{"gene":"ADA2","run_date":"2026-06-09T22:02:40","timeline":{"discoveries":[{"year":2005,"finding":"ADA2 (CECR1) was identified as a member of the ADGF (adenosine deaminase-related growth factor) family and shown to be a heparin-binding protein with adenosine deaminase activity; purification via heparin affinity demonstrated its biochemical properties including activity at acidic pH and elevated adenosine concentrations.","method":"Heparin-affinity purification, enzyme activity assays, biochemical characterization","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzyme assay and biochemical purification, single lab, single study","pmids":["15926889"],"is_preprint":false},{"year":2010,"finding":"Crystal structures of human ADA2 and ADA2 bound to a transition-state analogue revealed the structural basis of catalytic activity: ADA2 contains a catalytic domain plus two ADGF/ADA2-specific domains of novel folds mediating protein dimerization and binding to cell-surface receptors. Extensive glycosylation and a conserved disulfide bond indicate extracellular function. The substrate-binding pocket of ADA2 differs substantially from ADA1, explaining distinct substrate and inhibitor specificities.","method":"X-ray crystallography, transition-state analogue co-crystal structure, structural comparison","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation, multiple structural features resolved in one rigorous study","pmids":["20147294"],"is_preprint":false},{"year":2014,"finding":"Loss-of-function mutations in CECR1 (encoding ADA2) cause a syndrome of vasculopathy, stroke, and inflammation. Patients had markedly reduced ADA2 protein levels and ADA2-specific enzymatic activity. Morpholino knockdown of zebrafish ADA2 homologue caused intracranial hemorrhages and neutropenia; these phenotypes were rescued by co-injection with wild-type but not mutant human CECR1, establishing a direct causal link. Monocytes from patients induced endothelial cell layer damage in co-culture.","method":"Whole-exome sequencing, enzyme activity assay, zebrafish morpholino knockdown, co-culture endothelial damage assay, immunoblotting","journal":"The New England journal of medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (genetic, biochemical, zebrafish in vivo rescue), replicated across multiple patients","pmids":["24552284"],"is_preprint":false},{"year":2016,"finding":"ADA2 binds to distinct subsets of immune cells that lack CD26 (the ADA1 receptor), including neutrophils, monocytes (preferentially CD16+ monocytes), NK cells, B cells, and CD39+ regulatory T cells; this cell-surface binding is separate from ADA1 binding, suggesting ADA2 regulates activation and survival of immune cells anchored to the cell surface.","method":"Flow cytometry binding assays with recombinant ADA2, analysis of patient blood samples","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay on multiple immune cell subsets, single lab but multiple orthogonal approaches","pmids":["27663683"],"is_preprint":false},{"year":2007,"finding":"In Xenopus, CECR1/ADGF orthologs exhibit adenosine deaminase activity that is indispensable for their growth factor activity; knockdown caused developmental defects recapitulated by exogenous adenosine or P1 receptor agonists, placing ADA2 function upstream of adenosine/P1 receptor signaling in embryogenesis.","method":"Morpholino oligonucleotide knockdown in Xenopus, recombinant protein enzyme assay, adenosine/P1 receptor agonist injection, developmental marker gene expression","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis by morpholino plus pharmacological rescue, single lab, ortholog model","pmids":["18032387"],"is_preprint":false},{"year":2017,"finding":"In glioblastoma, macrophage-expressed CECR1 (ADA2) promotes neovascularization by upregulating PDGFB mRNA and protein in macrophages, which then activates pericyte PDGFRβ signaling in a paracrine manner, promoting pericyte migration and periostin deposition; siRNA knockdown of CECR1 in macrophages reduced vessel formation in a 3D co-culture system.","method":"siRNA knockdown, recombinant protein stimulation, 3D co-culture angiogenesis assay, transwell migration assay, qRT-PCR, immunohistochemistry","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss and gain of function with defined molecular pathway (PDGFB-PDGFRβ), single lab, multiple orthogonal methods","pmids":["28534507"],"is_preprint":false},{"year":2017,"finding":"CECR1 in M2-like tumor-associated macrophages regulates macrophage M2 polarization and exerts paracrine effects on glioma cells via MAPK signaling; CECR1 knockdown or stimulation of macrophages altered M2 phenotype markers and affected tumor cell proliferation and migration.","method":"siRNA knockdown, conditioned medium transfer, flow cytometry, immunohistochemistry, in vitro proliferation and migration assays","journal":"Neuro-oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss and gain of function with pathway readout (MAPK), single lab, multiple methods","pmids":["28453746"],"is_preprint":false},{"year":2000,"finding":"CECR1 encodes a protein with sequence similarity to insect growth factors (IDGF from flesh fly, MDGF from sea hare) and is alternatively spliced; it is expressed in developing heart outflow tract, cranial nerve ganglia, and notochord, suggesting a developmental role.","method":"Exon trapping, RT-PCR, Northern blot, in situ hybridization on human embryo","journal":"Genomics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — expression/localization data only, no functional mechanistic experiment, single study","pmids":["10756095"],"is_preprint":false},{"year":2005,"finding":"Transgenic overexpression of CECR1 adenosine deaminase in mice under cardiac-specific (myosin heavy chain) or ubiquitous (beta-actin) promoters caused heart enlargement, high rates of embryonic and neonatal lethality, and kidney and eye abnormalities, demonstrating that CECR1 gain-of-function disrupts heart and kidney development.","method":"Transgenic mouse generation, cardiac and ubiquitous promoter-driven overexpression, morphological and histological analysis","journal":"Transgenic research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct in vivo gain-of-function with defined organ phenotypes, single lab","pmids":["16145841"],"is_preprint":false},{"year":2018,"finding":"A pathogenic mutation in DADA2 affecting a consensus N-linked glycosylation sequence disrupts glycosylation of ADA2, establishing that N-linked glycosylation is essential for normal ADA2 biology (protein stability/secretion).","method":"Identification of novel mutation, biochemical analysis of glycosylation defect","journal":"The Journal of allergy and clinical immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct experiment on patient-derived variant demonstrating glycosylation requirement, single study","pmids":["29936104"],"is_preprint":false},{"year":2024,"finding":"ADA2 localizes within lysosomes (targeted via glycan modifications) and interacts with DNA molecules, editing deoxyadenosine (dA) to deoxyinosine (dI) in DNA; this lysosomal DNA-editing activity modulates TLR9 activation, regulating innate immune sensing of nucleic acids. Data suggest DNA rather than free adenosine is the physiological substrate.","method":"Subcellular fractionation/localization studies, DNA-binding assays, in vitro deamination assays on DNA substrates, TLR9 reporter assays, glycan modification experiments","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (localization, substrate assay, functional TLR9 assay), single lab","pmids":["39441717"],"is_preprint":false},{"year":2024,"finding":"In a zebrafish cecr1b loss-of-function model, ADA2 deficiency disrupts hematopoietic stem cell specification and causes defective hematopoiesis via induction of inflammation in the vascular endothelium; pharmacological blockade of inflammation, modulation of the adenosine A2 receptor (A2bR) pathway, or administration of recombinant human ADA2 corrected these hematopoietic defects, placing ADA2 upstream of A2bR signaling in hematopoiesis regulation.","method":"Zebrafish cecr1b loss-of-function model, pharmacological rescue (A2R pathway modulation, anti-inflammatory agents), recombinant human ADA2 administration, hematopoietic assays","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic model with multiple independent rescue strategies and pathway placement, single lab but multiple orthogonal methods","pmids":["38777862"],"is_preprint":false},{"year":2025,"finding":"Specific ADA2 missense variants (p.G47A, p.G47R, p.G47V, p.R169Q, p.E328K, p.H424N, p.Y453C) exert dominant-negative effects on ADA2 enzymatic activity, dimerization, and/or secretion; in vitro analysis showed these variants form large intracellular protein aggregates via disulfide bond formation at Cys408.","method":"Transfected cell expression assays, enzyme activity assays, western blotting, protein aggregation analysis","journal":"The Journal of experimental medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional cell-based assays with multiple variants, mechanistic finding of disulfide-mediated aggregation, single lab","pmids":["40864493"],"is_preprint":false},{"year":2024,"finding":"Dominant-negative ADA2 missense variants disrupt ADA2 enzymatic activity, dimerization, and/or secretion; these variants can cause DADA2 in heterozygous carriers, demonstrating that ADA2 protein function requires proper dimerization and secretion.","method":"Overexpression in 293T cells, enzyme activity assay, western blotting, patient cohort analysis","journal":"medRxiv","confidence":"Low","confidence_rationale":"Tier 2 / Weak — preprint, single lab, overlaps with peer-reviewed version (PMID:40864493)","pmids":["39711711"],"is_preprint":true},{"year":2025,"finding":"In vitro analysis of DADA2-associated ADA2 missense variants shows that residual ADA2 activity correlates with hypomorphic alleles; variants can synergistically disrupt protein function via intracellular aggregate formation mediated by disulfide bonds at Cys408.","method":"Overexpression in 293T cells, enzyme activity assay, western blotting","journal":"Arthritis & rheumatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vitro functional assay with defined molecular mechanism (Cys408 disulfide), single lab","pmids":["41147740"],"is_preprint":false},{"year":2021,"finding":"CECR1-encoded ADA2 plays a role in butyrate-modulated M2 macrophage polarization; siRNA knockdown of CECR1 in THP-1 cells impaired butyrate-induced M2 polarization in LPS-stimulated cells, and ADA2 levels in pleural fluid correlated with TGF-β and IL-22 (anti-inflammatory markers) and inversely with CCL21 and CCL25.","method":"siRNA knockdown in THP-1 macrophages, flow cytometry, ELISA of pleural fluid","journal":"International immunopharmacology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single knockdown assay with correlation data, single lab, limited mechanistic depth","pmids":["33857806"],"is_preprint":false},{"year":2025,"finding":"ADA2 localizes to endolysosomes within macrophages; intracellular ADA2 concentration decreases in cells secreting TNF-α, suggesting ADA2 functions as a lysosomal adenosine deaminase that regulates TNF-α expression. Secreted ADA2 can bind to apoptotic cells and reduce extracellular adenosine levels to activate immune cells.","method":"Subcellular localization imaging, correlation of intracellular ADA2 with TNF-α secretion, binding assay on apoptotic cells, bronchoalveolar lavage analysis","journal":"Frontiers of medicine","confidence":"Low","confidence_rationale":"Tier 3 / Weak — localization and correlative data without direct mechanistic proof of causal pathway, single lab","pmids":["39832022"],"is_preprint":false},{"year":2022,"finding":"Lentiviral-mediated ADA2 gene transfer into patient-derived macrophages and CD34+ HSPCs restored ADA2 protein expression and enzymatic activity, ameliorated M1 macrophage cytokine production (IFN-γ, phospho-STAT1), and reduced macrophage-mediated endothelial activation, demonstrating that ADA2 loss-of-function is the direct cause of these immune and vascular defects.","method":"Lentiviral transduction of patient cells, enzyme activity assay, western blotting, cytokine measurement, endothelial activation assay, colony-forming unit assay","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gene correction rescue with multiple cellular phenotype readouts in primary patient cells, single lab","pmids":["35529868"],"is_preprint":false}],"current_model":"Human ADA2 (CECR1) is a secreted, glycosylated, dimeric extracellular enzyme of the ADGF family that deaminates adenosine to inosine (and can edit deoxyadenosine in DNA within lysosomes to regulate TLR9 signaling); its crystal structure reveals a catalytic domain plus two novel dimerization/receptor-binding domains distinct from monomeric ADA1; it is produced predominantly by monocytes/macrophages, binds to specific immune cell subsets (neutrophils, NK cells, B cells, CD16+ monocytes, regulatory T cells) lacking the ADA1 receptor CD26, promotes M2 macrophage polarization and pericyte recruitment via PDGFB-PDGFRβ paracrine signaling, and regulates hematopoietic stem cell emergence via the adenosine A2b receptor pathway; loss-of-function mutations cause DADA2 vasculopathy through impaired endothelial integrity and excessive monocyte-driven inflammation, with dominant-negative variants disrupting ADA2 dimerization and secretion via Cys408-mediated disulfide aggregation."},"narrative":{"mechanistic_narrative":"ADA2 (CECR1) is a secreted, heparin-binding adenosine deaminase of the ADGF family that functions extracellularly and within the endolysosomal system to regulate adenosine-dependent signaling, immune cell behavior, and vascular development [PMID:15926889, PMID:24552284]. Crystallography established that ADA2 comprises a catalytic domain plus two ADGF/ADA2-specific domains of novel fold that mediate dimerization and cell-surface receptor binding, with extensive glycosylation and a conserved disulfide bond consistent with an extracellular role and a substrate-binding pocket distinct from ADA1 [PMID:20147294]; N-linked glycosylation and proper dimerization/secretion are essential for normal function [PMID:29936104]. Beyond deaminating free adenosine, ADA2 localizes to lysosomes via glycan-directed targeting and edits deoxyadenosine to deoxyinosine in DNA, thereby modulating TLR9-dependent innate immune sensing [PMID:39441717]. Produced largely by monocytes/macrophages, ADA2 binds immune cell subsets lacking the ADA1 receptor CD26 (neutrophils, CD16+ monocytes, NK cells, B cells, regulatory T cells) [PMID:27663683], drives M2 macrophage polarization, and promotes neovascularization by upregulating macrophage PDGFB that activates pericyte PDGFRβ signaling in a paracrine manner [PMID:28534507, PMID:28453746]. In development, its deaminase activity acts upstream of adenosine/P1 receptor signaling, and it regulates hematopoietic stem cell emergence through the adenosine A2b receptor pathway by restraining endothelial inflammation [PMID:18032387, PMID:38777862]. Biallelic loss-of-function mutations cause the autoinflammatory vasculopathy DADA2, with reduced protein and enzymatic activity, monocyte-driven endothelial damage, and rescue by wild-type CECR1 or gene transfer [PMID:24552284, PMID:35529868]; dominant-negative missense variants disrupt dimerization and secretion through Cys408-mediated intracellular disulfide aggregation [PMID:40864493].","teleology":[{"year":2000,"claim":"Before any biochemical role was known, the question was what kind of protein CECR1 encodes; sequence and expression analysis linked it to insect growth factors and placed expression in developing cardiovascular and neural structures.","evidence":"Exon trapping, RT-PCR, Northern blot, and in situ hybridization on human embryo","pmids":["10756095"],"confidence":"Low","gaps":["No enzymatic activity demonstrated","No functional perturbation","Developmental role inferred from expression only"]},{"year":2005,"claim":"It was unknown whether ADA2 was a true enzyme; heparin-affinity purification and activity assays defined it as an ADGF-family adenosine deaminase active at acidic pH and high adenosine concentrations, distinguishing it biochemically from ADA1.","evidence":"Heparin-affinity purification and in vitro enzyme activity assays","pmids":["15926889"],"confidence":"Medium","gaps":["Physiological substrate not established","No structural basis for activity","Single lab in vitro characterization"]},{"year":2005,"claim":"To test whether ADA2 deaminase dosage matters in vivo, transgenic overexpression showed gain-of-function disrupts heart and kidney development, implicating tightly controlled ADA2 activity in organogenesis.","evidence":"Cardiac-specific and ubiquitous promoter-driven transgenic mouse overexpression with histological analysis","pmids":["16145841"],"confidence":"Medium","gaps":["Mechanism linking deaminase activity to organ phenotype unknown","Overexpression may not reflect physiological role","Receptor/signaling pathway not defined"]},{"year":2007,"claim":"Whether the enzyme activity is required for the growth-factor function was open; Xenopus knockdown placed ADA2 deaminase activity upstream of adenosine/P1 receptor signaling in embryogenesis.","evidence":"Morpholino knockdown in Xenopus with recombinant enzyme assay and P1 receptor agonist rescue","pmids":["18032387"],"confidence":"Medium","gaps":["Specific P1 receptor not identified","Ortholog model may not fully reflect human biology","Direct receptor binding not shown"]},{"year":2010,"claim":"The structural basis of ADA2's distinct activity was unknown; crystal structures revealed a catalytic domain plus two novel ADGF/ADA2-specific dimerization/receptor-binding domains, glycosylation, and a substrate pocket differing from ADA1.","evidence":"X-ray crystallography with transition-state analogue co-crystal and structural comparison to ADA1","pmids":["20147294"],"confidence":"High","gaps":["Cell-surface receptor not identified","Functional consequence of dimerization not tested in cells","No structure of disease variants"]},{"year":2014,"claim":"The pathological role of ADA2 was unknown until biallelic CECR1 loss-of-function mutations were shown to cause vasculopathy, stroke, and inflammation, with zebrafish rescue establishing causality and patient monocytes damaging endothelium.","evidence":"Whole-exome sequencing, enzyme assays, zebrafish morpholino knockdown with human CECR1 rescue, and endothelial co-culture","pmids":["24552284"],"confidence":"High","gaps":["Molecular mechanism of endothelial damage not resolved","Link between enzyme loss and inflammation undefined","Cell-surface partner unknown"]},{"year":2016,"claim":"How ADA2 engages immune cells was unclear; binding assays showed it binds CD26-negative subsets distinct from ADA1, indicating a separate cell-surface anchoring function on neutrophils, CD16+ monocytes, NK, B, and regulatory T cells.","evidence":"Flow cytometry binding assays with recombinant ADA2 on patient blood","pmids":["27663683"],"confidence":"Medium","gaps":["The ADA2 cell-surface receptor is not identified","Functional consequence of binding not directly tested","Single lab"]},{"year":2017,"claim":"The mechanism connecting macrophage ADA2 to vasculature was unknown; in glioblastoma, macrophage CECR1 was shown to drive neovascularization by upregulating PDGFB to activate pericyte PDGFRβ, and to promote M2 polarization via MAPK signaling.","evidence":"siRNA knockdown, recombinant stimulation, 3D co-culture angiogenesis and migration assays, qRT-PCR, conditioned medium transfer","pmids":["28534507","28453746"],"confidence":"Medium","gaps":["How ADA2 enzymatic activity links to PDGFB induction unclear","Tumor context may differ from DADA2 vasculopathy","Receptor mediating ADA2 effect on macrophages unknown"]},{"year":2018,"claim":"Whether post-translational modification governs ADA2 biology was open; a pathogenic variant disrupting an N-glycosylation consensus site established that N-linked glycosylation is essential for ADA2 stability/secretion.","evidence":"Identification of patient variant and biochemical analysis of the glycosylation defect","pmids":["29936104"],"confidence":"Medium","gaps":["Quantitative effect on secretion vs stability not separated","Single variant studied","Downstream cellular consequence not assessed"]},{"year":2022,"claim":"Whether ADA2 loss directly causes the immune/vascular defects was confirmed by lentiviral gene transfer into patient macrophages and HSPCs, which restored enzyme activity and corrected M1 cytokine production and endothelial activation.","evidence":"Lentiviral transduction of patient cells with enzyme, cytokine, endothelial activation, and colony-forming readouts","pmids":["35529868"],"confidence":"Medium","gaps":["Does not define the molecular substrate driving inflammation","In vivo efficacy not tested here","Single lab"]},{"year":2024,"claim":"The physiological substrate and subcellular site of ADA2 action were reconsidered; lysosomal-localized ADA2 was shown to edit deoxyadenosine in DNA to modulate TLR9, suggesting DNA rather than free adenosine is a key substrate.","evidence":"Subcellular fractionation, DNA-binding and DNA deamination assays, TLR9 reporter assays, glycan modification experiments","pmids":["39441717"],"confidence":"Medium","gaps":["Relative contribution of DNA editing vs adenosine deamination in disease unresolved","In vivo relevance of TLR9 modulation not established","Single lab"]},{"year":2024,"claim":"How ADA2 contributes to blood formation was unknown; a zebrafish cecr1b model showed ADA2 deficiency impairs HSC specification via endothelial inflammation, with rescue by anti-inflammatory agents, A2bR modulation, or recombinant ADA2, placing ADA2 upstream of A2bR signaling.","evidence":"Zebrafish loss-of-function model with multiple independent pharmacological and protein rescue strategies","pmids":["38777862"],"confidence":"High","gaps":["Direct ADA2-A2bR molecular link not shown","Human HSC relevance not demonstrated","Whether DNA editing or adenosine deamination drives the effect unknown"]},{"year":2025,"claim":"The molecular basis for dominant inheritance and allele severity was defined; specific missense variants act dominant-negatively by forming Cys408-mediated intracellular disulfide aggregates that block dimerization and secretion, while residual activity tracks with hypomorphic phenotype.","evidence":"Transfected cell expression, enzyme activity assays, western blotting, and aggregation analysis of multiple variants","pmids":["40864493","41147740"],"confidence":"Medium","gaps":["Aggregation mechanism shown in overexpression systems","In vivo dominant-negative effect not modeled","Structural detail of Cys408 bridging not resolved"]},{"year":null,"claim":"The identity of the ADA2 cell-surface receptor on CD26-negative immune subsets and the in vivo balance between free-adenosine deamination, lysosomal DNA editing, and A2bR/PDGFB signaling in driving DADA2 pathology remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["ADA2 receptor unidentified","Dominant substrate in vivo unsettled","Mechanistic link between enzyme loss and vasculitis incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[10]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[10]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[1,16]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[10,16]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,10,17]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4,8,11]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[5,11]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,12]}],"complexes":["ADA2 homodimer"],"partners":["PDGFB","PDGFRB","TLR9"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NZK5","full_name":"Adenosine deaminase 2","aliases":["Cat eye syndrome critical region protein 1"],"length_aa":511,"mass_kda":58.9,"function":"Adenosine deaminase that may contribute to the degradation of extracellular adenosine, a signaling molecule that controls a variety of cellular responses. Requires elevated adenosine levels for optimal enzyme activity. Binds to cell surfaces via proteoglycans and may play a role in the regulation of cell proliferation and differentiation, independently of its enzyme activity","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q9NZK5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ADA2","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ADA2","total_profiled":1310},"omim":[{"mim_id":"619892","title":"ZINC FINGER ZZ-TYPE DOMAIN-CONTAINING PROTEIN 3; ZZZ3","url":"https://www.omim.org/entry/619892"},{"mim_id":"615688","title":"VASCULITIS, AUTOINFLAMMATION, IMMUNODEFICIENCY, AND HEMATOLOGIC DEFECTS SYNDROME; VAIHS","url":"https://www.omim.org/entry/615688"},{"mim_id":"613696","title":"UPSTREAM BINDING TRANSCRIPTION FACTOR (RNA POLYMERASE I)-LIKE 1; UBTFL1","url":"https://www.omim.org/entry/613696"},{"mim_id":"612116","title":"UBIQUITIN-SPECIFIC PROTEASE 22; USP22","url":"https://www.omim.org/entry/612116"},{"mim_id":"608958","title":"ADENOSINE DEAMINASE; ADA","url":"https://www.omim.org/entry/608958"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":106.4}],"url":"https://www.proteinatlas.org/search/ADA2"},"hgnc":{"alias_symbol":["ADGF"],"prev_symbol":["IDGFL","CECR1"]},"alphafold":{"accession":"Q9NZK5","domains":[{"cath_id":"3.20.20.140","chopping":"87-121_200-511","consensus_level":"high","plddt":98.6501,"start":87,"end":511},{"cath_id":"-","chopping":"126-197","consensus_level":"medium","plddt":97.8797,"start":126,"end":197}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZK5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZK5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZK5-F1-predicted_aligned_error_v6.png","plddt_mean":95.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ADA2","jax_strain_url":"https://www.jax.org/strain/search?query=ADA2"},"sequence":{"accession":"Q9NZK5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NZK5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NZK5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZK5"}},"corpus_meta":[{"pmid":"24552284","id":"PMC_24552284","title":"Early-onset 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therapy","url":"https://pubmed.ncbi.nlm.nih.gov/36804932","citation_count":1,"is_preprint":false},{"pmid":"40196538","id":"PMC_40196538","title":"Structural basis of substrate specificity of Helix pomatia AMP deaminase and a chimeric ADGF adenosine deaminase.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40196538","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47670,"output_tokens":5190,"usd":0.11043,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12483,"output_tokens":4558,"usd":0.088182,"stage2_stop_reason":"end_turn"},"total_usd":0.198612,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"I need to carefully classify each paper before extracting. The query gene is human ADA2 (CECR1/CECR1/ADGF), which encodes adenosine deaminase 2 — a secreted enzyme with adenosine deaminase activity involved in immune function and vasculopathy.\n\nI need to distinguish:\n1. Human/vertebrate ADA2 (CECR1) papers → INCLUDE\n2. Yeast/fungal/Drosophila ADA2 (transcriptional adaptor/SAGA complex subunit) → these are a COMPLETELY DIFFERENT protein (transcriptional coactivator, no adenosine deaminase activity). The yeast ADA2 is a component of SAGA/GCN5 complex — this is NOT an ortholog of human ADA2/CECR1. Human ADA2 (CECR1) is the adenosine deaminase growth factor, while the yeast ADA2 is a transcriptional adaptor. These are different proteins that share a symbol by convention in different contexts.\n\nWait — I need to reconsider. The HGNC entry for human ADA2 lists aliases: ADGF, IDGFL, CECR1. The yeast ADA2 (transcriptional adaptor in SAGA) is a genuinely different protein — the human ortholog of yeast ADA2 (SAGA subunit) is KAT2A-associated ADA2 proteins (ADA2A/ADA2B, encoded by TADA2A/TADA2B). The human gene \"ADA2\" queried here is CECR1/adenosine deaminase 2, not TADA2A/TADA2B. So the yeast/fungal/Drosophila SAGA-ADA2 papers are NOT about this gene.\n\nPapers about human ADA2/CECR1 (adenosine deaminase): [1], [6], [10], [11], [12], [17], [18], [19], [23], [24], [25], [27], [28], [29], [34], [36], [39], [44], [45], [47], [48], [49], [51], [53], [57], [59], [62], [63], [68], [69], [70], [72], [75], [85], [90], [92], [97], [98], [99]\n\nPapers about yeast/fungal/Drosophila transcriptional adaptor ADA2 (SAGA) — DIFFERENT GENE → EXCLUDE: [2], [3], [4], [5], [7], [8], [9], [13], [14], [15], [16], [20], [21], [22], [26], [31], [32], [33 - wait this is about human patients], [35], [37], [38], [40], [41], [42], [43], [50], [52], [54], [60], [61], [64], [65 - wait, this is about DADA2 patients], [73], [83], [86], [95]\n\nLet me now extract mechanistic discoveries only from the included papers:\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"ADA2 (CECR1) was identified as a member of the ADGF (adenosine deaminase-related growth factor) family and shown to be a heparin-binding protein with adenosine deaminase activity; purification via heparin affinity demonstrated its biochemical properties including activity at acidic pH and elevated adenosine concentrations.\",\n      \"method\": \"Heparin-affinity purification, enzyme activity assays, biochemical characterization\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzyme assay and biochemical purification, single lab, single study\",\n      \"pmids\": [\"15926889\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Crystal structures of human ADA2 and ADA2 bound to a transition-state analogue revealed the structural basis of catalytic activity: ADA2 contains a catalytic domain plus two ADGF/ADA2-specific domains of novel folds mediating protein dimerization and binding to cell-surface receptors. Extensive glycosylation and a conserved disulfide bond indicate extracellular function. The substrate-binding pocket of ADA2 differs substantially from ADA1, explaining distinct substrate and inhibitor specificities.\",\n      \"method\": \"X-ray crystallography, transition-state analogue co-crystal structure, structural comparison\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation, multiple structural features resolved in one rigorous study\",\n      \"pmids\": [\"20147294\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Loss-of-function mutations in CECR1 (encoding ADA2) cause a syndrome of vasculopathy, stroke, and inflammation. Patients had markedly reduced ADA2 protein levels and ADA2-specific enzymatic activity. Morpholino knockdown of zebrafish ADA2 homologue caused intracranial hemorrhages and neutropenia; these phenotypes were rescued by co-injection with wild-type but not mutant human CECR1, establishing a direct causal link. Monocytes from patients induced endothelial cell layer damage in co-culture.\",\n      \"method\": \"Whole-exome sequencing, enzyme activity assay, zebrafish morpholino knockdown, co-culture endothelial damage assay, immunoblotting\",\n      \"journal\": \"The New England journal of medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (genetic, biochemical, zebrafish in vivo rescue), replicated across multiple patients\",\n      \"pmids\": [\"24552284\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ADA2 binds to distinct subsets of immune cells that lack CD26 (the ADA1 receptor), including neutrophils, monocytes (preferentially CD16+ monocytes), NK cells, B cells, and CD39+ regulatory T cells; this cell-surface binding is separate from ADA1 binding, suggesting ADA2 regulates activation and survival of immune cells anchored to the cell surface.\",\n      \"method\": \"Flow cytometry binding assays with recombinant ADA2, analysis of patient blood samples\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay on multiple immune cell subsets, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"27663683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"In Xenopus, CECR1/ADGF orthologs exhibit adenosine deaminase activity that is indispensable for their growth factor activity; knockdown caused developmental defects recapitulated by exogenous adenosine or P1 receptor agonists, placing ADA2 function upstream of adenosine/P1 receptor signaling in embryogenesis.\",\n      \"method\": \"Morpholino oligonucleotide knockdown in Xenopus, recombinant protein enzyme assay, adenosine/P1 receptor agonist injection, developmental marker gene expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis by morpholino plus pharmacological rescue, single lab, ortholog model\",\n      \"pmids\": [\"18032387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In glioblastoma, macrophage-expressed CECR1 (ADA2) promotes neovascularization by upregulating PDGFB mRNA and protein in macrophages, which then activates pericyte PDGFRβ signaling in a paracrine manner, promoting pericyte migration and periostin deposition; siRNA knockdown of CECR1 in macrophages reduced vessel formation in a 3D co-culture system.\",\n      \"method\": \"siRNA knockdown, recombinant protein stimulation, 3D co-culture angiogenesis assay, transwell migration assay, qRT-PCR, immunohistochemistry\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss and gain of function with defined molecular pathway (PDGFB-PDGFRβ), single lab, multiple orthogonal methods\",\n      \"pmids\": [\"28534507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CECR1 in M2-like tumor-associated macrophages regulates macrophage M2 polarization and exerts paracrine effects on glioma cells via MAPK signaling; CECR1 knockdown or stimulation of macrophages altered M2 phenotype markers and affected tumor cell proliferation and migration.\",\n      \"method\": \"siRNA knockdown, conditioned medium transfer, flow cytometry, immunohistochemistry, in vitro proliferation and migration assays\",\n      \"journal\": \"Neuro-oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss and gain of function with pathway readout (MAPK), single lab, multiple methods\",\n      \"pmids\": [\"28453746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"CECR1 encodes a protein with sequence similarity to insect growth factors (IDGF from flesh fly, MDGF from sea hare) and is alternatively spliced; it is expressed in developing heart outflow tract, cranial nerve ganglia, and notochord, suggesting a developmental role.\",\n      \"method\": \"Exon trapping, RT-PCR, Northern blot, in situ hybridization on human embryo\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — expression/localization data only, no functional mechanistic experiment, single study\",\n      \"pmids\": [\"10756095\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Transgenic overexpression of CECR1 adenosine deaminase in mice under cardiac-specific (myosin heavy chain) or ubiquitous (beta-actin) promoters caused heart enlargement, high rates of embryonic and neonatal lethality, and kidney and eye abnormalities, demonstrating that CECR1 gain-of-function disrupts heart and kidney development.\",\n      \"method\": \"Transgenic mouse generation, cardiac and ubiquitous promoter-driven overexpression, morphological and histological analysis\",\n      \"journal\": \"Transgenic research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct in vivo gain-of-function with defined organ phenotypes, single lab\",\n      \"pmids\": [\"16145841\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A pathogenic mutation in DADA2 affecting a consensus N-linked glycosylation sequence disrupts glycosylation of ADA2, establishing that N-linked glycosylation is essential for normal ADA2 biology (protein stability/secretion).\",\n      \"method\": \"Identification of novel mutation, biochemical analysis of glycosylation defect\",\n      \"journal\": \"The Journal of allergy and clinical immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct experiment on patient-derived variant demonstrating glycosylation requirement, single study\",\n      \"pmids\": [\"29936104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ADA2 localizes within lysosomes (targeted via glycan modifications) and interacts with DNA molecules, editing deoxyadenosine (dA) to deoxyinosine (dI) in DNA; this lysosomal DNA-editing activity modulates TLR9 activation, regulating innate immune sensing of nucleic acids. Data suggest DNA rather than free adenosine is the physiological substrate.\",\n      \"method\": \"Subcellular fractionation/localization studies, DNA-binding assays, in vitro deamination assays on DNA substrates, TLR9 reporter assays, glycan modification experiments\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (localization, substrate assay, functional TLR9 assay), single lab\",\n      \"pmids\": [\"39441717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In a zebrafish cecr1b loss-of-function model, ADA2 deficiency disrupts hematopoietic stem cell specification and causes defective hematopoiesis via induction of inflammation in the vascular endothelium; pharmacological blockade of inflammation, modulation of the adenosine A2 receptor (A2bR) pathway, or administration of recombinant human ADA2 corrected these hematopoietic defects, placing ADA2 upstream of A2bR signaling in hematopoiesis regulation.\",\n      \"method\": \"Zebrafish cecr1b loss-of-function model, pharmacological rescue (A2R pathway modulation, anti-inflammatory agents), recombinant human ADA2 administration, hematopoietic assays\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic model with multiple independent rescue strategies and pathway placement, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"38777862\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Specific ADA2 missense variants (p.G47A, p.G47R, p.G47V, p.R169Q, p.E328K, p.H424N, p.Y453C) exert dominant-negative effects on ADA2 enzymatic activity, dimerization, and/or secretion; in vitro analysis showed these variants form large intracellular protein aggregates via disulfide bond formation at Cys408.\",\n      \"method\": \"Transfected cell expression assays, enzyme activity assays, western blotting, protein aggregation analysis\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional cell-based assays with multiple variants, mechanistic finding of disulfide-mediated aggregation, single lab\",\n      \"pmids\": [\"40864493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Dominant-negative ADA2 missense variants disrupt ADA2 enzymatic activity, dimerization, and/or secretion; these variants can cause DADA2 in heterozygous carriers, demonstrating that ADA2 protein function requires proper dimerization and secretion.\",\n      \"method\": \"Overexpression in 293T cells, enzyme activity assay, western blotting, patient cohort analysis\",\n      \"journal\": \"medRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 / Weak — preprint, single lab, overlaps with peer-reviewed version (PMID:40864493)\",\n      \"pmids\": [\"39711711\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In vitro analysis of DADA2-associated ADA2 missense variants shows that residual ADA2 activity correlates with hypomorphic alleles; variants can synergistically disrupt protein function via intracellular aggregate formation mediated by disulfide bonds at Cys408.\",\n      \"method\": \"Overexpression in 293T cells, enzyme activity assay, western blotting\",\n      \"journal\": \"Arthritis & rheumatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vitro functional assay with defined molecular mechanism (Cys408 disulfide), single lab\",\n      \"pmids\": [\"41147740\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CECR1-encoded ADA2 plays a role in butyrate-modulated M2 macrophage polarization; siRNA knockdown of CECR1 in THP-1 cells impaired butyrate-induced M2 polarization in LPS-stimulated cells, and ADA2 levels in pleural fluid correlated with TGF-β and IL-22 (anti-inflammatory markers) and inversely with CCL21 and CCL25.\",\n      \"method\": \"siRNA knockdown in THP-1 macrophages, flow cytometry, ELISA of pleural fluid\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single knockdown assay with correlation data, single lab, limited mechanistic depth\",\n      \"pmids\": [\"33857806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ADA2 localizes to endolysosomes within macrophages; intracellular ADA2 concentration decreases in cells secreting TNF-α, suggesting ADA2 functions as a lysosomal adenosine deaminase that regulates TNF-α expression. Secreted ADA2 can bind to apoptotic cells and reduce extracellular adenosine levels to activate immune cells.\",\n      \"method\": \"Subcellular localization imaging, correlation of intracellular ADA2 with TNF-α secretion, binding assay on apoptotic cells, bronchoalveolar lavage analysis\",\n      \"journal\": \"Frontiers of medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — localization and correlative data without direct mechanistic proof of causal pathway, single lab\",\n      \"pmids\": [\"39832022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Lentiviral-mediated ADA2 gene transfer into patient-derived macrophages and CD34+ HSPCs restored ADA2 protein expression and enzymatic activity, ameliorated M1 macrophage cytokine production (IFN-γ, phospho-STAT1), and reduced macrophage-mediated endothelial activation, demonstrating that ADA2 loss-of-function is the direct cause of these immune and vascular defects.\",\n      \"method\": \"Lentiviral transduction of patient cells, enzyme activity assay, western blotting, cytokine measurement, endothelial activation assay, colony-forming unit assay\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gene correction rescue with multiple cellular phenotype readouts in primary patient cells, single lab\",\n      \"pmids\": [\"35529868\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Human ADA2 (CECR1) is a secreted, glycosylated, dimeric extracellular enzyme of the ADGF family that deaminates adenosine to inosine (and can edit deoxyadenosine in DNA within lysosomes to regulate TLR9 signaling); its crystal structure reveals a catalytic domain plus two novel dimerization/receptor-binding domains distinct from monomeric ADA1; it is produced predominantly by monocytes/macrophages, binds to specific immune cell subsets (neutrophils, NK cells, B cells, CD16+ monocytes, regulatory T cells) lacking the ADA1 receptor CD26, promotes M2 macrophage polarization and pericyte recruitment via PDGFB-PDGFRβ paracrine signaling, and regulates hematopoietic stem cell emergence via the adenosine A2b receptor pathway; loss-of-function mutations cause DADA2 vasculopathy through impaired endothelial integrity and excessive monocyte-driven inflammation, with dominant-negative variants disrupting ADA2 dimerization and secretion via Cys408-mediated disulfide aggregation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ADA2 (CECR1) is a secreted, heparin-binding adenosine deaminase of the ADGF family that functions extracellularly and within the endolysosomal system to regulate adenosine-dependent signaling, immune cell behavior, and vascular development [#0, #2]. Crystallography established that ADA2 comprises a catalytic domain plus two ADGF/ADA2-specific domains of novel fold that mediate dimerization and cell-surface receptor binding, with extensive glycosylation and a conserved disulfide bond consistent with an extracellular role and a substrate-binding pocket distinct from ADA1 [#1]; N-linked glycosylation and proper dimerization/secretion are essential for normal function [#9]. Beyond deaminating free adenosine, ADA2 localizes to lysosomes via glycan-directed targeting and edits deoxyadenosine to deoxyinosine in DNA, thereby modulating TLR9-dependent innate immune sensing [#10]. Produced largely by monocytes/macrophages, ADA2 binds immune cell subsets lacking the ADA1 receptor CD26 (neutrophils, CD16+ monocytes, NK cells, B cells, regulatory T cells) [#3], drives M2 macrophage polarization, and promotes neovascularization by upregulating macrophage PDGFB that activates pericyte PDGFRβ signaling in a paracrine manner [#5, #6]. In development, its deaminase activity acts upstream of adenosine/P1 receptor signaling, and it regulates hematopoietic stem cell emergence through the adenosine A2b receptor pathway by restraining endothelial inflammation [#4, #11]. Biallelic loss-of-function mutations cause the autoinflammatory vasculopathy DADA2, with reduced protein and enzymatic activity, monocyte-driven endothelial damage, and rescue by wild-type CECR1 or gene transfer [#2, #17]; dominant-negative missense variants disrupt dimerization and secretion through Cys408-mediated intracellular disulfide aggregation [#12].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Before any biochemical role was known, the question was what kind of protein CECR1 encodes; sequence and expression analysis linked it to insect growth factors and placed expression in developing cardiovascular and neural structures.\",\n      \"evidence\": \"Exon trapping, RT-PCR, Northern blot, and in situ hybridization on human embryo\",\n      \"pmids\": [\"10756095\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No enzymatic activity demonstrated\", \"No functional perturbation\", \"Developmental role inferred from expression only\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"It was unknown whether ADA2 was a true enzyme; heparin-affinity purification and activity assays defined it as an ADGF-family adenosine deaminase active at acidic pH and high adenosine concentrations, distinguishing it biochemically from ADA1.\",\n      \"evidence\": \"Heparin-affinity purification and in vitro enzyme activity assays\",\n      \"pmids\": [\"15926889\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological substrate not established\", \"No structural basis for activity\", \"Single lab in vitro characterization\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"To test whether ADA2 deaminase dosage matters in vivo, transgenic overexpression showed gain-of-function disrupts heart and kidney development, implicating tightly controlled ADA2 activity in organogenesis.\",\n      \"evidence\": \"Cardiac-specific and ubiquitous promoter-driven transgenic mouse overexpression with histological analysis\",\n      \"pmids\": [\"16145841\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking deaminase activity to organ phenotype unknown\", \"Overexpression may not reflect physiological role\", \"Receptor/signaling pathway not defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Whether the enzyme activity is required for the growth-factor function was open; Xenopus knockdown placed ADA2 deaminase activity upstream of adenosine/P1 receptor signaling in embryogenesis.\",\n      \"evidence\": \"Morpholino knockdown in Xenopus with recombinant enzyme assay and P1 receptor agonist rescue\",\n      \"pmids\": [\"18032387\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific P1 receptor not identified\", \"Ortholog model may not fully reflect human biology\", \"Direct receptor binding not shown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"The structural basis of ADA2's distinct activity was unknown; crystal structures revealed a catalytic domain plus two novel ADGF/ADA2-specific dimerization/receptor-binding domains, glycosylation, and a substrate pocket differing from ADA1.\",\n      \"evidence\": \"X-ray crystallography with transition-state analogue co-crystal and structural comparison to ADA1\",\n      \"pmids\": [\"20147294\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-surface receptor not identified\", \"Functional consequence of dimerization not tested in cells\", \"No structure of disease variants\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"The pathological role of ADA2 was unknown until biallelic CECR1 loss-of-function mutations were shown to cause vasculopathy, stroke, and inflammation, with zebrafish rescue establishing causality and patient monocytes damaging endothelium.\",\n      \"evidence\": \"Whole-exome sequencing, enzyme assays, zebrafish morpholino knockdown with human CECR1 rescue, and endothelial co-culture\",\n      \"pmids\": [\"24552284\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of endothelial damage not resolved\", \"Link between enzyme loss and inflammation undefined\", \"Cell-surface partner unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"How ADA2 engages immune cells was unclear; binding assays showed it binds CD26-negative subsets distinct from ADA1, indicating a separate cell-surface anchoring function on neutrophils, CD16+ monocytes, NK, B, and regulatory T cells.\",\n      \"evidence\": \"Flow cytometry binding assays with recombinant ADA2 on patient blood\",\n      \"pmids\": [\"27663683\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The ADA2 cell-surface receptor is not identified\", \"Functional consequence of binding not directly tested\", \"Single lab\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The mechanism connecting macrophage ADA2 to vasculature was unknown; in glioblastoma, macrophage CECR1 was shown to drive neovascularization by upregulating PDGFB to activate pericyte PDGFRβ, and to promote M2 polarization via MAPK signaling.\",\n      \"evidence\": \"siRNA knockdown, recombinant stimulation, 3D co-culture angiogenesis and migration assays, qRT-PCR, conditioned medium transfer\",\n      \"pmids\": [\"28534507\", \"28453746\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How ADA2 enzymatic activity links to PDGFB induction unclear\", \"Tumor context may differ from DADA2 vasculopathy\", \"Receptor mediating ADA2 effect on macrophages unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Whether post-translational modification governs ADA2 biology was open; a pathogenic variant disrupting an N-glycosylation consensus site established that N-linked glycosylation is essential for ADA2 stability/secretion.\",\n      \"evidence\": \"Identification of patient variant and biochemical analysis of the glycosylation defect\",\n      \"pmids\": [\"29936104\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative effect on secretion vs stability not separated\", \"Single variant studied\", \"Downstream cellular consequence not assessed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Whether ADA2 loss directly causes the immune/vascular defects was confirmed by lentiviral gene transfer into patient macrophages and HSPCs, which restored enzyme activity and corrected M1 cytokine production and endothelial activation.\",\n      \"evidence\": \"Lentiviral transduction of patient cells with enzyme, cytokine, endothelial activation, and colony-forming readouts\",\n      \"pmids\": [\"35529868\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not define the molecular substrate driving inflammation\", \"In vivo efficacy not tested here\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The physiological substrate and subcellular site of ADA2 action were reconsidered; lysosomal-localized ADA2 was shown to edit deoxyadenosine in DNA to modulate TLR9, suggesting DNA rather than free adenosine is a key substrate.\",\n      \"evidence\": \"Subcellular fractionation, DNA-binding and DNA deamination assays, TLR9 reporter assays, glycan modification experiments\",\n      \"pmids\": [\"39441717\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of DNA editing vs adenosine deamination in disease unresolved\", \"In vivo relevance of TLR9 modulation not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"How ADA2 contributes to blood formation was unknown; a zebrafish cecr1b model showed ADA2 deficiency impairs HSC specification via endothelial inflammation, with rescue by anti-inflammatory agents, A2bR modulation, or recombinant ADA2, placing ADA2 upstream of A2bR signaling.\",\n      \"evidence\": \"Zebrafish loss-of-function model with multiple independent pharmacological and protein rescue strategies\",\n      \"pmids\": [\"38777862\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ADA2-A2bR molecular link not shown\", \"Human HSC relevance not demonstrated\", \"Whether DNA editing or adenosine deamination drives the effect unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The molecular basis for dominant inheritance and allele severity was defined; specific missense variants act dominant-negatively by forming Cys408-mediated intracellular disulfide aggregates that block dimerization and secretion, while residual activity tracks with hypomorphic phenotype.\",\n      \"evidence\": \"Transfected cell expression, enzyme activity assays, western blotting, and aggregation analysis of multiple variants\",\n      \"pmids\": [\"40864493\", \"41147740\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Aggregation mechanism shown in overexpression systems\", \"In vivo dominant-negative effect not modeled\", \"Structural detail of Cys408 bridging not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The identity of the ADA2 cell-surface receptor on CD26-negative immune subsets and the in vivo balance between free-adenosine deamination, lysosomal DNA editing, and A2bR/PDGFB signaling in driving DADA2 pathology remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ADA2 receptor unidentified\", \"Dominant substrate in vivo unsettled\", \"Mechanistic link between enzyme loss and vasculitis incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 16]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [10, 16]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 10, 17]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4, 8, 11]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5, 11]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 12]}\n    ],\n    \"complexes\": [\"ADA2 homodimer\"],\n    \"partners\": [\"PDGFB\", \"PDGFRB\", \"TLR9\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}