{"gene":"PEMT","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2005,"finding":"The V175M substitution in human PEMT (exon 8 SNP) is a loss-of-function mutation, as demonstrated by transient transfection of McArdle-RH7777 cells with wild-type versus V175M mutant PEMT constructs, showing diminished enzymatic activity.","method":"Transient transfection of hepatoma cells with wild-type vs. V175M mutant PEMT constructs; enzymatic activity assay","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional assay in cell-based system with mutant vs. wild-type comparison, single lab, single method","pmids":["16051693"],"is_preprint":false},{"year":2003,"finding":"PEMT (encoded by Pemt-2) is the sole de novo choline-synthesizing enzyme in the liver; Pemt-/- mice fed any level of dietary choline develop hepatic steatosis, elevated apoptosis (TUNEL-positive cells), and reduced phosphatidylcholine concentrations, demonstrating that PEMT activity is required for normal hepatic phospholipid homeostasis and is not fully compensable by dietary choline.","method":"Pemt-/- knockout mouse model with dietary choline manipulation; liver histology, TUNEL assay, choline metabolite quantification","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with multiple dietary conditions and multiple orthogonal phenotypic readouts, consistent with independent replication across studies","pmids":["12466019"],"is_preprint":false},{"year":2010,"finding":"Estrogen regulates PEMT in an isoform-specific fashion; chromatin immunoprecipitation identified estrogen receptor binding regions in the PEMT locus, and the risk SNP rs12325817 (located within 1 kb of the critical estrogen response element) abrogates binding of both the estrogen receptor and the pioneer factor FOXA1, preventing hormone-inducible PEMT expression.","method":"Transcript-specific gene expression analysis, locus-wide SNP analysis, chromatin immunoprecipitation with locus-wide microarray (ChIP-chip)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (ChIP, expression analysis, SNP-phenotype association), mechanistically defined regulatory element","pmids":["21059658"],"is_preprint":false},{"year":2002,"finding":"Liver damage caused by PEMT deficiency combined with choline-deficient diet is rapidly reversible upon choline supplementation, demonstrating that PEMT's essential role is to supply choline/phosphatidylcholine for hepatocyte survival.","method":"Pemt-/- mouse dietary rescue experiment; plasma aminotransferase assays, hepatic PC and triacylglycerol measurement","journal":"The Journal of nutrition","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic KO with dietary intervention and biochemical readouts, single lab","pmids":["11773510"],"is_preprint":false},{"year":2019,"finding":"Protection against diet-induced obesity and insulin resistance in Pemt-/- mice is specifically dependent on hepatic PEMT activity (not extrahepatically expressed PEMT); restoration of hepatic PEMT via adeno-associated virus in Pemt-/- mice reversed protection against obesity and insulin resistance, while AAV-mediated restoration also worsened the PC:PE ratio and NAFLD, demonstrating that hepatic PEMT is the critical site of action.","method":"Adeno-associated virus-mediated hepatic PEMT restoration in Pemt-/- mice; antisense oligonucleotide knockdown of hepatic PEMT in wild-type and ob/ob mice; measurement of weight gain, insulin sensitivity, liver function, and hepatic PC:PE ratio","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific rescue and knockdown with multiple metabolic readouts, orthogonal gain- and loss-of-function approaches in single study","pmids":["31284753"],"is_preprint":false},{"year":2000,"finding":"PEMT2 protein and mRNA are lost in pre-neoplastic nodules and hepatocellular carcinoma induced by aflatoxin B1 without gene deletion or mutation, indicating transcriptional downregulation. Re-expression of PEMT2 in McArdle hepatoma cells inhibited anchorage-independent colony formation and reduced tumorigenicity in athymic mice, demonstrating a tumor-suppressive function.","method":"Western blot, RT-PCR, Southern blot in rat liver carcinogenesis model; transfection of PEMT2 into McArdle hepatoma cells; soft-agar colony assay; xenograft tumorigenicity assay in athymic mice","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (in vitro and in vivo loss/gain of function), single lab","pmids":["10760824"],"is_preprint":false},{"year":2002,"finding":"Overexpression of PEMT2 in rat hepatoma CBRH-7919 cells downregulates multiple components of the PI3K/Akt signaling pathway (c-Met, PDGF receptor, PI3K, Akt, Bcl-2) and induces apoptosis, linking PEMT2-mediated phospholipid changes to suppression of a major cell-survival pathway.","method":"Stable transfection of PEMT2 cDNA into hepatoma cells; Western blotting for PI3K/Akt pathway proteins; flow cytometry and DNA ladder apoptosis assays; pharmacological inhibitors (wortmannin, PD98059)","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical readouts with pharmacological validation, single lab","pmids":["11960751"],"is_preprint":false},{"year":2009,"finding":"PEMT2-overexpressing hepatoma cells produce phosphatidylcholine enriched in oleic acid that localizes mainly to mitochondria; PEMT2 overexpression increases mitochondrial membrane fluidity, triggers cytochrome C release, and activates caspase-9 and caspase-3, establishing a mitochondrial (intrinsic) apoptotic pathway downstream of PEMT2 activity.","method":"Stable PEMT2 transfection in CBRH-7919 cells; lipid extraction with HPTLC and GC; [3H]-ethanolamine tracing; Western blot for cytochrome C and caspase activation; membrane fluidity measurement","journal":"IUBMB life","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (lipid tracing, fractionation, Western blot), single lab","pmids":["19517528"],"is_preprint":false},{"year":2004,"finding":"Deletion of Pemt results in increased S-adenosylmethionine levels and elevated DNA and protein methylation in fetal hippocampus, accompanied by increased neural progenitor cell mitosis and decreased GABAergic neuronal differentiation (calretinin expression), placing PEMT in a pathway regulating hippocampal development through methylation substrate availability.","method":"Pemt-/- knockout mouse; phosphorylated histone H3 immunostaining (mitosis marker); calretinin immunostaining; SAM quantification; DNA and protein methylation assays in embryonic day 17 hippocampus","journal":"Brain research. Developmental brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with multiple biochemical and histological readouts, single lab","pmids":["15063092"],"is_preprint":false},{"year":2009,"finding":"Pemt-/- fetal brains have 25-50% less phospholipid-DHA compared to wild-type; dietary DHA supplementation to pregnant Pemt-/- dams restores fetal brain phospholipid-DHA to wild-type levels and abrogates abnormal neural progenitor proliferation and apoptosis, demonstrating that PEMT's role in fetal hippocampal development is mediated through DHA incorporation into membrane phospholipids.","method":"Pemt-/- knockout mouse with dietary DHA supplementation; phospholipid-DHA quantification; BrdU/Ki67 proliferation assay; TUNEL apoptosis assay; calretinin immunostaining in E17 hippocampus","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic rescue with dietary intervention and multiple cellular readouts, single lab","pmids":["19889625"],"is_preprint":false},{"year":2014,"finding":"PEMT promoter methylation at the -132 site in BRCA1-mutated breast cancer leads to loss of active histone mark H3K9ac and gain of repressive mark H3K9me3, synergistically inhibiting PEMT transcription; this identifies DNA methylation and histone modification as cooperating epigenetic regulators of PEMT expression.","method":"Bisulfite sequencing; chromatin immunoprecipitation for H3K9ac and H3K9me3; transcript-specific expression analysis in breast cancer specimens","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal epigenetic methods, single lab","pmids":["24675476"],"is_preprint":false},{"year":2014,"finding":"PEMT deficiency in mice ameliorates ER stress in diabetic nephropathy; in renal proximal tubular cells, shRNA-mediated Pemt knockdown reduced GRP78 expression (ER stress marker), increased Akt phosphorylation, and decreased cleavage of caspase-3 and caspase-7, demonstrating that PEMT activity promotes ER stress-induced apoptosis in diabetic kidney disease.","method":"Streptozotocin-induced diabetic Pemt-/- mice; shRNA lentivirus knockdown in mProx24 cells; ER stress induction with tunicamycin/thapsigargin; Western blot for GRP78, p-Akt, caspase-3/-7; histology for glomerular hypertrophy, fibrosis, macrophage infiltration","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO and in vitro shRNA knockdown with mechanistic signaling readouts, single lab","pmids":["24667182"],"is_preprint":false},{"year":2005,"finding":"Mdr2+/- mice (which secrete 40% less phosphatidylcholine) show significantly lower PEMT activity and higher SAM:SAH ratios compared to Mdr2+/+ mice on a methionine- and choline-deficient diet, and are protected from diet-induced steatohepatitis, placing PEMT activity downstream of hepatic phosphatidylcholine demand and upstream of NASH pathogenesis.","method":"Mdr2+/- mice fed methionine-choline-deficient diet; PEMT activity assay; SAM/SAH quantification; serum ALT; liver histology","journal":"Journal of hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic mouse model with biochemical and histological readouts establishing pathway position, single lab","pmids":["16376450"],"is_preprint":false},{"year":2017,"finding":"Hepatic PEMT protein levels and activity are increased at gestational day 15 and 20 in pregnant rats, coinciding with increased plasma 16:0/DHA-phosphatidylcholine, identifying PEMT as the mechanism for the pregnancy-associated rise in circulating DHA-enriched PC.","method":"Rat pregnancy time-course study; PEMT activity assay; Western blot for PEMT protein; fatty acid profiling by GC; lipidomics for DHA-PC species","journal":"Journal of lipid research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct enzyme activity and protein level measurement combined with lipidomic profiling at multiple time points, single lab","pmids":["29167412"],"is_preprint":false},{"year":2019,"finding":"Global Pemt-/- mice completely lack UCP1 protein in brown adipose tissue (BAT) without changes in UCP1 mRNA, due to an untranslated UCP1 splice variant induced perinatally; this effect is non-cell-autonomous — BAT-specific, adipose-specific, liver-specific, and muscle-specific PEMT knockouts all maintain normal UCP1 protein levels — demonstrating that PEMT in non-adipocyte cells communicates to BAT to regulate UCP1 splicing during embryonic development.","method":"Multiple conditional PEMT knockout mouse models (BAT-specific, adipose-specific, liver-specific, muscle-specific); Western blot for UCP1 protein; RT-PCR for UCP1 mRNA and splice variants; cold tolerance testing","journal":"Molecular metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple tissue-specific conditional KO models with Western blot and RT-PCR, non-cell-autonomous mechanism established by systematic exclusion across tissue types in a single rigorous study","pmids":["31918922"],"is_preprint":false},{"year":2015,"finding":"High-fat diet-fed Pemt-/- mice develop hypothermia on cold exposure due to plasma hypoglycemia caused by compromised hepatic gluconeogenesis; choline supplementation normalizes plasma glucose, gluconeogenic protein expression, and cold tolerance, establishing a mechanistic link between PEMT activity, hepatic phospholipid balance, and gluconeogenesis.","method":"HF diet-fed Pemt-/- mice; acute cold exposure (4°C); plasma glucose and catecholamine measurement; lipolysis assay; Western blot for gluconeogenic proteins; choline supplementation rescue","journal":"Journal of lipid research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with dietary rescue and multiple metabolic readouts, single lab","pmids":["26113536"],"is_preprint":false},{"year":2018,"finding":"Hepatic PEMT expression (restored via AAV in Pemt-/-/Ldlr-/- mice) increases plasma cholesterol and trimethylamine-N-oxide (TMAO) and reverses protection against atherosclerosis, demonstrating that hepatic PEMT-derived choline is the source of substrate for gut microbiota-dependent TMAO production and that PEMT is a mechanistic link between de novo choline synthesis and atherosclerosis risk.","method":"AAV-mediated hepatic PEMT restoration in Pemt-/-/Ldlr-/- mice; plasma lipid and TMAO quantification; aortic lesion quantification; choline supplementation comparison","journal":"The Journal of nutrition","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific gain-of-function (AAV) with mechanistic metabolite and atherosclerosis readouts, single lab","pmids":["30281112"],"is_preprint":false},{"year":2006,"finding":"PEMT2 overexpression in rat hepatoma cells inhibits phosphorylation and membrane translocation of PLCγ1 and reduces autophosphorylation of c-Met, indicating that PEMT2-induced changes in membrane phospholipid composition downregulate the c-Met/PLCγ1 signaling pathway.","method":"PEMT2 stable transfection in CBRH-7919 cells; Western blot for PLCγ1 phosphorylation and subcellular fractionation; Western blot for phospho-c-Met","journal":"Zhonghua gan zang bing za zhi","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, Western blot only, limited mechanistic follow-up, published in lower-tier journal","pmids":["16867273"],"is_preprint":false},{"year":2005,"finding":"PEMT2 overexpression in CBRH-7919 hepatoma cells inhibits cPKCα expression while increasing cPKCβ2 expression and its translocation from cytosol to plasma membrane, and decreases diacylglycerol (DAG) content, linking PEMT2-mediated phospholipid metabolism to differential regulation of PKC isoforms.","method":"PEMT2 stable transfection; immunocytochemistry and Western blot for PKC isoforms; HPTLC for DAG quantification","journal":"Zhonghua gan zang bing za zhi","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, limited methods, lower-tier publication","pmids":["16174458"],"is_preprint":false},{"year":2023,"finding":"HCV infection induces PEMT expression and uses the PEMT-mediated non-canonical phosphatidylcholine synthesis pathway to increase phosphatidylcholine in the endoplasmic reticulum; siRNA knockdown of PEMT inhibits HCV replication and reverses virus-induced lipogenic gene expression changes (SREBP1c, DGAT1 upregulation; MTP downregulation), establishing PEMT as necessary for HCV-induced steatosis and virus replication.","method":"HCV cell culture model; quantitative lipidomics (HPTLC/MS); siRNA knockdown of PEMT; Western blot for PEMT and lipogenic genes; qRT-PCR; analysis of liver biopsies from HCV genotype 1 vs. 3 patients","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA knockdown with mechanistic lipid and viral replication readouts plus patient tissue validation, single lab","pmids":["37240132"],"is_preprint":false},{"year":2025,"finding":"PEMT physically interacts with SHMT1 in astrocytes; disruption of this interaction depletes SAM, causing H3K4me1 hypomethylation and reduced expression of Slc1a2 and Glul, ultimately exacerbating neuroexcitotoxicity and dopaminergic neuronal loss in a Parkinson's disease model.","method":"Astrocyte-specific conditional Shmt1 knockout; 13C-serine isotopic labeling; co-immunoprecipitation of SHMT1 and PEMT; ChIP for H3K4me1; gene expression analysis; PD mouse model behavioral and histological assessment","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP demonstrating physical interaction, isotopic labeling, and genetic KO with mechanistic downstream readouts; single lab","pmids":["41262011"],"is_preprint":false},{"year":2025,"finding":"Aging-driven PEMT overexpression (~2.4-fold at protein level in 24-month vs. 6-month mice) promotes hepatic phospholipid imbalance (increased PC/PE ratio ~2.5-fold); PEMT inhibition in D-galactose-induced senescent AML12 hepatocytes reduces lipid droplet accumulation by ~30% and intracellular triglycerides by ~20% under lipid stress, mechanistically linking elevated PEMT activity to age-associated hepatic steatosis.","method":"Natural aging mouse model (2-24 months); lipidomics; Western blot for PEMT protein; siRNA PEMT inhibition in senescent AML12 hepatocytes; lipid droplet quantification; intracellular TG measurement","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — combined in vivo aging model with in vitro loss-of-function and lipidomic readouts, single lab","pmids":["41311052"],"is_preprint":false}],"current_model":"PEMT is a liver-enriched enzyme that catalyzes the sequential methylation of phosphatidylethanolamine to phosphatidylcholine, representing the sole de novo choline-synthesizing pathway; hepatic PEMT activity maintains PC:PE balance critical for VLDL secretion, ER homeostasis, and liver health, is transcriptionally regulated by estrogen (via a specific estrogen response element bound by ERα and FOXA1), physically interacts with SHMT1 to couple one-carbon metabolism to phospholipid synthesis, and exerts non-cell-autonomous effects on UCP1 splicing in brown adipose tissue, while loss-of-function mutations (V175M) or epigenetic silencing reduce PC biosynthesis and promote steatosis, and overexpression triggers tumor-suppressive apoptosis via PI3K/Akt downregulation and the mitochondrial caspase cascade."},"narrative":{"mechanistic_narrative":"PEMT is a liver-enriched enzyme that constitutes the sole de novo choline-synthesizing pathway, catalyzing the conversion of phosphatidylethanolamine to phosphatidylcholine and thereby maintaining hepatic phospholipid homeostasis; its loss causes hepatic steatosis, reduced phosphatidylcholine, and elevated apoptosis that is rapidly reversible by dietary choline [PMID:12466019, PMID:11773510]. A loss-of-function V175M variant diminishes catalytic activity, linking sequence variation to reduced PC biosynthesis [PMID:16051693]. PEMT expression is hormonally controlled through an estrogen response element bound cooperatively by the estrogen receptor and the pioneer factor FOXA1, and a risk SNP near this element abrogates both factor binding and hormone-inducible expression [PMID:21059658]; expression is further silenced epigenetically through promoter DNA methylation coupled to loss of H3K9ac and gain of H3K9me3 [PMID:24675476]. Hepatic PEMT, rather than extrahepatic PEMT, is the critical site governing PC:PE ratio, susceptibility to diet-induced obesity, insulin resistance, and NAFLD [PMID:31284753], and PEMT-derived choline supplies substrate for gut microbiota-dependent TMAO production that promotes atherosclerosis [PMID:30281112]. Beyond bulk PC synthesis, PEMT generates DHA- and oleate-enriched PC species that support fetal brain development and circulating DHA delivery [PMID:19889625, PMID:29167412], and it couples to one-carbon metabolism by physically interacting with SHMT1 to sustain SAM-dependent histone methylation, with disruption depleting SAM and altering gene expression [PMID:41262011]. PEMT also exerts a tumor-suppressive function in hepatoma, where re-expression inhibits anchorage-independent growth and tumorigenicity and triggers intrinsic mitochondrial apoptosis with downregulation of PI3K/Akt survival signaling [PMID:10760824, PMID:11960751, PMID:19517528], and it acts non-cell-autonomously to control UCP1 splicing in brown adipose tissue during development [PMID:31918922].","teleology":[{"year":2002,"claim":"Established that PEMT's essential hepatic role is to supply choline/phosphatidylcholine required for hepatocyte survival, resolving whether dietary choline could substitute for endogenous synthesis.","evidence":"Pemt-/- mouse dietary rescue with choline supplementation, plasma aminotransferase and hepatic PC/TAG readouts","pmids":["11773510"],"confidence":"Medium","gaps":["Does not define the molecular trigger linking PC deficiency to hepatocyte death","Single lab"]},{"year":2003,"claim":"Defined PEMT as the sole de novo choline-synthesizing enzyme in liver and showed its loss is not fully compensable by dietary choline, anchoring its role in phospholipid homeostasis.","evidence":"Pemt-/- knockout mice across dietary choline levels; histology, TUNEL, metabolite quantification","pmids":["12466019"],"confidence":"High","gaps":["Does not address tissue-specific contributions of hepatic vs extrahepatic PEMT","Does not establish the apoptotic pathway"]},{"year":2005,"claim":"Connected a human coding variant (V175M) to reduced enzyme activity, providing a genetic basis for impaired PC biosynthesis.","evidence":"Transient transfection of wild-type vs V175M PEMT in hepatoma cells with activity assay","pmids":["16051693"],"confidence":"Medium","gaps":["No in vivo phenotype tied to the variant","Single method, single lab"]},{"year":2005,"claim":"Positioned PEMT activity downstream of hepatic PC demand and upstream of steatohepatitis pathogenesis.","evidence":"Mdr2+/- mice on methionine-choline-deficient diet; PEMT activity, SAM:SAH, ALT, histology","pmids":["16376450"],"confidence":"Medium","gaps":["Correlative pathway position rather than direct causal manipulation of PEMT","Single lab"]},{"year":2000,"claim":"Revealed a tumor-suppressive function for PEMT through transcriptional loss in carcinogenesis and growth suppression on re-expression.","evidence":"Aflatoxin B1 rat carcinogenesis model; PEMT2 re-expression with soft-agar and xenograft assays","pmids":["10760824"],"confidence":"Medium","gaps":["Does not define the downstream effector of tumor suppression","Single lab"]},{"year":2009,"claim":"Mechanistically linked PEMT2-driven phospholipid changes to intrinsic mitochondrial apoptosis, building on the earlier PI3K/Akt downregulation finding.","evidence":"PEMT2 stable transfection; lipid tracing, mitochondrial fractionation, cytochrome C release, caspase-9/-3 activation; membrane fluidity","pmids":["19517528","11960751"],"confidence":"Medium","gaps":["Causal chain from oleate-enriched PC to caspase activation not fully resolved","Single lab cell-line context"]},{"year":2010,"claim":"Identified the transcriptional control of PEMT by estrogen via an ERα/FOXA1-bound response element, explaining hormone- and SNP-dependent variation in PEMT expression.","evidence":"Transcript-specific expression analysis, SNP analysis, ChIP-chip for ER and FOXA1 binding","pmids":["21059658"],"confidence":"High","gaps":["Does not address non-estrogen transcriptional inputs","Functional consequence of the SNP in human liver not quantified here"]},{"year":2014,"claim":"Showed epigenetic silencing of PEMT via cooperating DNA methylation and histone marks, providing a non-genetic route to PEMT loss in cancer.","evidence":"Bisulfite sequencing and ChIP for H3K9ac/H3K9me3 in BRCA1-mutated breast cancer specimens","pmids":["24675476"],"confidence":"Medium","gaps":["Correlative in patient tissue without manipulation of the marks","Single lab"]},{"year":2014,"claim":"Demonstrated that PEMT activity promotes ER stress-induced apoptosis in diabetic kidney disease, extending its pro-apoptotic role to a non-hepatic tissue.","evidence":"STZ-diabetic Pemt-/- mice and shRNA knockdown in renal tubular cells; GRP78, p-Akt, caspase readouts","pmids":["24667182"],"confidence":"Medium","gaps":["Mechanism connecting PEMT-derived PC to ER stress not defined","Single lab"]},{"year":2009,"claim":"Established that PEMT supports fetal hippocampal development through incorporation of DHA into membrane phospholipids and modulation of SAM-dependent methylation.","evidence":"Pemt-/- mice with dietary DHA rescue; phospholipid-DHA, proliferation, TUNEL, calretinin readouts; earlier SAM/methylation analysis","pmids":["19889625","15063092"],"confidence":"Medium","gaps":["Relative contributions of DHA delivery vs methylation substrate not separated","Single lab"]},{"year":2017,"claim":"Identified PEMT as the mechanism for the pregnancy-associated rise in circulating DHA-enriched PC.","evidence":"Rat pregnancy time-course; PEMT activity and protein, lipidomics for DHA-PC species","pmids":["29167412"],"confidence":"Medium","gaps":["Upstream signal driving gestational PEMT induction unknown","Single lab"]},{"year":2018,"claim":"Defined hepatic PEMT-derived choline as the substrate source for gut microbiota-dependent TMAO production and a mechanistic link to atherosclerosis.","evidence":"AAV hepatic PEMT restoration in Pemt-/-/Ldlr-/- mice; plasma lipids, TMAO, aortic lesion quantification","pmids":["30281112"],"confidence":"Medium","gaps":["Microbial steps converting choline to TMAO not characterized here","Single lab"]},{"year":2019,"claim":"Resolved that hepatic, not extrahepatic, PEMT is the critical determinant of PC:PE ratio, NAFLD, and metabolic protection through orthogonal gain- and loss-of-function.","evidence":"AAV hepatic restoration and ASO knockdown in Pemt-/- and ob/ob mice with metabolic and lipid readouts","pmids":["31284753"],"confidence":"High","gaps":["Does not define the molecular sensor of PC:PE imbalance","Tissue communication mechanisms not addressed"]},{"year":2019,"claim":"Uncovered a non-cell-autonomous role for PEMT in controlling perinatal UCP1 splicing in brown adipose tissue.","evidence":"Multiple tissue-specific conditional Pemt knockouts; UCP1 protein and splice-variant mRNA, cold tolerance","pmids":["31918922"],"confidence":"High","gaps":["Identity of the intercellular signal from non-adipocytes to BAT unknown","Splicing regulator linking PEMT to UCP1 unidentified"]},{"year":2015,"claim":"Linked PEMT-dependent hepatic phospholipid balance to gluconeogenesis and systemic thermoregulation.","evidence":"HF-diet Pemt-/- mice with cold exposure and choline rescue; plasma glucose, gluconeogenic protein expression","pmids":["26113536"],"confidence":"Medium","gaps":["Molecular coupling of PC balance to gluconeogenic gene expression unresolved","Single lab"]},{"year":2023,"claim":"Showed that HCV co-opts PEMT-mediated non-canonical PC synthesis to drive ER PC accumulation, lipogenesis, and viral replication.","evidence":"HCV cell culture, lipidomics, siRNA PEMT knockdown, lipogenic gene profiling, patient biopsy analysis","pmids":["37240132"],"confidence":"Medium","gaps":["How HCV induces PEMT transcription not defined","Single lab"]},{"year":2025,"claim":"Established a physical interaction between PEMT and SHMT1 that couples phospholipid synthesis to one-carbon/SAM availability and histone methylation in astrocytes.","evidence":"Co-immunoprecipitation of PEMT and SHMT1, 13C-serine labeling, ChIP for H3K4me1, astrocyte Shmt1 KO in a PD model","pmids":["41262011"],"confidence":"Medium","gaps":["Single Co-IP without reciprocal structural mapping of the interaction","Direction of metabolic coupling between the two enzymes not fully resolved"]},{"year":2025,"claim":"Connected aging-driven PEMT overexpression to hepatic PC/PE imbalance and steatosis, indicating excess PEMT activity is also pathogenic.","evidence":"Natural aging mouse lipidomics, PEMT Western blot, siRNA inhibition in senescent AML12 hepatocytes","pmids":["41311052"],"confidence":"Medium","gaps":["Mechanism driving age-associated PEMT induction unknown","Single lab"]},{"year":null,"claim":"The identity of the intercellular signal by which non-adipocyte PEMT controls UCP1 splicing, and the structural/regulatory basis of the PEMT-SHMT1 metabolic coupling, remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No identified mediator of PEMT's non-cell-autonomous effect on BAT","No structural model of the PEMT-SHMT1 complex","Molecular sensor of PC:PE imbalance unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,12,13]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[20]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[19]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,4,16,21]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[5,6,7,11]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[2,10]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[8,20]}],"complexes":[],"partners":["SHMT1","ESR1","FOXA1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UBM1","full_name":"Phosphatidylethanolamine N-methyltransferase","aliases":["PEMT2","Phospholipid methyltransferase","PLMT"],"length_aa":199,"mass_kda":22.1,"function":"Catalyzes the three sequential steps of the methylation pathway for the biosynthesis of phosphatidylcholine, a critical and essential component for membrane structure (PubMed:12431977, PubMed:15927961). Uses S-adenosylmethionine (S-adenosyl-L-methionine, SAM or AdoMet) as the methyl group donor for the methylation of phosphatidylethanolamine (1,2-diacyl-sn-glycero-3-phosphoethanolamine, PE) to phosphatidylmonomethylethanolamine (1,2-diacyl-sn-glycero-3-phospho-N-methylethanolamine, PMME), PMME to phosphatidyldimethylethanolamine (1,2-diacyl-sn-glycero-3-phospho-N,N-dimethylethanolamine, PDME), and PDME to phosphatidylcholine (1,2-diacyl-sn-glycero-3-phosphocholine, PC), producing S-adenosyl-L-homocysteine in each step (PubMed:12431977, PubMed:15927961). Responsible for approximately 30% of hepatic PC with the CDP-choline pathway accounting for the other 70% (Probable) Catalyzes the three sequential steps of the methylation of 1,2-diacyl-sn-glycero-3-phospho-N-methylethanolamine (PMME) to 1,2-diacyl-sn-glycero-3-phospho-N,N-dimethylethanolamine (PDME) more efficiently than isoform 2 (PubMed:20860552). Induces increase in PC species with longer polyunsaturated chains than isoform 2 (PubMed:20860552) Produces a higher increase in the level of PC species containing long chains with three double bonds than isoform 1","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/Q9UBM1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PEMT","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PEMT","total_profiled":1310},"omim":[{"mim_id":"604031","title":"STEAROYL-CoA DESATURASE; SCD","url":"https://www.omim.org/entry/604031"},{"mim_id":"602391","title":"PHOSPHATIDYLETHANOLAMINE N-METHYLTRANSFERASE; PEMT","url":"https://www.omim.org/entry/602391"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Endoplasmic reticulum","reliability":"Supported"},{"location":"Mitochondria","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in 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V175M mutant PEMT constructs; enzymatic activity assay\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional assay in cell-based system with mutant vs. wild-type comparison, single lab, single method\",\n      \"pmids\": [\"16051693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PEMT (encoded by Pemt-2) is the sole de novo choline-synthesizing enzyme in the liver; Pemt-/- mice fed any level of dietary choline develop hepatic steatosis, elevated apoptosis (TUNEL-positive cells), and reduced phosphatidylcholine concentrations, demonstrating that PEMT activity is required for normal hepatic phospholipid homeostasis and is not fully compensable by dietary choline.\",\n      \"method\": \"Pemt-/- knockout mouse model with dietary choline manipulation; liver histology, TUNEL assay, choline metabolite quantification\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with multiple dietary conditions and multiple orthogonal phenotypic readouts, consistent with independent replication across studies\",\n      \"pmids\": [\"12466019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Estrogen regulates PEMT in an isoform-specific fashion; chromatin immunoprecipitation identified estrogen receptor binding regions in the PEMT locus, and the risk SNP rs12325817 (located within 1 kb of the critical estrogen response element) abrogates binding of both the estrogen receptor and the pioneer factor FOXA1, preventing hormone-inducible PEMT expression.\",\n      \"method\": \"Transcript-specific gene expression analysis, locus-wide SNP analysis, chromatin immunoprecipitation with locus-wide microarray (ChIP-chip)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (ChIP, expression analysis, SNP-phenotype association), mechanistically defined regulatory element\",\n      \"pmids\": [\"21059658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Liver damage caused by PEMT deficiency combined with choline-deficient diet is rapidly reversible upon choline supplementation, demonstrating that PEMT's essential role is to supply choline/phosphatidylcholine for hepatocyte survival.\",\n      \"method\": \"Pemt-/- mouse dietary rescue experiment; plasma aminotransferase assays, hepatic PC and triacylglycerol measurement\",\n      \"journal\": \"The Journal of nutrition\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic KO with dietary intervention and biochemical readouts, single lab\",\n      \"pmids\": [\"11773510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Protection against diet-induced obesity and insulin resistance in Pemt-/- mice is specifically dependent on hepatic PEMT activity (not extrahepatically expressed PEMT); restoration of hepatic PEMT via adeno-associated virus in Pemt-/- mice reversed protection against obesity and insulin resistance, while AAV-mediated restoration also worsened the PC:PE ratio and NAFLD, demonstrating that hepatic PEMT is the critical site of action.\",\n      \"method\": \"Adeno-associated virus-mediated hepatic PEMT restoration in Pemt-/- mice; antisense oligonucleotide knockdown of hepatic PEMT in wild-type and ob/ob mice; measurement of weight gain, insulin sensitivity, liver function, and hepatic PC:PE ratio\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific rescue and knockdown with multiple metabolic readouts, orthogonal gain- and loss-of-function approaches in single study\",\n      \"pmids\": [\"31284753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"PEMT2 protein and mRNA are lost in pre-neoplastic nodules and hepatocellular carcinoma induced by aflatoxin B1 without gene deletion or mutation, indicating transcriptional downregulation. Re-expression of PEMT2 in McArdle hepatoma cells inhibited anchorage-independent colony formation and reduced tumorigenicity in athymic mice, demonstrating a tumor-suppressive function.\",\n      \"method\": \"Western blot, RT-PCR, Southern blot in rat liver carcinogenesis model; transfection of PEMT2 into McArdle hepatoma cells; soft-agar colony assay; xenograft tumorigenicity assay in athymic mice\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (in vitro and in vivo loss/gain of function), single lab\",\n      \"pmids\": [\"10760824\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Overexpression of PEMT2 in rat hepatoma CBRH-7919 cells downregulates multiple components of the PI3K/Akt signaling pathway (c-Met, PDGF receptor, PI3K, Akt, Bcl-2) and induces apoptosis, linking PEMT2-mediated phospholipid changes to suppression of a major cell-survival pathway.\",\n      \"method\": \"Stable transfection of PEMT2 cDNA into hepatoma cells; Western blotting for PI3K/Akt pathway proteins; flow cytometry and DNA ladder apoptosis assays; pharmacological inhibitors (wortmannin, PD98059)\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical readouts with pharmacological validation, single lab\",\n      \"pmids\": [\"11960751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PEMT2-overexpressing hepatoma cells produce phosphatidylcholine enriched in oleic acid that localizes mainly to mitochondria; PEMT2 overexpression increases mitochondrial membrane fluidity, triggers cytochrome C release, and activates caspase-9 and caspase-3, establishing a mitochondrial (intrinsic) apoptotic pathway downstream of PEMT2 activity.\",\n      \"method\": \"Stable PEMT2 transfection in CBRH-7919 cells; lipid extraction with HPTLC and GC; [3H]-ethanolamine tracing; Western blot for cytochrome C and caspase activation; membrane fluidity measurement\",\n      \"journal\": \"IUBMB life\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (lipid tracing, fractionation, Western blot), single lab\",\n      \"pmids\": [\"19517528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Deletion of Pemt results in increased S-adenosylmethionine levels and elevated DNA and protein methylation in fetal hippocampus, accompanied by increased neural progenitor cell mitosis and decreased GABAergic neuronal differentiation (calretinin expression), placing PEMT in a pathway regulating hippocampal development through methylation substrate availability.\",\n      \"method\": \"Pemt-/- knockout mouse; phosphorylated histone H3 immunostaining (mitosis marker); calretinin immunostaining; SAM quantification; DNA and protein methylation assays in embryonic day 17 hippocampus\",\n      \"journal\": \"Brain research. Developmental brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with multiple biochemical and histological readouts, single lab\",\n      \"pmids\": [\"15063092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Pemt-/- fetal brains have 25-50% less phospholipid-DHA compared to wild-type; dietary DHA supplementation to pregnant Pemt-/- dams restores fetal brain phospholipid-DHA to wild-type levels and abrogates abnormal neural progenitor proliferation and apoptosis, demonstrating that PEMT's role in fetal hippocampal development is mediated through DHA incorporation into membrane phospholipids.\",\n      \"method\": \"Pemt-/- knockout mouse with dietary DHA supplementation; phospholipid-DHA quantification; BrdU/Ki67 proliferation assay; TUNEL apoptosis assay; calretinin immunostaining in E17 hippocampus\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic rescue with dietary intervention and multiple cellular readouts, single lab\",\n      \"pmids\": [\"19889625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PEMT promoter methylation at the -132 site in BRCA1-mutated breast cancer leads to loss of active histone mark H3K9ac and gain of repressive mark H3K9me3, synergistically inhibiting PEMT transcription; this identifies DNA methylation and histone modification as cooperating epigenetic regulators of PEMT expression.\",\n      \"method\": \"Bisulfite sequencing; chromatin immunoprecipitation for H3K9ac and H3K9me3; transcript-specific expression analysis in breast cancer specimens\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal epigenetic methods, single lab\",\n      \"pmids\": [\"24675476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PEMT deficiency in mice ameliorates ER stress in diabetic nephropathy; in renal proximal tubular cells, shRNA-mediated Pemt knockdown reduced GRP78 expression (ER stress marker), increased Akt phosphorylation, and decreased cleavage of caspase-3 and caspase-7, demonstrating that PEMT activity promotes ER stress-induced apoptosis in diabetic kidney disease.\",\n      \"method\": \"Streptozotocin-induced diabetic Pemt-/- mice; shRNA lentivirus knockdown in mProx24 cells; ER stress induction with tunicamycin/thapsigargin; Western blot for GRP78, p-Akt, caspase-3/-7; histology for glomerular hypertrophy, fibrosis, macrophage infiltration\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO and in vitro shRNA knockdown with mechanistic signaling readouts, single lab\",\n      \"pmids\": [\"24667182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Mdr2+/- mice (which secrete 40% less phosphatidylcholine) show significantly lower PEMT activity and higher SAM:SAH ratios compared to Mdr2+/+ mice on a methionine- and choline-deficient diet, and are protected from diet-induced steatohepatitis, placing PEMT activity downstream of hepatic phosphatidylcholine demand and upstream of NASH pathogenesis.\",\n      \"method\": \"Mdr2+/- mice fed methionine-choline-deficient diet; PEMT activity assay; SAM/SAH quantification; serum ALT; liver histology\",\n      \"journal\": \"Journal of hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic mouse model with biochemical and histological readouts establishing pathway position, single lab\",\n      \"pmids\": [\"16376450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Hepatic PEMT protein levels and activity are increased at gestational day 15 and 20 in pregnant rats, coinciding with increased plasma 16:0/DHA-phosphatidylcholine, identifying PEMT as the mechanism for the pregnancy-associated rise in circulating DHA-enriched PC.\",\n      \"method\": \"Rat pregnancy time-course study; PEMT activity assay; Western blot for PEMT protein; fatty acid profiling by GC; lipidomics for DHA-PC species\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct enzyme activity and protein level measurement combined with lipidomic profiling at multiple time points, single lab\",\n      \"pmids\": [\"29167412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Global Pemt-/- mice completely lack UCP1 protein in brown adipose tissue (BAT) without changes in UCP1 mRNA, due to an untranslated UCP1 splice variant induced perinatally; this effect is non-cell-autonomous — BAT-specific, adipose-specific, liver-specific, and muscle-specific PEMT knockouts all maintain normal UCP1 protein levels — demonstrating that PEMT in non-adipocyte cells communicates to BAT to regulate UCP1 splicing during embryonic development.\",\n      \"method\": \"Multiple conditional PEMT knockout mouse models (BAT-specific, adipose-specific, liver-specific, muscle-specific); Western blot for UCP1 protein; RT-PCR for UCP1 mRNA and splice variants; cold tolerance testing\",\n      \"journal\": \"Molecular metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple tissue-specific conditional KO models with Western blot and RT-PCR, non-cell-autonomous mechanism established by systematic exclusion across tissue types in a single rigorous study\",\n      \"pmids\": [\"31918922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"High-fat diet-fed Pemt-/- mice develop hypothermia on cold exposure due to plasma hypoglycemia caused by compromised hepatic gluconeogenesis; choline supplementation normalizes plasma glucose, gluconeogenic protein expression, and cold tolerance, establishing a mechanistic link between PEMT activity, hepatic phospholipid balance, and gluconeogenesis.\",\n      \"method\": \"HF diet-fed Pemt-/- mice; acute cold exposure (4°C); plasma glucose and catecholamine measurement; lipolysis assay; Western blot for gluconeogenic proteins; choline supplementation rescue\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with dietary rescue and multiple metabolic readouts, single lab\",\n      \"pmids\": [\"26113536\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Hepatic PEMT expression (restored via AAV in Pemt-/-/Ldlr-/- mice) increases plasma cholesterol and trimethylamine-N-oxide (TMAO) and reverses protection against atherosclerosis, demonstrating that hepatic PEMT-derived choline is the source of substrate for gut microbiota-dependent TMAO production and that PEMT is a mechanistic link between de novo choline synthesis and atherosclerosis risk.\",\n      \"method\": \"AAV-mediated hepatic PEMT restoration in Pemt-/-/Ldlr-/- mice; plasma lipid and TMAO quantification; aortic lesion quantification; choline supplementation comparison\",\n      \"journal\": \"The Journal of nutrition\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific gain-of-function (AAV) with mechanistic metabolite and atherosclerosis readouts, single lab\",\n      \"pmids\": [\"30281112\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PEMT2 overexpression in rat hepatoma cells inhibits phosphorylation and membrane translocation of PLCγ1 and reduces autophosphorylation of c-Met, indicating that PEMT2-induced changes in membrane phospholipid composition downregulate the c-Met/PLCγ1 signaling pathway.\",\n      \"method\": \"PEMT2 stable transfection in CBRH-7919 cells; Western blot for PLCγ1 phosphorylation and subcellular fractionation; Western blot for phospho-c-Met\",\n      \"journal\": \"Zhonghua gan zang bing za zhi\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, Western blot only, limited mechanistic follow-up, published in lower-tier journal\",\n      \"pmids\": [\"16867273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PEMT2 overexpression in CBRH-7919 hepatoma cells inhibits cPKCα expression while increasing cPKCβ2 expression and its translocation from cytosol to plasma membrane, and decreases diacylglycerol (DAG) content, linking PEMT2-mediated phospholipid metabolism to differential regulation of PKC isoforms.\",\n      \"method\": \"PEMT2 stable transfection; immunocytochemistry and Western blot for PKC isoforms; HPTLC for DAG quantification\",\n      \"journal\": \"Zhonghua gan zang bing za zhi\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, limited methods, lower-tier publication\",\n      \"pmids\": [\"16174458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HCV infection induces PEMT expression and uses the PEMT-mediated non-canonical phosphatidylcholine synthesis pathway to increase phosphatidylcholine in the endoplasmic reticulum; siRNA knockdown of PEMT inhibits HCV replication and reverses virus-induced lipogenic gene expression changes (SREBP1c, DGAT1 upregulation; MTP downregulation), establishing PEMT as necessary for HCV-induced steatosis and virus replication.\",\n      \"method\": \"HCV cell culture model; quantitative lipidomics (HPTLC/MS); siRNA knockdown of PEMT; Western blot for PEMT and lipogenic genes; qRT-PCR; analysis of liver biopsies from HCV genotype 1 vs. 3 patients\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA knockdown with mechanistic lipid and viral replication readouts plus patient tissue validation, single lab\",\n      \"pmids\": [\"37240132\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PEMT physically interacts with SHMT1 in astrocytes; disruption of this interaction depletes SAM, causing H3K4me1 hypomethylation and reduced expression of Slc1a2 and Glul, ultimately exacerbating neuroexcitotoxicity and dopaminergic neuronal loss in a Parkinson's disease model.\",\n      \"method\": \"Astrocyte-specific conditional Shmt1 knockout; 13C-serine isotopic labeling; co-immunoprecipitation of SHMT1 and PEMT; ChIP for H3K4me1; gene expression analysis; PD mouse model behavioral and histological assessment\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP demonstrating physical interaction, isotopic labeling, and genetic KO with mechanistic downstream readouts; single lab\",\n      \"pmids\": [\"41262011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Aging-driven PEMT overexpression (~2.4-fold at protein level in 24-month vs. 6-month mice) promotes hepatic phospholipid imbalance (increased PC/PE ratio ~2.5-fold); PEMT inhibition in D-galactose-induced senescent AML12 hepatocytes reduces lipid droplet accumulation by ~30% and intracellular triglycerides by ~20% under lipid stress, mechanistically linking elevated PEMT activity to age-associated hepatic steatosis.\",\n      \"method\": \"Natural aging mouse model (2-24 months); lipidomics; Western blot for PEMT protein; siRNA PEMT inhibition in senescent AML12 hepatocytes; lipid droplet quantification; intracellular TG measurement\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — combined in vivo aging model with in vitro loss-of-function and lipidomic readouts, single lab\",\n      \"pmids\": [\"41311052\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PEMT is a liver-enriched enzyme that catalyzes the sequential methylation of phosphatidylethanolamine to phosphatidylcholine, representing the sole de novo choline-synthesizing pathway; hepatic PEMT activity maintains PC:PE balance critical for VLDL secretion, ER homeostasis, and liver health, is transcriptionally regulated by estrogen (via a specific estrogen response element bound by ERα and FOXA1), physically interacts with SHMT1 to couple one-carbon metabolism to phospholipid synthesis, and exerts non-cell-autonomous effects on UCP1 splicing in brown adipose tissue, while loss-of-function mutations (V175M) or epigenetic silencing reduce PC biosynthesis and promote steatosis, and overexpression triggers tumor-suppressive apoptosis via PI3K/Akt downregulation and the mitochondrial caspase cascade.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PEMT is a liver-enriched enzyme that constitutes the sole de novo choline-synthesizing pathway, catalyzing the conversion of phosphatidylethanolamine to phosphatidylcholine and thereby maintaining hepatic phospholipid homeostasis; its loss causes hepatic steatosis, reduced phosphatidylcholine, and elevated apoptosis that is rapidly reversible by dietary choline [#1, #3]. A loss-of-function V175M variant diminishes catalytic activity, linking sequence variation to reduced PC biosynthesis [#0]. PEMT expression is hormonally controlled through an estrogen response element bound cooperatively by the estrogen receptor and the pioneer factor FOXA1, and a risk SNP near this element abrogates both factor binding and hormone-inducible expression [#2]; expression is further silenced epigenetically through promoter DNA methylation coupled to loss of H3K9ac and gain of H3K9me3 [#10]. Hepatic PEMT, rather than extrahepatic PEMT, is the critical site governing PC:PE ratio, susceptibility to diet-induced obesity, insulin resistance, and NAFLD [#4], and PEMT-derived choline supplies substrate for gut microbiota-dependent TMAO production that promotes atherosclerosis [#16]. Beyond bulk PC synthesis, PEMT generates DHA- and oleate-enriched PC species that support fetal brain development and circulating DHA delivery [#9, #13], and it couples to one-carbon metabolism by physically interacting with SHMT1 to sustain SAM-dependent histone methylation, with disruption depleting SAM and altering gene expression [#20]. PEMT also exerts a tumor-suppressive function in hepatoma, where re-expression inhibits anchorage-independent growth and tumorigenicity and triggers intrinsic mitochondrial apoptosis with downregulation of PI3K/Akt survival signaling [#5, #6, #7], and it acts non-cell-autonomously to control UCP1 splicing in brown adipose tissue during development [#14].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established that PEMT's essential hepatic role is to supply choline/phosphatidylcholine required for hepatocyte survival, resolving whether dietary choline could substitute for endogenous synthesis.\",\n      \"evidence\": \"Pemt-/- mouse dietary rescue with choline supplementation, plasma aminotransferase and hepatic PC/TAG readouts\",\n      \"pmids\": [\"11773510\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not define the molecular trigger linking PC deficiency to hepatocyte death\", \"Single lab\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defined PEMT as the sole de novo choline-synthesizing enzyme in liver and showed its loss is not fully compensable by dietary choline, anchoring its role in phospholipid homeostasis.\",\n      \"evidence\": \"Pemt-/- knockout mice across dietary choline levels; histology, TUNEL, metabolite quantification\",\n      \"pmids\": [\"12466019\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address tissue-specific contributions of hepatic vs extrahepatic PEMT\", \"Does not establish the apoptotic pathway\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Connected a human coding variant (V175M) to reduced enzyme activity, providing a genetic basis for impaired PC biosynthesis.\",\n      \"evidence\": \"Transient transfection of wild-type vs V175M PEMT in hepatoma cells with activity assay\",\n      \"pmids\": [\"16051693\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo phenotype tied to the variant\", \"Single method, single lab\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Positioned PEMT activity downstream of hepatic PC demand and upstream of steatohepatitis pathogenesis.\",\n      \"evidence\": \"Mdr2+/- mice on methionine-choline-deficient diet; PEMT activity, SAM:SAH, ALT, histology\",\n      \"pmids\": [\"16376450\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Correlative pathway position rather than direct causal manipulation of PEMT\", \"Single lab\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Revealed a tumor-suppressive function for PEMT through transcriptional loss in carcinogenesis and growth suppression on re-expression.\",\n      \"evidence\": \"Aflatoxin B1 rat carcinogenesis model; PEMT2 re-expression with soft-agar and xenograft assays\",\n      \"pmids\": [\"10760824\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not define the downstream effector of tumor suppression\", \"Single lab\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Mechanistically linked PEMT2-driven phospholipid changes to intrinsic mitochondrial apoptosis, building on the earlier PI3K/Akt downregulation finding.\",\n      \"evidence\": \"PEMT2 stable transfection; lipid tracing, mitochondrial fractionation, cytochrome C release, caspase-9/-3 activation; membrane fluidity\",\n      \"pmids\": [\"19517528\", \"11960751\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal chain from oleate-enriched PC to caspase activation not fully resolved\", \"Single lab cell-line context\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified the transcriptional control of PEMT by estrogen via an ERα/FOXA1-bound response element, explaining hormone- and SNP-dependent variation in PEMT expression.\",\n      \"evidence\": \"Transcript-specific expression analysis, SNP analysis, ChIP-chip for ER and FOXA1 binding\",\n      \"pmids\": [\"21059658\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address non-estrogen transcriptional inputs\", \"Functional consequence of the SNP in human liver not quantified here\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed epigenetic silencing of PEMT via cooperating DNA methylation and histone marks, providing a non-genetic route to PEMT loss in cancer.\",\n      \"evidence\": \"Bisulfite sequencing and ChIP for H3K9ac/H3K9me3 in BRCA1-mutated breast cancer specimens\",\n      \"pmids\": [\"24675476\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Correlative in patient tissue without manipulation of the marks\", \"Single lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated that PEMT activity promotes ER stress-induced apoptosis in diabetic kidney disease, extending its pro-apoptotic role to a non-hepatic tissue.\",\n      \"evidence\": \"STZ-diabetic Pemt-/- mice and shRNA knockdown in renal tubular cells; GRP78, p-Akt, caspase readouts\",\n      \"pmids\": [\"24667182\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting PEMT-derived PC to ER stress not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Established that PEMT supports fetal hippocampal development through incorporation of DHA into membrane phospholipids and modulation of SAM-dependent methylation.\",\n      \"evidence\": \"Pemt-/- mice with dietary DHA rescue; phospholipid-DHA, proliferation, TUNEL, calretinin readouts; earlier SAM/methylation analysis\",\n      \"pmids\": [\"19889625\", \"15063092\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contributions of DHA delivery vs methylation substrate not separated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified PEMT as the mechanism for the pregnancy-associated rise in circulating DHA-enriched PC.\",\n      \"evidence\": \"Rat pregnancy time-course; PEMT activity and protein, lipidomics for DHA-PC species\",\n      \"pmids\": [\"29167412\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Upstream signal driving gestational PEMT induction unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined hepatic PEMT-derived choline as the substrate source for gut microbiota-dependent TMAO production and a mechanistic link to atherosclerosis.\",\n      \"evidence\": \"AAV hepatic PEMT restoration in Pemt-/-/Ldlr-/- mice; plasma lipids, TMAO, aortic lesion quantification\",\n      \"pmids\": [\"30281112\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Microbial steps converting choline to TMAO not characterized here\", \"Single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved that hepatic, not extrahepatic, PEMT is the critical determinant of PC:PE ratio, NAFLD, and metabolic protection through orthogonal gain- and loss-of-function.\",\n      \"evidence\": \"AAV hepatic restoration and ASO knockdown in Pemt-/- and ob/ob mice with metabolic and lipid readouts\",\n      \"pmids\": [\"31284753\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not define the molecular sensor of PC:PE imbalance\", \"Tissue communication mechanisms not addressed\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Uncovered a non-cell-autonomous role for PEMT in controlling perinatal UCP1 splicing in brown adipose tissue.\",\n      \"evidence\": \"Multiple tissue-specific conditional Pemt knockouts; UCP1 protein and splice-variant mRNA, cold tolerance\",\n      \"pmids\": [\"31918922\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the intercellular signal from non-adipocytes to BAT unknown\", \"Splicing regulator linking PEMT to UCP1 unidentified\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Linked PEMT-dependent hepatic phospholipid balance to gluconeogenesis and systemic thermoregulation.\",\n      \"evidence\": \"HF-diet Pemt-/- mice with cold exposure and choline rescue; plasma glucose, gluconeogenic protein expression\",\n      \"pmids\": [\"26113536\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular coupling of PC balance to gluconeogenic gene expression unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed that HCV co-opts PEMT-mediated non-canonical PC synthesis to drive ER PC accumulation, lipogenesis, and viral replication.\",\n      \"evidence\": \"HCV cell culture, lipidomics, siRNA PEMT knockdown, lipogenic gene profiling, patient biopsy analysis\",\n      \"pmids\": [\"37240132\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How HCV induces PEMT transcription not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established a physical interaction between PEMT and SHMT1 that couples phospholipid synthesis to one-carbon/SAM availability and histone methylation in astrocytes.\",\n      \"evidence\": \"Co-immunoprecipitation of PEMT and SHMT1, 13C-serine labeling, ChIP for H3K4me1, astrocyte Shmt1 KO in a PD model\",\n      \"pmids\": [\"41262011\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single Co-IP without reciprocal structural mapping of the interaction\", \"Direction of metabolic coupling between the two enzymes not fully resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected aging-driven PEMT overexpression to hepatic PC/PE imbalance and steatosis, indicating excess PEMT activity is also pathogenic.\",\n      \"evidence\": \"Natural aging mouse lipidomics, PEMT Western blot, siRNA inhibition in senescent AML12 hepatocytes\",\n      \"pmids\": [\"41311052\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism driving age-associated PEMT induction unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The identity of the intercellular signal by which non-adipocyte PEMT controls UCP1 splicing, and the structural/regulatory basis of the PEMT-SHMT1 metabolic coupling, remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No identified mediator of PEMT's non-cell-autonomous effect on BAT\", \"No structural model of the PEMT-SHMT1 complex\", \"Molecular sensor of PC:PE imbalance unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 12, 13]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [20]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [19]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 4, 16, 21]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [5, 6, 7, 11]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [2, 10]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [8, 20]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"SHMT1\", \"ESR1\", \"FOXA1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}