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PDZD7

PDZ domain-containing protein 7 · UniProt Q9H5P4

Length
1033 aa
Mass
111.8 kDa
Annotated
2026-04-29
24 papers in source corpus 13 papers cited in narrative 13 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PDZD7 is a multi-PDZ-domain scaffolding protein essential for organizing the Usher type 2 (USH2) protein complex at the ankle-link region of inner ear hair cell stereocilia. Its long isoform localizes to stereocilia ankle links in a MYO7A-dependent manner, where its N-terminal PDZ1–PDZ2 supramodule preferentially binds ADGRV1/GPR98 while its PDZ3 domain engages FCHSD2 to link the complex to actin cytoskeletal dynamics, and its harmonin homology domain (HHD) mediates plasma membrane targeting through lipid binding (PMID:23055499, PMID:25406310, PMID:35695292, PMID:33937240). Loss of PDZD7 in mice causes congenital deafness with disorganized stereocilia bundles, loss of USH2A/GPR98/WHRN localization at ankle links, and reduced mechanotransduction currents, and homozygous PDZD7 disruption in humans causes non-syndromic congenital hearing loss (PMID:24334608, PMID:19028668). In the retina, PDZD7 acts as a genetic modifier of the USH2 pathway by regulating GPR98 localization at photoreceptor connecting cilia and contributing to digenic Usher syndrome in combination with USH2A or GPR98 mutations (PMID:20440071).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2008 Medium

    Establishing that PDZD7 is a deafness gene: a homozygous chromosomal translocation disrupting PDZD7 was identified as the cause of congenital hearing loss in a human case, and interaction assays placed it within the Usher protein network, revealing it as a harmonin/whirlin paralog with a role in auditory function.

    Evidence FISH and junction sequencing of human translocation; protein-protein interaction assays; RT-PCR for inner ear expression

    PMID:19028668

    Open questions at the time
    • Single family study without independent replication at that time
    • No localization in hair cells demonstrated
    • Mechanism of hearing loss not established
  2. 2010 High

    Demonstrating that PDZD7 functions as a modifier of retinal degeneration in the USH2 pathway: zebrafish knockdown showed PDZD7 loss reduces GPR98 localization at photoreceptor connecting cilia and synergizes with USH2A or GPR98 loss to exacerbate retinal cell death, establishing oligogenic disease contribution.

    Evidence Zebrafish morpholino knockdown with single and double knockdowns; immunolocalization of Gpr98

    PMID:20440071

    Open questions at the time
    • Retinal modifier role not confirmed in mammalian models
    • Direct biochemical interaction between PDZD7 and GPR98 not yet shown
    • Mechanism of retinal localization control unknown
  3. 2012 High

    Defining PDZD7 as a physical scaffolding component of the ankle-link complex: mass spectrometry identified PDZD7 in stereocilia, immunofluorescence placed it at the ankle-link region co-localizing with usherin, GPR98, and whirlin, and pull-downs confirmed direct binding to usherin and GPR98 cytoplasmic domains.

    Evidence Mass spectrometry of chick stereocilia; immunofluorescence in rodent hair cells; pull-down assays in LLC-PK1 cells

    PMID:23055499

    Open questions at the time
    • Functional consequence of PDZD7 loss on ankle-link integrity not yet tested in vivo
    • Binding specificity among USH2 complex members not resolved
  4. 2013 High

    Proving PDZD7 is required for hearing and USH2 complex assembly in vivo: Pdzd7 knockout mice are congenitally deaf with disorganized stereocilia, reduced mechanotransduction currents, and loss of USH2A/GPR98/WHRN from ankle links, establishing PDZD7 as essential for organizing the quaternary USH2 complex.

    Evidence Complete knockout mouse; ABR/DPOAE/cochlear microphonics; scanning electron microscopy; immunolocalization; electrophysiology

    PMID:24334608

    Open questions at the time
    • Whether PDZD7 loss affects retinal function in mammals not addressed
    • Relative contributions of different PDZD7 isoforms unknown
  5. 2014 High

    Resolving the binding architecture of the quaternary USH2 complex: systematic domain mapping showed WHRN preferentially binds USH2A and PDZD7 preferentially binds GPR98, with WHRN–PDZD7 interaction bridging the two receptors; additionally, PDZD7 was found to negatively regulate ADGRV1 Gαi signaling activity.

    Evidence Yeast two-hybrid, pull-downs, colocalization in cell lines (complex architecture); cAMP assay in cell lines (signaling modulation)

    PMID:24962568 PMID:25406310

    Open questions at the time
    • Signaling modulation shown only in heterologous cells, not in hair cells
    • Whether PDZD7-mediated signaling regulation is physiologically relevant in vivo is unknown
  6. 2016 High

    Establishing that MYO7A is required for PDZD7 localization at ankle links: PDZD7 co-fractionates and co-immunoprecipitates with MYO7A from stereocilia membranes, and PDZD7 fails to localize to ankle links in Myo7a mutant mice, revealing MYO7A-dependent transport as the mechanism of PDZD7 positioning.

    Evidence Stereocilia membrane fractionation and mass spectrometry; co-IP in tissue-culture cells; immunolocalization in Myo7a mutant mice

    PMID:27525485

    Open questions at the time
    • Whether MYO7A directly transports PDZD7 or acts indirectly is unclear
    • No reconstitution of motor-cargo complex in vitro
  7. 2019 High

    Demonstrating isoform specificity: only the long PDZD7 isoform localizes to ankle links and is required for hearing; selective disruption of the long isoform phenocopied the full knockout, and PIP5K1C was identified as a long-isoform-specific binding partner, linking PDZD7 to phosphoinositide signaling.

    Evidence Isoform-selective mouse knockout (exon 14 deletion); ABR; immunolocalization; electrophysiology; yeast two-hybrid

    PMID:31914662

    Open questions at the time
    • Functional role of PIP5K1C interaction in stereocilia not tested
    • Functions of short PDZD7 isoforms remain unknown
  8. 2021 High

    Structural elucidation of the HHD domain revealed how PDZD7 targets membranes: crystallography showed a five-helix fold with a unique α1N helix occluding the canonical binding pocket; the HHD binds lipids and mediates plasma membrane localization, and a deafness-causing mutation in this domain abolishes lipid binding.

    Evidence X-ray crystallography at 1.49 Å; lipid-binding assays; subcellular localization in HEK293T cells; disease mutation analysis

    PMID:33937240

    Open questions at the time
    • Lipid species specificity in native stereocilia membranes not determined
    • No in vivo rescue experiments with lipid-binding-deficient mutants
  9. 2022 High

    Atomic-resolution mapping of PDZ-domain interactions: NMR and crystallography revealed that PDZD7 PDZ1–PDZ2 forms a supramodule stabilized upon ADGRV1 PBM binding via atypical β-extensions, while PDZ3 binds FCHSD2 to connect the ankle-link complex to CDC42/N-WASP–mediated actin dynamics; deafness mutations in PDZ binding grooves disrupt these interactions.

    Evidence NMR and ITC for PDZ1–PDZ2/ADGRV1 (solution biophysics); X-ray crystallography at 2.0 Å for PDZ3/FCHSD2; co-IP in COS-7 cells; mutagenesis

    PMID:35695292 PMID:35836927

    Open questions at the time
    • Whether FCHSD2 interaction is functionally required for stereocilia development not tested in vivo
    • Full-length PDZD7 structure and domain arrangement remain undetermined
  10. 2025 Medium

    Nanoscale localization revealed unexpected spatial asymmetry: STED super-resolution showed ADGRV1 and PDZD7 have row-specific asymmetric distributions in stereocilia, differing between inner and outer hair cells, and the ADGRV1 extracellular domain is lost after P12 while the GPCR domain persists, suggesting a signaling function beyond structural scaffolding.

    Evidence STED nanoscopy on juvenile mouse cochlear hair cells

    PMID:40836926

    Open questions at the time
    • Functional significance of row-specific asymmetry is unknown
    • Whether the persistent ADGRV1 GPCR domain signals through PDZD7 in mature hair cells not tested
    • Single-lab observation awaiting independent confirmation

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include whether PDZD7 has a direct role in mammalian retinal function, how the full-length multi-domain protein is spatially organized in the ankle-link complex, whether PDZD7-mediated regulation of ADGRV1 signaling is physiologically relevant in hair cells, and the functional roles of the short PDZD7 isoforms.
  • No mammalian retinal phenotype from PDZD7 loss reported
  • No full-length structure or in situ structural model
  • Short isoform functions completely uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 3 GO:0008289 lipid binding 1 GO:0098772 molecular function regulator activity 1
Localization
GO:0005929 cilium 6 GO:0005886 plasma membrane 3
Pathway
R-HSA-9709957 Sensory Perception 3
Complex memberships
USH2 ankle-link complex (USH2A/ADGRV1/WHRN/PDZD7)

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2010 PDZD7 knockdown in zebrafish produced an Usher-like phenotype, exacerbated retinal cell death in combination with ush2a or gpr98 knockdown, and reduced Gpr98 localization in the region of the photoreceptor connecting cilium, establishing PDZD7 as a modifier of retinal disease and contributor to digenic Usher syndrome through genetic interaction with USH2A and GPR98. Zebrafish morpholino knockdown, epistasis/double-knockdown, immunolocalization The Journal of clinical investigation High 20440071
2012 PDZD7 localizes to the ankle-link region of hair cell stereocilia, overlapping with usherin, whirlin, and GPR98; cytosolic domains of usherin and GPR98 can directly bind to both whirlin and PDZD7, establishing PDZD7 as a scaffolding component of the ankle-link complex. Mass spectrometry of chick stereocilia, immunofluorescence, overexpression of tagged proteins in rat/mouse hair cells, pull-down assays in LLC-PK1 cells The Journal of neuroscience High 23055499
2013 Pdzd7 knockout mice exhibit congenital profound deafness with disorganized stereocilia bundles, reduced mechanotransduction currents, and loss of USH2 protein complex (USH2A, GPR98, WHRN) localization at ankle links in cochlear hair cells, demonstrating that PDZD7 is essential for organizing the USH2 complex at ankle links through direct interactions with all three USH2 proteins. Knockout mouse model, ABR/DPOAE/cochlear microphonics, electron microscopy, immunolocalization, electrophysiology Human molecular genetics High 24334608
2014 PDZD7 overexpression decreased the adenylate cyclase inhibition mediated by the VLGR1 (ADGRV1) β-subunit Gαi coupling, identifying PDZD7 as a negative regulator of VLGR1 constitutive Gαi signaling activity. cAMP assay, co-expression in cell lines, functional mutant analysis The Journal of biological chemistry Medium 24962568
2014 WHRN and PDZD7 are both required to form a quaternary USH2 protein complex with USH2A and GPR98; WHRN preferentially binds USH2A, PDZD7 preferentially binds GPR98, and WHRN-PDZD7 interaction bridges USH2A and GPR98 within the complex. Yeast two-hybrid, pull-down assays, colocalization in cell lines, systematic domain mapping The Journal of biological chemistry High 25406310
2016 MYO7A forms a complex with PDZD7 in stereocilia membrane fractions; MYO7A and PDZD7 interact in tissue-culture cells, and PDZD7 co-localizes to the ankle-link region of stereocilia in wild-type but not Myo7a mutant mice, demonstrating that PDZD7 localization at ankle links depends on MYO7A. Stereocilia membrane fractionation, mass spectrometry, co-immunoprecipitation in tissue-culture cells, immunolocalization in Myo7a mutant mice eLife High 27525485
2018 Yeast two-hybrid screening using the first two PDZ domains of PDZD7 as bait identified novel binding partners including ADGRV1, gelsolin, β-catenin, and CADM1, expanding the known PDZD7 interactome. Yeast two-hybrid screening, expression verification by RT-PCR/immunostaining, ABR measurement in Cadm1 KO mice Neural plasticity Medium 29796015
2019 The PDZD7 long isoform, but not short isoforms, localizes to the ankle region of stereocilia; selective disruption of the long isoform in mice impairs ankle-link complex localization, causes stereocilia development deficits, reduces MET currents, and causes hearing loss; yeast two-hybrid identified PIP5K1C as a long-isoform-specific binding partner. Isoform-selective mouse knockout (exon 14 deletion), ABR, immunolocalization, electrophysiology, yeast two-hybrid FASEB journal High 31914662
2021 The PDZD7 harmonin homology domain (HHD) adopts a five-helix fold and contains a unique α1N helix that occupies the canonical binding pocket; the HHD binds lipids and mediates localization of PDZD7 to the plasma membrane, and a hearing-loss mutation in the N-terminal extension of HHD disrupts lipid binding. X-ray crystallography (1.49 Å), lipid-binding assays, subcellular localization in HEK293T cells, disease mutation analysis Frontiers in cell and developmental biology High 33937240
2022 Both N-terminal PDZ domains of PDZD7 bind the C-terminal PDZ-binding motif (PBM) of ADGRV1 via atypical C-terminal β extensions; the two PDZ domains form a supramodule in solution that is stabilized upon PBM binding; two deafness-causing mutations located in the binding grooves of these PDZ domains disrupt stability and binding. NMR, ITC, mutagenesis, structural biochemistry in solution Frontiers in molecular biosciences High 35836927
2022 PDZD7 PDZ3 domain binds the C-terminal tail of FCHSD2 (a CDC42/N-WASP regulator of cell protrusion); crystal structure at 2.0 Å resolution shows the FCHSD2 PDZ-binding motif stretching through the αB/βB groove of PDZD7 PDZ3, linking the ankle-link complex to cytoskeletal dynamics. Yeast two-hybrid, co-immunoprecipitation in COS-7 cells, X-ray crystallography (2.0 Å) The Biochemical journal High 35695292
2025 Using STED super-resolution nanoscopy, ADGRV1 and PDZD7 show highly asymmetric colocalization within stereocilia rows at the ankle-link region, with distinct distributions between inner and outer hair cells; the ADGRV1 extracellular domain disappears after P12 while the GPCR domain persists until P21, suggesting a signaling role beyond scaffolding. STED nanoscopy on juvenile mouse cochlear hair cells iScience Medium 40836926
2008 Homozygous disruption of PDZD7 by chromosomal translocation causes non-syndromic congenital hearing loss; protein-protein interaction assays showed PDZD7 integrates into the Usher syndrome protein network; PDZD7 shares homology with harmonin (USH1C) and whirlin (DFNB31). FISH, junction fragment cloning/sequencing, RT-PCR for inner ear expression, protein-protein interaction assays Human molecular genetics Medium 19028668

Source papers

Stage 0 corpus · 24 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2010 PDZD7 is a modifier of retinal disease and a contributor to digenic Usher syndrome. The Journal of clinical investigation 196 20440071
2012 Localization of PDZD7 to the stereocilia ankle-link associates this scaffolding protein with the Usher syndrome protein network. The Journal of neuroscience : the official journal of the Society for Neuroscience 63 23055499
2014 Constitutive Gαi coupling activity of very large G protein-coupled receptor 1 (VLGR1) and its regulation by PDZD7 protein. The Journal of biological chemistry 60 24962568
2013 Deletion of PDZD7 disrupts the Usher syndrome type 2 protein complex in cochlear hair cells and causes hearing loss in mice. Human molecular genetics 53 24334608
2014 Whirlin and PDZ domain-containing 7 (PDZD7) proteins are both required to form the quaternary protein complex associated with Usher syndrome type 2. The Journal of biological chemistry 52 25406310
2015 PDZD7 and hearing loss: More than just a modifier. American journal of medical genetics. Part A 50 26416264
2008 Homozygous disruption of PDZD7 by reciprocal translocation in a consanguineous family: a new member of the Usher syndrome protein interactome causing congenital hearing impairment. Human molecular genetics 46 19028668
2019 Lnc-PDZD7 contributes to stemness properties and chemosensitivity in hepatocellular carcinoma through EZH2-mediated ATOH8 transcriptional repression. Journal of experimental & clinical cancer research : CR 44 30786928
2016 PDZD7-MYO7A complex identified in enriched stereocilia membranes. eLife 44 27525485
2016 Confirmation of PDZD7 as a Nonsyndromic Hearing Loss Gene. Ear and hearing 25 26849169
2019 Identification of a Potential Founder Effect of a Novel PDZD7 Variant Involved in Moderate-to-Severe Sensorineural Hearing Loss in Koreans. International journal of molecular sciences 19 31454969
2017 Novel recessive PDZD7 biallelic mutations in two Chinese families with non-syndromic hearing loss. American journal of medical genetics. Part A 18 29048736
2019 Lack of PDZD7 long isoform disrupts ankle-link complex and causes hearing loss in mice. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 17 31914662
2018 Identification of Binding Partners of Deafness-Related Protein PDZD7. Neural plasticity 12 29796015
2021 A novel recessive PDZD7 bi-allelic mutation in an Iranian family with non-syndromic hearing loss. BMC medical genomics 8 33530996
2021 Structure and Membrane Targeting of the PDZD7 Harmonin Homology Domain (HHD) Associated With Hearing Loss. Frontiers in cell and developmental biology 7 33937240
2019 Novel recessive PDZD7 biallelic mutations associated with hereditary hearing loss in a Chinese pedigree. Gene 7 31129248
2022 Deciphering the Molecular Interaction Between the Adhesion G Protein-Coupled Receptor ADGRV1 and its PDZ-Containing Regulator PDZD7. Frontiers in molecular biosciences 4 35836927
2022 Novel homozygous variant in the PDZD7 gene in a family with nonsyndromic sensorineural hearing loss. BMC medical genomics 3 35715776
2022 Deafness-related protein PDZD7 forms complex with the C-terminal tail of FCHSD2. The Biochemical journal 2 35695292
2025 Super-resolution mapping of the ankle link proteins ADGRV1 and PDZD7 in developing auditory hair cells. iScience 1 40836926
2025 A newly discovered Lnc-PDZD7-3 increased metastatic and proliferative potential of lung adenocarcinoma cells via modulating FN1/fibronectin signaling. Frontiers in genetics 1 41199745
2024 Clinical characterizations and molecular genetic study of two co-segregating variants in PDZD7 and PDE6C genes leading simultaneously to non-syndromic hearing loss and achromatopsia. BMC medical genomics 1 38956522
2025 First clinical report of a rare PDZD7 nonsense variant and recurrent mutations in Iranian families with autosomal recessive non-syndromic hearing loss. BMC medical genomics 0 41276803