{"gene":"LGR5","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":2007,"finding":"Lgr5 marks cycling crypt base columnar (CBC) cells at the intestinal crypt bottom; lineage-tracing using an inducible Cre knock-in allele demonstrated that these Lgr5+ CBC cells are self-renewing, multipotent stem cells that generate all epithelial lineages of the small intestine and colon over a 60-day period.","method":"Knock-in allele reporter mice; inducible Cre/Rosa26-lacZ lineage tracing in vivo","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct in vivo lineage tracing with genetic knock-in, replicated across many subsequent studies","pmids":["17934449"],"is_preprint":false},{"year":2009,"finding":"Single sorted Lgr5+ stem cells can self-organize into crypt-villus organoids in vitro, generating all differentiated epithelial cell types and maintaining the Lgr5+ stem-cell hierarchy, demonstrating that the intestinal crypt-villus unit is a self-organizing structure that does not require a non-epithelial mesenchymal niche.","method":"Single-cell sorting of Lgr5+ cells, 3D organoid culture, lineage tracing in vitro","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct functional reconstitution from single sorted cells, widely replicated","pmids":["19329995"],"is_preprint":false},{"year":2010,"finding":"Paneth cells constitute the niche for Lgr5+ stem cells by physically interdigitating with them and providing essential niche signals (EGF, TGF-α, Wnt3, Dll4); genetic removal of Paneth cells in vivo results in concomitant loss of Lgr5+ stem cells, and co-culture of sorted Lgr5+ stem cells with Paneth cells markedly improves organoid formation.","method":"Co-culture assays, genetic Paneth cell ablation in vivo, FACS sorting, organoid formation assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal genetic and co-culture experiments, in vivo and in vitro, replicated","pmids":["21113151"],"is_preprint":false},{"year":2010,"finding":"Lgr5-high stem cells in the intestinal crypt divide symmetrically and undergo neutral drift dynamics; crypt clonality is achieved stochastically rather than through asymmetric division, as shown by multicolor clonal fate mapping.","method":"Multicolor Cre-reporter fate mapping (Rainbow mouse); quantitative clonal tracing","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multicolor clonal tracing with quantitative modeling, single rigorous study with multiple orthogonal analyses","pmids":["20887898"],"is_preprint":false},{"year":2012,"finding":"LGR5, upon co-stimulation with R-spondin1 and Wnt3a, forms a supercomplex with Wnt co-receptors LRP6 and Fzd5, which is internalized via a dynamin- and clathrin-dependent pathway; deletion of the LGR5 C-terminal tail increases signaling activity and decreases endocytosis, indicating that internalization is not required for Wnt/β-catenin potentiation.","method":"Co-immunoprecipitation, endocytosis inhibitors, C-terminal deletion mutagenesis, luciferase Wnt reporter assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — reciprocal Co-IP, mutagenesis, and functional reporter assays in single lab with multiple orthogonal methods","pmids":["22473993"],"is_preprint":false},{"year":2014,"finding":"The R-spondin/Lgr5/Rnf43 module regulates Wnt signal strength: Lgr5 and homologs Lgr4/Lgr6 are receptors for R-spondins; the Lgr5/R-spondin complex acts by neutralizing RNF43 and ZNRF3, two transmembrane E3 ligases (themselves Wnt target genes) that remove Wnt receptors from the stem cell surface, constituting a negative Wnt feedback loop that is relieved by R-spondin.","method":"Biochemical characterization, review synthesizing multiple experimental findings including receptor identification and E3 ligase neutralization","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — synthesis of replicated findings from multiple labs using receptor-ligand binding, genetic, and cell biology approaches","pmids":["24532711"],"is_preprint":false},{"year":2014,"finding":"RSPO2 interacts with LGR5 to stabilize membrane-associated ZNRF3, thereby inhibiting Wnt/β-catenin signaling in colorectal cancer cells; the RSPO2-induced inhibition of Wnt signaling is dependent on LGR5, revealing a LGR5-dependent negative feedback mechanism.","method":"Co-immunoprecipitation, LGR5 knockdown, Wnt reporter assays, cell proliferation assays","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and KD with reporter assays, single lab","pmids":["24476626"],"is_preprint":false},{"year":2015,"finding":"Lgr5 and Lgr4 promote formation of ultra-long actin-rich cytoneme-like membrane protrusions (exceeding 80 µm) by stabilizing nascent filopodia from a lamellipodial-like network; these cytonemes serve as conduits for transit of signaling effectors including myosin X (Myo10) and β-arrestin-2 (Arrb2).","method":"Live-cell imaging, overexpression of Lgr4/Lgr5, fluorescent reporter constructs for cargo tracking","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct live-cell imaging with functional cargo tracking, single lab","pmids":["25653388"],"is_preprint":false},{"year":2013,"finding":"LGR5/GPR49 overexpression activates the G12/13-Rho GTPase signaling pathway in a ligand-independent manner; LGR5-induced SRF-RE reporter activity is blocked by Rho inhibitor C3 transferase, RhoA-N19 mutant, and Gα12/13 knockdown. R-spondin ligands did not activate this Rho pathway in the presence of LGR5.","method":"SRF-RE luciferase reporter assay, dominant-negative mutants, siRNA knockdown of Gα12/13, LGR5 overexpression","journal":"Molecules and cells","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — multiple orthogonal approaches (reporter, dominant-negative, KD) but single lab","pmids":["23912594"],"is_preprint":false},{"year":2019,"finding":"The HECT-domain E3 ubiquitin ligases NEDD4 and NEDD4L are expressed in intestinal crypt stem cell regions and negatively regulate LGR5 receptor and DVL2 by targeting them for proteasomal and lysosomal degradation; loss of Nedd4/Nedd4l enhances ISC proliferation, increases sensitivity to R-spondin stimulation, and accelerates tumor development.","method":"Genetic deletion of Nedd4/Nedd4l, organoid assays, Western blotting for protein degradation, ApcMin tumor model","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function in vivo and in vitro with mechanistic follow-up (degradation pathway), single lab with multiple orthogonal methods","pmids":["31867777"],"is_preprint":false},{"year":2020,"finding":"Unlike LGR4, full-length LGR5 does not interact with E3 ligases RNF43 or ZNRF3 (with or without RSPO), as shown by Co-IP, proximity ligation, competition binding, and time-resolved FRET assays; instead, LGR5 interacts with FZD and LRP6 of the Wnt signalosome to enhance LRP6 phosphorylation and potentiate Wnt/β-catenin signaling. Domain-swapping revealed the LGR4 seven-transmembrane domain confers E3 ligase interaction.","method":"Co-immunoprecipitation, proximity ligation assay, competition binding, time-resolved FRET, domain-swap mutagenesis","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — four orthogonal biochemical methods plus domain-swap mutagenesis in one rigorous study","pmids":["33262293"],"is_preprint":false},{"year":2023,"finding":"LGR4 forms a 2:2 homodimer complex with RNF43/ZNRF3 that accommodates bivalent RSPO binding, whereas LGR5 forms a homodimer that does not interact with these E3 ligases; monovalent and bivalent RSPO2 have nearly identical affinity for LGR5, in contrast to LGR4. Co-expression of ZNRF3 with LGR4 greatly increases monovalent RSPO affinity but has no effect when co-expressed with LGR5.","method":"Whole-cell binding affinity assays, co-immunoprecipitation, structural modeling","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — multiple binding assays and structural models, single lab","pmids":["37402772"],"is_preprint":false},{"year":2020,"finding":"LGR5 and LGR4 constitutively activate NF-κB signaling in a ligand-independent manner through their C-termini; the C-termini of LGR5/4 interact with the adaptor protein TROY, which is required for NF-κB activation. Overexpression of a C-terminal deletion mutant of LGR5 inhibits organoid growth and budding, while an R-spondin-binding-deficient mutant of LGR5 still promotes organoid growth via NF-κB.","method":"C-terminal deletion and binding-domain mutagenesis, luciferase NF-κB reporter, co-immunoprecipitation with TROY, intestinal organoid growth assays","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis, Co-IP, and functional organoid readout with multiple constructs, single lab","pmids":["33001511"],"is_preprint":false},{"year":2017,"finding":"R-spondin1/LGR5 directly activates TGFβ signaling cooperatively with TGFβ type II receptor in colon cancer cells; upon RSPO1 stimulation, LGR5 forms complexes with TGFβ receptors, enhancing TGFβ-mediated growth inhibition and apoptosis. LGR5 knockdown attenuated downstream TGFβ signaling and increased metastasis in an orthotopic colon cancer model.","method":"Co-immunoprecipitation (LGR5-TGFβR complex), siRNA knockdown, orthotopic xenograft model, downstream signaling assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and in vivo KD model with functional readout, single lab","pmids":["28939678"],"is_preprint":false},{"year":2017,"finding":"Wnt and R-spondin ligands have qualitatively distinct, non-interchangeable roles in Lgr5+ ISC self-renewal: Wnt proteins cannot induce ISC self-renewal but confer basal competency by maintaining RSPO receptor (LGR5) expression, while RSPO ligands actively drive stem-cell expansion. This was shown using a non-lipidated Wnt analogue and genetic/organoid approaches.","method":"In vivo genetic Wnt loss-of-function, non-lipidated Wnt analogue, RSPO gain-of-function, Lgr5+ ISC organoid culture, single-cell lineage tracing","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vivo and in vitro approaches, published in high-impact journal, functional dissection with synthetic ligands","pmids":["28467820"],"is_preprint":false},{"year":2015,"finding":"Notch signaling is intrinsic to the gastric epithelium and is essential for homeostasis of LGR5+ antral stem cells; Notch inhibition reduces proliferation and induces mucous/endocrine differentiation, while constitutive Notch activation in LGR5+ stem cells induces gland fission and tissue expansion via mTORC1 signaling.","method":"Pharmacological Notch inhibition/activation, conditional Notch activation using Lgr5-Cre, gastric organoid culture, multicolor lineage tracing","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological approaches in vivo and in vitro with multiple orthogonal readouts in single rigorous study","pmids":["26271103"],"is_preprint":false},{"year":2015,"finding":"Yap transiently reprograms Lgr5+ ISCs by suppressing Wnt signaling and excessive Paneth cell differentiation while promoting cell survival and inducing an Egf pathway regenerative program; Yap-deficient organoid growth is rescued by the Egfr ligand epiregulin, and Yap inactivation abolishes adenomas in Apc(Min) mice.","method":"Yap conditional knockout mice, irradiation injury model, organoid rescue assays with epiregulin, Apc(Min) tumor model","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic KO with multiple phenotypic and epistatic readouts, replicated across tissue injury and cancer models","pmids":["26503053"],"is_preprint":false},{"year":2019,"finding":"R-spondin-3 (Rspo3) secreted by myofibroblasts acts on basal Lgr5+ gastric stem cells to induce their differentiation into secretory cells expressing antimicrobial factors (e.g., intelectin-1), rather than promoting proliferation; depletion of Lgr5+ cells or Rspo3 knockout leads to hypercolonization of gastric glands with H. pylori.","method":"Lgr5+ cell depletion, Rspo3 conditional knockout in myofibroblasts, systemic Rspo3 administration, H. pylori colonization assays","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO and cell ablation in vivo with specific functional (antimicrobial/colonization) readout, multiple complementary approaches","pmids":["31235935"],"is_preprint":false},{"year":2017,"finding":"LGR5 expression in neuroblastoma cells regulates pro-survival MEK/ERK signaling independently of Wnt; siRNA-mediated LGR5 knockdown induces apoptosis accompanied by decreased phosphorylation of MEK1/2 and ERK1/2, increased BimEL, decreased Akt signaling via a Rictor-dependent PDK1-independent mechanism, and G1 cell-cycle arrest with increased p27.","method":"siRNA knockdown, Western blotting for MEK/ERK/Akt phosphorylation, cell cycle analysis, apoptosis assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — multiple signaling readouts from KD, single lab","pmids":["26517508"],"is_preprint":false},{"year":2016,"finding":"LGR5 undergoes rapid, constitutive internalization independent of ligand, and LGR5-high cancer cells exhibit properties of tumor-initiating/cancer stem cells; LGR5-targeting antibody-drug conjugates internalize to lysosomes of LGR5-expressing cells and induce cytotoxicity specifically in LGR5-high but not LGR5-negative or LGR5-knockdown cells.","method":"Receptor binding assays, cell internalization assays, cytotoxicity assays, xenograft tumor model","journal":"Molecular cancer therapeutics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct internalization assay with functional (cytotoxicity) readout, single lab","pmids":["27207778"],"is_preprint":false},{"year":2022,"finding":"IL-17A signaling through IL-17RA in Lgr5+ intestinal stem cells induces expression of transcription factor ATOH1 to promote secretory epithelial cell lineage commitment; multiple conditional deletion models demonstrated that Paneth, tuft, goblet, and enteroendocrine cell numbers were dependent on this IL-17A/ATOH1 axis specifically in Lgr5+ cells.","method":"Multiple conditional deletion mouse models (Lgr5-Cre, ATOH1-Cre), human intestinal organoid stimulation with IL-17A","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple conditional genetic models with specific cellular phenotypes, complemented by human organoid experiments","pmids":["35081371"],"is_preprint":false},{"year":2020,"finding":"NOD2 agonist MDP protects Lgr5+ intestinal stem cells against oxidative stress-induced death via mitophagy; MDP-induced cytoprotection requires both NOD2 and ATG16L1; the mechanism involves NOD2-dependent reduction of mitochondrial ROS through mitophagy induction, independent of NF-κB.","method":"ATG16L1 and NOD2 knockout organoids, irradiation stress model, ROS measurement, mitophagy quantification in vivo and in vitro","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic KO of two pathway components with mechanistic ROS/mitophagy readouts in vivo and in vitro, single lab","pmids":["31919280"],"is_preprint":false},{"year":2016,"finding":"IKKα binds directly to the LGR5 promoter in basal cell carcinoma cells and upregulates LGR5 expression through activation of the STAT3 signaling pathway; STAT3 and IKKα interact functionally to drive LGR5 expression during BCC cancer progression.","method":"ChIP assay (IKKα at LGR5 promoter), STAT3 pathway inhibition, IKKα knockdown, tumor growth assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — ChIP and KD with functional readout, single lab","pmids":["27049829"],"is_preprint":false},{"year":2015,"finding":"SOX9 directly transcriptionally upregulates LGR5 expression in glioblastoma cells; knockdown of SOX9 suppresses LGR5 expression, proliferation, and tumorigenicity of glioblastoma cells, establishing a SOX9-LGR5 regulatory axis.","method":"SOX9 knockdown, luciferase reporter (LGR5 promoter), ChIP, LGR5 KD functional assays","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — transcriptional regulation assays with promoter reporter and ChIP, single lab","pmids":["25770425"],"is_preprint":false},{"year":2017,"finding":"LGR5 knockdown in human pluripotent stem cells (hPSCs) reduces cardiomyocyte-associated markers and impairs cardiac differentiation, while promoting endothelial cell differentiation with increased nuclear translocation of β-catenin and upregulation of Wnt signaling-related genes, indicating LGR5 modulates hPSC lineage fate through Wnt/β-catenin regulation.","method":"LGR5 siRNA knockdown during hPSC differentiation, qRT-PCR, immunostaining, functional tube formation and LDL uptake assays","journal":"Stem cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — KD with multiple differentiation readouts, single lab","pmids":["28793247"],"is_preprint":false},{"year":2024,"finding":"LGR5+ colorectal cancer stem cells are mechanically stiffer, adhere better to ECM, move slower, display higher nuclear YAP, and form larger transendothelial gaps compared to LGR5- cells; these differences are largely explained by downregulation of membrane-to-cortex attachment proteins Ezrin/Radixin/Moesin (ERMs) in LGR5+ cells.","method":"Patient-derived organoids, single-cell RNA-seq, atomic force microscopy, live-cell imaging, ERM knockdown/overexpression","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (mechanical measurements, genomics, functional rescue) linking ERM downregulation mechanistically to LGR5+ cell properties","pmids":["38637494"],"is_preprint":false},{"year":2023,"finding":"Loss of LGR5 expression (through chemotherapy, LGR5-targeted ADC treatment, or gene ablation) in colorectal cancer cells activates STAT3 via increased MET (mesenchymal-epithelial transition factor) receptor activity; LGR5 overexpression decreased MET-STAT3 activity, and STAT3 inhibition suppressed MET phosphorylation, suggesting a feedback mechanism between LGR5, MET, and STAT3.","method":"LGR5 gene ablation, LGR5 overexpression, Western blotting, MET/STAT3 inhibition, tumor organoids and xenograft model","journal":"Molecular cancer therapeutics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple complementary approaches (KO, OE, inhibitors, in vivo) in single lab","pmids":["36921315"],"is_preprint":false},{"year":2022,"finding":"Quiescent (slow-cycling) LGR5+p27+ cells exist in the human colon and display lineage-forming capability in vivo; TGFβ signaling regulates the quiescent state of these LGR5+ cells, as shown by orthotopic xenotransplantation and lineage tracing of LGR5-tdTomato/LGR5-iCaspase9 knock-in human colon organoids.","method":"Single-cell RNA-seq, genome-engineered human organoid knock-ins (LGR5-tdTomato, LGR5-iCaspase9, p27-mVenus), orthotopic xenotransplantation, EdU pulse-chase, TGFβ pathway manipulation","journal":"Gastroenterology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genome-engineered reporter lines with in vivo transplantation and pathway manipulation, single rigorous study with multiple orthogonal methods","pmids":["35963362"],"is_preprint":false},{"year":2021,"finding":"REGγ enhances transcriptional activation of Lgr5 via potentiation of both Wnt and Hippo signaling pathways; TEAD4 alone or cooperating with TCF4 directly enhances Lgr5 expression, and silencing TEAD4 drastically attenuates β-catenin/TCF4-dependent Lgr5 expression. Conditional ablation of REGγ in Lgr5+ stem cells impairs intestinal crypt proliferation and delays regeneration after irradiation.","method":"Conditional REGγ knockout in Lgr5+ cells, TEAD4 and TCF4 co-transfection/silencing, luciferase reporter assays for Lgr5 promoter, irradiation injury model","journal":"Science China. Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — conditional KO with mechanistic promoter assays, single lab","pmids":["34826093"],"is_preprint":false}],"current_model":"LGR5 is a seven-transmembrane leucine-rich repeat-containing G-protein-coupled receptor that serves as the cell-surface receptor for R-spondin ligands; upon R-spondin binding it potentiates Wnt/β-catenin signaling by forming a complex with Wnt co-receptors FZD and LRP6 to enhance LRP6 phosphorylation (without sequestering E3 ligases RNF43/ZNRF3 as LGR4 does), and independently activates NF-κB signaling via its C-terminus through TROY, as well as G12/13-Rho GTPase signaling; LGR5 is post-translationally regulated by NEDD4/NEDD4L-mediated proteasomal and lysosomal degradation, constitutively internalizes via clathrin/dynamin, drives formation of actin-rich cytoneme-like protrusions, and marks multipotent self-renewing adult stem cells in intestinal crypts, stomach, liver, hair follicle, and other tissues where it is a Wnt target gene maintaining stem cell identity."},"narrative":{"mechanistic_narrative":"LGR5 is a seven-transmembrane R-spondin receptor that marks and maintains multipotent, self-renewing adult stem cells, defined originally as the cycling crypt base columnar cells that regenerate all intestinal epithelial lineages and self-organize into crypt-villus organoids from single cells [PMID:17934449, PMID:19329995]. Mechanistically, R-spondin-bound LGR5 forms a supercomplex with the Wnt co-receptors FZD5 and LRP6 to enhance LRP6 phosphorylation and potentiate Wnt/β-catenin signaling [PMID:22473993, PMID:33262293]; this complex internalizes via clathrin/dynamin, but endocytosis is dispensable for signaling, as C-terminal truncation increases activity while reducing internalization [PMID:22473993, PMID:27207778]. Within the Wnt module, the R-spondin/LGR5 interaction tunes signal strength by neutralizing the transmembrane E3 ligases RNF43/ZNRF3 that remove Wnt receptors, yet unlike its paralog LGR4, full-length LGR5 does not itself bind RNF43/ZNRF3—a distinction conferred by the seven-transmembrane domain [PMID:24532711, PMID:33262293, PMID:37402772]. Beyond Wnt potentiation, LGR5 engages additional outputs: its C-terminus drives ligand-independent, TROY-dependent NF-κB activation that supports organoid growth, and it activates G12/13-Rho-SRF signaling and shapes actin-rich cytoneme-like protrusions [PMID:33001511, PMID:23912594, PMID:25653388]. LGR5 receptor abundance is constrained post-translationally by NEDD4/NEDD4L-mediated proteasomal and lysosomal degradation, loss of which heightens R-spondin sensitivity and accelerates tumorigenesis [PMID:31867777]. In tissue, LGR5+ stem cell behavior is governed by niche inputs—Paneth-cell-derived signals, Notch, YAP, IL-17A/ATOH1, and distinct Wnt versus R-spondin roles—that couple self-renewal to differentiation and regeneration [PMID:21113151, PMID:26271103, PMID:26503053, PMID:35081371, PMID:28467820], and LGR5 expression is itself a transcriptional output of Wnt/Hippo and other regulators [PMID:34826093].","teleology":[{"year":2007,"claim":"Established that LGR5 is not just a Wnt target but a functional marker of bona fide adult stem cells, answering what cell population sustains the intestinal epithelium.","evidence":"Inducible Cre knock-in lineage tracing in mouse intestine in vivo","pmids":["17934449"],"confidence":"High","gaps":["Does not define LGR5's biochemical signaling activity","Marker function does not establish whether LGR5 protein is required for stemness"]},{"year":2009,"claim":"Showed LGR5+ cells are intrinsically multipotent and niche-independent for organization, by reconstituting crypt-villus organoids from single sorted cells.","evidence":"Single-cell sorting and 3D organoid culture in vitro","pmids":["19329995"],"confidence":"High","gaps":["Culture requires exogenous Wnt/R-spondin/EGF, so cell-autonomous signaling roles remain unresolved","Does not address LGR5 receptor mechanism"]},{"year":2010,"claim":"Defined the cellular niche and population dynamics of LGR5+ stem cells, establishing Paneth cells as signal providers and symmetric neutral-drift division as the renewal mode.","evidence":"Genetic Paneth ablation, co-culture, and multicolor clonal fate mapping in vivo","pmids":["21113151","20887898"],"confidence":"High","gaps":["Niche signals identified are paracrine ligands, not LGR5-direct receptor events","Does not connect division dynamics to LGR5 signaling output"]},{"year":2012,"claim":"Resolved how LGR5 acts within the Wnt machinery, showing it forms an internalizing LRP6/FZD5 supercomplex but that endocytosis is uncoupled from β-catenin potentiation.","evidence":"Co-IP, endocytosis inhibitors, C-terminal deletion, Wnt luciferase reporters","pmids":["22473993"],"confidence":"High","gaps":["Mechanism by which the complex enhances LRP6 phosphorylation not detailed here","Role of the C-terminal tail in negative regulation left open"]},{"year":2013,"claim":"Identified a Wnt-independent LGR5 output, showing ligand-independent G12/13-Rho-SRF activation.","evidence":"SRF-RE reporter, dominant-negative RhoA/G12-13, siRNA knockdown, overexpression","pmids":["23912594"],"confidence":"Medium","gaps":["Relies on overexpression; physiological relevance in stem cells untested","Single lab, no in vivo confirmation"]},{"year":2014,"claim":"Placed LGR5 mechanistically as the receptor that tunes Wnt signal strength via the R-spondin/RNF43/ZNRF3 feedback loop.","evidence":"Receptor-ligand and E3-ligase neutralization biochemistry; Co-IP and reporter assays in cancer cells","pmids":["24532711","24476626"],"confidence":"High","gaps":["Whether LGR5 itself binds the E3 ligases was not yet distinguished from paralogs","Context-dependent positive vs negative effects unresolved"]},{"year":2015,"claim":"Extended LGR5 cell biology to membrane morphology and gastric/niche regulation, linking it to cytoneme formation and Notch-dependent gastric stem cell homeostasis.","evidence":"Live-cell imaging of cytonemes; Notch manipulation with Lgr5-Cre and gastric organoids","pmids":["25653388","26271103"],"confidence":"Medium","gaps":["Cytoneme function based on overexpression imaging","Notch acts on LGR5+ cells but not via LGR5 receptor itself"]},{"year":2017,"claim":"Dissected non-interchangeable Wnt vs R-spondin roles and identified TGFβ cross-talk, showing Wnt maintains LGR5 expression/competency while R-spondin drives expansion, and LGR5 can couple to TGFβ receptors.","evidence":"Synthetic non-lipidated Wnt analogue, RSPO gain-of-function, lineage tracing; LGR5-TGFβR Co-IP with orthotopic model","pmids":["28467820","28939678"],"confidence":"High","gaps":["TGFβ coupling shown in cancer cells (Medium); generality to normal stem cells unclear","Molecular basis of LGR5-TGFβR complex undefined"]},{"year":2019,"claim":"Defined post-translational control of LGR5, showing NEDD4/NEDD4L degrade the receptor to restrain R-spondin sensitivity and tumorigenesis.","evidence":"Genetic Nedd4/Nedd4l deletion, organoid assays, degradation Western blots, ApcMin model","pmids":["31867777"],"confidence":"High","gaps":["Ubiquitination sites on LGR5 not mapped","Balance between proteasomal and lysosomal routes unresolved"]},{"year":2020,"claim":"Mechanistically separated LGR5 from LGR4, establishing that LGR5 does not bind RNF43/ZNRF3 but instead enhances LRP6 phosphorylation, and that its C-terminus drives TROY-dependent NF-κB signaling.","evidence":"Co-IP, PLA, competition binding, TR-FRET, domain-swap mutagenesis; NF-κB reporter and TROY Co-IP with organoid growth assays","pmids":["33262293","33001511"],"confidence":"High","gaps":["How the 7TM domain selects against E3-ligase binding not structurally resolved","NF-κB branch validated in single lab (Medium)"]},{"year":2023,"claim":"Provided structural-level rationale for paralog divergence, showing LGR4 forms a 2:2 complex with RNF43/ZNRF3 enabling bivalent RSPO sensing while LGR5 homodimers do not.","evidence":"Whole-cell binding affinity assays, Co-IP, structural modeling","pmids":["37402772"],"confidence":"Medium","gaps":["No experimental high-resolution structure of LGR5 complexes","Functional consequence of monovalent/bivalent equivalence in LGR5 stem cells untested"]},{"year":2024,"claim":"Connected LGR5+ identity to mechanical and metastatic cancer-stem-cell phenotypes through ERM downregulation.","evidence":"Patient-derived organoids, scRNA-seq, atomic force microscopy, ERM knockdown/overexpression","pmids":["38637494"],"confidence":"High","gaps":["Whether ERM downregulation is downstream of LGR5 signaling per se is not established","Link to specific LGR5 signaling branch (Wnt/NF-κB/Rho) undefined"]},{"year":null,"claim":"It remains unresolved how LGR5's multiple signaling outputs (Wnt potentiation, NF-κB, G12/13-Rho, TGFβ coupling) are integrated and balanced within a single stem cell to control self-renewal versus differentiation.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural model of LGR5 distinguishing its branch-specific conformations","Quantitative contribution of each branch to stem-cell maintenance in vivo unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[4,5,10]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[5,11]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,5,10]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4,10,19]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[4,19]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,5,10,12,8]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,1,14]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[9,25,26]}],"complexes":["Wnt signalosome (LGR5-FZD5-LRP6)"],"partners":["RSPO1","RSPO2","LRP6","FZD5","RNF43","ZNRF3","TROY","NEDD4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O75473","full_name":"Leucine-rich repeat-containing G-protein coupled receptor 5","aliases":["G-protein coupled receptor 49","G-protein coupled receptor 67","G-protein coupled receptor HG38"],"length_aa":907,"mass_kda":100.0,"function":"Receptor for R-spondins that potentiates the canonical Wnt signaling pathway and acts as a stem cell marker of the intestinal epithelium and the hair follicle. Upon binding to R-spondins (RSPO1, RSPO2, RSPO3 or RSPO4), associates with phosphorylated LRP6 and frizzled receptors that are activated by extracellular Wnt receptors, triggering the canonical Wnt signaling pathway to increase expression of target genes. In contrast to classical G-protein coupled receptors, does not activate heterotrimeric G-proteins to transduce the signal. Involved in the development and/or maintenance of the adult intestinal stem cells during postembryonic development","subcellular_location":"Cell membrane; Golgi apparatus, trans-Golgi network membrane","url":"https://www.uniprot.org/uniprotkb/O75473/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LGR5","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/LGR5","total_profiled":1310},"omim":[{"mim_id":"612482","title":"RING FINGER PROTEIN 43; RNF43","url":"https://www.omim.org/entry/612482"},{"mim_id":"612062","title":"ZINC FINGER AND RING FINGER PROTEIN 3; ZNRF3","url":"https://www.omim.org/entry/612062"},{"mim_id":"610575","title":"R-SPONDIN 2; 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patients.","date":"2011","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/21978106","citation_count":21,"is_preprint":false},{"pmid":"33249719","id":"PMC_33249719","title":"LGR5 induces β-catenin activation and augments tumour progression by activating STAT3 in human intrahepatic cholangiocarcinoma.","date":"2020","source":"Liver international : official journal of the International Association for the Study of the Liver","url":"https://pubmed.ncbi.nlm.nih.gov/33249719","citation_count":21,"is_preprint":false},{"pmid":"27140312","id":"PMC_27140312","title":"Full-length LGR5-positive cells have chemoresistant characteristics in colorectal cancer.","date":"2016","source":"British journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/27140312","citation_count":20,"is_preprint":false},{"pmid":"35218981","id":"PMC_35218981","title":"Glucagon-Like Peptide-2 Stimulates S-Phase Entry of Intestinal Lgr5+ Stem Cells.","date":"2022","source":"Cellular and molecular gastroenterology and hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/35218981","citation_count":19,"is_preprint":false},{"pmid":"25770425","id":"PMC_25770425","title":"SOX9-mediated upregulation of LGR5 is important for glioblastoma tumorigenicity.","date":"2015","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/25770425","citation_count":19,"is_preprint":false},{"pmid":"29149105","id":"PMC_29149105","title":"LGR5 expression is regulated by EGF in early colorectal adenomas and governs EGFR inhibitor sensitivity.","date":"2017","source":"British journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/29149105","citation_count":18,"is_preprint":false},{"pmid":"37402772","id":"PMC_37402772","title":"LGR4 and LGR5 form distinct homodimers that only LGR4 complexes with RNF43/ZNRF3 to provide high affinity binding of R-spondin ligands.","date":"2023","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/37402772","citation_count":18,"is_preprint":false},{"pmid":"29928673","id":"PMC_29928673","title":"Monoclonal Antibodies Reveal Dynamic Plasticity Between Lgr5- and Bmi1-Expressing Intestinal Cell Populations.","date":"2018","source":"Cellular and molecular gastroenterology and hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/29928673","citation_count":18,"is_preprint":false},{"pmid":"28793247","id":"PMC_28793247","title":"Downregulation of LGR5 Expression Inhibits Cardiomyocyte Differentiation and Potentiates Endothelial Differentiation from Human Pluripotent Stem Cells.","date":"2017","source":"Stem cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/28793247","citation_count":17,"is_preprint":false},{"pmid":"25592865","id":"PMC_25592865","title":"LGR5 expression in oral epithelial dysplasia and oral squamous cell carcinoma.","date":"2014","source":"Oral surgery, oral medicine, oral pathology and oral radiology","url":"https://pubmed.ncbi.nlm.nih.gov/25592865","citation_count":16,"is_preprint":false},{"pmid":"24246263","id":"PMC_24246263","title":"The Lgr5 transgene is expressed specifically in glycinergic amacrine cells in the mouse retina.","date":"2013","source":"Experimental eye research","url":"https://pubmed.ncbi.nlm.nih.gov/24246263","citation_count":16,"is_preprint":false},{"pmid":"28404917","id":"PMC_28404917","title":"Expression and functional regulation of stemness gene Lgr5 in esophageal squamous cell carcinoma.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/28404917","citation_count":16,"is_preprint":false},{"pmid":"26280006","id":"PMC_26280006","title":"Overexpression of Leucine-Rich Repeat-Containing G Protein-Coupled Receptor 5 (LGR5) Represents a Typical Wnt/β-Catenin Pathway-Activated Hepatocellular Carcinoma.","date":"2014","source":"Liver cancer","url":"https://pubmed.ncbi.nlm.nih.gov/26280006","citation_count":16,"is_preprint":false},{"pmid":"23793848","id":"PMC_23793848","title":"LGR5 is a proneural factor and is regulated by OLIG2 in glioma stem-like cells.","date":"2013","source":"Cellular and molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/23793848","citation_count":16,"is_preprint":false},{"pmid":"33001511","id":"PMC_33001511","title":"LGR5 constitutively activates NF-κB signaling to regulate the growth of intestinal crypts.","date":"2020","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/33001511","citation_count":16,"is_preprint":false},{"pmid":"39821694","id":"PMC_39821694","title":"LGR5: An emerging therapeutic target for cancer metastasis and chemotherapy resistance.","date":"2025","source":"Cancer metastasis reviews","url":"https://pubmed.ncbi.nlm.nih.gov/39821694","citation_count":15,"is_preprint":false},{"pmid":"35778589","id":"PMC_35778589","title":"Differential epithelial and stromal LGR5 expression in ovarian carcinogenesis.","date":"2022","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/35778589","citation_count":14,"is_preprint":false},{"pmid":"36318235","id":"PMC_36318235","title":"Elevated Expression of LGR5 and WNT Signaling Factors in Neuroblastoma Cells With Acquired Drug Resistance.","date":"2022","source":"Cancer investigation","url":"https://pubmed.ncbi.nlm.nih.gov/36318235","citation_count":14,"is_preprint":false},{"pmid":"36921315","id":"PMC_36921315","title":"Loss of LGR5 through Therapy-induced Downregulation or Gene Ablation Is Associated with Resistance and Enhanced MET-STAT3 Signaling in Colorectal Cancer Cells.","date":"2023","source":"Molecular cancer therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/36921315","citation_count":14,"is_preprint":false},{"pmid":"39169164","id":"PMC_39169164","title":"Novel immunotherapeutics against LGR5 to target multiple cancer types.","date":"2024","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/39169164","citation_count":13,"is_preprint":false},{"pmid":"23912594","id":"PMC_23912594","title":"Leucine-rich repeat-containing G-protein coupled receptor 5/GPR49 activates G12/13-Rho GTPase pathway.","date":"2013","source":"Molecules and cells","url":"https://pubmed.ncbi.nlm.nih.gov/23912594","citation_count":13,"is_preprint":false},{"pmid":"31966480","id":"PMC_31966480","title":"Expression of LGR5 in oral squamous cell carcinoma and its correlation to vasculogenic mimicry.","date":"2017","source":"International journal of clinical and experimental pathology","url":"https://pubmed.ncbi.nlm.nih.gov/31966480","citation_count":13,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":48729,"output_tokens":7303,"usd":0.127866,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":16511,"output_tokens":4170,"usd":0.093402,"stage2_stop_reason":"end_turn"},"total_usd":0.221268,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"Lgr5 marks cycling crypt base columnar (CBC) cells at the intestinal crypt bottom; lineage-tracing using an inducible Cre knock-in allele demonstrated that these Lgr5+ CBC cells are self-renewing, multipotent stem cells that generate all epithelial lineages of the small intestine and colon over a 60-day period.\",\n      \"method\": \"Knock-in allele reporter mice; inducible Cre/Rosa26-lacZ lineage tracing in vivo\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct in vivo lineage tracing with genetic knock-in, replicated across many subsequent studies\",\n      \"pmids\": [\"17934449\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Single sorted Lgr5+ stem cells can self-organize into crypt-villus organoids in vitro, generating all differentiated epithelial cell types and maintaining the Lgr5+ stem-cell hierarchy, demonstrating that the intestinal crypt-villus unit is a self-organizing structure that does not require a non-epithelial mesenchymal niche.\",\n      \"method\": \"Single-cell sorting of Lgr5+ cells, 3D organoid culture, lineage tracing in vitro\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct functional reconstitution from single sorted cells, widely replicated\",\n      \"pmids\": [\"19329995\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Paneth cells constitute the niche for Lgr5+ stem cells by physically interdigitating with them and providing essential niche signals (EGF, TGF-α, Wnt3, Dll4); genetic removal of Paneth cells in vivo results in concomitant loss of Lgr5+ stem cells, and co-culture of sorted Lgr5+ stem cells with Paneth cells markedly improves organoid formation.\",\n      \"method\": \"Co-culture assays, genetic Paneth cell ablation in vivo, FACS sorting, organoid formation assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal genetic and co-culture experiments, in vivo and in vitro, replicated\",\n      \"pmids\": [\"21113151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Lgr5-high stem cells in the intestinal crypt divide symmetrically and undergo neutral drift dynamics; crypt clonality is achieved stochastically rather than through asymmetric division, as shown by multicolor clonal fate mapping.\",\n      \"method\": \"Multicolor Cre-reporter fate mapping (Rainbow mouse); quantitative clonal tracing\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multicolor clonal tracing with quantitative modeling, single rigorous study with multiple orthogonal analyses\",\n      \"pmids\": [\"20887898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"LGR5, upon co-stimulation with R-spondin1 and Wnt3a, forms a supercomplex with Wnt co-receptors LRP6 and Fzd5, which is internalized via a dynamin- and clathrin-dependent pathway; deletion of the LGR5 C-terminal tail increases signaling activity and decreases endocytosis, indicating that internalization is not required for Wnt/β-catenin potentiation.\",\n      \"method\": \"Co-immunoprecipitation, endocytosis inhibitors, C-terminal deletion mutagenesis, luciferase Wnt reporter assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — reciprocal Co-IP, mutagenesis, and functional reporter assays in single lab with multiple orthogonal methods\",\n      \"pmids\": [\"22473993\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The R-spondin/Lgr5/Rnf43 module regulates Wnt signal strength: Lgr5 and homologs Lgr4/Lgr6 are receptors for R-spondins; the Lgr5/R-spondin complex acts by neutralizing RNF43 and ZNRF3, two transmembrane E3 ligases (themselves Wnt target genes) that remove Wnt receptors from the stem cell surface, constituting a negative Wnt feedback loop that is relieved by R-spondin.\",\n      \"method\": \"Biochemical characterization, review synthesizing multiple experimental findings including receptor identification and E3 ligase neutralization\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — synthesis of replicated findings from multiple labs using receptor-ligand binding, genetic, and cell biology approaches\",\n      \"pmids\": [\"24532711\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RSPO2 interacts with LGR5 to stabilize membrane-associated ZNRF3, thereby inhibiting Wnt/β-catenin signaling in colorectal cancer cells; the RSPO2-induced inhibition of Wnt signaling is dependent on LGR5, revealing a LGR5-dependent negative feedback mechanism.\",\n      \"method\": \"Co-immunoprecipitation, LGR5 knockdown, Wnt reporter assays, cell proliferation assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and KD with reporter assays, single lab\",\n      \"pmids\": [\"24476626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Lgr5 and Lgr4 promote formation of ultra-long actin-rich cytoneme-like membrane protrusions (exceeding 80 µm) by stabilizing nascent filopodia from a lamellipodial-like network; these cytonemes serve as conduits for transit of signaling effectors including myosin X (Myo10) and β-arrestin-2 (Arrb2).\",\n      \"method\": \"Live-cell imaging, overexpression of Lgr4/Lgr5, fluorescent reporter constructs for cargo tracking\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct live-cell imaging with functional cargo tracking, single lab\",\n      \"pmids\": [\"25653388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"LGR5/GPR49 overexpression activates the G12/13-Rho GTPase signaling pathway in a ligand-independent manner; LGR5-induced SRF-RE reporter activity is blocked by Rho inhibitor C3 transferase, RhoA-N19 mutant, and Gα12/13 knockdown. R-spondin ligands did not activate this Rho pathway in the presence of LGR5.\",\n      \"method\": \"SRF-RE luciferase reporter assay, dominant-negative mutants, siRNA knockdown of Gα12/13, LGR5 overexpression\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — multiple orthogonal approaches (reporter, dominant-negative, KD) but single lab\",\n      \"pmids\": [\"23912594\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The HECT-domain E3 ubiquitin ligases NEDD4 and NEDD4L are expressed in intestinal crypt stem cell regions and negatively regulate LGR5 receptor and DVL2 by targeting them for proteasomal and lysosomal degradation; loss of Nedd4/Nedd4l enhances ISC proliferation, increases sensitivity to R-spondin stimulation, and accelerates tumor development.\",\n      \"method\": \"Genetic deletion of Nedd4/Nedd4l, organoid assays, Western blotting for protein degradation, ApcMin tumor model\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function in vivo and in vitro with mechanistic follow-up (degradation pathway), single lab with multiple orthogonal methods\",\n      \"pmids\": [\"31867777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Unlike LGR4, full-length LGR5 does not interact with E3 ligases RNF43 or ZNRF3 (with or without RSPO), as shown by Co-IP, proximity ligation, competition binding, and time-resolved FRET assays; instead, LGR5 interacts with FZD and LRP6 of the Wnt signalosome to enhance LRP6 phosphorylation and potentiate Wnt/β-catenin signaling. Domain-swapping revealed the LGR4 seven-transmembrane domain confers E3 ligase interaction.\",\n      \"method\": \"Co-immunoprecipitation, proximity ligation assay, competition binding, time-resolved FRET, domain-swap mutagenesis\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — four orthogonal biochemical methods plus domain-swap mutagenesis in one rigorous study\",\n      \"pmids\": [\"33262293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"LGR4 forms a 2:2 homodimer complex with RNF43/ZNRF3 that accommodates bivalent RSPO binding, whereas LGR5 forms a homodimer that does not interact with these E3 ligases; monovalent and bivalent RSPO2 have nearly identical affinity for LGR5, in contrast to LGR4. Co-expression of ZNRF3 with LGR4 greatly increases monovalent RSPO affinity but has no effect when co-expressed with LGR5.\",\n      \"method\": \"Whole-cell binding affinity assays, co-immunoprecipitation, structural modeling\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — multiple binding assays and structural models, single lab\",\n      \"pmids\": [\"37402772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"LGR5 and LGR4 constitutively activate NF-κB signaling in a ligand-independent manner through their C-termini; the C-termini of LGR5/4 interact with the adaptor protein TROY, which is required for NF-κB activation. Overexpression of a C-terminal deletion mutant of LGR5 inhibits organoid growth and budding, while an R-spondin-binding-deficient mutant of LGR5 still promotes organoid growth via NF-κB.\",\n      \"method\": \"C-terminal deletion and binding-domain mutagenesis, luciferase NF-κB reporter, co-immunoprecipitation with TROY, intestinal organoid growth assays\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis, Co-IP, and functional organoid readout with multiple constructs, single lab\",\n      \"pmids\": [\"33001511\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"R-spondin1/LGR5 directly activates TGFβ signaling cooperatively with TGFβ type II receptor in colon cancer cells; upon RSPO1 stimulation, LGR5 forms complexes with TGFβ receptors, enhancing TGFβ-mediated growth inhibition and apoptosis. LGR5 knockdown attenuated downstream TGFβ signaling and increased metastasis in an orthotopic colon cancer model.\",\n      \"method\": \"Co-immunoprecipitation (LGR5-TGFβR complex), siRNA knockdown, orthotopic xenograft model, downstream signaling assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and in vivo KD model with functional readout, single lab\",\n      \"pmids\": [\"28939678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Wnt and R-spondin ligands have qualitatively distinct, non-interchangeable roles in Lgr5+ ISC self-renewal: Wnt proteins cannot induce ISC self-renewal but confer basal competency by maintaining RSPO receptor (LGR5) expression, while RSPO ligands actively drive stem-cell expansion. This was shown using a non-lipidated Wnt analogue and genetic/organoid approaches.\",\n      \"method\": \"In vivo genetic Wnt loss-of-function, non-lipidated Wnt analogue, RSPO gain-of-function, Lgr5+ ISC organoid culture, single-cell lineage tracing\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vivo and in vitro approaches, published in high-impact journal, functional dissection with synthetic ligands\",\n      \"pmids\": [\"28467820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Notch signaling is intrinsic to the gastric epithelium and is essential for homeostasis of LGR5+ antral stem cells; Notch inhibition reduces proliferation and induces mucous/endocrine differentiation, while constitutive Notch activation in LGR5+ stem cells induces gland fission and tissue expansion via mTORC1 signaling.\",\n      \"method\": \"Pharmacological Notch inhibition/activation, conditional Notch activation using Lgr5-Cre, gastric organoid culture, multicolor lineage tracing\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological approaches in vivo and in vitro with multiple orthogonal readouts in single rigorous study\",\n      \"pmids\": [\"26271103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Yap transiently reprograms Lgr5+ ISCs by suppressing Wnt signaling and excessive Paneth cell differentiation while promoting cell survival and inducing an Egf pathway regenerative program; Yap-deficient organoid growth is rescued by the Egfr ligand epiregulin, and Yap inactivation abolishes adenomas in Apc(Min) mice.\",\n      \"method\": \"Yap conditional knockout mice, irradiation injury model, organoid rescue assays with epiregulin, Apc(Min) tumor model\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic KO with multiple phenotypic and epistatic readouts, replicated across tissue injury and cancer models\",\n      \"pmids\": [\"26503053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"R-spondin-3 (Rspo3) secreted by myofibroblasts acts on basal Lgr5+ gastric stem cells to induce their differentiation into secretory cells expressing antimicrobial factors (e.g., intelectin-1), rather than promoting proliferation; depletion of Lgr5+ cells or Rspo3 knockout leads to hypercolonization of gastric glands with H. pylori.\",\n      \"method\": \"Lgr5+ cell depletion, Rspo3 conditional knockout in myofibroblasts, systemic Rspo3 administration, H. pylori colonization assays\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO and cell ablation in vivo with specific functional (antimicrobial/colonization) readout, multiple complementary approaches\",\n      \"pmids\": [\"31235935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"LGR5 expression in neuroblastoma cells regulates pro-survival MEK/ERK signaling independently of Wnt; siRNA-mediated LGR5 knockdown induces apoptosis accompanied by decreased phosphorylation of MEK1/2 and ERK1/2, increased BimEL, decreased Akt signaling via a Rictor-dependent PDK1-independent mechanism, and G1 cell-cycle arrest with increased p27.\",\n      \"method\": \"siRNA knockdown, Western blotting for MEK/ERK/Akt phosphorylation, cell cycle analysis, apoptosis assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — multiple signaling readouts from KD, single lab\",\n      \"pmids\": [\"26517508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"LGR5 undergoes rapid, constitutive internalization independent of ligand, and LGR5-high cancer cells exhibit properties of tumor-initiating/cancer stem cells; LGR5-targeting antibody-drug conjugates internalize to lysosomes of LGR5-expressing cells and induce cytotoxicity specifically in LGR5-high but not LGR5-negative or LGR5-knockdown cells.\",\n      \"method\": \"Receptor binding assays, cell internalization assays, cytotoxicity assays, xenograft tumor model\",\n      \"journal\": \"Molecular cancer therapeutics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct internalization assay with functional (cytotoxicity) readout, single lab\",\n      \"pmids\": [\"27207778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"IL-17A signaling through IL-17RA in Lgr5+ intestinal stem cells induces expression of transcription factor ATOH1 to promote secretory epithelial cell lineage commitment; multiple conditional deletion models demonstrated that Paneth, tuft, goblet, and enteroendocrine cell numbers were dependent on this IL-17A/ATOH1 axis specifically in Lgr5+ cells.\",\n      \"method\": \"Multiple conditional deletion mouse models (Lgr5-Cre, ATOH1-Cre), human intestinal organoid stimulation with IL-17A\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple conditional genetic models with specific cellular phenotypes, complemented by human organoid experiments\",\n      \"pmids\": [\"35081371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"NOD2 agonist MDP protects Lgr5+ intestinal stem cells against oxidative stress-induced death via mitophagy; MDP-induced cytoprotection requires both NOD2 and ATG16L1; the mechanism involves NOD2-dependent reduction of mitochondrial ROS through mitophagy induction, independent of NF-κB.\",\n      \"method\": \"ATG16L1 and NOD2 knockout organoids, irradiation stress model, ROS measurement, mitophagy quantification in vivo and in vitro\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO of two pathway components with mechanistic ROS/mitophagy readouts in vivo and in vitro, single lab\",\n      \"pmids\": [\"31919280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"IKKα binds directly to the LGR5 promoter in basal cell carcinoma cells and upregulates LGR5 expression through activation of the STAT3 signaling pathway; STAT3 and IKKα interact functionally to drive LGR5 expression during BCC cancer progression.\",\n      \"method\": \"ChIP assay (IKKα at LGR5 promoter), STAT3 pathway inhibition, IKKα knockdown, tumor growth assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — ChIP and KD with functional readout, single lab\",\n      \"pmids\": [\"27049829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SOX9 directly transcriptionally upregulates LGR5 expression in glioblastoma cells; knockdown of SOX9 suppresses LGR5 expression, proliferation, and tumorigenicity of glioblastoma cells, establishing a SOX9-LGR5 regulatory axis.\",\n      \"method\": \"SOX9 knockdown, luciferase reporter (LGR5 promoter), ChIP, LGR5 KD functional assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — transcriptional regulation assays with promoter reporter and ChIP, single lab\",\n      \"pmids\": [\"25770425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"LGR5 knockdown in human pluripotent stem cells (hPSCs) reduces cardiomyocyte-associated markers and impairs cardiac differentiation, while promoting endothelial cell differentiation with increased nuclear translocation of β-catenin and upregulation of Wnt signaling-related genes, indicating LGR5 modulates hPSC lineage fate through Wnt/β-catenin regulation.\",\n      \"method\": \"LGR5 siRNA knockdown during hPSC differentiation, qRT-PCR, immunostaining, functional tube formation and LDL uptake assays\",\n      \"journal\": \"Stem cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — KD with multiple differentiation readouts, single lab\",\n      \"pmids\": [\"28793247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"LGR5+ colorectal cancer stem cells are mechanically stiffer, adhere better to ECM, move slower, display higher nuclear YAP, and form larger transendothelial gaps compared to LGR5- cells; these differences are largely explained by downregulation of membrane-to-cortex attachment proteins Ezrin/Radixin/Moesin (ERMs) in LGR5+ cells.\",\n      \"method\": \"Patient-derived organoids, single-cell RNA-seq, atomic force microscopy, live-cell imaging, ERM knockdown/overexpression\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (mechanical measurements, genomics, functional rescue) linking ERM downregulation mechanistically to LGR5+ cell properties\",\n      \"pmids\": [\"38637494\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Loss of LGR5 expression (through chemotherapy, LGR5-targeted ADC treatment, or gene ablation) in colorectal cancer cells activates STAT3 via increased MET (mesenchymal-epithelial transition factor) receptor activity; LGR5 overexpression decreased MET-STAT3 activity, and STAT3 inhibition suppressed MET phosphorylation, suggesting a feedback mechanism between LGR5, MET, and STAT3.\",\n      \"method\": \"LGR5 gene ablation, LGR5 overexpression, Western blotting, MET/STAT3 inhibition, tumor organoids and xenograft model\",\n      \"journal\": \"Molecular cancer therapeutics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple complementary approaches (KO, OE, inhibitors, in vivo) in single lab\",\n      \"pmids\": [\"36921315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Quiescent (slow-cycling) LGR5+p27+ cells exist in the human colon and display lineage-forming capability in vivo; TGFβ signaling regulates the quiescent state of these LGR5+ cells, as shown by orthotopic xenotransplantation and lineage tracing of LGR5-tdTomato/LGR5-iCaspase9 knock-in human colon organoids.\",\n      \"method\": \"Single-cell RNA-seq, genome-engineered human organoid knock-ins (LGR5-tdTomato, LGR5-iCaspase9, p27-mVenus), orthotopic xenotransplantation, EdU pulse-chase, TGFβ pathway manipulation\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genome-engineered reporter lines with in vivo transplantation and pathway manipulation, single rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"35963362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"REGγ enhances transcriptional activation of Lgr5 via potentiation of both Wnt and Hippo signaling pathways; TEAD4 alone or cooperating with TCF4 directly enhances Lgr5 expression, and silencing TEAD4 drastically attenuates β-catenin/TCF4-dependent Lgr5 expression. Conditional ablation of REGγ in Lgr5+ stem cells impairs intestinal crypt proliferation and delays regeneration after irradiation.\",\n      \"method\": \"Conditional REGγ knockout in Lgr5+ cells, TEAD4 and TCF4 co-transfection/silencing, luciferase reporter assays for Lgr5 promoter, irradiation injury model\",\n      \"journal\": \"Science China. Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — conditional KO with mechanistic promoter assays, single lab\",\n      \"pmids\": [\"34826093\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"LGR5 is a seven-transmembrane leucine-rich repeat-containing G-protein-coupled receptor that serves as the cell-surface receptor for R-spondin ligands; upon R-spondin binding it potentiates Wnt/β-catenin signaling by forming a complex with Wnt co-receptors FZD and LRP6 to enhance LRP6 phosphorylation (without sequestering E3 ligases RNF43/ZNRF3 as LGR4 does), and independently activates NF-κB signaling via its C-terminus through TROY, as well as G12/13-Rho GTPase signaling; LGR5 is post-translationally regulated by NEDD4/NEDD4L-mediated proteasomal and lysosomal degradation, constitutively internalizes via clathrin/dynamin, drives formation of actin-rich cytoneme-like protrusions, and marks multipotent self-renewing adult stem cells in intestinal crypts, stomach, liver, hair follicle, and other tissues where it is a Wnt target gene maintaining stem cell identity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"LGR5 is a seven-transmembrane R-spondin receptor that marks and maintains multipotent, self-renewing adult stem cells, defined originally as the cycling crypt base columnar cells that regenerate all intestinal epithelial lineages and self-organize into crypt-villus organoids from single cells [#0, #1]. Mechanistically, R-spondin-bound LGR5 forms a supercomplex with the Wnt co-receptors FZD5 and LRP6 to enhance LRP6 phosphorylation and potentiate Wnt/\\u03b2-catenin signaling [#4, #10]; this complex internalizes via clathrin/dynamin, but endocytosis is dispensable for signaling, as C-terminal truncation increases activity while reducing internalization [#4, #19]. Within the Wnt module, the R-spondin/LGR5 interaction tunes signal strength by neutralizing the transmembrane E3 ligases RNF43/ZNRF3 that remove Wnt receptors, yet unlike its paralog LGR4, full-length LGR5 does not itself bind RNF43/ZNRF3\\u2014a distinction conferred by the seven-transmembrane domain [#5, #10, #11]. Beyond Wnt potentiation, LGR5 engages additional outputs: its C-terminus drives ligand-independent, TROY-dependent NF-\\u03baB activation that supports organoid growth, and it activates G12/13-Rho-SRF signaling and shapes actin-rich cytoneme-like protrusions [#12, #8, #7]. LGR5 receptor abundance is constrained post-translationally by NEDD4/NEDD4L-mediated proteasomal and lysosomal degradation, loss of which heightens R-spondin sensitivity and accelerates tumorigenesis [#9]. In tissue, LGR5+ stem cell behavior is governed by niche inputs\\u2014Paneth-cell-derived signals, Notch, YAP, IL-17A/ATOH1, and distinct Wnt versus R-spondin roles\\u2014that couple self-renewal to differentiation and regeneration [#2, #15, #16, #20, #14], and LGR5 expression is itself a transcriptional output of Wnt/Hippo and other regulators [#28].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that LGR5 is not just a Wnt target but a functional marker of bona fide adult stem cells, answering what cell population sustains the intestinal epithelium.\",\n      \"evidence\": \"Inducible Cre knock-in lineage tracing in mouse intestine in vivo\",\n      \"pmids\": [\"17934449\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not define LGR5's biochemical signaling activity\", \"Marker function does not establish whether LGR5 protein is required for stemness\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed LGR5+ cells are intrinsically multipotent and niche-independent for organization, by reconstituting crypt-villus organoids from single sorted cells.\",\n      \"evidence\": \"Single-cell sorting and 3D organoid culture in vitro\",\n      \"pmids\": [\"19329995\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Culture requires exogenous Wnt/R-spondin/EGF, so cell-autonomous signaling roles remain unresolved\", \"Does not address LGR5 receptor mechanism\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined the cellular niche and population dynamics of LGR5+ stem cells, establishing Paneth cells as signal providers and symmetric neutral-drift division as the renewal mode.\",\n      \"evidence\": \"Genetic Paneth ablation, co-culture, and multicolor clonal fate mapping in vivo\",\n      \"pmids\": [\"21113151\", \"20887898\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Niche signals identified are paracrine ligands, not LGR5-direct receptor events\", \"Does not connect division dynamics to LGR5 signaling output\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Resolved how LGR5 acts within the Wnt machinery, showing it forms an internalizing LRP6/FZD5 supercomplex but that endocytosis is uncoupled from \\u03b2-catenin potentiation.\",\n      \"evidence\": \"Co-IP, endocytosis inhibitors, C-terminal deletion, Wnt luciferase reporters\",\n      \"pmids\": [\"22473993\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which the complex enhances LRP6 phosphorylation not detailed here\", \"Role of the C-terminal tail in negative regulation left open\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified a Wnt-independent LGR5 output, showing ligand-independent G12/13-Rho-SRF activation.\",\n      \"evidence\": \"SRF-RE reporter, dominant-negative RhoA/G12-13, siRNA knockdown, overexpression\",\n      \"pmids\": [\"23912594\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relies on overexpression; physiological relevance in stem cells untested\", \"Single lab, no in vivo confirmation\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Placed LGR5 mechanistically as the receptor that tunes Wnt signal strength via the R-spondin/RNF43/ZNRF3 feedback loop.\",\n      \"evidence\": \"Receptor-ligand and E3-ligase neutralization biochemistry; Co-IP and reporter assays in cancer cells\",\n      \"pmids\": [\"24532711\", \"24476626\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LGR5 itself binds the E3 ligases was not yet distinguished from paralogs\", \"Context-dependent positive vs negative effects unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Extended LGR5 cell biology to membrane morphology and gastric/niche regulation, linking it to cytoneme formation and Notch-dependent gastric stem cell homeostasis.\",\n      \"evidence\": \"Live-cell imaging of cytonemes; Notch manipulation with Lgr5-Cre and gastric organoids\",\n      \"pmids\": [\"25653388\", \"26271103\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cytoneme function based on overexpression imaging\", \"Notch acts on LGR5+ cells but not via LGR5 receptor itself\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Dissected non-interchangeable Wnt vs R-spondin roles and identified TGF\\u03b2 cross-talk, showing Wnt maintains LGR5 expression/competency while R-spondin drives expansion, and LGR5 can couple to TGF\\u03b2 receptors.\",\n      \"evidence\": \"Synthetic non-lipidated Wnt analogue, RSPO gain-of-function, lineage tracing; LGR5-TGF\\u03b2R Co-IP with orthotopic model\",\n      \"pmids\": [\"28467820\", \"28939678\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"TGF\\u03b2 coupling shown in cancer cells (Medium); generality to normal stem cells unclear\", \"Molecular basis of LGR5-TGF\\u03b2R complex undefined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined post-translational control of LGR5, showing NEDD4/NEDD4L degrade the receptor to restrain R-spondin sensitivity and tumorigenesis.\",\n      \"evidence\": \"Genetic Nedd4/Nedd4l deletion, organoid assays, degradation Western blots, ApcMin model\",\n      \"pmids\": [\"31867777\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitination sites on LGR5 not mapped\", \"Balance between proteasomal and lysosomal routes unresolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Mechanistically separated LGR5 from LGR4, establishing that LGR5 does not bind RNF43/ZNRF3 but instead enhances LRP6 phosphorylation, and that its C-terminus drives TROY-dependent NF-\\u03baB signaling.\",\n      \"evidence\": \"Co-IP, PLA, competition binding, TR-FRET, domain-swap mutagenesis; NF-\\u03baB reporter and TROY Co-IP with organoid growth assays\",\n      \"pmids\": [\"33262293\", \"33001511\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the 7TM domain selects against E3-ligase binding not structurally resolved\", \"NF-\\u03baB branch validated in single lab (Medium)\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Provided structural-level rationale for paralog divergence, showing LGR4 forms a 2:2 complex with RNF43/ZNRF3 enabling bivalent RSPO sensing while LGR5 homodimers do not.\",\n      \"evidence\": \"Whole-cell binding affinity assays, Co-IP, structural modeling\",\n      \"pmids\": [\"37402772\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental high-resolution structure of LGR5 complexes\", \"Functional consequence of monovalent/bivalent equivalence in LGR5 stem cells untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Connected LGR5+ identity to mechanical and metastatic cancer-stem-cell phenotypes through ERM downregulation.\",\n      \"evidence\": \"Patient-derived organoids, scRNA-seq, atomic force microscopy, ERM knockdown/overexpression\",\n      \"pmids\": [\"38637494\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ERM downregulation is downstream of LGR5 signaling per se is not established\", \"Link to specific LGR5 signaling branch (Wnt/NF-\\u03baB/Rho) undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how LGR5's multiple signaling outputs (Wnt potentiation, NF-\\u03baB, G12/13-Rho, TGF\\u03b2 coupling) are integrated and balanced within a single stem cell to control self-renewal versus differentiation.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural model of LGR5 distinguishing its branch-specific conformations\", \"Quantitative contribution of each branch to stem-cell maintenance in vivo unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [4, 5, 10]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [5, 11]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 5, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4, 10, 19]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4, 19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 5, 10, 12, 8]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 1, 14]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [9, 25, 26]}\n    ],\n    \"complexes\": [\"Wnt signalosome (LGR5-FZD5-LRP6)\"],\n    \"partners\": [\"RSPO1\", \"RSPO2\", \"LRP6\", \"FZD5\", \"RNF43\", \"ZNRF3\", \"TROY\", \"NEDD4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}