Affinage

CCDC40

Coiled-coil domain-containing protein 40 · UniProt Q4G0X9

Length
1142 aa
Mass
130.1 kDa
Annotated
2026-06-09
18 papers in source corpus 8 papers cited in narrative 8 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

CCDC40 is an axonemal assembly factor required for the structural organization and motility of motile cilia and sperm flagella (PMID:21131974, PMID:39056782). Together with CCDC39 it forms a molecular ruler complex that establishes and maintains the 96 nm repeat unit along the ciliary axoneme, and CCDC40 is specifically required for the axonemal recruitment and stability of CCDC39, the dynein regulatory complex components GAS8/DRC4 and DNALI1, and multiple inner dynein arm heavy chains including DNAH1, DNAH2, DNAH6, and DNAH7 (PMID:21131974, PMID:39056782, PMID:36873931, PMID:35449766). Loss of CCDC40 misplaces the central pair of microtubules and disrupts inner dynein arm assembly, producing cilia with severely reduced motility while leaving radial spoke structures largely intact (PMID:21131974, PMID:23255504). At the organismal level, CCDC40-driven ciliary beating generates leftward nodal fluid flow that acts upstream of asymmetric Cerl2 and Nodal pathway activation in left-right axis determination, such that its loss randomizes laterality (PMID:28182636). Complete loss-of-function (null) alleles of CCDC40 cause primary ciliary dyskinesia with inner dynein arm loss and axonemal disorganization, and the same defect underlies multiple morphological abnormalities of the sperm flagella (PMID:23255504, PMID:35449766). Restoration of endogenous CCDC40 expression by exogenous mRNA delivery rescues axonemal integration of CCDC39, GAS8/DRC4, and DNALI1 and restores ciliary beating and directional flow, confirming that CCDC40 is the rate-limiting determinant of this assembly program (PMID:42089334).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2010 High

    Established CCDC40 as a ciliary protein required to recruit CCDC39 and to assemble inner dynein arms and dynein regulatory complexes, defining its core role in axonemal organization.

    Evidence Loss-of-function mutants in mouse, zebrafish, and human with immunofluorescence and TEM of ciliary ultrastructure

    PMID:21131974

    Open questions at the time
    • Did not resolve whether CCDC40-CCDC39 interaction is direct or how the ruler measures the 96 nm repeat
    • No biochemical reconstitution of the complex
  2. 2013 Medium

    Showed that PCD-causing alleles are null mutations and redefined the resulting defect as IDA loss with microtubular disorganization rather than a radial spoke defect.

    Evidence Sequencing of 54 PCD families with TEM of ciliary ultrastructure

    PMID:23255504

    Open questions at the time
    • Genotype-phenotype correlation for hypomorphic vs null alleles not established
    • Molecular basis of central-pair and IDA defects not mechanistically dissected
  3. 2017 Medium

    Placed CCDC40-dependent ciliary flow genetically upstream of Nodal pathway activation, explaining how loss of ciliary motility randomizes the left-right axis.

    Evidence Genetic epistasis (Ccdc40 mutant x Nodal hypomorph) with in situ hybridization for Nodal, Lefty, and Cerl2 markers

    PMID:28182636

    Open questions at the time
    • Does not address direct molecular signaling between flow and Cerl2
    • Single lab epistasis study
  4. 2022 Low

    Extended CCDC40's IDA-assembly requirement to sperm flagella by linking deficiency to absent DNAH2 and the MMAF phenotype.

    Evidence Immunofluorescence, high-speed video, SEM, and Papanicolaou staining in a single patient

    PMID:35449766

    Open questions at the time
    • Single patient without functional reconstitution
    • Primarily descriptive immunofluorescence
    • Generality to other CCDC40 alleles not tested
  5. 2022 Low

    Confirmed the pathogenic mechanism of a specific splice-site variant at the RNA/protein level.

    Evidence Minigene splicing assay with WES and Sanger sequencing

    PMID:36245716

    Open questions at the time
    • Minigene assay in a single lab without a cilia functional readout for this variant
    • Effect on ciliary ultrastructure not measured
  6. 2023 Medium

    Demonstrated that CCDC40 is required for CCDC39 stability in sperm flagella, extending the assembly dependency beyond respiratory cilia.

    Evidence Immunofluorescence, TEM, and high-speed video on sperm flagella from CCDC40-mutant individuals

    PMID:36873931

    Open questions at the time
    • Whether the interaction is direct not biochemically demonstrated
    • Single lab cohort
  7. 2024 Medium

    Defined the CCDC40-CCDC39 molecular ruler and broadened the set of CCDC40-dependent IDA heavy chains to include DNAH1, DNAH6, and DNAH7.

    Evidence Immunofluorescence with multiple IDA markers in 51 individuals with CCDC39/CCDC40 variants plus NGS

    PMID:39056782

    Open questions at the time
    • No in vitro reconstitution of the ruler complex
    • Order of recruitment among IDA heavy chains not resolved
  8. 2026 Medium

    Showed that restoring CCDC40 expression is sufficient to rescue axonemal assembly and motility, validating CCDC40 as the rate-limiting determinant of the assembly program.

    Evidence LNP-CCDC40 mRNA delivery to patient nasal epithelial cultures and ccdc40-/- zebrafish with beat frequency, particle transport, and flow assays

    PMID:42089334

    Open questions at the time
    • Durability and dosing of mRNA rescue not characterized
    • Single lab; not tested across allelic spectrum

Open questions

Synthesis pass · forward-looking unresolved questions
  • The biochemical basis of how the CCDC40-CCDC39 ruler measures and templates the 96 nm repeat, and whether CCDC40 binds its partners directly, remains unresolved.
  • No in vitro reconstitution of the ruler complex
  • Direct vs indirect binding to CCDC39 and IDA components not established
  • Structural model of the repeat-templating mechanism absent

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 3 GO:0005198 structural molecule activity 2
Localization
GO:0005929 cilium 3 GO:0005856 cytoskeleton 2
Pathway
R-HSA-1852241 Organelle biogenesis and maintenance 2 R-HSA-1266738 Developmental Biology 1
Partners
CCDC39DNAH1DNAH2DNAH6DNAH7DNALI1GAS8
Complex memberships
CCDC40-CCDC39 molecular ruler complexciliary axoneme

Evidence

Reading pass · 8 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2010 CCDC40 localizes to motile cilia and the apical cytoplasm, and is required for axonemal recruitment of CCDC39; loss of CCDC40 in mouse, zebrafish, and human results in misplacement of the central pair of microtubules and defective assembly of inner dynein arms and dynein regulatory complexes, causing cilia with reduced ranges of motility. Genetic loss-of-function (mouse and zebrafish mutants, human patient mutations), immunofluorescence localization, transmission electron microscopy of ciliary ultrastructure Nature genetics High 21131974
2013 CCDC39 and CCDC40 mutations cause PCD with inner dynein arm loss and axonemal disorganization; all identified mutations were nonsense, splice, or frameshift predicting complete protein loss ('null' alleles), demonstrating that the phenotype results from complete absence of functional CCDC39/CCDC40 protein. Radial spoke structures are largely intact in these patients, redefining the defect as 'IDA and microtubular disorganisation' rather than 'radial spoke defect'. Sequencing of 54 PCD families, transmission electron microscopy of ciliary ultrastructure Human mutation Medium 23255504
2017 In Ccdc40 mutant mouse embryos, defective cilia motility impairs fluid flow across the node, causing delayed and randomized asymmetric Cerl2 expression, which leads to delayed and randomized Nodal expression around the node and bilateral reduction of Nodal activation, resulting in left isomerism. Genetic reduction of Nodal dosage in Ccdc40 mutants shifts outcome toward right isomerism, placing CCDC40-driven cilia flow upstream of Nodal pathway activation in left-right axis determination. Genetic epistasis (Ccdc40 mutant × Nodal hypomorph double mutant), in situ hybridization for Lefty1, Lefty2, Nodal, Cerl2 expression in lateral plate mesoderm and node PloS one Medium 28182636
2024 CCDC40 and CCDC39 form a molecular ruler complex maintaining the 96 nm repeat units along ciliary axonemes; disease-causing variants in either gene cause absence of IDA heavy chains DNAH1, DNAH6, and DNAH7 (centrin2-containing IDAs) from respiratory ciliary axonemes, in addition to previously known absence of GAS8, CCDC39, and DNALI1. Immunofluorescence analysis of respiratory cilia from a cohort of 51 individuals with CCDC39/CCDC40 disease-causing variants, next-generation sequencing Cells Medium 39056782
2023 In sperm flagella of individuals with CCDC40 pathogenic variants, CCDC39 protein is absent or severely reduced, providing direct evidence that CCDC40 is required for CCDC39 stability/assembly in sperm flagella (as well as respiratory cilia), and demonstrating a physical interaction between CCDC39 and CCDC40 in this compartment. Immunofluorescence microscopy on sperm flagella from CCDC40-mutant individuals, transmission electron microscopy, high-speed video microscopy Frontiers in genetics Medium 36873931
2026 Exogenous LNP-formulated CCDC40 mRNA delivered to CCDC40-deficient human nasal respiratory epithelial cells enables endogenous CCDC40 expression and axonemal integration of CCDC40-associated proteins CCDC39, GAS8/DRC4, and DNALI1, significantly restoring ciliary beat frequency and ciliary particle transport. In ccdc40-/- zebrafish, injected or topically applied LNP-CCDC40-mRNA restores ciliary motility and establishes directional flow in olfactory pits. mRNA therapy in air-liquid interface cultures from CCDC40-deficient patients and ccdc40-/- zebrafish; high-speed video microscopy, immunofluorescence microscopy, fluorescent particle transport assay, fluid flow assay American journal of respiratory cell and molecular biology Medium 42089334
2022 CCDC40 compound heterozygous loss-of-function variants cause absence of inner dynein arm protein DNAH2 in both respiratory cilia and sperm flagella, demonstrating that CCDC40 is required for IDA assembly in flagella as well as cilia, and linking CCDC40 deficiency to multiple morphological abnormalities of the sperm flagella (MMAF) phenotype. Immunofluorescence on respiratory cilia and sperm, high-speed video microscopy, scanning electron microscopy, Papanicolaou staining Pharmacogenomics and personalized medicine Low 35449766
2022 The CCDC40 splice-site variant c.2236-2delA causes formation of a truncated protein via splicing disruption, as demonstrated by a minigene assay, confirming the pathogenic mechanism of this mutation at the RNA/protein level. Minigene splicing assay using pcDNA3.1(+) plasmid, whole-exome sequencing, Sanger sequencing Frontiers in pediatrics Low 36245716

Source papers

Stage 0 corpus · 18 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2010 The coiled-coil domain containing protein CCDC40 is essential for motile cilia function and left-right axis formation. Nature genetics 260 21131974
2013 Mutations in CCDC39 and CCDC40 are the major cause of primary ciliary dyskinesia with axonemal disorganization and absent inner dynein arms. Human mutation 158 23255504
2012 Delineation of CCDC39/CCDC40 mutation spectrum and associated phenotypes in primary ciliary dyskinesia. Journal of medical genetics 79 22693285
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
2015 CCDC40 mutation as a cause of primary ciliary dyskinesia: a case report and review of literature. The clinical respiratory journal 22 25619595
2022 Novel Compound Heterozygous Variants in CCDC40 Associated with Primary Ciliary Dyskinesia and Multiple Morphological Abnormalities of the Sperm Flagella. Pharmacogenomics and personalized medicine 12 35449766
2021 CCDC40 mutation as a cause of infertility in a Chinese family with primary ciliary dyskinesia. Medicine 11 34941110
2024 Primary Ciliary Dyskinesia Associated Disease-Causing Variants in CCDC39 and CCDC40 Cause Axonemal Absence of Inner Dynein Arm Heavy Chains DNAH1, DNAH6, and DNAH7. Cells 9 39056782
2018 Generation of the induced pluripotent stem cell line UHOMi001-A from a patient with mutations in CCDC40 gene causing Primary Ciliary Dyskinesia (PCD). Stem cell research 7 30296669
2017 Mechanism for generation of left isomerism in Ccdc40 mutant embryos. PloS one 6 28182636
2013 Identification of the first deletion-insertion involving the complete structure of GAA gene and part of CCDC40 gene mediated by an Alu element. Gene 6 23402890
2018 Severe disease due to CCDC40 gene variants and the perils of late diagnosis in primary ciliary dyskinesia. BMJ case reports 5 30209139
2022 Pulmonary Hypertension in a Patient With Kartagener's Syndrome and a Novel Homozygous Nonsense Mutation in CCDC40 Gene: A Case Report. Frontiers in medicine 4 35433722
2024 Identification of a Homozygous Mutation of CCDC40 in a Chinese Infertile Man with MMAF and PCD-like Phenotypes. Genetic testing and molecular biomarkers 3 38837151
2022 Novel compound heterozygous CCDC40 mutations in a familial case of primary ciliary dyskinesia. Frontiers in pediatrics 3 36245716
2026 mRNA therapy improves the composition and motility in CCDC40-deficient cilia in vitro and in vivo. American journal of respiratory cell and molecular biology 0 42089334
2025 Genomic Complexity of ccdc40 in Xenopus : Implications for CRISPR Targeting and Disease Modeling. microPublication biology 0 40415903
2024 Novel rare variation of CCDC40 plays a role in the development of idiopathic scoliosis possibly via dysfunction of cilia motility. The spine journal : official journal of the North American Spine Society 0 39662682

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