DNAAF11

DNAAF11/LRRC6 is a cytoplasmic dynein axonemal assembly factor required for the pre-assembly and ciliary delivery of outer and inner dynein arm complexes that power motile cilia and sperm flagella (PMID:23122589, PMID:27353389). It operates within a cytoplasmic interactome, binding ZMYND10 through its CS domain (an interaction abolished by PCD-causing mutations) and associating with Reptin/RUVBL2, CCDC40, and SPAG1; loss of these contacts collapses dynein arm assembly (PMID:23891469, PMID:23858445, PMID:38934611). Mechanistically, LRRC6 acts downstream of initial dynein arm subunit assembly: in its absence the IC2–IC1 interaction still forms but outer dynein arm proteins (DNAH5, DNAH9, IC2) accumulate in the cytoplasm and fail to reach the axoneme, leaving 9+2 cilia structurally intact but immotile (PMID:27353389). Independently, LRRC6 promotes importin-α-dependent nuclear translocation of FOXJ1, sustaining transcription of the broader cilia gene program; its own expression is itself FOXJ1-dependent during ciliogenesis (PMID:23527195, PMID:37328841). Loss-of-function mutations in LRRC6 cause primary ciliary dyskinesia with absent dynein arms and male infertility, a role conserved to the Drosophila ortholog TilB (PMID:23122589, PMID:20215474, PMID:33403504).

1. 2010 High

   Established that this gene family encodes a cytoplasmic factor specifically required for axonemal dynein arm assembly rather than for ciliary structure or transport machinery generally.

   Evidence Deficiency mapping, genomic rescue transgene, tagged localization and axoneme TEM of the Drosophila ortholog TilB

   PMID:20215474

   Open questions at the time

   • Did not identify mammalian protein partners
   • Mechanism of how a cytoplasmic protein supports axonemal dynein assembly unresolved
2. 2012 High

   Defined LRRC6 as a human PCD gene whose loss removes both inner and outer dynein arms, framing it as an assembly factor acting on dynein arms collectively.

   Evidence Homozygosity mapping, sequencing, TEM, and immunolocalization in patient airway epithelial cells

   PMID:23122589

   Open questions at the time

   • Did not distinguish assembly from transport defect
   • No molecular partners identified
3. 2013 High

   Placed LRRC6 in a defined cytoplasmic assembly network by mapping a direct ZMYND10 interaction and a direct Reptin/RUVBL2 interaction, both required for dynein arm formation.

   Evidence Domain-mapping reciprocal Co-IP with PCD-mutant disruption, centriole-marker colocalization, and zebrafish/Xenopus genetic models

   PMID:23858445 PMID:23891469

   Open questions at the time

   • Stoichiometry and assembly order of the complex unknown
   • How the complex chaperones dynein subunits not resolved
4. 2013 High

   Linked LRRC6 to the ciliogenesis transcriptional program and showed knockdown mislocalizes dynein arm proteins to the cytoplasm with loss of beat frequency.

   Evidence shRNA knockdown in human airway epithelium, FOXJ1-dependent expression analysis, immunofluorescence, cilia beat frequency

   PMID:23527195

   Open questions at the time

   • FOXJ1 dependence shown only at expression level, not mechanism
   • Did not separate transport from assembly
5. 2016 High

   Resolved the step at which LRRC6 acts, showing initial ODA subunit assembly (IC2–IC1) is intact but cytoplasm-to-cilia transport of assembled dynein fails.

   Evidence Lrrc6 knockout mouse with immunofluorescence, Co-IP of IC2–IC1, and TEM

   PMID:27353389

   Open questions at the time

   • Molecular machinery linking pre-assembly to transport not defined
   • Inner dynein arm transport not examined in equivalent detail
6. 2021 Medium

   Confirmed in human sperm that a truncating LRRC6 variant abolishes protein and dynein arm marker expression, extending the assembly role to flagella and infertility.

   Evidence Western blot, immunofluorescence, TEM on patient spermatozoa carrying p.W250*

   PMID:33403504

   Open questions at the time

   • Single family
   • Whether defect is reduced expression versus mislocalization not distinguished
7. 2023 Medium

   Revealed a second, transcriptional axis: LRRC6 drives importin-α-dependent nuclear entry of FOXJ1, so its loss reduces transcription of the full motile-cilia gene set.

   Evidence Lrrc6 KO mice, proteomics/transcriptomics, FOXJ1 immunofluorescence, importin-α inhibitor INI-43, basal cell organoids

   PMID:37328841

   Open questions at the time

   • Direct LRRC6–FOXJ1 or LRRC6–importin-α binding not demonstrated
   • Relationship between cytoplasmic assembly role and nuclear role unclear
   • Single lab
8. 2024 Medium

   Extended the cytoplasmic interactome to CCDC40 and SPAG1 alongside ZMYND10 in patient material, consolidating LRRC6 as a hub for dynein arm pre-assembly.

   Evidence Tandem mass tagging proteomics on patient spermatozoa with western blot, immunostaining, and TEM

   PMID:38934611

   Open questions at the time

   • Interactome inferred from patient material, not reconstituted
   • Direct versus indirect associations not all distinguished

• How LRRC6 mechanistically couples cytoplasmic dynein pre-assembly to ciliary transport, and how this is reconciled with its FOXJ1 nuclear-translocation role, remains unresolved.
• No structural model of the assembly complex
• Direct LRRC6–importin-α–FOXJ1 binding unproven
• Substrate handoff mechanism to transport machinery undefined