Affinage

WDR35

WD repeat-containing protein 35 · UniProt Q9P2L0

Length
1181 aa
Mass
133.5 kDa
Annotated
2026-04-28
24 papers in source corpus 9 papers cited in narrative 9 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

WDR35 (IFT121) is a subunit of the IFT-A complex that functions as a COPI-like vesicle coat protein essential for ciliogenesis, retrograde intraflagellar transport, and delivery of membrane cargo to cilia. WDR35 shares deep structural homology with COPI coatomer subunits; in its absence, coat-less vesicles accumulate at the ciliary base and fail to fuse, and recombinant non-core IFT-A proteins including WDR35 bind lipids directly, establishing a vesicular coat mechanism for ciliary membrane protein delivery (PMID:34734804, PMID:21473986). Beyond general retrograde IFT, WDR35 is specifically required for ciliary entry of Smoothened and the EVC/EVC2 complex, distinguishing its function from that of the retrograde dynein motor and linking it to Hedgehog signaling during embryonic development and osteogenic differentiation (PMID:25908617, PMID:30790652). WDR35 also interacts with IFT43 within the IFT-A peripheral subcomplex, associates with CCT chaperonins involved in tubulin folding, and physically binds Rag GTPases to negatively regulate mTORC1 signaling (PMID:28400947, PMID:33610917, PMID:30570184).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2006 High

    The first functional assignment of WDR35/IFTA-1 established it as an IFT-A subcomplex component required for retrograde intraflagellar transport, resolving the question of whether this WD40-repeat protein participates in ciliary trafficking.

    Evidence C. elegans ifta-1 mutant analysis with fluorescence localization and IFT motility assays

    PMID:17021254

    Open questions at the time
    • Mammalian function not yet tested
    • Mechanism of retrograde IFT contribution (motor vs. cargo adapter) unresolved
    • Direct protein–protein interactions within IFT-A not mapped
  2. 2011 High

    Demonstration that mammalian WDR35 localizes to cilia and centrosomes and is absolutely required for ciliogenesis and Hedgehog signaling in vivo established WDR35 as essential for both cilium formation and developmental signaling in vertebrates.

    Evidence Mouse Wdr35 knockout, immunofluorescence in embryos and fibroblasts, structural homology modeling to COPI coatomer

    PMID:21473986

    Open questions at the time
    • Specific ciliary cargoes dependent on WDR35 not identified
    • COPI homology functional significance not experimentally tested
    • Distinction from retrograde dynein motor function unknown
  3. 2015 High

    Genetic epistasis between Wdr35 and the retrograde dynein motor Dync2h1 revealed that WDR35 has a specific, motor-independent role in delivering Smoothened and the EVC/EVC2 complex to cilia, explaining the Hedgehog signaling defects in WDR35 mutants.

    Evidence Immunofluorescence of EVC, EVC2, and SMO in Wdr35−/− versus Dync2h1−/− fibroblasts with functional rescue

    PMID:25908617

    Open questions at the time
    • Direct physical interaction between WDR35 and SMO/EVC not shown
    • Whether other IFT-A subunits share this cargo-specific function unclear
    • Mechanism of cargo selectivity not defined
  4. 2017 Medium

    Identification of IFT43 as a direct functional partner of WDR35 within the IFT-A peripheral subcomplex clarified the subunit organization and showed that mutations in either gene produce overlapping ciliopathy phenotypes.

    Evidence Patient genetics and ciliogenesis assays comparing IFT43 and WDR35 mutant cells

    PMID:28400947

    Open questions at the time
    • Direct biochemical reconstitution of WDR35–IFT43 interaction not performed in this study
    • Stoichiometry and binding interface unknown
    • Whether IFT43 mediates the same cargo specificity as WDR35 untested
  5. 2018 Medium

    Live imaging in Drosophila cilia demonstrated that WDR35/Oseg4 is required not only for retrograde IFT but also for anterograde movement in the distal ciliary segment, extending its transport role beyond simple retrograde function.

    Evidence Time-lapse imaging of IFT88-GFP in Drosophila oseg4 mutant cilia

    PMID:29983040

    Open questions at the time
    • Distal-segment-specific role not confirmed in mammalian systems
    • Mechanism of anterograde involvement unknown
    • Single lab observation
  6. 2019 Low

    Discovery that WDR35 physically binds Rag GTPases (RagA/B/C) and suppresses mTORC1-dependent S6 phosphorylation identified a non-ciliary signaling role, raising the question of whether WDR35 integrates nutrient sensing with ciliogenesis.

    Evidence Co-immunoprecipitation and phospho-S6 western blot upon WDR35 overexpression/knockdown

    PMID:30570184

    Open questions at the time
    • Single Co-IP without reciprocal validation or endogenous-level confirmation
    • Mechanism by which WDR35 inhibits mTORC1 not defined
    • Relevance to ciliary vs. cytoplasmic pools of WDR35 unclear
  7. 2021 High

    In situ electron tomography and lipid-binding reconstitution established that WDR35 and the IFT-A complex function as a bona fide vesicle coat — analogous to COPI — that directly coats and delivers membrane-protein-laden vesicles to cilia, providing the structural and biochemical basis for how ciliary membrane composition is maintained.

    Evidence Mouse Wdr35 mutant electron tomography, recombinant non-core IFT-A lipid binding, biochemical fractionation

    PMID:34734804

    Open questions at the time
    • Full reconstitution of IFT-A coat assembly on liposomes not achieved
    • High-resolution structure of the WDR35-containing coat not available
    • Cargo-sorting signals recognized by the coat not identified
  8. 2021 Medium

    Mass spectrometry interactome analysis linked WDR35 to CCT/TRiC chaperonins involved in tubulin folding and showed that partial WDR35 loss disperses acetylated α-tubulin, connecting WDR35 to cytoskeletal quality control at the ciliary base.

    Evidence Mass spectrometry, immunostaining in WDR35 partial-KO 293T cells, co-immunoprecipitation

    PMID:33610917

    Open questions at the time
    • Direct binding between WDR35 and CCT subunits not biochemically validated
    • Functional consequence of CCT interaction for ciliogenesis not tested by reconstitution
    • Relationship between tubulin folding and vesicle coat function unclear

Open questions

Synthesis pass · forward-looking unresolved questions
  • The molecular logic by which WDR35/IFT-A coat selects specific membrane cargoes (e.g., SMO, EVC) for ciliary delivery, the high-resolution structure of the assembled coat on vesicles, and the physiological significance of the WDR35–Rag GTPase interaction remain unresolved.
  • Cargo-sorting motifs or adaptors for IFT-A coat not identified
  • Cryo-EM or crystal structure of WDR35 within the coat complex absent
  • Endogenous role of WDR35 in mTORC1 regulation not confirmed in vivo

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 2 GO:0008289 lipid binding 1
Localization
GO:0005929 cilium 4 GO:0005815 microtubule organizing center 1 GO:0031410 cytoplasmic vesicle 1
Pathway
R-HSA-1852241 Organelle biogenesis and maintenance 4 R-HSA-162582 Signal Transduction 2 R-HSA-5653656 Vesicle-mediated transport 1
Partners
EVCEVC2IFT43RAGARAGBRAGCSMOTCP1
Complex memberships
IFT-A complex

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2006 C. elegans IFTA-1 (ortholog of WDR35/IFT121) localizes to the base of cilia and undergoes intraflagellar transport; it is required for retrograde IFT, as ifta-1 mutants display shortened cilia with accumulations of core IFT machinery indicative of retrograde transport defects. IFTA-1 co-localizes with the IFT-A subcomplex in bbs and che-11 mutant backgrounds. C. elegans genetics, fluorescence localization, IFT motility analysis, epistasis with bbs and che-11 mutants Molecular biology of the cell High 17021254
2011 WDR35 localizes to cilia and centrosomes throughout the developing mouse embryo; human and mouse fibroblasts lacking WDR35 fail to produce cilia, and Wdr35 mouse mutants display Hedgehog signaling defects (midgestation lethality with Hh pathway abnormalities). Structural modeling shows WDR35 has strong homology to COPI coatamer subunits involved in vesicular trafficking. Immunofluorescence localization in embryo, loss-of-function fibroblasts, mouse knockout phenotyping, structural homology modeling American journal of human genetics High 21473986
2015 WDR35/IFT121 is specifically required for entry of EVC, EVC2, and Smoothened (SMO) into the ciliary compartment; in Wdr35-/- cilia these three proteins fail to localize, but they do localize in Dync2h1-/- (retrograde motor mutant) cilia, indicating IFT121 has a specific role beyond retrograde motor activity in targeting the EvC complex and SMO to cilia, with consequent Hedgehog signaling defects. Immunofluorescence of EVC/EVC2/SMO in Wdr35-/- vs Dync2h1-/- fibroblasts; rescue experiments with disease cDNAs; Hh signaling assays Human molecular genetics High 25908617
2018 Drosophila Oseg4 (WDR35 ortholog) is required for both retrograde IFT and anterograde movement specifically in the distal ciliary segment, as revealed by time-lapse live-cell imaging of IFT88-GFP in oseg4 mutant cilia. Time-lapse live-cell imaging of IFT88-GFP in Drosophila cilia, genetic loss-of-function Molecules and cells Medium 29983040
2019 WDR35 physically interacts with RagA, RagB, and RagC (mTORC1 regulatory GTPases), and overexpression of WDR35 decreases phosphorylation of ribosomal S6 protein in a RagA/RagB/RagC-dependent manner, indicating WDR35 negatively influences mTORC1 activity. Co-immunoprecipitation, overexpression/knockdown, phospho-S6 western blot Genes to cells Low 30570184
2019 WDR35 overexpression or Gli2 overexpression enhances osteogenic differentiation marker gene expression and ALP activity, while WDR35 silencing in C3H10T1/2 cells inhibits cilia formation and osteogenic differentiation; this inhibitory effect is rescued by Gli2 overexpression, placing WDR35 upstream of Gli2/Hedgehog signaling in osteogenic differentiation. siRNA knockdown, overexpression, ALP activity assay, immunofluorescence of cilia, gene expression analysis Gene Medium 30790652
2021 WDR35 associates with CCT complex proteins (TCP1/CCT1 chaperonins for α-tubulin folding), identified by mass spectrometry; partial knockout of WDR35 disperses acetylated α-tubulin from the peri-ciliary region, and RagA (GDP-bound form) binds WDR35 and negatively regulates primary cilium formation. Mass spectrometry interactome, immunostaining in WDR35 partial KO and RagA KO 293T cells, co-immunoprecipitation Biochemical and biophysical research communications Medium 33610917
2021 In the absence of WDR35, small mutant cilia form but fail to enrich diverse classes of ciliary membrane proteins; non-core IFT-A components are degraded and core components accumulate at the ciliary base in Wdr35 mouse mutants. WDR35 and other IFT-A subunits share deep sequence homology with α and β' COPI coatomer subunits. Coat-less vesicles accumulate and fail to fuse with Wdr35 mutant cilia. Recombinant non-core IFT-A proteins bind directly to lipids, providing in situ evidence that WDR35, likely with other IFT-A proteins, forms a coat on vesicles that delivers ciliary membrane cargo. Mouse genetics (Wdr35 mutant), in situ electron tomography, biochemical fractionation, recombinant protein-lipid binding assay, sequence homology analysis eLife High 34734804
2017 WDR35/IFT121 directly interacts with IFT43 as a satellite component of the IFT-A complex; mutations in IFT43 that disrupt ciliogenesis produce a phenotype similar to WDR35/IFT121 mutations, supporting their direct functional interaction in retrograde IFT and endochondral ossification. Patient genetics, ciliogenesis assays in patient-derived cells, phenotypic comparison of IFT43 and WDR35 mutants Cilia Medium 28400947

Source papers

Stage 0 corpus · 24 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2010 Exome sequencing identifies WDR35 variants involved in Sensenbrenner syndrome. American journal of human genetics 231 20817137
2011 Human and mouse mutations in WDR35 cause short-rib polydactyly syndromes due to abnormal ciliogenesis. American journal of human genetics 110 21473986
2006 The WD repeat-containing protein IFTA-1 is required for retrograde intraflagellar transport. Molecular biology of the cell 90 17021254
2015 Specific variants in WDR35 cause a distinctive form of Ellis-van Creveld syndrome by disrupting the recruitment of the EvC complex and SMO into the cilium. Human molecular genetics 48 25908617
2012 WDR35 mutation in siblings with Sensenbrenner syndrome: a ciliopathy with variable phenotype. American journal of medical genetics. Part A 41 22987818
2021 A WDR35-dependent coat protein complex transports ciliary membrane cargo vesicles to cilia. eLife 35 34734804
2017 Mutations in IFT-A satellite core component genes IFT43 and IFT121 produce short rib polydactyly syndrome with distinctive campomelia. Cilia 28 28400947
2012 Bupivacaine-induced apoptosis independently of WDR35 expression in mouse neuroblastoma Neuro2a cells. BMC neuroscience 14 23227925
2017 Uncommon runs of homozygosity disclose homozygous missense mutations in two ciliopathy-related genes (SPAG17 and WDR35) in a patient with multiple brain and skeletal anomalies. European journal of medical genetics 13 29174089
2017 Exome sequencing for the differential diagnosis of ciliary chondrodysplasias: Example of a WDR35 mutation case and review of the literature. European journal of medical genetics 12 28870638
2015 A relatively mild skeletal ciliopathy phenotype consistent with cranioectodermal dysplasia is associated with a homozygous nonsynonymous mutation in WDR35. American journal of medical genetics. Part A 12 26691894
2020 Prenatal genetic diagnosis of cranioectodermal dysplasia in a Polish family with compound heterozygous variants in WDR35. American journal of medical genetics. Part A 9 32804427
2013 Enhanced expression of WD repeat-containing protein 35 (WDR35) stimulated by domoic acid in rat hippocampus: involvement of reactive oxygen species generation and p38 mitogen-activated protein kinase activation. BMC neuroscience 9 23289926
2021 Interfamilial clinical variability in four Polish families with cranioectodermal dysplasia and identical compound heterozygous variants in WDR35. American journal of medical genetics. Part A 8 33421337
2017 Clinical and molecular genetic characterization of a male patient with Sensenbrenner syndrome (cranioectodermal dysplasia) and biallelic WDR35 mutations. Birth defects research 7 29134781
2019 RagA, an mTORC1 activator, interacts with a hedgehog signaling protein, WDR35/IFT121. Genes to cells : devoted to molecular & cellular mechanisms 6 30570184
2018 Time-Lapse Live-Cell Imaging Reveals Dual Function of Oseg4, Drosophila WDR35, in Ciliary Protein Trafficking. Molecules and cells 5 29983040
2022 WDR35 variants in a cranioectodermal dysplasia patient with early onset end-stage renal disease and retinal dystrophy. American journal of medical genetics. Part A 3 35875935
2021 WDR35 is involved in subcellular localization of acetylated tubulin in 293T cells. Biochemical and biophysical research communications 2 33610917
2020 Association study of genetic variants at TTC32-WDR35 gene cluster with coronary artery disease in Chinese Han population. Journal of clinical laboratory analysis 2 33009702
2023 Ciliary phenotyping in renal epithelial cells in a cranioectodermal dysplasia patient with WDR35 variants. Frontiers in molecular biosciences 1 38161384
2025 Case Report: Prenatal diagnosis of novel compound heterozygous variants in WDR35 gene causing short-rib thoracic dysplasia 7 with or without polydactyly. Frontiers in pediatrics 0 39877340
2025 Aberrant Splicing Caused by Compound Heterozygous Variants in WDR35 Identified in a Fetus With Cranioectodermal Dysplasia 2. Prenatal diagnosis 0 40445021
2019 Down-regulated WDR35 contributes to fetal anomaly via regulation of osteogenic differentiation. Gene 0 30790652