{"gene":"CNNM1","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2003,"finding":"ACDP1 (CNNM1) protein is predominantly localized in the nucleus of HeLa cells, as determined by immunofluorescence staining of permeabilized cells.","method":"Immunofluorescence staining of permeabilized HeLa cells","journal":"Gene","confidence":"Low","confidence_rationale":"Tier 3 — single localization experiment without functional follow-up in this study","pmids":["12657465"],"is_preprint":false},{"year":2004,"finding":"Mouse Acdp1 (Cnnm1) protein is predominantly localized on the plasma membrane of hippocampus neurons, as shown by immunostaining; structural homology to bacterial CorC (Mg2+/Co2+ efflux protein) suggests a role in ion transport.","method":"Immunostaining of mouse hippocampus neurons; sequence homology analysis","journal":"BMC genomics","confidence":"Low","confidence_rationale":"Tier 3 — localization by immunostaining without direct functional consequence demonstrated","pmids":["14723793"],"is_preprint":false},{"year":2007,"finding":"ACDP-1 (CNNM1) binds copper with high affinity (nanomolar), localizes to the cytoplasm, and modifies cellular copper retention when expressed in cells, consistent with a role as a copper chaperone or storage protein.","method":"Immobilized metal affinity chromatography, isothermal titration calorimetry, cellular copper retention assay, subcellular localization","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 1–2 — in vitro binding assay with quantitative ITC plus cellular functional assay, single lab","pmids":["17608643"],"is_preprint":false},{"year":2016,"finding":"CNNM1 is expressed in c-KIT- and OCT3/4-positive spermatogonial stem cells in mouse testis; silencing of Cnnm1 in GC1-spg cells reduces G1-phase cells and increases S and G2/M populations, and retinoic acid downregulates Cnnm1 expression, indicating a role in spermatogonial cell cycle regulation and stemness maintenance.","method":"Immunofluorescence, siRNA knockdown, flow cytometry cell cycle analysis, RT-PCR","journal":"Biology of reproduction","confidence":"Medium","confidence_rationale":"Tier 2 — KD with defined cell-cycle phenotype plus localization, single lab, multiple methods","pmids":["27251091"],"is_preprint":false},{"year":2021,"finding":"Native TRPM7 channels in rodent brain form high-molecular-weight complexes containing CNNM1-4 and ARL15, as identified by multi-epitope affinity purification and quantitative mass spectrometry; heterologous reconstitution confirmed TRPM7/CNNM/ARL15 ternary complex formation, which specifically impacts TRPM7 activity.","method":"Multi-epitope affinity purification, high-resolution quantitative mass spectrometry, heterologous reconstitution, electrophysiology","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 — native complex purification from brain + MS + reconstitution + functional activity measurement","pmids":["34766907"],"is_preprint":false},{"year":2021,"finding":"ARL15 interacts with CNNM family proteins (including CNNM1) at their C-terminal CBS domains, promotes complex N-glycosylation of CNNMs, co-localizes with CNNM2 in endoplasmic reticulum, Golgi apparatus, and plasma membrane of kidney cells, and ARL15 knockdown increases Mg2+ uptake—establishing ARL15 as a negative regulator of Mg2+ transport via CNNM N-glycosylation.","method":"Co-immunoprecipitation, in silico modeling, immunocytochemistry, stable isotope 25Mg2+ uptake assay, siRNA knockdown","journal":"Cellular and molecular life sciences","confidence":"High","confidence_rationale":"Tier 2 — reciprocal biochemical interaction, functional isotope uptake assay, subcellular co-localization, multiple cell lines","pmids":["34089346"],"is_preprint":false},{"year":2025,"finding":"The CNNM transmembrane (DUF21) domain is sufficient to mediate assembly of the CNNM2-TRPM7 complex, while the CBS-pair and CNBH domains provide additional contact points; the CBS-pair domain modulates TRPM7 channel activity and is required for ARL15-mediated inhibition of TRPM7; the CNBH domain binds the TRPM7 kinase domain and modestly enhances its catalytic activity in vitro.","method":"Co-immunoprecipitation of deletion constructs, electrophysiology, in vitro kinase assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — domain dissection with multiple interaction assays, electrophysiology, and in vitro kinase assay in one study","pmids":["40962059"],"is_preprint":false},{"year":2009,"finding":"Cnnm1 is a downstream transcriptional target of both STAT3 and Nanog in mouse embryonic stem cells; knockdown increases differentiation markers and frequency of differentiated colonies, indicating a role in maintenance of the undifferentiated state.","method":"Hormone-dependent STAT3 system, microarray, siRNA knockdown, self-renewal assay, differentiation marker analysis","journal":"Stem cells","confidence":"Medium","confidence_rationale":"Tier 2 — functional knockdown with defined phenotype, transcriptional target validated, single lab","pmids":["19544440"],"is_preprint":false},{"year":2025,"finding":"Overexpression of CNNM1 in C18-4 spermatogonial cells upregulates genes involved in cell proliferation, nucleic acid metabolism, and cell cycle regulation; CNNM1 knockdown alters cell cycle progression, supporting a role in SSC self-renewal and survival.","method":"Overexpression, siRNA knockdown, proteome profiling, cell cycle analysis","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 — preprint, single lab, functional assays without reconstitution or epistasis","pmids":["bio_10.1101_2025.10.20.683346"],"is_preprint":true}],"current_model":"CNNM1 is a transmembrane protein that forms high-molecular-weight complexes with the ion channel-kinase TRPM7 (through its DUF21, CBS-pair, and CNBH domains) and with ARL15 in native brain and kidney tissues, where it regulates TRPM7 channel and kinase activities; in the cytoplasm, CNNM1 acts as a high-affinity copper-binding protein (chaperone/storage), and in the nucleus/stem-cell context it is a STAT3 and Nanog transcriptional target that sustains spermatogonial stem cell self-renewal and pluripotent cell maintenance by controlling cell cycle progression."},"narrative":{"teleology":[{"year":2003,"claim":"Initial localization studies placed CNNM1 in the nucleus of HeLa cells, raising questions about whether this protein functions as a nuclear factor rather than a membrane transporter.","evidence":"Immunofluorescence in permeabilized HeLa cells","pmids":["12657465"],"confidence":"Low","gaps":["Single cell line; no orthogonal biochemical fractionation","Nuclear function not tested","Antibody specificity not rigorously validated"]},{"year":2004,"claim":"In contrast, localization in native neurons placed CNNM1 at the plasma membrane and sequence homology to bacterial CorC suggested an ion transport function, reframing the protein as a potential divalent cation transporter.","evidence":"Immunostaining of mouse hippocampal neurons; bioinformatic analysis","pmids":["14723793"],"confidence":"Low","gaps":["No direct ion transport activity demonstrated","Conflicting localization with prior HeLa study unresolved","Homology-based inference only"]},{"year":2007,"claim":"The demonstration that CNNM1 binds copper with nanomolar affinity and alters cellular copper retention established a specific biochemical activity — copper binding — independent of magnesium transport hypotheses.","evidence":"Immobilized metal affinity chromatography, isothermal titration calorimetry, cellular copper retention assay","pmids":["17608643"],"confidence":"Medium","gaps":["Physiological relevance of copper binding in vivo not shown","Relationship between copper binding and ion transport function unclear","Single lab, awaits independent replication"]},{"year":2009,"claim":"Identification of Cnnm1 as a transcriptional target of STAT3 and Nanog in embryonic stem cells, with knockdown causing increased differentiation, revealed an unexpected role in pluripotency maintenance distinct from ion transport.","evidence":"Hormone-dependent STAT3 system, microarray, siRNA knockdown, self-renewal and differentiation assays in mouse ES cells","pmids":["19544440"],"confidence":"Medium","gaps":["Downstream effector mechanism linking CNNM1 to self-renewal unknown","Whether ion transport or copper binding mediates the stem cell phenotype untested","Single lab"]},{"year":2016,"claim":"Extension of the stem cell role to spermatogonial stem cells showed that CNNM1 silencing shifts cells out of G1 into S/G2-M, establishing cell cycle regulation as a proximate mechanism for its role in stemness maintenance.","evidence":"siRNA knockdown, flow cytometry cell cycle analysis, immunofluorescence in mouse testis and GC1-spg cells","pmids":["27251091"],"confidence":"Medium","gaps":["Direct molecular targets controlling cell cycle progression not identified","In vivo SSC self-renewal phenotype not demonstrated","Whether the effect is cell-autonomous not confirmed"]},{"year":2021,"claim":"Purification of native TRPM7 complexes from brain revealed that CNNM1–4 and ARL15 are bona fide TRPM7-associated proteins, and reconstitution confirmed functional ternary complexes that modulate TRPM7 channel activity — establishing the major physiological partnership for CNNM family proteins.","evidence":"Multi-epitope affinity purification from rodent brain, quantitative mass spectrometry, heterologous reconstitution, electrophysiology","pmids":["34766907"],"confidence":"High","gaps":["Individual contribution of CNNM1 versus other CNNM paralogs to TRPM7 regulation not dissected","Structural basis of the complex unknown","In vivo physiological consequence of disrupting CNNM1–TRPM7 interaction not tested"]},{"year":2021,"claim":"Parallel work showed that ARL15 interacts with CNNM CBS domains, promotes CNNM N-glycosylation, and negatively regulates Mg²⁺ uptake, linking the CNNM–ARL15 axis to magnesium homeostasis in kidney cells.","evidence":"Co-immunoprecipitation, immunocytochemistry, ²⁵Mg²⁺ stable isotope uptake assay, siRNA knockdown in kidney cell lines","pmids":["34089346"],"confidence":"High","gaps":["Specific contribution of CNNM1 (versus CNNM2/3/4) to renal Mg²⁺ handling not isolated","Whether N-glycosylation is the sole mechanism of ARL15-mediated regulation unknown"]},{"year":2025,"claim":"Domain dissection resolved how CNNM engages TRPM7: the DUF21 transmembrane domain is sufficient for complex assembly, the CBS-pair modulates channel gating and is required for ARL15 inhibition, and the CNBH domain binds and activates the TRPM7 kinase — providing a multi-domain regulatory model.","evidence":"Co-immunoprecipitation of deletion constructs, electrophysiology, in vitro kinase assay","pmids":["40962059"],"confidence":"High","gaps":["Structural model of the CNNM–TRPM7 interface at atomic resolution not available","Whether CNNM1 and CNNM2 differ in their TRPM7 regulatory properties not tested","In vivo validation of domain-specific functions lacking"]},{"year":null,"claim":"Key unresolved questions include whether CNNM1's copper-binding and TRPM7-regulatory activities are functionally connected, the molecular mechanism by which CNNM1 controls cell cycle in stem cells, and CNNM1-specific (versus paralog-redundant) physiological roles in vivo.","evidence":"","pmids":[],"confidence":"Low","gaps":["No in vivo loss-of-function model (knockout mouse) reported for CNNM1","Relationship between copper binding, Mg²⁺ transport, and TRPM7 regulation unresolved","Molecular targets mediating cell cycle effects in stem cells unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,5,6]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,5]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[5]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[5]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[4,5,6]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[3,7]}],"complexes":["TRPM7-CNNM-ARL15 complex"],"partners":["TRPM7","ARL15"],"other_free_text":[]},"mechanistic_narrative":"CNNM1 is a transmembrane protein that functions at the intersection of divalent cation homeostasis and stem cell maintenance. It assembles into native high-molecular-weight complexes with the channel-kinase TRPM7 and the small GTPase ARL15 in brain tissue, where its DUF21 domain mediates TRPM7 binding, its CBS-pair domain modulates TRPM7 channel activity and transduces ARL15-dependent inhibition, and its CNBH domain contacts and enhances TRPM7 kinase activity [PMID:34766907, PMID:40962059]. CNNM1 binds copper with nanomolar affinity and modifies cellular copper retention, consistent with a cytoplasmic copper chaperone or storage function [PMID:17608643]. In embryonic stem cells and spermatogonial stem cells, CNNM1 is a transcriptional target of STAT3 and Nanog whose knockdown promotes differentiation and alters cell cycle progression, establishing it as a regulator of the undifferentiated state and self-renewal [PMID:19544440, PMID:27251091]."},"prefetch_data":{"uniprot":{"accession":"Q9NRU3","full_name":"Metal transporter CNNM1","aliases":["Ancient conserved domain-containing protein 1","Cyclin-M1"],"length_aa":951,"mass_kda":104.4,"function":"Probable metal transporter","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q9NRU3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CNNM1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CNNM1","total_profiled":1310},"omim":[{"mim_id":"607805","title":"CYCLIN M4; CNNM4","url":"https://www.omim.org/entry/607805"},{"mim_id":"607804","title":"CYCLIN M3; CNNM3","url":"https://www.omim.org/entry/607804"},{"mim_id":"607803","title":"CYCLIN M2; CNNM2","url":"https://www.omim.org/entry/607803"},{"mim_id":"607802","title":"CYCLIN M1; CNNM1","url":"https://www.omim.org/entry/607802"},{"mim_id":"236730","title":"UROFACIAL SYNDROME 1; UFS1","url":"https://www.omim.org/entry/236730"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":13.2},{"tissue":"testis","ntpm":9.8}],"url":"https://www.proteinatlas.org/search/CNNM1"},"hgnc":{"alias_symbol":["SLC70A1"],"prev_symbol":["ACDP1"]},"alphafold":{"accession":"Q9NRU3","domains":[{"cath_id":"2.60.40","chopping":"43-79_105-113_133-209","consensus_level":"high","plddt":70.4245,"start":43,"end":209},{"cath_id":"-","chopping":"223-308_324-391","consensus_level":"high","plddt":85.5942,"start":223,"end":391},{"cath_id":"3.10.580.10","chopping":"431-581","consensus_level":"high","plddt":88.5902,"start":431,"end":581},{"cath_id":"2.60.120.10","chopping":"597-707_763-797","consensus_level":"high","plddt":87.4689,"start":597,"end":797}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NRU3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NRU3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NRU3-F1-predicted_aligned_error_v6.png","plddt_mean":66.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CNNM1","jax_strain_url":"https://www.jax.org/strain/search?query=CNNM1"},"sequence":{"accession":"Q9NRU3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NRU3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NRU3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NRU3"}},"corpus_meta":[{"pmid":"19544440","id":"PMC_19544440","title":"Novel 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structural homology to bacterial CorC (Mg2+/Co2+ efflux protein) suggests a role in ion transport.\",\n      \"method\": \"Immunostaining of mouse hippocampus neurons; sequence homology analysis\",\n      \"journal\": \"BMC genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — localization by immunostaining without direct functional consequence demonstrated\",\n      \"pmids\": [\"14723793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"ACDP-1 (CNNM1) binds copper with high affinity (nanomolar), localizes to the cytoplasm, and modifies cellular copper retention when expressed in cells, consistent with a role as a copper chaperone or storage protein.\",\n      \"method\": \"Immobilized metal affinity chromatography, isothermal titration calorimetry, cellular copper retention assay, subcellular localization\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro binding assay with quantitative ITC plus cellular functional assay, single lab\",\n      \"pmids\": [\"17608643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CNNM1 is expressed in c-KIT- and OCT3/4-positive spermatogonial stem cells in mouse testis; silencing of Cnnm1 in GC1-spg cells reduces G1-phase cells and increases S and G2/M populations, and retinoic acid downregulates Cnnm1 expression, indicating a role in spermatogonial cell cycle regulation and stemness maintenance.\",\n      \"method\": \"Immunofluorescence, siRNA knockdown, flow cytometry cell cycle analysis, RT-PCR\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD with defined cell-cycle phenotype plus localization, single lab, multiple methods\",\n      \"pmids\": [\"27251091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Native TRPM7 channels in rodent brain form high-molecular-weight complexes containing CNNM1-4 and ARL15, as identified by multi-epitope affinity purification and quantitative mass spectrometry; heterologous reconstitution confirmed TRPM7/CNNM/ARL15 ternary complex formation, which specifically impacts TRPM7 activity.\",\n      \"method\": \"Multi-epitope affinity purification, high-resolution quantitative mass spectrometry, heterologous reconstitution, electrophysiology\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — native complex purification from brain + MS + reconstitution + functional activity measurement\",\n      \"pmids\": [\"34766907\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ARL15 interacts with CNNM family proteins (including CNNM1) at their C-terminal CBS domains, promotes complex N-glycosylation of CNNMs, co-localizes with CNNM2 in endoplasmic reticulum, Golgi apparatus, and plasma membrane of kidney cells, and ARL15 knockdown increases Mg2+ uptake—establishing ARL15 as a negative regulator of Mg2+ transport via CNNM N-glycosylation.\",\n      \"method\": \"Co-immunoprecipitation, in silico modeling, immunocytochemistry, stable isotope 25Mg2+ uptake assay, siRNA knockdown\",\n      \"journal\": \"Cellular and molecular life sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal biochemical interaction, functional isotope uptake assay, subcellular co-localization, multiple cell lines\",\n      \"pmids\": [\"34089346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The CNNM transmembrane (DUF21) domain is sufficient to mediate assembly of the CNNM2-TRPM7 complex, while the CBS-pair and CNBH domains provide additional contact points; the CBS-pair domain modulates TRPM7 channel activity and is required for ARL15-mediated inhibition of TRPM7; the CNBH domain binds the TRPM7 kinase domain and modestly enhances its catalytic activity in vitro.\",\n      \"method\": \"Co-immunoprecipitation of deletion constructs, electrophysiology, in vitro kinase assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — domain dissection with multiple interaction assays, electrophysiology, and in vitro kinase assay in one study\",\n      \"pmids\": [\"40962059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Cnnm1 is a downstream transcriptional target of both STAT3 and Nanog in mouse embryonic stem cells; knockdown increases differentiation markers and frequency of differentiated colonies, indicating a role in maintenance of the undifferentiated state.\",\n      \"method\": \"Hormone-dependent STAT3 system, microarray, siRNA knockdown, self-renewal assay, differentiation marker analysis\",\n      \"journal\": \"Stem cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional knockdown with defined phenotype, transcriptional target validated, single lab\",\n      \"pmids\": [\"19544440\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Overexpression of CNNM1 in C18-4 spermatogonial cells upregulates genes involved in cell proliferation, nucleic acid metabolism, and cell cycle regulation; CNNM1 knockdown alters cell cycle progression, supporting a role in SSC self-renewal and survival.\",\n      \"method\": \"Overexpression, siRNA knockdown, proteome profiling, cell cycle analysis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — preprint, single lab, functional assays without reconstitution or epistasis\",\n      \"pmids\": [\"bio_10.1101_2025.10.20.683346\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"CNNM1 is a transmembrane protein that forms high-molecular-weight complexes with the ion channel-kinase TRPM7 (through its DUF21, CBS-pair, and CNBH domains) and with ARL15 in native brain and kidney tissues, where it regulates TRPM7 channel and kinase activities; in the cytoplasm, CNNM1 acts as a high-affinity copper-binding protein (chaperone/storage), and in the nucleus/stem-cell context it is a STAT3 and Nanog transcriptional target that sustains spermatogonial stem cell self-renewal and pluripotent cell maintenance by controlling cell cycle progression.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CNNM1 is a transmembrane protein that functions at the intersection of divalent cation homeostasis and stem cell maintenance. It assembles into native high-molecular-weight complexes with the channel-kinase TRPM7 and the small GTPase ARL15 in brain tissue, where its DUF21 domain mediates TRPM7 binding, its CBS-pair domain modulates TRPM7 channel activity and transduces ARL15-dependent inhibition, and its CNBH domain contacts and enhances TRPM7 kinase activity [PMID:34766907, PMID:40962059]. CNNM1 binds copper with nanomolar affinity and modifies cellular copper retention, consistent with a cytoplasmic copper chaperone or storage function [PMID:17608643]. In embryonic stem cells and spermatogonial stem cells, CNNM1 is a transcriptional target of STAT3 and Nanog whose knockdown promotes differentiation and alters cell cycle progression, establishing it as a regulator of the undifferentiated state and self-renewal [PMID:19544440, PMID:27251091].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Initial localization studies placed CNNM1 in the nucleus of HeLa cells, raising questions about whether this protein functions as a nuclear factor rather than a membrane transporter.\",\n      \"evidence\": \"Immunofluorescence in permeabilized HeLa cells\",\n      \"pmids\": [\"12657465\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Single cell line; no orthogonal biochemical fractionation\",\n        \"Nuclear function not tested\",\n        \"Antibody specificity not rigorously validated\"\n      ]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"In contrast, localization in native neurons placed CNNM1 at the plasma membrane and sequence homology to bacterial CorC suggested an ion transport function, reframing the protein as a potential divalent cation transporter.\",\n      \"evidence\": \"Immunostaining of mouse hippocampal neurons; bioinformatic analysis\",\n      \"pmids\": [\"14723793\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No direct ion transport activity demonstrated\",\n        \"Conflicting localization with prior HeLa study unresolved\",\n        \"Homology-based inference only\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"The demonstration that CNNM1 binds copper with nanomolar affinity and alters cellular copper retention established a specific biochemical activity — copper binding — independent of magnesium transport hypotheses.\",\n      \"evidence\": \"Immobilized metal affinity chromatography, isothermal titration calorimetry, cellular copper retention assay\",\n      \"pmids\": [\"17608643\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Physiological relevance of copper binding in vivo not shown\",\n        \"Relationship between copper binding and ion transport function unclear\",\n        \"Single lab, awaits independent replication\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identification of Cnnm1 as a transcriptional target of STAT3 and Nanog in embryonic stem cells, with knockdown causing increased differentiation, revealed an unexpected role in pluripotency maintenance distinct from ion transport.\",\n      \"evidence\": \"Hormone-dependent STAT3 system, microarray, siRNA knockdown, self-renewal and differentiation assays in mouse ES cells\",\n      \"pmids\": [\"19544440\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Downstream effector mechanism linking CNNM1 to self-renewal unknown\",\n        \"Whether ion transport or copper binding mediates the stem cell phenotype untested\",\n        \"Single lab\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extension of the stem cell role to spermatogonial stem cells showed that CNNM1 silencing shifts cells out of G1 into S/G2-M, establishing cell cycle regulation as a proximate mechanism for its role in stemness maintenance.\",\n      \"evidence\": \"siRNA knockdown, flow cytometry cell cycle analysis, immunofluorescence in mouse testis and GC1-spg cells\",\n      \"pmids\": [\"27251091\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct molecular targets controlling cell cycle progression not identified\",\n        \"In vivo SSC self-renewal phenotype not demonstrated\",\n        \"Whether the effect is cell-autonomous not confirmed\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Purification of native TRPM7 complexes from brain revealed that CNNM1–4 and ARL15 are bona fide TRPM7-associated proteins, and reconstitution confirmed functional ternary complexes that modulate TRPM7 channel activity — establishing the major physiological partnership for CNNM family proteins.\",\n      \"evidence\": \"Multi-epitope affinity purification from rodent brain, quantitative mass spectrometry, heterologous reconstitution, electrophysiology\",\n      \"pmids\": [\"34766907\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Individual contribution of CNNM1 versus other CNNM paralogs to TRPM7 regulation not dissected\",\n        \"Structural basis of the complex unknown\",\n        \"In vivo physiological consequence of disrupting CNNM1–TRPM7 interaction not tested\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Parallel work showed that ARL15 interacts with CNNM CBS domains, promotes CNNM N-glycosylation, and negatively regulates Mg²⁺ uptake, linking the CNNM–ARL15 axis to magnesium homeostasis in kidney cells.\",\n      \"evidence\": \"Co-immunoprecipitation, immunocytochemistry, ²⁵Mg²⁺ stable isotope uptake assay, siRNA knockdown in kidney cell lines\",\n      \"pmids\": [\"34089346\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Specific contribution of CNNM1 (versus CNNM2/3/4) to renal Mg²⁺ handling not isolated\",\n        \"Whether N-glycosylation is the sole mechanism of ARL15-mediated regulation unknown\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Domain dissection resolved how CNNM engages TRPM7: the DUF21 transmembrane domain is sufficient for complex assembly, the CBS-pair modulates channel gating and is required for ARL15 inhibition, and the CNBH domain binds and activates the TRPM7 kinase — providing a multi-domain regulatory model.\",\n      \"evidence\": \"Co-immunoprecipitation of deletion constructs, electrophysiology, in vitro kinase assay\",\n      \"pmids\": [\"40962059\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural model of the CNNM–TRPM7 interface at atomic resolution not available\",\n        \"Whether CNNM1 and CNNM2 differ in their TRPM7 regulatory properties not tested\",\n        \"In vivo validation of domain-specific functions lacking\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include whether CNNM1's copper-binding and TRPM7-regulatory activities are functionally connected, the molecular mechanism by which CNNM1 controls cell cycle in stem cells, and CNNM1-specific (versus paralog-redundant) physiological roles in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No in vivo loss-of-function model (knockout mouse) reported for CNNM1\",\n        \"Relationship between copper binding, Mg²⁺ transport, and TRPM7 regulation unresolved\",\n        \"Molecular targets mediating cell cycle effects in stem cells unidentified\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 5, 6]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [4, 5, 6]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [3, 7]}\n    ],\n    \"complexes\": [\n      \"TRPM7-CNNM-ARL15 complex\"\n    ],\n    \"partners\": [\n      \"TRPM7\",\n      \"ARL15\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}