{"gene":"NKD1","run_date":"2026-04-29T11:37:56","timeline":{"discoveries":[{"year":2001,"finding":"Human NKD1 was cloned and characterized as a Dishevelled-binding protein with an EF-hand motif in the NH2 domain, functioning as a negative regulator of the WNT–β-catenin–TCF signaling pathway, orthologous to mouse Nkd.","method":"Molecular cloning, sequence analysis, domain characterization","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 3 — cloning and domain characterization; foundational paper replicated by subsequent functional studies","pmids":["11604995"],"is_preprint":false},{"year":2004,"finding":"The EF-hand motif of Nkd1 is required for its inhibitory function on Wnt/β-catenin signaling; mice expressing EF-hand-deleted Nkd1 show increased nuclear β-catenin in elongating spermatids and reduced sperm count, but no intestinal polyposis effect in Apc-mutant background.","method":"Targeted mouse knockout (EF-hand deletion), nuclear β-catenin localization by immunostaining, sperm count and testis weight measurements, genetic epistasis with Apc mutant","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — in vivo loss-of-function with defined molecular phenotype and domain mutagenesis, replicated by subsequent structural/functional studies","pmids":["15546883"],"is_preprint":false},{"year":2007,"finding":"Mouse Nkd1 and Nkd2 proteins bind Dvl proteins and inhibit Wnt signaling; targeted replacement of nkd exons encoding Dvl-binding sequences with lacZ/neomycin cassettes generates viable double-knockout mice with subtle cranial bone morphology alterations reminiscent of axin2 mutation, demonstrating partial functional redundancy.","method":"Gene targeting (IRES-lacZ/neomycin knock-in), double-knockout mouse generation, skeletal analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal genetic loss-of-function with defined cellular/developmental phenotype; Dvl-binding domain ablation confirmed mechanistically","pmids":["17438140"],"is_preprint":false},{"year":2009,"finding":"NKD1 mutations found in colorectal tumors reduce its ability to bind and destabilize Dvl proteins, leading to β-catenin stabilization and increased cell proliferation, directly implicating NKD1 in Wnt-dependent tumorigenesis.","method":"Mutation identification in patient tumors, co-immunoprecipitation (NKD1–Dvl binding), β-catenin stabilization assay, cell proliferation assay, luciferase Wnt reporter assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (Co-IP, reporter, proliferation) with patient-derived mutations and functional rescue","pmids":["19956716"],"is_preprint":false},{"year":2010,"finding":"Zebrafish Nkd1 promotes Dvl degradation upon overexpression; knockdown of Nkd1 specifically in dorsal forerunner cells results in β-catenin nuclear localization, transcriptional activation, impaired DFC migration, defective KV formation and ciliogenesis, and disrupted left-right patterning.","method":"Zebrafish morpholino knockdown (DFC-specific), Nkd1 overexpression, β-catenin nuclear localization imaging, KV formation and ciliogenesis analysis, asymmetric charon expression assay","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific knockdown with multiple orthogonal readouts including molecular (β-catenin localization, Dvl degradation) and developmental phenotypes","pmids":["20858476"],"is_preprint":false},{"year":2013,"finding":"Nkd1 functions as a passive antagonist of Wnt/β-catenin signaling, with its antagonistic activity enhanced in Wnt/Planar Cell Polarity pathway mutants (slb/wnt11 and tri/vangl2), suggesting Nkd1 acts to buffer destabilized or breached Wnt signaling rather than constitutively suppressing it.","method":"Zebrafish genetic epistasis using Wnt/PCP mutant lines (silberblick, trilobite), Wnt8a overexpression dorsalization assay, Nkd1 rescue experiments","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in multiple mutant backgrounds with functional rescue, single lab","pmids":["24009776"],"is_preprint":false},{"year":2015,"finding":"Nkd1 activity is specifically dependent on Wnt ligand activation of the receptor; Nkd1 is recruited to the Wnt signalosome with Dvl2 upon ligand stimulation, then moves into the cytoplasm to interact with β-catenin and inhibit its nuclear accumulation.","method":"Zebrafish blastula Wnt-responsive cell assay, Wnt ligand stimulation, co-immunoprecipitation (Nkd1–Dvl2, Nkd1–β-catenin), subcellular fractionation/localization","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (Co-IP, fractionation, functional assay) establishing pathway position and molecular interactions","pmids":["25904337"],"is_preprint":false},{"year":2015,"finding":"NKD1 is an immediate early transcriptional target of FGF receptor signaling in endoderm; NKD1 loss suppresses hepatic progenitor cell formation from human iPSCs, and this phenotype is rescued by pharmacological antagonism of canonical WNT signaling, placing NKD1 downstream of FGFR and upstream of WNT inhibition in hepatic specification.","method":"Human iPSC differentiation, FGFR inhibition and stimulation, NKD1 knockdown, pharmacological WNT antagonist rescue, hepatic progenitor marker analysis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis (KD + pharmacological rescue) with functional developmental readout in human stem cell system","pmids":["26637527"],"is_preprint":false},{"year":2016,"finding":"NKD1 interacts with Rac1 in the cytoplasm and promotes its degradation via the ubiquitin-proteasome pathway; NKD1 overexpression attenuates HCC cell migration and invasion by downregulating Rac1 expression and activity, affecting the cytoskeleton and E-cadherin expression. Conversely, Rac1 negatively regulates EZH2, which enhances NKD1 transcription, forming a NKD1/Rac1 feedback loop.","method":"Co-immunoprecipitation (NKD1–Rac1), overexpression/knockdown in HCC cells, ubiquitin-proteasome pathway inhibitor assay, in vitro and in vivo migration/invasion assays, cytoskeleton imaging","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP, proteasome inhibitor confirmation, and functional in vitro/in vivo assays; single lab","pmids":["27231134"],"is_preprint":false},{"year":2016,"finding":"Rnf25/AO7 E3 ubiquitin ligase physically interacts with both Nkd1 and Axin in an E3-ligase-independent manner, disrupting the Nkd1–Axin inhibitory complex to positively regulate Wnt signaling; this distinguishes Nkd1 from Nkd2 (which is ubiquitinated by Rnf25).","method":"Co-immunoprecipitation (Rnf25–Nkd1, Rnf25–Axin), zebrafish rnf25 knockdown with Wnt target gene readout, E3-ligase dead mutant analysis","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP with mechanistic E3-ligase mutant controls and in vivo zebrafish validation; single lab","pmids":["27007149"],"is_preprint":false},{"year":2018,"finding":"The lncRNA H19 binds EZH2 in glioblastoma cells and recruits it to the NKD1 promoter, promoting H3K27 trimethylation and transcriptional repression of NKD1; H19 knockdown impairs EZH2 binding to the NKD1 promoter.","method":"RNA immunoprecipitation (H19–EZH2), chromatin immunoprecipitation (EZH2 at NKD1 promoter), H19 knockdown with NKD1 expression measurement, H3K27me3 analysis","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 — RIP and ChIP with functional gene expression readout; single lab, moderate evidence","pmids":["29643989"],"is_preprint":false},{"year":2017,"finding":"By interacting with EZH2, the lncRNA HNF1A-AS1 promotes repression of NKD1 expression in HCC cells to facilitate cell proliferation and S-phase progression.","method":"RNA immunoprecipitation (HNF1A-AS1–EZH2), chromatin immunoprecipitation (EZH2 at NKD1 promoter), HNF1A-AS1 knockdown/overexpression, cell proliferation and cell cycle analysis","journal":"Biomedicine & pharmacotherapy","confidence":"Medium","confidence_rationale":"Tier 2 — RIP and ChIP with functional readout; single lab","pmids":["28292020"],"is_preprint":false},{"year":2022,"finding":"NKD1 binds APC protein and promotes its ubiquitination-dependent degradation by suppressing the deubiquitinase USP15 and blocking the USP15–APC interaction, thereby paradoxically enhancing β-catenin nuclear accumulation and colon cancer cell proliferation in this context.","method":"Co-immunoprecipitation (NKD1–APC, USP15–APC), ubiquitination assay, β-catenin nuclear localization assay, NKD1 knockout cell line, cell proliferation/migration assays","journal":"Cancer science","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP, ubiquitination assay, and functional rescue; single lab","pmids":["36445120"],"is_preprint":false},{"year":2023,"finding":"NKD1 protein binds directly to the YWHAE gene promoter and activates YWHAE transcription, thereby promoting glucose uptake in colon cancer cells; NKD1 and YWHAE proteins also co-localize in colon cancer cells.","method":"Chromatin immunoprecipitation (NKD1 at YWHAE promoter), dual-luciferase reporter assay, NKD1 overexpression/knockout, immunofluorescence co-localization, glucose uptake assay","journal":"Journal of Southern Medical University","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP and luciferase reporter with functional glucose uptake readout; single lab","pmids":["37202194"],"is_preprint":false},{"year":2023,"finding":"NKD1 interacts with PCM1 and promotes PCM1 degradation through the ubiquitin-proteasome pathway; PCM1 overexpression reverses the cell-cycle inhibition caused by NKD1 depletion in colorectal cancer cells.","method":"Co-immunoprecipitation (NKD1–PCM1), quantitative proteomics, ubiquitin-proteasome pathway assay, siRNA knockdown, cell cycle analysis, rescue experiment with PCM1 overexpression","journal":"Molecular biology reports","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus proteomic discovery and functional rescue; single lab","pmids":["37338734"],"is_preprint":false},{"year":2024,"finding":"Nkd1 functions downstream of Axin2 in the Wnt negative feedback cascade; zebrafish axin2/nkd1 double mutants phenocopy nkd1 single mutants at the level of Wnt target gene expression and protein profiles, placing Nkd1 epistatically downstream of Axin2. Both regulators share defects in heart looping, neuromast migration, and behavior, but show no synergy in the double mutant.","method":"CRISPR/Cas9 axin2, nkd1 single and double mutant zebrafish, qRT-PCR, RNA-seq, mass spectrometry proteomics of Wnt target gene expression, phenotypic analysis","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with multiple orthogonal molecular readouts (qRT-PCR, RNA-seq, proteomics) in well-controlled CRISPR mutants","pmids":["38656801"],"is_preprint":false},{"year":2024,"finding":"YTHDF3 (m6A reader) suppresses NKD1 transcription and translation in an m6A-dependent manner, thereby activating WNT/β-catenin signaling and promoting HCC invasion and metastasis.","method":"RNA-seq, meRIP-seq, Lace-seq (m6A site identification), YTHDF3 knockdown/overexpression, Western blot and qPCR for NKD1 expression, in vitro and in vivo invasion/metastasis assays","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 — multi-omics identification of m6A modification site on NKD1 mRNA with functional validation; single lab","pmids":["39127439"],"is_preprint":false},{"year":2025,"finding":"NKD1 inhibits autophagic degradation of MYC protein by suppressing the interaction between LC3B and MYC; NKD1 binds MYC through its EF-hand domain, facilitates MYC nuclear entry, and thereby activates MYC target genes to promote colon cancer cell proliferation, migration, and angiogenesis. PPARδ was identified as a transcription factor driving NKD1 gene expression.","method":"NKD1 knockout cell line (SW620-nkd1-/-), differential proteomics, co-immunoprecipitation (NKD1–MYC, LC3B–MYC), EF-hand domain mutant analysis, autophagy assays, nuclear fractionation, ChIP (PPARδ at NKD1 promoter), functional cell assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP, domain mutagenesis, autophagy pathway analysis with functional readout; single lab, recent publication","pmids":["40675969"],"is_preprint":false},{"year":2026,"finding":"Wnt3a signaling upregulates NKD1 and MSX1 expression in dental pulp stem cells; NKD1 undergoes membrane detachment and directly interacts with MSX1 to promote its nuclear translocation, where MSX1 occupies promoters of odontogenic regulators to drive odontoblast differentiation and dentin formation.","method":"Single-cell transcriptomics, CUT&Tag (MSX1 ChIP-seq), co-immunoprecipitation/co-localization (NKD1–MSX1), NKD1 membrane detachment imaging, Wnt3a stimulation, murine pulp exposure model, SCENIC gene regulatory network analysis","journal":"International journal of oral science","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP, CUT&Tag, in vivo model with multiple orthogonal approaches; single lab, very recent publication","pmids":["41526338"],"is_preprint":false}],"current_model":"NKD1 is a negative feedback regulator of canonical Wnt/β-catenin signaling that, upon Wnt ligand stimulation, is recruited to the Wnt signalosome with Dvl, then binds and destabilizes Dvl proteins and interacts with β-catenin via its EF-hand domain to inhibit nuclear β-catenin accumulation; it functions epistatically downstream of Axin2, can be epigenetically silenced by lncRNA-EZH2 complexes or suppressed by m6A readers, and also has non-canonical roles including promoting Rac1 and PCM1 degradation via the ubiquitin-proteasome pathway, inhibiting MYC autophagic degradation through LC3B competition, and activating YWHAE transcription, collectively influencing cancer cell proliferation, migration, and developmental processes such as spermatogenesis, left-right patterning, hepatic specification, and odontoblast differentiation."},"narrative":{"teleology":[{"year":2001,"claim":"Identification of NKD1 as a Dvl-binding, EF-hand-containing antagonist of Wnt/β-catenin signaling established the gene's core molecular identity and pathway membership.","evidence":"Molecular cloning, domain analysis, and sequence comparison with Drosophila nkd in human cells","pmids":["11604995"],"confidence":"Medium","gaps":["No functional validation of Dvl-binding or EF-hand requirement in this study","Mechanism of Wnt inhibition not resolved"]},{"year":2004,"claim":"Demonstrating that the EF-hand motif is required for NKD1's inhibition of nuclear β-catenin accumulation in vivo established the first structure-function relationship and revealed a physiological role in spermatogenesis.","evidence":"EF-hand-deleted Nkd1 knock-in mice analyzed for nuclear β-catenin in spermatids and sperm count; epistasis with Apc mutation","pmids":["15546883"],"confidence":"High","gaps":["Why EF-hand-deleted mice lack intestinal phenotype in Apc-mutant background remains unexplained","Direct binding partner of the EF-hand domain was not identified at this stage"]},{"year":2007,"claim":"Generation of Nkd1/Nkd2 double-knockout mice revealed partial functional redundancy between the two paralogs and subtle cranial bone phenotypes resembling Axin2 loss, linking Nkd proteins to Wnt feedback in skeletal patterning.","evidence":"Dvl-binding-domain-targeted Nkd1/Nkd2 double-knockout mice with skeletal analysis","pmids":["17438140"],"confidence":"High","gaps":["Mild double-knockout phenotype suggests additional compensatory Wnt feedback mechanisms","No biochemical readout of Wnt pathway activation in these mutants"]},{"year":2009,"claim":"Discovery that colorectal tumor mutations in NKD1 reduce Dvl binding and destabilization, leading to β-catenin stabilization, provided direct evidence that NKD1 loss-of-function contributes to Wnt-driven tumorigenesis.","evidence":"Patient tumor mutation identification followed by Co-IP, Wnt reporter, and cell proliferation assays","pmids":["19956716"],"confidence":"High","gaps":["No in vivo tumor model with NKD1 mutation rescue","Whether these mutations are driver or passenger events in CRC was not formally established"]},{"year":2010,"claim":"Cell-type-specific Nkd1 knockdown in zebrafish DFC established that Nkd1 promotes Dvl degradation and restrains nuclear β-catenin to enable proper Kupffer's vesicle formation, ciliogenesis, and left-right axis patterning.","evidence":"DFC-targeted morpholino knockdown with β-catenin localization, KV/cilia analysis, and asymmetric gene expression readouts","pmids":["20858476"],"confidence":"High","gaps":["Mechanism of Dvl degradation (proteasomal vs lysosomal) not distinguished","Whether Nkd1 role in LR patterning is conserved in mammals not tested"]},{"year":2015,"claim":"Two studies established that NKD1 is specifically activated by Wnt ligand engagement—being recruited to the signalosome with Dvl2, then redistributing to the cytoplasm to bind β-catenin—and that FGF signaling induces NKD1 as an immediate-early gene required for hepatic specification from human iPSCs.","evidence":"Zebrafish Wnt-responsive cell assay with Co-IP and subcellular fractionation (Nkd1–Dvl2, Nkd1–β-catenin); human iPSC hepatic differentiation with NKD1 knockdown and WNT antagonist rescue","pmids":["25904337","26637527"],"confidence":"High","gaps":["How Nkd1 membrane detachment is triggered biochemically was not resolved","Whether FGF-induced NKD1 acts identically to Wnt-induced NKD1 in molecular mechanism"]},{"year":2016,"claim":"NKD1 was shown to interact with Rac1 and promote its proteasomal degradation, establishing a Wnt-independent function in cell migration control, while Rnf25 was found to disrupt the Nkd1–Axin complex in a ligase-independent manner to modulate Wnt signaling.","evidence":"Co-IP (NKD1–Rac1) with proteasome inhibitor treatment, migration/invasion assays in HCC cells; Co-IP (Rnf25–Nkd1/Axin) with E3-ligase-dead mutant in zebrafish","pmids":["27231134","27007149"],"confidence":"Medium","gaps":["Whether NKD1 itself serves as an E3 ligase adaptor for Rac1 ubiquitination is unknown","Rnf25–Nkd1 interaction not validated in mammalian cells","Single-lab findings for both"]},{"year":2017,"claim":"Multiple lncRNAs (HNF1A-AS1, H19) were found to recruit EZH2 to the NKD1 promoter for H3K27me3-mediated transcriptional silencing, establishing epigenetic repression as a major mechanism of NKD1 downregulation in cancer.","evidence":"RIP (lncRNA–EZH2) and ChIP (EZH2/H3K27me3 at NKD1 promoter) in HCC and glioblastoma cells with lncRNA knockdown","pmids":["28292020","29643989"],"confidence":"Medium","gaps":["Each lncRNA–EZH2–NKD1 axis demonstrated in a single lab/cancer type","No in vivo validation of epigenetic silencing effects on NKD1"]},{"year":2022,"claim":"A paradoxical pro-tumorigenic role was uncovered in which NKD1 binds APC and promotes its ubiquitination by suppressing USP15, thereby enhancing β-catenin nuclear accumulation in colon cancer—contrasting the canonical model of NKD1 as a Wnt antagonist.","evidence":"Co-IP (NKD1–APC, USP15–APC), ubiquitination assays, NKD1 knockout colon cancer cell lines","pmids":["36445120"],"confidence":"Medium","gaps":["Apparent contradiction with canonical Wnt-inhibitory function not reconciled","Single-lab finding; no independent replication","Cell-type or context specificity not defined"]},{"year":2023,"claim":"NKD1 was shown to directly bind the YWHAE promoter to activate its transcription and to interact with PCM1 to promote its proteasomal degradation, expanding NKD1's roles to transcriptional activation and centrosome-associated protein homeostasis in colon cancer.","evidence":"ChIP and luciferase reporter for NKD1 at YWHAE promoter; Co-IP (NKD1–PCM1) with quantitative proteomics and cell cycle rescue","pmids":["37202194","37338734"],"confidence":"Medium","gaps":["DNA-binding domain of NKD1 not identified; mechanism of transcriptional activation unclear","Each interaction reported by a single lab","PCM1 degradation pathway (direct adaptor vs indirect) not resolved"]},{"year":2024,"claim":"Genetic epistasis using CRISPR mutants demonstrated that Nkd1 functions downstream of Axin2 in the Wnt negative feedback hierarchy, while YTHDF3-mediated m6A modification was shown to suppress NKD1 mRNA to activate Wnt signaling in HCC.","evidence":"Zebrafish axin2/nkd1 single and double CRISPR mutants with RNA-seq and proteomics; meRIP-seq and YTHDF3 manipulation in HCC cells","pmids":["38656801","39127439"],"confidence":"High","gaps":["How Nkd1 is positioned downstream of Axin2 biochemically is not resolved","Whether YTHDF3 regulation of NKD1 is tissue-specific or generalizable is unknown"]},{"year":2025,"claim":"NKD1 was found to inhibit MYC autophagic degradation by competing with LC3B for MYC binding through its EF-hand domain, facilitating MYC nuclear entry and target gene activation, revealing a direct oncogenic mechanism in colon cancer.","evidence":"NKD1-knockout SW620 cells, Co-IP (NKD1–MYC, LC3B–MYC), EF-hand domain mutagenesis, autophagy assays, nuclear fractionation, ChIP of PPARδ at NKD1 promoter","pmids":["40675969"],"confidence":"Medium","gaps":["Single-lab finding; no independent replication","Whether MYC protection by NKD1 operates in non-cancer contexts unknown","Structural basis for LC3B–MYC competition not determined"]},{"year":2026,"claim":"NKD1 was shown to undergo Wnt3a-induced membrane detachment and interact with MSX1 to drive its nuclear translocation and occupancy of odontogenic gene promoters, linking NKD1 to odontoblast differentiation and dentin formation.","evidence":"Single-cell transcriptomics, CUT&Tag, Co-IP (NKD1–MSX1), membrane detachment imaging in dental pulp stem cells, murine pulp exposure model","pmids":["41526338"],"confidence":"Medium","gaps":["Single-lab finding in dental pulp stem cells","Membrane detachment mechanism not molecularly defined","Whether MSX1 interaction requires EF-hand or Dvl-binding domain unknown"]},{"year":null,"claim":"Key unresolved questions include: the structural basis for how NKD1's EF-hand domain engages β-catenin vs MYC vs MSX1; how NKD1 switches between Wnt-antagonistic and context-dependent pro-tumorigenic functions (e.g., APC degradation, MYC stabilization); and whether NKD1's roles in proteasomal degradation of Rac1 and PCM1 involve specific E3 ligase recruitment.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal or cryo-EM structure of NKD1 or its complexes","Context-dependent switch between tumor suppressor and oncogene not mechanistically resolved","E3 ligase adaptors for NKD1-mediated degradation targets not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,3,4,6,15]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[13]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[6,8]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[6,18]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,3,4,6,15]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4,7,18]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[8,14]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[3,12,17]}],"complexes":[],"partners":["DVL2","CTNNB1","RAC1","PCM1","MYC","APC","MSX1","RNF25"],"other_free_text":[]},"mechanistic_narrative":"NKD1 is a Wnt-inducible negative feedback regulator of canonical Wnt/β-catenin signaling that also exerts Wnt-independent functions in protein degradation, transcriptional activation, and autophagy modulation. Upon Wnt ligand stimulation, NKD1 is recruited to the Wnt signalosome with Dvl2, then moves into the cytoplasm where it binds and destabilizes Dvl proteins via its conserved Dvl-binding domain and interacts with β-catenin through its EF-hand motif to inhibit β-catenin nuclear accumulation; it functions epistatically downstream of Axin2 in this negative feedback cascade [PMID:25904337, PMID:38656801, PMID:15546883]. Beyond canonical Wnt antagonism, NKD1 promotes ubiquitin-proteasome-dependent degradation of Rac1 and PCM1, inhibits autophagic degradation of MYC by competing with LC3B binding, directly activates YWHAE transcription, and interacts with MSX1 to facilitate its nuclear translocation during odontoblast differentiation [PMID:27231134, PMID:37338734, PMID:40675969, PMID:37202194, PMID:41526338]. NKD1 expression is regulated by FGF signaling in hepatic specification, by EZH2-recruiting lncRNAs (H19, HNF1A-AS1) that impose H3K27me3-mediated silencing at its promoter, and by the m6A reader YTHDF3 that suppresses its mRNA post-transcriptionally [PMID:26637527, PMID:29643989, PMID:39127439]."},"prefetch_data":{"uniprot":{"accession":"Q969G9","full_name":"Protein naked cuticle homolog 1","aliases":[],"length_aa":470,"mass_kda":52.3,"function":"Cell autonomous antagonist of the canonical Wnt signaling pathway. May activate a second Wnt signaling pathway that controls planar cell polarity","subcellular_location":"Cell membrane; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q969G9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NKD1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NKD1","total_profiled":1310},"omim":[{"mim_id":"607852","title":"NKD INHIBITOR OF WNT SIGNALING PATHWAY 2; NKD2","url":"https://www.omim.org/entry/607852"},{"mim_id":"607851","title":"NKD INHIBITOR OF WNT SIGNALING PATHWAY 1; NKD1","url":"https://www.omim.org/entry/607851"},{"mim_id":"190198","title":"NOTCH RECEPTOR 1; NOTCH1","url":"https://www.omim.org/entry/190198"},{"mim_id":"164820","title":"WINGLESS-TYPE MMTV INTEGRATION SITE FAMILY, MEMBER 1; WNT1","url":"https://www.omim.org/entry/164820"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoli fibrillar center","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"blood vessel","ntpm":14.7}],"url":"https://www.proteinatlas.org/search/NKD1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q969G9","domains":[{"cath_id":"1.20.5","chopping":"137-169","consensus_level":"medium","plddt":83.963,"start":137,"end":169}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q969G9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q969G9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q969G9-F1-predicted_aligned_error_v6.png","plddt_mean":54.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NKD1","jax_strain_url":"https://www.jax.org/strain/search?query=NKD1"},"sequence":{"accession":"Q969G9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q969G9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q969G9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q969G9"}},"corpus_meta":[{"pmid":"11604995","id":"PMC_11604995","title":"Molecular cloning, gene structure, and expression analyses of NKD1 and NKD2.","date":"2001","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/11604995","citation_count":115,"is_preprint":false},{"pmid":"28356225","id":"PMC_28356225","title":"miR-532 promoted gastric cancer migration and invasion by targeting NKD1.","date":"2017","source":"Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/28356225","citation_count":54,"is_preprint":false},{"pmid":"31435644","id":"PMC_31435644","title":"Exosome-mediated transfer of miR-1290 promotes cell proliferation and invasion in gastric cancer via NKD1.","date":"2019","source":"Acta biochimica et biophysica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/31435644","citation_count":42,"is_preprint":false},{"pmid":"19956716","id":"PMC_19956716","title":"Mutations in the human naked cuticle homolog NKD1 found in colorectal cancer alter Wnt/Dvl/beta-catenin signaling.","date":"2009","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/19956716","citation_count":42,"is_preprint":false},{"pmid":"29643989","id":"PMC_29643989","title":"The lncRNA H19 positively affects the tumorigenic properties of glioblastoma cells and contributes to NKD1 repression through the recruitment of EZH2 on its promoter.","date":"2018","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/29643989","citation_count":41,"is_preprint":false},{"pmid":"15546883","id":"PMC_15546883","title":"A targeted mutation of Nkd1 impairs mouse spermatogenesis.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15546883","citation_count":38,"is_preprint":false},{"pmid":"20858476","id":"PMC_20858476","title":"Zebrafish Nkd1 promotes Dvl degradation and is required for left-right patterning.","date":"2010","source":"Developmental 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biology","url":"https://pubmed.ncbi.nlm.nih.gov/17438140","citation_count":31,"is_preprint":false},{"pmid":"25904337","id":"PMC_25904337","title":"Wnt ligand-dependent activation of the negative feedback regulator Nkd1.","date":"2015","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/25904337","citation_count":31,"is_preprint":false},{"pmid":"26637527","id":"PMC_26637527","title":"FGF2 mediates hepatic progenitor cell formation during human pluripotent stem cell differentiation by inducing the WNT antagonist NKD1.","date":"2015","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/26637527","citation_count":30,"is_preprint":false},{"pmid":"25446263","id":"PMC_25446263","title":"NKD1 marks intestinal and liver tumors linked to aberrant Wnt signaling.","date":"2014","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/25446263","citation_count":22,"is_preprint":false},{"pmid":"27231134","id":"PMC_27231134","title":"The NKD1/Rac1 feedback loop regulates the invasion and migration ability of hepatocarcinoma cells.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27231134","citation_count":20,"is_preprint":false},{"pmid":"36445120","id":"PMC_36445120","title":"Let-7b-5p inhibits colon cancer progression by prohibiting APC ubiquitination degradation and the Wnt pathway by targeting NKD1.","date":"2022","source":"Cancer science","url":"https://pubmed.ncbi.nlm.nih.gov/36445120","citation_count":16,"is_preprint":false},{"pmid":"25706354","id":"PMC_25706354","title":"Expression pattern and clinicopathologic significance of NKD1 in human primary hepatocellular carcinoma.","date":"2015","source":"APMIS : acta pathologica, microbiologica, et immunologica Scandinavica","url":"https://pubmed.ncbi.nlm.nih.gov/25706354","citation_count":12,"is_preprint":false},{"pmid":"16763811","id":"PMC_16763811","title":"Expression and regulation of Nkd-1, an intracellular component of Wnt signalling pathway in the chick embryo.","date":"2006","source":"Anatomy and embryology","url":"https://pubmed.ncbi.nlm.nih.gov/16763811","citation_count":9,"is_preprint":false},{"pmid":"27007149","id":"PMC_27007149","title":"Rnf25/AO7 positively regulates wnt signaling via disrupting Nkd1-Axin inhibitory complex independent of its ubiquitin ligase activity.","date":"2016","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/27007149","citation_count":8,"is_preprint":false},{"pmid":"29115501","id":"PMC_29115501","title":"Downregulation of NKD1 in human osteosarcoma and its clinical significance.","date":"2017","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/29115501","citation_count":7,"is_preprint":false},{"pmid":"39127439","id":"PMC_39127439","title":"YTHDF3-mediated m6A modification of NKD1 regulates hepatocellular carcinoma invasion and metastasis by activating the WNT/β-catenin signaling axis.","date":"2024","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/39127439","citation_count":7,"is_preprint":false},{"pmid":"38656801","id":"PMC_38656801","title":"Nkd1 functions downstream of Axin2 to attenuate Wnt signaling.","date":"2024","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/38656801","citation_count":6,"is_preprint":false},{"pmid":"36969985","id":"PMC_36969985","title":"Clinical Significance of NKD Inhibitor of WNT Signaling Pathway 1 (NKD1) in Glioblastoma.","date":"2023","source":"Genetics research","url":"https://pubmed.ncbi.nlm.nih.gov/36969985","citation_count":3,"is_preprint":false},{"pmid":"40675969","id":"PMC_40675969","title":"NKD1 enhances colon cancer progression by inhibiting the autophagic degradation of MYC.","date":"2025","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/40675969","citation_count":1,"is_preprint":false},{"pmid":"31472047","id":"PMC_31472047","title":"miR-532 promotes colorectal cancer invasion and metastasis by targeting NKD1.","date":"2019","source":"Cellular and molecular biology (Noisy-le-Grand, France)","url":"https://pubmed.ncbi.nlm.nih.gov/31472047","citation_count":1,"is_preprint":false},{"pmid":"37202194","id":"PMC_37202194","title":"[NKD1 promotes glucose uptake in colon cancer cells by activating YWHAE transcription].","date":"2023","source":"Nan fang yi ke da xue xue bao = Journal of Southern Medical University","url":"https://pubmed.ncbi.nlm.nih.gov/37202194","citation_count":1,"is_preprint":false},{"pmid":"37338734","id":"PMC_37338734","title":"NKD1 targeting PCM1 regulates the therapeutic effects of homoharringtonine on colorectal cancer.","date":"2023","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/37338734","citation_count":1,"is_preprint":false},{"pmid":"41526338","id":"PMC_41526338","title":"Wnt3a promotes in situ dentin formation through NKD1-MSX1 axis-mediated odontogenic differentiation of dental pulp stem cells.","date":"2026","source":"International journal of oral science","url":"https://pubmed.ncbi.nlm.nih.gov/41526338","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":14693,"output_tokens":4848,"usd":0.0584},"stage2":{"model":"claude-opus-4-6","input_tokens":8453,"output_tokens":3743,"usd":0.20376},"total_usd":0.26216,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"Human NKD1 was cloned and characterized as a Dishevelled-binding protein with an EF-hand motif in the NH2 domain, functioning as a negative regulator of the WNT–β-catenin–TCF signaling pathway, orthologous to mouse Nkd.\",\n      \"method\": \"Molecular cloning, sequence analysis, domain characterization\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — cloning and domain characterization; foundational paper replicated by subsequent functional studies\",\n      \"pmids\": [\"11604995\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The EF-hand motif of Nkd1 is required for its inhibitory function on Wnt/β-catenin signaling; mice expressing EF-hand-deleted Nkd1 show increased nuclear β-catenin in elongating spermatids and reduced sperm count, but no intestinal polyposis effect in Apc-mutant background.\",\n      \"method\": \"Targeted mouse knockout (EF-hand deletion), nuclear β-catenin localization by immunostaining, sperm count and testis weight measurements, genetic epistasis with Apc mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo loss-of-function with defined molecular phenotype and domain mutagenesis, replicated by subsequent structural/functional studies\",\n      \"pmids\": [\"15546883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Mouse Nkd1 and Nkd2 proteins bind Dvl proteins and inhibit Wnt signaling; targeted replacement of nkd exons encoding Dvl-binding sequences with lacZ/neomycin cassettes generates viable double-knockout mice with subtle cranial bone morphology alterations reminiscent of axin2 mutation, demonstrating partial functional redundancy.\",\n      \"method\": \"Gene targeting (IRES-lacZ/neomycin knock-in), double-knockout mouse generation, skeletal analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal genetic loss-of-function with defined cellular/developmental phenotype; Dvl-binding domain ablation confirmed mechanistically\",\n      \"pmids\": [\"17438140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"NKD1 mutations found in colorectal tumors reduce its ability to bind and destabilize Dvl proteins, leading to β-catenin stabilization and increased cell proliferation, directly implicating NKD1 in Wnt-dependent tumorigenesis.\",\n      \"method\": \"Mutation identification in patient tumors, co-immunoprecipitation (NKD1–Dvl binding), β-catenin stabilization assay, cell proliferation assay, luciferase Wnt reporter assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (Co-IP, reporter, proliferation) with patient-derived mutations and functional rescue\",\n      \"pmids\": [\"19956716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Zebrafish Nkd1 promotes Dvl degradation upon overexpression; knockdown of Nkd1 specifically in dorsal forerunner cells results in β-catenin nuclear localization, transcriptional activation, impaired DFC migration, defective KV formation and ciliogenesis, and disrupted left-right patterning.\",\n      \"method\": \"Zebrafish morpholino knockdown (DFC-specific), Nkd1 overexpression, β-catenin nuclear localization imaging, KV formation and ciliogenesis analysis, asymmetric charon expression assay\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific knockdown with multiple orthogonal readouts including molecular (β-catenin localization, Dvl degradation) and developmental phenotypes\",\n      \"pmids\": [\"20858476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Nkd1 functions as a passive antagonist of Wnt/β-catenin signaling, with its antagonistic activity enhanced in Wnt/Planar Cell Polarity pathway mutants (slb/wnt11 and tri/vangl2), suggesting Nkd1 acts to buffer destabilized or breached Wnt signaling rather than constitutively suppressing it.\",\n      \"method\": \"Zebrafish genetic epistasis using Wnt/PCP mutant lines (silberblick, trilobite), Wnt8a overexpression dorsalization assay, Nkd1 rescue experiments\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in multiple mutant backgrounds with functional rescue, single lab\",\n      \"pmids\": [\"24009776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Nkd1 activity is specifically dependent on Wnt ligand activation of the receptor; Nkd1 is recruited to the Wnt signalosome with Dvl2 upon ligand stimulation, then moves into the cytoplasm to interact with β-catenin and inhibit its nuclear accumulation.\",\n      \"method\": \"Zebrafish blastula Wnt-responsive cell assay, Wnt ligand stimulation, co-immunoprecipitation (Nkd1–Dvl2, Nkd1–β-catenin), subcellular fractionation/localization\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (Co-IP, fractionation, functional assay) establishing pathway position and molecular interactions\",\n      \"pmids\": [\"25904337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"NKD1 is an immediate early transcriptional target of FGF receptor signaling in endoderm; NKD1 loss suppresses hepatic progenitor cell formation from human iPSCs, and this phenotype is rescued by pharmacological antagonism of canonical WNT signaling, placing NKD1 downstream of FGFR and upstream of WNT inhibition in hepatic specification.\",\n      \"method\": \"Human iPSC differentiation, FGFR inhibition and stimulation, NKD1 knockdown, pharmacological WNT antagonist rescue, hepatic progenitor marker analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (KD + pharmacological rescue) with functional developmental readout in human stem cell system\",\n      \"pmids\": [\"26637527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NKD1 interacts with Rac1 in the cytoplasm and promotes its degradation via the ubiquitin-proteasome pathway; NKD1 overexpression attenuates HCC cell migration and invasion by downregulating Rac1 expression and activity, affecting the cytoskeleton and E-cadherin expression. Conversely, Rac1 negatively regulates EZH2, which enhances NKD1 transcription, forming a NKD1/Rac1 feedback loop.\",\n      \"method\": \"Co-immunoprecipitation (NKD1–Rac1), overexpression/knockdown in HCC cells, ubiquitin-proteasome pathway inhibitor assay, in vitro and in vivo migration/invasion assays, cytoskeleton imaging\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, proteasome inhibitor confirmation, and functional in vitro/in vivo assays; single lab\",\n      \"pmids\": [\"27231134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Rnf25/AO7 E3 ubiquitin ligase physically interacts with both Nkd1 and Axin in an E3-ligase-independent manner, disrupting the Nkd1–Axin inhibitory complex to positively regulate Wnt signaling; this distinguishes Nkd1 from Nkd2 (which is ubiquitinated by Rnf25).\",\n      \"method\": \"Co-immunoprecipitation (Rnf25–Nkd1, Rnf25–Axin), zebrafish rnf25 knockdown with Wnt target gene readout, E3-ligase dead mutant analysis\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP with mechanistic E3-ligase mutant controls and in vivo zebrafish validation; single lab\",\n      \"pmids\": [\"27007149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The lncRNA H19 binds EZH2 in glioblastoma cells and recruits it to the NKD1 promoter, promoting H3K27 trimethylation and transcriptional repression of NKD1; H19 knockdown impairs EZH2 binding to the NKD1 promoter.\",\n      \"method\": \"RNA immunoprecipitation (H19–EZH2), chromatin immunoprecipitation (EZH2 at NKD1 promoter), H19 knockdown with NKD1 expression measurement, H3K27me3 analysis\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — RIP and ChIP with functional gene expression readout; single lab, moderate evidence\",\n      \"pmids\": [\"29643989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"By interacting with EZH2, the lncRNA HNF1A-AS1 promotes repression of NKD1 expression in HCC cells to facilitate cell proliferation and S-phase progression.\",\n      \"method\": \"RNA immunoprecipitation (HNF1A-AS1–EZH2), chromatin immunoprecipitation (EZH2 at NKD1 promoter), HNF1A-AS1 knockdown/overexpression, cell proliferation and cell cycle analysis\",\n      \"journal\": \"Biomedicine & pharmacotherapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — RIP and ChIP with functional readout; single lab\",\n      \"pmids\": [\"28292020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NKD1 binds APC protein and promotes its ubiquitination-dependent degradation by suppressing the deubiquitinase USP15 and blocking the USP15–APC interaction, thereby paradoxically enhancing β-catenin nuclear accumulation and colon cancer cell proliferation in this context.\",\n      \"method\": \"Co-immunoprecipitation (NKD1–APC, USP15–APC), ubiquitination assay, β-catenin nuclear localization assay, NKD1 knockout cell line, cell proliferation/migration assays\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, ubiquitination assay, and functional rescue; single lab\",\n      \"pmids\": [\"36445120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NKD1 protein binds directly to the YWHAE gene promoter and activates YWHAE transcription, thereby promoting glucose uptake in colon cancer cells; NKD1 and YWHAE proteins also co-localize in colon cancer cells.\",\n      \"method\": \"Chromatin immunoprecipitation (NKD1 at YWHAE promoter), dual-luciferase reporter assay, NKD1 overexpression/knockout, immunofluorescence co-localization, glucose uptake assay\",\n      \"journal\": \"Journal of Southern Medical University\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP and luciferase reporter with functional glucose uptake readout; single lab\",\n      \"pmids\": [\"37202194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NKD1 interacts with PCM1 and promotes PCM1 degradation through the ubiquitin-proteasome pathway; PCM1 overexpression reverses the cell-cycle inhibition caused by NKD1 depletion in colorectal cancer cells.\",\n      \"method\": \"Co-immunoprecipitation (NKD1–PCM1), quantitative proteomics, ubiquitin-proteasome pathway assay, siRNA knockdown, cell cycle analysis, rescue experiment with PCM1 overexpression\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus proteomic discovery and functional rescue; single lab\",\n      \"pmids\": [\"37338734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Nkd1 functions downstream of Axin2 in the Wnt negative feedback cascade; zebrafish axin2/nkd1 double mutants phenocopy nkd1 single mutants at the level of Wnt target gene expression and protein profiles, placing Nkd1 epistatically downstream of Axin2. Both regulators share defects in heart looping, neuromast migration, and behavior, but show no synergy in the double mutant.\",\n      \"method\": \"CRISPR/Cas9 axin2, nkd1 single and double mutant zebrafish, qRT-PCR, RNA-seq, mass spectrometry proteomics of Wnt target gene expression, phenotypic analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple orthogonal molecular readouts (qRT-PCR, RNA-seq, proteomics) in well-controlled CRISPR mutants\",\n      \"pmids\": [\"38656801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"YTHDF3 (m6A reader) suppresses NKD1 transcription and translation in an m6A-dependent manner, thereby activating WNT/β-catenin signaling and promoting HCC invasion and metastasis.\",\n      \"method\": \"RNA-seq, meRIP-seq, Lace-seq (m6A site identification), YTHDF3 knockdown/overexpression, Western blot and qPCR for NKD1 expression, in vitro and in vivo invasion/metastasis assays\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multi-omics identification of m6A modification site on NKD1 mRNA with functional validation; single lab\",\n      \"pmids\": [\"39127439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NKD1 inhibits autophagic degradation of MYC protein by suppressing the interaction between LC3B and MYC; NKD1 binds MYC through its EF-hand domain, facilitates MYC nuclear entry, and thereby activates MYC target genes to promote colon cancer cell proliferation, migration, and angiogenesis. PPARδ was identified as a transcription factor driving NKD1 gene expression.\",\n      \"method\": \"NKD1 knockout cell line (SW620-nkd1-/-), differential proteomics, co-immunoprecipitation (NKD1–MYC, LC3B–MYC), EF-hand domain mutant analysis, autophagy assays, nuclear fractionation, ChIP (PPARδ at NKD1 promoter), functional cell assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, domain mutagenesis, autophagy pathway analysis with functional readout; single lab, recent publication\",\n      \"pmids\": [\"40675969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Wnt3a signaling upregulates NKD1 and MSX1 expression in dental pulp stem cells; NKD1 undergoes membrane detachment and directly interacts with MSX1 to promote its nuclear translocation, where MSX1 occupies promoters of odontogenic regulators to drive odontoblast differentiation and dentin formation.\",\n      \"method\": \"Single-cell transcriptomics, CUT&Tag (MSX1 ChIP-seq), co-immunoprecipitation/co-localization (NKD1–MSX1), NKD1 membrane detachment imaging, Wnt3a stimulation, murine pulp exposure model, SCENIC gene regulatory network analysis\",\n      \"journal\": \"International journal of oral science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, CUT&Tag, in vivo model with multiple orthogonal approaches; single lab, very recent publication\",\n      \"pmids\": [\"41526338\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NKD1 is a negative feedback regulator of canonical Wnt/β-catenin signaling that, upon Wnt ligand stimulation, is recruited to the Wnt signalosome with Dvl, then binds and destabilizes Dvl proteins and interacts with β-catenin via its EF-hand domain to inhibit nuclear β-catenin accumulation; it functions epistatically downstream of Axin2, can be epigenetically silenced by lncRNA-EZH2 complexes or suppressed by m6A readers, and also has non-canonical roles including promoting Rac1 and PCM1 degradation via the ubiquitin-proteasome pathway, inhibiting MYC autophagic degradation through LC3B competition, and activating YWHAE transcription, collectively influencing cancer cell proliferation, migration, and developmental processes such as spermatogenesis, left-right patterning, hepatic specification, and odontoblast differentiation.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NKD1 is a Wnt-inducible negative feedback regulator of canonical Wnt/β-catenin signaling that also exerts Wnt-independent functions in protein degradation, transcriptional activation, and autophagy modulation. Upon Wnt ligand stimulation, NKD1 is recruited to the Wnt signalosome with Dvl2, then moves into the cytoplasm where it binds and destabilizes Dvl proteins via its conserved Dvl-binding domain and interacts with β-catenin through its EF-hand motif to inhibit β-catenin nuclear accumulation; it functions epistatically downstream of Axin2 in this negative feedback cascade [PMID:25904337, PMID:38656801, PMID:15546883]. Beyond canonical Wnt antagonism, NKD1 promotes ubiquitin-proteasome-dependent degradation of Rac1 and PCM1, inhibits autophagic degradation of MYC by competing with LC3B binding, directly activates YWHAE transcription, and interacts with MSX1 to facilitate its nuclear translocation during odontoblast differentiation [PMID:27231134, PMID:37338734, PMID:40675969, PMID:37202194, PMID:41526338]. NKD1 expression is regulated by FGF signaling in hepatic specification, by EZH2-recruiting lncRNAs (H19, HNF1A-AS1) that impose H3K27me3-mediated silencing at its promoter, and by the m6A reader YTHDF3 that suppresses its mRNA post-transcriptionally [PMID:26637527, PMID:29643989, PMID:39127439].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Identification of NKD1 as a Dvl-binding, EF-hand-containing antagonist of Wnt/β-catenin signaling established the gene's core molecular identity and pathway membership.\",\n      \"evidence\": \"Molecular cloning, domain analysis, and sequence comparison with Drosophila nkd in human cells\",\n      \"pmids\": [\"11604995\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional validation of Dvl-binding or EF-hand requirement in this study\", \"Mechanism of Wnt inhibition not resolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrating that the EF-hand motif is required for NKD1's inhibition of nuclear β-catenin accumulation in vivo established the first structure-function relationship and revealed a physiological role in spermatogenesis.\",\n      \"evidence\": \"EF-hand-deleted Nkd1 knock-in mice analyzed for nuclear β-catenin in spermatids and sperm count; epistasis with Apc mutation\",\n      \"pmids\": [\"15546883\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why EF-hand-deleted mice lack intestinal phenotype in Apc-mutant background remains unexplained\", \"Direct binding partner of the EF-hand domain was not identified at this stage\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Generation of Nkd1/Nkd2 double-knockout mice revealed partial functional redundancy between the two paralogs and subtle cranial bone phenotypes resembling Axin2 loss, linking Nkd proteins to Wnt feedback in skeletal patterning.\",\n      \"evidence\": \"Dvl-binding-domain-targeted Nkd1/Nkd2 double-knockout mice with skeletal analysis\",\n      \"pmids\": [\"17438140\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mild double-knockout phenotype suggests additional compensatory Wnt feedback mechanisms\", \"No biochemical readout of Wnt pathway activation in these mutants\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Discovery that colorectal tumor mutations in NKD1 reduce Dvl binding and destabilization, leading to β-catenin stabilization, provided direct evidence that NKD1 loss-of-function contributes to Wnt-driven tumorigenesis.\",\n      \"evidence\": \"Patient tumor mutation identification followed by Co-IP, Wnt reporter, and cell proliferation assays\",\n      \"pmids\": [\"19956716\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No in vivo tumor model with NKD1 mutation rescue\", \"Whether these mutations are driver or passenger events in CRC was not formally established\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Cell-type-specific Nkd1 knockdown in zebrafish DFC established that Nkd1 promotes Dvl degradation and restrains nuclear β-catenin to enable proper Kupffer's vesicle formation, ciliogenesis, and left-right axis patterning.\",\n      \"evidence\": \"DFC-targeted morpholino knockdown with β-catenin localization, KV/cilia analysis, and asymmetric gene expression readouts\",\n      \"pmids\": [\"20858476\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of Dvl degradation (proteasomal vs lysosomal) not distinguished\", \"Whether Nkd1 role in LR patterning is conserved in mammals not tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Two studies established that NKD1 is specifically activated by Wnt ligand engagement—being recruited to the signalosome with Dvl2, then redistributing to the cytoplasm to bind β-catenin—and that FGF signaling induces NKD1 as an immediate-early gene required for hepatic specification from human iPSCs.\",\n      \"evidence\": \"Zebrafish Wnt-responsive cell assay with Co-IP and subcellular fractionation (Nkd1–Dvl2, Nkd1–β-catenin); human iPSC hepatic differentiation with NKD1 knockdown and WNT antagonist rescue\",\n      \"pmids\": [\"25904337\", \"26637527\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Nkd1 membrane detachment is triggered biochemically was not resolved\", \"Whether FGF-induced NKD1 acts identically to Wnt-induced NKD1 in molecular mechanism\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"NKD1 was shown to interact with Rac1 and promote its proteasomal degradation, establishing a Wnt-independent function in cell migration control, while Rnf25 was found to disrupt the Nkd1–Axin complex in a ligase-independent manner to modulate Wnt signaling.\",\n      \"evidence\": \"Co-IP (NKD1–Rac1) with proteasome inhibitor treatment, migration/invasion assays in HCC cells; Co-IP (Rnf25–Nkd1/Axin) with E3-ligase-dead mutant in zebrafish\",\n      \"pmids\": [\"27231134\", \"27007149\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether NKD1 itself serves as an E3 ligase adaptor for Rac1 ubiquitination is unknown\", \"Rnf25–Nkd1 interaction not validated in mammalian cells\", \"Single-lab findings for both\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Multiple lncRNAs (HNF1A-AS1, H19) were found to recruit EZH2 to the NKD1 promoter for H3K27me3-mediated transcriptional silencing, establishing epigenetic repression as a major mechanism of NKD1 downregulation in cancer.\",\n      \"evidence\": \"RIP (lncRNA–EZH2) and ChIP (EZH2/H3K27me3 at NKD1 promoter) in HCC and glioblastoma cells with lncRNA knockdown\",\n      \"pmids\": [\"28292020\", \"29643989\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Each lncRNA–EZH2–NKD1 axis demonstrated in a single lab/cancer type\", \"No in vivo validation of epigenetic silencing effects on NKD1\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A paradoxical pro-tumorigenic role was uncovered in which NKD1 binds APC and promotes its ubiquitination by suppressing USP15, thereby enhancing β-catenin nuclear accumulation in colon cancer—contrasting the canonical model of NKD1 as a Wnt antagonist.\",\n      \"evidence\": \"Co-IP (NKD1–APC, USP15–APC), ubiquitination assays, NKD1 knockout colon cancer cell lines\",\n      \"pmids\": [\"36445120\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Apparent contradiction with canonical Wnt-inhibitory function not reconciled\", \"Single-lab finding; no independent replication\", \"Cell-type or context specificity not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"NKD1 was shown to directly bind the YWHAE promoter to activate its transcription and to interact with PCM1 to promote its proteasomal degradation, expanding NKD1's roles to transcriptional activation and centrosome-associated protein homeostasis in colon cancer.\",\n      \"evidence\": \"ChIP and luciferase reporter for NKD1 at YWHAE promoter; Co-IP (NKD1–PCM1) with quantitative proteomics and cell cycle rescue\",\n      \"pmids\": [\"37202194\", \"37338734\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"DNA-binding domain of NKD1 not identified; mechanism of transcriptional activation unclear\", \"Each interaction reported by a single lab\", \"PCM1 degradation pathway (direct adaptor vs indirect) not resolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Genetic epistasis using CRISPR mutants demonstrated that Nkd1 functions downstream of Axin2 in the Wnt negative feedback hierarchy, while YTHDF3-mediated m6A modification was shown to suppress NKD1 mRNA to activate Wnt signaling in HCC.\",\n      \"evidence\": \"Zebrafish axin2/nkd1 single and double CRISPR mutants with RNA-seq and proteomics; meRIP-seq and YTHDF3 manipulation in HCC cells\",\n      \"pmids\": [\"38656801\", \"39127439\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Nkd1 is positioned downstream of Axin2 biochemically is not resolved\", \"Whether YTHDF3 regulation of NKD1 is tissue-specific or generalizable is unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"NKD1 was found to inhibit MYC autophagic degradation by competing with LC3B for MYC binding through its EF-hand domain, facilitating MYC nuclear entry and target gene activation, revealing a direct oncogenic mechanism in colon cancer.\",\n      \"evidence\": \"NKD1-knockout SW620 cells, Co-IP (NKD1–MYC, LC3B–MYC), EF-hand domain mutagenesis, autophagy assays, nuclear fractionation, ChIP of PPARδ at NKD1 promoter\",\n      \"pmids\": [\"40675969\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab finding; no independent replication\", \"Whether MYC protection by NKD1 operates in non-cancer contexts unknown\", \"Structural basis for LC3B–MYC competition not determined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"NKD1 was shown to undergo Wnt3a-induced membrane detachment and interact with MSX1 to drive its nuclear translocation and occupancy of odontogenic gene promoters, linking NKD1 to odontoblast differentiation and dentin formation.\",\n      \"evidence\": \"Single-cell transcriptomics, CUT&Tag, Co-IP (NKD1–MSX1), membrane detachment imaging in dental pulp stem cells, murine pulp exposure model\",\n      \"pmids\": [\"41526338\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab finding in dental pulp stem cells\", \"Membrane detachment mechanism not molecularly defined\", \"Whether MSX1 interaction requires EF-hand or Dvl-binding domain unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the structural basis for how NKD1's EF-hand domain engages β-catenin vs MYC vs MSX1; how NKD1 switches between Wnt-antagonistic and context-dependent pro-tumorigenic functions (e.g., APC degradation, MYC stabilization); and whether NKD1's roles in proteasomal degradation of Rac1 and PCM1 involve specific E3 ligase recruitment.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal or cryo-EM structure of NKD1 or its complexes\", \"Context-dependent switch between tumor suppressor and oncogene not mechanistically resolved\", \"E3 ligase adaptors for NKD1-mediated degradation targets not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 3, 4, 6, 15]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [6, 18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 3, 4, 6, 15]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4, 7, 18]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [8, 14]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [3, 12, 17]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"DVL2\", \"CTNNB1\", \"RAC1\", \"PCM1\", \"MYC\", \"APC\", \"MSX1\", \"RNF25\"],\n    \"other_free_text\": []\n  }\n}\n```"}