Affinage

RSPH9

Radial spoke head protein 9 homolog · UniProt Q9H1X1

Length
276 aa
Mass
31.3 kDa
Annotated
2026-06-10
36 papers in source corpus 13 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 4/4 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

RSPH9 is a core structural component of the radial spoke head of axonemal '9+2' motile cilia and sperm flagella, where it is required for radial spoke head assembly, central pair microtubule stability, and the normal planar ciliary beat (PMID:19200523, PMID:30383886). Its incorporation into the axoneme is governed by an ordered assembly hierarchy in respiratory cilia, RSPH4A > RSPH1 > RSPH9, such that loss of either upstream factor strips RSPH9 from cilia while RSPH9 loss leaves RSPH4A and RSPH1 assembly intact (PMID:25789548, PMID:24518672); in sperm flagella RSPH6A acts upstream of RSPH9 (PMID:30185526). Within the spoke architecture RSPH9 constitutes the RS1 head together with RSPH3, RSPH6A, and DYDC1, and also localizes to the RS3 head where its direct interaction with LRRC23 is required for RS3 head assembly (PMID:38091523, PMID:39849482); it further engages SPEF2 and the dynein DNAH12, the latter coupling the radial spoke head to central pair stability (PMID:34755699, PMID:39849482). Loss of RSPH9 causes near-complete central pair loss and converts the ciliary beat from planar to rotational, producing neonatal hydrocephalus in mice and, in humans, primary ciliary dyskinesia with sperm dysmotility and male infertility (PMID:30383886, PMID:32709945, PMID:36873931).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2009 High

    Established RSPH9 as a disease gene and assigned it to the radial spoke head, answering whether this gene is causally required for normal motile cilia function.

    Evidence Positional cloning of PCD families plus morpholino knockdown with rescue in zebrafish and Chlamydomonas

    PMID:19200523

    Open questions at the time
    • Did not resolve the molecular activity of RSPH9 within the spoke head
    • No structural placement within the radial spoke
  2. 2014 High

    Showed RSPH9 axonemal assembly depends on RSPH1, indicating RSPH9 is part of an interdependent spoke head module rather than independently anchored.

    Evidence Patient cilia immunofluorescence and TEM with defined RSPH1 mutations

    PMID:24518672

    Open questions at the time
    • Did not define the full ordering relative to RSPH4A
    • Mechanism of recruitment not resolved
  3. 2015 High

    Resolved the assembly hierarchy RSPH4A > RSPH1 > RSPH9, establishing RSPH9 as a terminal/dependent member whose loss does not destabilize upstream components.

    Evidence High-resolution immunofluorescence across multiple patient genotypes in respiratory cilia

    PMID:25789548

    Open questions at the time
    • Hierarchy defined for respiratory cilia, not sperm flagella
    • Does not show direct physical contacts between hierarchy members
  4. 2016 High

    Extended RSPH9 function beyond canonical 9+2 cilia by showing it localizes to and is required for both 9+2 and 9+0 axonemes and sensory kinocilia.

    Evidence CRISPR mutagenesis, localization, and behavioral/structural assays in zebrafish

    PMID:27687975

    Open questions at the time
    • Mechanism of RSPH9 function in 9+0 cilia lacking a central pair unexplained
    • Mammalian relevance of kinocilia role not tested
  5. 2018 High

    Linked RSPH9 depletion mechanistically to central pair loss and beat-pattern conversion, and showed it stabilizes a network of radial spoke proteins.

    Evidence RNAi knockdown in mouse ependymal cells with high-speed video, TEM, and RS protein quantification

    PMID:30383886

    Open questions at the time
    • Does not establish which interactions are direct
    • Causal order between central pair loss and beat change unresolved
  6. 2018 Medium

    Placed RSPH6A upstream of RSPH9 in sperm flagellar spoke assembly, indicating tissue-specific upstream dependencies.

    Evidence Rsph6a knockout mouse with sperm flagella immunofluorescence

    PMID:30185526

    Open questions at the time
    • Single KO model with single readout for the RSPH9-specific finding
    • Direct interaction not tested
  7. 2022 Medium

    Identified SPEF2 as a physical partner of RSPH9, suggesting cooperation during flagellar assembly.

    Evidence In vitro co-immunoprecipitation alongside SPEF2-mutant patient sperm proteomics

    PMID:34755699

    Open questions at the time
    • Single in vitro interaction without mutagenesis confirmation
    • Functional consequence of the interaction not established
  8. 2023 High

    Provided the first direct biochemical and structural placement of RSPH9 in the RS3 head via its LRRC23 interaction, defining a specific binding interface required for RS3 head assembly.

    Evidence Purified recombinant protein interaction with C-terminal truncation mutagenesis and cryo-ET of mutant spermatozoa

    PMID:36865175 PMID:38091523

    Open questions at the time
    • Mapped LRRC23 interface but not the RSPH9 residues involved
    • RS3 vs RS1 head dual assignment not fully reconciled
  9. 2023 Medium

    Demonstrated RSPH9 deficiency in human sperm flagella causing dysmotility, extending the PCD phenotype to male infertility with altered flagellar RSPH9 composition.

    Evidence NGS, immunofluorescence, high-speed video, and TEM of sperm from an RSPH9-mutant individual

    PMID:36873931

    Open questions at the time
    • Single patient
    • Does not dissect molecular basis of flagellar dysmotility
  10. 2025 Medium

    Assigned RSPH9 to the RS1 head with RSPH3, RSPH6A, and DYDC1, and linked it to central pair stability through DNAH12, integrating the spoke head with a dynein/central pair regulatory axis.

    Evidence Mass spectrometry, Co-IP, structural modeling, and Iqub/Dnah12 mouse models

    PMID:39849482

    Open questions at the time
    • Direct vs indirect nature of DNAH12 interaction unclear
    • Reconciliation of RS1 and RS3 head assignments incomplete

Open questions

Synthesis pass · forward-looking unresolved questions
  • The molecular activity of RSPH9 within the spoke head — its precise structural role and how it couples spoke head integrity to central pair maintenance — remains undefined.
  • No enzymatic or biochemical activity assigned
  • Mechanism linking spoke head loss to central pair collapse not resolved
  • Full set of direct binding partners and stoichiometry within the radial spoke unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 5
Localization
GO:0005929 cilium 4 GO:0005856 cytoskeleton 3
Partners
DNAH12DNAJB13DYDC1LRRC23RSPH1RSPH3RSPH6ASPEF2
Complex memberships
radial spoke head (RS1 head)radial spoke head (RS3 head)

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 RSPH9 encodes a protein component of the axonemal radial spoke head; loss-of-function mutations cause primary ciliary dyskinesia with central-microtubular-pair abnormalities; knockdown of RSPH9 orthologs in zebrafish and Chlamydomonas disrupts normal motile cilia beat pattern, which is rescued by reintroduction of gene expression SNP-based linkage analysis, positional cloning, in situ hybridization (murine Rsph9), morpholino knockdown in zebrafish, rescue experiment in zebrafish American journal of human genetics High 19200523
2015 RSPH4A is the core protein of the radial spoke head; RSPH4A mutations result in deficient axonemal assembly of both RSPH1 and RSPH9; RSPH1 mutations cause loss of RSPH9 from cilia; RSPH9 mutations cause axonemal absence of RSPH9 but do not affect assembly of RSPH1 or RSPH4A, establishing an assembly hierarchy: RSPH4A > RSPH1 > RSPH9 High-resolution immunofluorescence analysis of human respiratory cilia from patients with biallelic mutations in RSPH9, RSPH4A, and RSPH1 American journal of respiratory cell and molecular biology High 25789548
2014 Loss-of-function mutations in RSPH1 cause loss of RSPH4A and RSPH9 from cilia, suggesting RSPH1 mutations result in loss of the entire radial spoke head structure; RSPH9 is therefore dependent on RSPH1 for its axonemal assembly Targeted NGS panel sequencing, high-resolution immunofluorescence of human respiratory cilia, ultrastructural analysis by TEM Human molecular genetics High 24518672
2018 Mouse Rsph9 is specifically expressed in tissues containing motile cilia and is upregulated during multiciliation; Rsph9 localizes to the ciliary axoneme consistent with its role as a radial spoke subunit; RNAi-mediated depletion of Rsph9 in mouse ependymal cilia causes near-complete central pair loss, converts ciliary beat pattern from planar to rotational, and markedly downregulates multiple radial spoke proteins including other head components RNAi knockdown in mouse ependymal cells, immunofluorescence localization, high-speed video microscopy, TEM Biology of the cell High 30383886
2016 Zebrafish Rsph9 localizes to both 9+2 and 9+0 ciliary axonemes; CRISPR-mediated rsph9 mutation disrupts motility of presumptive 9+2 olfactory cilia and 9+0 neural cilia, and impairs structural integrity of both axoneme types; rsph9 mutant larvae show reduced acoustic startle response consistent with hearing impairment, revealing a role in kinocilia of the inner ear CRISPR mutagenesis in zebrafish, immunofluorescence localization, behavioral assays (acoustic startle response), structural analysis Scientific reports High 27687975
2020 Deletion of Rsph9 in mice leads to neonatal hydrocephalus; Rsph9-/- ependymal cilia show lower beating amplitude and irregular rotational beating pattern; centriolar patch size is increased in Rsph9-/- cells; TEM reveals ectopic ciliary membrane inclusions in Rsph9-/- cilia without gross axonemal organizational defects; hydrocephalus results in astrogliosis, microgliosis, and cerebrovascular abnormalities Rsph9 knockout mouse model, high-speed video microscopy, TEM, immunofluorescence Scientific reports High 32709945
2018 RSPH9 protein disappears from sperm flagella in Rsph6a knockout mice, indicating that RSPH6A is required upstream of RSPH9 for radial spoke assembly in sperm flagella Rsph6a knockout mouse model, immunofluorescence of sperm flagella Journal of cell science Medium 30185526
2022 SPEF2 interacts with RSPH9 in vitro, suggesting SPEF2 and RSPH9 functionally cooperate during sperm flagellar assembly Co-immunoprecipitation in vitro (proteomic analysis of SPEF2 mutant patient spermatozoa plus in vitro interaction assay) Asian journal of andrology Medium 34755699
2023 Purified recombinant LRRC23 directly interacts with RSPH9 (an RS head protein), and this interaction is abolished by C-terminal truncation of LRRC23; cryo-electron tomography shows absence of the RS3 head in LRRC23 mutant spermatozoa, placing RSPH9 as a component of the RS3 head and demonstrating that LRRC23 is required for RS3 head assembly via its interaction with RSPH9 Recombinant protein interaction assay (purified proteins), C-terminal truncation mutagenesis, cryo-electron tomography of mutant spermatozoa eLife High 38091523
2023 LRRC23 interacts with RSPH9 (RS head protein) in vitro, and C-terminal truncation abolishes this interaction; cryo-ET confirms RS3 head loss in LRRC23 mutant sperm (preprint version of the eLife paper above) Recombinant protein interaction assay, mutagenesis, cryo-electron tomography bioRxivpreprint Medium 36865175
2023 Pathogenic variants in RSPH9 cause male infertility due to sperm cell dysmotility and abnormal flagellar RSPH9 protein composition, demonstrated for the first time by immunofluorescence microscopy in sperm cells from an RSPH9-mutant individual Next-generation sequencing, immunofluorescence microscopy of sperm flagella, high-speed video microscopy, transmission electron microscopy, semen analysis Frontiers in genetics Medium 36873931
2025 RSPH9 is identified as a component of radial spoke 1 (RS1) head in human and mouse sperm flagella; RSPH9, along with RSPH3, RSPH6A, and DYDC1, constitutes the RS1 head; DNAH12 interacts with radial spoke head proteins RSPH1, RSPH9, and DNAJB13 to regulate central pair stability in sperm flagella Protein mass spectrometry, western blotting, co-immunoprecipitation, Iqub-/- mouse model, bioinformatic structural modeling Cell communication and signaling : CCS Medium 39849482
2024 DNAH12 interacts with radial spoke head proteins RSPH1, RSPH9, and DNAJB13; disruption of DNAH12 compromises central pair stability; this interaction positions RSPH9 functionally near the inner dynein arm/central pair regulatory axis in sperm flagella Co-immunoprecipitation, mouse knockout model (Dnah12-/-), TEM, immunofluorescence bioRxivpreprint Medium
2017 RSPH9 is a high-abundance component of human airway ciliary axonemes, quantified at 1850 fmol by label-free LC/MSE, establishing it as one of the most abundant non-tubulin axonemal proteins Label-free quantitative LC/MSE proteomics of human airway cilia axonemes Journal of proteome research Medium 28282151

Source papers

Stage 0 corpus · 36 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2009 Mutations in radial spoke head protein genes RSPH9 and RSPH4A cause primary ciliary dyskinesia with central-microtubular-pair abnormalities. American journal of human genetics 271 19200523
2015 Immunofluorescence Analysis and Diagnosis of Primary Ciliary Dyskinesia with Radial Spoke Defects. American journal of respiratory cell and molecular biology 104 25789548
2018 RSPH6A is required for sperm flagellum formation and male fertility in mice. Journal of cell science 86 30185526
2014 Targeted NGS gene panel identifies mutations in RSPH1 causing primary ciliary dyskinesia and a common mechanism for ciliary central pair agenesis due to radial spoke defects. Human molecular genetics 76 24518672
2017 Quantitative Proteomic Analysis of Human Airway Cilia Identifies Previously Uncharacterized Proteins of High Abundance. Journal of proteome research 69 28282151
2021 Clinical and Genetic Spectrum of Children With Primary Ciliary Dyskinesia in China. Chest 64 33577779
2016 Genome-wide DNA methylation analysis in hepatocellular carcinoma. Oncology reports 49 26883180
2019 Bioinformatic identification of candidate biomarkers and related transcription factors in nasopharyngeal carcinoma. World journal of surgical oncology 42 30935420
2019 A Six-Gene Signature Predicts Survival of Adenocarcinoma Type of Non-Small-Cell Lung Cancer Patients: A Comprehensive Study Based on Integrated Analysis and Weighted Gene Coexpression Network. BioMed research international 28 31886214
2015 High-resolution genomic analysis does not qualify atypical plexus papilloma as a separate entity among choroid plexus tumors. Journal of neuropathology and experimental neurology 27 25575132
2023 Pathogenic gene variants in CCDC39, CCDC40, RSPH1, RSPH9, HYDIN, and SPEF2 cause defects of sperm flagella composition and male infertility. Frontiers in genetics 25 36873931
2019 Wide phenotypic variability in RSPH9-associated primary ciliary dyskinesia: review of a case-series from Cyprus. Journal of thoracic disease 23 31285900
2020 Loss of Rsph9 causes neonatal hydrocephalus with abnormal development of motile cilia in mice. Scientific reports 20 32709945
2022 Sperm flagellar 2 (SPEF2) is essential for sperm flagellar assembly in humans. Asian journal of andrology 19 34755699
2020 Immunofluorescence Analysis as a Diagnostic Tool in a Spanish Cohort of Patients with Suspected Primary Ciliary Dyskinesia. Journal of clinical medicine 18 33182294
2018 Rsph9 is critical for ciliary radial spoke assembly and central pair microtubule stability. Biology of the cell 18 30383886
2010 Founder mutation(s) in the RSPH9 gene leading to primary ciliary dyskinesia in two inbred Bedouin families. Annals of human genetics 17 20070851
2016 Novel roles for the radial spoke head protein 9 in neural and neurosensory cilia. Scientific reports 15 27687975
2023 LRRC23 truncation impairs radial spoke 3 head assembly and sperm motility underlying male infertility. eLife 14 38091523
2022 Combining RSPH9 founder mutation screening and next-generation sequencing analysis is efficient for primary ciliary dyskinesia diagnosis in Saudi patients. Journal of human genetics 7 35046476
2022 Motile Ciliary Disorders of the Nasal Epithelium in Adults With Bronchiectasis. Chest 7 36435264
2021 Clinical and molecular characteristics of primary ciliary dyskinesia: A tertiary care centre experience. International journal of pediatrics & adolescent medicine 7 34401452
2019 An Integrated Analysis of Radial Spoke Head and Outer Dynein Arm Protein Defects and Ciliogenesis Abnormality in Nasal Polyps. Frontiers in genetics 7 31798623
2025 IQUB mutation induces radial spoke 1 deficiency causing asthenozoospermia with normal sperm morphology in humans and mice. Cell communication and signaling : CCS 6 39849482
2024 Application of sperm motion kinematics and motility-related proteins for prediction of male fertility. Theriogenology 6 38359560
2023 Clinical and Genetic Characterization of Patients with Primary Ciliary Dyskinesia in Southwest Saudi Arabia: A Cross Sectional Study. Children (Basel, Switzerland) 6 37892347
2023 LRRC23 truncation impairs radial spoke 3 head assembly and sperm motility underlying male infertility. bioRxiv : the preprint server for biology 3 36865175
2021 alms1 mutant zebrafish do not show hair cell phenotypes seen in other cilia mutants. PloS one 3 33793549
2021 Severe herpes virus 6 interstitial pneumonia in an infant with three variants in genes predisposing to lung disease. Journal of medical virology 3 33851733
2024 Exploring nasopharyngeal carcinoma genetics: Bioinformatics insights into pathways and gene associations. The Medical journal of Malaysia 2 39352166
2023 Mapping the Most Common Founder Variant in RSPH9 That Causes Primary Ciliary Dyskinesia in Multiple Consanguineous Families of Bedouin Arabs. Journal of clinical medicine 2 37892643
2023 An Integrated Analysis Reveals Ciliary Abnormalities in Antrochoanal Polyps. Journal of inflammation research 1 36820148
2023 Primary Ciliary Dyskinesia and Type 1 Diabetes: True Association or Circumstantial? Cureus 1 37351244
2026 Associations of air pollution and genetic risk and their interaction with risk of Alzheimer's disease: identification of risk loci and potential biological pathways. GeroScience 0 41571964
2025 Prevalence and Nationality Distribution of Known and Novel Genetic Variants in Children With Primary Ciliary Dyskinesia in the State of Qatar. Clinical genetics 0 41267578
2022 An Unusual Cause of Respiratory Distress in Term Neonate. Cureus 0 36059358

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