Affinage

NPHP4

Nephrocystin-4 · UniProt O75161

Length
1426 aa
Mass
157.6 kDa
Annotated
2026-06-10
25 papers in source corpus 12 papers cited in narrative 12 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

NPHP4 (nephrocystin-4) is a transition zone protein that builds and gates the cilium, controlling the selective composition of ciliary membrane and matrix proteins and supporting ciliary signaling across photoreceptors, motile cilia, and sensory cilia (PMID:25150219, PMID:21078623). At the distal transition zone it functions as a diffusion barrier that retains ciliary membrane proteins while excluding large soluble housekeeping proteins from the flagellar compartment (PMID:25150219). NPHP4 is required for photoreceptor outer segment formation and for male germ cell homeostasis, with loss causing outer-segment marker mislocalization, synaptic ribbon degeneration, and sperm motility defects (PMID:21078623, PMID:41782365); its targeting to photoreceptor cilia depends on RPGRIP1 (PMID:22825473). In multiciliated cells NPHP4 organizes the subapical actin network required for ciliary polarization and directional fluid flow by nucleating an Inturned–DAAM1 complex and recruiting Inturned to basal bodies (PMID:26644512), and it is required for motile-cilia-driven left-right patterning (PMID:22550138). Separately, NPHP4 acts as a negative regulator of Hippo signaling: it binds the kinase LATS1 and inhibits LATS1-mediated phosphorylation of YAP and TAZ, freeing them from 14-3-3 for nuclear TEAD-dependent transcription and promoting proliferation (PMID:21555462). Genetically, NPHP4 operates in a pathway parallel to MKS-complex genes and synergizes with the BBSome component BBS5 and the ciliary kinesin OSM-3 in cilia assembly and signaling (PMID:20150540, PMID:26863025, PMID:34850872).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2005 Medium

    Established that NPHP4 localizes to ciliated sensory endings and acts redundantly with NPHP1 in ciliary sensory signaling, defining its baseline role at the cilium rather than in general cytoplasm.

    Evidence GFP localization and genetic epistasis of single vs. nphp-1; nphp-4 double mutants in C. elegans

    PMID:15817158

    Open questions at the time
    • Did not define the molecular barrier function
    • Redundancy mechanism with NPHP1 not resolved at protein level
  2. 2008 Low

    Mapped domain-specific requirements by showing a truncation retaining the NPHP1-binding domain but lacking the RPGRIP1-interacting domain causes cone-rod dystrophy without kidney disease, separating retinal and renal functional modules.

    Evidence RT-PCR exon-skipping analysis and pedigree segregation of a natural canine NPHP4 deletion

    PMID:18687878

    Open questions at the time
    • Domain assignments inferred from deletion breakpoints, not direct mutagenesis
    • No biochemical confirmation of lost RPGRIP1 binding
  3. 2010 Medium

    Demonstrated NPHP4 is essential for photoreceptor outer segment formation and male fertility in mammals, connecting transition-zone localization to tissue-level ciliary phenotypes.

    Evidence Localization, ERG, EM and sperm analysis in the Nphp4-nmf192 mouse mutant

    PMID:21078623

    Open questions at the time
    • Mechanism of outer-segment marker mislocalization not defined
    • No structural defect in connecting cilia explained
  4. 2011 High

    Uncovered a non-ciliary signaling role by showing NPHP4 binds LATS1 and inhibits YAP/TAZ phosphorylation, positioning it as a negative regulator of Hippo signaling and driver of proliferation.

    Evidence Reciprocal Co-IP, in vitro phosphorylation, nuclear translocation, TEAD reporter and proliferation assays

    PMID:21555462

    Open questions at the time
    • Link between ciliary and Hippo-regulatory roles unresolved
    • No structural basis for LATS1 inhibition
  5. 2012 Medium

    Identified RPGRIP1 as the ciliary-targeting factor for NPHP4 in photoreceptors, explaining cell-type-specific localization (retina vs. kidney).

    Evidence Immunofluorescence and subcellular fractionation in Rpgrip1-nmf247 mouse retina and kidney

    PMID:22825473

    Open questions at the time
    • Targeting mechanism in non-retinal tissues not identified
    • Direct NPHP4–RPGRIP1 binding not biochemically resolved here
  6. 2012 Medium

    Showed NPHP4 is required for motile-cilia function and left-right axis determination, with patient mutations failing to rescue, validating disease-relevant alleles.

    Evidence Morpholino knockdown in zebrafish Kupffer's vesicle with human wild-type vs. mutant mRNA rescue

    PMID:22550138

    Open questions at the time
    • Molecular mechanism within motile cilia not defined
    • Morpholino specificity limitations
  7. 2014 High

    Defined the core molecular function: NPHP4 forms a distal transition-zone barrier gating both membrane protein composition and exclusion of large soluble proteins from cilia.

    Evidence Biochemical fractionation of flagella from nphp4-null vs. wild-type Chlamydomonas with localization and ultrastructure

    PMID:25150219

    Open questions at the time
    • Structural organization of the barrier not resolved
    • Partner proteins constituting the barrier not fully enumerated
  8. 2015 High

    Extended NPHP4 function beyond gating to actin cytoskeleton organization by showing it nucleates an Inturned–DAAM1 complex required for subapical actin and ciliary polarization.

    Evidence Co-IP and morpholino knockdown in Xenopus multiciliated cells with actin/basal body imaging and fluid-flow assays

    PMID:26644512

    Open questions at the time
    • Whether actin role is separable from gating role unknown
    • Direct DAAM1 binding partner geometry not resolved
  9. 2016 Medium

    Linked NPHP4 to intraflagellar transport by showing it influences distal kinesin OSM-3 cilia entry rate, connecting the barrier to IFT-dependent ciliary maintenance.

    Evidence Genetic screen, FRAP, IFT velocity, and behavioral assays in C. elegans nphp-4 and OSM-3 mutants

    PMID:26863025

    Open questions at the time
    • Direct NPHP4–OSM-3 interaction not demonstrated
    • Mechanism of reduced OSM-3 entry unresolved
  10. 2022 Medium

    Established an evolutionarily conserved genetic interaction with the BBSome component BBS5, indicating synergistic control of ciliary signaling across species.

    Evidence Double mutant analysis in C. elegans, zebrafish and mouse plus conditional Bbs5 allele with viability scoring

    PMID:34850872

    Open questions at the time
    • Molecular basis of NPHP4–BBSome synergy unknown
    • No physical interaction demonstrated
  11. 2026 Medium

    Refined the male-fertility role by localizing nphp4 to Sertoli cells and showing it maintains the spermatogonial niche, with loss causing Sertoli apoptosis and germ cell depletion.

    Evidence In situ hybridization, CRISPR/Cas9 knockout, EM and transcriptomics in medaka

    PMID:41782365

    Open questions at the time
    • Whether the niche role is ciliary or signaling-based unresolved
    • Mitochondrial damage mechanism undefined

Open questions

Synthesis pass · forward-looking unresolved questions
  • How NPHP4's ciliary gating, actin-organizing, and Hippo-regulatory activities are mechanistically integrated within a single protein remains unresolved.
  • No structural model of NPHP4 barrier assembly
  • Connection between cilium-based and Hippo-signaling roles unestablished
  • Substrate/recruitment hierarchy at the transition zone undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 2 GO:0008092 cytoskeletal protein binding 1 GO:0098772 molecular function regulator activity 1
Localization
GO:0005929 cilium 2 GO:0005815 microtubule organizing center 1
Pathway
R-HSA-1852241 Organelle biogenesis and maintenance 2 R-HSA-162582 Signal Transduction 1
Partners
DAAM1INTURNEDLATS1NPHP1RPGRIP1
Complex memberships
NPHP4-Inturned-DAAM1 complexciliary transition zone

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 NPHP4 directly interacts with the kinase LATS1 and inhibits LATS1-mediated phosphorylation of YAP and TAZ, leading to their release from 14-3-3 binding and nuclear translocation, thereby promoting TEAD/TAZ/YAP-dependent transcriptional activity. NPHP4 thus acts as a negative regulator of mammalian Hippo signaling and promotes cell proliferation through this mechanism. Co-immunoprecipitation, phosphorylation assays, nuclear translocation assays, knockdown with TEAD/TAZ reporter assays, proliferation assays The Journal of cell biology High 21555462
2014 NPHP4 is stably incorporated into the distal part of the flagellar transition zone (close to the membrane, distal to CEP290) in Chlamydomonas reinhardtii, and functions as an essential component of a barrier that regulates both membrane protein composition and exclusion of large soluble proteins (>50 kDa) from flagella. Loss of NPHP4 results in reduced membrane proteins and entry of cellular housekeeping proteins into flagella. Biochemical fractionation of isolated flagella from nphp4-null vs. wild-type Chlamydomonas, immunofluorescence localization, ultrastructural analysis Journal of cell science High 25150219
2015 NPHP4 interacts with the polarity protein Inturned (via co-immunoprecipitation), and Inturned mediates formation of a ternary complex between NPHP4 and the actin nucleator DAAM1. NPHP4 depletion in Xenopus multiciliated cells disrupts the subapical actin layer required for cilia polarization and directional fluid flow. NPHP4 depletion also prevents association of Inturned with basal bodies. Co-immunoprecipitation, morpholino knockdown in Xenopus laevis epidermis, immunofluorescence imaging of subapical actin and basal bodies, ciliary beat and fluid flow assays The Journal of cell biology High 26644512
2010 NPHP4 localizes to the transition zone of the connecting cilia in photoreceptors. Loss of NPHP4 (nonsense mutation in Nphp4) causes failure of photoreceptor outer segment formation with mislocalization of outer segment markers to inner segments and outer nuclear layer, rapid synaptic ribbon degeneration, and male infertility with reduced sperm motility, without structural defects in connecting cilia. Immunofluorescence localization, ERG recording, electron microscopy of photoreceptor structure, sperm motility/count analysis in Nphp4-nmf192 mouse mutant Human molecular genetics Medium 21078623
2012 RPGRIP1 is required for the ciliary targeting of NPHP4 (and RPGR, SDCCAG8) specifically in photoreceptors: loss of RPGRIP1 expression in Rpgrip1(nmf247) mice abolishes NPHP4 and RPGR from photoreceptor cilia and shifts NPHP4 and SDCCAG8 to an ER-associated membrane fraction, while ciliary localization of these proteins is unaffected in kidney cells of the same mutant. Immunofluorescence and subcellular fractionation in Rpgrip1(nmf247) mouse retina and kidney, immunolocalization of NPHP4 relative to centrin-2 and acetylated-α-tubulin Cell death & disease Medium 22825473
2012 Knockdown of nphp4 in zebrafish disrupts formation and function of motile cilia in Kupffer's vesicle, impairing asymmetric fluid flow and left-right patterning. This L-R axis defect was partially rescued by wild-type human NPHP4 mRNA but not by patient-derived mutant NPHP4. Antisense morpholino knockdown in zebrafish, analysis of Kupffer's vesicle cilia, heart and gut laterality assays, rescue experiments with wild-type and mutant human NPHP4 mRNA Circulation research Medium 22550138
2005 C. elegans NPHP-1 and NPHP-4 proteins co-localize to ciliated sensory endings and to male-specific sensory cilia. Single nphp-1 or nphp-4 mutants have intact cilia, but nphp-1; nphp-4 double mutants show male mating response defects, indicating redundant roles in ciliary sensory signal transduction. GFP fusion protein localization, behavioral assays in single and double nphp-1; nphp-4 C. elegans mutants, genetic epistasis Experimental cell research Medium 15817158
2010 In C. elegans, mks-1 and mks-3 genetically interact with a pathway involving nphp-1 and nphp-4 to influence proper positioning, orientation, and formation of cilia. Combined disruption of nphp and mks pathways has cell non-autonomous effects on C. elegans sensilla, demonstrating that nphp-4 functions in a pathway parallel to the MKS complex genes. Genetic epistasis analysis in C. elegans double and triple mutants, ciliogenesis and chemoreception assays, fluorescence imaging of MKS-3 localization Journal of the American Society of Nephrology Medium 20150540
2016 NPHP-4 in C. elegans influences the localization and function of the distal ciliary kinesin OSM-3: an OSM-3(S316F) phosphorylation-site mutation causes reduced IFT velocity and exacerbates nphp-4 ciliary defects (distal segment loss, dye-filling, osmotic avoidance defects) without affecting wild-type animals. FRAP analysis revealed that nphp-4 mutant background decreases OSM-3 cilia entry rate. Genetic screen, double mutant analysis, FRAP, GFP-tagged IFT velocity measurement, dye-filling and osmotic avoidance behavioral assays in C. elegans PLoS genetics Medium 26863025
2022 Genetic interaction between nphp-4 and bbs-5 is evolutionarily conserved: nphp-4; bbs-5 double mutants in C. elegans exhibit phenotypes not seen in either single mutant; in mice, Nphp4; Bbs5 double mutants show reduced viability (fewer than expected with three mutant alleles), and postnatal conditional loss of Bbs5 compromised survival when combined with Nphp4 allele, indicating synergistic disruption of ciliary signaling. Mutagenesis screen in C. elegans, double mutant analysis in C. elegans/zebrafish/mouse, conditional allele in mouse, viability/phenotype scoring Genetics Medium 34850872
2008 A 180-bp deletion in exon/intron 5 of canine NPHP4 causes exon skipping and a truncated protein that retains the NPHP1-binding domain but lacks the RPGRIP1-interacting domain, leading to cone-rod dystrophy without kidney disease. This establishes domain-specific functional requirements: the RPGRIP1-interacting domain is necessary for retinal function. RT-PCR demonstrating exon skipping, protein domain analysis, segregation analysis in wire-haired dachshund pedigrees Genome research Low 18687878
2026 In medaka (Oryzias latipes), nphp4 is expressed in Sertoli cells of the spermatogonial niche. CRISPR/Cas9-mediated nphp4 deficiency causes age-dependent infertility with sperm motility defects, head abnormalities, mitochondrial damage, Sertoli cell apoptosis, and altered Sertoli cell functional markers leading to premature germ cell depletion—identifying nphp4 as a regulator of testicular niche homeostasis. In situ hybridization for localization, CRISPR/Cas9 knockout, sperm motility and morphology analysis, transmission electron microscopy, transcriptomic profiling Reproduction (Cambridge, England) Medium 41782365

Source papers

Stage 0 corpus · 25 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 NPHP4, a cilia-associated protein, negatively regulates the Hippo pathway. The Journal of cell biology 129 21555462
2014 NPHP4 controls ciliary trafficking of membrane proteins and large soluble proteins at the transition zone. Journal of cell science 78 25150219
2010 NPHP4 is necessary for normal photoreceptor ribbon synapse maintenance and outer segment formation, and for sperm development. Human molecular genetics 75 21078623
2008 A deletion in nephronophthisis 4 (NPHP4) is associated with recessive cone-rod dystrophy in standard wire-haired dachshund. Genome research 71 18687878
2010 Normal ciliogenesis requires synergy between the cystic kidney disease genes MKS-3 and NPHP-4. Journal of the American Society of Nephrology : JASN 53 20150540
2015 The polarity protein Inturned links NPHP4 to Daam1 to control the subapical actin network in multiciliated cells. The Journal of cell biology 49 26644512
2005 Functional characterization of the C. elegans nephrocystins NPHP-1 and NPHP-4 and their role in cilia and male sensory behaviors. Experimental cell research 45 15817158
2005 Mutational analysis of the NPHP4 gene in 250 patients with nephronophthisis. Human mutation 44 15776426
2012 Selective loss of RPGRIP1-dependent ciliary targeting of NPHP4, RPGR and SDCCAG8 underlies the degeneration of photoreceptor neurons. Cell death & disease 42 22825473
2012 NPHP4 variants are associated with pleiotropic heart malformations. Circulation research 39 22550138
2013 NPHP4 mutation is linked to cerebello-oculo-renal syndrome and male infertility. Clinical genetics 19 23574405
2016 A Screen for Modifiers of Cilia Phenotypes Reveals Novel MKS Alleles and Uncovers a Specific Genetic Interaction between osm-3 and nphp-4. PLoS genetics 17 26863025
2007 Novel mutations in NPHP4 in a consanguineous family with histological findings of focal segmental glomerulosclerosis. American journal of kidney diseases : the official journal of the National Kidney Foundation 17 17954299
2022 Evolutionarily conserved genetic interactions between nphp-4 and bbs-5 mutations exacerbate ciliopathy phenotypes. Genetics 13 34850872
2019 Adult-Diagnosed Nonsyndromic Nephronophthisis in Australian Families Caused by Biallelic NPHP4 Variants. American journal of kidney diseases : the official journal of the National Kidney Foundation 12 31810733
2004 Clinical and histological presentation of 3 siblings with mutations in the NPHP4 gene. American journal of kidney diseases : the official journal of the National Kidney Foundation 9 14750102
2010 The novel and independent association between single-point SNP of NPHP4 gene and renal function in non-diabetic Japanese population: the Takahata study. Journal of human genetics 8 20844548
2011 Assessing the pathogenic potential of human Nephronophthisis disease-associated NPHP-4 missense mutations in C. elegans. Human molecular genetics 7 21546380
2023 A novel NPHP4 homozygous missense variant identified in infertile brothers with multiple morphological abnormalities of the sperm flagella. Journal of assisted reproduction and genetics 6 37831349
2005 Effect of splice-site polymorphisms of the TMPRSS4, NPHP4 and ORCTL4 genes on their mRNA expression. Journal of genetics 6 16131712
2014 Diverse phenotypic expression of NPHP4 mutations in four siblings. The Turkish journal of pediatrics 3 25818963
2024 Identification of a Novel Deletion Variant (c.2999_3005delTGTGTGT/p.Asn1000SerfsTer4) in NPHP4 Associated With Nephronophthisis-4. Journal of clinical laboratory analysis 2 38895833
2022 One novel ACOT7-NPHP4 fusion gene identified in one patient with acute lymphoblastic leukemia: a case report. BMC medical genomics 2 36316773
2026 nphp4 deficiency disrupts testicular homeostasis and impairs male fertility in medaka (Oryzias latipes). Reproduction (Cambridge, England) 0 41782365
2025 Molecular Spectrum and Deep Phenotyping of a Turkish Joubert Syndrome Cohort, Including a Potential Candidate Gene, NPHP4. Turkish archives of pediatrics 0 42044428

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