EFCAB7

EFCAB7 is a core subunit of the EvC ciliary complex that facilitates Hedgehog/Gli pathway activation at primary cilia. It forms a heterotetramer with IQCE, EVC, and EVC2, directly binding a C-terminal disordered region of EVC2 to anchor the EVC-EVC2 module within the EvC zone at the ciliary base; depletion of EFCAB7 causes EVC-EVC2 mislocalization and impaired GLI2 activation (PMID:24582806, PMID:37576597). Loss-of-function mutations in EFCAB7 cause autosomal recessive nonsyndromic postaxial polydactyly in humans (PMID:37684519), and a splicing variant produces impaired ciliogenesis, disrupted Shh-Gli signaling, and Tetralogy of Fallot-like cardiac defects in a mouse knockin model (PMID:39894222). In a distinct context, EFCAB7 interacts with PARK7 (DJ-1) in hepatocellular carcinoma cells to promote proliferation and metastasis (PMID:39276379).

1. 2014 High

   The central question of how EVC-EVC2 is confined to the EvC zone at the ciliary base was answered by identifying EFCAB7-IQCE as the anchoring complex, establishing EFCAB7 as a required positive regulator of Hedgehog/Gli signaling.

   Evidence Reciprocal Co-IP, siRNA knockdown with ciliary localization imaging, GLI2 reporter assays, and domain-mapping of EVC2 binding in mammalian cells

   PMID:24582806

   Open questions at the time

   • Structural basis of the EFCAB7-EVC2 interaction unresolved
   • Whether EFCAB7's EF-hand domains bind calcium and whether calcium regulates complex assembly unknown
   • In vivo developmental consequences of EFCAB7 loss not yet tested
2. 2016 Low

   Patient genetics provided the first human evidence that EFCAB7 variants modify EvC-related disease severity, linking EFCAB7 to Ellis-van Creveld syndrome as a genetic modifier.

   Evidence Sanger sequencing and SNP array analysis of an EVC patient carrying a heterozygous EFCAB7 missense variant (p.Y391H)

   PMID:26748586

   Open questions at the time

   • No functional reconstitution of the Y391H variant to demonstrate pathogenicity
   • Single patient observation without segregation in multiple families
   • Effect of the variant on EFCAB7-EVC2 binding not tested
3. 2018 Low

   A second EFCAB7 missense mutation was shown to alter expression levels and interactions among EvC complex components, reinforcing EFCAB7's role in complex stabilization.

   Evidence Mutation analysis and protein interaction/expression studies in patient-derived material

   PMID:29845660

   Open questions at the time

   • Limited mechanistic detail; no cell-biological or in vivo functional assays reported
   • Single study with patient-derived samples only
4. 2023 Medium

   Two advances solidified EFCAB7's role: (1) homozygous loss-of-function frameshift deletions in EFCAB7 were shown to cause autosomal recessive postaxial polydactyly across multiple families, confirming EFCAB7 as an essential Hedgehog regulator for limb patterning; (2) post-translational modifications (SUMOylation enhancing and monoubiquitination reducing EVC-EVC2 EvC zone targeting) were mapped, and a second EFCAB7-binding motif in EVC2 was identified.

   Evidence Whole exome and Sanger sequencing with segregation in four consanguineous families; AP-MS interactomics, SUMO/ubiquitin modification assays, confocal microscopy, domain mapping

   PMID:37576597 PMID:37684519

   Open questions at the time

   • Functional consequence of the second EFCAB7-binding motif versus the first not dissected independently
   • Whether SUMOylation directly modulates EFCAB7-EVC2 affinity or acts indirectly remains unclear
   • No rescue of polydactyly phenotype with EFCAB7 re-expression in patient cells
5. 2024 Medium

   Mouse knockout studies established that EFCAB7 facilitates Smoothened-dependent Shh signaling in vivo: Efcab7-null embryos are hypersensitive to Smo antagonists and resistant to a Smo agonist, placing EFCAB7 genetically downstream of or at the level of Smoothened.

   Evidence CRISPR/Cas9 Efcab7 knockout mice challenged with vismodegib, alcohol (Smo antagonists) and SAG (Smo agonist) during gastrulation, with fetal morphological phenotyping

   PMID:39366525

   Open questions at the time

   • Molecular mechanism by which EFCAB7 promotes Smo-dependent signaling (e.g., whether it affects Smo ciliary trafficking) not determined
   • Craniofacial phenotype penetrance and variability in unstressed Efcab7 KO mice not fully characterized
6. 2024 Medium

   An unexpected non-ciliary role emerged: EFCAB7 directly interacts with PARK7/DJ-1 in hepatocellular carcinoma cells, and this axis promotes tumor proliferation and metastasis, revealing a context-dependent oncogenic function.

   Evidence Mass spectrometry identification, reciprocal Co-IP, siRNA knockdown with proliferation/metastasis assays, PARK7 rescue overexpression in HCC cell lines and xenografts

   PMID:39276379

   Open questions at the time

   • Whether the EFCAB7-PARK7 interaction occurs through EFCAB7's EF-hand domains or a distinct interface is unknown
   • Relevance beyond HCC and relationship to ciliary Hedgehog function not explored
   • Single-lab finding not yet independently replicated
7. 2025 High

   In vivo consequences of EFCAB7 loss on cardiac development were defined: a splicing variant causes impaired ciliogenesis, disrupted Shh-Gli activity, and Tetralogy of Fallot-like heart defects in a mouse knockin model, tracing the mechanism from EFCAB7 loss through reduced Gli binding at cardiac gene promoters to downregulation of Myh6, Zfpm1, and Nkx2-5.

   Evidence Mouse knockin model, splicing assays, CUT&Tag for Gli binding, bulk RNA-seq of embryonic hearts, cardiac phenotyping

   PMID:39894222

   Open questions at the time

   • Whether EFCAB7 loss affects ciliogenesis cell-autonomously or via secondary paracrine Hh signaling deficits not resolved
   • Human patient validation of the splicing variant limited to sequencing without functional studies in human cells
8. 2025 Medium

   Male fertility is unaffected in Efcab7 knockout mice, demonstrating that EFCAB7 is dispensable for spermatogenesis and sperm motility despite primary cilia/flagella sharing structural components.

   Evidence CRISPR/Cas9 knockout mice with mating tests, testis/epididymis histology, sperm motility analysis

   PMID:41194443

   Open questions at the time

   • Potential redundancy with other EF-hand proteins in sperm flagella not tested
   • Female fertility not assessed

• Key unresolved questions include the structural basis of EFCAB7-EVC2 interaction, whether EFCAB7's EF-hand domains bind calcium and how calcium might regulate EvC complex assembly, and the mechanism by which EFCAB7 engages PARK7 in non-ciliary contexts.
• No crystal or cryo-EM structure of the EFCAB7-containing complex
• Calcium binding and its functional significance for EFCAB7 never demonstrated
• Relationship between ciliary and oncogenic functions of EFCAB7 unexplored