CFAP58

CFAP58 is a cilia- and flagella-associated protein essential for sperm flagellum assembly, axonemal integrity, and sperm head shaping. It localizes along the entire sperm flagellum with enrichment at the mid-piece, where it is required for central pair microtubule assembly, mitochondrial sheath formation, and stabilization of axonemal markers such as SPAG6 and SPEF2 (PMID:32791035, PMID:40675161). Its Chlamydomonas ortholog (FAP58/CCDC147) forms a heterodimeric L-shaped complex with MBO2/CCDC146 that interconnects inner dynein arm b with axonemal regulatory complexes, stabilizing inner arm dynein assembly and controlling ciliary waveform (PMID:38568782). CFAP58 also participates in intra-manchette and intra-flagellar transport by interacting with IFT88 and stabilizing CCDC42, and biallelic loss-of-function mutations in CFAP58 cause multiple morphological abnormalities of the sperm flagella (MMAF) and male infertility in humans (PMID:38602507, PMID:32791035).

1. 2020 High

   Establishing that CFAP58 is a flagellar structural protein required for sperm flagellogenesis resolved its basic biological role: loss of CFAP58 causes axonemal and mitochondrial sheath malformations and reduces key axonemal (SPAG6, SPEF2) and mitochondrial sheath (HSP60) markers, while biallelic mutations cause MMAF in humans.

   Evidence Immunofluorescence, TEM, CRISPR/Cas9 knockout mice, and whole-exome sequencing in human MMAF patients and independent replication cohorts

   PMID:32791035 PMID:33314088

   Open questions at the time

   • Precise molecular mechanism by which CFAP58 organizes axonemal and mitochondrial sheath components was unknown
   • Direct binding partners within the axoneme were not identified
   • Whether CFAP58 functions beyond the flagellum (e.g. in motile or primary cilia) was unresolved
2. 2020 Medium

   Identification of CFAP58 as a testis-enriched interactor of ODF2/Cenexin linked it to midpiece organization and implicated Notch signaling modulation in its ciliary elongation function.

   Evidence Mass spectrometry interactome of Odf2/Cenexin, siRNA knockdown, and pathway inhibitor studies in cell lines

   PMID:31904090

   Open questions at the time

   • Notch pathway connection was based on knockdown plus inhibitor without rescue or genetic confirmation
   • ODF2 interaction not validated by reciprocal Co-IP or in vivo crosslinking
   • Mechanism linking CFAP58–ODF2 interaction to midpiece assembly was not defined
3. 2024 High

   Cryo-ET structural analysis of the Chlamydomonas ortholog revealed that CFAP58 forms an L-shaped heterodimer with CCDC146/MBO2 that physically bridges inner dynein arm b to axonemal regulatory complexes, establishing the first structural model for CFAP58 function in dynein stabilization and ciliary motility.

   Evidence Cryo-electron tomography, comparative proteomics, epitope tagging, and genetic mutant analysis in Chlamydomonas

   PMID:38568782

   Open questions at the time

   • Whether the L-shaped heterodimer architecture is conserved in mammalian sperm axonemes is untested
   • How loss of this complex leads to the full MMAF phenotype including mitochondrial sheath defects is unclear
   • Structural basis for doublet-specific variation of the complex was not fully resolved
4. 2024 Medium

   Discovery that CFAP58 interacts with IFT88 and CCDC42 and is required for normal manchette structure expanded its functional scope beyond flagellar axoneme to include intra-manchette transport and sperm head shaping.

   Evidence Co-immunoprecipitation, Cfap58 knockout mice with manchette and sperm head morphology analysis

   PMID:38602507

   Open questions at the time

   • Whether CFAP58 is a direct cargo adapter in IFT or acts indirectly on transport is unresolved
   • Reciprocal validation of IFT88 and CCDC42 interactions by independent methods is lacking
   • Relative contribution of manchette versus flagellar defects to the infertility phenotype is not delineated
5. 2025 Medium

   A patient-derived truncating mutation modeled in knock-in mice pinpointed CFAP58's role specifically in central pair microtubule assembly, distinguishing this function from its broader axonemal and mitochondrial sheath roles.

   Evidence Cfap58-R188* knock-in mouse model, TEM of central pair defects, immunofluorescence of axonemal protein disorganization

   PMID:40675161

   Open questions at the time

   • Which domain or region of CFAP58 mediates central pair versus outer doublet functions is undefined
   • Whether partial truncation alleles retain some L-shaped heterodimer function with CCDC146 is untested
   • Single lab finding awaiting independent replication

• A unified structural and mechanistic model explaining how CFAP58 coordinates its multiple functions — central pair assembly, inner dynein arm stabilization via the CCDC146 heterodimer, mitochondrial sheath formation, and intra-manchette transport — in mammalian spermatogenesis remains to be established.
• No high-resolution structure of mammalian CFAP58 or its complexes exists
• Domain-function mapping has not been performed for the distinct flagellar and manchette roles
• Whether CFAP58 has roles in motile cilia outside the male germline is unexplored