{"gene":"CIDEA","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":1998,"finding":"CIDEA activates apoptosis in mammalian cells; its C-terminal region is necessary and sufficient for cell killing, while the N-terminal CIDE domain (homologous to DFF45) is required for DFF45-mediated inhibition of CIDEA-induced apoptosis. CIDEA-induced DNA fragmentation is inhibited by DFF45 but not by caspase inhibitors.","method":"Transfection of deletion mutants in 293T cells, DNA fragmentation assay, inhibition studies with DFF45 and caspase inhibitors","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 — domain mutagenesis with multiple functional readouts, replicated across constructs","pmids":["9564035"],"is_preprint":false},{"year":2003,"finding":"Cidea is expressed at high levels in brown adipose tissue mitochondria and directly suppresses UCP1 activity, thereby regulating thermogenesis and lipolysis; Cidea-null mice have increased metabolic rate, elevated BAT lipolysis, and resistance to diet-induced obesity and diabetes.","method":"Cidea knockout mouse model, metabolic rate measurements, cold challenge, direct suppression of UCP1 activity assay","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 — clean KO mouse with multiple orthogonal phenotypic readouts and direct UCP1 activity assay, highly cited foundational study","pmids":["12910269"],"is_preprint":false},{"year":2005,"finding":"In human adipocytes, CIDEA regulates lipolysis; RNAi-mediated depletion of CIDEA stimulates lipolysis and increases TNF-alpha secretion by a post-transcriptional mechanism. TNF-alpha in turn decreases CIDEA expression via the JNK (c-Jun N-terminal kinase) pathway.","method":"RNA interference in human adipocytes, lipolysis assay, TNF-alpha secretion measurement, pharmacological inhibition of JNK","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 — RNAi with defined cellular phenotype plus pathway placement via JNK inhibitor","pmids":["15919794"],"is_preprint":false},{"year":2007,"finding":"Cidea protein is regulated by ubiquitin-proteasome-mediated degradation; it is polyubiquitinated primarily at Lys23 in its N-terminal region, and mutation of N-terminal lysine residues (N-5KA mutant) greatly stabilizes the protein.","method":"Cycloheximide chase, proteasome inhibitor treatment, ubiquitination assay, site-directed mutagenesis of lysine residues in multiple cell lines and brown adipocytes","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro mutagenesis combined with biochemical ubiquitination assay across multiple cell systems","pmids":["17711404"],"is_preprint":false},{"year":2007,"finding":"Cidea gene expression in mouse liver is transcriptionally regulated by both PPARalpha and PPARgamma through a shared proximal PPRE element (Cidea-PPRE1 at -680/-668) in the Cidea promoter.","method":"Transactivation/luciferase reporter assays, gel-shift (EMSA), chromatin immunoprecipitation with PPARalpha and PPARgamma ligands","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — ChIP, EMSA, and reporter assays with orthogonal methods confirming functional PPRE","pmids":["17462989"],"is_preprint":false},{"year":2008,"finding":"Cidea colocalizes with lipid droplets (not mitochondria) in human and mouse adipocytes, co-localizing with perilipin; ectopic expression of Cidea-GFP greatly enhances lipid droplet size in preadipocytes and COS cells, and Cidea is regulated by PPARgamma.","method":"Fluorescence microscopy (GFP fusion protein), co-localization with perilipin, RNAi lipolysis assay, rosiglitazone treatment in mice","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — direct imaging with functional consequence (lipid droplet enlargement), multiple cell systems","pmids":["18509062"],"is_preprint":false},{"year":2008,"finding":"Cidea forms a complex with the beta subunit of AMPK (but not alpha or gamma subunits) in the endoplasmic reticulum, promoting ubiquitination-dependent proteasomal degradation of the AMPK-beta subunit, thereby reducing AMPK protein levels and enzymatic activity in brown adipose tissue.","method":"Co-immunoprecipitation in vivo, co-localization in ER, co-expression ubiquitination assay, AMPK activity measurement in Cidea-/- adipocytes","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 — reciprocal co-IP, ER co-localization, in-cell ubiquitination assay, KO rescue, multiple methods in one study","pmids":["18480843"],"is_preprint":false},{"year":2008,"finding":"RIP140 and PGC-1alpha regulate CIDEA expression in brown adipocytes: PGC-1alpha induces while RIP140 represses CIDEA promoter activity via estrogen-related receptor alpha (ERRalpha) and NRF-1 binding sites; RIP140 directly interacts with PGC-1alpha to suppress its coactivator activity.","method":"Luciferase reporter assays, promoter deletion analysis, protein-protein interaction assay (RIP140-PGC-1alpha), ectopic expression in brown adipocytes and nonadipogenic lines","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 — reporter assay with defined binding sites, direct protein interaction, and functional lipid droplet formation assay","pmids":["18794372"],"is_preprint":false},{"year":2008,"finding":"In apoptotic conditions, CIDEa redistributes from mitochondria to the nucleus in HeLa cells, and nuclear accumulation correlates with increased cell death.","method":"Immunocytochemistry and subcellular fractionation with tetracycline-inducible CIDEa expression, camptothecin/valinomycin treatment","journal":"General physiology and biophysics","confidence":"Medium","confidence_rationale":"Tier 2 — direct fractionation and imaging, but single lab and limited mechanistic follow-up","pmids":["18645223"],"is_preprint":false},{"year":2009,"finding":"Cold exposure down-regulates CIDEA mRNA and protein in rat interscapular BAT via sympathetically activated beta3-adrenoreceptors, and this effect is blocked by propranolol (non-selective beta-blocker) or SR59230A (selective beta3-antagonist).","method":"Cold exposure in vivo, pharmacological blockade with beta-adrenoreceptor antagonists, norepinephrine turnover measurement, qRT-PCR and western blot","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological pathway placement with in vivo model; single lab","pmids":["19577538"],"is_preprint":false},{"year":2010,"finding":"The carboxy-terminal 104 amino acids of Cidea are sufficient for lipid droplet targeting and triglyceride accumulation, while the N-terminal domain is required for the development of enlarged (fused) lipid droplets; Cidea promotes lipid storage by inhibiting lipolysis (reduces basal glycerol release in differentiated 3T3-L1 adipocytes).","method":"Expression of deletion constructs in 3T3-L1 and COS-1 cells, fluorescence microscopy, triglyceride measurement, glycerol release assay","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 1 — domain mapping with multiple constructs, direct biochemical readouts, two cell systems","pmids":["20810722"],"is_preprint":false},{"year":2010,"finding":"SREBP-1c directly binds the Cidea promoter via a sterol-regulatory element (SRE) in mouse hepatocytes, mediating insulin-induced Cidea expression; Cidea in turn mediates SREBP-1c-dependent hepatic lipid accumulation.","method":"Luciferase reporter assay, EMSA, ChIP, adenovirus-mediated SREBP-1c overexpression and Cidea knockdown in hepatocytes from wild-type and SREBP-1c-null mice","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — ChIP, EMSA, and reporter assay with KO rescue; multiple orthogonal methods","pmids":["20575761"],"is_preprint":false},{"year":2010,"finding":"In human adipocytes, insulin decreases CIDEA expression, and CIDEA (not CIDEC) is responsible for starvation-induced apoptosis; RNAi depletion of CIDEA inhibits apoptosis similarly to insulin treatment.","method":"siRNA knockdown of CIDEA/CIDEC in human adipocytes, apoptosis assays, lipid droplet size measurement","journal":"Journal of lipid research","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA with specific apoptotic phenotype, distinguishing CIDEA from CIDEC roles","pmids":["20154362"],"is_preprint":false},{"year":2011,"finding":"Insulin regulates CIDEA expression via PI3K and specifically through Akt1/2-dependent pathway; Akt1/2 knockdown prevents insulin-induced CIDEA downregulation and its anti-apoptotic effect.","method":"PI3K inhibitors (wortmannin, PI-103), Akt inhibitor (API-2), siRNA depletion of Akt1/2, apoptosis assay in human adipocytes","journal":"Journal of lipid research","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological plus RNAi with functional apoptosis readout; pathway position established","pmids":["21636835"],"is_preprint":false},{"year":2011,"finding":"CIDEA binds to liver X receptors (LXRs) in human white adipocytes and regulates their transcriptional activity; CIDEA localizes to both cytoplasm and nucleus in human white adipocytes.","method":"Protein-protein binding experiments, transactivation assays, cell fractionation of human white adipocytes","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct binding assay and transactivation with fractionation; single lab","pmids":["21315073"],"is_preprint":false},{"year":2011,"finding":"In pancreatic beta-cells, palmitic acid-induced apoptosis upregulates Cidea downstream of FoxO1; FoxO1 suppression reduces palmitic acid-induced Cidea expression and apoptosis, placing Cidea as a critical downstream target of FoxO1 in FFA-induced beta-cell death.","method":"siRNA knockdown of Cidea and FoxO1 in beta-cells, palmitic acid treatment, apoptosis assay","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — RNAi epistasis experiment placing Cidea downstream of FoxO1; single lab","pmids":["21945815"],"is_preprint":false},{"year":2012,"finding":"Cidea functions as a transcriptional coactivator of C/EBPbeta in mammary epithelial cells: it translocates to the nucleus via a nuclear bipartite signal, physically interacts with C/EBPbeta, promotes C/EBPbeta association with the Xdh (XOR) promoter, and displaces HDAC1, thereby inducing XOR expression and milk lipid secretion.","method":"Nuclear fractionation, co-immunoprecipitation of Cidea with C/EBPbeta, ChIP for C/EBPbeta and HDAC1 on Xdh promoter, Cidea-deficient mouse mammary glands, ectopic expression in vivo","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 1-2 — co-IP, ChIP, KO phenotype, ectopic expression in vivo with multiple orthogonal methods","pmids":["22245780"],"is_preprint":false},{"year":2012,"finding":"Cidea promotes hepatic lipid accumulation by sensing dietary saturated fatty acids; saturated FAs induce Cidea expression via SREBP1c, and Cidea protein stability in hepatocytes is increased by FA treatment. Cidea overexpression in mouse liver increases hepatic lipid and large lipid droplet formation; Cidea deficiency reduces lipid accumulation in ob/ob mice.","method":"Adenoviral overexpression and knockdown in mouse liver and hepatocytes, ob/ob mouse model, SREBP1c knockdown, FA treatment, lipid droplet measurement","journal":"Hepatology (Baltimore, Md.)","confidence":"High","confidence_rationale":"Tier 2 — multiple in vivo and in vitro models, SREBP1c epistasis, protein stability assay","pmids":["22278400"],"is_preprint":false},{"year":2014,"finding":"Cidea is required for normal sebaceous gland lipid storage and sebum secretion; Cidea-deficient mice accumulate many small lipid droplets in sebocytes instead of large ones, leading to reduced skin surface lipids, dry hair, and defective thermoregulation. Overexpression of Cidea in human SZ95 sebocytes increases lipid storage and large LD formation.","method":"Cidea knockout mice, sebocyte lipid droplet imaging, skin surface lipid analysis, overexpression in SZ95 human sebocytes","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with defined phenotype plus reciprocal gain-of-function in human cells","pmids":["24636991"],"is_preprint":false},{"year":2015,"finding":"CIDEA promotes lipid droplet fusion via an amphipathic helix that embeds in the LD phospholipid monolayer and binds phosphatidic acid (PA); CIDEA forms trans-complexes at LD-LD contact sites through its N-terminal domain and C-terminal dimerization region, interacting with cone-shaped PA to increase phospholipid barrier permeability and enable lipid transfer between droplets.","method":"Mutagenesis of amphipathic helix, PA-binding assay, reconstitution of LD-LD docking, CIDEA complex analysis at contact sites, brown adipocyte differentiation assay","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 — reconstitution, mutagenesis, lipid-binding assay, and structural analysis of LD fusion mechanism in one study","pmids":["26609809"],"is_preprint":false},{"year":2015,"finding":"Transgenic expression of human Cidea in mouse adipose tissue increases adipose tissue expandability; in obese transgenic mice, Cidea preserves perilipin-1 and Akt expression in adipose tissue, reduces macrophage accumulation, and maintains adiponectin expression, resulting in enhanced insulin sensitivity.","method":"aP2-hCidea transgenic mice, high-fat diet challenge at thermoneutrality, western blot for perilipin/Akt, adiponectin measurement, insulin tolerance test","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — gain-of-function transgenic model with multiple mechanistic readouts; independent from KO work","pmids":["26118629"],"is_preprint":false},{"year":2016,"finding":"Cidea protein levels in brown fat are regulated post-transcriptionally (not transcriptionally) and are elevated in the thermogenically recruited state; overexpressed Cidea markedly suppresses UCP1 activity in isolated BAT mitochondria without changing UCP1 protein levels, but Cidea itself is not localized to mitochondria, implying an indirect inhibitory mechanism.","method":"aP2-hCidea transgenic mice, UCP1 activity assay in isolated mitochondria, Cidea protein/mRNA quantification across recruitment states, subcellular localization","journal":"American journal of physiology. Endocrinology and metabolism","confidence":"High","confidence_rationale":"Tier 1-2 — direct UCP1 activity assay in isolated mitochondria, localization experiment, transgenic gain-of-function","pmids":["27923808"],"is_preprint":false},{"year":2019,"finding":"CIDEA acts as a transcriptional regulator in human adipocytes: during britening, it shuttles from lipid droplets to the nucleus via a nuclear bipartite signal in a concentration-dependent manner, where it inhibits LXRalpha repression of the UCP1 enhancer and strengthens PPARgamma binding to the UCP1 enhancer, driving UCP1 transcription and thermogenesis.","method":"CRISPR-Cas9nD10A knockout of CIDEA in primary human adipocytes, nuclear fractionation, UCP1 enhancer reporter assay, chromatin binding assays, re-expression rescue","journal":"iScience","confidence":"High","confidence_rationale":"Tier 1-2 — CRISPR KO with rescue, reporter assay, nuclear fractionation and chromatin binding; multiple orthogonal methods","pmids":["31563853"],"is_preprint":false},{"year":2021,"finding":"ER stress increases Cidea mRNA levels (partly through mRNA stabilization) and stabilizes CIDE-A protein against proteasomal degradation; elevated CIDE-A expression under ER stress accompanies increased cell death. ATF6 negatively regulates Cidea mRNA under ER stress.","method":"Acute and chronic ER stress induction in PCCL3 thyrocytes and other cell types, mRNA stability assays, proteasome inhibition, ATF6 modulation, cell death assays","journal":"JCI insight","confidence":"Medium","confidence_rationale":"Tier 2 — mRNA stability and protein stabilization assays with ATF6 pathway placement; single lab","pmids":["33661766"],"is_preprint":false},{"year":2022,"finding":"METTL16 methyltransferase upregulates CIDEA expression in hepatocytes through m6A-dependent translational regulation, contributing to NAFLD progression.","method":"m6A sequencing, METTL16 overexpression and knockdown in HepG2 cells, quantification of CIDEA expression","journal":"PeerJ","confidence":"Low","confidence_rationale":"Tier 3 — single lab, limited mechanistic follow-up of m6A-CIDEA axis","pmids":["36518278"],"is_preprint":false},{"year":2022,"finding":"SENP2 (SUMO-specific protease 2) increases CIDEA expression by desumoylating ERRalpha, which then cooperates with PGC-1alpha to activate CIDEA transcription; palmitate treatment increases SENP2 and CIDEA levels and SENP2 or ERRalpha knockdown abolishes palmitate-induced CIDEA expression.","method":"SENP2 overexpression in 3T3-L1 adipocytes, ERRalpha knockdown, siRNA, palmitate treatment, luciferase reporter assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2-3 — defined pathway (SENP2→ERRalpha→CIDEA) with RNAi and reporter assays; single lab","pmids":["37748256"],"is_preprint":false},{"year":2023,"finding":"Egr-1 transcription factor rhythmically couples with and represses Cidea expression in mouse liver; Egr-1 deletion disrupts this rhythmic coupling, leading to increased Cidea expression, large lipid droplet formation, and age-related hepatic metabolic dysfunction.","method":"Egr-1 knockout mice, circadian gene expression profiling, lipid droplet size analysis, circadian light-shift experiment","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — KO mouse with defined Cidea phenotype and transcriptional coupling; single lab","pmids":["36964140"],"is_preprint":false},{"year":2023,"finding":"DNMT3B methylates the CIDEA promoter to suppress its expression; LPS-induced reduction of DNMT3B leads to promoter hypomethylation, increased SREBP-1c binding, and elevated CIDEA expression promoting hepatic lipid accumulation. Cidea knockdown reverses LPS-induced lipogenesis.","method":"DNMT3B overexpression/knockdown in mice and hepatocytes, bisulfite methylation assay of CIDEA promoter, SREBP-1c ChIP, CIDEA knockdown rescue","journal":"Cellular and molecular gastroenterology and hepatology","confidence":"Medium","confidence_rationale":"Tier 2 — promoter methylation assay, ChIP, and epistasis rescue; single lab","pmids":["37703946"],"is_preprint":false},{"year":2008,"finding":"TNF-alpha negatively regulates CIDEA transcription in human adipocytes at least in part through an NF-kappaB binding site at position -163/-151 in the human CIDEA promoter; basal transcription is confined to the 97 bp upstream of the TSS.","method":"Luciferase reporter assays with deletion and mutant constructs, EMSA, TNF-alpha treatment of human adipocytes and 3T3-L1 cells","journal":"International journal of obesity (2005)","confidence":"Medium","confidence_rationale":"Tier 1-2 — EMSA and reporter mutagenesis with functional NF-kappaB site validation; single lab","pmids":["18607384"],"is_preprint":false}],"current_model":"CIDEA is a multifunctional CIDE-domain protein that (1) localizes to lipid droplets via its C-terminal domain, where it promotes lipid droplet enlargement and fusion through PA-binding amphipathic helix-mediated trans-complexes at LD-LD contact sites; (2) inhibits lipolysis and AMPK activity in brown and white adipose tissue via ubiquitin-proteasome-mediated AMPK-beta degradation; (3) acts as an indirect inhibitor of UCP1 thermogenic activity in BAT; (4) translocates to the nucleus where it acts as a transcriptional coactivator of C/EBPbeta (in mammary glands) and inhibits LXRalpha while strengthening PPARgamma at the UCP1 enhancer (in beige adipocytes); (5) is itself regulated at the protein level by ubiquitin-proteasomal degradation (with K23 as a key ubiquitination site) and transcriptionally by PPARgamma, PPARalpha, SREBP-1c, PGC-1alpha/RIP140, NF-kappaB (downstream of TNF-alpha), Egr-1, and ERRalpha/SENP2."},"narrative":{"teleology":[{"year":1998,"claim":"The initial identification of CIDEA as a DFF45-homologous cell death activator established that its C-terminal domain is necessary and sufficient for apoptosis induction, while the N-terminal CIDE domain mediates inhibition by DFF45, framing the protein as a modular apoptosis effector.","evidence":"Transfection of deletion mutants in 293T cells with DNA fragmentation and caspase-inhibitor assays","pmids":["9564035"],"confidence":"High","gaps":["Physiological cell type for CIDE-domain-mediated apoptosis unclear","Endogenous DFF45 interaction not validated in vivo"]},{"year":2003,"claim":"Generation of Cidea-null mice revealed that Cidea suppresses UCP1 activity and restrains BAT thermogenesis and lipolysis, positioning it as a negative regulator of energy expenditure — knockout mice were lean, hypermetabolic, and resistant to diet-induced obesity.","evidence":"Cidea knockout mouse with metabolic rate, cold challenge, and direct UCP1 activity assays","pmids":["12910269"],"confidence":"High","gaps":["Molecular mechanism of UCP1 inhibition unresolved","Whether Cidea acts on UCP1 directly or indirectly was unclear"]},{"year":2005,"claim":"RNAi in human adipocytes demonstrated that CIDEA cell-autonomously suppresses lipolysis and that TNF-α feeds back to repress CIDEA via JNK, establishing a regulatory loop between CIDEA and inflammatory signaling.","evidence":"siRNA knockdown in human adipocytes with lipolysis and TNF-α secretion readouts plus JNK inhibitor","pmids":["15919794"],"confidence":"High","gaps":["Direct anti-lipolytic target of CIDEA not identified","Whether TNF-α/JNK axis acts transcriptionally or post-transcriptionally was incompletely resolved"]},{"year":2007,"claim":"Two studies clarified CIDEA regulation: its protein is controlled by ubiquitin-proteasomal degradation with K23 as the principal ubiquitination site, while its transcription is driven by PPARα and PPARγ through a shared PPRE in the promoter — establishing dual-level control of CIDEA abundance.","evidence":"Cycloheximide chase, ubiquitination assays with K-to-A mutants; ChIP, EMSA, and reporter assays for PPRE","pmids":["17711404","17462989"],"confidence":"High","gaps":["E3 ubiquitin ligase responsible for K23 ubiquitination not identified","Relative contributions of PPARα vs PPARγ in different tissues unclear"]},{"year":2008,"claim":"A series of studies repositioned CIDEA from a mitochondrial protein to a lipid-droplet-resident factor: CIDEA co-localizes with perilipin on lipid droplets and drives droplet enlargement; separately, it interacts with AMPK-β at the ER to promote AMPK-β degradation, and its transcription is repressed by TNF-α/NF-κB and regulated by PGC-1α/RIP140 via ERRα.","evidence":"GFP-fusion imaging and co-localization in adipocytes; co-IP and ubiquitination of AMPK-β; reporter assays identifying NF-κB site and ERRα-dependent regulation","pmids":["18509062","18480843","18607384","18794372"],"confidence":"High","gaps":["Lipid-droplet targeting domain not yet mapped","Mechanism by which lipid-droplet CIDEA inhibits UCP1 still unresolved"]},{"year":2010,"claim":"Domain mapping showed that the C-terminal 104 amino acids are sufficient for lipid-droplet targeting and triglyceride accumulation while the N-terminal domain is required for droplet enlargement/fusion, and SREBP-1c was identified as a direct transcriptional activator of Cidea via a promoter SRE element in hepatocytes.","evidence":"Deletion constructs in 3T3-L1/COS-1 cells with lipolysis readout; ChIP, EMSA, and reporter assays with SREBP-1c-null hepatocytes","pmids":["20810722","20575761"],"confidence":"High","gaps":["Whether N- and C-terminal domains cooperate through dimerization was not established","Relative importance of PPARs vs SREBP-1c in hepatic Cidea expression unclear"]},{"year":2012,"claim":"CIDEA was shown to function as a transcriptional coactivator: in mammary epithelial cells it translocates to the nucleus via a bipartite NLS, binds C/EBPβ, displaces HDAC1 from the Xdh promoter, and drives milk-lipid secretion — extending CIDEA's role beyond lipid-droplet biology to gene regulation.","evidence":"Co-IP of CIDEA–C/EBPβ, ChIP at Xdh promoter, Cidea-deficient mouse mammary glands, ectopic re-expression","pmids":["22245780"],"confidence":"High","gaps":["Whether nuclear coactivator function extends to other promoters beyond Xdh was unknown","Whether nuclear translocation occurs in adipocytes was not tested"]},{"year":2015,"claim":"The biophysical mechanism of lipid droplet fusion was resolved: CIDEA forms trans-complexes at LD–LD contact sites through N-terminal and C-terminal dimerization, and an amphipathic helix embeds in the phospholipid monolayer where it binds phosphatidic acid to increase barrier permeability and enable lipid transfer.","evidence":"Amphipathic helix mutagenesis, PA-binding assay, reconstitution of LD–LD docking in brown adipocytes","pmids":["26609809"],"confidence":"High","gaps":["Structural model of the CIDEA trans-complex at atomic resolution lacking","Regulation of PA availability at contact sites not addressed"]},{"year":2016,"claim":"The long-standing question of how lipid-droplet-localized CIDEA inhibits mitochondrial UCP1 was partially resolved: overexpressed CIDEA suppresses UCP1 activity in isolated BAT mitochondria without changing UCP1 protein levels and without being mitochondrially localized, confirming an indirect inhibitory mechanism.","evidence":"UCP1 activity assay in isolated mitochondria from aP2-hCidea transgenic mice plus subcellular localization","pmids":["27923808"],"confidence":"High","gaps":["Identity of the intermediary signal between lipid droplets and mitochondria unknown","Whether AMPK-β degradation accounts for UCP1 suppression not tested"]},{"year":2019,"claim":"Nuclear CIDEA function was extended to adipocyte thermogenesis: during britening of human adipocytes, CIDEA shuttles from lipid droplets to the nucleus in a concentration-dependent manner, where it inhibits LXRα-mediated repression and strengthens PPARγ binding at the UCP1 enhancer to drive UCP1 transcription.","evidence":"CRISPR knockout in primary human adipocytes with rescue, UCP1 enhancer reporter, nuclear fractionation, chromatin binding assays","pmids":["31563853"],"confidence":"High","gaps":["How CIDEA concentration sensing triggers nuclear import is unknown","Whether LXRα inhibition and PPARγ enhancement are direct or indirect remains incompletely defined"]},{"year":2023,"claim":"Hepatic Cidea expression was found to be rhythmically repressed by Egr-1 and regulated by DNMT3B-mediated promoter methylation controlling SREBP-1c access, adding circadian and epigenetic layers to the transcriptional regulation of Cidea in liver lipid metabolism.","evidence":"Egr-1 knockout mice with circadian profiling; DNMT3B overexpression/knockdown with bisulfite sequencing and ChIP in hepatocytes","pmids":["36964140","37703946"],"confidence":"Medium","gaps":["Whether Egr-1 directly binds the Cidea promoter or acts indirectly not fully established","Interaction between circadian and epigenetic regulatory layers not tested"]},{"year":null,"claim":"The molecular intermediary by which lipid-droplet-localized CIDEA indirectly suppresses mitochondrial UCP1 activity remains unidentified, and the E3 ligase(s) mediating CIDEA ubiquitination at K23 have not been determined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No candidate E3 ligase for CIDEA ubiquitination identified","Indirect mechanism of UCP1 suppression entirely unresolved","High-resolution structure of full-length CIDEA or the LD fusion trans-complex not available"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[16,22]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[19]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,6,21]}],"localization":[{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[5,10,19]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[16,22,14]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[5,10,11,17,19]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,12]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[16,22]}],"complexes":[],"partners":["PRKAB1","CEBPB","NR1H3","PPARG","DFF45","PLIN1"],"other_free_text":[]},"mechanistic_narrative":"CIDEA is a CIDE-domain protein that functions as a central regulator of lipid droplet dynamics, energy metabolism, and transcriptional control in adipose tissue, liver, and mammary gland. On lipid droplets, CIDEA promotes droplet enlargement and fusion by forming trans-complexes at droplet–droplet contact sites through an amphipathic helix that binds phosphatidic acid in the phospholipid monolayer, while simultaneously inhibiting lipolysis [PMID:26609809, PMID:20810722, PMID:18509062]. CIDEA also suppresses AMPK activity by binding the AMPK-β subunit at the endoplasmic reticulum and promoting its ubiquitin-dependent proteasomal degradation, and indirectly inhibits UCP1 thermogenic activity in brown adipose tissue through a non-mitochondrial mechanism [PMID:18480843, PMID:27923808, PMID:12910269]. In a concentration-dependent manner, CIDEA translocates to the nucleus where it acts as a transcriptional coactivator of C/EBPβ to drive milk-lipid secretion in mammary epithelium and modulates the UCP1 enhancer by inhibiting LXRα repression and strengthening PPARγ binding during adipocyte britening [PMID:22245780, PMID:31563853]."},"prefetch_data":{"uniprot":{"accession":"O60543","full_name":"Lipid transferase CIDEA","aliases":["Cell death activator CIDE-A","Cell death-inducing DFFA-like effector A"],"length_aa":219,"mass_kda":24.7,"function":"Lipid transferase that promotes unilocular lipid droplet formation by mediating lipid droplet fusion (PubMed:19843876, PubMed:26118629). Lipid droplet fusion promotes their enlargement, restricting lipolysis and favoring lipid storage (PubMed:19843876). Localizes on the lipid droplet surface, at focal contact sites between lipid droplets, and mediates atypical lipid droplet fusion by promoting directional net neutral lipid transfer from the smaller to larger lipid droplets (By similarity). The transfer direction may be driven by the internal pressure difference between the contacting lipid droplet pair and occurs at a lower rate than that promoted by CIDEC (By similarity). May also act as a CEBPB coactivator in epithelial cells to control the expression of a subset of CEBPB downstream target genes, including ID2, IGF1, PRLR, SOCS1, SOCS3, XDH, but not casein (By similarity). By interacting with CEBPB, strengthens the association of CEBPB with the XDH promoter, increases histone acetylation and dissociates HDAC1 from the promoter (By similarity). When overexpressed, induces apoptosis; the physiological significance of its role in apoptosis is unclear (By similarity)","subcellular_location":"Lipid droplet; Nucleus","url":"https://www.uniprot.org/uniprotkb/O60543/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CIDEA","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/CIDEA","total_profiled":1310},"omim":[{"mim_id":"612120","title":"CELL DEATH-INDUCING DFFA-LIKE EFFECTOR C; CIDEC","url":"https://www.omim.org/entry/612120"},{"mim_id":"604441","title":"CELL DEATH-INDUCING DFFA-LIKE EFFECTOR B; CIDEB","url":"https://www.omim.org/entry/604441"},{"mim_id":"604440","title":"CELL DEATH-INDUCING DFFA-LIKE EFFECTOR A; CIDEA","url":"https://www.omim.org/entry/604440"},{"mim_id":"601882","title":"DNA FRAGMENTATION FACTOR, 45-KD, ALPHA SUBUNIT; DFFA","url":"https://www.omim.org/entry/601882"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"adipose 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CIDEA-induced DNA fragmentation is inhibited by DFF45 but not by caspase inhibitors.\",\n      \"method\": \"Transfection of deletion mutants in 293T cells, DNA fragmentation assay, inhibition studies with DFF45 and caspase inhibitors\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — domain mutagenesis with multiple functional readouts, replicated across constructs\",\n      \"pmids\": [\"9564035\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Cidea is expressed at high levels in brown adipose tissue mitochondria and directly suppresses UCP1 activity, thereby regulating thermogenesis and lipolysis; Cidea-null mice have increased metabolic rate, elevated BAT lipolysis, and resistance to diet-induced obesity and diabetes.\",\n      \"method\": \"Cidea knockout mouse model, metabolic rate measurements, cold challenge, direct suppression of UCP1 activity assay\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO mouse with multiple orthogonal phenotypic readouts and direct UCP1 activity assay, highly cited foundational study\",\n      \"pmids\": [\"12910269\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"In human adipocytes, CIDEA regulates lipolysis; RNAi-mediated depletion of CIDEA stimulates lipolysis and increases TNF-alpha secretion by a post-transcriptional mechanism. TNF-alpha in turn decreases CIDEA expression via the JNK (c-Jun N-terminal kinase) pathway.\",\n      \"method\": \"RNA interference in human adipocytes, lipolysis assay, TNF-alpha secretion measurement, pharmacological inhibition of JNK\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — RNAi with defined cellular phenotype plus pathway placement via JNK inhibitor\",\n      \"pmids\": [\"15919794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Cidea protein is regulated by ubiquitin-proteasome-mediated degradation; it is polyubiquitinated primarily at Lys23 in its N-terminal region, and mutation of N-terminal lysine residues (N-5KA mutant) greatly stabilizes the protein.\",\n      \"method\": \"Cycloheximide chase, proteasome inhibitor treatment, ubiquitination assay, site-directed mutagenesis of lysine residues in multiple cell lines and brown adipocytes\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro mutagenesis combined with biochemical ubiquitination assay across multiple cell systems\",\n      \"pmids\": [\"17711404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Cidea gene expression in mouse liver is transcriptionally regulated by both PPARalpha and PPARgamma through a shared proximal PPRE element (Cidea-PPRE1 at -680/-668) in the Cidea promoter.\",\n      \"method\": \"Transactivation/luciferase reporter assays, gel-shift (EMSA), chromatin immunoprecipitation with PPARalpha and PPARgamma ligands\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP, EMSA, and reporter assays with orthogonal methods confirming functional PPRE\",\n      \"pmids\": [\"17462989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Cidea colocalizes with lipid droplets (not mitochondria) in human and mouse adipocytes, co-localizing with perilipin; ectopic expression of Cidea-GFP greatly enhances lipid droplet size in preadipocytes and COS cells, and Cidea is regulated by PPARgamma.\",\n      \"method\": \"Fluorescence microscopy (GFP fusion protein), co-localization with perilipin, RNAi lipolysis assay, rosiglitazone treatment in mice\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct imaging with functional consequence (lipid droplet enlargement), multiple cell systems\",\n      \"pmids\": [\"18509062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Cidea forms a complex with the beta subunit of AMPK (but not alpha or gamma subunits) in the endoplasmic reticulum, promoting ubiquitination-dependent proteasomal degradation of the AMPK-beta subunit, thereby reducing AMPK protein levels and enzymatic activity in brown adipose tissue.\",\n      \"method\": \"Co-immunoprecipitation in vivo, co-localization in ER, co-expression ubiquitination assay, AMPK activity measurement in Cidea-/- adipocytes\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reciprocal co-IP, ER co-localization, in-cell ubiquitination assay, KO rescue, multiple methods in one study\",\n      \"pmids\": [\"18480843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"RIP140 and PGC-1alpha regulate CIDEA expression in brown adipocytes: PGC-1alpha induces while RIP140 represses CIDEA promoter activity via estrogen-related receptor alpha (ERRalpha) and NRF-1 binding sites; RIP140 directly interacts with PGC-1alpha to suppress its coactivator activity.\",\n      \"method\": \"Luciferase reporter assays, promoter deletion analysis, protein-protein interaction assay (RIP140-PGC-1alpha), ectopic expression in brown adipocytes and nonadipogenic lines\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reporter assay with defined binding sites, direct protein interaction, and functional lipid droplet formation assay\",\n      \"pmids\": [\"18794372\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In apoptotic conditions, CIDEa redistributes from mitochondria to the nucleus in HeLa cells, and nuclear accumulation correlates with increased cell death.\",\n      \"method\": \"Immunocytochemistry and subcellular fractionation with tetracycline-inducible CIDEa expression, camptothecin/valinomycin treatment\",\n      \"journal\": \"General physiology and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct fractionation and imaging, but single lab and limited mechanistic follow-up\",\n      \"pmids\": [\"18645223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Cold exposure down-regulates CIDEA mRNA and protein in rat interscapular BAT via sympathetically activated beta3-adrenoreceptors, and this effect is blocked by propranolol (non-selective beta-blocker) or SR59230A (selective beta3-antagonist).\",\n      \"method\": \"Cold exposure in vivo, pharmacological blockade with beta-adrenoreceptor antagonists, norepinephrine turnover measurement, qRT-PCR and western blot\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological pathway placement with in vivo model; single lab\",\n      \"pmids\": [\"19577538\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The carboxy-terminal 104 amino acids of Cidea are sufficient for lipid droplet targeting and triglyceride accumulation, while the N-terminal domain is required for the development of enlarged (fused) lipid droplets; Cidea promotes lipid storage by inhibiting lipolysis (reduces basal glycerol release in differentiated 3T3-L1 adipocytes).\",\n      \"method\": \"Expression of deletion constructs in 3T3-L1 and COS-1 cells, fluorescence microscopy, triglyceride measurement, glycerol release assay\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — domain mapping with multiple constructs, direct biochemical readouts, two cell systems\",\n      \"pmids\": [\"20810722\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SREBP-1c directly binds the Cidea promoter via a sterol-regulatory element (SRE) in mouse hepatocytes, mediating insulin-induced Cidea expression; Cidea in turn mediates SREBP-1c-dependent hepatic lipid accumulation.\",\n      \"method\": \"Luciferase reporter assay, EMSA, ChIP, adenovirus-mediated SREBP-1c overexpression and Cidea knockdown in hepatocytes from wild-type and SREBP-1c-null mice\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP, EMSA, and reporter assay with KO rescue; multiple orthogonal methods\",\n      \"pmids\": [\"20575761\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In human adipocytes, insulin decreases CIDEA expression, and CIDEA (not CIDEC) is responsible for starvation-induced apoptosis; RNAi depletion of CIDEA inhibits apoptosis similarly to insulin treatment.\",\n      \"method\": \"siRNA knockdown of CIDEA/CIDEC in human adipocytes, apoptosis assays, lipid droplet size measurement\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA with specific apoptotic phenotype, distinguishing CIDEA from CIDEC roles\",\n      \"pmids\": [\"20154362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Insulin regulates CIDEA expression via PI3K and specifically through Akt1/2-dependent pathway; Akt1/2 knockdown prevents insulin-induced CIDEA downregulation and its anti-apoptotic effect.\",\n      \"method\": \"PI3K inhibitors (wortmannin, PI-103), Akt inhibitor (API-2), siRNA depletion of Akt1/2, apoptosis assay in human adipocytes\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological plus RNAi with functional apoptosis readout; pathway position established\",\n      \"pmids\": [\"21636835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"CIDEA binds to liver X receptors (LXRs) in human white adipocytes and regulates their transcriptional activity; CIDEA localizes to both cytoplasm and nucleus in human white adipocytes.\",\n      \"method\": \"Protein-protein binding experiments, transactivation assays, cell fractionation of human white adipocytes\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct binding assay and transactivation with fractionation; single lab\",\n      \"pmids\": [\"21315073\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In pancreatic beta-cells, palmitic acid-induced apoptosis upregulates Cidea downstream of FoxO1; FoxO1 suppression reduces palmitic acid-induced Cidea expression and apoptosis, placing Cidea as a critical downstream target of FoxO1 in FFA-induced beta-cell death.\",\n      \"method\": \"siRNA knockdown of Cidea and FoxO1 in beta-cells, palmitic acid treatment, apoptosis assay\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — RNAi epistasis experiment placing Cidea downstream of FoxO1; single lab\",\n      \"pmids\": [\"21945815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Cidea functions as a transcriptional coactivator of C/EBPbeta in mammary epithelial cells: it translocates to the nucleus via a nuclear bipartite signal, physically interacts with C/EBPbeta, promotes C/EBPbeta association with the Xdh (XOR) promoter, and displaces HDAC1, thereby inducing XOR expression and milk lipid secretion.\",\n      \"method\": \"Nuclear fractionation, co-immunoprecipitation of Cidea with C/EBPbeta, ChIP for C/EBPbeta and HDAC1 on Xdh promoter, Cidea-deficient mouse mammary glands, ectopic expression in vivo\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — co-IP, ChIP, KO phenotype, ectopic expression in vivo with multiple orthogonal methods\",\n      \"pmids\": [\"22245780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Cidea promotes hepatic lipid accumulation by sensing dietary saturated fatty acids; saturated FAs induce Cidea expression via SREBP1c, and Cidea protein stability in hepatocytes is increased by FA treatment. Cidea overexpression in mouse liver increases hepatic lipid and large lipid droplet formation; Cidea deficiency reduces lipid accumulation in ob/ob mice.\",\n      \"method\": \"Adenoviral overexpression and knockdown in mouse liver and hepatocytes, ob/ob mouse model, SREBP1c knockdown, FA treatment, lipid droplet measurement\",\n      \"journal\": \"Hepatology (Baltimore, Md.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple in vivo and in vitro models, SREBP1c epistasis, protein stability assay\",\n      \"pmids\": [\"22278400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Cidea is required for normal sebaceous gland lipid storage and sebum secretion; Cidea-deficient mice accumulate many small lipid droplets in sebocytes instead of large ones, leading to reduced skin surface lipids, dry hair, and defective thermoregulation. Overexpression of Cidea in human SZ95 sebocytes increases lipid storage and large LD formation.\",\n      \"method\": \"Cidea knockout mice, sebocyte lipid droplet imaging, skin surface lipid analysis, overexpression in SZ95 human sebocytes\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with defined phenotype plus reciprocal gain-of-function in human cells\",\n      \"pmids\": [\"24636991\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CIDEA promotes lipid droplet fusion via an amphipathic helix that embeds in the LD phospholipid monolayer and binds phosphatidic acid (PA); CIDEA forms trans-complexes at LD-LD contact sites through its N-terminal domain and C-terminal dimerization region, interacting with cone-shaped PA to increase phospholipid barrier permeability and enable lipid transfer between droplets.\",\n      \"method\": \"Mutagenesis of amphipathic helix, PA-binding assay, reconstitution of LD-LD docking, CIDEA complex analysis at contact sites, brown adipocyte differentiation assay\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution, mutagenesis, lipid-binding assay, and structural analysis of LD fusion mechanism in one study\",\n      \"pmids\": [\"26609809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Transgenic expression of human Cidea in mouse adipose tissue increases adipose tissue expandability; in obese transgenic mice, Cidea preserves perilipin-1 and Akt expression in adipose tissue, reduces macrophage accumulation, and maintains adiponectin expression, resulting in enhanced insulin sensitivity.\",\n      \"method\": \"aP2-hCidea transgenic mice, high-fat diet challenge at thermoneutrality, western blot for perilipin/Akt, adiponectin measurement, insulin tolerance test\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function transgenic model with multiple mechanistic readouts; independent from KO work\",\n      \"pmids\": [\"26118629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Cidea protein levels in brown fat are regulated post-transcriptionally (not transcriptionally) and are elevated in the thermogenically recruited state; overexpressed Cidea markedly suppresses UCP1 activity in isolated BAT mitochondria without changing UCP1 protein levels, but Cidea itself is not localized to mitochondria, implying an indirect inhibitory mechanism.\",\n      \"method\": \"aP2-hCidea transgenic mice, UCP1 activity assay in isolated mitochondria, Cidea protein/mRNA quantification across recruitment states, subcellular localization\",\n      \"journal\": \"American journal of physiology. Endocrinology and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct UCP1 activity assay in isolated mitochondria, localization experiment, transgenic gain-of-function\",\n      \"pmids\": [\"27923808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CIDEA acts as a transcriptional regulator in human adipocytes: during britening, it shuttles from lipid droplets to the nucleus via a nuclear bipartite signal in a concentration-dependent manner, where it inhibits LXRalpha repression of the UCP1 enhancer and strengthens PPARgamma binding to the UCP1 enhancer, driving UCP1 transcription and thermogenesis.\",\n      \"method\": \"CRISPR-Cas9nD10A knockout of CIDEA in primary human adipocytes, nuclear fractionation, UCP1 enhancer reporter assay, chromatin binding assays, re-expression rescue\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — CRISPR KO with rescue, reporter assay, nuclear fractionation and chromatin binding; multiple orthogonal methods\",\n      \"pmids\": [\"31563853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ER stress increases Cidea mRNA levels (partly through mRNA stabilization) and stabilizes CIDE-A protein against proteasomal degradation; elevated CIDE-A expression under ER stress accompanies increased cell death. ATF6 negatively regulates Cidea mRNA under ER stress.\",\n      \"method\": \"Acute and chronic ER stress induction in PCCL3 thyrocytes and other cell types, mRNA stability assays, proteasome inhibition, ATF6 modulation, cell death assays\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mRNA stability and protein stabilization assays with ATF6 pathway placement; single lab\",\n      \"pmids\": [\"33661766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"METTL16 methyltransferase upregulates CIDEA expression in hepatocytes through m6A-dependent translational regulation, contributing to NAFLD progression.\",\n      \"method\": \"m6A sequencing, METTL16 overexpression and knockdown in HepG2 cells, quantification of CIDEA expression\",\n      \"journal\": \"PeerJ\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, limited mechanistic follow-up of m6A-CIDEA axis\",\n      \"pmids\": [\"36518278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SENP2 (SUMO-specific protease 2) increases CIDEA expression by desumoylating ERRalpha, which then cooperates with PGC-1alpha to activate CIDEA transcription; palmitate treatment increases SENP2 and CIDEA levels and SENP2 or ERRalpha knockdown abolishes palmitate-induced CIDEA expression.\",\n      \"method\": \"SENP2 overexpression in 3T3-L1 adipocytes, ERRalpha knockdown, siRNA, palmitate treatment, luciferase reporter assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — defined pathway (SENP2→ERRalpha→CIDEA) with RNAi and reporter assays; single lab\",\n      \"pmids\": [\"37748256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Egr-1 transcription factor rhythmically couples with and represses Cidea expression in mouse liver; Egr-1 deletion disrupts this rhythmic coupling, leading to increased Cidea expression, large lipid droplet formation, and age-related hepatic metabolic dysfunction.\",\n      \"method\": \"Egr-1 knockout mice, circadian gene expression profiling, lipid droplet size analysis, circadian light-shift experiment\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with defined Cidea phenotype and transcriptional coupling; single lab\",\n      \"pmids\": [\"36964140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DNMT3B methylates the CIDEA promoter to suppress its expression; LPS-induced reduction of DNMT3B leads to promoter hypomethylation, increased SREBP-1c binding, and elevated CIDEA expression promoting hepatic lipid accumulation. Cidea knockdown reverses LPS-induced lipogenesis.\",\n      \"method\": \"DNMT3B overexpression/knockdown in mice and hepatocytes, bisulfite methylation assay of CIDEA promoter, SREBP-1c ChIP, CIDEA knockdown rescue\",\n      \"journal\": \"Cellular and molecular gastroenterology and hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — promoter methylation assay, ChIP, and epistasis rescue; single lab\",\n      \"pmids\": [\"37703946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"TNF-alpha negatively regulates CIDEA transcription in human adipocytes at least in part through an NF-kappaB binding site at position -163/-151 in the human CIDEA promoter; basal transcription is confined to the 97 bp upstream of the TSS.\",\n      \"method\": \"Luciferase reporter assays with deletion and mutant constructs, EMSA, TNF-alpha treatment of human adipocytes and 3T3-L1 cells\",\n      \"journal\": \"International journal of obesity (2005)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — EMSA and reporter mutagenesis with functional NF-kappaB site validation; single lab\",\n      \"pmids\": [\"18607384\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CIDEA is a multifunctional CIDE-domain protein that (1) localizes to lipid droplets via its C-terminal domain, where it promotes lipid droplet enlargement and fusion through PA-binding amphipathic helix-mediated trans-complexes at LD-LD contact sites; (2) inhibits lipolysis and AMPK activity in brown and white adipose tissue via ubiquitin-proteasome-mediated AMPK-beta degradation; (3) acts as an indirect inhibitor of UCP1 thermogenic activity in BAT; (4) translocates to the nucleus where it acts as a transcriptional coactivator of C/EBPbeta (in mammary glands) and inhibits LXRalpha while strengthening PPARgamma at the UCP1 enhancer (in beige adipocytes); (5) is itself regulated at the protein level by ubiquitin-proteasomal degradation (with K23 as a key ubiquitination site) and transcriptionally by PPARgamma, PPARalpha, SREBP-1c, PGC-1alpha/RIP140, NF-kappaB (downstream of TNF-alpha), Egr-1, and ERRalpha/SENP2.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CIDEA is a CIDE-domain protein that functions as a central regulator of lipid droplet dynamics, energy metabolism, and transcriptional control in adipose tissue, liver, and mammary gland. On lipid droplets, CIDEA promotes droplet enlargement and fusion by forming trans-complexes at droplet–droplet contact sites through an amphipathic helix that binds phosphatidic acid in the phospholipid monolayer, while simultaneously inhibiting lipolysis [PMID:26609809, PMID:20810722, PMID:18509062]. CIDEA also suppresses AMPK activity by binding the AMPK-β subunit at the endoplasmic reticulum and promoting its ubiquitin-dependent proteasomal degradation, and indirectly inhibits UCP1 thermogenic activity in brown adipose tissue through a non-mitochondrial mechanism [PMID:18480843, PMID:27923808, PMID:12910269]. In a concentration-dependent manner, CIDEA translocates to the nucleus where it acts as a transcriptional coactivator of C/EBPβ to drive milk-lipid secretion in mammary epithelium and modulates the UCP1 enhancer by inhibiting LXRα repression and strengthening PPARγ binding during adipocyte britening [PMID:22245780, PMID:31563853].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"The initial identification of CIDEA as a DFF45-homologous cell death activator established that its C-terminal domain is necessary and sufficient for apoptosis induction, while the N-terminal CIDE domain mediates inhibition by DFF45, framing the protein as a modular apoptosis effector.\",\n      \"evidence\": \"Transfection of deletion mutants in 293T cells with DNA fragmentation and caspase-inhibitor assays\",\n      \"pmids\": [\"9564035\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological cell type for CIDE-domain-mediated apoptosis unclear\", \"Endogenous DFF45 interaction not validated in vivo\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Generation of Cidea-null mice revealed that Cidea suppresses UCP1 activity and restrains BAT thermogenesis and lipolysis, positioning it as a negative regulator of energy expenditure — knockout mice were lean, hypermetabolic, and resistant to diet-induced obesity.\",\n      \"evidence\": \"Cidea knockout mouse with metabolic rate, cold challenge, and direct UCP1 activity assays\",\n      \"pmids\": [\"12910269\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of UCP1 inhibition unresolved\", \"Whether Cidea acts on UCP1 directly or indirectly was unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"RNAi in human adipocytes demonstrated that CIDEA cell-autonomously suppresses lipolysis and that TNF-α feeds back to repress CIDEA via JNK, establishing a regulatory loop between CIDEA and inflammatory signaling.\",\n      \"evidence\": \"siRNA knockdown in human adipocytes with lipolysis and TNF-α secretion readouts plus JNK inhibitor\",\n      \"pmids\": [\"15919794\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct anti-lipolytic target of CIDEA not identified\", \"Whether TNF-α/JNK axis acts transcriptionally or post-transcriptionally was incompletely resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Two studies clarified CIDEA regulation: its protein is controlled by ubiquitin-proteasomal degradation with K23 as the principal ubiquitination site, while its transcription is driven by PPARα and PPARγ through a shared PPRE in the promoter — establishing dual-level control of CIDEA abundance.\",\n      \"evidence\": \"Cycloheximide chase, ubiquitination assays with K-to-A mutants; ChIP, EMSA, and reporter assays for PPRE\",\n      \"pmids\": [\"17711404\", \"17462989\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E3 ubiquitin ligase responsible for K23 ubiquitination not identified\", \"Relative contributions of PPARα vs PPARγ in different tissues unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"A series of studies repositioned CIDEA from a mitochondrial protein to a lipid-droplet-resident factor: CIDEA co-localizes with perilipin on lipid droplets and drives droplet enlargement; separately, it interacts with AMPK-β at the ER to promote AMPK-β degradation, and its transcription is repressed by TNF-α/NF-κB and regulated by PGC-1α/RIP140 via ERRα.\",\n      \"evidence\": \"GFP-fusion imaging and co-localization in adipocytes; co-IP and ubiquitination of AMPK-β; reporter assays identifying NF-κB site and ERRα-dependent regulation\",\n      \"pmids\": [\"18509062\", \"18480843\", \"18607384\", \"18794372\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Lipid-droplet targeting domain not yet mapped\", \"Mechanism by which lipid-droplet CIDEA inhibits UCP1 still unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Domain mapping showed that the C-terminal 104 amino acids are sufficient for lipid-droplet targeting and triglyceride accumulation while the N-terminal domain is required for droplet enlargement/fusion, and SREBP-1c was identified as a direct transcriptional activator of Cidea via a promoter SRE element in hepatocytes.\",\n      \"evidence\": \"Deletion constructs in 3T3-L1/COS-1 cells with lipolysis readout; ChIP, EMSA, and reporter assays with SREBP-1c-null hepatocytes\",\n      \"pmids\": [\"20810722\", \"20575761\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether N- and C-terminal domains cooperate through dimerization was not established\", \"Relative importance of PPARs vs SREBP-1c in hepatic Cidea expression unclear\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"CIDEA was shown to function as a transcriptional coactivator: in mammary epithelial cells it translocates to the nucleus via a bipartite NLS, binds C/EBPβ, displaces HDAC1 from the Xdh promoter, and drives milk-lipid secretion — extending CIDEA's role beyond lipid-droplet biology to gene regulation.\",\n      \"evidence\": \"Co-IP of CIDEA–C/EBPβ, ChIP at Xdh promoter, Cidea-deficient mouse mammary glands, ectopic re-expression\",\n      \"pmids\": [\"22245780\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether nuclear coactivator function extends to other promoters beyond Xdh was unknown\", \"Whether nuclear translocation occurs in adipocytes was not tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"The biophysical mechanism of lipid droplet fusion was resolved: CIDEA forms trans-complexes at LD–LD contact sites through N-terminal and C-terminal dimerization, and an amphipathic helix embeds in the phospholipid monolayer where it binds phosphatidic acid to increase barrier permeability and enable lipid transfer.\",\n      \"evidence\": \"Amphipathic helix mutagenesis, PA-binding assay, reconstitution of LD–LD docking in brown adipocytes\",\n      \"pmids\": [\"26609809\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural model of the CIDEA trans-complex at atomic resolution lacking\", \"Regulation of PA availability at contact sites not addressed\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The long-standing question of how lipid-droplet-localized CIDEA inhibits mitochondrial UCP1 was partially resolved: overexpressed CIDEA suppresses UCP1 activity in isolated BAT mitochondria without changing UCP1 protein levels and without being mitochondrially localized, confirming an indirect inhibitory mechanism.\",\n      \"evidence\": \"UCP1 activity assay in isolated mitochondria from aP2-hCidea transgenic mice plus subcellular localization\",\n      \"pmids\": [\"27923808\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the intermediary signal between lipid droplets and mitochondria unknown\", \"Whether AMPK-β degradation accounts for UCP1 suppression not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Nuclear CIDEA function was extended to adipocyte thermogenesis: during britening of human adipocytes, CIDEA shuttles from lipid droplets to the nucleus in a concentration-dependent manner, where it inhibits LXRα-mediated repression and strengthens PPARγ binding at the UCP1 enhancer to drive UCP1 transcription.\",\n      \"evidence\": \"CRISPR knockout in primary human adipocytes with rescue, UCP1 enhancer reporter, nuclear fractionation, chromatin binding assays\",\n      \"pmids\": [\"31563853\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CIDEA concentration sensing triggers nuclear import is unknown\", \"Whether LXRα inhibition and PPARγ enhancement are direct or indirect remains incompletely defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Hepatic Cidea expression was found to be rhythmically repressed by Egr-1 and regulated by DNMT3B-mediated promoter methylation controlling SREBP-1c access, adding circadian and epigenetic layers to the transcriptional regulation of Cidea in liver lipid metabolism.\",\n      \"evidence\": \"Egr-1 knockout mice with circadian profiling; DNMT3B overexpression/knockdown with bisulfite sequencing and ChIP in hepatocytes\",\n      \"pmids\": [\"36964140\", \"37703946\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether Egr-1 directly binds the Cidea promoter or acts indirectly not fully established\", \"Interaction between circadian and epigenetic regulatory layers not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular intermediary by which lipid-droplet-localized CIDEA indirectly suppresses mitochondrial UCP1 activity remains unidentified, and the E3 ligase(s) mediating CIDEA ubiquitination at K23 have not been determined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No candidate E3 ligase for CIDEA ubiquitination identified\", \"Indirect mechanism of UCP1 suppression entirely unresolved\", \"High-resolution structure of full-length CIDEA or the LD fusion trans-complex not available\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [16, 22]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [19]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 6, 21]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [5, 10, 19]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [16, 22, 14]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [5, 10, 11, 17, 19]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 12]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [16, 22]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PRKAB1\",\n      \"CEBPB\",\n      \"NR1H3\",\n      \"PPARG\",\n      \"DFF45\",\n      \"PLIN1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}