CFAP47

CFAP47 is a core structural component of the axonemal central apparatus (CA) of motile cilia and sperm flagella, where it physically bridges the two central microtubules to maintain flagellar architecture and motility (PMID:40473901). In situ cryo-electron tomography of mouse sperm resolved CFAP47 as a constituent of the C1–C2 bridge: its N-terminal domains bind the C1 microtubule, its central CFAP47-ring engages HYDIN, and its C-terminal region anchors to the C2 microtubule, and loss of CFAP47 produces a hollowed bridge in the CA with significantly reduced sperm progressive motility [PMID:40473901, PMID:bio_10.1101_2024.08.06.606614]. Consistent with this structural role, hemizygous loss-of-function variants in X-linked CFAP47 in humans reduce CFAP47 protein in spermatozoa and cause multiple morphological abnormalities of the flagella (MMAF) and asthenoteratozoospermia, a phenotype recapitulated in Cfap47-mutant male mice whose sterility is rescued by ICSI (PMID:33472045). Beyond its CA scaffolding function, CFAP47 supports broader flagellar morphogenesis by enabling correct localization of WDR87 to the midpiece (PMID:36571501). Loss-of-function variants also cause primary ciliary dyskinesia affecting respiratory cilia (PMID:37723893) and are associated with cystic kidney disease through a role in renal primary cilia, where Cfap47-knockout mice develop tubular vacuolation and dilation (PMID:39698362).

1. 2021 High

   Establishing that CFAP47 has an essential function in sperm flagella, this work showed that human loss-of-function variants cause a defined male-infertility syndrome rather than being incidental polymorphisms.

   Evidence Whole-exome sequencing of MMAF patients with immunoblotting/immunofluorescence protein quantification and a Cfap47-mutant mouse with ICSI rescue

   PMID:33472045

   Open questions at the time

   • Did not resolve the molecular/structural role of CFAP47 within the flagellum
   • No interacting partners identified
   • Mechanism linking protein loss to flagellar malformation unknown
2. 2022 Medium

   Moving from phenotype to mechanism, this work identified a physical partner of CFAP47 and showed CFAP47 is required for that partner's correct localization, framing CFAP47 as a transport/assembly factor in the midpiece.

   Evidence Co-immunoprecipitation plus immunofluorescence/immunoblotting in CFAP47-mutant human spermatozoa showing WDR87 depletion and mislocalization

   PMID:36571501

   Open questions at the time

   • Single lab; interaction not reciprocally validated
   • Direct vs indirect nature of CFAP47–WDR87 binding unresolved
   • Mechanism of WDR87 transport not defined
3. 2023 Medium

   These studies extended CFAP47's disease relevance beyond sperm to motile respiratory cilia, defining it as a PCD gene, while a separate report linked a missense variant to broader sperm structural defects and additional candidate interactions.

   Evidence WES/qRT-PCR/IF/TEM in patient respiratory epithelium (PCD); IF/WB/Co-IP in CFAP47-mutant sperm reporting interactions with CFAP65, CFAP69, SEPTIN4

   PMID:37424856 PMID:37723893

   Open questions at the time

   • The CFAP65/CFAP69/SEPTIN4 interactions are Low-confidence and lack deep validation
   • How a CA-bridge protein contributes to mitochondrial sheath and annulus defects is unexplained
   • Tissue-specific requirements in respiratory vs sperm cilia not dissected
4. 2024 Medium

   This work generalized CFAP47 function to non-motile primary cilia, implicating it in renal cyst formation and broadening its physiological scope beyond motile-cilia syndromes.

   Evidence Immunohistology of human kidney tubules, Cfap47-knockout mouse histology (tubular vacuolation/dilation), and whole-genome sequencing of cystic kidney patients

   PMID:39698362

   Open questions at the time

   • Mechanism of CFAP47 action in primary (non-motile) cilia undefined
   • Causality of patient variants in kidney disease not proven beyond association
   • Relationship between renal ciliary role and axonemal CA role unclear
5. 2025 High

   Cryo-ET with atomic modelling delivered the decisive mechanistic advance, defining CFAP47 as the structural element that tethers C1 to C2 via domain-specific contacts and HYDIN engagement, explaining why its loss collapses the central-apparatus bridge.

   Evidence In situ cryo-electron tomography and AlphaFold2 modelling of mouse sperm CA with Cfap47-knockout structural and motility analysis

   PMID:40473901

   Open questions at the time

   • Atomic contacts inferred partly from AlphaFold2 modelling rather than direct density at side-chain resolution
   • How the CA-bridge role relates to non-motile renal cilia function unresolved
   • Regulation/assembly order of CFAP47 into the CA not established
6. 2025 Low

   A patient-variant study probed the molecular consequence of a specific missense allele, indicating that some CFAP47 mutations act by reducing transcript abundance/stability rather than solely altering protein structure.

   Evidence qPCR in patient sperm and HEK293 cells transfected with mutant vs wild-type CFAP47 plasmid

   PMID:40636384

   Open questions at the time

   • Single method (qPCR), no protein-level confirmation
   • Mechanism of reduced transcript stability not defined
   • Generalizability to other CFAP47 variants unknown
7. 2026 Low

   This work placed CFAP47 in an additional flagellar protein network, expanding its potential interactome beyond the CA bridge.

   Evidence STRING-guided Co-immunoprecipitation validating CFAP47 as an ADGB (androglobin) interactor in an ADGB/TTC29-associated complex

   PMID:41834962

   Open questions at the time

   • Single Co-IP, single lab, no reciprocal or in vivo validation
   • Functional significance of CFAP47–ADGB association unknown
   • Whether this complex overlaps with the CA-bridge role unresolved

• How CFAP47 is assembled into and recruited to the central apparatus, and how its single molecular scaffold serves both motile (sperm/respiratory) and non-motile (renal) cilia, remains unresolved.
• Assembly/recruitment hierarchy of CFAP47 into the CA bridge unknown
• Mechanistic basis of renal primary-cilia phenotype not connected to CA structure
• Full validated interactome and its functional partitioning undefined