DNALI1

DNALI1 is an axonemal dynein light intermediate chain that is essential for the stable assembly and function of a specific subset of inner dynein arms in cilia and sperm flagella. In Chlamydomonas, DNALI1 (p28) associates with inner dynein arm heavy chains via co-immunoprecipitation and its loss-of-function abolishes the corresponding heavy chains from axonemes, eliminating inner arm-dependent motility (PMID:7579689, PMID:7579690, PMID:12378537). In mammals, DNALI1 is required for incorporation of DNAH1 and DNAH7 into sperm flagella, interacts with cytoplasmic dynein components, and recruits the MEIG1/PACRG complex at the manchette to facilitate flagellar cargo transport during spermiogenesis; bi-allelic loss-of-function mutations in humans and knockout mice cause severe asthenozoospermia and male infertility (PMID:36792588, PMID:37083624). Under pathological conditions such as traumatic brain injury, DNALI1 overexpression inhibits autophagosome–lysosome fusion and exacerbates neuronal cell death (PMID:38348540).

1. 1995 High

   Establishing that DNALI1 (p28) is a bona fide light chain subunit of inner dynein arms resolved the composition of the non-caltractin-containing inner arm subspecies and identified the heavy chains (2′ and 2) with which it stably associates.

   Evidence Co-immunoprecipitation and biochemical fractionation of Chlamydomonas axonemes

   PMID:7579689

   Open questions at the time

   • Structural basis of p28 interaction with inner arm heavy chains unknown
   • Whether p28 has a role beyond inner arm assembly not addressed
2. 1995 High

   Demonstrating that IDA4 encodes p28 and that loss-of-function mutations eliminate the associated heavy chains from flagella established DNALI1 as required for stable inner dynein arm assembly, not merely a co-purifying factor.

   Evidence Genetic analysis and immunoblotting of three ida4 mutant alleles in Chlamydomonas

   PMID:7579690

   Open questions at the time

   • Mechanism by which p28 loss destabilizes heavy chains (chaperone vs. structural scaffold) not resolved
   • Whether other light chains can compensate unknown
3. 2002 High

   Showing that recombinant p28 could restore motility to non-motile mutants demonstrated functional sufficiency of the protein and confirmed it acts directly in inner arm-dependent flagellar beating.

   Evidence Electroporation of recombinant p28 into Chlamydomonas ida4oda6 double mutant with motility rescue assay

   PMID:12378537

   Open questions at the time

   • How p28 is targeted and assembled into the axoneme in vivo remained unclear
   • Rescue was partial (~30%), leaving open whether co-factors are limiting
4. 2006 Medium

   Identification of cytoplasmic dynein heavy chain 1 as a mammalian DNALI1 interactor, together with localization to sperm flagella and tracheal cilia, extended DNALI1 function from Chlamydomonas to mammals and suggested a cytoplasmic transport role.

   Evidence Yeast two-hybrid screen, co-immunoprecipitation, and immunofluorescence in mouse testes and trachea

   PMID:16496424

   Open questions at the time

   • Interaction with cytoplasmic dynein heavy chain identified by Y2H and single co-IP; reciprocal validation in endogenous conditions not shown
   • Functional significance of the cytoplasmic dynein interaction not tested by loss-of-function
5. 2023 High

   Human genetic and mouse knockout studies established that DNALI1 is specifically required for the assembly of the DNAH1/DNAH7-containing inner dynein arm subspecies in mammalian sperm and that its loss causes male infertility through disrupted flagellar ultrastructure and impaired transport of fibrous sheath components.

   Evidence Bi-allelic human mutations, Dnali1−/− mouse model, immunoprecipitation, TEM, immunofluorescence

   PMID:36792588

   Open questions at the time

   • Whether DNALI1 loss affects motile cilia function in human airways not assessed
   • Direct mechanism distinguishing inner arm assembly failure from fibrous sheath transport defect unclear
6. 2023 High

   Discovery that DNALI1 recruits and stabilizes the MEIG1/PACRG complex at the manchette placed DNALI1 upstream in an intramanchette transport pathway required for flagellogenesis, distinct from its structural role within axonemal dynein arms.

   Evidence Co-immunoprecipitation, pull-down assays, male germ cell-specific conditional knockout in mice, immunofluorescence of elongating spermatids

   PMID:37083624

   Open questions at the time

   • Whether DNALI1's manchette role is separable from its axonemal dynein role not genetically dissected
   • Cargo identity transported via the MEIG1/PACRG/DNALI1 pathway not fully catalogued
7. 2024 Medium

   Revealing that DNALI1 overexpression inhibits autophagosome–lysosome fusion uncovered an unexpected non-ciliary function, linking DNALI1 to autophagy regulation in pathological neurodegeneration.

   Evidence Overexpression and knockdown in vitro, autophagic flux assays, chronic traumatic encephalopathy mouse model

   PMID:38348540

   Open questions at the time

   • Mechanism by which DNALI1 blocks autophagosome–lysosome fusion (direct vs. indirect) not identified
   • Relevance of this function under physiological (non-injury) conditions unknown
   • Single-lab finding; independent replication pending

• The structural basis of DNALI1 interaction with its inner dynein arm heavy chain partners, whether its manchette and axonemal functions are mechanistically separable, and whether its autophagy-inhibitory activity reflects a physiological role remain unresolved.
• No high-resolution structural data for DNALI1 in complex with dynein heavy chains
• Separation-of-function alleles distinguishing manchette transport from axonemal assembly roles not available
• Physiological relevance of DNALI1 in autophagy outside injury models untested