{"gene":"SLC39A4","run_date":"2026-06-10T07:46:34","timeline":{"discoveries":[{"year":2002,"finding":"SLC39A4 encodes a ZIP-family zinc transporter protein expressed in the duodenum/jejunum; mutations in SLC39A4 cause acrodermatitis enteropathica, establishing it as the intestinal zinc uptake transporter responsible for this disease.","method":"Chromosomal mapping, expression analysis, and mutational analysis in eight AE-affected families","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct mutational analysis in multiple families, replicated independently, foundational disease-gene identification","pmids":["12068297"],"is_preprint":false},{"year":2007,"finding":"ZIP4 protein abundance is regulated post-transcriptionally: during zinc deficiency, ZIP4 mRNA stability increases and ZIP4 protein localizes to apical membranes; zinc repletion triggers ZIP4 internalization and degradation in enterocytes and visceral endoderm cells.","method":"In vivo dietary zinc manipulation in mice combined with immunofluorescence localization and mRNA stability assays in mouse Hepa cells","journal":"Biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (mRNA stability assay, transcription rate measurement, protein localization, in vivo mouse experiments), replicated across cell types and in vivo","pmids":["18020946"],"is_preprint":false},{"year":2007,"finding":"Homozygous Zip4 knockout mouse embryos die during early morphogenesis, demonstrating that ZIP4 is essential for early embryonic development; heterozygosity causes hypersensitivity to zinc deficiency with developmental defects exacerbated by maternal zinc deficiency and ameliorated by zinc excess.","method":"Gene knockout mouse model with dietary zinc manipulation; developmental phenotyping","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function in mouse with defined phenotypic rescue by dietary zinc, multiple developmental endpoints assessed","pmids":["17483098"],"is_preprint":false},{"year":2008,"finding":"During prolonged zinc deficiency, the extracellular N-terminal ectodomain of ZIP4 is proteolytically cleaved, leaving the eight-transmembrane C-terminal half on the plasma membrane; this cleavage is blocked by acrodermatitis enteropathica mutations near a predicted metalloproteinase cleavage site and is attenuated by inhibitors of endocytosis, suggesting ectodomain cleavage occurs following internalization and recycling back to the plasma membrane.","method":"In vivo intestinal analysis and transfected MDCK, CaCo2, and HEK293 cell lines; inhibitor studies; disease mutation analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple cell systems, in vivo validation, pharmacological inhibition, and disease mutation structure-function analysis in a single study","pmids":["18936158"],"is_preprint":false},{"year":2012,"finding":"Enterocyte-specific knockout of Zip4 in mice causes loss of labile zinc in Paneth cells, reprogramming of Paneth cells toward a goblet cell-like state (loss of Sox9 and lysozyme, accumulation of mucin), dysplasia of intestinal crypts, diminished small intestine cell division, and attenuated mTOR1 activity in villus enterocytes indicative of increased catabolism, establishing ZIP4 as essential for intestinal stem cell niche integrity.","method":"Tamoxifen-inducible, enterocyte-specific Zip4 knockout mouse; immunohistochemistry; elemental analysis; mTOR pathway assay","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional genetic knockout with multiple orthogonal readouts (histology, gene expression, elemental analysis, signaling pathway)","pmids":["22737083"],"is_preprint":false},{"year":2007,"finding":"Forced overexpression of ZIP4 in pancreatic cancer cells increases intracellular zinc levels, increases cell proliferation ~2-fold in vitro, and dramatically increases tumor volume (13-fold) and peritoneal dissemination in xenograft mouse models, establishing a functional role for ZIP4-mediated zinc uptake in promoting tumor growth.","method":"Stable overexpression in pancreatic cancer cell lines; in vitro proliferation assay; subcutaneous and orthotopic xenograft mouse models","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — gain-of-function in vitro and in vivo with multiple endpoints including zinc measurement, proliferation, and tumor growth","pmids":["18003899"],"is_preprint":false},{"year":2010,"finding":"RNAi knockdown of Zip4 in mouse Hepa cells significantly increases apoptosis and slows G0/G1-to-S phase progression under zinc-deficient conditions; forced overexpression of Zip4 in Hepa and MCF-7 cells enhances in vitro migration, while knockdown depresses migration.","method":"RNAi knockdown; cell cycle analysis after hydroxyurea block; apoptosis assay; cell migration assay; forced overexpression","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple cellular assays in cultured cells but no in vivo validation for these specific mechanisms; single lab","pmids":["20957146"],"is_preprint":false},{"year":2014,"finding":"The Leu372Val polymorphism and disease-causing mutations Leu372Pro and Leu372Arg at the same codon differentially affect ZIP4 surface expression and zinc uptake: the two AE mutations abolish cell surface expression and nearly eliminate zinc uptake, while the Val372 variant shows significantly reduced surface protein expression, reduced basal intracellular zinc, and reduced zinc uptake compared to Leu372.","method":"Transient overexpression of ZIP4 variants in HeLa cells; surface protein expression assay; zinc uptake assay","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional zinc uptake assay plus surface expression assay in human cells, single lab, multiple variants tested","pmids":["24586184"],"is_preprint":false},{"year":2006,"finding":"A splice-site variant in bovine SLC39A4 ortholog causes exon skipping, producing a protein predicted to lack two critical motifs in adjacent transmembrane domains implicated in forming the zinc transport pore, establishing loss of these transmembrane domains as the molecular basis of impaired zinc absorption in bovine hereditary zinc deficiency (lethal trait A46).","method":"Sequencing of bovine SLC39A4 ortholog; splice variant characterization; structural domain analysis","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — genetic and molecular characterization of a disease variant in an animal model; no in vitro functional reconstitution of transport activity","pmids":["16714095"],"is_preprint":false},{"year":2021,"finding":"Among all intestinal zinc transporters, Slc39a4 expression is the only one positively correlated with fractional zinc absorption (liver and plasma 67Zn appearance), identifying SLC39A4/ZIP4 as the primary determinant of dietary zinc absorption in young mice.","method":"Stable isotope (67Zn) oral gavage absorption assay in mice fed varied zinc diets; ICP-MS measurement; qPCR expression profiling of all 24 zinc transporters across intestinal segments","journal":"The Journal of nutritional biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo isotope absorption assay with correlation analysis across dietary conditions; single lab, correlational design limits mechanistic inference","pmids":["34843931"],"is_preprint":false},{"year":2021,"finding":"SLC39A4 knockdown in gallbladder cancer cell lines suppresses proliferation, migration, and xenograft tumor growth, while overexpression promotes proliferation, migration, and inhibits apoptosis, indicating ZIP4 modulates survival and metastasis-related signaling in GBC cells.","method":"siRNA knockdown and overexpression in GBC-SD and NOZ cells; MTT assay; colony formation; wound-healing and Transwell migration assays; nude mouse xenograft","journal":"Cancer management and research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — standard knockdown/overexpression phenotypic assays, single lab, no specific pathway mechanism identified","pmids":["33727860"],"is_preprint":false},{"year":2024,"finding":"UKLF (ubiquitous Krüppel-like factor) transcriptionally activates SLC39A4 expression, while PCBP2 stabilizes UKLF mRNA by binding its 3'-UTR, placing SLC39A4 as a downstream transcriptional target in a PCBP2/UKLF/SLC39A4 pathway in colorectal cancer cells.","method":"Reporter assays, RNA immunoprecipitation, mRNA stability assay, knockdown/overexpression experiments in CRC cell lines","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, transcriptional regulation shown by reporter assay but mechanistic detail of how UKLF activates SLC39A4 transcription is limited in the abstract","pmids":["38768927"],"is_preprint":false},{"year":2026,"finding":"YTHDF1 binds SLC39A4 mRNA and stabilizes its transcripts in an m6A-dependent manner (mutation of the m6A site in SLC39A4 coding sequence abolishes YTHDF1-mediated regulation); SLC39A4 overexpression attenuates cuproptosis induced by CuCl2/elesclomol treatment, while SLC39A4 knockdown potentiates it, establishing a role for ZIP4 in suppressing cuproptosis in gastric cancer cells.","method":"Lentiviral stable overexpression/knockdown; dual-luciferase m6A reporter assay; RNA immunoprecipitation for YTHDF1-SLC39A4 mRNA binding; proliferation and cuproptosis marker assays in cell lines and xenograft models","journal":"Cancer gene therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — m6A site mutagenesis with luciferase assay, RIP for direct binding, functional cuproptosis assay in vitro and in vivo; single lab","pmids":["42056258"],"is_preprint":false}],"current_model":"SLC39A4/ZIP4 is an intestinal apical zinc uptake transporter whose expression is dynamically regulated by zinc status through mRNA stability changes and protein trafficking (internalization and lysosomal degradation upon zinc repletion, or proteolytic ectodomain cleavage during prolonged deficiency); it is essential for embryonic development and intestinal stem cell niche integrity in mice, with its loss causing acrodermatitis enteropathica, and its aberrant overexpression in multiple cancers promoting proliferation, migration, and cuproptosis resistance partly through upstream m6A-dependent mRNA stabilization by YTHDF1."},"narrative":{"mechanistic_narrative":"SLC39A4 (ZIP4) is the principal apical zinc uptake transporter of the small intestine and the primary genetic determinant of dietary zinc absorption [PMID:12068297, PMID:34843931]. Its abundance is tuned to zinc status by layered post-transcriptional control: during zinc deficiency ZIP4 mRNA is stabilized and protein accumulates at the apical membrane, whereas zinc repletion drives ZIP4 internalization and lysosomal degradation [PMID:18020946]. Under prolonged deficiency the extracellular N-terminal ectodomain is proteolytically cleaved at a metalloproteinase site following endocytosis and recycling, leaving the eight-transmembrane C-terminal half at the surface; acrodermatitis enteropathica mutations near this site block cleavage [PMID:18936158]. Loss-of-function mutations in SLC39A4 cause acrodermatitis enteropathica, and disease alleles act by abolishing cell-surface expression and zinc transport [PMID:12068297, PMID:24586184]. ZIP4 is essential for early embryonic development and for intestinal stem cell niche integrity, where its loss depletes Paneth cell labile zinc, reprograms Paneth cells toward a goblet-like state, and reduces crypt cell division and mTOR signaling [PMID:17483098, PMID:22737083]. Aberrant ZIP4 overexpression in pancreatic, gallbladder, and gastric cancers raises intracellular zinc and promotes proliferation, migration, and resistance to copper-induced cuproptosis [PMID:18003899, PMID:33727860, PMID:42056258].","teleology":[{"year":2002,"claim":"Established the molecular identity of the intestinal zinc uptake transporter and linked it to a human disease, answering why acrodermatitis enteropathica disrupts zinc absorption.","evidence":"Chromosomal mapping, expression analysis, and mutational analysis in eight AE families","pmids":["12068297"],"confidence":"High","gaps":["Did not define the transport mechanism or directionality biochemically","Did not address regulation by zinc status"]},{"year":2007,"claim":"Showed that ZIP4 abundance is dynamically matched to zinc availability through mRNA stability and protein trafficking, explaining how the transporter adapts to dietary zinc.","evidence":"In vivo dietary zinc manipulation in mice with immunofluorescence and mRNA stability assays in Hepa cells","pmids":["18020946"],"confidence":"High","gaps":["Molecular machinery driving internalization/degradation not identified","Signal sensing zinc status not defined"]},{"year":2007,"claim":"Demonstrated that ZIP4 is required for early morphogenesis and that gene dosage governs sensitivity to maternal zinc deficiency, establishing its developmental essentiality.","evidence":"Homozygous and heterozygous Zip4 knockout mice with dietary zinc manipulation and developmental phenotyping","pmids":["17483098"],"confidence":"High","gaps":["Tissue-specific contributions to lethality not dissected","Downstream zinc-dependent developmental pathways unresolved"]},{"year":2007,"claim":"Provided gain-of-function evidence that ZIP4-mediated zinc uptake drives tumor growth, opening a cancer-relevant axis for the transporter.","evidence":"Stable overexpression in pancreatic cancer cells with in vitro proliferation and xenograft models","pmids":["18003899"],"confidence":"High","gaps":["Downstream signaling linking zinc to proliferation not identified","Endogenous regulation in tumors not addressed"]},{"year":2008,"claim":"Defined a second regulatory mechanism—proteolytic ectodomain cleavage during prolonged deficiency—and linked it to a disease mutation hotspot, refining how ZIP4 is processed at the membrane.","evidence":"In vivo intestinal analysis plus transfected MDCK/CaCo2/HEK293 cells with endocytosis inhibitors and disease-mutation analysis","pmids":["18936158"],"confidence":"High","gaps":["Identity of the responsible protease not established","Functional consequence of the cleaved transporter on transport rate unresolved"]},{"year":2010,"claim":"Connected ZIP4 to cell survival and motility phenotypes, indicating roles beyond bulk zinc supply.","evidence":"RNAi knockdown and overexpression in Hepa and MCF-7 cells with cell cycle, apoptosis, and migration assays","pmids":["20957146"],"confidence":"Medium","gaps":["No in vivo validation for these mechanisms","Molecular effectors of migration not identified"]},{"year":2012,"claim":"Revealed that intestinal ZIP4 maintains the stem cell niche by supplying labile zinc to Paneth cells and sustaining mTOR signaling, mechanistically grounding its intestinal essentiality.","evidence":"Tamoxifen-inducible enterocyte-specific Zip4 knockout mouse with histology, elemental analysis, and mTOR pathway assays","pmids":["22737083"],"confidence":"High","gaps":["Mechanism coupling zinc to Paneth cell identity unknown","Direct link between zinc and mTOR attenuation not defined"]},{"year":2014,"claim":"Resolved how codon-372 variants alter function, distinguishing surface-expression loss as the basis of pathogenicity versus a partial-function polymorphism.","evidence":"Transient expression of ZIP4 variants in HeLa cells with surface expression and zinc uptake assays","pmids":["24586184"],"confidence":"Medium","gaps":["Structural basis of trafficking defect not determined","Single cell-line context"]},{"year":2021,"claim":"Quantitatively established ZIP4 as the dominant transporter setting fractional dietary zinc absorption among all intestinal zinc transporters.","evidence":"67Zn oral isotope absorption assay in mice with ICP-MS and qPCR profiling of 24 zinc transporters","pmids":["34843931"],"confidence":"Medium","gaps":["Correlational design limits causal inference","Adult and human relevance not addressed"]},{"year":2021,"claim":"Extended the pro-tumor role of ZIP4 to gallbladder cancer through standard loss/gain-of-function phenotyping.","evidence":"siRNA and overexpression in GBC-SD and NOZ cells with proliferation, migration, and xenograft assays","pmids":["33727860"],"confidence":"Low","gaps":["No specific pathway mechanism identified","Single lab, phenotype-only"]},{"year":2024,"claim":"Placed SLC39A4 downstream of a transcriptional regulatory cascade in colorectal cancer, identifying an upstream activator and its mRNA stabilizer.","evidence":"Reporter assays, RNA immunoprecipitation, mRNA stability and knockdown/overexpression experiments in CRC cell lines","pmids":["38768927"],"confidence":"Low","gaps":["Single lab; mechanism of UKLF-driven SLC39A4 transcription not detailed","In vivo relevance not shown"]},{"year":2026,"claim":"Identified m6A-dependent stabilization of SLC39A4 mRNA by YTHDF1 and linked ZIP4 to suppression of copper-induced cuproptosis in gastric cancer, adding an RNA-modification regulatory layer and a metal-crosstalk function.","evidence":"Lentiviral overexpression/knockdown, m6A luciferase reporter mutagenesis, RIP, and cuproptosis assays in cells and xenografts","pmids":["42056258"],"confidence":"Medium","gaps":["Mechanism by which zinc uptake counters cuproptosis not defined","Single lab"]},{"year":null,"claim":"The biochemical transport mechanism (stoichiometry, directionality, pore residues) and the identity of the protease and zinc-sensing machinery controlling ZIP4 trafficking remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No reconstituted transport assay defining transport mechanism","Protease responsible for ectodomain cleavage unidentified","Zinc-status sensor governing mRNA stability and trafficking unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,5,7,9]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,3,7]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,4]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,5]}],"complexes":[],"partners":[],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q6P5W5","full_name":"Zinc transporter ZIP4","aliases":["Solute carrier family 39 member 4","Zrt- and Irt-like protein 4","ZIP-4"],"length_aa":647,"mass_kda":68.4,"function":"Selective transporter that mediates the uptake of Zn(2+) (PubMed:17202136, PubMed:22242765, PubMed:27321477, PubMed:28875161, PubMed:31164399, PubMed:31914589, PubMed:31979155, PubMed:33837739, PubMed:36473915). Plays an essential role for dietary zinc uptake from small intestine (By similarity). The Zn(2+) uniporter activity is regulated by zinc availability (PubMed:17202136, PubMed:32348750). Also exhibits polyspecific binding and transport of Cu(2+), Cd(2+) and possibly Ni(2+) but at higher concentrations (PubMed:22242765, PubMed:31914589)","subcellular_location":"Cell membrane; Recycling endosome membrane; Apical cell membrane","url":"https://www.uniprot.org/uniprotkb/Q6P5W5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SLC39A4","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/SLC39A4","total_profiled":1310},"omim":[{"mim_id":"608118","title":"ZINC DEFICIENCY, TRANSIENT NEONATAL; TNZD","url":"https://www.omim.org/entry/608118"},{"mim_id":"607059","title":"SOLUTE CARRIER FAMILY 39 (ZINC TRANSPORTER), MEMBER 4; SLC39A4","url":"https://www.omim.org/entry/607059"},{"mim_id":"201100","title":"ACRODERMATITIS ENTEROPATHICA, ZINC-DEFICIENCY TYPE; AEZ","url":"https://www.omim.org/entry/201100"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"intestine","ntpm":82.8}],"url":"https://www.proteinatlas.org/search/SLC39A4"},"hgnc":{"alias_symbol":["ZIP4","ZIP-4","AWMS2"],"prev_symbol":["AEZ"]},"alphafold":{"accession":"Q6P5W5","domains":[{"cath_id":"-","chopping":"29-200","consensus_level":"high","plddt":84.0163,"start":29,"end":200},{"cath_id":"-","chopping":"324-390_399-425_492-642","consensus_level":"high","plddt":84.4609,"start":324,"end":642},{"cath_id":"1.10.238","chopping":"204-236_268-312","consensus_level":"medium","plddt":87.0358,"start":204,"end":312}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6P5W5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q6P5W5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q6P5W5-F1-predicted_aligned_error_v6.png","plddt_mean":74.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SLC39A4","jax_strain_url":"https://www.jax.org/strain/search?query=SLC39A4"},"sequence":{"accession":"Q6P5W5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q6P5W5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q6P5W5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6P5W5"}},"corpus_meta":[{"pmid":"12068297","id":"PMC_12068297","title":"Identification of SLC39A4, a gene involved in acrodermatitis enteropathica.","date":"2002","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/12068297","citation_count":355,"is_preprint":false},{"pmid":"18003899","id":"PMC_18003899","title":"Aberrant expression of zinc transporter ZIP4 (SLC39A4) significantly contributes to human pancreatic cancer pathogenesis and progression.","date":"2007","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/18003899","citation_count":221,"is_preprint":false},{"pmid":"18020946","id":"PMC_18020946","title":"Novel zinc-responsive post-transcriptional mechanisms reciprocally regulate expression of the mouse Slc39a4 and Slc39a5 zinc transporters (Zip4 and Zip5).","date":"2007","source":"Biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18020946","citation_count":130,"is_preprint":false},{"pmid":"22737083","id":"PMC_22737083","title":"A mouse model of acrodermatitis enteropathica: loss of intestine zinc transporter ZIP4 (Slc39a4) disrupts the stem cell niche and intestine integrity.","date":"2012","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22737083","citation_count":107,"is_preprint":false},{"pmid":"18936158","id":"PMC_18936158","title":"Novel proteolytic processing of the ectodomain of the zinc transporter ZIP4 (SLC39A4) during zinc deficiency is inhibited by acrodermatitis enteropathica mutations.","date":"2008","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18936158","citation_count":102,"is_preprint":false},{"pmid":"17483098","id":"PMC_17483098","title":"The mouse acrodermatitis enteropathica gene Slc39a4 (Zip4) is essential for early development and heterozygosity causes hypersensitivity to zinc deficiency.","date":"2007","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/17483098","citation_count":96,"is_preprint":false},{"pmid":"19370757","id":"PMC_19370757","title":"An update on mutations of the SLC39A4 gene in acrodermatitis enteropathica.","date":"2009","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/19370757","citation_count":94,"is_preprint":false},{"pmid":"20957146","id":"PMC_20957146","title":"Zip4 (Slc39a4) expression is activated in hepatocellular carcinomas and functions to repress apoptosis, enhance cell cycle and increase migration.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20957146","citation_count":70,"is_preprint":false},{"pmid":"12955721","id":"PMC_12955721","title":"Mutation spectrum of human SLC39A4 in a panel of patients with acrodermatitis enteropathica.","date":"2003","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/12955721","citation_count":49,"is_preprint":false},{"pmid":"12787121","id":"PMC_12787121","title":"Novel SLC39A4 mutations in acrodermatitis enteropathica.","date":"2003","source":"The Journal of investigative dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/12787121","citation_count":45,"is_preprint":false},{"pmid":"24586184","id":"PMC_24586184","title":"Extreme population differences in the human zinc transporter ZIP4 (SLC39A4) are explained by positive selection in Sub-Saharan Africa.","date":"2014","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24586184","citation_count":30,"is_preprint":false},{"pmid":"16714095","id":"PMC_16714095","title":"Identification of a unique splice site variant in SLC39A4 in bovine hereditary zinc deficiency, lethal trait A46: An animal model of acrodermatitis enteropathica.","date":"2006","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/16714095","citation_count":24,"is_preprint":false},{"pmid":"34843931","id":"PMC_34843931","title":"Slc39a4 in the small intestine predicts zinc absorption and utilization: a comprehensive analysis of zinc transporter expression in response to diets of varied zinc content in young mice.","date":"2021","source":"The Journal of nutritional biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/34843931","citation_count":18,"is_preprint":false},{"pmid":"21165302","id":"PMC_21165302","title":"Congenital zinc deficiency from mutations of the SLC39A4 gene as the genetic background of acrodermatitis enteropathica.","date":"2010","source":"Journal of Korean medical science","url":"https://pubmed.ncbi.nlm.nih.gov/21165302","citation_count":15,"is_preprint":false},{"pmid":"31987033","id":"PMC_31987033","title":"Analysis of the relationship between the mutation site of the SLC39A4 gene and acrodermatitis enteropathica by reporting a rare Chinese twin: a case report and review of the literature.","date":"2020","source":"BMC pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/31987033","citation_count":14,"is_preprint":false},{"pmid":"25780817","id":"PMC_25780817","title":"Acrodermatitis Enteropathica: A Novel SLC39A4 Gene Mutation in a Patient with Normal Zinc Levels.","date":"2015","source":"Pediatric dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/25780817","citation_count":14,"is_preprint":false},{"pmid":"24647711","id":"PMC_24647711","title":"Effects of combined administration of rapamycin, tolvaptan, and AEZ-131 on the progression of polycystic disease in PCK rats.","date":"2014","source":"American journal of physiology. Renal physiology","url":"https://pubmed.ncbi.nlm.nih.gov/24647711","citation_count":13,"is_preprint":false},{"pmid":"22082465","id":"PMC_22082465","title":"Novel SLC39A4 mutation in acrodermatitis enteropathica.","date":"2011","source":"Pediatric dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/22082465","citation_count":10,"is_preprint":false},{"pmid":"20300938","id":"PMC_20300938","title":"One novel homozygous mutation of SLC39A4 gene in a Chinese patient with acrodermatitis enteropathica.","date":"2010","source":"Archives of dermatological research","url":"https://pubmed.ncbi.nlm.nih.gov/20300938","citation_count":9,"is_preprint":false},{"pmid":"23430849","id":"PMC_23430849","title":"A Zinc Sulphate-Resistant Acrodermatitis Enteropathica Patient with a Novel Mutation in SLC39A4 Gene.","date":"2011","source":"JIMD reports","url":"https://pubmed.ncbi.nlm.nih.gov/23430849","citation_count":9,"is_preprint":false},{"pmid":"38768927","id":"PMC_38768927","title":"UKLF/PCBP2 axis governs the colorectal cancer development by transcriptionally activating SLC39A4.","date":"2024","source":"Biochimica et biophysica acta. Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/38768927","citation_count":8,"is_preprint":false},{"pmid":"33727860","id":"PMC_33727860","title":"Knockdown of SLC39A4 Expression Inhibits the Proliferation and Motility of Gallbladder Cancer Cells and Tumor Formation in Nude Mice.","date":"2021","source":"Cancer management and research","url":"https://pubmed.ncbi.nlm.nih.gov/33727860","citation_count":8,"is_preprint":false},{"pmid":"16819703","id":"PMC_16819703","title":"[Acrodermatitis enteropathica (AE) is caused by mutations in the zinc transporter gene SLC39A4].","date":"2006","source":"Klinische Padiatrie","url":"https://pubmed.ncbi.nlm.nih.gov/16819703","citation_count":8,"is_preprint":false},{"pmid":"36479285","id":"PMC_36479285","title":"Case report: Acrodermatitis enteropathica result from a novel SLC39A4 gene mutation.","date":"2022","source":"Frontiers in pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/36479285","citation_count":6,"is_preprint":false},{"pmid":"21906148","id":"PMC_21906148","title":"Acrodermatitis enteropathica: a novel SLC39A4 gene mutation found in a patient with an early-onset.","date":"2011","source":"Pediatric dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/21906148","citation_count":3,"is_preprint":false},{"pmid":"28604961","id":"PMC_28604961","title":"[Analysis of SLC39A4 gene mutation in a patient with acrodermatitis enteropathica].","date":"2017","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28604961","citation_count":2,"is_preprint":false},{"pmid":"34573291","id":"PMC_34573291","title":"A Missense Variant in SLC39A4 in a Litter of Turkish Van Cats with Acrodermatitis Enteropathica.","date":"2021","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/34573291","citation_count":1,"is_preprint":false},{"pmid":"25391167","id":"PMC_25391167","title":"SLC39A4 mutation in zinc deficiency patients.","date":"2014","source":"Journal of the Medical Association of Thailand = Chotmaihet thangphaet","url":"https://pubmed.ncbi.nlm.nih.gov/25391167","citation_count":0,"is_preprint":false},{"pmid":"41385451","id":"PMC_41385451","title":"Heterozygous Variants of the SLC39A4 Gene and Possible Increased Risk for Developing Acrodermatitis Enteropathica with Kaposi's Varicelliform Eruption.","date":"2025","source":"The American journal of case reports","url":"https://pubmed.ncbi.nlm.nih.gov/41385451","citation_count":0,"is_preprint":false},{"pmid":"42056258","id":"PMC_42056258","title":"YTHDF1/SLC39A4 signaling axis promotes gastric cancer cell proliferation by suppressing cuproptosis ex vivo and in vitro.","date":"2026","source":"Cancer gene therapy","url":"https://pubmed.ncbi.nlm.nih.gov/42056258","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":14967,"output_tokens":3181,"usd":0.046308,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10858,"output_tokens":3459,"usd":0.070383,"stage2_stop_reason":"end_turn"},"total_usd":0.116691,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"SLC39A4 encodes a ZIP-family zinc transporter protein expressed in the duodenum/jejunum; mutations in SLC39A4 cause acrodermatitis enteropathica, establishing it as the intestinal zinc uptake transporter responsible for this disease.\",\n      \"method\": \"Chromosomal mapping, expression analysis, and mutational analysis in eight AE-affected families\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct mutational analysis in multiple families, replicated independently, foundational disease-gene identification\",\n      \"pmids\": [\"12068297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"ZIP4 protein abundance is regulated post-transcriptionally: during zinc deficiency, ZIP4 mRNA stability increases and ZIP4 protein localizes to apical membranes; zinc repletion triggers ZIP4 internalization and degradation in enterocytes and visceral endoderm cells.\",\n      \"method\": \"In vivo dietary zinc manipulation in mice combined with immunofluorescence localization and mRNA stability assays in mouse Hepa cells\",\n      \"journal\": \"Biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (mRNA stability assay, transcription rate measurement, protein localization, in vivo mouse experiments), replicated across cell types and in vivo\",\n      \"pmids\": [\"18020946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Homozygous Zip4 knockout mouse embryos die during early morphogenesis, demonstrating that ZIP4 is essential for early embryonic development; heterozygosity causes hypersensitivity to zinc deficiency with developmental defects exacerbated by maternal zinc deficiency and ameliorated by zinc excess.\",\n      \"method\": \"Gene knockout mouse model with dietary zinc manipulation; developmental phenotyping\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function in mouse with defined phenotypic rescue by dietary zinc, multiple developmental endpoints assessed\",\n      \"pmids\": [\"17483098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"During prolonged zinc deficiency, the extracellular N-terminal ectodomain of ZIP4 is proteolytically cleaved, leaving the eight-transmembrane C-terminal half on the plasma membrane; this cleavage is blocked by acrodermatitis enteropathica mutations near a predicted metalloproteinase cleavage site and is attenuated by inhibitors of endocytosis, suggesting ectodomain cleavage occurs following internalization and recycling back to the plasma membrane.\",\n      \"method\": \"In vivo intestinal analysis and transfected MDCK, CaCo2, and HEK293 cell lines; inhibitor studies; disease mutation analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple cell systems, in vivo validation, pharmacological inhibition, and disease mutation structure-function analysis in a single study\",\n      \"pmids\": [\"18936158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Enterocyte-specific knockout of Zip4 in mice causes loss of labile zinc in Paneth cells, reprogramming of Paneth cells toward a goblet cell-like state (loss of Sox9 and lysozyme, accumulation of mucin), dysplasia of intestinal crypts, diminished small intestine cell division, and attenuated mTOR1 activity in villus enterocytes indicative of increased catabolism, establishing ZIP4 as essential for intestinal stem cell niche integrity.\",\n      \"method\": \"Tamoxifen-inducible, enterocyte-specific Zip4 knockout mouse; immunohistochemistry; elemental analysis; mTOR pathway assay\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional genetic knockout with multiple orthogonal readouts (histology, gene expression, elemental analysis, signaling pathway)\",\n      \"pmids\": [\"22737083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Forced overexpression of ZIP4 in pancreatic cancer cells increases intracellular zinc levels, increases cell proliferation ~2-fold in vitro, and dramatically increases tumor volume (13-fold) and peritoneal dissemination in xenograft mouse models, establishing a functional role for ZIP4-mediated zinc uptake in promoting tumor growth.\",\n      \"method\": \"Stable overexpression in pancreatic cancer cell lines; in vitro proliferation assay; subcutaneous and orthotopic xenograft mouse models\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — gain-of-function in vitro and in vivo with multiple endpoints including zinc measurement, proliferation, and tumor growth\",\n      \"pmids\": [\"18003899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RNAi knockdown of Zip4 in mouse Hepa cells significantly increases apoptosis and slows G0/G1-to-S phase progression under zinc-deficient conditions; forced overexpression of Zip4 in Hepa and MCF-7 cells enhances in vitro migration, while knockdown depresses migration.\",\n      \"method\": \"RNAi knockdown; cell cycle analysis after hydroxyurea block; apoptosis assay; cell migration assay; forced overexpression\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple cellular assays in cultured cells but no in vivo validation for these specific mechanisms; single lab\",\n      \"pmids\": [\"20957146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The Leu372Val polymorphism and disease-causing mutations Leu372Pro and Leu372Arg at the same codon differentially affect ZIP4 surface expression and zinc uptake: the two AE mutations abolish cell surface expression and nearly eliminate zinc uptake, while the Val372 variant shows significantly reduced surface protein expression, reduced basal intracellular zinc, and reduced zinc uptake compared to Leu372.\",\n      \"method\": \"Transient overexpression of ZIP4 variants in HeLa cells; surface protein expression assay; zinc uptake assay\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional zinc uptake assay plus surface expression assay in human cells, single lab, multiple variants tested\",\n      \"pmids\": [\"24586184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"A splice-site variant in bovine SLC39A4 ortholog causes exon skipping, producing a protein predicted to lack two critical motifs in adjacent transmembrane domains implicated in forming the zinc transport pore, establishing loss of these transmembrane domains as the molecular basis of impaired zinc absorption in bovine hereditary zinc deficiency (lethal trait A46).\",\n      \"method\": \"Sequencing of bovine SLC39A4 ortholog; splice variant characterization; structural domain analysis\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — genetic and molecular characterization of a disease variant in an animal model; no in vitro functional reconstitution of transport activity\",\n      \"pmids\": [\"16714095\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Among all intestinal zinc transporters, Slc39a4 expression is the only one positively correlated with fractional zinc absorption (liver and plasma 67Zn appearance), identifying SLC39A4/ZIP4 as the primary determinant of dietary zinc absorption in young mice.\",\n      \"method\": \"Stable isotope (67Zn) oral gavage absorption assay in mice fed varied zinc diets; ICP-MS measurement; qPCR expression profiling of all 24 zinc transporters across intestinal segments\",\n      \"journal\": \"The Journal of nutritional biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo isotope absorption assay with correlation analysis across dietary conditions; single lab, correlational design limits mechanistic inference\",\n      \"pmids\": [\"34843931\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SLC39A4 knockdown in gallbladder cancer cell lines suppresses proliferation, migration, and xenograft tumor growth, while overexpression promotes proliferation, migration, and inhibits apoptosis, indicating ZIP4 modulates survival and metastasis-related signaling in GBC cells.\",\n      \"method\": \"siRNA knockdown and overexpression in GBC-SD and NOZ cells; MTT assay; colony formation; wound-healing and Transwell migration assays; nude mouse xenograft\",\n      \"journal\": \"Cancer management and research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — standard knockdown/overexpression phenotypic assays, single lab, no specific pathway mechanism identified\",\n      \"pmids\": [\"33727860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UKLF (ubiquitous Krüppel-like factor) transcriptionally activates SLC39A4 expression, while PCBP2 stabilizes UKLF mRNA by binding its 3'-UTR, placing SLC39A4 as a downstream transcriptional target in a PCBP2/UKLF/SLC39A4 pathway in colorectal cancer cells.\",\n      \"method\": \"Reporter assays, RNA immunoprecipitation, mRNA stability assay, knockdown/overexpression experiments in CRC cell lines\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, transcriptional regulation shown by reporter assay but mechanistic detail of how UKLF activates SLC39A4 transcription is limited in the abstract\",\n      \"pmids\": [\"38768927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"YTHDF1 binds SLC39A4 mRNA and stabilizes its transcripts in an m6A-dependent manner (mutation of the m6A site in SLC39A4 coding sequence abolishes YTHDF1-mediated regulation); SLC39A4 overexpression attenuates cuproptosis induced by CuCl2/elesclomol treatment, while SLC39A4 knockdown potentiates it, establishing a role for ZIP4 in suppressing cuproptosis in gastric cancer cells.\",\n      \"method\": \"Lentiviral stable overexpression/knockdown; dual-luciferase m6A reporter assay; RNA immunoprecipitation for YTHDF1-SLC39A4 mRNA binding; proliferation and cuproptosis marker assays in cell lines and xenograft models\",\n      \"journal\": \"Cancer gene therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — m6A site mutagenesis with luciferase assay, RIP for direct binding, functional cuproptosis assay in vitro and in vivo; single lab\",\n      \"pmids\": [\"42056258\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SLC39A4/ZIP4 is an intestinal apical zinc uptake transporter whose expression is dynamically regulated by zinc status through mRNA stability changes and protein trafficking (internalization and lysosomal degradation upon zinc repletion, or proteolytic ectodomain cleavage during prolonged deficiency); it is essential for embryonic development and intestinal stem cell niche integrity in mice, with its loss causing acrodermatitis enteropathica, and its aberrant overexpression in multiple cancers promoting proliferation, migration, and cuproptosis resistance partly through upstream m6A-dependent mRNA stabilization by YTHDF1.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SLC39A4 (ZIP4) is the principal apical zinc uptake transporter of the small intestine and the primary genetic determinant of dietary zinc absorption [#0, #9]. Its abundance is tuned to zinc status by layered post-transcriptional control: during zinc deficiency ZIP4 mRNA is stabilized and protein accumulates at the apical membrane, whereas zinc repletion drives ZIP4 internalization and lysosomal degradation [#1]. Under prolonged deficiency the extracellular N-terminal ectodomain is proteolytically cleaved at a metalloproteinase site following endocytosis and recycling, leaving the eight-transmembrane C-terminal half at the surface; acrodermatitis enteropathica mutations near this site block cleavage [#3]. Loss-of-function mutations in SLC39A4 cause acrodermatitis enteropathica, and disease alleles act by abolishing cell-surface expression and zinc transport [#0, #7]. ZIP4 is essential for early embryonic development and for intestinal stem cell niche integrity, where its loss depletes Paneth cell labile zinc, reprograms Paneth cells toward a goblet-like state, and reduces crypt cell division and mTOR signaling [#2, #4]. Aberrant ZIP4 overexpression in pancreatic, gallbladder, and gastric cancers raises intracellular zinc and promotes proliferation, migration, and resistance to copper-induced cuproptosis [#5, #10, #12].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established the molecular identity of the intestinal zinc uptake transporter and linked it to a human disease, answering why acrodermatitis enteropathica disrupts zinc absorption.\",\n      \"evidence\": \"Chromosomal mapping, expression analysis, and mutational analysis in eight AE families\",\n      \"pmids\": [\"12068297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the transport mechanism or directionality biochemically\", \"Did not address regulation by zinc status\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Showed that ZIP4 abundance is dynamically matched to zinc availability through mRNA stability and protein trafficking, explaining how the transporter adapts to dietary zinc.\",\n      \"evidence\": \"In vivo dietary zinc manipulation in mice with immunofluorescence and mRNA stability assays in Hepa cells\",\n      \"pmids\": [\"18020946\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular machinery driving internalization/degradation not identified\", \"Signal sensing zinc status not defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrated that ZIP4 is required for early morphogenesis and that gene dosage governs sensitivity to maternal zinc deficiency, establishing its developmental essentiality.\",\n      \"evidence\": \"Homozygous and heterozygous Zip4 knockout mice with dietary zinc manipulation and developmental phenotyping\",\n      \"pmids\": [\"17483098\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specific contributions to lethality not dissected\", \"Downstream zinc-dependent developmental pathways unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Provided gain-of-function evidence that ZIP4-mediated zinc uptake drives tumor growth, opening a cancer-relevant axis for the transporter.\",\n      \"evidence\": \"Stable overexpression in pancreatic cancer cells with in vitro proliferation and xenograft models\",\n      \"pmids\": [\"18003899\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream signaling linking zinc to proliferation not identified\", \"Endogenous regulation in tumors not addressed\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined a second regulatory mechanism—proteolytic ectodomain cleavage during prolonged deficiency—and linked it to a disease mutation hotspot, refining how ZIP4 is processed at the membrane.\",\n      \"evidence\": \"In vivo intestinal analysis plus transfected MDCK/CaCo2/HEK293 cells with endocytosis inhibitors and disease-mutation analysis\",\n      \"pmids\": [\"18936158\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the responsible protease not established\", \"Functional consequence of the cleaved transporter on transport rate unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Connected ZIP4 to cell survival and motility phenotypes, indicating roles beyond bulk zinc supply.\",\n      \"evidence\": \"RNAi knockdown and overexpression in Hepa and MCF-7 cells with cell cycle, apoptosis, and migration assays\",\n      \"pmids\": [\"20957146\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo validation for these mechanisms\", \"Molecular effectors of migration not identified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Revealed that intestinal ZIP4 maintains the stem cell niche by supplying labile zinc to Paneth cells and sustaining mTOR signaling, mechanistically grounding its intestinal essentiality.\",\n      \"evidence\": \"Tamoxifen-inducible enterocyte-specific Zip4 knockout mouse with histology, elemental analysis, and mTOR pathway assays\",\n      \"pmids\": [\"22737083\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism coupling zinc to Paneth cell identity unknown\", \"Direct link between zinc and mTOR attenuation not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Resolved how codon-372 variants alter function, distinguishing surface-expression loss as the basis of pathogenicity versus a partial-function polymorphism.\",\n      \"evidence\": \"Transient expression of ZIP4 variants in HeLa cells with surface expression and zinc uptake assays\",\n      \"pmids\": [\"24586184\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of trafficking defect not determined\", \"Single cell-line context\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Quantitatively established ZIP4 as the dominant transporter setting fractional dietary zinc absorption among all intestinal zinc transporters.\",\n      \"evidence\": \"67Zn oral isotope absorption assay in mice with ICP-MS and qPCR profiling of 24 zinc transporters\",\n      \"pmids\": [\"34843931\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Correlational design limits causal inference\", \"Adult and human relevance not addressed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Extended the pro-tumor role of ZIP4 to gallbladder cancer through standard loss/gain-of-function phenotyping.\",\n      \"evidence\": \"siRNA and overexpression in GBC-SD and NOZ cells with proliferation, migration, and xenograft assays\",\n      \"pmids\": [\"33727860\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No specific pathway mechanism identified\", \"Single lab, phenotype-only\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placed SLC39A4 downstream of a transcriptional regulatory cascade in colorectal cancer, identifying an upstream activator and its mRNA stabilizer.\",\n      \"evidence\": \"Reporter assays, RNA immunoprecipitation, mRNA stability and knockdown/overexpression experiments in CRC cell lines\",\n      \"pmids\": [\"38768927\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single lab; mechanism of UKLF-driven SLC39A4 transcription not detailed\", \"In vivo relevance not shown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identified m6A-dependent stabilization of SLC39A4 mRNA by YTHDF1 and linked ZIP4 to suppression of copper-induced cuproptosis in gastric cancer, adding an RNA-modification regulatory layer and a metal-crosstalk function.\",\n      \"evidence\": \"Lentiviral overexpression/knockdown, m6A luciferase reporter mutagenesis, RIP, and cuproptosis assays in cells and xenografts\",\n      \"pmids\": [\"42056258\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which zinc uptake counters cuproptosis not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The biochemical transport mechanism (stoichiometry, directionality, pore residues) and the identity of the protease and zinc-sensing machinery controlling ZIP4 trafficking remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reconstituted transport assay defining transport mechanism\", \"Protease responsible for ectodomain cleavage unidentified\", \"Zinc-status sensor governing mRNA stability and trafficking unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 5, 7, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 3, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}