ly6Chi TREML4+ monocytes are committed to differentiate into Ly6Clo TREML4+ monocytes and cannot differentiate into Zbtb46+ monocyte-derived DCs capable of cross-priming, whereas Ly6Chi TREML4− monocytes can differentiate into cross-priming Mo-DCs in response to GM-CSF and IL-4.\",\n      \"method\": \"Cell sorting of TREML4+ vs TREML4− monocyte subsets, in vitro differentiation assays with GM-CSF/IL-4, flow cytometry, Zbtb46-GFP reporter mice\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — prospective cell sorting and functional differentiation assays establish TREML4 as a lineage commitment marker with functional consequence\",\n      \"pmids\": [\"27264183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NOTCH2 signaling (via DLL1) induces the transition of Ly6Chi TREML4− monocytes into Ly6Clo TREML4+ monocytes in vitro, and this transition requires IRF2 but can occur independently of NUR77 or BCL6, establishing a transcriptional hierarchy for Ly6Clo monocyte development in which TREML4 marks the mature nonclassical subset.\",\n      \"method\": \"In vitro NOTCH2/DLL1 differentiation assay, conditional knockout mice (BCL6, IRF2, NUR77 deletion from myeloid progenitors), flow cytometry tracking of TREML4 expression\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro reconstitution of differentiation step with genetic dissection of transcription factor requirements, TREML4 used as phenotypic marker of commitment\",\n      \"pmids\": [\"37607223\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TREML4 is a DAP12-associated TREM family receptor expressed on myeloid cells (macrophages and dendritic cell subsets) that binds dead/necrotic cells, amplifies TLR7 signaling by facilitating MyD88 recruitment to TLR7 and downstream p38-STAT1 phosphorylation to drive type I interferon and inflammatory cytokine production, regulates calcium homeostasis and ER stress-linked apoptosis during sepsis, promotes inflammatory gene programs in macrophages relevant to atherosclerosis, and marks committed Ly6Clo nonclassical monocytes whose development is controlled by NOTCH2-IRF2 signaling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TREML4 is a DAP12-associated activating receptor of the TREM family expressed on macrophages and dendritic cell subsets that functions as a positive regulator of innate immune signaling, myeloid cell differentiation, and inflammatory responses. Its extracellular domain binds late apoptotic and necrotic cells, and it amplifies TLR7 signaling by facilitating MyD88 recruitment to TLR7 and promoting p38-dependent STAT1 phosphorylation, thereby driving type I interferon and inflammatory cytokine production critical for antiviral defense and lupus pathogenesis [PMID:19155473, PMID:25848864]. During sepsis, TREML4 regulates calcium homeostasis, ER stress, and apoptotic cell death, and its genetic ablation improves survival; in atherosclerosis, it promotes inflammatory gene programs in macrophages and its deficiency reduces plaque burden in ApoE-deficient mice [PMID:33020659, PMID:32292401]. TREML4 also serves as a lineage commitment marker distinguishing Ly6Chi monocytes fated to become Ly6Clo nonclassical monocytes, a transition driven by NOTCH2-DLL1 signaling and dependent on IRF2 [PMID:27264183, PMID:37607223].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Identification of TREML4 as a new TREM family receptor that binds dead cells and signals through DAP12 established its molecular identity as an activating innate immune receptor on specific myeloid cell subsets.\",\n      \"evidence\": \"Fc-fusion binding assay to apoptotic/necrotic cells, co-immunoprecipitation with DAP12, flow cytometry and immunohistochemistry on splenic macrophages and CD8α+ DCs\",\n      \"pmids\": [\"19155473\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ligand(s) on dead cells not molecularly identified\", \"Signaling downstream of DAP12 engagement not characterized\", \"Function beyond dead-cell recognition unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Knockout mouse studies showed TREML4 is dispensable for dead-cell uptake and cross-presentation by CD8α+ DCs but can serve as an efficient antigen-delivery receptor for T cell priming, defining its non-redundant role in targeted antigen delivery rather than scavenging.\",\n      \"evidence\": \"Treml4 KO mice, anti-Treml4 antibody–antigen fusion targeting in vivo, T cell priming and tumor challenge experiments\",\n      \"pmids\": [\"22210914\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which anti-Treml4 targeting enhances antigen presentation not resolved at molecular level\", \"Contribution to natural antigen presentation in physiological settings unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Localization of TREML4 protein to macrophages within necrotic cores of calcified coronary plaques, together with a cis-eQTL conferring increased coronary calcification risk, linked TREML4 to human atherosclerotic disease.\",\n      \"evidence\": \"Immunohistochemistry on human coronary arteries, eQTL analysis of rs2803496\",\n      \"pmids\": [\"24975946\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal mechanism connecting TREML4 expression to calcification not established\", \"eQTL association not functionally validated by gene perturbation in human cells\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"An unbiased shRNA screen and KO validation revealed TREML4 as an essential amplifier of TLR7 signaling by promoting MyD88 recruitment to TLR7 and enabling p38–STAT1 phosphorylation, establishing its central signaling mechanism in type I interferon production and autoimmunity.\",\n      \"evidence\": \"Genome-scale shRNA screen, Treml4−/− macrophage stimulation, Co-IP of MyD88–TLR7, phospho-blotting, MRL/lpr lupus and influenza models\",\n      \"pmids\": [\"25848864\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physical interaction between TREML4 and TLR7 not demonstrated\", \"How DAP12 association connects to MyD88 recruitment mechanistically unclear\", \"Whether TREML4 amplifies other TLR pathways untested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Prospective sorting demonstrated that TREML4 expression marks a committed Ly6Chi monocyte subset fated to become Ly6Clo nonclassical monocytes, separating it from progenitors that can generate cross-priming monocyte-derived DCs.\",\n      \"evidence\": \"TREML4+/− monocyte subset sorting, GM-CSF/IL-4 differentiation assays, Zbtb46-GFP reporter mice\",\n      \"pmids\": [\"27264183\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether TREML4 is functionally required for the Ly6Chi-to-Ly6Clo transition or merely a marker not resolved\", \"Transcriptional regulation of TREML4 during monocyte commitment not identified\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Two studies expanded TREML4's pathophysiological roles: a CRISPR screen showed TREML4 controls calcium homeostasis, ER stress, and apoptosis during sepsis (with KO mice surviving longer), while double-KO atherosclerosis models showed TREML4 drives inflammatory and lipid-regulatory gene programs in macrophages that promote plaque formation.\",\n      \"evidence\": \"Whole-genome CRISPR screen with CLP sepsis model, Treml4−/− calcium/ER stress/apoptosis assays; ApoE−/−Treml4−/− atherosclerosis model, transcriptomics, metabolomics\",\n      \"pmids\": [\"33020659\", \"32292401\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular targets linking TREML4 to calcium flux and ER stress pathways not identified\", \"Contribution of TLR7 amplification versus other TREML4 functions to sepsis and atherosclerosis phenotypes not dissected\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"TREML4 was found to be upregulated on Nr4a1-regulated CD138+ Ly6Clo monocytes that produce exuberant TNFα upon TLR7 stimulation, linking TREML4-high patrolling monocytes to lupus-associated diffuse alveolar hemorrhage.\",\n      \"evidence\": \"Flow cytometry in pristane-induced lupus, Nr4a1-regulated monocyte genetic tracking, TLR7 stimulation assays\",\n      \"pmids\": [\"36264674\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether Nr4a1 directly regulates Treml4 transcription not shown\", \"Functional requirement for TREML4 in hemorrhage pathogenesis not tested by loss-of-function\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Two studies further defined TREML4 biology: NOTCH2/DLL1 signaling was shown to drive the Ly6Chi-to-Ly6Clo TREML4+ monocyte transition in an IRF2-dependent manner, while TREML4 knockdown in diabetic keratitis suppressed RIPK3-dependent necroptosis, placing TREML4 upstream of necroptotic cell death.\",\n      \"evidence\": \"In vitro NOTCH2/DLL1 differentiation assay with conditional KO mice (IRF2, NUR77, BCL6); siRNA knockdown in mouse corneal infection model with RIPK3 inhibitor epistasis\",\n      \"pmids\": [\"37607223\", \"37279395\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether NOTCH2-IRF2 directly induces Treml4 transcription or acts indirectly not established\", \"Direct biochemical link between TREML4 and RIPK3/necroptosis machinery not demonstrated\", \"Relevance of TREML4-necroptosis axis beyond corneal infection unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the molecular ligand(s) on dead cells recognized by TREML4, the structural basis of TREML4–DAP12 signaling, the direct physical relationship between TREML4 and TLR7, and whether TREML4 has signaling functions independent of TLR7 amplification.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal structure or cryo-EM model of TREML4 or TREML4–DAP12 complex\", \"Dead-cell ligand identity unknown\", \"No direct TREML4–TLR7 physical interaction demonstrated\", \"Human genetic loss-of-function studies absent\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 2, 4, 6]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [4, 7]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [3, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"DAP12\", \"TLR7\", \"MYD88\"],\n    \"other_free_text\": []\n  }\n}\n```"}