EFCAB7

EFCAB7 is a primary cilium protein that functions as a positive regulator of Hedgehog signaling by anchoring the EVC-EVC2 heterodimer within a specialized signaling microdomain at the ciliary base (the EvC zone) (PMID:24582806). Together with IQCE, EFCAB7 forms a complex that directly binds a C-terminal disordered region of EVC2 — the same region deleted in Weyers syndrome — and its depletion mislocalizes EVC-EVC2 within cilia and impairs activation of the GLI2 transcription factor (PMID:24582806). EvC zone targeting depends on two distinct EFCAB7-binding motifs in the EVC2 Weyers-deleted peptide, and SUMOylation of the EVC-EVC2 cytosolic tails enhances complex accumulation at this site, consistent with modulation of binding to the EFCAB7-IQCE complex (PMID:37576597). In vivo, EFCAB7 acts upstream as a positive regulator of Smoothened activity: full deletion in mice sensitizes fetuses to malformations induced by Smo antagonism and protects against Smo agonism (PMID:39366525), and a disease-associated splicing variant disrupts ciliogenesis, downregulates Gli target genes (Myh6, Zfpm1, Nkx2-5), and produces Tetralogy of Fallot-like cardiac defects (PMID:39894222). EFCAB7 loss is nonetheless dispensable for male fertility and sperm motility when ablated alone (PMID:41194443).

1. 2014 High

   Established how EVC-EVC2 is retained at the ciliary base and linked EFCAB7 to a defined Hedgehog signaling output, answering how a Weyers-syndrome–associated EVC2 region is functionally read out.

   Evidence Co-IP, ciliary immunofluorescence, EFCAB7 siRNA knockdown with GLI2 activation assay, and binding-domain mapping in mammalian cells

   PMID:24582806

   Open questions at the time

   • Does not resolve the structural basis of the EFCAB7-IQCE-EVC2 complex
   • Stoichiometry and assembly order at the EvC zone not defined
2. 2023 Medium

   Refined the molecular interface and regulation, showing EvC zone targeting requires two separate EFCAB7-binding motifs and is enhanced by SUMOylation of the EVC-EVC2 tails.

   Evidence Endogenous EVC interactome by Co-IP/MS in Evc-null vs control cells, SUMOylation assays, ciliary localization, and EVC2 motif mapping (single lab)

   PMID:37576597

   Open questions at the time

   • Mechanism by which SUMO3 increases EFCAB7-IQCE binding not directly demonstrated
   • SUMO ligase/site responsible not identified
   • Single lab
3. 2024 Medium

   Placed EFCAB7 epistatically within the Shh pathway in vivo as a positive regulator of Smoothened activity, distinguishing its role from upstream/downstream nodes.

   Evidence CRISPR Efcab7-knockout mice challenged with Smo agonist (SAG), Smo antagonist (vismodegib), or alcohol at gastrulation, with fetal phenotypic scoring

   PMID:39366525

   Open questions at the time

   • Does not define the molecular step at which EFCAB7 modulates Smo
   • Single lab
   • Epistasis inferred pharmacologically rather than biochemically
4. 2025 Medium

   Connected an EFCAB7 loss-of-function variant to a human-relevant developmental disease mechanism, tying ciliogenesis and Gli-target transcription to cardiac morphogenesis.

   Evidence Splicing assays, variant knock-in mouse, ciliogenesis assay, CUT&Tag for Gli binding, and bulk RNA-seq of embryonic hearts

   PMID:39894222

   Open questions at the time

   • Direct effect of EFCAB7 on ciliogenesis machinery not mechanistically resolved
   • Single lab
   • Causality between Gli-target downregulation and specific cardiac defects not fully dissected
5. 2024 Low

   Reported a non-ciliary context in which EFCAB7 interacts with PARK7 and acts upstream of it to support tumor cell proliferation and metastasis.

   Evidence Mass spectrometry and Co-IP in hepatocellular carcinoma cells with siRNA knockdown and PARK7 rescue overexpression (in vitro)

   PMID:39276379

   Open questions at the time

   • Single Co-IP and MS from one lab, no reciprocal or structural validation
   • Restricted to one cancer cell line context
   • Relationship to ciliary function unknown
6. 2025 Medium

   Defined the boundary of EFCAB7 requirement in vivo, showing it is dispensable for male reproduction when ablated alone.

   Evidence CRISPR/Cas9 knockout mice with mating tests, sperm motility analysis, and histological phenotyping

   PMID:41194443

   Open questions at the time

   • Possible redundancy with paralogs not tested
   • Female reproductive phenotype not addressed

• The structural architecture of the EFCAB7-IQCE-EVC2 assembly and the precise molecular step at which EFCAB7 enables Smoothened-to-GLI2 signal transduction remain undefined.
• No structure of the EFCAB7-IQCE-EVC2 complex
• Direct biochemical link between complex anchoring and Smo activation unresolved
• PARK7 interaction not integrated with ciliary role