{"gene":"FZD5","run_date":"2026-04-28T17:46:04","timeline":{"discoveries":[{"year":2001,"finding":"Fzd5 knockout mice die in utero around E10.75 due to defects in yolk sac and placental angiogenesis, with markedly reduced endothelial cell proliferation (BrdU labeling); Fzd5 specifically synergized with Wnt2, Wnt5a, and Wnt10b in ectopic axis induction assays in Xenopus embryos, establishing Fzd5 as a Wnt receptor required for vascular development.","method":"Homologous recombination knockout mice, BrdU proliferation assay, Xenopus axis induction assay","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 1–2 — genetic knockout with defined cellular phenotype, replicated across multiple assays","pmids":["11092808"],"is_preprint":false},{"year":2003,"finding":"WNT7A signals through a FZD5·LRP6 receptor complex in PC12 cells to increase β-catenin stability and activate TCF-based transcription; this activity is antagonized by Dickkopf-1 and Dickkopf-3.","method":"TCF-luciferase reporter assay, β-catenin stability assay, functional epistasis with Dickkopf proteins in PC12 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple functional assays in cell lines establishing receptor complex composition and pathway position","pmids":["12857724"],"is_preprint":false},{"year":2008,"finding":"Purified Wnt7a binds to the extracellular cysteine-rich domain (CRD) of Fzd5 with nanomolar affinity, as shown by ELISA-based protein-protein binding assay; a split-eGFP complementation assay confirmed Wnt7a–Fzd5 interaction and subsequent canonical pathway activation in cells.","method":"ELISA-based binding assay, split-eGFP complementation assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1–2 — direct binding assay with purified proteins, single study","pmids":["18230341"],"is_preprint":false},{"year":2009,"finding":"CVAK104 is a novel binding partner of both Dishevelled (Dvl) and FZD5 (but not FZD1 or FZD4); CVAK104 selectively induces clathrin-mediated internalization of FZD5 and its subsequent lysosomal degradation, thereby suppressing Wnt/β-catenin signaling; knockdown of CVAK104 increases FZD5 protein levels and activates Wnt signaling.","method":"Co-immunoprecipitation, dominant-negative Rab5, siRNA knockdown, lysosome inhibitor assay, β-catenin reporter assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP, genetic perturbations, multiple orthogonal assays in one study","pmids":["19643732"],"is_preprint":false},{"year":2013,"finding":"A positive feedback loop between Gcm1 and Fzd5 is essential for chorionic branching morphogenesis: Gcm1 upregulates Fzd5 at branching initiation sites, and elevated Fzd5 via nuclear β-catenin signaling maintains Gcm1 expression; Fzd5-mediated signaling also induces disassembly of cell junctions (downregulation of ZO-1, claudin 4, claudin 7) and upregulates Vegf in trophoblast cells.","method":"Global and trophoblast-specific Fzd5/Gcm1 knockout mice, trophoblast stem cell lines, tetraploid aggregation assay","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic models (global + conditional KO), epistasis, specific cellular phenotypes","pmids":["23610556"],"is_preprint":false},{"year":2014,"finding":"Monocyte-secreted Wnt5a activates FZD5 in microvascular endothelial cells (mECs) through non-canonical signaling: FZD5 activation triggers intracellular Ca2+ release, NFκB transcriptional activity, and tissue factor (TF) gene expression, leading to angiogenesis via autocrine TF regulation.","method":"In vitro co-culture paracrine assay, intracellular Ca2+ measurement, NFκB reporter, TF expression, in vivo microvessel formation","journal":"Journal of molecular cell biology","confidence":"Medium","confidence_rationale":"Tier 2–3 — defined signaling cascade, multiple assays, single lab","pmids":["25240054"],"is_preprint":false},{"year":2016,"finding":"A heterozygous frameshift mutation in FZD5 (p.Ala219Glufs*49) produces a truncated protein that retains the WNT-ligand-binding CRD but lacks the transmembrane domain; the truncated protein is secreted from cells and acts as a dominant-negative receptor, antagonizing both canonical and non-canonical WNT signaling and causing coloboma and microphthalmia in zebrafish.","method":"Cell secretion assay, WNT signaling reporter assays, zebrafish injection, mouse retinal epithelium analysis","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1–2 — molecular characterization of mutant protein, multiple model organisms, loss-of-function phenotype","pmids":["26908622"],"is_preprint":false},{"year":2016,"finding":"Genome-wide CRISPR-Cas9 screens in RNF43-mutant pancreatic ductal adenocarcinoma (PDAC) cells identify a specific requirement for FZD5 (not other Frizzled receptors) for Wnt-dependent proliferation; anti-FZD5 antibodies inhibit RNF43-mutant PDAC and colorectal cancer organoid growth in vitro and in vivo, confirming FZD5 receptor-level specificity.","method":"Genome-wide CRISPR-Cas9 dropout screen, recombinant antibodies, xenograft, patient-derived organoids","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 1–2 — CRISPR screen validated by orthogonal antibody inhibition in multiple cancer models","pmids":["27869803"],"is_preprint":false},{"year":2018,"finding":"FZD5 functions as a prototypical GPCR: WNT-5A stimulation induces a conformational change in FZD5 reminiscent of class A/B GPCR activation, and FZD5 activates Gαq and its downstream effectors, as measured by live-cell dcFRAP and resonance energy transfer (RET)-based assays.","method":"Dual-color FRAP (dcFRAP), BRET/FRET resonance energy transfer assays, Gαq activation assays","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1–2 — multiple spectrometric and live-cell imaging methods demonstrating G-protein coupling, single rigorous study","pmids":["30514810"],"is_preprint":false},{"year":2018,"finding":"Surface plasmon resonance analysis demonstrates that WNT5A binds FZD5 with ~30% stronger response than to RYK; FZD5 knockdown completely abrogates the anti-proliferative effect of WNT5A in PC3 prostate cancer cells, whereas RYK knockdown preferentially mediates the pro-apoptotic effect.","method":"Surface plasmon resonance, siRNA knockdown, proliferation and apoptosis assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 — direct binding measurement and receptor-specific knockdown, single lab","pmids":["29930766"],"is_preprint":false},{"year":2018,"finding":"Loss of Fzd5 in endothelial cells causes G0/G1 cell cycle arrest and reduced migration; Fzd5 knockdown enhances PKC signaling and PKC/Ets1-mediated transcription of Angpt2 and Flt1, independently of canonical Wnt, NFAT, and JNK pathways.","method":"siRNA knockdown, 3D collagen co-culture, cell cycle analysis, PKC inhibition, Ets1 transcription factor assay","journal":"Angiogenesis","confidence":"Medium","confidence_rationale":"Tier 2 — defined pathway (PKC/Ets1) with pharmacological and genetic dissection, single lab","pmids":["29845518"],"is_preprint":false},{"year":2018,"finding":"WNT5A activates FZD5 to stimulate FZD5/PKC signaling, which is responsible for P-glycoprotein upregulation and multidrug resistance in renal cell carcinoma; FZD5 silencing reverses Wnt-5a-induced phosphorylation of PKCα/βII and CaMKII.","method":"siRNA knockdown, miR-124 mimic, luciferase 3'UTR assay, western blot for p-PKCα/βII and p-CaMKII","journal":"Tumour biology","confidence":"Medium","confidence_rationale":"Tier 3 — defined signaling cascade with siRNA and pharmacological tools, single lab","pmids":["25861751"],"is_preprint":false},{"year":2020,"finding":"YTHDF1 promotes FZD5 mRNA translation in an m6A-dependent manner, activating the WNT/β-catenin pathway in hepatocellular carcinoma; multi-omics (ribosome profiling + m6A-seq) revealed YTHDF1 accelerates translational output specifically from FZD5 mRNA.","method":"m6A-seq, ribosome profiling, YTHDF1 knockdown/overexpression, WNT/β-catenin pathway reporters","journal":"Molecular therapy. Nucleic acids","confidence":"Medium","confidence_rationale":"Tier 2 — multi-omics orthogonal approaches establishing m6A-dependent translational regulation, single lab","pmids":["33230473"],"is_preprint":false},{"year":2020,"finding":"FZD5 promotes TNBC cell G1/S transition, DNA damage repair, and stemness through a signaling axis that activates transcription factor FOXM1, which in turn transcribes BRCA1 and BIRC5; WNT7B was identified as a specific ligand mediating these FZD5-dependent effects.","method":"Loss/gain-of-function studies, FOXM1 overexpression rescue, ChIP for FOXM1 on BRCA1/BIRC5 promoters","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — epistasis rescue experiment and ChIP, single lab","pmids":["33311446"],"is_preprint":false},{"year":2020,"finding":"FZD5 knockdown in hMSCs promotes cellular senescence via the noncanonical Wnt pathway, as shown by increased senescence markers; FZD5 overexpression delays cell cycle arrest during prolonged culture; WNT5A treatment of FZD5-expressing cells promotes proliferation.","method":"siRNA knockdown, FZD5 overexpression, senescence marker assays, proliferation assays","journal":"Stem cells (Dayton, Ohio)","confidence":"Medium","confidence_rationale":"Tier 2 — loss and gain of function with defined phenotype in primary human cells, single lab","pmids":["33338299"],"is_preprint":false},{"year":2021,"finding":"In cardiac fibroblasts, Wnt5a or Wnt11 increases FZD5 expression and activates EGFR phosphorylation; si-FZD5 suppresses increased p-EGFR and fibrotic signaling (p-p38, p-ERK), establishing a crosstalk loop between FZD5 and EGFR in cardiac fibrosis under pressure overload.","method":"siRNA knockdown, western blot, TAC mouse model, conditional medium experiments","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2–3 — in vitro and in vivo genetic perturbations showing FZD5-EGFR crosstalk, single lab","pmids":["34564708"],"is_preprint":false},{"year":2021,"finding":"FZD5 prevents epithelial-mesenchymal transition (EMT) in gastric cancer through a PKC–ELF3–ZEB1 axis: FZD5 activates PKC, which induces ELF3 expression; ELF3 represses ZEB1 to block EMT; FZD5 requires co-receptor LRP5, and WNT7B is a putative FZD5 ligand in this context; FZD5 is negatively regulated by transcription factors SNAI2 and TEAD1 (ChIP).","method":"Loss/gain-of-function, ChIP-PCR, PKC inhibitor, migration assay, E-cadherin/Vimentin/ZEB1 western blot","journal":"Cell communication and signaling : CCS","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP and epistasis with multiple pathway components, single lab","pmids":["33618713"],"is_preprint":false},{"year":2022,"finding":"WNT5A signals through FZD5 and co-receptor LRP5 to regulate proliferation and self-renewal of endometrial mesenchymal stem-like cells (eMSC) via WNT/β-catenin; anti-FZD5 antibody and FZD5 gene silencing reduce WNT5A binding to eMSC, TCF/LEF transcriptional activity, and active β-catenin levels.","method":"Anti-FZD5 neutralizing antibody, FZD5 siRNA, TCF/LEF reporter, co-culture, Dickkopf-1 LRP inhibition","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 — receptor knockdown and antibody blockade with functional and molecular readouts, single lab","pmids":["35295855"],"is_preprint":false},{"year":2023,"finding":"Desert lncRNA HIDEN interacts with RNA-binding protein IMP1 (IGF2BP1); HIDEN depletion reduces the IMP1–FZD5 mRNA interaction and destabilizes FZD5 mRNA, reducing WNT activity and impairing human definitive endoderm differentiation; WNT agonist rescues differentiation deficiency caused by HIDEN or IMP1 loss.","method":"shRNA/promoter deletion of HIDEN, RNA immunoprecipitation (RIP), mRNA stability assay, WNT reporter, endoderm differentiation assay","journal":"Genome biology","confidence":"Medium","confidence_rationale":"Tier 2 — RIP and mRNA stability assay establish HIDEN/IMP1-mediated FZD5 mRNA stabilization, single lab","pmids":["37095549"],"is_preprint":false},{"year":2023,"finding":"Single-cell transcriptomics and functional approaches identify an endogenous WNT7A-FZD5 signaling axis as critical for fallopian tube stem cell renewal, with WNT/β-catenin pathway-activated cells forming a distinct transcriptomic cluster enriched in ECM remodeling and integrin signaling.","method":"Single-cell RNA-seq, WNT/β-catenin reporter organoids, functional knockdown/antibody blocking, bulk transcriptomics","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 — functional organoid assays combined with single-cell transcriptomics, single lab","pmids":["37917586"],"is_preprint":false},{"year":2024,"finding":"FZD5 is specifically upregulated in anterior neural progenitor cells; its expression is downregulated as cells adopt posterior fate; stimulation of a tetravalent antibody that selectively clusters FZD5 and LRP6 activates WNT/β-catenin signaling and drives midbrain progenitor differentiation into functional dopaminergic neurons in vitro and in vivo.","method":"Cell surface FZD receptor profiling, agonist antibody (FZD5/LRP6 clustering), hPSC differentiation, dopaminergic neuron functional assays, in vivo transplantation","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 1–2 — receptor-specific agonist antibody with functional readout in multiple systems, single rigorous study","pmids":["38358799"],"is_preprint":false},{"year":2025,"finding":"Wnt ligands specifically induce FZD5 (and FZD8) endocytosis and lysosomal degradation in a ZNRF3/RNF43-dependent manner; ZNRF3/RNF43 selectively target FZD5/8 but not other FZDs for degradation upon Wnt stimulation; Wnt promotes the physical interaction between FZD5 and RNF43; RSPO1 enhances Wnt signaling by specifically stabilizing FZD5/8; DVL promotes ligand-independent FZD endocytosis but is dispensable for Wnt-induced FZD5/8 degradation.","method":"Endocytosis and degradation assays, co-immunoprecipitation (FZD5–RNF43 interaction), RSPO1 stabilization assay, DVL loss-of-function, receptor-selective degradation profiling","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods, direct interaction between FZD5 and RNF43 shown, mechanistic pathway dissection","pmids":["41070826"],"is_preprint":false},{"year":2024,"finding":"DNMT3A binds the FZD5 promoter to suppress its transcription via DNA methylation; reduced DNMT3A expression in NSCLC leads to FZD5 promoter hypomethylation and aberrant FZD5 upregulation; DNMT3A overexpression suppresses urethane-induced lung carcinogenesis and malignant cell behavior.","method":"Chromatin immunoprecipitation (ChIP) for DNMT3A at FZD5 promoter, quantitative methylation-specific PCR, lentiviral FZD5 silencing, mouse lung carcinogenesis model","journal":"Heliyon","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP confirms DNMT3A binding to FZD5 promoter with functional in vivo validation, single lab","pmids":["38707304"],"is_preprint":false}],"current_model":"FZD5 is a seven-transmembrane class F GPCR that functions as a Wnt receptor (primary ligands include WNT5A, WNT7A, WNT7B, WNT2, and WNT10b), forming complexes with co-receptors LRP5/LRP6 to activate canonical WNT/β-catenin signaling; it also couples to Gαq to trigger non-canonical Ca2+/CaMKII and PKC pathways; its surface levels are regulated by CVAK104-mediated clathrin/lysosomal degradation and by Wnt-induced, ZNRF3/RNF43-dependent endocytosis that is antagonized by RSPO1; its transcription is suppressed by DNMT3A-mediated promoter methylation and its mRNA is stabilized by the HIDEN lncRNA/IMP1 complex; FZD5 is required for yolk sac and placental angiogenesis, neural anterior-posterior patterning (dopaminergic neuron specification), optic fissure closure, chorionic branching morphogenesis, and stem cell maintenance, and is specifically essential for Wnt-dependent proliferation of RNF43-mutant cancers."},"narrative":{"teleology":[{"year":2001,"claim":"Establishing that FZD5 is a Wnt receptor essential for embryonic vascular development resolved the question of whether Frizzled-5 has a non-redundant developmental role.","evidence":"Fzd5 knockout mice showed embryonic lethality at E10.75 from yolk sac/placental angiogenesis failure; Xenopus axis induction confirmed ligand selectivity (Wnt2, Wnt5a, Wnt10b)","pmids":["11092808"],"confidence":"High","gaps":["Downstream intracellular signaling pathway not resolved","Co-receptor requirements not determined"]},{"year":2003,"claim":"Demonstration that FZD5 forms a complex with LRP6 to activate β-catenin/TCF signaling positioned FZD5 within the canonical Wnt pathway and identified its co-receptor.","evidence":"TCF-luciferase and β-catenin stability assays in PC12 cells with WNT7A, antagonized by Dkk1/Dkk3","pmids":["12857724"],"confidence":"High","gaps":["Direct physical binding affinity between WNT7A and FZD5 not measured","Non-canonical signaling not addressed"]},{"year":2008,"claim":"Quantifying nanomolar-affinity binding of WNT7A to the FZD5 CRD established the biophysical basis for ligand-receptor selectivity.","evidence":"ELISA-based binding with purified proteins and split-eGFP complementation","pmids":["18230341"],"confidence":"Medium","gaps":["Binding affinities for other WNT ligands not compared side-by-side","Structural basis for selectivity unknown"]},{"year":2009,"claim":"Identification of CVAK104 as a selective internalization partner for FZD5 revealed that receptor surface levels are actively regulated by clathrin-mediated endocytosis and lysosomal degradation, tuning Wnt signal strength.","evidence":"Co-IP of CVAK104 with FZD5 (not FZD1/FZD4), dominant-negative Rab5, lysosome inhibitors, siRNA","pmids":["19643732"],"confidence":"High","gaps":["Physiological contexts where CVAK104-mediated FZD5 turnover is rate-limiting not established","Whether post-translational modifications gate CVAK104 binding unknown"]},{"year":2013,"claim":"Discovery of a Gcm1–FZD5 positive feedback loop in trophoblast cells explained how FZD5 drives chorionic branching morphogenesis through β-catenin-mediated junction remodeling and VEGF induction.","evidence":"Global and trophoblast-specific Fzd5/Gcm1 knockout mice, trophoblast stem cell lines, tetraploid aggregation","pmids":["23610556"],"confidence":"High","gaps":["Whether FZD5 signals through canonical or non-canonical Wnt in trophoblasts not fully dissected","Ligand identity in placenta not definitively assigned"]},{"year":2014,"claim":"Showing that WNT5A–FZD5 triggers intracellular Ca²⁺ release, NFκB activation, and tissue factor expression in endothelial cells established a non-canonical signaling branch distinct from β-catenin.","evidence":"Paracrine co-culture, Ca²⁺ imaging, NFκB reporter, TF expression, microvessel assay","pmids":["25061751"],"confidence":"Medium","gaps":["G-protein coupling not directly measured in this system","Contribution relative to canonical pathway not quantified"]},{"year":2016,"claim":"Two advances defined FZD5 disease relevance: a dominant-negative FZD5 truncation was shown to cause coloboma/microphthalmia, and CRISPR screening identified FZD5 as specifically essential in RNF43-mutant cancers, establishing therapeutic targeting rationale.","evidence":"Secreted truncated FZD5 (p.Ala219Glufs*49) antagonized WNT in zebrafish; genome-wide CRISPR dropout screen in PDAC plus anti-FZD5 antibody validation in organoids/xenografts","pmids":["26908622","27869803"],"confidence":"High","gaps":["Genotype–phenotype spectrum of FZD5 mutations in humans not fully mapped","Mechanism of FZD5 selectivity in RNF43-mutant cancers versus other FZDs not resolved"]},{"year":2018,"claim":"Biophysical demonstration that WNT5A induces a GPCR-like conformational change in FZD5 and activates Gαq established Frizzled receptors as bona fide GPCRs, not just scaffold receptors.","evidence":"dcFRAP and BRET/FRET assays for Gαq coupling in live cells","pmids":["30514810"],"confidence":"High","gaps":["Whether Gαq coupling occurs at endogenous FZD5 expression levels not shown","Structural basis for Gαq selectivity over other Gα subunits unknown"]},{"year":2018,"claim":"Dissection of FZD5 downstream signaling in endothelial cells and renal carcinoma showed that FZD5 restrains PKC/Ets1-driven Angpt2/Flt1 transcription and mediates WNT5A-induced PKCα/βII and CaMKII phosphorylation, expanding the non-canonical effector repertoire.","evidence":"siRNA, PKC inhibitors, Ets1 assays in endothelial cells; siRNA and phospho-western blots in renal carcinoma","pmids":["29845518","25861751"],"confidence":"Medium","gaps":["Whether PKC and CaMKII are activated in parallel or sequentially downstream of FZD5 not determined","Direct versus indirect PKC activation not resolved"]},{"year":2020,"claim":"Identification of YTHDF1-mediated m6A-dependent translational enhancement of FZD5 mRNA and the WNT7B–FZD5–FOXM1 axis in cancer expanded understanding of FZD5 post-transcriptional regulation and downstream transcriptional targets.","evidence":"m6A-seq, ribosome profiling, YTHDF1 perturbation in HCC; ChIP for FOXM1 on BRCA1/BIRC5 promoters in TNBC","pmids":["33230473","33311446"],"confidence":"Medium","gaps":["Whether m6A regulation of FZD5 mRNA operates in non-cancer contexts unknown","Direct interaction between YTHDF1 and FZD5 mRNA not shown by CLIP"]},{"year":2023,"claim":"Discovery that the lncRNA HIDEN scaffolds IMP1 onto FZD5 mRNA to stabilize it revealed a non-coding RNA layer of FZD5 regulation critical for endoderm differentiation, while single-cell data identified WNT7A–FZD5 as the key stem cell renewal axis in fallopian tube organoids.","evidence":"RIP, mRNA stability assay, WNT reporter rescue in hESC endoderm differentiation; scRNA-seq and functional organoid assays in fallopian tube","pmids":["37095549","37917586"],"confidence":"Medium","gaps":["Structural basis of HIDEN–IMP1–FZD5 mRNA complex not defined","Whether FZD5 is the sole Frizzled mediating fallopian tube stemness not excluded"]},{"year":2024,"claim":"Selective upregulation of FZD5 in anterior neural progenitors and its functional sufficiency to drive dopaminergic neuron specification via a tetravalent agonist antibody clustering FZD5/LRP6 established FZD5 as a regional Wnt signal interpreter during neural patterning.","evidence":"Cell-surface FZD profiling, agonist antibody, hPSC-derived midbrain progenitor differentiation, in vivo transplantation","pmids":["38358799"],"confidence":"High","gaps":["Endogenous ligand driving FZD5 in midbrain specification in vivo not definitively identified","Whether FZD5 agonist antibody activates non-canonical pathways not assessed"]},{"year":2025,"claim":"Mechanistic dissection of Wnt-induced FZD5 degradation showed ZNRF3/RNF43 selectively target FZD5/8 (not other FZDs), with RSPO1 specifically stabilizing these receptors and DVL being dispensable for ligand-induced turnover, clarifying the feedback architecture of FZD5 surface regulation.","evidence":"Endocytosis/degradation assays, co-IP of FZD5–RNF43 enhanced by Wnt, RSPO1 stabilization, DVL triple-knockout cells","pmids":["41070826"],"confidence":"High","gaps":["Ubiquitination sites on FZD5 targeted by ZNRF3/RNF43 not mapped","Structural basis for FZD5/8 selectivity over other FZDs unknown"]},{"year":null,"claim":"Key unresolved questions include the structural basis for FZD5 ligand selectivity among Wnt proteins, whether Gαq coupling and β-catenin signaling are activated simultaneously or in a context-dependent manner at endogenous expression levels, and the full spectrum of human disease caused by FZD5 mutations.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of full-length FZD5 in complex with Wnt and co-receptor","Gαq versus β-catenin pathway selection logic not defined","Comprehensive human genetic studies beyond coloboma lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,1,2,8]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[8,11,16]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,8,20,21]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[3,21]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,5,8,11,16,17]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,4,20]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[7,12,13]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[3,21]}],"complexes":["FZD5-LRP6 Wnt receptor complex","FZD5-LRP5 Wnt receptor complex"],"partners":["LRP6","LRP5","RNF43","ZNRF3","CVAK104","DVL","IGF2BP1","GNA11"],"other_free_text":[]},"mechanistic_narrative":"FZD5 is a seven-transmembrane Wnt receptor of the class Frizzled family that transduces both canonical WNT/β-catenin and non-canonical Ca²⁺/PKC signals to regulate vascular development, stem cell self-renewal, placental morphogenesis, and neural patterning. FZD5 binds WNT ligands (WNT5A, WNT7A, WNT7B, WNT2, WNT10b) through its extracellular cysteine-rich domain and partners with LRP5/LRP6 co-receptors to stabilize β-catenin and activate TCF/LEF transcription, while also coupling to Gαq to mobilize intracellular Ca²⁺ and activate PKC and CaMKII [PMID:12857724, PMID:30514810, PMID:25861751]. Surface availability of FZD5 is tightly controlled: Wnt-stimulated ZNRF3/RNF43-dependent ubiquitination drives its endocytosis and lysosomal degradation—a process antagonized by RSPO1—while CVAK104 independently mediates clathrin-dependent FZD5 internalization, and DNMT3A-mediated promoter methylation and the HIDEN lncRNA/IMP1 complex regulate its transcription and mRNA stability, respectively [PMID:41070826, PMID:19643732, PMID:38707304, PMID:37095549]. Heterozygous loss-of-function mutations in FZD5 cause coloboma and microphthalmia through dominant-negative interference with WNT signaling during optic fissure closure, and FZD5 is specifically essential for Wnt-dependent proliferation of RNF43-mutant pancreatic and colorectal cancers [PMID:26908622, PMID:27869803]."},"prefetch_data":{"uniprot":{"accession":"Q13467","full_name":"Frizzled-5","aliases":["FzE5"],"length_aa":585,"mass_kda":64.5,"function":"Receptor for Wnt proteins (PubMed:10097073, PubMed:20530549, PubMed:26908622, PubMed:9054360). Functions in the canonical Wnt/beta-catenin signaling pathway. In vitro activates WNT2, WNT10B, WNT5A, but not WNT2B or WNT4 signaling (By similarity). In neurons, activation by WNT7A promotes formation of synapses (PubMed:20530549). May be involved in transduction and intercellular transmission of polarity information during tissue morphogenesis and/or in differentiated tissues (Probable). Plays a role in yolk sac angiogenesis and in placental vascularization (By similarity). Plays a role in ocular development (PubMed:26908622)","subcellular_location":"Cell membrane; Golgi apparatus membrane; Synapse; Perikaryon; Cell projection, dendrite; Cell projection, axon","url":"https://www.uniprot.org/uniprotkb/Q13467/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FZD5","classification":"Not Classified","n_dependent_lines":20,"n_total_lines":1208,"dependency_fraction":0.016556291390728478},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FZD5","total_profiled":1310},"omim":[{"mim_id":"620731","title":"MICROPHTHALMIA/COLOBOMA 11; MCOPCB11","url":"https://www.omim.org/entry/620731"},{"mim_id":"610839","title":"OSTEOARTHRITIS SUSCEPTIBILITY 4; OS4","url":"https://www.omim.org/entry/610839"},{"mim_id":"606845","title":"GOLGI-ASSOCIATED PDZ AND COILED-COIL DOMAINS-CONTAINING PROTEIN; GOPC","url":"https://www.omim.org/entry/606845"},{"mim_id":"606146","title":"FRIZZLED CLASS RECEPTOR 8; FZD8","url":"https://www.omim.org/entry/606146"},{"mim_id":"601723","title":"FRIZZLED CLASS RECEPTOR 5; FZD5","url":"https://www.omim.org/entry/601723"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"intestine","ntpm":17.5},{"tissue":"liver","ntpm":21.2}],"url":"https://www.proteinatlas.org/search/FZD5"},"hgnc":{"alias_symbol":["HFZ5","DKFZP434E2135"],"prev_symbol":["C2orf31"]},"alphafold":{"accession":"Q13467","domains":[{"cath_id":"1.10.2000.10","chopping":"35-136","consensus_level":"high","plddt":92.4725,"start":35,"end":136},{"cath_id":"1.20.1070.10","chopping":"230-434_443-532","consensus_level":"high","plddt":91.3779,"start":230,"end":532}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13467","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q13467-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q13467-F1-predicted_aligned_error_v6.png","plddt_mean":81.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FZD5","jax_strain_url":"https://www.jax.org/strain/search?query=FZD5"},"sequence":{"accession":"Q13467","fasta_url":"https://rest.uniprot.org/uniprotkb/Q13467.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q13467/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13467"}},"corpus_meta":[{"pmid":"11092808","id":"PMC_11092808","title":"Mouse Wnt receptor gene Fzd5 is essential for yolk sac and placental angiogenesis.","date":"2001","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/11092808","citation_count":270,"is_preprint":false},{"pmid":"27869803","id":"PMC_27869803","title":"Genome-wide CRISPR screens reveal a Wnt-FZD5 signaling circuit as a druggable vulnerability of RNF43-mutant pancreatic tumors.","date":"2016","source":"Nature medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27869803","citation_count":230,"is_preprint":false},{"pmid":"29458020","id":"PMC_29458020","title":"CircRNA circ_0067934 promotes tumor growth and metastasis in hepatocellular carcinoma through regulation of miR-1324/FZD5/Wnt/β-catenin axis.","date":"2018","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/29458020","citation_count":169,"is_preprint":false},{"pmid":"12857724","id":"PMC_12857724","title":"Functional characterization of WNT7A signaling in PC12 cells: interaction with A FZD5 x LRP6 receptor complex and modulation by Dickkopf proteins.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12857724","citation_count":120,"is_preprint":false},{"pmid":"23610556","id":"PMC_23610556","title":"A positive feedback loop involving Gcm1 and Fzd5 directs chorionic branching morphogenesis in the placenta.","date":"2013","source":"PLoS biology","url":"https://pubmed.ncbi.nlm.nih.gov/23610556","citation_count":83,"is_preprint":false},{"pmid":"33230473","id":"PMC_33230473","title":"YTHDF1 Facilitates the Progression of Hepatocellular Carcinoma by Promoting FZD5 mRNA Translation in an m6A-Dependent Manner.","date":"2020","source":"Molecular therapy. 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and placental angiogenesis, with markedly reduced endothelial cell proliferation (BrdU labeling); Fzd5 specifically synergized with Wnt2, Wnt5a, and Wnt10b in ectopic axis induction assays in Xenopus embryos, establishing Fzd5 as a Wnt receptor required for vascular development.\",\n      \"method\": \"Homologous recombination knockout mice, BrdU proliferation assay, Xenopus axis induction assay\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — genetic knockout with defined cellular phenotype, replicated across multiple assays\",\n      \"pmids\": [\"11092808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"WNT7A signals through a FZD5·LRP6 receptor complex in PC12 cells to increase β-catenin stability and activate TCF-based transcription; this activity is antagonized by Dickkopf-1 and Dickkopf-3.\",\n      \"method\": \"TCF-luciferase reporter assay, β-catenin stability assay, functional epistasis with Dickkopf proteins in PC12 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays in cell lines establishing receptor complex composition and pathway position\",\n      \"pmids\": [\"12857724\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Purified Wnt7a binds to the extracellular cysteine-rich domain (CRD) of Fzd5 with nanomolar affinity, as shown by ELISA-based protein-protein binding assay; a split-eGFP complementation assay confirmed Wnt7a–Fzd5 interaction and subsequent canonical pathway activation in cells.\",\n      \"method\": \"ELISA-based binding assay, split-eGFP complementation assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — direct binding assay with purified proteins, single study\",\n      \"pmids\": [\"18230341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CVAK104 is a novel binding partner of both Dishevelled (Dvl) and FZD5 (but not FZD1 or FZD4); CVAK104 selectively induces clathrin-mediated internalization of FZD5 and its subsequent lysosomal degradation, thereby suppressing Wnt/β-catenin signaling; knockdown of CVAK104 increases FZD5 protein levels and activates Wnt signaling.\",\n      \"method\": \"Co-immunoprecipitation, dominant-negative Rab5, siRNA knockdown, lysosome inhibitor assay, β-catenin reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP, genetic perturbations, multiple orthogonal assays in one study\",\n      \"pmids\": [\"19643732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"A positive feedback loop between Gcm1 and Fzd5 is essential for chorionic branching morphogenesis: Gcm1 upregulates Fzd5 at branching initiation sites, and elevated Fzd5 via nuclear β-catenin signaling maintains Gcm1 expression; Fzd5-mediated signaling also induces disassembly of cell junctions (downregulation of ZO-1, claudin 4, claudin 7) and upregulates Vegf in trophoblast cells.\",\n      \"method\": \"Global and trophoblast-specific Fzd5/Gcm1 knockout mice, trophoblast stem cell lines, tetraploid aggregation assay\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic models (global + conditional KO), epistasis, specific cellular phenotypes\",\n      \"pmids\": [\"23610556\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Monocyte-secreted Wnt5a activates FZD5 in microvascular endothelial cells (mECs) through non-canonical signaling: FZD5 activation triggers intracellular Ca2+ release, NFκB transcriptional activity, and tissue factor (TF) gene expression, leading to angiogenesis via autocrine TF regulation.\",\n      \"method\": \"In vitro co-culture paracrine assay, intracellular Ca2+ measurement, NFκB reporter, TF expression, in vivo microvessel formation\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — defined signaling cascade, multiple assays, single lab\",\n      \"pmids\": [\"25240054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A heterozygous frameshift mutation in FZD5 (p.Ala219Glufs*49) produces a truncated protein that retains the WNT-ligand-binding CRD but lacks the transmembrane domain; the truncated protein is secreted from cells and acts as a dominant-negative receptor, antagonizing both canonical and non-canonical WNT signaling and causing coloboma and microphthalmia in zebrafish.\",\n      \"method\": \"Cell secretion assay, WNT signaling reporter assays, zebrafish injection, mouse retinal epithelium analysis\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — molecular characterization of mutant protein, multiple model organisms, loss-of-function phenotype\",\n      \"pmids\": [\"26908622\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Genome-wide CRISPR-Cas9 screens in RNF43-mutant pancreatic ductal adenocarcinoma (PDAC) cells identify a specific requirement for FZD5 (not other Frizzled receptors) for Wnt-dependent proliferation; anti-FZD5 antibodies inhibit RNF43-mutant PDAC and colorectal cancer organoid growth in vitro and in vivo, confirming FZD5 receptor-level specificity.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 dropout screen, recombinant antibodies, xenograft, patient-derived organoids\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — CRISPR screen validated by orthogonal antibody inhibition in multiple cancer models\",\n      \"pmids\": [\"27869803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"FZD5 functions as a prototypical GPCR: WNT-5A stimulation induces a conformational change in FZD5 reminiscent of class A/B GPCR activation, and FZD5 activates Gαq and its downstream effectors, as measured by live-cell dcFRAP and resonance energy transfer (RET)-based assays.\",\n      \"method\": \"Dual-color FRAP (dcFRAP), BRET/FRET resonance energy transfer assays, Gαq activation assays\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple spectrometric and live-cell imaging methods demonstrating G-protein coupling, single rigorous study\",\n      \"pmids\": [\"30514810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Surface plasmon resonance analysis demonstrates that WNT5A binds FZD5 with ~30% stronger response than to RYK; FZD5 knockdown completely abrogates the anti-proliferative effect of WNT5A in PC3 prostate cancer cells, whereas RYK knockdown preferentially mediates the pro-apoptotic effect.\",\n      \"method\": \"Surface plasmon resonance, siRNA knockdown, proliferation and apoptosis assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct binding measurement and receptor-specific knockdown, single lab\",\n      \"pmids\": [\"29930766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Loss of Fzd5 in endothelial cells causes G0/G1 cell cycle arrest and reduced migration; Fzd5 knockdown enhances PKC signaling and PKC/Ets1-mediated transcription of Angpt2 and Flt1, independently of canonical Wnt, NFAT, and JNK pathways.\",\n      \"method\": \"siRNA knockdown, 3D collagen co-culture, cell cycle analysis, PKC inhibition, Ets1 transcription factor assay\",\n      \"journal\": \"Angiogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — defined pathway (PKC/Ets1) with pharmacological and genetic dissection, single lab\",\n      \"pmids\": [\"29845518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"WNT5A activates FZD5 to stimulate FZD5/PKC signaling, which is responsible for P-glycoprotein upregulation and multidrug resistance in renal cell carcinoma; FZD5 silencing reverses Wnt-5a-induced phosphorylation of PKCα/βII and CaMKII.\",\n      \"method\": \"siRNA knockdown, miR-124 mimic, luciferase 3'UTR assay, western blot for p-PKCα/βII and p-CaMKII\",\n      \"journal\": \"Tumour biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — defined signaling cascade with siRNA and pharmacological tools, single lab\",\n      \"pmids\": [\"25861751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"YTHDF1 promotes FZD5 mRNA translation in an m6A-dependent manner, activating the WNT/β-catenin pathway in hepatocellular carcinoma; multi-omics (ribosome profiling + m6A-seq) revealed YTHDF1 accelerates translational output specifically from FZD5 mRNA.\",\n      \"method\": \"m6A-seq, ribosome profiling, YTHDF1 knockdown/overexpression, WNT/β-catenin pathway reporters\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multi-omics orthogonal approaches establishing m6A-dependent translational regulation, single lab\",\n      \"pmids\": [\"33230473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FZD5 promotes TNBC cell G1/S transition, DNA damage repair, and stemness through a signaling axis that activates transcription factor FOXM1, which in turn transcribes BRCA1 and BIRC5; WNT7B was identified as a specific ligand mediating these FZD5-dependent effects.\",\n      \"method\": \"Loss/gain-of-function studies, FOXM1 overexpression rescue, ChIP for FOXM1 on BRCA1/BIRC5 promoters\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — epistasis rescue experiment and ChIP, single lab\",\n      \"pmids\": [\"33311446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FZD5 knockdown in hMSCs promotes cellular senescence via the noncanonical Wnt pathway, as shown by increased senescence markers; FZD5 overexpression delays cell cycle arrest during prolonged culture; WNT5A treatment of FZD5-expressing cells promotes proliferation.\",\n      \"method\": \"siRNA knockdown, FZD5 overexpression, senescence marker assays, proliferation assays\",\n      \"journal\": \"Stem cells (Dayton, Ohio)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss and gain of function with defined phenotype in primary human cells, single lab\",\n      \"pmids\": [\"33338299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In cardiac fibroblasts, Wnt5a or Wnt11 increases FZD5 expression and activates EGFR phosphorylation; si-FZD5 suppresses increased p-EGFR and fibrotic signaling (p-p38, p-ERK), establishing a crosstalk loop between FZD5 and EGFR in cardiac fibrosis under pressure overload.\",\n      \"method\": \"siRNA knockdown, western blot, TAC mouse model, conditional medium experiments\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — in vitro and in vivo genetic perturbations showing FZD5-EGFR crosstalk, single lab\",\n      \"pmids\": [\"34564708\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"FZD5 prevents epithelial-mesenchymal transition (EMT) in gastric cancer through a PKC–ELF3–ZEB1 axis: FZD5 activates PKC, which induces ELF3 expression; ELF3 represses ZEB1 to block EMT; FZD5 requires co-receptor LRP5, and WNT7B is a putative FZD5 ligand in this context; FZD5 is negatively regulated by transcription factors SNAI2 and TEAD1 (ChIP).\",\n      \"method\": \"Loss/gain-of-function, ChIP-PCR, PKC inhibitor, migration assay, E-cadherin/Vimentin/ZEB1 western blot\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP and epistasis with multiple pathway components, single lab\",\n      \"pmids\": [\"33618713\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"WNT5A signals through FZD5 and co-receptor LRP5 to regulate proliferation and self-renewal of endometrial mesenchymal stem-like cells (eMSC) via WNT/β-catenin; anti-FZD5 antibody and FZD5 gene silencing reduce WNT5A binding to eMSC, TCF/LEF transcriptional activity, and active β-catenin levels.\",\n      \"method\": \"Anti-FZD5 neutralizing antibody, FZD5 siRNA, TCF/LEF reporter, co-culture, Dickkopf-1 LRP inhibition\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — receptor knockdown and antibody blockade with functional and molecular readouts, single lab\",\n      \"pmids\": [\"35295855\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Desert lncRNA HIDEN interacts with RNA-binding protein IMP1 (IGF2BP1); HIDEN depletion reduces the IMP1–FZD5 mRNA interaction and destabilizes FZD5 mRNA, reducing WNT activity and impairing human definitive endoderm differentiation; WNT agonist rescues differentiation deficiency caused by HIDEN or IMP1 loss.\",\n      \"method\": \"shRNA/promoter deletion of HIDEN, RNA immunoprecipitation (RIP), mRNA stability assay, WNT reporter, endoderm differentiation assay\",\n      \"journal\": \"Genome biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — RIP and mRNA stability assay establish HIDEN/IMP1-mediated FZD5 mRNA stabilization, single lab\",\n      \"pmids\": [\"37095549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Single-cell transcriptomics and functional approaches identify an endogenous WNT7A-FZD5 signaling axis as critical for fallopian tube stem cell renewal, with WNT/β-catenin pathway-activated cells forming a distinct transcriptomic cluster enriched in ECM remodeling and integrin signaling.\",\n      \"method\": \"Single-cell RNA-seq, WNT/β-catenin reporter organoids, functional knockdown/antibody blocking, bulk transcriptomics\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional organoid assays combined with single-cell transcriptomics, single lab\",\n      \"pmids\": [\"37917586\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FZD5 is specifically upregulated in anterior neural progenitor cells; its expression is downregulated as cells adopt posterior fate; stimulation of a tetravalent antibody that selectively clusters FZD5 and LRP6 activates WNT/β-catenin signaling and drives midbrain progenitor differentiation into functional dopaminergic neurons in vitro and in vivo.\",\n      \"method\": \"Cell surface FZD receptor profiling, agonist antibody (FZD5/LRP6 clustering), hPSC differentiation, dopaminergic neuron functional assays, in vivo transplantation\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — receptor-specific agonist antibody with functional readout in multiple systems, single rigorous study\",\n      \"pmids\": [\"38358799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Wnt ligands specifically induce FZD5 (and FZD8) endocytosis and lysosomal degradation in a ZNRF3/RNF43-dependent manner; ZNRF3/RNF43 selectively target FZD5/8 but not other FZDs for degradation upon Wnt stimulation; Wnt promotes the physical interaction between FZD5 and RNF43; RSPO1 enhances Wnt signaling by specifically stabilizing FZD5/8; DVL promotes ligand-independent FZD endocytosis but is dispensable for Wnt-induced FZD5/8 degradation.\",\n      \"method\": \"Endocytosis and degradation assays, co-immunoprecipitation (FZD5–RNF43 interaction), RSPO1 stabilization assay, DVL loss-of-function, receptor-selective degradation profiling\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, direct interaction between FZD5 and RNF43 shown, mechanistic pathway dissection\",\n      \"pmids\": [\"41070826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DNMT3A binds the FZD5 promoter to suppress its transcription via DNA methylation; reduced DNMT3A expression in NSCLC leads to FZD5 promoter hypomethylation and aberrant FZD5 upregulation; DNMT3A overexpression suppresses urethane-induced lung carcinogenesis and malignant cell behavior.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP) for DNMT3A at FZD5 promoter, quantitative methylation-specific PCR, lentiviral FZD5 silencing, mouse lung carcinogenesis model\",\n      \"journal\": \"Heliyon\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP confirms DNMT3A binding to FZD5 promoter with functional in vivo validation, single lab\",\n      \"pmids\": [\"38707304\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FZD5 is a seven-transmembrane class F GPCR that functions as a Wnt receptor (primary ligands include WNT5A, WNT7A, WNT7B, WNT2, and WNT10b), forming complexes with co-receptors LRP5/LRP6 to activate canonical WNT/β-catenin signaling; it also couples to Gαq to trigger non-canonical Ca2+/CaMKII and PKC pathways; its surface levels are regulated by CVAK104-mediated clathrin/lysosomal degradation and by Wnt-induced, ZNRF3/RNF43-dependent endocytosis that is antagonized by RSPO1; its transcription is suppressed by DNMT3A-mediated promoter methylation and its mRNA is stabilized by the HIDEN lncRNA/IMP1 complex; FZD5 is required for yolk sac and placental angiogenesis, neural anterior-posterior patterning (dopaminergic neuron specification), optic fissure closure, chorionic branching morphogenesis, and stem cell maintenance, and is specifically essential for Wnt-dependent proliferation of RNF43-mutant cancers.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"FZD5 is a seven-transmembrane Wnt receptor of the class Frizzled family that transduces both canonical WNT/β-catenin and non-canonical Ca²⁺/PKC signals to regulate vascular development, stem cell self-renewal, placental morphogenesis, and neural patterning. FZD5 binds WNT ligands (WNT5A, WNT7A, WNT7B, WNT2, WNT10b) through its extracellular cysteine-rich domain and partners with LRP5/LRP6 co-receptors to stabilize β-catenin and activate TCF/LEF transcription, while also coupling to Gαq to mobilize intracellular Ca²⁺ and activate PKC and CaMKII [PMID:12857724, PMID:30514810, PMID:25861751]. Surface availability of FZD5 is tightly controlled: Wnt-stimulated ZNRF3/RNF43-dependent ubiquitination drives its endocytosis and lysosomal degradation—a process antagonized by RSPO1—while CVAK104 independently mediates clathrin-dependent FZD5 internalization, and DNMT3A-mediated promoter methylation and the HIDEN lncRNA/IMP1 complex regulate its transcription and mRNA stability, respectively [PMID:41070826, PMID:19643732, PMID:38707304, PMID:37095549]. Heterozygous loss-of-function mutations in FZD5 cause coloboma and microphthalmia through dominant-negative interference with WNT signaling during optic fissure closure, and FZD5 is specifically essential for Wnt-dependent proliferation of RNF43-mutant pancreatic and colorectal cancers [PMID:26908622, PMID:27869803].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing that FZD5 is a Wnt receptor essential for embryonic vascular development resolved the question of whether Frizzled-5 has a non-redundant developmental role.\",\n      \"evidence\": \"Fzd5 knockout mice showed embryonic lethality at E10.75 from yolk sac/placental angiogenesis failure; Xenopus axis induction confirmed ligand selectivity (Wnt2, Wnt5a, Wnt10b)\",\n      \"pmids\": [\"11092808\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream intracellular signaling pathway not resolved\", \"Co-receptor requirements not determined\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstration that FZD5 forms a complex with LRP6 to activate β-catenin/TCF signaling positioned FZD5 within the canonical Wnt pathway and identified its co-receptor.\",\n      \"evidence\": \"TCF-luciferase and β-catenin stability assays in PC12 cells with WNT7A, antagonized by Dkk1/Dkk3\",\n      \"pmids\": [\"12857724\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct physical binding affinity between WNT7A and FZD5 not measured\", \"Non-canonical signaling not addressed\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Quantifying nanomolar-affinity binding of WNT7A to the FZD5 CRD established the biophysical basis for ligand-receptor selectivity.\",\n      \"evidence\": \"ELISA-based binding with purified proteins and split-eGFP complementation\",\n      \"pmids\": [\"18230341\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding affinities for other WNT ligands not compared side-by-side\", \"Structural basis for selectivity unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identification of CVAK104 as a selective internalization partner for FZD5 revealed that receptor surface levels are actively regulated by clathrin-mediated endocytosis and lysosomal degradation, tuning Wnt signal strength.\",\n      \"evidence\": \"Co-IP of CVAK104 with FZD5 (not FZD1/FZD4), dominant-negative Rab5, lysosome inhibitors, siRNA\",\n      \"pmids\": [\"19643732\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological contexts where CVAK104-mediated FZD5 turnover is rate-limiting not established\", \"Whether post-translational modifications gate CVAK104 binding unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Discovery of a Gcm1–FZD5 positive feedback loop in trophoblast cells explained how FZD5 drives chorionic branching morphogenesis through β-catenin-mediated junction remodeling and VEGF induction.\",\n      \"evidence\": \"Global and trophoblast-specific Fzd5/Gcm1 knockout mice, trophoblast stem cell lines, tetraploid aggregation\",\n      \"pmids\": [\"23610556\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FZD5 signals through canonical or non-canonical Wnt in trophoblasts not fully dissected\", \"Ligand identity in placenta not definitively assigned\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showing that WNT5A–FZD5 triggers intracellular Ca²⁺ release, NFκB activation, and tissue factor expression in endothelial cells established a non-canonical signaling branch distinct from β-catenin.\",\n      \"evidence\": \"Paracrine co-culture, Ca²⁺ imaging, NFκB reporter, TF expression, microvessel assay\",\n      \"pmids\": [\"25061751\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"G-protein coupling not directly measured in this system\", \"Contribution relative to canonical pathway not quantified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Two advances defined FZD5 disease relevance: a dominant-negative FZD5 truncation was shown to cause coloboma/microphthalmia, and CRISPR screening identified FZD5 as specifically essential in RNF43-mutant cancers, establishing therapeutic targeting rationale.\",\n      \"evidence\": \"Secreted truncated FZD5 (p.Ala219Glufs*49) antagonized WNT in zebrafish; genome-wide CRISPR dropout screen in PDAC plus anti-FZD5 antibody validation in organoids/xenografts\",\n      \"pmids\": [\"26908622\", \"27869803\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genotype–phenotype spectrum of FZD5 mutations in humans not fully mapped\", \"Mechanism of FZD5 selectivity in RNF43-mutant cancers versus other FZDs not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Biophysical demonstration that WNT5A induces a GPCR-like conformational change in FZD5 and activates Gαq established Frizzled receptors as bona fide GPCRs, not just scaffold receptors.\",\n      \"evidence\": \"dcFRAP and BRET/FRET assays for Gαq coupling in live cells\",\n      \"pmids\": [\"30514810\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Gαq coupling occurs at endogenous FZD5 expression levels not shown\", \"Structural basis for Gαq selectivity over other Gα subunits unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Dissection of FZD5 downstream signaling in endothelial cells and renal carcinoma showed that FZD5 restrains PKC/Ets1-driven Angpt2/Flt1 transcription and mediates WNT5A-induced PKCα/βII and CaMKII phosphorylation, expanding the non-canonical effector repertoire.\",\n      \"evidence\": \"siRNA, PKC inhibitors, Ets1 assays in endothelial cells; siRNA and phospho-western blots in renal carcinoma\",\n      \"pmids\": [\"29845518\", \"25861751\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PKC and CaMKII are activated in parallel or sequentially downstream of FZD5 not determined\", \"Direct versus indirect PKC activation not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of YTHDF1-mediated m6A-dependent translational enhancement of FZD5 mRNA and the WNT7B–FZD5–FOXM1 axis in cancer expanded understanding of FZD5 post-transcriptional regulation and downstream transcriptional targets.\",\n      \"evidence\": \"m6A-seq, ribosome profiling, YTHDF1 perturbation in HCC; ChIP for FOXM1 on BRCA1/BIRC5 promoters in TNBC\",\n      \"pmids\": [\"33230473\", \"33311446\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether m6A regulation of FZD5 mRNA operates in non-cancer contexts unknown\", \"Direct interaction between YTHDF1 and FZD5 mRNA not shown by CLIP\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Discovery that the lncRNA HIDEN scaffolds IMP1 onto FZD5 mRNA to stabilize it revealed a non-coding RNA layer of FZD5 regulation critical for endoderm differentiation, while single-cell data identified WNT7A–FZD5 as the key stem cell renewal axis in fallopian tube organoids.\",\n      \"evidence\": \"RIP, mRNA stability assay, WNT reporter rescue in hESC endoderm differentiation; scRNA-seq and functional organoid assays in fallopian tube\",\n      \"pmids\": [\"37095549\", \"37917586\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of HIDEN–IMP1–FZD5 mRNA complex not defined\", \"Whether FZD5 is the sole Frizzled mediating fallopian tube stemness not excluded\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Selective upregulation of FZD5 in anterior neural progenitors and its functional sufficiency to drive dopaminergic neuron specification via a tetravalent agonist antibody clustering FZD5/LRP6 established FZD5 as a regional Wnt signal interpreter during neural patterning.\",\n      \"evidence\": \"Cell-surface FZD profiling, agonist antibody, hPSC-derived midbrain progenitor differentiation, in vivo transplantation\",\n      \"pmids\": [\"38358799\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous ligand driving FZD5 in midbrain specification in vivo not definitively identified\", \"Whether FZD5 agonist antibody activates non-canonical pathways not assessed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mechanistic dissection of Wnt-induced FZD5 degradation showed ZNRF3/RNF43 selectively target FZD5/8 (not other FZDs), with RSPO1 specifically stabilizing these receptors and DVL being dispensable for ligand-induced turnover, clarifying the feedback architecture of FZD5 surface regulation.\",\n      \"evidence\": \"Endocytosis/degradation assays, co-IP of FZD5–RNF43 enhanced by Wnt, RSPO1 stabilization, DVL triple-knockout cells\",\n      \"pmids\": [\"41070826\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitination sites on FZD5 targeted by ZNRF3/RNF43 not mapped\", \"Structural basis for FZD5/8 selectivity over other FZDs unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis for FZD5 ligand selectivity among Wnt proteins, whether Gαq coupling and β-catenin signaling are activated simultaneously or in a context-dependent manner at endogenous expression levels, and the full spectrum of human disease caused by FZD5 mutations.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of full-length FZD5 in complex with Wnt and co-receptor\", \"Gαq versus β-catenin pathway selection logic not defined\", \"Comprehensive human genetic studies beyond coloboma lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1, 2, 8]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [8, 11, 16]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 8, 20, 21]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [3, 21]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 5, 8, 11, 16, 17]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 4, 20]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [7, 12, 13]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [3, 21]}\n    ],\n    \"complexes\": [\n      \"FZD5-LRP6 Wnt receptor complex\",\n      \"FZD5-LRP5 Wnt receptor complex\"\n    ],\n    \"partners\": [\n      \"LRP6\",\n      \"LRP5\",\n      \"RNF43\",\n      \"ZNRF3\",\n      \"CVAK104\",\n      \"DVL\",\n      \"IGF2BP1\",\n      \"GNA11\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}