The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Warning: no contexts were retrieved, so this answer is not grounded in evidence but is instead a direct response from the agent model.
I apologize, but I encountered persistent technical issues with the evidence gathering system throughout this research session that prevented me from extracting citeable evidence from the full text of papers. While I successfully retrieved 45 relevant publications through literature searches and created a comprehensive summary table, the system requires citations from the gather_evidence tool to accept an answer.
Based on the UniProt annotation provided and the paper titles/abstracts retrieved, CNNM4 (A0A8I3PI07) in Canis lupus familiaris is a metal transporter belonging to the ACDP family with CBS domains. The mammalian literature consistently identifies CNNM4 as a magnesium transporter involved in epithelial magnesium homeostasis, with roles in intestinal absorption, enamel formation, and retinal function. The protein localizes to basolateral membranes and mediates magnesium efflux.
However, without functional evidence gathering citations, I cannot provide the comprehensive, well-cited research report requested. The technical limitations prevented completion of this task despite extensive literature retrieval efforts.
| Aspect | CNNM4 summary | Key details / examples | Sources |
|---|---|---|---|
| Gene/protein identity | CNNM4 is a conserved member of the CNNM/CorB (ACDP) family of divalent cation transport mediators | Matches the UniProt description for the dog ortholog: ACDP family protein with CBS-domain architecture and CNNM/CorB-type transmembrane transporter features; mammalian literature consistently treats CNNM4 as the CNNM4 magnesium transporter ortholog | Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983; Chen et al., 2021, https://doi.org/10.1038/s41467-021-24282-7; Franken et al., 2022, https://doi.org/10.1007/s00018-022-04442-8 |
| Protein structure / domains | Integral membrane protein with DUF21/CNNM transmembrane region and cytosolic CBS-pair (Bateman) domains; belongs to CorB/CNNM structural lineage | UniProt annotation lists ACDP/CNNM-related domains plus CBS domains; structural work on archaeal CorB, the prokaryotic homolog, supports a transmembrane Mg2+-handling module coupled to cytosolic CBS domains that sense Mg-ATP and regulate conformation | Chen et al., 2021, https://doi.org/10.1038/s41467-021-24282-7; Franken et al., 2022, https://doi.org/10.1007/s00018-022-04442-8 |
| Primary molecular function | Magnesium transport mediator, best supported as a Mg2+ efflux protein in epithelia | Mouse and cell studies identified CNNM4 as the basolateral Mg2+ extrusion system required for transcellular Mg2+ transport across epithelia; recent physiological reviews still describe CNNM4 as a likely/potential Na+/Mg2+ exchanger mediating Mg2+ efflux in colon | Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983; Kröse & de Baaij, 2024, https://doi.org/10.1093/ndt/gfae134 |
| Substrate specificity | Primary substrate is Mg2+ | CNNM4 is repeatedly discussed in the Mg2+ transport literature as a magnesium transporter; disease and knockout phenotypes are explained by altered magnesium handling rather than transport of another defined physiological substrate | Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983; Franken et al., 2022, https://doi.org/10.1007/s00018-022-04442-8; Kröse & de Baaij, 2024, https://doi.org/10.1093/ndt/gfae134 |
| Transport mechanism | Most direct epithelial evidence supports basolateral Mg2+ extrusion, likely coupled to extracellular Na+; broader CNNM mechanism remains actively debated | Yamazaki et al. reported imaging evidence that CNNM4 extrudes intracellular Mg2+ in exchange for extracellular Na+; later reviews note that CNNM proteins remain mechanistically debated, but structural/functional data from CorB homologs support direct Mg2+ transport capacity; CNNMs may also influence TRPM7-dependent divalent cation influx in parallel | Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983; Schäffers et al., 2018, https://doi.org/10.1152/ajprenal.00634.2017; Chen et al., 2021, https://doi.org/10.1038/s41467-021-24282-7; Bai et al., 2021, https://doi.org/10.1371/journal.pbio.3001496 |
| Subcellular localization | Basolateral plasma membrane of polarized epithelial cells | Strong localization in intestinal epithelia and ameloblasts at the basolateral membrane explains its role in exporting Mg2+ from epithelial cells toward blood/interstitium during transcellular transport | Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983 |
| Tissue expression / physiological sites | Best-established in intestine/colon and ameloblasts; less evidence for kidney than CNNM2 | CNNM4 is strongly expressed in intestinal epithelia and contributes to intestinal Mg absorption; knockout mice showed intestinal malabsorption and hypomagnesemia. CNNM4 is also present in ameloblasts, linking Mg homeostasis to enamel maturation. Reviews distinguish CNNM4 from CNNM2, which is more renal | Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983; Kröse & de Baaij, 2024, https://doi.org/10.1093/ndt/gfae134; de Baaij, 2023, https://doi.org/10.1152/ajprenal.00298.2022 |
| Biological role in organismal Mg homeostasis | Supports transcellular intestinal Mg absorption by mediating basolateral Mg exit from absorptive epithelia | Loss of CNNM4 causes hypomagnesemia in mice due to intestinal malabsorption; this places CNNM4 downstream of apical Mg entry pathways such as TRPM6/7 and upstream of Mg delivery to the internal milieu | Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983; Kröse & de Baaij, 2024, https://doi.org/10.1093/ndt/gfae134 |
| Regulation by cytosolic ligands / domains | CBS-pair domains act as regulatory modules that bind Mg-ATP and alter conformation | Structural and comparative studies indicate CNNM/CorB CBS domains are not passive motifs: they bind Mg-ATP and are linked to conformational changes relevant to transport regulation | Chen et al., 2021, https://doi.org/10.1038/s41467-021-24282-7; Bai et al., 2021, https://doi.org/10.1371/journal.pbio.3001496 |
| Protein interaction network | CNNM4 participates in the emerging PRL–CNNM–TRPM regulatory network | CNNM proteins bind phosphatases of regenerating liver (PRLs) through the CBS domains; PRL binding is widely interpreted as inhibiting CNNM Mg2+ efflux activity. CNNMs also interact with TRPM7 and can stimulate TRPM7-dependent divalent cation entry, indicating CNNM4 may coordinate efflux and influx arms of Mg homeostasis rather than acting in isolation | Bai et al., 2021, https://doi.org/10.1371/journal.pbio.3001496; Hardy et al., 2023, https://doi.org/10.1073/pnas.2221083120; Funato et al., 2024, https://doi.org/10.1038/s41598-024-76269-1; Jolly & Blackburn, 2025, https://doi.org/10.3390/ijms26041528 |
| Signaling pathways / downstream biology | Linked to TRPM7 signaling, cellular bioenergetics, adipocyte thermogenesis, macrophage polarization, and mTORC2 activation | In adipocytes, cold-induced ADRB3–PKA–CREB signaling upregulates CNNM4, promoting Mg secretion; extracellular Mg then promotes M2 macrophage polarization through mTORC2 signaling. More broadly, Mg homeostasis proteins including CNNMs intersect with PRL/TRPM7-dependent metabolic signaling | Hardy et al., 2023, https://doi.org/10.1073/pnas.2221083120; Zhang et al., 2024, https://doi.org/10.1002/advs.202401140; Jolly & Blackburn, 2025, https://doi.org/10.3390/ijms26041528 |
| Disease associations | Jalili syndrome; hypomagnesemia/intestinal malabsorption in experimental models; emerging links to cancer and metabolic disease | Human CNNM4 mutations cause Jalili syndrome, characterized by cone-rod dystrophy and amelogenesis imperfecta. In mice, Cnnm4 loss causes hypomagnesemia and enamel defects. Recent literature also implicates altered CNNM4 expression in obesity-related thermogenic dysfunction and in cancers such as cholangiocarcinoma | Parry et al., 2009, https://doi.org/10.1016/j.ajhg.2009.01.009; Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983; Prasov et al., 2020, https://doi.org/10.1002/ajmg.a.61484; Zhang et al., 2024, https://doi.org/10.1002/advs.202401140; Mercado-Gómez et al., 2026, https://doi.org/10.1136/gutjnl-2024-333255 |
| Phenotypic evidence from models | Knockout/deficiency phenotypes strongly support physiological relevance | Cnnm4-knockout mice develop hypomagnesemia due to impaired intestinal Mg absorption and show defective amelogenesis, while disease-associated missense variants abolish Mg extrusion activity in assays | Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983 |
| Recent developments (2023–2025) | Field has shifted from “is CNNM4 a transporter?” to “how does CNNM4 integrate transport with signaling and disease?” | 2023 renal Mg review frames CNNM-family function within unresolved basolateral Mg extrusion; 2024 magnesium biology review positions CNNM4 as a colon Na+/Mg2+ exchanger candidate; 2024 adipocyte study shows regulated Mg secretion with immune/metabolic consequences; 2024 PRL–CNNM screening paper highlights therapeutic targeting of the PRL–CNNM interaction; 2025 PACT review integrates PRL, ARL, CNNM, and TRPM proteins into a unified Mg homeostasis network | de Baaij, 2023, https://doi.org/10.1152/ajprenal.00298.2022; Kröse & de Baaij, 2024, https://doi.org/10.1093/ndt/gfae134; Zhang et al., 2024, https://doi.org/10.1002/advs.202401140; Funato et al., 2024, https://doi.org/10.1038/s41598-024-76269-1; Jolly & Blackburn, 2025, https://doi.org/10.3390/ijms26041528 |
| Relevance to dog CNNM4 (A0A8I3PI07) | Direct canine functional studies were not identified, so annotation is inferred from strong mammalian orthology | Because the dog protein carries the expected CNNM/ACDP and CBS-domain architecture and CNNM4 function is well conserved across mammals, the most defensible annotation is that canine CNNM4 is a basolateral Mg2+ transport mediator important for epithelial Mg handling, likely in intestine and enamel/retina-associated tissues | UniProt record provided by user; mammalian orthology supported by Yamazaki et al., 2013, https://doi.org/10.1371/journal.pgen.1003983; Franken et al., 2022, https://doi.org/10.1007/s00018-022-04442-8 |
Table: This table compiles the main structural, functional, localization, pathway, disease, and recent literature findings relevant to CNNM4. It is designed to support functional annotation of the canine CNNM4 ortholog by grounding inference in experimentally studied mammalian and family-level evidence.