Affinage

WHRN

Whirlin · UniProt Q9P202

Length
907 aa
Mass
96.6 kDa
Annotated
2026-06-11
16 papers in source corpus 9 papers cited in narrative 9 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 4/5 claims corpus-supported (80%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

Whirlin (WHRN) is a multi-PDZ scaffold protein that organizes submembranous molecular complexes in cochlear, vestibular, and photoreceptor sensory cells, where it drives coordinated actin polymerization and membrane growth required for stereocilia elongation and maintenance (PMID:12833159, PMID:26420843). WHRN is expressed as distinct isoforms with separable roles: full-length whirlin anchors the Usher type 2 protein complex—including USH2A and VLGR1b/ADGRV1—at stereociliary bases and photoreceptor synaptic regions, while both full-length and C-terminal isoforms act at stereociliary tips to promote elongation; isoform-specific disruptions accordingly produce either a combined retinal-plus-hearing (USH2D) or hearing-only (DFNB31) phenotype (PMID:16434480, PMID:26307081). The whirlin-organized complex is dynamically regulated: ADGRV1 suppresses WHRN phosphorylation through regional cAMP-PKA signaling, and the phosphorylation state of WHRN controls USH2A stability by governing recruitment of the E3 ligase WDSUB1, which ubiquitinates and destabilizes USH2A (PMID:37066759). WHRN also engages CIB2 through a CIB2 EF2–whirlin HHD2 domain interaction, though CIB2 contributes functions in stereocilia staircase patterning independent of whirlin [PMID:bio_10.1101_2024.07.30.605852], and binds the MAGUK scaffold CASK in neurons, where the two co-localize along dendritic processes (PMID:12641734). The developmental requirement for whirlin is irreversible: late re-expression after hearing-loss onset fails to rescue auditory thresholds or stereocilia morphology (PMID:42214993).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2003 High

    Established WHRN as a causal organizer of stereocilia: it was unknown what molecule coordinated actin-based stereocilia elongation, and transgene correction of the whirler mouse showed whirlin loss directly causes defective elongation.

    Evidence BAC transgene rescue of the whirler mutant with mutation analysis and immunolocalization in cochlear hair cells

    PMID:12833159

    Open questions at the time
    • Molecular partners within the submembranous complex not yet identified
    • Mechanism linking the PDZ scaffold to actin machinery not defined
  2. 2003 Medium

    Identified a neuronal binding partner: whether whirlin acted outside hair cells was unknown, and direct interaction with the MAGUK scaffold CASK placed it in synaptic scaffolding complexes in the CNS.

    Evidence Co-immunoprecipitation, immunocytochemistry, electron microscopy, and in situ hybridization in neurons

    PMID:12641734

    Open questions at the time
    • No functional mutagenesis of the CASK interaction
    • Functional consequence of WHRN-CASK scaffolding in neurons untested
  3. 2006 Medium

    Placed whirlin in the Usher protein interactome: it was unclear how Usher syndrome proteins were physically organized, and whirlin was shown to directly associate with USH2A isoform b and VLGR1b at photoreceptor and hair cell sites.

    Evidence Direct binding assays and co-localization by immunofluorescence with isoform expression analysis

    PMID:16434480

    Open questions at the time
    • Single lab; binding affinities and domain mapping not resolved
    • Functional requirement of these interactions in vivo not tested here
  4. 2015 High

    Resolved isoform-specific function: it was unknown why WHRN mutations give either combined deaf-blindness or isolated deafness, and an allelic series showed full-length whirlin serves the USH2 complex/retina while both isoforms drive stereociliary tip elongation.

    Evidence Isoform-specific Dfnb31 mutant mouse allelic series with auditory and retinal phenotyping and immunofluorescence

    PMID:26307081

    Open questions at the time
    • Mechanism by which the N-terminal fragment retains partial retinal function unclear
    • How isoform localization is differentially targeted not defined
  5. 2015 Medium

    Extended the requirement to the vestibular system: whether whirlin was needed beyond auditory hair cells was untested, and isoform loss was shown to cause severe vestibular stereociliary growth and functional deficits.

    Evidence Isoform-specific immunofluorescence, vestibular sensory-evoked potentials, and behavioral balance tests in Dfnb31 mutant mice

    PMID:26420843

    Open questions at the time
    • Single lab
    • Molecular partners of whirlin specific to vestibular hair cells not identified
  6. 2023 High

    Defined the dynamic regulatory axis: how the ankle-link complex is maintained was unknown, and ADGRV1 was shown to suppress WHRN phosphorylation via cAMP-PKA, with phospho-WHRN recruiting the E3 ligase WDSUB1 to control USH2A ubiquitination and stability.

    Evidence Adgrv1 mutant mouse, yeast two-hybrid, FlAsH-BRET, NMR, mutagenesis, and ubiquitination assays

    PMID:37066759

    Open questions at the time
    • Kinase/phosphatase acting directly on WHRN not fully resolved
    • Generality of the WDSUB1 mechanism across tissues untested
  7. 2024 Medium

    Mapped the WHRN-CIB2 interaction and tested its functional dependence: it was unknown whether CIB2 acts through whirlin, and domain mapping plus genetic epistasis showed a CIB2 EF2–whirlin HHD2 interaction but CIB2 functions independently in staircase patterning.

    Evidence NanoSPD pulldown with deletion constructs, AlphaFold2 multimer modeling, double-mutant mouse genetics, overexpression rescue, and SEM (preprint)

    PMID:bio_10.1101_2024.07.30.605852

    Open questions at the time
    • Preprint, single lab
    • Functional role of the WHRN-CIB2 binding event itself not defined
    • Structural interaction validated only computationally
  8. 2025 Medium

    Demonstrated dosage sensitivity: whether partial WHRN loss matters was unknown, and heterozygous loss of the long isoform was shown to cause progressive, sex-dependent sensorineural hearing loss with hair cell death.

    Evidence Longitudinal ABR measurements in a large Whrn+/- cohort with immunohistochemistry for hair cell death

    PMID:40360853

    Open questions at the time
    • Mechanism of sex-dependent susceptibility unexplained
    • Single lab/single mouse background
  9. 2026 Medium

    Established the developmental, irreversible nature of the requirement: it was unknown whether restoring WHRN could reverse damage, and inducible late re-expression failed to rescue thresholds or stereocilia morphology.

    Evidence Tamoxifen-inducible Flp-mediated genetic rescue in Whrntm1a/tm1a mice with ABR and SEM

    PMID:42214993

    Open questions at the time
    • Temporal window for productive re-expression not finely mapped
    • Whether earlier reactivation could rescue not tested

Open questions

Synthesis pass · forward-looking unresolved questions
  • How WHRN mechanically couples its PDZ/HHD scaffolding to the actin polymerization machinery that elongates stereocilia, and how its phosphorylation is enzymatically controlled, remain open.
  • No direct link between WHRN scaffolding and actin-elongation enzymes characterized
  • Kinase/phosphatase directly modifying WHRN not identified

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 4
Localization
GO:0005856 cytoskeleton 2 GO:0005929 cilium 1
Pathway
R-HSA-9709957 Sensory Perception 3 R-HSA-1266738 Developmental Biology 2
Partners
ADGRV1CASKCIB2USH2AWDSUB1
Complex memberships
USH2 protein complex (ankle-link complex)

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2003 Whirlin (WHRN) is a novel PDZ domain-containing protein essential for elongation and maintenance of stereocilia in inner and outer hair cells of the cochlea; BAC-mediated transgene correction of the whirler mouse phenotype established that loss of whirlin causes defective stereocilia elongation, and whirlin acts as an organizer of submembranous molecular complexes controlling coordinated actin polymerization and membrane growth of stereocilia. BAC transgene rescue of whirler mouse mutant, mutation analysis, immunolocalization in cochlear hair cell stereocilia Nature genetics High 12833159
2003 CIP98 (WHRN) is expressed in the central nervous system and directly interacts with CASK (calmodulin-dependent serine kinase), a MAGUK family scaffolding protein; CIP98 co-localizes with CASK along dendritic processes of neurons, suggesting a role in CASK scaffolding complex formation at synapses. Co-immunoprecipitation, immunocytochemistry, electron microscopy, in situ hybridization Journal of neurochemistry Medium 12641734
2006 Whirlin directly associates with USH2A isoform b and VLGR1b (two Usher syndrome proteins), and co-localizes with them at synaptic regions of photoreceptor cells and outer hair cells, at the connecting cilium and outer limiting membrane of photoreceptors, and in spiral ganglion neurons, placing whirlin within the Usher protein interactome as a PDZ scaffold. Direct binding assays (pulldown/yeast two-hybrid implied), co-localization by immunofluorescence, expression analysis of isoforms Human molecular genetics Medium 16434480
2015 Distinct whirlin isoforms play different roles: full-length (FL-) whirlin in photoreceptors and hair cell stereociliary bases is required for the USH type 2 protein complex (important for retinal function), while FL- and C-terminal (C-) whirlins at hair cell stereociliary tips participate in stereociliary elongation. Mutations disrupting only FL-whirlin cause retinal degeneration plus moderate-severe hearing loss (USH2D phenotype), whereas mutations eliminating all isoforms but generating a truncated N-terminal fragment (partially functional in retina) cause profound hearing loss without retinal degeneration (DFNB31 phenotype). Isoform-specific mouse mutant analysis (Dfnb31 allelic series), immunofluorescence localization, auditory/retinal phenotyping of mutant mice Human molecular genetics High 26307081
2015 Both FL- and C-terminal whirlin isoforms are expressed in vestibular hair cells and are required for normal vestibular stereociliary growth; loss of whirlin isoforms in Dfnb31 mutant mice causes severe-to-profound vestibular deficits as measured by vestibular sensory-evoked potentials and behavioral balance tests. Isoform-specific immunofluorescence in vestibular organs, vestibular sensory-evoked potentials, behavioral tests (swimming, rotarod) in Dfnb31 mutant mice Human molecular genetics Medium 26420843
2023 ADGRV1 inhibits WHRN phosphorylation through regional cAMP-PKA signaling; phosphorylation state of WHRN in turn regulates the ubiquitination and stability of USH2A via the E3 ligase WDSUB1, which was identified by yeast two-hybrid screening as a WHRN-binding partner. A deafness-associated ADGRV1 mutation (Y6236fsX1) disrupts this signaling axis, leading to USH2A destabilization and stereocilia disorganization. NMR spectrometry, FlAsH-BRET, and mutagenesis defined the interaction motifs at single-residue resolution. Adgrv1 mutant mouse model, yeast two-hybrid screening, FlAsH-BRET assay, NMR spectrometry, mutagenesis, ubiquitination assays, cAMP-PKA signaling analysis Advanced science (Weinheim, Baden-Wurttemberg, Germany) High 37066759
2024 CIB2 directly binds whirlin through an interaction between the CIB2 EF2 domain and the whirlin HHD2 domain, as defined by deletion construct nanoscale pulldown (NanoSPD) assays and validated by AlphaFold2 multimer structural modeling. Genetic epistasis in double-homozygous Cib2KO/KO;Whrnwi/wi mice showed that the stereocilia phenotype is predominantly that of single Whrnwi/wi mutants, and overexpression of Whrn in Cib2KO/KO mice did not rescue stereocilia morphology, indicating CIB2 has independent functions from whirlin in stereocilia staircase patterning. NanoSPD pulldown with deletion constructs, AlphaFold2 multimer structural modeling, double-homozygous and double-heterozygous mouse genetics, overexpression rescue experiment, scanning electron microscopy bioRxivpreprint Medium bio_10.1101_2024.07.30.605852
2026 Activation of the Whrn gene after onset of hearing loss (at postnatal day 4 or 14) using tamoxifen-inducible Flp recombinase-mediated cassette removal did not rescue auditory brainstem response thresholds or reverse outer hair cell stereocilia defects in Whrntm1a/tm1a mice, demonstrating that stereocilia disorganization caused by Whrn loss is not reversed by late Whrn re-expression, indicating the requirement for whirlin is developmental and irreversible. Tamoxifen-inducible Flp recombinase genetic rescue experiment in mice, ABR threshold measurements, scanning electron microscopy of stereocilia Hearing research Medium 42214993
2025 Haploinsufficiency of Whrn (heterozygous loss of the long isoform) contributes to progressive sensorineural hearing loss in C57BL/6 mice, with sex-dependent effects: Whrn+/- males show progressive hearing loss with age while Whrn+/- females show elevated thresholds as early as 1-2 months, accompanied by hair cell death. Longitudinal ABR measurements in Whrn+/- heterozygous mice (n=135 mutant, 133 WT), immunohistochemistry for hair cell death Journal of the Association for Research in Otolaryngology : JARO Medium 40360853

Source papers

Stage 0 corpus · 16 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2003 Defects in whirlin, a PDZ domain molecule involved in stereocilia elongation, cause deafness in the whirler mouse and families with DFNB31. Nature genetics 261 12833159
2006 The DFNB31 gene product whirlin connects to the Usher protein network in the cochlea and retina by direct association with USH2A and VLGR1. Human molecular genetics 157 16434480
2015 Distinct expression and function of whirlin isoforms in the inner ear and retina: an insight into pathogenesis of USH2D and DFNB31. Human molecular genetics 35 26307081
2005 Identification of a novel frameshift mutation in the DFNB31/WHRN gene in a Tunisian consanguineous family with hereditary non-syndromic recessive hearing loss. Human mutation 34 15841483
2003 CIP98, a novel PDZ domain protein, is expressed in the central nervous system and interacts with calmodulin-dependent serine kinase. Journal of neurochemistry 30 12641734
2002 DFNB31, a recessive form of sensorineural hearing loss, maps to chromosome 9q32-34. European journal of human genetics : EJHG 29 11973626
2015 A study of whirlin isoforms in the mouse vestibular system suggests potential vestibular dysfunction in DFNB31-deficient patients. Human molecular genetics 19 26420843
2011 A novel DFNB31 mutation associated with Usher type 2 syndrome showing variable degrees of auditory loss in a consanguineous Portuguese family. Molecular vision 18 21738389
2013 The contribution of GPR98 and DFNB31 genes to a Spanish Usher syndrome type 2 cohort. Molecular vision 15 23441107
2023 Deafness-Associated ADGRV1 Mutation Impairs USH2A Stability through Improper Phosphorylation of WHRN and WDSUB1 Recruitment. Advanced science (Weinheim, Baden-Wurttemberg, Germany) 14 37066759
2010 Sequence variants of the DFNB31 gene among Usher syndrome patients of diverse origin. Molecular vision 14 20352026
2025 Computational study of the potential impact of WHRN protein missense SNPs on WHRN-MYO15A protein complex interaction and their association with Usher syndrome. Journal of biomolecular structure & dynamics 2 40389825
2017 Common founder effects of hereditary hemochromatosis, Wilson´s disease, the long QT syndrome and autosomal recessive deafness caused by two novel mutations in the WHRN and TMC1 genes. Hereditas 2 29270100
2023 Novel pathogenic WHRN variant causing hearing loss in a moroccan family. Molecular biology reports 1 37924449
2026 Hearing loss in a whirlin mouse mutant is not reversed by activating the Whrn gene. Hearing research 0 42214993
2025 Haploinsufficiency of Whrn Contributes to Progressive Sensorineural Hearing Loss in C57BL6 Mice. Journal of the Association for Research in Otolaryngology : JARO 0 40360853

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