Affinage

NDP

Norrin · UniProt Q00604

Length
133 aa
Mass
15.0 kDa
Annotated
2026-06-10
100 papers in source corpus 29 papers cited in narrative 29 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 8/8 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

Norrin (NDP) is a secreted cystine-knot growth factor that drives canonical Wnt/β-catenin signaling in vascular endothelium to control CNS and retinal angiogenesis and blood-barrier formation and maintenance (PMID:15035989, PMID:19837032, PMID:23217714). Biochemically it is secreted as disulfide-bonded dimers and higher-order oligomers associated with the extracellular matrix, with Cys95 required for oligomerization beyond dimers (PMID:9407136); each monomer adopts a cystine-knot fold, and the dimer interface is required for receptor activation (PMID:24186977). Norrin acts as an atypical, Wnt-mimetic ligand that binds specifically and with high affinity to the cysteine-rich domain (CRD) of Frizzled-4 and not to other Frizzled CRDs, contacting Fz4 through patches that overlap the Wnt-recognition surface while using a separate site to engage the LRP5/6 co-receptor, thereby nucleating a ternary Norrin–Fz4–LRP5/6 complex rather than inducing Fz4 dimerization (PMID:15035989, PMID:26158506, PMID:24186977, PMID:17158104). Signaling output is selectively amplified by the tetraspanin co-receptor TSPAN12, which interacts directly with FZD4 and Norrin, promotes receptor-complex multimerization, and confers ligand selectivity for Norrin over Wnt (PMID:19837033, PMID:28658627). Norrin-induced FZD4 ubiquitination and trafficking of the receptor complex into the endo-lysosomal/MVB compartment via the ESCRT pathway is required for full β-catenin signaling and for normal CNS vascular and barrier development (PMID:28675177). Downstream, endothelial β-catenin activation induces an angiogenic and barrier program—including Sox17 and tight-junction proteins—while in Müller glia Norrin/β-catenin drives secretion of neuroprotective and angiogenic factors (FGF2, BDNF, Ang-2, IGF-1) that support endothelial growth and retinal neuron survival (PMID:19837032, PMID:20427659, PMID:20053900, PMID:26706283). Loss-of-function and disease-associated NDP and FZD4 variants disrupt secretion, receptor binding, or signaling, and transgenic re-expression of Norrin rescues retinal vascular defects in Ndp-null mice, establishing Norrin as causative for the inherited vascular retinopathies of the Norrie disease/FEVR spectrum (PMID:9407136, PMID:15716406, PMID:21177847, PMID:17955262). Beyond the vascular Wnt axis, Norrin also signals through the LGR4 receptor and, in glioblastoma stem cells, can activate Notch independently of Wnt depending on ASCL1 status (PMID:23444378, PMID:32182224).

Mechanistic history

Synthesis pass · year-by-year structured walk · 18 steps
  1. 1997 High

    Established the secreted, oligomeric, ECM-associated nature of Norrin before its receptor was known, defining the biochemical form in which the ligand acts.

    Evidence Pulse-chase radiolabeling, non-reducing SDS-PAGE, crosslinking and mutagenesis of Cys95 and disease variants in transfected cells

    PMID:9407136

    Open questions at the time
    • Did not identify a receptor or signaling pathway
    • Functional consequence of oligomerization for signaling not tested
  2. 2004 High

    Identified Norrin as a high-affinity, Frizzled-4-specific ligand that activates canonical Wnt/β-catenin signaling in an Fz4/Lrp-dependent manner, unifying NDP and FZD4 genetics into one pathway.

    Evidence Binding assays, cell-based β-catenin reporter assays, and comparison of Norrin and Fz4 mutant mice and humans

    PMID:15035989

    Open questions at the time
    • Structural basis of Fz4 selectivity not resolved
    • Co-receptor requirements beyond Lrp not defined
  3. 2006 High

    Defined the structural determinants of Norrin–Fz4 specificity, showing it recognizes the Fz4 CRD over 13 other CRDs through the cystine knot and overlaps the Wnt8 binding region, with heparin enhancing binding.

    Evidence Binding specificity panel across 14 Frizzled CRDs, mutagenesis of Norrin and Fz4/Fz8 chimeras, heparin competition

    PMID:17158104

    Open questions at the time
    • Atomic structure not yet determined
    • Role of GAG binding in vivo unknown
  4. 2009 High

    Showed Norrin/Fz4/Lrp signaling acts cell-autonomously in endothelium to drive retinal vascular growth and barrier integrity, identifying Sox17 as a transcriptional effector of the angiogenic program.

    Evidence Endothelial-specific conditional Fz4 deletion, cell-culture signaling assays, gene expression analysis

    PMID:19837032

    Open questions at the time
    • Full downstream transcriptional network not mapped
    • Mechanism of barrier-specific output not resolved
  5. 2009 High

    Identified TSPAN12 as a component that multimerizes the Norrin/FZD4 complex and selectively amplifies Norrin (not Wnt) β-catenin signaling, explaining ligand-specific pathway control.

    Evidence Co-IP, siRNA knockdown, overexpression, mouse knockout phenocopy, β-catenin reporter assays

    PMID:19837033 PMID:28658627

    Open questions at the time
    • Molecular basis of Norrin-vs-Wnt selectivity not yet structural
    • Stoichiometry of the multimeric complex unknown
  6. 2010 Medium

    Connected Norrin/β-catenin signaling to non-cell-autonomous outputs: Müller-glial induction of neuroprotective factors and endothelial proliferation/angiogenesis mediated by Ang-2.

    Evidence Intravitreal Norrin, DKK-1 blockade, conditioned-medium transfer, anti-Ang-2 inhibition, in vitro endothelial assays, OIR model

    PMID:20053900 PMID:20427659

    Open questions at the time
    • RGC-5 line and conditioned-medium model are indirect
    • Relative contributions of individual secreted factors not dissected
  7. 2012 High

    Demonstrated a continuing requirement for Norrin/Fz4 signaling in mature CNS endothelium for ongoing blood-retina and blood-brain barrier maintenance, not just development.

    Evidence Conditional gain/loss-of-function and mosaic mouse genetics with vascular permeability assays

    PMID:23217714

    Open questions at the time
    • Molecular targets sustaining the mature barrier not fully enumerated
  8. 2013 High

    Determined the Norrin crystal structure, establishing a cystine-knot dimer with separate Fz4 and Lrp5/6 sites that assembles a ternary complex, providing the mechanistic framework for receptor engagement.

    Evidence X-ray crystallography, mutagenesis, binding assays, Wnt reporter assays

    PMID:24186977

    Open questions at the time
    • Co-complex structure with receptors not yet solved
    • Conformational changes in Fz4 upon binding not visualized
  9. 2013 Medium

    Revealed receptor diversity by showing Norrin also functions as an LGR4-specific Wnt agonist, and that disease mutations can be partitioned by which downstream pathway they impair.

    Evidence Cell-based Wnt signaling and binding assays across LGR4/5/6, mutagenesis of disease variants

    PMID:23444378

    Open questions at the time
    • In vivo physiological role of Norrin–LGR4 signaling not established
    • Relationship to FZD4 axis unclear
  10. 2015 High

    Provided the Norrin–Fz4CRD co-structure, showing Wnt mimicry through distinct contact patches, mapped separate Lrp5/6 and GAG sites, and explained disease mutations structurally.

    Evidence X-ray crystallography, SAXS, biophysical binding and cell-based signaling assays with mutants

    PMID:26158506

    Open questions at the time
    • Full ternary receptor complex not captured
    • Transmembrane signal transmission not addressed
  11. 2017 High

    Established TSPAN12 as a direct co-receptor whose extracellular loops bind FZD4 and Norrin to confer ligand selectivity, and showed FEVR mutations exclude it from the complex.

    Evidence Reciprocal Co-IP, cell-based signaling, FEVR-mutant analysis, Xenopus rescue

    PMID:28658627

    Open questions at the time
    • Structure of TSPAN12 within the complex unknown
    • Quantitative contribution to receptor multimerization unresolved
  12. 2017 High

    Showed that Norrin-triggered FZD4 ubiquitination and ESCRT/MVB-dependent endo-lysosomal trafficking is required for full β-catenin signaling and CNS vascular development, adding a post-receptor regulatory layer.

    Evidence Ubiquitination/trafficking assays, dominant-negative VPS4 EQ, in vitro signaling and in vivo mouse vascular phenotyping

    PMID:28675177

    Open questions at the time
    • Identity of the responsible E3 ligase not defined
    • How trafficking enhances β-catenin output mechanistically unclear
  13. 2018 High

    Refined the receptor mechanism by showing the Fz4 stalk linker contributes ~10-fold to Norrin affinity and that binding induces conformational changes in the linker and ICL3 important for signaling.

    Evidence SPR binding, HDX-MS, mutagenesis (linker swaps, ICL3 mutants), β-catenin reporter assays

    PMID:30104375

    Open questions at the time
    • How ICL3 changes couple to intracellular effectors not defined
  14. 2018 High

    Defined functional redundancy between the Norrin and Wnt7a barrier systems, and positioned TSPAN12 as a less-potent coactivator that tunes Norrin signal amplitude.

    Evidence Compound conditional knockout epistasis, BBB/BRB permeability assays

    PMID:30478038

    Open questions at the time
    • Regional/temporal division of labor between ligands not fully mapped
  15. 2019 Medium

    Extended Norrin biology beyond vasculature, showing astroglial-secreted Norrin shapes neuronal dendrites/spines and that follicular Norrin acts non-cell-autonomously to drive hair growth.

    Evidence Astroglia-specific transgenics with spine quantification; dermal papilla transcriptomics, siRNA, β-catenin reporters, ex vivo hair follicle growth and EV transfer

    PMID:30936556 PMID:31237401

    Open questions at the time
    • Receptor/co-receptor identity in these contexts not fully defined
    • Single-lab observations
  16. 2020 Medium

    Revealed context-dependent pathway switching: Norrin activates Wnt in ASCL1-low glioblastoma stem cells but Notch independently of Wnt in ASCL1-high cells, with opposite tumor consequences; and VEGF licenses Norrin barrier responses via MEK/ERK-driven TSPAN12 surface expression.

    Evidence GSC cultures with NDP/FZD4 manipulation and ASCL1 rescue; endothelial barrier assays with VEGF co-treatment, pathway inhibitors, diabetic rat injections

    PMID:32086377 PMID:32182224

    Open questions at the time
    • Molecular switch determining Wnt-vs-Notch output unclear
    • GSK-3-independent barrier mechanism not fully resolved
  17. 2021 Medium

    Demonstrated sufficiency of the core receptor logic: a bispecific antibody forcing FZD4–LRP5 proximity recapitulates Norrin signaling and rescues Tspan12-/- and OIR vascular defects.

    Evidence Antibody engineering, β-catenin assays, Tspan12-/- rescue, OIR model, permeability assays

    PMID:34105895

    Open questions at the time
    • Whether forced proximity reproduces full trafficking-dependent signaling not tested
    • Single lab
  18. 2024 High

    Placed Norrin signaling under neuronal-activity control, showing glutamatergic activity tunes endothelial Norrin/β-catenin signaling to coordinate angiogenesis and barrier maturation with neural function.

    Evidence Vglut1-/- and Gnat1-/- mouse genetics, scRNA-seq, pharmacological pathway activation, vascular morphometry and permeability

    PMID:38599212

    Open questions at the time
    • Signal relay from glutamate sensing to Norrin expression not molecularly defined

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the choice between Norrin's distinct outputs (FZD4/β-catenin vs LGR4 vs Notch) is determined in different cell contexts, and the identity of the FZD4 E3 ubiquitin ligase coupling trafficking to signal strength, remain unresolved.
  • No defined molecular switch governing pathway selection
  • FZD4 ubiquitin ligase unidentified
  • In vivo role of Norrin-LGR4 axis untested

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0048018 receptor ligand activity 5 GO:0008289 lipid binding 2 GO:0060089 molecular transducer activity 2 GO:0098772 molecular function regulator activity 2
Localization
GO:0005576 extracellular region 3 GO:0031012 extracellular matrix 1
Pathway
R-HSA-1266738 Developmental Biology 3 R-HSA-162582 Signal Transduction 3 R-HSA-5653656 Vesicle-mediated transport 1
Partners
FZD4LGR4LRP5LRP6TSPAN12
Complex memberships
Norrin-FZD4-LRP5/6 ternary signaling complexNorrin/FZD4/TSPAN12 receptor complex

Evidence

Reading pass · 29 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2004 Norrin (NDP) functions as a high-affinity ligand for Frizzled-4 (Fz4) receptor, binding specifically to Fz4 and not other Frizzled family members, and activates the classical (canonical) Wnt/β-catenin pathway in an Fz4- and Lrp-dependent manner. Disease-associated variants of Norrin and Fz4 display signaling defects. Binding assays, cell-based canonical Wnt pathway reporter assays, genetic phenotype comparison between Norrin and Fz4 mutant mice and humans Cell High 15035989
2009 TSPAN12 (tetraspanin-12) associates with the Norrin/Frizzled4 receptor complex, promotes multimerization of FZD4 and associated proteins, and selectively amplifies Norrin/β-catenin signaling but not Wnt/β-catenin signaling. TSPAN12 siRNA abolishes transcriptional responses to Norrin but not Wnt3A in retinal endothelial cells. TSPAN12 loss-of-function phenocopies Norrin, Fzd4, and Lrp5 mutant retinal vascular defects in mice. Co-immunoprecipitation, siRNA knockdown, overexpression, mouse genetics (knockout), cell-based β-catenin reporter assays Cell High 19837033 28658627
2009 Norrin/Fz4/Lrp signaling acts specifically in endothelial cells to control retinal vascular growth and blood-brain barrier integrity. Sox17, a transcription factor upregulated by Norrin/Fz4/Lrp signaling, plays a central role in inducing the angiogenic program. Excessive Fz4 signaling disrupts embryonic angiogenesis. Conditional mouse genetics (endothelial-specific Fz4 deletion), cell culture Norrin/Fz4/Lrp signaling assays, gene expression analysis Cell High 19837032
2012 Norrin/Fz4 signaling in adult retinal and cerebellar endothelial cells maintains blood-retina barrier and blood-brain barrier function in a cell-autonomous manner, demonstrating ongoing plasticity and requirement for Frizzled signaling in mature CNS vascular barrier maintenance. Conditional gain- and loss-of-function mouse genetics, genetic mosaic analysis, vascular permeability assays Cell High 23217714
2015 Crystal structure of Norrin in complex with Fz4 cysteine-rich domain (Fz4CRD) revealed that Norrin mimics Wnt for Frizzled recognition, using structurally distinct patches to contact Fz4. The structure maps separate binding sites on Norrin for Fz4 and Lrp5/6, and identifies a glycosaminoglycan (GAG) binding site spanning Norrin and Fz4CRD. Disease-associated mutations are explained by these structural findings. X-ray crystallography, small-angle X-ray scattering (SAXS), biophysical binding assays, cell-based signaling assays with mutants eLife High 26158506
2013 Crystal structure of Norrin reveals a unique dimeric architecture with each monomer adopting a cystine knot fold. The dimer interface is required for Fz4 activation. Norrin contains separate binding sites for Fz4 and for Lrp5/Lrp6 and induces formation of a ternary Norrin-Fz4-Lrp5/6 complex rather than inducing Fz4 dimerization. X-ray crystallography, site-directed mutagenesis, co-immunoprecipitation/binding assays, cell-based Wnt reporter assays Genes & development High 24186977
2006 Norrin binds specifically to the Fz4 cysteine-rich domain (CRD) and does not detectably bind to 14 other mammalian Frizzled or secreted Frizzled-related protein CRDs. Norrin and Xenopus Wnt8 recognize largely overlapping regions on the Fz4 CRD. Norrin binding depends critically on three disulfide bonds forming the cystine knot and on a largely contiguous group of amino acids in the extended beta-sheet domain. Heparin enhances Norrin-CRD binding ~10-fold. Binding specificity assays across 14 Frizzled CRDs, site-directed mutagenesis of Norrin and Fz4/Fz8 chimeras, heparin competition binding The Journal of biological chemistry High 17158104
1997 Norrin is a secreted protein that forms disulfide-bonded oligomers (up to ~20 monomers) associated with the extracellular matrix. Cysteine-95 is required for oligomer formation beyond dimers. Disease-associated mutations (V60E, R121Q) reduce the amount of Norrin in the extracellular matrix of transfected cells. Pulse-chase radiolabeling, SDS-PAGE under reducing and non-reducing conditions, chemical crosslinking, site-directed mutagenesis of Cys95 and disease variants The Journal of biological chemistry High 9407136
2017 TSPAN12 acts as a co-receptor for the Norrin/FZD4 signaling complex: it interacts directly with FZD4 and NDP via its extracellular loops, enhances FZD4 ligand selectivity for NDP over Wnt, and is an essential component of the NDP receptor complex. FEVR-linked TSPAN12 mutations prevent its incorporation into the NDP receptor complex. TSPAN12 can rescue defects of FZD4 M105V (a mutation destabilizing NDP/FZD4 interaction) in vitro and in Xenopus. Co-immunoprecipitation, cell-based signaling assays, FEVR-mutant functional analysis, Xenopus rescue experiments Cell reports High 28658627
2018 The flexible linker domain connecting the Fz4 CRD to the transmembrane domain directly contributes to high-affinity Norrin/Fz4 interaction (~10-fold higher affinity than CRD alone). Swapping the Fz4 linker with Fz5 linker abolishes Norrin signaling. Norrin binding induces conformational changes in the Fz4 linker and intracellular loop 3 (ICL3), and ICL3 mutations (L430A, L433A) reduce β-catenin signaling. Biophysical binding assays (SPR), hydrogen-deuterium exchange mass spectrometry, site-directed mutagenesis, cell-based β-catenin reporter assays Proceedings of the National Academy of Sciences of the United States of America High 30104375
2017 Norrin triggers FZD4 ubiquitination and induces internalization of the NDP/FZD4 receptor complex into the endo-lysosomal compartment via the multivesicular body (MVB)/ESCRT pathway. Inhibiting ubiquitinated cargo transport through the MVB pathway (dominant-negative VPS4 EQ) strongly impairs NDP/FZD4 β-catenin signaling in vitro and causes CNS angiogenesis and blood-CNS barrier defects in mice. Ubiquitination assays, endocytosis/trafficking assays, dominant-negative ESCRT overexpression (VPS4 EQ), in vitro signaling assays, in vivo mouse vascular phenotyping Nature communications High 28675177
2010 Norrin activates Wnt/β-catenin signaling in Müller glia, which then induces neuroprotective growth factors (FGF2, BDNF, CNTF, LEGF, LIF, EDN2). Conditioned medium from Norrin-treated Müller cells increases survival of RGC-5 cells. These neuroprotective effects on retinal ganglion cells can be blocked by DKK-1 (a Wnt/β-catenin inhibitor). Intravitreal injection of Norrin + NMDA in mice, DKK-1 inhibitor experiments, primary Müller cell culture, conditioned medium transfer to RGC-5 cells, western blot and gene expression analysis The Journal of neuroscience : the official journal of the Society for Neuroscience Medium 20427659
2010 Norrin stimulates proliferation, viability, migration, and tube formation of microvascular endothelial cells in vitro. These effects are blocked by DKK-1. Norrin induces angiopoietin-2 (Ang-2) expression, and inhibitory antibodies against Ang-2 suppress Norrin's proliferative effects, placing Ang-2 as a downstream mediator. In vitro endothelial cell assays (proliferation, migration, tube formation), DKK-1 inhibition, anti-Ang-2 antibody inhibition, transgenic mouse OIR model The Journal of neuroscience : the official journal of the Society for Neuroscience Medium 20053900
2013 Norrin acts as a ligand for LGR4 receptor and stimulates Wnt signaling mediated by LGR4 (but not LGR5 or LGR6) in mammalian cells. Binding studies showed interactions between Norrin and LGR4, LGR5, and LGR6, but only LGR4 mediates signaling. Different Norrie disease mutations can be categorized by defects in signaling through FZD4 vs. LGR4 vs. BMP antagonism pathways. Cell-based Wnt signaling assays, binding studies, site-directed mutagenesis categorizing disease mutants Journal of cell science Medium 23444378
2018 Wnt7a and Norrin systems show partial redundancy in maintaining the blood-brain barrier and blood-retina barrier. Combined loss of Wnt7a and Norrin (or Wnt7a and Fz4) produces far more severe BBB defects than individual losses. Tspan12 functions as a coactivator less potent than Norrin in BBB maintenance, consistent with a model where Tspan12 amplifies Norrin signal amplitude in endothelial cells. Compound conditional knockout mouse genetics, BBB/BRB permeability assays, epistasis analysis Proceedings of the National Academy of Sciences of the United States of America High 30478038
2019 A molecularly defined subset of cortical astroglia (enriched in layer V) expresses and secretes Norrin. Astrocytic Norrin regulates neuronal dendrites and dendritic spines; loss of Norrin (as in Norrie disease) contributes to cortical dendritic spine loss. Transgenic mice with astroglia-specific promoter, transcriptomic analysis, histological analysis, loss-of-function dendritic spine quantification Nature neuroscience Medium 30936556
2014 Norrin protected blood-brain barrier integrity after subarachnoid hemorrhage via Frizzled-4 receptor activation, which promotes β-catenin nuclear translocation and enhances expression of tight junction proteins Occludin, VE-Cadherin, and ZO-1. These effects were abolished by Frizzled-4 siRNA pretreatment. Rat subarachnoid hemorrhage model, intracerebroventricular Norrin administration, Frizzled-4 siRNA knockdown, BBB permeability assays, western blot, immunofluorescence Stroke Medium 25550365
2020 Norrin restores blood-retinal barrier properties after VEGF-induced permeability in a β-catenin-dependent manner. VEGF promotes Norrin responsiveness by increasing TSPAN12 at cell membranes via an MEK/ERK-dependent mechanism. Norrin and VEGF together (but not separately) are required for enriched claudin-5 localization at tight junctions. GSK-3α/β inhibition does not restore BRB properties, suggesting the mechanism is not through GSK-3 inhibition alone. In vitro primary endothelial cell barrier assays (electrical resistance, RITC-dextran permeability), intravitreal co-injection in diabetic rats, western blot, β-catenin reporter assays The Journal of biological chemistry Medium 32086377
2005 Ectopic transgenic expression of Norrin under a lens-specific promoter restores normal retinal vascular network formation in Norrie disease (Ndp knockout) mice, rescuing the failure of deep capillary layer formation. Lenses expressing ectopic Norrin induce proliferation of co-cultured microvascular endothelial cells in vitro. Transgenic rescue in Ndp knockout mice, retinal vascular morphology, ERG functional analysis, in vitro co-culture endothelial proliferation assay The Journal of neuroscience : the official journal of the Society for Neuroscience High 15716406
2012 Norrin is expressed in Müller glia in the retina and activates canonical Wnt/β-catenin signaling through Frizzled-4 receptors. Loss of Norrin or Frizzled-4 prevents intraretinal capillary formation during developmental angiogenesis. Norrin stimulates endothelial cell proliferation in the superficial retinal vascular plexus, and loss of Norrin reduces proliferation of isolectin B4-positive endothelial cells. Elevated mural cell coverage in Ndp knockout mice is associated with altered PDGFβ and PDGFRβ expression. Ndp knockout mouse morphometric analysis, DAPT Notch inhibition, BrdU in vivo proliferation assays, PDGF pathway expression analysis Human molecular genetics Medium 22394677
2010 In FZD4 CRD mutants associated with FEVR (C45Y, Y58C, C204R), Norrin binding to FZD4 is abolished and FZD4-mediated Wnt/β-catenin signaling is abrogated. In vivo validation in Xenopus embryos showed these FZD4 mutations disrupt Norrin/β-catenin signaling as evidenced by decreased Siamois and Xnr3 expression. Cell-surface and overlay binding assays, luciferase reporter assays in HEK293, in vivo Xenopus β-catenin target gene expression The Journal of biological chemistry Medium 21177847
2007 Missense mutations in NDP found in FEVR patients caused variable but moderate reductions (rather than complete abolishment) in Norrin signaling activity in a Topflash reporter assay. Norrin mutants examined demonstrated impaired cell surface binding to FZD4, and some may have partially lost ability to form a complex with high molecular weight material(s). No single-missense Norrin mutant showed complete loss of signaling. Norrin-dependent Topflash reporter assay, cell surface binding assay, protein electrophoresis Human genetics Medium 17955262
2024 Glutamatergic neuronal activity regulates retinal angiogenesis and blood-retinal barrier maturation by modulating endothelial Norrin/β-catenin signaling. In Vglut1-/- retinas (where neurons fail to release glutamate), Norrin expression and endothelial Norrin/β-catenin signaling are downregulated; in Gnat1-/- retinas (excessive glutamate), they are upregulated. Pharmacological activation of endothelial Norrin/β-catenin signaling in Vglut1-/- retinas rescues deep plexus angiogenesis and paracellular BRB maturation defects. In vivo mouse genetic studies (Vglut1-/-, Gnat1-/- knockouts), scRNA-seq, pharmacological Norrin/β-catenin pathway activation, vascular morphometry and permeability assays Neuron High 38599212
2019 Dermal papilla cells (DPCs) stimulated by extracellular vesicles from activated dermal fibroblasts upregulate and secrete Norrin via the NDP gene, which then activates the β-catenin pathway in follicular keratinocytes in a non-cell-autonomous manner to promote hair follicle growth. FZD4 protein (delivered by EV) was required to potentiate Norrin effects. Transcriptomic analysis of DPCs, siRNA knockdown, β-catenin reporter assays, hair follicle ex vivo growth assays, EV transfer Stem cells (Dayton, Ohio) Medium 31237401
2020 In glioblastoma, Norrin signals through FZD4 to activate canonical Wnt signaling in ASCL1-low GSCs (tumor-suppressive effect) but promotes Notch signaling independently of WNT in ASCL1-high GSCs (tumor-promoting effect). Forced ASCL1 expression reversed tumor-suppressive effects of Norrin in ASCL1-low GSCs. GBM stem cell culture, NDP/FZD4 manipulation, Notch and Wnt pathway reporter assays, ASCL1 overexpression rescue, functional growth assays The Journal of clinical investigation Medium 32182224
2021 A tetravalent bispecific antibody (F4L5.13) designed to induce FZD4 and LRP5 proximity triggers β-catenin signaling in endothelial cells, rescues retinal angiogenesis and barrier function in Tspan12-/- mice, and normalizes neovascularization in an OIR model, demonstrating that forced FZD4-LRP5 co-engagement is sufficient to recapitulate Norrin/FZD4/LRP5 signaling. Antibody engineering, cell-based β-catenin signaling assays, Tspan12-/- mouse retinal phenotype rescue, OIR mouse model, vascular permeability assays EMBO molecular medicine Medium 34105895
2005 Female mice homozygous for Ndp knockout exhibit near-complete infertility due to defects in vascular development and decidualization in the uterus from E7 onwards, demonstrating a role for Norrin in female reproductive tissue vascular development. Ndp knockout mouse model, histological analysis, RNA in situ hybridization, RT-PCR expression analysis of uteri, deciduae, and human placenta Genesis (New York, N.Y. : 2000) Medium 16035034
2012 Norrin activates Wnt/β-catenin signaling and endothelin-2 (EDN2) signaling to protect photoreceptors from light-induced damage. The protective effects were abolished by intravitreal injection of DKK-1 (Wnt/β-catenin inhibitor) or BQ788 (EDN receptor B antagonist), establishing that both Wnt/β-catenin and EDN2 signaling are required for Norrin-mediated photoreceptor protection. Transgenic Norrin-overexpressing mice (Rpe65-Norrin), light damage model, intravitreal DKK-1 and BQ788 injections, ERG functional assays, apoptosis quantification Neurobiology of disease Medium 23009755
2015 Norrin induces IGF-1 expression via activation of the Wnt/β-catenin signaling pathway in Müller cells and endothelial cells. Inhibition of IGF-1 with antibodies significantly attenuates Norrin-mediated vascular repair in the OIR model, establishing IGF-1 as a downstream mediator of Norrin's angiogenic properties. Transgenic Norrin-overexpressing mice (βB1-Norrin), OIR model, DKK-1 inhibition, anti-IGF-1 antibody intravitreal injection, gene expression analysis Experimental eye research Medium 26706283

Source papers

Stage 0 corpus · 100 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2004 Vascular development in the retina and inner ear: control by Norrin and Frizzled-4, a high-affinity ligand-receptor pair. Cell 730 15035989
2009 Norrin, frizzled-4, and Lrp5 signaling in endothelial cells controls a genetic program for retinal vascularization. Cell 379 19837032
2012 Norrin/Frizzled4 signaling in retinal vascular development and blood brain barrier plasticity. Cell 332 23217714
2009 TSPAN12 regulates retinal vascular development by promoting Norrin- but not Wnt-induced FZD4/beta-catenin signaling. Cell 329 19837033
1993 A mutation in the Norrie disease gene (NDP) associated with X-linked familial exudative vitreoretinopathy. Nature genetics 284 8252044
2002 NDP kinase 2 interacts with two oxidative stress-activated MAPKs to regulate cellular redox state and enhances multiple stress tolerance in transgenic plants. Proceedings of the National Academy of Sciences of the United States of America 274 12506203
2010 The Norrin/Frizzled4 signaling pathway in retinal vascular development and disease. Trends in molecular medicine 149 20688566
1999 Coats' disease of the retina (unilateral retinal telangiectasis) caused by somatic mutation in the NDP gene: a role for norrin in retinal angiogenesis. Human molecular genetics 142 10484772
2018 Interplay of the Norrin and Wnt7a/Wnt7b signaling systems in blood-brain barrier and blood-retina barrier development and maintenance. Proceedings of the National Academy of Sciences of the United States of America 133 30478038
2010 Overview of the mutation spectrum in familial exudative vitreoretinopathy and Norrie disease with identification of 21 novel variants in FZD4, LRP5, and NDP. Human mutation 126 20340138
2010 Norrin mediates neuroprotective effects on retinal ganglion cells via activation of the Wnt/beta-catenin signaling pathway and the induction of neuroprotective growth factors in Muller cells. The Journal of neuroscience : the official journal of the Society for Neuroscience 113 20427659
2015 Structure and functional properties of Norrin mimic Wnt for signalling with Frizzled4, Lrp5/6, and proteoglycan. eLife 109 26158506
2013 Structure and function of Norrin in assembly and activation of a Frizzled 4-Lrp5/6 complex. Genes & development 103 24186977
2003 Multiple biochemical activities of NM23/NDP kinase in gene regulation. Journal of bioenergetics and biomembranes 96 12848339
2006 Mutational analysis of Norrin-Frizzled4 recognition. The Journal of biological chemistry 95 17158104
2019 NDP-MSH binding melanocortin-1 receptor ameliorates neuroinflammation and BBB disruption through CREB/Nr4a1/NF-κB pathway after intracerebral hemorrhage in mice. Journal of neuroinflammation 87 31660977
2000 Catalysis of DNA cleavage and nucleoside triphosphate synthesis by NM23-H2/NDP kinase share an active site that implies a DNA repair function. Proceedings of the National Academy of Sciences of the United States of America 83 11121025
2014 Norrin protected blood-brain barrier via frizzled-4/β-catenin pathway after subarachnoid hemorrhage in rats. Stroke 81 25550365
1992 Molecular cloning and functional expression of the second mouse nm23/NDP kinase gene, nm23-M2. FEBS letters 81 1325378
2017 TSPAN12 Is a Norrin Co-receptor that Amplifies Frizzled4 Ligand Selectivity and Signaling. Cell reports 79 28658627
1999 Overexpression of nm23-H2/NDP kinase B in a human oral squamous cell carcinoma cell line results in reduced metastasis, differentiated phenotype in the metastatic site, and growth factor-independent proliferative activity in culture. Clinical cancer research : an official journal of the American Association for Cancer Research 79 10632374
2005 Ectopic norrin induces growth of ocular capillaries and restores normal retinal angiogenesis in Norrie disease mutant mice. The Journal of neuroscience : the official journal of the Society for Neuroscience 75 15716406
2001 Sptrx-2, a fusion protein composed of one thioredoxin and three tandemly repeated NDP-kinase domains is expressed in human testis germ cells. Genes to cells : devoted to molecular & cellular mechanisms 75 11737268
2010 Norrin promotes vascular regrowth after oxygen-induced retinal vessel loss and suppresses retinopathy in mice. The Journal of neuroscience : the official journal of the Society for Neuroscience 73 20053900
1998 NM23-NDP kinase. The international journal of biochemistry & cell biology 73 9924799
1993 Expression of nm23/NDP kinase proteins on the cell surface. Oncogene 73 8386830
2021 Structures of active melanocortin-4 receptor-Gs-protein complexes with NDP-α-MSH and setmelanotide. Cell research 72 34561620
2012 Norrin: molecular and functional properties of an angiogenic and neuroprotective growth factor. Progress in retinal and eye research 70 22387751
1995 A human NDP-kinase B specifically binds single-stranded poly-pyrimidine sequences. Nucleic acids research 70 7479028
2019 Molecularly defined cortical astroglia subpopulation modulates neurons via secretion of Norrin. Nature neuroscience 69 30936556
2021 Catenin α 1 mutations cause familial exudative vitreoretinopathy by overactivating Norrin/β-catenin signaling. The Journal of clinical investigation 65 33497368
2013 Multi-functional norrin is a ligand for the LGR4 receptor. Journal of cell science 64 23444378
2006 Mutations in the NDP gene: contribution to Norrie disease, familial exudative vitreoretinopathy and retinopathy of prematurity. Clinical & experimental ophthalmology 63 16970763
1999 A novel human nucleoside diphosphate (NDP) kinase, Nm23-H6, localizes in mitochondria and affects cytokinesis. Journal of cellular biochemistry 63 10618642
2019 Hypoxia tolerance in the Norrin-deficient retina and the chronically hypoxic brain studied at single-cell resolution. Proceedings of the National Academy of Sciences of the United States of America 61 30988181
2017 Mutations in LRP5,FZD4, TSPAN12, NDP, ZNF408, or KIF11 Genes Account for 38.7% of Chinese Patients With Familial Exudative Vitreoretinopathy. Investigative ophthalmology & visual science 58 28494495
2010 Expression of the Norrie disease gene (Ndp) in developing and adult mouse eye, ear, and brain. Gene expression patterns : GEP 58 21055480
2021 A Norrin/Wnt surrogate antibody stimulates endothelial cell barrier function and rescues retinopathy. EMBO molecular medicine 56 34105895
1997 Norrie disease protein (norrin) forms disulfide-linked oligomers associated with the extracellular matrix. The Journal of biological chemistry 55 9407136
2012 Constitutive overexpression of Norrin activates Wnt/β-catenin and endothelin-2 signaling to protect photoreceptors from light damage. Neurobiology of disease 54 23009755
2003 Knockout mice as model systems for studying nm23/NDP kinase gene functions. Application to the nm23-M1 gene. Journal of bioenergetics and biomembranes 53 12848338
2000 Inhibition by protein kinase C of the K(NDP) subtype of vascular smooth muscle ATP-sensitive potassium channel. Circulation research 49 10903994
1996 The enzymatic activity of Drosophila AWD/NDP kinase is necessary but not sufficient for its biological function. Developmental biology 49 8806830
2003 Nm23/NDP kinases in human male germ cells: role in spermiogenesis and sperm motility? Experimental cell research 45 14499630
2018 Biophysical and functional characterization of Norrin signaling through Frizzled4. Proceedings of the National Academy of Sciences of the United States of America 44 30104375
2013 Effect of NDP-α-MSH on PPAR-γ and -β expression and anti-inflammatory cytokine release in rat astrocytes and microglia. PloS one 43 23468969
2020 Norrin restores blood-retinal barrier properties after vascular endothelial growth factor-induced permeability. The Journal of biological chemistry 41 32086377
2019 Extracellular Vesicles from Activated Dermal Fibroblasts Stimulate Hair Follicle Growth Through Dermal Papilla-Secreted Norrin. Stem cells (Dayton, Ohio) 40 31237401
2019 Familial Exudative Vitreoretinopathy-Related Disease-Causing Genes and Norrin/β-Catenin Signal Pathway: Structure, Function, and Mutation Spectrums. Journal of ophthalmology 40 31827910
1999 A novel NDP-6-deoxyhexosyl-4-ulose reductase in the pathway for the synthesis of thymidine diphosphate-D-fucose. The Journal of biological chemistry 39 10358040
2017 Norrin-induced Frizzled4 endocytosis and endo-lysosomal trafficking control retinal angiogenesis and barrier function. Nature communications 38 28675177
2008 The relationship between dNTP pool levels and mutagenesis in an Escherichia coli NDP kinase mutant. Proceedings of the National Academy of Sciences of the United States of America 38 18621712
2020 Activation of the Melanocortin-1 Receptor by NDP-MSH Attenuates Oxidative Stress and Neuronal Apoptosis through PI3K/Akt/Nrf2 Pathway after Intracerebral Hemorrhage in Mice. Oxidative medicine and cellular longevity 37 33274009
2019 Müller Cell-Localized G-Protein-Coupled Receptor 81 (Hydroxycarboxylic Acid Receptor 1) Regulates Inner Retinal Vasculature via Norrin/Wnt Pathways. The American journal of pathology 37 31220454
2012 Norrin stimulates cell proliferation in the superficial retinal vascular plexus and is pivotal for the recruitment of mural cells. Human molecular genetics 37 22394677
2005 Fetal loss in homozygous mutant Norrie disease mice: a new role of Norrin in reproduction. Genesis (New York, N.Y. : 2000) 37 16035034
2017 Mutation Spectrum of the LRP5, NDP, and TSPAN12 Genes in Chinese Patients With Familial Exudative Vitreoretinopathy. Investigative ophthalmology & visual science 34 29181528
2010 An essential role of the cysteine-rich domain of FZD4 in Norrin/Wnt signaling and familial exudative vitreoretinopathy. The Journal of biological chemistry 33 21177847
2004 Nm23-M2/NDP kinase B induces endogenous c-myc and nm23-M1/NDP kinase A overexpression in BAF3 cells. Both NDP kinases protect the cells from oxidative stress-induced death. Experimental cell research 32 15530864
2003 NDP gene mutations in 14 French families with Norrie disease. Human mutation 32 14635119
2014 The role of the hypoxia response in shaping retinal vascular development in the absence of Norrin/Frizzled4 signaling. Investigative ophthalmology & visual science 31 25414188
2007 Moderate reduction of Norrin signaling activity associated with the causative missense mutations identified in patients with familial exudative vitreoretinopathy. Human genetics 31 17955262
1992 Estrogen receptor, c-erbB-2 and nm23/NDP kinase expression in the intraductal and invasive components of human breast cancers. Japanese journal of cancer research : Gann 31 1356959
1994 Immunohistochemical analysis of nm23/NDP kinase expression in human lung adenocarcinoma: association with tumor progression in Clara cell type. Japanese journal of cancer research : Gann 30 7928630
2017 FZD4 Marks Lateral Plate Mesoderm and Signals with NORRIN to Increase Cardiomyocyte Induction from Pluripotent Stem Cell-Derived Cardiac Progenitors. Stem cell reports 28 29249665
2024 Glutamatergic neuronal activity regulates angiogenesis and blood-retinal barrier maturation via Norrin/β-catenin signaling. Neuron 27 38599212
2012 Protective action of NDP-MSH in experimental subarachnoid hemorrhage. Experimental neurology 27 22230666
2009 Double knockout Nme1/Nme2 mouse model suggests a critical role for NDP kinases in erythroid development. Molecular and cellular biochemistry 26 19381783
2013 Retinal vascular rescue of oxygen-induced retinopathy in mice by norrin. Investigative ophthalmology & visual science 25 23188723
2003 Receptor activation regulates cortical, but not vesicular localization of NDP kinase. Journal of cell science 24 12829743
2020 Norrin mediates tumor-promoting and -suppressive effects in glioblastoma via Notch and Wnt. The Journal of clinical investigation 22 32182224
2017 Characterization of a Novel Nicotine Degradation Gene Cluster ndp in Sphingomonas melonis TY and Its Evolutionary Analysis. Frontiers in microbiology 22 28337179
2014 A novel signaling pathway regulates colon cancer angiogenesis through Norrin. Scientific reports 22 25005225
2009 A novel NDP mutation in an infant with unilateral persistent fetal vasculature and retinal vasculopathy. Ophthalmic genetics 22 19373682
2003 Physiological and pathological relevance of extracellular NM23/NDP kinases. Journal of bioenergetics and biomembranes 22 12848346
2023 A Frizzled4-LRP5 agonist promotes blood-retina barrier function by inducing a Norrin-like transcriptional response. iScience 21 37559903
2021 Structure-function relationships in NDP-sugar active SDR enzymes: Fingerprints for functional annotation and enzyme engineering. Biotechnology advances 21 33571638
2010 Interactions of the melanocortin-4 receptor with the peptide agonist NDP-MSH. Journal of molecular biology 21 20600126
2006 Nm23/NDP kinases in hepatocellular carcinoma. Journal of bioenergetics and biomembranes 21 16944304
2004 Wnt signaling: Ig-norrin the dogma. Current biology : CB 21 15182694
2003 Structural analysis of the activation of ribavirin analogs by NDP kinase: comparison with other ribavirin targets. Molecular pharmacology 21 12606760
1996 Peripheral retinopathy in offspring of carriers of Norrie disease gene mutations. Possible transplacental effect of abnormal Norrin. Ophthalmology 20 9003348
2017 Norrin treatment improves ganglion cell survival in an oxygen-induced retinopathy model of retinal ischemia. Experimental eye research 19 28823941
2016 Mutation spectrum of the Norrie disease pseudoglioma (NDP) gene in Indian patients with FEVR. Molecular vision 19 27217716
2014 Protective effects of the melanocortin analog NDP-α-MSH in rats undergoing cardiac arrest. European journal of pharmacology 19 25446929
2009 The peptide NDP-MSH induces phenotype changes in the heart that resemble ischemic preconditioning. Peptides 19 19799952
2007 Regulation of norrin receptor frizzled-4 by Wnt2 in colon-derived cells. BMC cell biology 19 17386109
2020 Ethacrynic acid, a loop diuretic, suppresses epithelial-mesenchymal transition of A549 lung cancer cells via blocking of NDP-induced WNT signaling. Biochemical pharmacology 18 33189676
2015 Norrin mediates angiogenic properties via the induction of insulin-like growth factor-1. Experimental eye research 18 26706283
2009 Norrin attenuates protease-mediated death of transformed retinal ganglion cells. Molecular vision 18 19137075
2004 Norrin and frizzled; a new vein for the eye. Developmental cell 18 15068782
2003 ErbB2 and the antimetastatic nm23/NDP kinase in regulating serum induced breast cancer invasion. International journal of molecular medicine 18 12792823
2012 Melanocortin-1 receptor-mediated signalling pathways activated by NDP-MSH and HBD3 ligands. Pigment cell & melanoma research 17 22364200
2022 Spectrum of Mutations in NDP Resulting in Ocular Disease; a Systematic Review. Frontiers in genetics 16 35651932
2008 Vascular changes in the cerebellum of Norrin /Ndph knockout mice correlate with high expression of Norrin and Frizzled-4. The European journal of neuroscience 16 18547247
1997 Nm23/nucleoside diphosphate (NDP) kinase expression in human malignant melanomas: significance and implications in tumor biology. Anticancer research 16 9066703
2021 NDP-MSH treatment recovers marginal lungs during ex vivo lung perfusion (EVLP). Peptides 15 33865932
2019 NDP-MSH reduces oxidative damage induced by palmitic acid in primary astrocytes. Journal of neuroendocrinology 15 30712280
2015 NDP-α-MSH attenuates heart and liver responses to myocardial reperfusion via the vagus nerve and JAK/ERK/STAT signaling. European journal of pharmacology 15 26477637
2024 Familial Exudative Vitreoretinopathy With and Without Pathogenic Variants of Norrin/β-Catenin Signaling Genes. Ophthalmology science 14 38881609

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