CEP70

CEP70 is a centrosomal scaffolding protein that organizes microtubule-based structures across multiple cellular contexts, including interphase microtubule networks, mitotic spindles, cilia, and sperm flagella. It directly binds γ-tubulin through coiled-coil domains, and this interaction—regulated by CYLD-mediated deubiquitination—is required for its centrosomal localization and for ciliogenesis (PMID:21795687, PMID:25342559). CEP70 promotes microtubule stability through interaction with HDAC6 and regulation of tubulin acetylation, and supports cell migration and angiogenesis via activation of Cdc42 and Rac1 (PMID:26112604, PMID:22437770). In mice, CEP70 knockout causes male sterility due to defective acrosome biogenesis and flagella formation during spermiogenesis (PMID:33980814).

1. 2009 High

   Whether CEP70 functions in ciliogenesis was unknown; zebrafish morpholino depletion established that Cep70 is required for cilium elongation—but not basal body formation—across multiple tissues, linking it to intraflagellar-transport-like ciliary phenotypes.

   Evidence Morpholino knockdown in zebrafish embryos with immunofluorescence of cilia length and organ phenotyping (kidney cysts, laterality defects)

   PMID:19254375

   Open questions at the time

   • Mechanism by which CEP70 promotes cilium elongation not defined
   • Whether mammalian CEP70 has the same ciliogenesis role was untested
2. 2011 High

   How CEP70 is retained at the centrosome was unclear; domain-mapping and Co-IP showed that CEP70 directly binds γ-tubulin via coiled-coil domains, and this interaction is necessary for centrosomal localization, interphase microtubule organization, and bipolar spindle assembly.

   Evidence Reciprocal Co-IP with domain-mapping pulldowns and siRNA knockdown with spindle phenotype readouts in mammalian cells

   PMID:21795687

   Open questions at the time

   • Stoichiometry and structural basis of the CEP70–γ-tubulin complex unknown
   • Whether CEP70 recruits additional centrosomal effectors not addressed
3. 2011 Medium

   Whether the CEP70 family has a conserved role in centriole biogenesis was untested; Chlamydomonas CRC70 was shown to scaffold centriole assembly by recruiting SAS-6 and Bld10p, and its overexpression in mammalian cells induced ectopic centriole-related structures.

   Evidence RNAi in Chlamydomonas and overexpression in mouse NIH3T3 cells with immunofluorescence

   PMID:21878503

   Open questions at the time

   • CRC70 is an ortholog, not human CEP70 itself; direct equivalence of scaffold function in mammalian centriole assembly unconfirmed
   • Recruitment mechanism for SAS-6 and Bld10p not defined biochemically
4. 2012 High

   Whether CEP70 has roles beyond microtubule nucleation was unknown; depletion in endothelial cells revealed that CEP70 is required for angiogenesis by enabling centrosome reorientation, microtubule rearrangement, and activation of Cdc42 and Rac1 during directed migration.

   Evidence siRNA knockdown in endothelial cells with wound-healing, tube-formation, transwell assays, in vivo mouse angiogenesis assay, and Rho GTPase pull-down activity assays

   PMID:22437770

   Open questions at the time

   • How CEP70 activates Cdc42/Rac1 mechanistically is not determined
   • Relevant GEF intermediary not identified
5. 2014 High

   What regulates CEP70 centrosomal targeting was unresolved; CYLD was identified as the deubiquitinase that removes polyubiquitin from CEP70, and this modification is required for CEP70–γ-tubulin interaction, centrosomal localization, and ciliogenesis.

   Evidence Co-IP, ubiquitination assays, and CYLD knockout mouse model with ciliogenesis phenotyping

   PMID:25342559

   Open questions at the time

   • The E3 ubiquitin ligase opposing CYLD on CEP70 is not identified
   • Specific ubiquitin chain type and modified residues on CEP70 not mapped
6. 2015 Medium

   How CEP70 influences microtubule dynamics beyond nucleation was unclear; CEP70 was found to interact with HDAC6 and modulate tubulin acetylation, thereby enhancing microtubule resistance to depolymerization.

   Evidence Co-IP, colocalization, cold/nocodazole resistance assays, and tubulin acetylation western blotting after CEP70 manipulation

   PMID:26112604

   Open questions at the time

   • Whether CEP70 modulates HDAC6 activity directly or acts as a scaffold is unresolved
   • Functional significance of this interaction relative to centrosomal versus cytoplasmic CEP70 pools not dissected
7. 2016 Medium

   Whether CEP70 dosage affects centrosome integrity and tumorigenesis was untested; overexpression in pancreatic cancer cells caused mislocalization of γ-tubulin and pericentrin, multipolar spindles, and enhanced tumor growth in xenografts.

   Evidence siRNA knockdown and ectopic overexpression in pancreatic cancer cell lines with centrosome marker IF and xenograft assays

   PMID:26893288

   Open questions at the time

   • Whether CEP70 overexpression is a driver or passenger in clinical pancreatic cancer unresolved
   • Mechanism linking CEP70 dosage to centrosomal protein mislocalization not defined
8. 2021 High

   Whether CEP70 is essential for mammalian fertility was unknown; knockout mice revealed that CEP70 is indispensable for acrosome biogenesis and flagella formation during spermiogenesis, with quantitative proteomics showing global reduction in flagellar, head, and cytoskeletal proteins.

   Evidence CEP70 knockout mouse, TEM/SEM ultrastructural analysis, TMT-based quantitative proteomics, human patient mutation screening

   PMID:33980814

   Open questions at the time

   • Whether human CEP70 mutations are a significant cause of male infertility in clinical populations requires larger cohorts
   • Specific step in acrosome vesicle trafficking disrupted by CEP70 loss not identified

• Major unresolved questions include: the structural basis of the CEP70–γ-tubulin interaction, the identity of the E3 ligase that ubiquitinates CEP70 upstream of CYLD, how CEP70 activates Rho GTPases during migration, and the precise step in acrosome biogenesis that requires CEP70.
• No structural or cryo-EM data for CEP70 or its complexes
• E3 ligase targeting CEP70 not identified
• Mechanism linking CEP70 to Cdc42/Rac1 activation unknown