DNAH8 (dynein axonemal heavy chain 8; mouse Dnahc8) is a gamma-type outer dynein arm (ODA) heavy chain, the sperm-specific paralog of DNAH5. It is a 4490-residue motor protein with an N-terminal tail that assembles with the other ODA subunits, a ring of six AAA+ domains (AAA1 carries the hydrolytic ATP site), and a coiled-coil stalk ending in a microtubule-binding domain, and it generates force towards microtubule minus ends. DNAH8 is expressed in germ cells from early spermatocytes to late spermatids, is detected in the cytoplasm of spermatocytes during dynein preassembly, and in mature sperm lies along the flagellar axoneme, concentrated in the principal piece. In human sperm the ODA heavy chains are DNAH8 (gamma) and DNAH17 (beta), whereas respiratory cilia use DNAH5, DNAH9 and DNAH11 and lack DNAH8. DNAH8 and DNAH17 depend on each other for stable incorporation into the sperm axoneme. Bi-allelic loss-of-function variants cause male infertility with asthenoteratozoospermia and multiple morphological abnormalities of the sperm flagella (MMAF; spermatogenic failure 46) without respiratory disease, and Dnah8-knockout male mice are sterile with MMAF; ICSI can achieve pregnancy. Mouse t-haplotype alleles of Dnahc8 contribute to the curlicue sperm-tail phenotype. Knockout and cancer studies also link DNAH8 to androgen signalling (an androgen-regulated gene in prostate cancer, and reduced fetal testosterone in knockout mice), but how an axonemal motor would do this is unexplained.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003777 microtubule motor activity | IMP PMID:32619401 Bi-allelic DNAH8 Variants Lead to Multiple Morphological Abn... | ACCEPT | Summary: Microtubule motor activity based on patient and Dnah8-knockout phenotypes (loss of DNAH8 gives MMAF and immotile sperm). Reason: DNAH8 is a gamma-type outer dynein arm heavy chain with a full AAA+ motor head and stalk. The loss-of-function data are indirect evidence for motor activity (they mainly show a flagellar assembly defect), but the activity itself is well founded on family biology and is the core molecular function. The more specific child term minus-end-directed microtubule motor activity is also annotated. Supporting Evidence: PMID:32619401 DNAH8 is essential for sperm flagellar formation and that bi-allelic deleterious DNAH8 variants lead to male infertility with MMAF file:human/DNAH8/DNAH8-uniprot.txt Force generating protein component of the outer dynein arms |
| GO:0003777 microtubule motor activity | NAS PMID:9373155 Identification of dynein heavy chain genes expressed in huma... | ACCEPT | Summary: Early testis cDNA survey of dynein heavy chain sequences, classifying the human fragments as outer- or inner-arm axonemal dyneins. Reason: Consistent with the domain architecture and with the experimental annotations. Retained as a general statement of the core activity. Supporting Evidence: PMID:9373155 axonemal dyneins are essential for motility of cilia and flagella file:human/DNAH8/DNAH8-uniprot.txt Force generating protein component of the outer dynein arms |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro mapping from the dynein heavy chain AAA domain. UniProt annotates an ATP-binding P-loop in AAA1. Reason: Correct (the AAA1 site hydrolyses ATP to power the motor) but uninformative relative to the motor activity terms. Supporting Evidence: file:human/DNAH8/DNAH8-uniprot.txt FT BINDING 1846..1853 |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt subcellular-location mapping to cytoplasm. Reason: Axonemal dynein arms are preassembled in the cytoplasm before transport into the flagellum, and mouse Dnahc8 is detected in the cytoplasm of primary spermatocytes. This is a transient pre-assembly location, not where the protein functions. Supporting Evidence: file:human/DNAH8/DNAH8-uniprot.txt Also detected in the cytoplasm of primary spermatocytes |
| GO:0005737 cytoplasm | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Transferred from mouse Dnahc8 (Q91XQ0), which is detected in the cytoplasm of primary spermatocytes. Reason: Plausible location during cytoplasmic preassembly of outer arm dyneins; non-core relative to the sperm axoneme. Supporting Evidence: file:human/DNAH8/DNAH8-uniprot.txt Also detected in the cytoplasm of primary spermatocytes |
| GO:0005858 axonemal dynein complex | NAS PMID:9373155 Identification of dynein heavy chain genes expressed in huma... | ACCEPT | Summary: Axonemal dynein complex, from the early testis dynein heavy chain survey. Reason: Correct; DNAH8 is a heavy chain of the sperm outer dynein arm, a type of axonemal dynein complex. The more specific outer dynein arm term is also annotated. Supporting Evidence: PMID:9373155 axonemal dyneins are essential for motility of cilia and flagella PMID:31178125 Ξ³-type: DNAH5 and DNAH8 and Ξ²-type: DNAH9, DNAH11, and DNAH17 |
| GO:0005930 axoneme | IDA PMID:31178125 Mutations in DNAH17, Encoding a Sperm-Specific Axonemal Oute... | ACCEPT | Summary: DNAH8 immunostaining colocalizes with alpha-tubulin along the axoneme of control human sperm. Reason: Direct localization evidence in human sperm. Supporting Evidence: PMID:31178125 We show that DNAH17 and DNAH8, but not DNAH5, DNAH9, or DNAH11, colocalize with Ξ±-tubulin along the sperm axoneme, whereas the reverse picture is observed in respiratory cilia, thus explaining the phenotype restricted to sperm cells. |
| GO:0005930 axoneme | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA prediction of axoneme location. Reason: Agrees with the experimental IDA from PMID:31178125. Supporting Evidence: PMID:31178125 We show that DNAH17 and DNAH8, but not DNAH5, DNAH9, or DNAH11, colocalize with Ξ±-tubulin along the sperm axoneme, whereas the reverse picture is observed in respiratory cilia, thus explaining the phenotype restricted to sperm cells. |
| GO:0005930 axoneme | IMP PMID:32619401 Bi-allelic DNAH8 Variants Lead to Multiple Morphological Abn... | ACCEPT | Summary: Loss of DNAH8 staining from the flagella of men with bi-allelic DNAH8 variants. Reason: Supports axonemal localization (absence of the normal flagellar signal in mutants); consistent with the IDA. Supporting Evidence: PMID:32619401 Immunofluorescence assays performed on the spermatozoa from men harboring bi-allelic DNAH8 variants revealed the absent or markedly reduced staining of DNAH8 and its associated protein DNAH17. |
| GO:0007018 microtubule-based movement | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro mapping from the dynein heavy chain family. Reason: Outer arm dynein heavy chains generate microtubule sliding in the axoneme. Accurate, though general; the specific process is flagellated sperm motility. Supporting Evidence: PMID:31178125 the outer dynein arms (ODAs), through ATPase activity of their heavy chains (HCs), play a major role for cilia and flagella beating |
| GO:0008569 minus-end-directed microtubule motor activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBD at the root dynein heavy chain node PTN000743491 (PTHR10676), seeded by experimentally characterized cytoplasmic and axonemal dyneins. Reason: All dynein heavy chains with an intact AAA1 site and microtubule-binding stalk are minus-end-directed motors; DNAH8 retains both and there is no evidence of loss of this activity in the gamma ODA heavy chain lineage. This is the most specific correct molecular function for DNAH8. Supporting Evidence: file:human/DNAH8/DNAH8-uniprot.txt Produces force towards the minus ends of microtubules PMID:31178125 the outer dynein arms (ODAs), through ATPase activity of their heavy chains (HCs), play a major role for cilia and flagella beating |
| GO:0008569 minus-end-directed microtubule motor activity | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro mapping (IPR004273, dynein heavy chain). Reason: Same conclusion as the IBA. Supporting Evidence: file:human/DNAH8/DNAH8-uniprot.txt Produces force towards the minus ends of microtubules |
| GO:0030286 dynein complex | IEA GO_REF:0000002 | MODIFY | Summary: InterPro mapping to the generic dynein complex. Reason: Correct but too general. DNAH8 is a heavy chain of the sperm outer dynein arm (with DNAH17), so the outer dynein arm term is the appropriate complex. Proposed replacements: outer dynein arm Supporting Evidence: PMID:31178125 We show that DNAH17 and DNAH8, but not DNAH5, DNAH9, or DNAH11, colocalize with Ξ±-tubulin along the sperm axoneme, whereas the reverse picture is observed in respiratory cilia, thus explaining the phenotype restricted to sperm cells. PMID:32619401 Immunofluorescence assays performed on the spermatozoa from men harboring bi-allelic DNAH8 variants revealed the absent or markedly reduced staining of DNAH8 and its associated protein DNAH17. |
| GO:0036126 sperm flagellum | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBD at node PTN008503977, seeded by mouse Dnahc8 (MGI:107714) and human DNAH8 itself. Reason: The sperm flagellum is the principal site of DNAH8 function. Human DNAH8 appears among the sources because it has its own experimental annotation, which is expected for a correctly placed node. Supporting Evidence: PMID:31178125 We show that DNAH17 and DNAH8, but not DNAH5, DNAH9, or DNAH11, colocalize with Ξ±-tubulin along the sperm axoneme, whereas the reverse picture is observed in respiratory cilia, thus explaining the phenotype restricted to sperm cells. PMID:16054618 Interestingly, DNAHC8 is confined to the principal piece of the sperm tail. |
| GO:0036126 sperm flagellum | IDA PMID:31178125 Mutations in DNAH17, Encoding a Sperm-Specific Axonemal Oute... | ACCEPT | Summary: Immunostaining of DNAH8 along the flagella of control human sperm. Reason: Direct evidence; DNAH8 is present in sperm axonemes but not in respiratory cilia. Supporting Evidence: PMID:31178125 We show that DNAH17 and DNAH8, but not DNAH5, DNAH9, or DNAH11, colocalize with Ξ±-tubulin along the sperm axoneme, whereas the reverse picture is observed in respiratory cilia, thus explaining the phenotype restricted to sperm cells. |
| GO:0036126 sperm flagellum | IMP PMID:32619401 Bi-allelic DNAH8 Variants Lead to Multiple Morphological Abn... | ACCEPT | Summary: Absence or marked reduction of DNAH8 flagellar staining in men with bi-allelic DNAH8 variants. Reason: Consistent with the IDA annotation. Supporting Evidence: PMID:32619401 Immunofluorescence assays performed on the spermatozoa from men harboring bi-allelic DNAH8 variants revealed the absent or markedly reduced staining of DNAH8 and its associated protein DNAH17. |
| GO:0036157 outer dynein arm | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBD at node PTN002472868 (gamma-type ODA heavy chains), seeded by DNAH5 (Q8TE73) and mouse Dnah5. Reason: DNAH8 is the sperm-specific paralog of the gamma ODA heavy chain DNAH5 and occupies the gamma position of the sperm ODA together with the beta chain DNAH17. Loss of DNAH17 removes DNAH8 and other ODA subunits from sperm, and vice versa, which is the signature of co-assembly in one complex. Supporting Evidence: PMID:31178125 Ξ³-type: DNAH5 and DNAH8 and Ξ²-type: DNAH9, DNAH11, and DNAH17 PMID:31178125 these analyses indicated the absence of DNAH17 and DNAH8, whereas DNAH2 and DNALI, two inner dynein arm components, were present PMID:32619401 Immunofluorescence assays performed on the spermatozoa from men harboring bi-allelic DNAH8 variants revealed the absent or markedly reduced staining of DNAH8 and its associated protein DNAH17. |
| GO:0036158 outer dynein arm assembly | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: PAINT IBD at node PTN002472868, seeded by DNAH5. Reason: As a core structural subunit, DNAH8 contributes to building the outer arm: in DNAH8-mutant sperm DNAH17 is lost, and in DNAH17-mutant sperm DNAH8 is lost. This is participation by being a structural component rather than an assembly factor, so it is kept but not treated as core. Supporting Evidence: PMID:36308074 In addition, expression of DNAH17, a DNAH8-associated protein, was significantly reduced in the sperm flagella of the patients with the DNAH8 mutation. PMID:41549443 In addition to DNAH17, several proteins associated with ODA assembly, including ODAD4, ODAD2, DNAI1, and DNAH8, were among the top 10 downregulated proteins in DNAH17-mutant patients |
| GO:0045505 dynein intermediate chain binding | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: PAINT IBD at the root dynein heavy chain node PTN000743491, seeded by Dictyostelium cytoplasmic dynein. Reason: The heavy chain tail of an outer arm dynein binds the ODA intermediate chains (DNAI1/DNAI2 type), so this activity is plausible for DNAH8 by conservation of the tail, and DNAI1 is co-depleted with the heavy chains in ODA-deficient sperm. No direct binding data for DNAH8 exist, and binding is a structural feature rather than the core motor function. Supporting Evidence: PMID:41549443 In addition to DNAH17, several proteins associated with ODA assembly, including ODAD4, ODAD2, DNAI1, and DNAH8, were among the top 10 downregulated proteins in DNAH17-mutant patients |
| GO:0045505 dynein intermediate chain binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro mapping (IPR026983). Reason: As for the IBA. Supporting Evidence: PMID:41549443 In addition to DNAH17, several proteins associated with ODA assembly, including ODAD4, ODAD2, DNAI1, and DNAH8, were among the top 10 downregulated proteins in DNAH17-mutant patients |
| GO:0051959 dynein light intermediate chain binding | IBA GO_REF:0000033 | REMOVE | Summary: PAINT IBD at the root dynein heavy chain node PTN000743491, seeded only by cytoplasmic dynein 1 heavy chains (human DYNC1H1 Q14204, mouse Dync1h1 MGI:103147, rat RGD:71042). Reason: Light intermediate chains (DYNC1LI1/2) are subunits of cytoplasmic dynein 1. The outer dynein arm contains heavy, intermediate and light chains but no light intermediate chain, and the axonemal light intermediate chain DNALI1 is an inner arm subunit that is retained in DNAH17/DNAH8-deficient sperm. The node placement at the root of the family over-propagates a cytoplasmic-dynein-specific interaction to the outer arm heavy chain lineage. Propagation Review Root cause: PROPAGATION BAD Failure modes: COMPARTMENT OR COMPLEX MISMATCH ROLE CONFLATION Sources checked: PANTHER:PTN000743491 Β· PTN000743491 SUPPORTS SOURCE BUT NOT TARGET IBD at the root of the dynein heavy chain family, seeded only by cytoplasmic dynein 1 heavy chains (DYNC1H1 and its mouse and rat orthologs), whose light intermediate chains are cytoplasmic-dynein-specific subunits. Outer arm heavy chains descend from this node but their complex has no light intermediate chain. Supporting Evidence: PMID:31178125 these analyses indicated the absence of DNAH17 and DNAH8, whereas DNAH2 and DNALI, two inner dynein arm components, were present file:human/DNAH8/DNAH8-uniprot.txt Part of the ciliary outer dynein arms (ODAs), at least consisting of dynein axonemal heavy chains, light chains and intermediate chains |
| GO:0051959 dynein light intermediate chain binding | IEA GO_REF:0000002 | REMOVE | Summary: InterPro mapping (IPR026983, dynein heavy chain family). Reason: Same argument as for the IBA: no light intermediate chain is part of the outer dynein arm. Supporting Evidence: PMID:31178125 these analyses indicated the absence of DNAH17 and DNAH8, whereas DNAH2 and DNALI, two inner dynein arm components, were present file:human/DNAH8/DNAH8-uniprot.txt Part of the ciliary outer dynein arms (ODAs), at least consisting of dynein axonemal heavy chains, light chains and intermediate chains |
| GO:0060285 cilium-dependent cell motility | NAS PMID:9373155 Identification of dynein heavy chain genes expressed in huma... | MODIFY | Summary: Cilium-dependent cell motility, from the early testis dynein heavy chain survey. Reason: DNAH8 supplies the force-generating heavy-chain motor component of the sperm outer dynein arm, so it performs part of flagellar movement rather than merely marking infertility. Human localization places DNAH8 along sperm axonemes but not the examined respiratory cilia (PMID:31178125), making flagellated sperm motility the informative refinement. Human DNAH8 variants and the Dnah8-knockout mouse phenotype independently support the sperm-flagellar requirement (PMID:32619401; PMID:32681648); these phenotypes are not measurements of purified motor kinetics. A bounded current QuickGO comparison recovers the same process on mouse Dnah1 and Dnah11 with IMP records and on Dnah7a, Dnah7b and Dnah7c with electronic records. This supports the annotation convention for sperm axonemal motor subunits, not equivalent experimental proof for all comparators or an independent human assay. The original NAS source remains unchanged; the later human and mouse evidence supports the specific replacement. Proposed replacements: flagellated sperm motility Supporting Evidence: PMID:9373155 axonemal dyneins are essential for motility of cilia and flagella PMID:31178125 We show that DNAH17 and DNAH8, but not DNAH5, DNAH9, or DNAH11, colocalize with Ξ±-tubulin along the sperm axoneme, whereas the reverse picture is observed in respiratory cilia, thus explaining the phenotype restricted to sperm cells. PMID:32619401 Dnah8-knockout male mice also presented typical MMAF phenotypes and sterility. PMID:32681648 a loss-of-function mutation in DNAH8 can cause male infertility with MMAF and that DNAH8 is essential for sperm flagellar formation |
| GO:0060294 cilium movement involved in cell motility | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBD at the root node PTN000743491, seeded by many axonemal heavy chains from fly, mouse and human. Reason: DNAH8 drives beating of the sperm flagellum, which is cilium movement involved in cell motility. The more specific flagellated sperm motility is already proposed as the replacement for the GO:0060285 NAS annotation; no separate NEW row is asserted. Supporting Evidence: PMID:31178125 the outer dynein arms (ODAs), through ATPase activity of their heavy chains (HCs), play a major role for cilia and flagella beating |
| GO:0097225 sperm midpiece | IDA GO_REF:0000052 | KEEP AS NON CORE | Summary: Human Protein Atlas immunofluorescence of sperm midpiece. Reason: Outer dynein arms run through the midpiece axoneme, and patients lacking the DNAH8/DNAH17 outer arm lose ODAs from the middle piece as well as the principal and end pieces, so the signal is plausible. Mouse Dnahc8 has been described as confined to the principal piece, so this is kept as a minor location. Supporting Evidence: PMID:41549443 revealed a lack of outer dynein arms (ODAs) in the middle, principal, and end pieces of the flagella |
| GO:0097228 sperm principal piece | IDA GO_REF:0000052 | ACCEPT | Summary: Human Protein Atlas immunofluorescence of sperm principal piece. Reason: Consistent with the mouse Dnahc8 localization, which is concentrated in the principal piece. Supporting Evidence: PMID:16054618 Interestingly, DNAHC8 is confined to the principal piece of the sperm tail. file:human/DNAH8/DNAH8-uniprot.txt almost exclusive localization to the principal piece |
| GO:0097729 9+2 motile cilium | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA prediction of 9+2 motile cilium. Reason: Formally correct because the sperm flagellum is a 9+2 motile cilium, but DNAH8 is not detected in respiratory multiciliated cells; the sperm flagellum annotation is the informative one. Supporting Evidence: PMID:31178125 We show that DNAH17 and DNAH8, but not DNAH5, DNAH9, or DNAH11, colocalize with Ξ±-tubulin along the sperm axoneme, whereas the reverse picture is observed in respiratory cilia, thus explaining the phenotype restricted to sperm cells. |
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Download this section (compressed HTML)Q: Does DNAH8 form a heterodimeric outer arm with DNAH17 in every position along the sperm flagellum, or do midpiece and principal-piece ODAs differ in heavy-chain composition (the mouse protein is reported to be confined to the principal piece)?
Q: Do DNAH8 and DNAH17 assemble with the same intermediate chains, light chains and docking complex (ODAD1-4) as the respiratory DNAH5/DNAH9/DNAH11 arms, or are there sperm-specific ODA subunits?
Q: Is the reported link between DNAH8 and androgen signalling (prostate cancer AR activity, fetal testosterone in knockout mice) a direct, non-axonemal function, or a secondary effect of germ-cell or ciliary defects?
Experiment: Cryo-electron tomography with subtomogram averaging of Dnah8-/- and Dnah17-/- mouse sperm axonemes to define the position and interdependence of the two heavy chains within the outer arm.
Type: cryo-electron tomography
Experiment: Purify sperm outer arm dynein (or recombinant DNAH8 motor domain) and measure ATPase activity and microtubule gliding, to confirm minus-end-directed motor activity of the gamma chain directly.
Type: in vitro motility assay
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