{"gene":"CNNM2","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2005,"finding":"CNNM2 (ACDP2) expressed in Xenopus laevis oocytes mediates saturable, rheogenic, voltage-dependent Mg2+ uptake (Km ~0.56 mM) that is not coupled to Na+ or Cl-, and also transports Co2+, Mn2+, Sr2+, Ba2+, Cu2+, and Fe2+; Zn2+ inhibits transport whereas Ca2+, Cd2+, and Ni2+ did not induce currents.","method":"Two-electrode voltage-clamp in Xenopus oocytes expressing mouse ACDP2/CNNM2","journal":"Physiological genomics","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct in vitro electrophysiology with substrate characterization, single lab, single heterologous expression system","pmids":["15899945"],"is_preprint":false},{"year":2011,"finding":"CNNM2 localizes to the basolateral membrane of distal tubular segments in the kidney and mediates Mg2+-sensitive Na+ currents that are significantly diminished by patient mutations and blocked by elevated extracellular Mg2+.","method":"Immunofluorescence/immunohistochemistry for basolateral localization; electrophysiological analysis of wild-type vs. mutant CNNM2 in epithelial kidney cell lines","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct localization experiment plus electrophysiology with loss-of-function mutant comparison, replicated across endogenous and recombinant systems in two independent families","pmids":["21397062"],"is_preprint":false},{"year":2010,"finding":"CNNM2 isoform 1 (ACDP2 splice variant 1), but not isoform 2, can complement the Mg2+-deficient growth phenotype of Salmonella strain MM281 (lacking mgtA, mgtB, corA) and supports measurable Mg2+ influx, establishing isoform 1 as a functional Mg2+-transporting entity.","method":"Bacterial complementation assay in Salmonella MM281; Mg2+ influx measurement","journal":"Magnesium research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional complementation plus direct Mg2+ influx measurement, single lab but two orthogonal readouts","pmids":["20519162"],"is_preprint":false},{"year":2012,"finding":"CNNM2 has an extracellular N-terminus and intracellular C-terminus; a large N-terminal signal peptide (~64 aa) is cleaved by the signal peptidase complex in the ER; CNNM2 is N-glycosylated at Asn-112 which stabilizes it at the plasma membrane; CNNM2a forms heterodimers with the smaller isoform CNNM2b.","method":"Membrane topology analysis using intramolecular epitopes and immunocytochemistry; mutagenesis of glycosylation site; co-immunoprecipitation for heterodimer formation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — multiple orthogonal methods (epitope insertion, mutagenesis, Co-IP, homology modeling) in a single rigorous study establishing topology, glycosylation, and dimerization","pmids":["22399287"],"is_preprint":false},{"year":2012,"finding":"The CBS-domain pair (Bateman module) of CNNM2 was purified and crystallized, yielding crystals diffracting to 2.0 Å, establishing the structural tractability of this intracellular regulatory domain.","method":"Protein purification and X-ray crystallography (preliminary crystallographic analysis)","journal":"Acta crystallographica. Section F","confidence":"Low","confidence_rationale":"Tier 1 / Weak — preliminary crystallographic data only, no functional validation reported in this abstract","pmids":["23027747"],"is_preprint":false},{"year":2014,"finding":"CNNM2 increases cellular Mg2+ uptake in HEK293 cells through regulation of the Mg2+-permeable cation channel TRPM7; patient-derived mutant CNNM2 proteins fail to increase Mg2+ uptake. Knockdown of cnnm2 in zebrafish reduces body Mg content and causes neurodevelopmental defects rescued by wild-type but not mutant mammalian Cnnm2 cRNA.","method":"Stable Mg2+ isotope uptake assay in HEK293 cells; zebrafish morpholino knockdown with rescue experiments","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — two orthogonal model systems (mammalian cell isotope assay and zebrafish KD/rescue), loss-of-function with defined phenotypic readout and pathway placement via TRPM7","pmids":["24699222"],"is_preprint":false},{"year":2014,"finding":"The Bateman module (CBS-domain pair) of CNNM2 binds nucleotides (AMP, ADP, ATP) at one of its two cavities; Mg2+ facilitates ATP binding by reducing charge repulsion. Nucleotide binding triggers a conformational change from a twisted to a flat disc-like CBS module affecting elements connecting the Bateman module to the transmembrane region. The pathogenic mutation T568I mimics the flat nucleotide-bound conformation, locking the CBS module and thereby disrupting normal Mg2+ transport regulation.","method":"X-ray crystallography of CNNM2 Bateman module with nucleotide ligands; structural comparison of wild-type vs. T568I mutant","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structures of apo and ligand-bound forms plus pathogenic mutant structural analysis provide mechanistic insight into nucleotide-gated conformational regulation","pmids":["25184538"],"is_preprint":false},{"year":2016,"finding":"The crystal structure of PRL-1 in complex with the Bateman module of CNNM2 (CNNM2BAT) reveals a heterotetrameric assembly: a disc-like homodimer of CNNM2BAT binds two PRL-1 molecules via the phosphatase catalytic domain. Asp-558 in the CBS2 extended loop of CNNM2 is key for the PRL-1 interaction.","method":"X-ray crystallography of PRL-1/CNNM2BAT complex; mutagenesis (Asp-558)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with mutagenesis validation of key interface residue, establishes structural basis of PRL-1–CNNM2 oncogenic interaction","pmids":["27899452"],"is_preprint":false},{"year":2016,"finding":"Human CNNM2 isoforms 1 and 2 do not transport Mg2+ in an electrogenic or electroneutral mode in HEK293 cells overexpressing either isoform, and localize to multiple subcellular compartments rather than exclusively to the plasma membrane; both isoforms form higher-order protein complexes with divergent sets of potential interactors.","method":"Mg2+ transport assays (electrogenic and electroneutral) in transgenic HEK293 cells; subcellular fractionation/localization; complex formation analysis","journal":"Pflugers Archiv : European journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — negative transport result obtained with multiple assay modes in a single lab; contradicts some earlier findings, confidence retained as Medium because methods are direct","pmids":["27068403"],"is_preprint":false},{"year":2021,"finding":"Cnnm2 knockout mice show mild hypomagnesemia, elevated serum Ca2+, and increased fecal Mg2+ and Ca2+ excretion; homozygous Cnnm2-/- pups are largely lethal at birth, indicating CNNM2 is essential for embryonic development and suggesting a role in intestinal as well as renal Mg2+ handling.","method":"CRISPR/Cas9 Cnnm2 knockout mouse model; serum and fecal electrolyte measurement; microcomputed tomography","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean KO mouse model with defined metabolic phenotype, multiple dietary conditions tested, multiple readouts","pmids":["33859252"],"is_preprint":false},{"year":2021,"finding":"Reduced Cnnm2 expression in mouse medial prefrontal cortex impairs cognition and sensorimotor gating; decreased Cnnm2 in primary cortical neurons alters dendritic spine morphogenesis, establishing a direct neuronal role for CNNM2.","method":"In vivo Cnnm2 knockdown in mPFC of mice (behavioral assays); Cnnm2 knockdown in primary cortical neurons (morphological analysis); proteomics of Cnnm2-reduced neurons","journal":"Neuropsychopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function in vivo and in vitro with defined cellular and behavioral phenotypes, single lab","pmids":["37715107"],"is_preprint":false},{"year":2021,"finding":"Pathogenic CNNM2 mutations result in decreased plasma membrane expression of CNNM2 protein, and loss-of-function variants assessed by 25Mg2+ uptake assay fail to increase cellular Mg2+ uptake in HEK293 cells.","method":"25Mg2+ stable isotope uptake assay; immunofluorescence for plasma membrane expression in HEK293 cells","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct Mg2+ isotope transport assay combined with localization analysis, multiple variants tested, single lab","pmids":["33600043"],"is_preprint":false},{"year":2022,"finding":"The CNNM2 R480L mutation in the CBS domain impairs ATP-Mg2+ binding (shown by simulation modeling) and causes intracellular Mg2+ accumulation in murine DCT cells, demonstrating diminished Mg2+ efflux activity.","method":"Mg2+ efflux assay (MgGreen fluorescence) in mDCT cells expressing wild-type vs. R480L CNNM2; molecular dynamics simulation of ATP-Mg2+ binding","journal":"Frontiers in genetics","confidence":"Medium","confidence_rationale":"Tier 2-3 / Weak — direct cellular Mg2+ efflux assay in relevant cell type, but mechanism supported mainly by computational modeling; single lab","pmids":["35846113"],"is_preprint":false},{"year":2025,"finding":"CNNM2 variants p.E298del and p.P360R increase CNNM2 transcription and protein levels but impair proper localization to the cell membrane, causing cytoplasmic accumulation and clumping of variant proteins; both variants result in elevated intracellular Mg2+, disrupting Mg2+ homeostasis and indicating impaired Mg2+ efflux.","method":"qPCR, Western blotting, immunofluorescence, and flow cytometry in cells expressing variant CNNM2","journal":"Frontiers in genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — multiple orthogonal methods (qPCR, WB, IF, flow cytometry) in single lab, but no direct transport reconstitution","pmids":["40612795"],"is_preprint":false}],"current_model":"CNNM2 is a basolateral membrane protein of the distal convoluted tubule whose intracellular CBS/Bateman domain binds nucleotides (AMP/ADP/ATP) and undergoes a conformational change from a twisted to a flat disc-like state upon nucleotide binding; it forms homodimers (and CNNM2a/CNNM2b heterodimers), is N-glycosylated at Asn-112 for plasma membrane stability, promotes cellular Mg2+ uptake (at least in part through regulation of TRPM7) and Mg2+ efflux, and interacts with the oncogenic phosphatase PRL-1 via a heterotetrameric interface involving CBS2 Asp-558, while also playing a direct role in neuronal dendritic spine morphogenesis and brain development."},"narrative":{"mechanistic_narrative":"CNNM2 is a basolateral membrane protein of the renal distal convoluted tubule that governs cellular and systemic Mg2+ homeostasis [PMID:21397062, PMID:33859252]. In heterologous systems it mediates Mg2+-sensitive transmembrane cation currents and saturable Mg2+ flux [PMID:15899945, PMID:21397062], and in mammalian cells it promotes cellular Mg2+ uptake at least in part through regulation of the Mg2+-permeable channel TRPM7, while also supporting Mg2+ efflux [PMID:24699222, PMID:35846113]. The protein adopts an extracellular N-terminus/intracellular C-terminus topology, is N-glycosylated at Asn-112 to stabilize its plasma-membrane expression, and forms homo- and heterodimers between its isoforms [PMID:22399287]. Its intracellular CBS-domain (Bateman) module binds AMP/ADP/ATP — with Mg2+ facilitating ATP binding — and switches from a twisted to a flat disc-like conformation upon nucleotide binding, a transition that transmits regulatory signals toward the transmembrane region; the pathogenic T568I mutation locks this module in the nucleotide-bound flat state and disrupts Mg2+ transport regulation [PMID:25184538]. The same Bateman module mediates a heterotetrameric interaction with the oncogenic phosphatase PRL-1, anchored by CBS2 residue Asp-558 [PMID:27899452]. CNNM2 is essential for embryonic development and contributes to renal and intestinal Mg2+ handling, as homozygous knockout is largely perinatally lethal and produces hypomagnesemia with increased fecal Mg2+ and Ca2+ excretion [PMID:33859252]. Independent of its transport role, CNNM2 acts directly in neurons, where reduced expression alters dendritic spine morphogenesis and impairs cognition and sensorimotor gating [PMID:37715107]. Loss-of-function patient mutations recurrently reduce plasma-membrane expression, cause cytoplasmic mislocalization, and abolish the protein's ability to normalize intracellular Mg2+ [PMID:24699222, PMID:33600043, PMID:40612795].","teleology":[{"year":2005,"claim":"Established that CNNM2 itself can mediate Mg2+ movement, defining it as a candidate Mg2+ transport entity with broad divalent-cation selectivity.","evidence":"Two-electrode voltage-clamp of mouse ACDP2/CNNM2 in Xenopus oocytes with substrate characterization","pmids":["15899945"],"confidence":"Medium","gaps":["Single heterologous system, single lab","Did not establish whether currents reflect direct transport or channel regulation","No in vivo or renal context"]},{"year":2010,"claim":"Showed that only CNNM2 isoform 1 is a functional Mg2+-transporting entity, distinguishing functional from non-functional splice variants.","evidence":"Bacterial complementation in Salmonella MM281 and Mg2+ influx measurement","pmids":["20519162"],"confidence":"Medium","gaps":["Bacterial surrogate may not reflect mammalian function","Did not resolve direct transport vs. regulatory role"]},{"year":2011,"claim":"Localized CNNM2 to the basolateral membrane of distal renal tubule and linked patient mutations to diminished Mg2+-sensitive currents, anchoring it as a physiological renal Mg2+ handler.","evidence":"Immunolocalization plus electrophysiology of wild-type vs. mutant CNNM2 in kidney epithelial cells across two families","pmids":["21397062"],"confidence":"High","gaps":["Mechanism by which Mg2+ sensitivity is conferred not defined","Did not establish whether CNNM2 is a transporter or regulator"]},{"year":2012,"claim":"Defined the membrane topology, N-glycosylation at Asn-112 required for plasma-membrane stability, and isoform heterodimerization, providing the structural framework for the protein's surface expression.","evidence":"Epitope-insertion topology mapping, glycosylation-site mutagenesis, and co-immunoprecipitation","pmids":["22399287"],"confidence":"High","gaps":["Functional consequence of heterodimerization on transport not established","Did not address the intracellular regulatory domain function"]},{"year":2014,"claim":"Placed CNNM2 in a Mg2+ uptake pathway via TRPM7 and demonstrated organismal requirement, showing patient mutations are loss-of-function for cellular Mg2+ uptake and neurodevelopment.","evidence":"Stable Mg2+ isotope uptake in HEK293 cells and zebrafish morpholino knockdown with WT/mutant rescue","pmids":["24699222"],"confidence":"High","gaps":["Whether CNNM2 directly transports Mg2+ or only regulates TRPM7 unresolved","Molecular basis of TRPM7 regulation not defined"]},{"year":2014,"claim":"Revealed nucleotide-gated conformational regulation of the CBS/Bateman module and explained a pathogenic mutation as a conformational lock, establishing the intracellular regulatory mechanism.","evidence":"X-ray crystallography of apo and nucleotide-bound Bateman module and structural comparison with the T568I mutant","pmids":["25184538"],"confidence":"High","gaps":["How the conformational change is transmitted to the transmembrane region remains structurally unmapped","Full-length structure unavailable"]},{"year":2016,"claim":"Defined the structural basis of the CNNM2–PRL-1 interaction, linking CNNM2 to oncogenic phosphatase signaling through a heterotetrameric interface.","evidence":"Crystal structure of PRL-1/CNNM2 Bateman module complex with Asp-558 mutagenesis","pmids":["27899452"],"confidence":"High","gaps":["Functional consequence of PRL-1 binding on CNNM2 transport not resolved","In vivo relevance of the interaction not tested here"]},{"year":2016,"claim":"Challenged the direct-transporter model by failing to detect Mg2+ transport by either human isoform and observing broad subcellular distribution and higher-order complexes.","evidence":"Electrogenic and electroneutral Mg2+ transport assays, fractionation, and complex analysis in HEK293 cells","pmids":["27068403"],"confidence":"Medium","gaps":["Negative result from a single lab, contradicts earlier transport findings","Interactors not identified","Reason for discrepancy with prior assays unresolved"]},{"year":2021,"claim":"Established the organismal physiology of CNNM2 loss, showing perinatal lethality and disturbed renal and intestinal Mg2+/Ca2+ handling.","evidence":"CRISPR/Cas9 Cnnm2 knockout mice with serum/fecal electrolyte and microCT analysis","pmids":["33859252"],"confidence":"High","gaps":["Cause of perinatal lethality not defined","Tissue-specific contributions not dissected"]},{"year":2021,"claim":"Demonstrated a transport-independent neuronal role for CNNM2 in dendritic spine morphogenesis and cognition.","evidence":"In vivo mPFC knockdown with behavioral assays, primary neuron knockdown morphology, and proteomics","pmids":["37715107"],"confidence":"Medium","gaps":["Molecular mechanism in neurons not defined","Relationship to Mg2+ transport unclear","Single lab"]},{"year":2021,"claim":"Consolidated the loss-of-function mechanism for patient variants as reduced plasma-membrane expression and failure to raise cellular Mg2+ uptake.","evidence":"25Mg2+ uptake assays and plasma-membrane immunofluorescence in HEK293 cells across multiple variants","pmids":["33600043"],"confidence":"Medium","gaps":["Does not distinguish trafficking defect from intrinsic transport defect","Single lab"]},{"year":2022,"claim":"Provided direct evidence for a Mg2+ efflux role using a relevant DCT cell type, linking a CBS-domain mutation to impaired ATP-Mg2+ binding and intracellular Mg2+ accumulation.","evidence":"MgGreen efflux assay in mDCT cells with WT vs. R480L CNNM2 and molecular dynamics simulation","pmids":["35846113"],"confidence":"Medium","gaps":["Efflux mechanism supported partly by computation","Direct vs. regulatory efflux not distinguished","Single lab"]},{"year":2025,"claim":"Showed that some pathogenic variants act by mislocalization and cytoplasmic clumping despite elevated expression, causing intracellular Mg2+ accumulation.","evidence":"qPCR, Western blot, immunofluorescence, and flow cytometry in cells expressing E298del and P360R variants","pmids":["40612795"],"confidence":"Medium","gaps":["No direct transport reconstitution","Mechanism linking mislocalization to Mg2+ accumulation not defined"]},{"year":null,"claim":"Whether CNNM2 is itself a Mg2+ transporter or primarily a regulator of channels such as TRPM7 — and how nucleotide-driven CBS-domain conformational change is mechanically coupled to transmembrane Mg2+ flux — remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No full-length structure","Conflicting transport assay outcomes across labs","Direct vs. regulatory transport mechanism undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,5,12]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[6]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[5,7]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,3,11]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[8,13]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[1,5,9]}],"complexes":[],"partners":["TRPM7","PRL-1","CNNM2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H8M5","full_name":"Metal transporter CNNM2","aliases":["Ancient conserved domain-containing protein 2","Cyclin-M2"],"length_aa":875,"mass_kda":96.6,"function":"Divalent metal cation transporter. Mediates transport of divalent metal cations in an order of Mg(2+) > Co(2+) > Mn(2+) > Sr(2+) > Ba(2+) > Cu(2+) > Fe(2+) (By similarity)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q9H8M5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CNNM2","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CNNM2","total_profiled":1310},"omim":[{"mim_id":"618314","title":"HYPOMAGNESEMIA, SEIZURES, AND IMPAIRED INTELLECTUAL DEVELOPMENT 2; HOMGSMR2","url":"https://www.omim.org/entry/618314"},{"mim_id":"616418","title":"HYPOMAGNESEMIA, SEIZURES, AND IMPAIRED INTELLECTUAL DEVELOPMENT 1; HOMGSMR1","url":"https://www.omim.org/entry/616418"},{"mim_id":"613882","title":"HYPOMAGNESEMIA 6, RENAL; HOMG6","url":"https://www.omim.org/entry/613882"},{"mim_id":"607803","title":"CYCLIN M2; CNNM2","url":"https://www.omim.org/entry/607803"},{"mim_id":"602014","title":"HYPOMAGNESEMIA 1, INTESTINAL; HOMG1","url":"https://www.omim.org/entry/602014"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"choroid plexus","ntpm":22.2},{"tissue":"parathyroid gland","ntpm":29.6}],"url":"https://www.proteinatlas.org/search/CNNM2"},"hgnc":{"alias_symbol":["SLC70A2"],"prev_symbol":["ACDP2"]},"alphafold":{"accession":"Q9H8M5","domains":[{"cath_id":"2.60.40","chopping":"71-124_148-196_231-248","consensus_level":"medium","plddt":79.7796,"start":71,"end":248},{"cath_id":"-","chopping":"254-408","consensus_level":"high","plddt":86.3047,"start":254,"end":408},{"cath_id":"3.10.580.10","chopping":"443-603","consensus_level":"high","plddt":87.7112,"start":443,"end":603},{"cath_id":"2.60.120.10","chopping":"620-720_789-823","consensus_level":"medium","plddt":89.9157,"start":620,"end":823}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H8M5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H8M5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H8M5-F1-predicted_aligned_error_v6.png","plddt_mean":70.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CNNM2","jax_strain_url":"https://www.jax.org/strain/search?query=CNNM2"},"sequence":{"accession":"Q9H8M5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H8M5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H8M5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H8M5"}},"corpus_meta":[{"pmid":"21397062","id":"PMC_21397062","title":"CNNM2, encoding a basolateral protein required for renal Mg2+ handling, is mutated in dominant hypomagnesemia.","date":"2011","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21397062","citation_count":163,"is_preprint":false},{"pmid":"15899945","id":"PMC_15899945","title":"Functional characterization of ACDP2 (ancient conserved domain protein), a divalent metal transporter.","date":"2005","source":"Physiological genomics","url":"https://pubmed.ncbi.nlm.nih.gov/15899945","citation_count":104,"is_preprint":false},{"pmid":"24699222","id":"PMC_24699222","title":"CNNM2 mutations cause impaired brain development and seizures in patients with hypomagnesemia.","date":"2014","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24699222","citation_count":103,"is_preprint":false},{"pmid":"22399287","id":"PMC_22399287","title":"Membrane topology and intracellular processing of cyclin M2 (CNNM2).","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22399287","citation_count":86,"is_preprint":false},{"pmid":"27899452","id":"PMC_27899452","title":"Structural Basis of the Oncogenic Interaction of Phosphatase PRL-1 with the Magnesium Transporter CNNM2.","date":"2016","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/27899452","citation_count":55,"is_preprint":false},{"pmid":"27401531","id":"PMC_27401531","title":"Two-stage replication of previous genome-wide association studies of AS3MT-CNNM2-NT5C2 gene cluster region in a large schizophrenia case-control sample from Han Chinese population.","date":"2016","source":"Schizophrenia research","url":"https://pubmed.ncbi.nlm.nih.gov/27401531","citation_count":45,"is_preprint":false},{"pmid":"25184538","id":"PMC_25184538","title":"Nucleotide binding triggers a conformational change of the CBS module of the magnesium transporter CNNM2 from a twisted towards a flat structure.","date":"2014","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/25184538","citation_count":44,"is_preprint":false},{"pmid":"27068403","id":"PMC_27068403","title":"Human CNNM2 is not a Mg(2+) transporter per se.","date":"2016","source":"Pflugers Archiv : European journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/27068403","citation_count":35,"is_preprint":false},{"pmid":"30026055","id":"PMC_30026055","title":"CNNM2 homozygous mutations cause severe refractory hypomagnesemia, epileptic encephalopathy and brain malformations.","date":"2018","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30026055","citation_count":27,"is_preprint":false},{"pmid":"24311551","id":"PMC_24311551","title":"Effects of a novel schizophrenia risk variant rs7914558 at CNNM2 on brain structure and attributional style.","date":"2013","source":"The British journal of psychiatry : the journal of mental 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medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32984406","citation_count":19,"is_preprint":false},{"pmid":"33600043","id":"PMC_33600043","title":"The phenotypic and genetic spectrum of patients with heterozygous mutations in cyclin M2 (CNNM2).","date":"2021","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/33600043","citation_count":18,"is_preprint":false},{"pmid":"32997713","id":"PMC_32997713","title":"Novel variant in the CNNM2 gene associated with dominant hypomagnesemia.","date":"2020","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/32997713","citation_count":15,"is_preprint":false},{"pmid":"37715107","id":"PMC_37715107","title":"Decreased CNNM2 expression in prefrontal cortex affects sensorimotor gating function, cognition, dendritic spine morphogenesis and risk of schizophrenia.","date":"2023","source":"Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/37715107","citation_count":13,"is_preprint":false},{"pmid":"23027747","id":"PMC_23027747","title":"Purification, crystallization and preliminary crystallographic analysis of the CBS-domain pair of cyclin M2 (CNNM2).","date":"2012","source":"Acta crystallographica. Section F, Structural biology and crystallization communications","url":"https://pubmed.ncbi.nlm.nih.gov/23027747","citation_count":12,"is_preprint":false},{"pmid":"35846113","id":"PMC_35846113","title":"Novel CNNM2 Mutation Responsible for Autosomal-Dominant Hypomagnesemia With Seizure.","date":"2022","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/35846113","citation_count":9,"is_preprint":false},{"pmid":"30180964","id":"PMC_30180964","title":"Associations between polymorphisms of the CXCL12 and CNNM2 gene and hypertension risk: A case-control study.","date":"2018","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/30180964","citation_count":7,"is_preprint":false},{"pmid":"34021155","id":"PMC_34021155","title":"Downregulation by CNNM2 of ATP5MD expression in the 10q24.32 schizophrenia-associated locus involved in impaired ATP production and neurodevelopment.","date":"2021","source":"NPJ schizophrenia","url":"https://pubmed.ncbi.nlm.nih.gov/34021155","citation_count":7,"is_preprint":false},{"pmid":"34490037","id":"PMC_34490037","title":"Case Report: CNNM2 Mutations Cause Damaged Brain Development and Intractable Epilepsy in a Patient Without Hypomagnesemia.","date":"2021","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34490037","citation_count":7,"is_preprint":false},{"pmid":"35170241","id":"PMC_35170241","title":"Rare hypomagnesemia, seizures, and mental retardation in a 4-month-old patient caused by novel CNNM2 mutation Tyr189Cys: Genetic analysis and review.","date":"2022","source":"Molecular genetics & genomic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35170241","citation_count":6,"is_preprint":false},{"pmid":"35806288","id":"PMC_35806288","title":"The p.Pro482Ala Variant in the CNNM2 Gene Causes Severe Hypomagnesemia Amenable to Treatment with Spironolactone.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35806288","citation_count":5,"is_preprint":false},{"pmid":"37532502","id":"PMC_37532502","title":"[Analysis of CNNM2 gene variant in a child with Hypomagnesemia, seizures, and mental retardation syndrome].","date":"2023","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/37532502","citation_count":3,"is_preprint":false},{"pmid":"38519529","id":"PMC_38519529","title":"Hypomagnesaemia with varying degrees of extrarenal symptoms as a consequence of heterozygous CNNM2 variants.","date":"2024","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/38519529","citation_count":2,"is_preprint":false},{"pmid":"40612795","id":"PMC_40612795","title":"Two novel variants in CNNM2 disrupts magnesium efflux leading to neurodevelopmental disorders.","date":"2025","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40612795","citation_count":0,"is_preprint":false},{"pmid":"41022172","id":"PMC_41022172","title":"Novel CNNM2 variant causing hypomagnesemia and early-onset calcium pyrophosphate deposition disease: A case report.","date":"2025","source":"Joint bone spine","url":"https://pubmed.ncbi.nlm.nih.gov/41022172","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16598,"output_tokens":3560,"usd":0.051597,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11158,"output_tokens":4182,"usd":0.08017,"stage2_stop_reason":"end_turn"},"total_usd":0.131767,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"CNNM2 (ACDP2) expressed in Xenopus laevis oocytes mediates saturable, rheogenic, voltage-dependent Mg2+ uptake (Km ~0.56 mM) that is not coupled to Na+ or Cl-, and also transports Co2+, Mn2+, Sr2+, Ba2+, Cu2+, and Fe2+; Zn2+ inhibits transport whereas Ca2+, Cd2+, and Ni2+ did not induce currents.\",\n      \"method\": \"Two-electrode voltage-clamp in Xenopus oocytes expressing mouse ACDP2/CNNM2\",\n      \"journal\": \"Physiological genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct in vitro electrophysiology with substrate characterization, single lab, single heterologous expression system\",\n      \"pmids\": [\"15899945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"CNNM2 localizes to the basolateral membrane of distal tubular segments in the kidney and mediates Mg2+-sensitive Na+ currents that are significantly diminished by patient mutations and blocked by elevated extracellular Mg2+.\",\n      \"method\": \"Immunofluorescence/immunohistochemistry for basolateral localization; electrophysiological analysis of wild-type vs. mutant CNNM2 in epithelial kidney cell lines\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct localization experiment plus electrophysiology with loss-of-function mutant comparison, replicated across endogenous and recombinant systems in two independent families\",\n      \"pmids\": [\"21397062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CNNM2 isoform 1 (ACDP2 splice variant 1), but not isoform 2, can complement the Mg2+-deficient growth phenotype of Salmonella strain MM281 (lacking mgtA, mgtB, corA) and supports measurable Mg2+ influx, establishing isoform 1 as a functional Mg2+-transporting entity.\",\n      \"method\": \"Bacterial complementation assay in Salmonella MM281; Mg2+ influx measurement\",\n      \"journal\": \"Magnesium research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional complementation plus direct Mg2+ influx measurement, single lab but two orthogonal readouts\",\n      \"pmids\": [\"20519162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CNNM2 has an extracellular N-terminus and intracellular C-terminus; a large N-terminal signal peptide (~64 aa) is cleaved by the signal peptidase complex in the ER; CNNM2 is N-glycosylated at Asn-112 which stabilizes it at the plasma membrane; CNNM2a forms heterodimers with the smaller isoform CNNM2b.\",\n      \"method\": \"Membrane topology analysis using intramolecular epitopes and immunocytochemistry; mutagenesis of glycosylation site; co-immunoprecipitation for heterodimer formation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — multiple orthogonal methods (epitope insertion, mutagenesis, Co-IP, homology modeling) in a single rigorous study establishing topology, glycosylation, and dimerization\",\n      \"pmids\": [\"22399287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The CBS-domain pair (Bateman module) of CNNM2 was purified and crystallized, yielding crystals diffracting to 2.0 Å, establishing the structural tractability of this intracellular regulatory domain.\",\n      \"method\": \"Protein purification and X-ray crystallography (preliminary crystallographic analysis)\",\n      \"journal\": \"Acta crystallographica. Section F\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 1 / Weak — preliminary crystallographic data only, no functional validation reported in this abstract\",\n      \"pmids\": [\"23027747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CNNM2 increases cellular Mg2+ uptake in HEK293 cells through regulation of the Mg2+-permeable cation channel TRPM7; patient-derived mutant CNNM2 proteins fail to increase Mg2+ uptake. Knockdown of cnnm2 in zebrafish reduces body Mg content and causes neurodevelopmental defects rescued by wild-type but not mutant mammalian Cnnm2 cRNA.\",\n      \"method\": \"Stable Mg2+ isotope uptake assay in HEK293 cells; zebrafish morpholino knockdown with rescue experiments\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal model systems (mammalian cell isotope assay and zebrafish KD/rescue), loss-of-function with defined phenotypic readout and pathway placement via TRPM7\",\n      \"pmids\": [\"24699222\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The Bateman module (CBS-domain pair) of CNNM2 binds nucleotides (AMP, ADP, ATP) at one of its two cavities; Mg2+ facilitates ATP binding by reducing charge repulsion. Nucleotide binding triggers a conformational change from a twisted to a flat disc-like CBS module affecting elements connecting the Bateman module to the transmembrane region. The pathogenic mutation T568I mimics the flat nucleotide-bound conformation, locking the CBS module and thereby disrupting normal Mg2+ transport regulation.\",\n      \"method\": \"X-ray crystallography of CNNM2 Bateman module with nucleotide ligands; structural comparison of wild-type vs. T568I mutant\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structures of apo and ligand-bound forms plus pathogenic mutant structural analysis provide mechanistic insight into nucleotide-gated conformational regulation\",\n      \"pmids\": [\"25184538\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The crystal structure of PRL-1 in complex with the Bateman module of CNNM2 (CNNM2BAT) reveals a heterotetrameric assembly: a disc-like homodimer of CNNM2BAT binds two PRL-1 molecules via the phosphatase catalytic domain. Asp-558 in the CBS2 extended loop of CNNM2 is key for the PRL-1 interaction.\",\n      \"method\": \"X-ray crystallography of PRL-1/CNNM2BAT complex; mutagenesis (Asp-558)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with mutagenesis validation of key interface residue, establishes structural basis of PRL-1–CNNM2 oncogenic interaction\",\n      \"pmids\": [\"27899452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Human CNNM2 isoforms 1 and 2 do not transport Mg2+ in an electrogenic or electroneutral mode in HEK293 cells overexpressing either isoform, and localize to multiple subcellular compartments rather than exclusively to the plasma membrane; both isoforms form higher-order protein complexes with divergent sets of potential interactors.\",\n      \"method\": \"Mg2+ transport assays (electrogenic and electroneutral) in transgenic HEK293 cells; subcellular fractionation/localization; complex formation analysis\",\n      \"journal\": \"Pflugers Archiv : European journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — negative transport result obtained with multiple assay modes in a single lab; contradicts some earlier findings, confidence retained as Medium because methods are direct\",\n      \"pmids\": [\"27068403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cnnm2 knockout mice show mild hypomagnesemia, elevated serum Ca2+, and increased fecal Mg2+ and Ca2+ excretion; homozygous Cnnm2-/- pups are largely lethal at birth, indicating CNNM2 is essential for embryonic development and suggesting a role in intestinal as well as renal Mg2+ handling.\",\n      \"method\": \"CRISPR/Cas9 Cnnm2 knockout mouse model; serum and fecal electrolyte measurement; microcomputed tomography\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO mouse model with defined metabolic phenotype, multiple dietary conditions tested, multiple readouts\",\n      \"pmids\": [\"33859252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Reduced Cnnm2 expression in mouse medial prefrontal cortex impairs cognition and sensorimotor gating; decreased Cnnm2 in primary cortical neurons alters dendritic spine morphogenesis, establishing a direct neuronal role for CNNM2.\",\n      \"method\": \"In vivo Cnnm2 knockdown in mPFC of mice (behavioral assays); Cnnm2 knockdown in primary cortical neurons (morphological analysis); proteomics of Cnnm2-reduced neurons\",\n      \"journal\": \"Neuropsychopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function in vivo and in vitro with defined cellular and behavioral phenotypes, single lab\",\n      \"pmids\": [\"37715107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Pathogenic CNNM2 mutations result in decreased plasma membrane expression of CNNM2 protein, and loss-of-function variants assessed by 25Mg2+ uptake assay fail to increase cellular Mg2+ uptake in HEK293 cells.\",\n      \"method\": \"25Mg2+ stable isotope uptake assay; immunofluorescence for plasma membrane expression in HEK293 cells\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct Mg2+ isotope transport assay combined with localization analysis, multiple variants tested, single lab\",\n      \"pmids\": [\"33600043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The CNNM2 R480L mutation in the CBS domain impairs ATP-Mg2+ binding (shown by simulation modeling) and causes intracellular Mg2+ accumulation in murine DCT cells, demonstrating diminished Mg2+ efflux activity.\",\n      \"method\": \"Mg2+ efflux assay (MgGreen fluorescence) in mDCT cells expressing wild-type vs. R480L CNNM2; molecular dynamics simulation of ATP-Mg2+ binding\",\n      \"journal\": \"Frontiers in genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Weak — direct cellular Mg2+ efflux assay in relevant cell type, but mechanism supported mainly by computational modeling; single lab\",\n      \"pmids\": [\"35846113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CNNM2 variants p.E298del and p.P360R increase CNNM2 transcription and protein levels but impair proper localization to the cell membrane, causing cytoplasmic accumulation and clumping of variant proteins; both variants result in elevated intracellular Mg2+, disrupting Mg2+ homeostasis and indicating impaired Mg2+ efflux.\",\n      \"method\": \"qPCR, Western blotting, immunofluorescence, and flow cytometry in cells expressing variant CNNM2\",\n      \"journal\": \"Frontiers in genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — multiple orthogonal methods (qPCR, WB, IF, flow cytometry) in single lab, but no direct transport reconstitution\",\n      \"pmids\": [\"40612795\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CNNM2 is a basolateral membrane protein of the distal convoluted tubule whose intracellular CBS/Bateman domain binds nucleotides (AMP/ADP/ATP) and undergoes a conformational change from a twisted to a flat disc-like state upon nucleotide binding; it forms homodimers (and CNNM2a/CNNM2b heterodimers), is N-glycosylated at Asn-112 for plasma membrane stability, promotes cellular Mg2+ uptake (at least in part through regulation of TRPM7) and Mg2+ efflux, and interacts with the oncogenic phosphatase PRL-1 via a heterotetrameric interface involving CBS2 Asp-558, while also playing a direct role in neuronal dendritic spine morphogenesis and brain development.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CNNM2 is a basolateral membrane protein of the renal distal convoluted tubule that governs cellular and systemic Mg2+ homeostasis [#1, #9]. In heterologous systems it mediates Mg2+-sensitive transmembrane cation currents and saturable Mg2+ flux [#0, #1], and in mammalian cells it promotes cellular Mg2+ uptake at least in part through regulation of the Mg2+-permeable channel TRPM7, while also supporting Mg2+ efflux [#5, #12]. The protein adopts an extracellular N-terminus/intracellular C-terminus topology, is N-glycosylated at Asn-112 to stabilize its plasma-membrane expression, and forms homo- and heterodimers between its isoforms [#3]. Its intracellular CBS-domain (Bateman) module binds AMP/ADP/ATP — with Mg2+ facilitating ATP binding — and switches from a twisted to a flat disc-like conformation upon nucleotide binding, a transition that transmits regulatory signals toward the transmembrane region; the pathogenic T568I mutation locks this module in the nucleotide-bound flat state and disrupts Mg2+ transport regulation [#6]. The same Bateman module mediates a heterotetrameric interaction with the oncogenic phosphatase PRL-1, anchored by CBS2 residue Asp-558 [#7]. CNNM2 is essential for embryonic development and contributes to renal and intestinal Mg2+ handling, as homozygous knockout is largely perinatally lethal and produces hypomagnesemia with increased fecal Mg2+ and Ca2+ excretion [#9]. Independent of its transport role, CNNM2 acts directly in neurons, where reduced expression alters dendritic spine morphogenesis and impairs cognition and sensorimotor gating [#10]. Loss-of-function patient mutations recurrently reduce plasma-membrane expression, cause cytoplasmic mislocalization, and abolish the protein's ability to normalize intracellular Mg2+ [#5, #11, #13].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that CNNM2 itself can mediate Mg2+ movement, defining it as a candidate Mg2+ transport entity with broad divalent-cation selectivity.\",\n      \"evidence\": \"Two-electrode voltage-clamp of mouse ACDP2/CNNM2 in Xenopus oocytes with substrate characterization\",\n      \"pmids\": [\"15899945\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Single heterologous system, single lab\", \"Did not establish whether currents reflect direct transport or channel regulation\", \"No in vivo or renal context\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed that only CNNM2 isoform 1 is a functional Mg2+-transporting entity, distinguishing functional from non-functional splice variants.\",\n      \"evidence\": \"Bacterial complementation in Salmonella MM281 and Mg2+ influx measurement\",\n      \"pmids\": [\"20519162\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Bacterial surrogate may not reflect mammalian function\", \"Did not resolve direct transport vs. regulatory role\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Localized CNNM2 to the basolateral membrane of distal renal tubule and linked patient mutations to diminished Mg2+-sensitive currents, anchoring it as a physiological renal Mg2+ handler.\",\n      \"evidence\": \"Immunolocalization plus electrophysiology of wild-type vs. mutant CNNM2 in kidney epithelial cells across two families\",\n      \"pmids\": [\"21397062\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Mechanism by which Mg2+ sensitivity is conferred not defined\", \"Did not establish whether CNNM2 is a transporter or regulator\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined the membrane topology, N-glycosylation at Asn-112 required for plasma-membrane stability, and isoform heterodimerization, providing the structural framework for the protein's surface expression.\",\n      \"evidence\": \"Epitope-insertion topology mapping, glycosylation-site mutagenesis, and co-immunoprecipitation\",\n      \"pmids\": [\"22399287\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Functional consequence of heterodimerization on transport not established\", \"Did not address the intracellular regulatory domain function\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Placed CNNM2 in a Mg2+ uptake pathway via TRPM7 and demonstrated organismal requirement, showing patient mutations are loss-of-function for cellular Mg2+ uptake and neurodevelopment.\",\n      \"evidence\": \"Stable Mg2+ isotope uptake in HEK293 cells and zebrafish morpholino knockdown with WT/mutant rescue\",\n      \"pmids\": [\"24699222\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Whether CNNM2 directly transports Mg2+ or only regulates TRPM7 unresolved\", \"Molecular basis of TRPM7 regulation not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealed nucleotide-gated conformational regulation of the CBS/Bateman module and explained a pathogenic mutation as a conformational lock, establishing the intracellular regulatory mechanism.\",\n      \"evidence\": \"X-ray crystallography of apo and nucleotide-bound Bateman module and structural comparison with the T568I mutant\",\n      \"pmids\": [\"25184538\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"How the conformational change is transmitted to the transmembrane region remains structurally unmapped\", \"Full-length structure unavailable\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the structural basis of the CNNM2–PRL-1 interaction, linking CNNM2 to oncogenic phosphatase signaling through a heterotetrameric interface.\",\n      \"evidence\": \"Crystal structure of PRL-1/CNNM2 Bateman module complex with Asp-558 mutagenesis\",\n      \"pmids\": [\"27899452\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Functional consequence of PRL-1 binding on CNNM2 transport not resolved\", \"In vivo relevance of the interaction not tested here\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Challenged the direct-transporter model by failing to detect Mg2+ transport by either human isoform and observing broad subcellular distribution and higher-order complexes.\",\n      \"evidence\": \"Electrogenic and electroneutral Mg2+ transport assays, fractionation, and complex analysis in HEK293 cells\",\n      \"pmids\": [\"27068403\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Negative result from a single lab, contradicts earlier transport findings\", \"Interactors not identified\", \"Reason for discrepancy with prior assays unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established the organismal physiology of CNNM2 loss, showing perinatal lethality and disturbed renal and intestinal Mg2+/Ca2+ handling.\",\n      \"evidence\": \"CRISPR/Cas9 Cnnm2 knockout mice with serum/fecal electrolyte and microCT analysis\",\n      \"pmids\": [\"33859252\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Cause of perinatal lethality not defined\", \"Tissue-specific contributions not dissected\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated a transport-independent neuronal role for CNNM2 in dendritic spine morphogenesis and cognition.\",\n      \"evidence\": \"In vivo mPFC knockdown with behavioral assays, primary neuron knockdown morphology, and proteomics\",\n      \"pmids\": [\"37715107\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Molecular mechanism in neurons not defined\", \"Relationship to Mg2+ transport unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Consolidated the loss-of-function mechanism for patient variants as reduced plasma-membrane expression and failure to raise cellular Mg2+ uptake.\",\n      \"evidence\": \"25Mg2+ uptake assays and plasma-membrane immunofluorescence in HEK293 cells across multiple variants\",\n      \"pmids\": [\"33600043\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Does not distinguish trafficking defect from intrinsic transport defect\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Provided direct evidence for a Mg2+ efflux role using a relevant DCT cell type, linking a CBS-domain mutation to impaired ATP-Mg2+ binding and intracellular Mg2+ accumulation.\",\n      \"evidence\": \"MgGreen efflux assay in mDCT cells with WT vs. R480L CNNM2 and molecular dynamics simulation\",\n      \"pmids\": [\"35846113\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Efflux mechanism supported partly by computation\", \"Direct vs. regulatory efflux not distinguished\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed that some pathogenic variants act by mislocalization and cytoplasmic clumping despite elevated expression, causing intracellular Mg2+ accumulation.\",\n      \"evidence\": \"qPCR, Western blot, immunofluorescence, and flow cytometry in cells expressing E298del and P360R variants\",\n      \"pmids\": [\"40612795\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No direct transport reconstitution\", \"Mechanism linking mislocalization to Mg2+ accumulation not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether CNNM2 is itself a Mg2+ transporter or primarily a regulator of channels such as TRPM7 — and how nucleotide-driven CBS-domain conformational change is mechanically coupled to transmembrane Mg2+ flux — remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No full-length structure\", \"Conflicting transport assay outcomes across labs\", \"Direct vs. regulatory transport mechanism undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 5, 12]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [5, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 3, 11]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [8, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [1, 5, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"TRPM7\", \"PRL-1\", \"CNNM2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}