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Inheritance

1

Autosomal recessive HP:0000007

Disease requires biallelic DNAH1 variants. Reported genotypes include homozygosity in consanguineous North African families, a recurrent East Asian homozygous frameshift, and compound heterozygosity; parents and unaffected siblings are heterozygous carriers.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:27573432 SUPPORT Human Clinical

"The parents and the sibling of proband 1 were all identified as heterozygous carriers."

Heterozygous unaffected parents and sibling establish recessive inheritance.

◈

Mechanistic Hypotheses

1

DNAH1 is required by the sperm flagellum but largely dispensable in motile cilia, which is why SPGF18 is not primary ciliary dyskinesia

flagellum_specific_dynein_requirement EMERGING

Evidence balance 1 support 2 refute

DNAH1 encodes an axonemal dynein heavy chain and is expressed in ciliated cells beyond the testis, so biallelic loss would be expected to produce primary ciliary dyskinesia - chronic sinopulmonary disease, otitis media, possible situs inversus. It does not. In the original 20-subject cohort, infertility was the only PCD feature observed. The proposed explanation is that DNAH1's contribution to the motile cilium is redundant, covered by other inner-arm dynein heavy chains, while the sperm flagellum has no such redundancy. The evidence is an absence of reported respiratory disease rather than a systematic ciliary assessment, and the cohorts are small, so this is recorded as EMERGING. Distinguishing genuine tissue-specific redundancy from mild or unascertained ciliary disease would require nasal nitric oxide measurement or ciliary beat analysis in genotyped men, which no published study reports. There is also direct counter-evidence. Two sisters with clinically diagnosed PCD carry a homozygous DNAH1 missense variant segregating completely with the phenotype, and OMIM recognises a separate DNAH1 ciliary dyskinesia entity (CILD37) on that basis. That does not overturn the tissue-specific-redundancy reading - the alleles differ and the SPGF18 cohorts genuinely lack ciliary disease - but it does mean the redundancy cannot be a property of losing DNAH1 as such, and that a DNAH1 finding cannot be used to rule ciliary disease out.

Show evidence (3 references)

PMID:24360805 SUPPORT Human Clinical

"Although DNAH1 is also expressed in other ciliated cells, infertility was the only symptom of primary ciliary dyskinesia observed in affected subjects, suggesting that DNAH1 function in cilium is not as critical as in sperm flagellum."

The authors' own statement of both the observation and the proposed tissue-specific-redundancy explanation.

PMID:25927852 REFUTE Human Clinical

"A novel homozygous missense aberration (p.Lys1154Gln) was identified in both sisters in the DNAH1 gene that segregated completely with the disease phenotype."

Direct counter-evidence. A homozygous DNAH1 variant segregating with clinically diagnosed PCD means ciliary dysfunction from DNAH1 variation is possible, so redundancy cannot be a property of DNAH1 loss as such.

PMID:25927852 REFUTE Human Clinical

"Molecular variation in DNAH1 may play a role in PCD and its potential contribution should be considered in patients where all known genes are excluded."

The authors' own conclusion that DNAH1 should be considered in PCD, which is incompatible with treating a DNAH1 finding as excluding ciliary disease.

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Discussions and Knowledge Gaps

1

Does the Dnah1 ferf1 mouse model the human MMAF flagellar phenotype at all, or only the downstream infertility - and is the divergence a species difference or an allele-class difference?

HUMAN MODEL MISMATCH dnah1_mouse_flagellar_mismatch

Attached to

pathophysiology#Multiple Morphological Abnormalities of the Sperm Flagella animal_models#Mouse

The Dnah1 ferf1 allele produces infertility with apparently normal sperm morphology and a zona-penetration block, whereas human biallelic DNAH1 loss produces gross flagellar malformation with inner dynein arm loss. The model therefore reproduces the clinical endpoint by a route that may not be the human one. Because ferf1 is a missense allele and the best-characterised human genotypes are protein-null, the divergence could be allele class rather than species - a distinction that determines whether the model is usable for studying human flagellar morphogenesis. The missense-versus-null framing is itself not decisive: a separate constitutive Dnah1 knockout is described with reduced motility and no TEM-detectable axonemal defect, which is also unlike the human ultrastructural phenotype, so a null allele does not obviously rescue the comparison. That knockout is not cited here because its primary description was not verified in this round. The ferf1 source paper makes the general point, noting that DNAH1 mutations across mouse and human give a diversity of phenotypes with both subtle and considerable differences.

Show evidence (1 reference)

PMID:30734403 SUPPORT Model Organism

"the various mutations affecting the DNAH1 protein in both mouse and human produce a diversity of phenotypes with both subtle and considerable differences"

The authors themselves flag the cross-species and cross-allele phenotypic divergence that this gap records.

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Pathophysiology

3

Loss of the DNAH1 Inner-Arm Dynein Heavy Chain

DNAH1 encodes an inner dynein arm heavy chain expressed in testis. Both truncating and missense routes converge on absence or dysfunction of the protein in sperm: in a donor-splice-site case neither transcript nor protein was detectable, and in the recurrent East Asian frameshift the protein was undetectable by Western blot and immunofluorescence even though DNAH1 mRNA was still present in spermatozoa - so loss of protein, not loss of transcript, is the common endpoint.

Downstream

Axonemal Disorganization and Inner Dynein Arm Loss Absence of the heavy chain removes the inner dynein arms it forms and destabilizes axonemal architecture.

Show evidence (2 references)

PMID:24360805 SUPPORT Human Clinical

"Neither the transcript nor the protein was observed in this individual, confirming the pathogenicity of this variant."

Demonstrates complete loss of DNAH1 product in a patient, establishing the molecular lesion.

PMID:27573432 SUPPORT Human Clinical

"the variant DNAH1 protein could not be detected in spermatozoa by Western blot or immunofluorescence staining although DNAH1 mRNA was expressed in the spermatozoa"

Shows the frameshift allele yields no detectable protein despite retained mRNA, an independent route to the same protein-level loss.

Axonemal Disorganization and Inner Dynein Arm Loss

The sperm axoneme loses its inner dynein arms and its ordered microtubule-doublet arrangement. Further ultrastructural defects reported across cohorts include absence of the central pair, disorganization of the fibrous sheath, missing radial spokes, and displaced outer dense fibers, so the lesion extends beyond the dynein arm itself to the wider accessory architecture of the flagellum.

Sperm CL:0000019

Inner dynein arm GO:0036156 Sperm flagellum GO:0036126 Axoneme GO:0005930

Downstream

Multiple Morphological Abnormalities of the Sperm Flagella A disorganized axoneme cannot support a normally formed flagellum, giving the mosaic of absent, short, coiled and irregular flagella.

Show evidence (1 reference)

PMID:33989052 SUPPORT Human Clinical

"Transmission electron microscopy of the sperm flagella showed that the inner dynein arm and radial spoke were absent, and the dense fiber and microtubule doublets were displaced."

Independent ultrastructural confirmation of inner dynein arm loss with wider accessory-structure disruption.

Multiple Morphological Abnormalities of the Sperm Flagella

The defining semen phenotype: a mosaic of absent, short, coiled, bent and irregular-caliber flagella within the same ejaculate. The mosaicism is characteristic - this is not uniform absence of flagella but a mixture of malformations, which is what distinguishes MMAF from other flagellar defects on standard semen analysis.

Sperm CL:0000019

Sperm axoneme assembly GO:0007288 ↓ DECREASED

Animal models

Dnah1 ferf1 ENU missense mouse Mouse fails to recapitulate Homozygous ferf1 males are infertile, but their sperm is described as apparently normal in appearance rather than showing the mosaic of absent, short and coiled flagella that defines human MMAF. The block is at zona pellucida penetration, and the sperm remain competent to fertilize zona-free oocytes - a fertilization-failure phenotype rather than a flagellar-morphogenesis one.

Downstream

Reduced sperm motility Malformed flagella lacking inner dynein arms cannot generate propulsive beating.

Male infertility Immotile sperm cannot reach or fertilize the oocyte in vivo.

Show evidence (1 reference)

PMID:24360805 SUPPORT Human Clinical

"a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"

Defines the mosaic flagellar phenotype that constitutes this node.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

6

Genitourinary 1

Male infertility HP:0003251

Show evidence (1 reference)

PMID:24360805 SUPPORT Human Clinical

"presenting with primary infertility resulting from impaired sperm motility"

Primary infertility is the presenting phenotype in the mapping cohort.

Other 5

Reduced sperm motility HP:0012207

Show evidence (1 reference)

PMID:36510862 SUPPORT Human Clinical

"Three primary infertile males with completely immobile sperm and MMAF were enrolled."

Documents the severe end of the motility phenotype in genotyped patients.

Coiled sperm flagella HP:0032560

Show evidence (1 reference)

PMID:33989052 SUPPORT Human Clinical

"Results of Papanicolaou staining and scanning electron microscopy demonstrated coiled and short flagella with multiple anomalies."

Direct morphological documentation of the flagellar abnormalities in a genotyped patient.

Absent sperm flagella HP:0032558

Show evidence (1 reference)

PMID:24360805 SUPPORT Human Clinical

"a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"

Enumerates absent flagella among the coexisting abnormalities.

Short sperm flagella HP:0032559

Show evidence (1 reference)

PMID:24360805 SUPPORT Human Clinical

"a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"

Enumerates short flagella among the coexisting abnormalities.

Bent sperm flagella HP:0034811

Show evidence (1 reference)

PMID:24360805 SUPPORT Human Clinical

"a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"

Enumerates bent flagella among the coexisting abnormalities.

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Genetic Associations

1

DNAH1 (Causal)

Gene: DNAH1 hgnc:2940

Show evidence (2 references)

PMID:24360805 SUPPORT Human Clinical

"Five unrelated subjects out of 18 (28%) carried a homozygous variant in DNAH1, which encodes an inner dynein heavy chain and is expressed in testis."

Establishes DNAH1 as a causal gene and quantifies its share of the MMAF cohort.

PMID:27573432 SUPPORT Human Clinical

"four of the nine patients were affected by the same homozygous frameshift mutation c.11726_11727delCT"

Identifies the recurrent East Asian founder-like frameshift allele.

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Medical Actions

1

Intracytoplasmic Sperm Injection

Action: Intracytoplasmic Sperm Injection NCIT:C185482

ICSI bypasses the defect directly: the lesion is one of flagellar motility and form, not of the sperm nucleus, so injecting a single spermatozoon into the oocyte circumvents every step the malformed flagellum would have had to perform. Reported outcomes for MMAF couples do not differ from other couples requiring ICSI, and this holds irrespective of which gene is responsible - though the same study notes occasional technical difficulty in handling these sperm.

Mechanism Target:

Multiple Morphological Abnormalities of the Sperm Flagella — Direct injection makes flagellar propulsion and morphology irrelevant to fertilization.

Show evidence (1 reference)

PMID:34529793 SUPPORT Human Clinical

"Despite occasional technical difficulties, ICSI outcomes for couples with MMAF do not differ from those of other couples requiring ICSI, irrespective of the genetic defect."

Establishes that ICSI overcomes the mechanism, with outcomes equivalent to other ICSI indications.

Show evidence (1 reference)

PMID:34529793 SUPPORT Human Clinical

"The ICSI results obtained for 20 couples with MMAF were compared to those of 378 men with oligoasthenoteratozoospermia but no MMAF as an ICSI control group."

Describes the controlled comparison underlying the equivalent-outcome conclusion.

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Diagnosis

3

Semen Analysis with Flagellar Morphology Assessment

The entry point. Standard semen analysis shows severe asthenozoospermia, and light microscopy shows the mosaic that defines MMAF - absent, short, coiled, bent and irregular-caliber flagella coexisting in one sample. The mosaicism is what distinguishes MMAF from uniform flagellar absence, so the morphological read is diagnostic rather than merely descriptive.

semen analysis with flagellar morphology assessment NCIT:C25294

Show evidence (1 reference)

PMID:24360805 SUPPORT Human Clinical

"a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"

Defines the morphological picture that semen analysis is looking for.

Transmission Electron Microscopy of the Sperm Flagellum

Establishes the ultrastructural lesion the pathograph is built on - loss of the inner dynein arms with mislocalized microtubule doublets, and in other patients absent central pair, disorganized fibrous sheath and displaced outer dense fibers. This is the step that distinguishes an axonemal defect from a purely morphological one.

transmission electron microscopy of the sperm flagellum NCIT:C25294

Show evidence (1 reference)

PMID:24360805 SUPPORT Human Clinical

"A general axonemal disorganization including mislocalization of the microtubule doublets and loss of the inner dynein arms was observed."

The ultrastructural finding this modality establishes.

Whole-Exome Sequencing or Male-Infertility Gene Panel

Identifies the causal gene. DNAH1 is among the commonest causes of MMAF, so a molecular diagnosis is achievable in a substantial share of men with this semen phenotype, and it clarifies recurrence risk for the couple.

Genetic Testing NCIT:C15709

Show evidence (1 reference)

PMID:27573432 SUPPORT Human Clinical

"further confirmed the effectiveness of genetic screening in the diagnosis of MMAF"

Supports genetic screening as an effective diagnostic route in MMAF.

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Prevalence

1

Men with the MMAF phenotype

Unknown Unknown

Recorded as a share of MMAF cases, not a population prevalence: DNAH1 accounted for 28% of an 18-case North African MMAF series. No population-level estimate for SPGF18 exists.

Show evidence (1 reference)

PMID:24360805 SUPPORT Human Clinical

"Five unrelated subjects out of 18 (28%) carried a homozygous variant in DNAH1"

The reported DNAH1 yield within an MMAF cohort.

🔀

Differential Diagnoses

1

Conditions with similar clinical presentations that must be differentiated from Spermatogenic Failure 18:

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Animal Models

1

Dnah1 ferf1 ENU missense mouse

An ENU-induced single-base Dnah1 missense allele causing male infertility in homozygous mice. It is informative for the gene-to-infertility link but reproduces the human cellular phenotype only in part, which is itself the useful result.

Species

Mouse

Genotype

Dnah1 ferf1 (ENU-induced missense), homozygous

Publication

PMID:30734403

Pathograph links

Multiple Morphological Abnormalities of the Sperm Flagella fails to recapitulate fidelity: low Homozygous ferf1 males are infertile, but their sperm is described as apparently normal in appearance rather than showing the mosaic of absent, short and coiled flagella that defines human MMAF. The block is at zona pellucida penetration, and the sperm remain competent to fertilize zona-free oocytes - a fertilization-failure phenotype rather than a flagellar-morphogenesis one.

Limitations: This is a missense allele, whereas the human disease is most clearly established for protein-null genotypes, so the divergence may reflect allele class rather than species. The model should not be used to argue about human flagellar morphogenesis, and the paper itself notes that DNAH1 mutations across mouse and human give a diversity of phenotypes.

Readouts

Sperm flagellar morphology

Direction: UNCHANGED

Interpretation: Sperm appearance is grossly preserved in the mouse, unlike the human phenotype. Recorded as a genuine negative result, not a missing measurement.

Show evidence (1 reference)

PMID:30734403 SUPPORT Model Organism

"producing apparently normal sperm that does not fertilize oocytes"

The morphology readout is explicitly normal in this model.

Show evidence (1 reference)

PMID:30734403 SUPPORT Model Organism

"male mice homozygous for the ethyl-nitroso-urea-induced ferf1 (fertilization failure 1) mutation are infertile, producing apparently normal sperm that does not fertilize oocytes in standard fertilization in vitro fertilization assays"

Apparently normal sperm morphology contradicts recapitulation of the human MMAF flagellar phenotype, which is why this link is FAILS_TO_RECAPITULATE.

{ }

Source YAML

click to show

name: Spermatogenic Failure 18
creation_date: "2026-09-04T00:00:00Z"
category: Mendelian
synonyms:
- SPGF18
- spermatogenic failure 18
- DNAH1-related multiple morphological abnormalities of the sperm flagella
description: >-
  Spermatogenic failure 18 (SPGF18) is autosomal recessive male infertility
  caused by biallelic variants in DNAH1, which encodes an inner-arm axonemal
  dynein heavy chain. Affected men present with primary infertility and a
  characteristic semen picture - severe asthenozoospermia with a mosaic of
  absent, short, coiled, bent and irregular-caliber flagella, the phenotype
  known as multiple morphological abnormalities of the flagella (MMAF).
  Ultrastructurally the axoneme is disorganized, with loss of the inner dynein
  arms and mislocalized microtubule doublets.

  The point of interest is what SPGF18 is not. DNAH1 encodes an axonemal
  dynein, and an axonemal dynein defect is the textbook lesion of primary
  ciliary dyskinesia - yet in the original cohort these men had no respiratory
  or other ciliary disease, and infertility was the only feature of PCD
  observed. The interpretation offered there is that DNAH1 matters far less to
  the motile cilium than to the sperm flagellum, despite being expressed in
  both. That reading is contested: a later study reported DNAH1 variation in
  clinically diagnosed PCD and argued the gene should be considered in PCD
  patients where the known genes are excluded, so the sparing of the airway is
  a cohort observation rather than a settled property of DNAH1 loss.

  Fertility is achievable: because the defect is one of motility and flagellar
  form rather than of the sperm nucleus, ICSI bypasses it, and reported
  outcomes for MMAF couples do not differ from other couples requiring ICSI.
disease_term:
  preferred_term: spermatogenic failure 18
  term:
    id: MONDO:0054615
    label: spermatogenic failure 18
parents:
- Spermatogenic Failure
- Genetic Disease
references:
- reference: PMID:24360805
  title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
inheritance:
- name: Autosomal recessive
  description: >-
    Disease requires biallelic DNAH1 variants. Reported genotypes include
    homozygosity in consanguineous North African families, a recurrent East
    Asian homozygous frameshift, and compound heterozygosity; parents and
    unaffected siblings are heterozygous carriers.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:27573432
    reference_title: "Homozygous DNAH1 frameshift mutation causes multiple morphological anomalies of the sperm flagella in Chinese."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The parents and the sibling of proband 1 were all identified as heterozygous carriers."
    explanation: Heterozygous unaffected parents and sibling establish recessive inheritance.
pathophysiology:
- name: Loss of the DNAH1 Inner-Arm Dynein Heavy Chain
  description: >-
    DNAH1 encodes an inner dynein arm heavy chain expressed in testis. Both
    truncating and missense routes converge on absence or dysfunction of the
    protein in sperm: in a donor-splice-site case neither transcript nor
    protein was detectable, and in the recurrent East Asian frameshift the
    protein was undetectable by Western blot and immunofluorescence even though
    DNAH1 mRNA was still present in spermatozoa - so loss of protein, not loss
    of transcript, is the common endpoint.
  biological_scale: MOLECULAR
  downstream:
  - target: Axonemal Disorganization and Inner Dynein Arm Loss
    causal_link_type: DIRECT
    description: >-
      Absence of the heavy chain removes the inner dynein arms it forms and
      destabilizes axonemal architecture.
    evidence:
    - reference: PMID:24360805
      reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A general axonemal disorganization including mislocalization of the microtubule doublets and loss of the inner dynein arms was observed."
      explanation: Electron microscopy in a patient lacking DNAH1 protein shows precisely the predicted structural consequence.
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neither the transcript nor the protein was observed in this individual, confirming the pathogenicity of this variant."
    explanation: Demonstrates complete loss of DNAH1 product in a patient, establishing the molecular lesion.
  - reference: PMID:27573432
    reference_title: "Homozygous DNAH1 frameshift mutation causes multiple morphological anomalies of the sperm flagella in Chinese."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the variant DNAH1 protein could not be detected in spermatozoa by Western blot or immunofluorescence staining although DNAH1 mRNA was expressed in the spermatozoa"
    explanation: Shows the frameshift allele yields no detectable protein despite retained mRNA, an independent route to the same protein-level loss.
- name: Axonemal Disorganization and Inner Dynein Arm Loss
  description: >-
    The sperm axoneme loses its inner dynein arms and its ordered
    microtubule-doublet arrangement. Further ultrastructural defects reported
    across cohorts include absence of the central pair, disorganization of the
    fibrous sheath, missing radial spokes, and displaced outer dense fibers, so
    the lesion extends beyond the dynein arm itself to the wider accessory
    architecture of the flagellum.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Sperm
    term:
      id: CL:0000019
      label: sperm
  cellular_components:
  - preferred_term: Inner dynein arm
    term:
      id: GO:0036156
      label: inner dynein arm
  - preferred_term: Sperm flagellum
    term:
      id: GO:0036126
      label: sperm flagellum
  - preferred_term: Axoneme
    term:
      id: GO:0005930
      label: axoneme
  downstream:
  - target: Multiple Morphological Abnormalities of the Sperm Flagella
    causal_link_type: DIRECT
    description: >-
      A disorganized axoneme cannot support a normally formed flagellum, giving
      the mosaic of absent, short, coiled and irregular flagella.
    evidence:
    - reference: PMID:36510862
      reference_title: "Novel compound heterozygous mutations in DNAH1 cause primary infertility in Han Chinese males with multiple morphological abnormalities of the sperm flagella."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The absence of the center pair and disorganization of the fibrous sheath were present in sperm flagella at the ultrastructural level."
      explanation: Links the ultrastructural disorganization to the flagellar morphological phenotype in DNAH1 patients.
  evidence:
  - reference: PMID:33989052
    reference_title: "Novel Biallelic DNAH1 Variations Cause Multiple Morphological Abnormalities of the Sperm Flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Transmission electron microscopy of the sperm flagella showed that the inner dynein arm and radial spoke were absent, and the dense fiber and microtubule doublets were displaced."
    explanation: Independent ultrastructural confirmation of inner dynein arm loss with wider accessory-structure disruption.
- name: Multiple Morphological Abnormalities of the Sperm Flagella
  description: >-
    The defining semen phenotype: a mosaic of absent, short, coiled, bent and
    irregular-caliber flagella within the same ejaculate. The mosaicism is
    characteristic - this is not uniform absence of flagella but a mixture of
    malformations, which is what distinguishes MMAF from other flagellar
    defects on standard semen analysis.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Sperm
    term:
      id: CL:0000019
      label: sperm
  biological_processes:
  - preferred_term: Sperm axoneme assembly
    term:
      id: GO:0007288
      label: sperm axoneme assembly
    modifier: DECREASED
  downstream:
  - target: Reduced sperm motility
    causal_link_type: DIRECT
    description: >-
      Malformed flagella lacking inner dynein arms cannot generate propulsive
      beating.
    evidence:
    - reference: PMID:24360805
      reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "primary infertility resulting from impaired sperm motility caused by a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"
      explanation: States the causal sequence from flagellar malformation to impaired motility to infertility.
  - target: Male infertility
    causal_link_type: DIRECT
    description: >-
      Immotile sperm cannot reach or fertilize the oocyte in vivo.
    evidence:
    - reference: PMID:24360805
      reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "primary infertility resulting from impaired sperm motility caused by a mosaic of multiple morphological abnormalities of the flagella (MMAF)"
      explanation: The primary report's own statement of the causal chain ending in infertility.
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"
    explanation: Defines the mosaic flagellar phenotype that constitutes this node.
mechanistic_hypotheses:
- hypothesis_group_id: flagellum_specific_dynein_requirement
  hypothesis_label: DNAH1 is required by the sperm flagellum but largely dispensable in motile cilia, which is why SPGF18 is not primary ciliary dyskinesia
  status: EMERGING
  description: >-
    DNAH1 encodes an axonemal dynein heavy chain and is expressed in ciliated
    cells beyond the testis, so biallelic loss would be expected to produce
    primary ciliary dyskinesia - chronic sinopulmonary disease, otitis media,
    possible situs inversus. It does not. In the original 20-subject cohort,
    infertility was the only PCD feature observed. The proposed explanation is
    that DNAH1's contribution to the motile cilium is redundant, covered by
    other inner-arm dynein heavy chains, while the sperm flagellum has no such
    redundancy.

    The evidence is an absence of reported respiratory disease rather than a
    systematic ciliary assessment, and the cohorts are small, so this is
    recorded as EMERGING. Distinguishing genuine tissue-specific redundancy
    from mild or unascertained ciliary disease would require nasal nitric oxide
    measurement or ciliary beat analysis in genotyped men, which no published
    study reports.

    There is also direct counter-evidence. Two sisters with clinically
    diagnosed PCD carry a homozygous DNAH1 missense variant segregating
    completely with the phenotype, and OMIM recognises a separate DNAH1 ciliary
    dyskinesia entity (CILD37) on that basis. That does not overturn the
    tissue-specific-redundancy reading - the alleles differ and the SPGF18
    cohorts genuinely lack ciliary disease - but it does mean the redundancy
    cannot be a property of losing DNAH1 as such, and that a DNAH1 finding
    cannot be used to rule ciliary disease out.
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although DNAH1 is also expressed in other ciliated cells, infertility was the only symptom of primary ciliary dyskinesia observed in affected subjects, suggesting that DNAH1 function in cilium is not as critical as in sperm flagellum."
    explanation: The authors' own statement of both the observation and the proposed tissue-specific-redundancy explanation.
  - reference: PMID:25927852
    reference_title: "Variation in DNAH1 may contribute to primary ciliary dyskinesia."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "A novel homozygous missense aberration (p.Lys1154Gln) was identified in both sisters in the DNAH1 gene that segregated completely with the disease phenotype."
    explanation: >-
      Direct counter-evidence. A homozygous DNAH1 variant segregating with
      clinically diagnosed PCD means ciliary dysfunction from DNAH1 variation is
      possible, so redundancy cannot be a property of DNAH1 loss as such.
  - reference: PMID:25927852
    reference_title: "Variation in DNAH1 may contribute to primary ciliary dyskinesia."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Molecular variation in DNAH1 may play a role in PCD and its potential contribution should be considered in patients where all known genes are excluded."
    explanation: The authors' own conclusion that DNAH1 should be considered in PCD, which is incompatible with treating a DNAH1 finding as excluding ciliary disease.
phenotypes:
- category: Reproductive
  name: Male infertility
  description: >-
    Primary infertility is the presenting and, characteristically, the only
    complaint. Affected men are otherwise well.
  phenotype_term:
    preferred_term: Male infertility
    term:
      id: HP:0003251
      label: Male infertility
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presenting with primary infertility resulting from impaired sperm motility"
    explanation: Primary infertility is the presenting phenotype in the mapping cohort.
- category: Reproductive
  name: Reduced sperm motility
  description: >-
    Severe asthenozoospermia, in some reported patients amounting to completely
    immotile sperm.
  phenotype_term:
    preferred_term: Reduced sperm motility
    term:
      id: HP:0012207
      label: Reduced sperm motility
  evidence:
  - reference: PMID:36510862
    reference_title: "Novel compound heterozygous mutations in DNAH1 cause primary infertility in Han Chinese males with multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Three primary infertile males with completely immobile sperm and MMAF were enrolled."
    explanation: Documents the severe end of the motility phenotype in genotyped patients.
- category: Reproductive
  name: Coiled sperm flagella
  description: >-
    Flagella coiled back on themselves, one of the elements that coexist in the
    MMAF mosaic alongside the absent, short and bent forms recorded separately
    below.
  phenotype_term:
    preferred_term: Coiled sperm flagella
    term:
      id: HP:0032560
      label: Coiled sperm flagella
  evidence:
  - reference: PMID:33989052
    reference_title: "Novel Biallelic DNAH1 Variations Cause Multiple Morphological Abnormalities of the Sperm Flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Results of Papanicolaou staining and scanning electron microscopy demonstrated coiled and short flagella with multiple anomalies."
    explanation: Direct morphological documentation of the flagellar abnormalities in a genotyped patient.
- category: Reproductive
  name: Absent sperm flagella
  description: >-
    Some spermatozoa in the same ejaculate lack flagella entirely, one element
    of the MMAF mosaic.
  phenotype_term:
    preferred_term: Absent sperm flagella
    term:
      id: HP:0032558
      label: Absent sperm flagella
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"
    explanation: Enumerates absent flagella among the coexisting abnormalities.
- category: Reproductive
  name: Short sperm flagella
  description: >-
    Shortened flagella coexist with absent and coiled forms in the same sample.
  phenotype_term:
    preferred_term: Short sperm flagella
    term:
      id: HP:0032559
      label: Short sperm flagella
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"
    explanation: Enumerates short flagella among the coexisting abnormalities.
- category: Reproductive
  name: Bent sperm flagella
  description: >-
    Bent flagella are a further element of the MMAF mosaic.
  phenotype_term:
    preferred_term: Bent sperm flagella
    term:
      id: HP:0034811
      label: Bent sperm flagella
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"
    explanation: Enumerates bent flagella among the coexisting abnormalities.
genetic:
- name: DNAH1
  association: Causal
  gene_term:
    preferred_term: DNAH1
    term:
      id: hgnc:2940
      label: DNAH1
  notes: >-
    Biallelic DNAH1 variants cause SPGF18. DNAH1 accounted for 5 of 18 index
    cases (28%) in the original North African MMAF cohort, making it one of the
    commonest single causes of the MMAF phenotype. The recurrent East Asian
    frameshift c.11726_11727delCT (p.Pro3909ArgfsTer33) has been found in
    multiple unrelated Han Chinese patients and appears population-specific.
    Compound heterozygous combinations of nonsense, missense, frameshift and
    splice alleles are also reported.
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Five unrelated subjects out of 18 (28%) carried a homozygous variant in DNAH1, which encodes an inner dynein heavy chain and is expressed in testis."
    explanation: Establishes DNAH1 as a causal gene and quantifies its share of the MMAF cohort.
  - reference: PMID:27573432
    reference_title: "Homozygous DNAH1 frameshift mutation causes multiple morphological anomalies of the sperm flagella in Chinese."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "four of the nine patients were affected by the same homozygous frameshift mutation c.11726_11727delCT"
    explanation: Identifies the recurrent East Asian founder-like frameshift allele.
  case_fractions:
  - population: North African MMAF cohort
    case_fraction_percent: 28.0
    cohort_size: 18
    notes: Five of 18 index cases with the MMAF phenotype carried a homozygous DNAH1 variant.
    evidence:
    - reference: PMID:24360805
      reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Five unrelated subjects out of 18 (28%) carried a homozygous variant in DNAH1"
      explanation: The reported DNAH1 share of an MMAF case series.
animal_models:
- name: Dnah1 ferf1 ENU missense mouse
  species: Mouse
  genotype: Dnah1 ferf1 (ENU-induced missense), homozygous
  publication: PMID:30734403
  description: >-
    An ENU-induced single-base Dnah1 missense allele causing male infertility in
    homozygous mice. It is informative for the gene-to-infertility link but
    reproduces the human cellular phenotype only in part, which is itself the
    useful result.
  modeled_mechanisms:
  - target: Multiple Morphological Abnormalities of the Sperm Flagella
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      Homozygous ferf1 males are infertile, but their sperm is described as
      apparently normal in appearance rather than showing the mosaic of absent,
      short and coiled flagella that defines human MMAF. The block is at zona
      pellucida penetration, and the sperm remain competent to fertilize
      zona-free oocytes - a fertilization-failure phenotype rather than a
      flagellar-morphogenesis one.
    limitations: >-
      This is a missense allele, whereas the human disease is most clearly
      established for protein-null genotypes, so the divergence may reflect
      allele class rather than species. The model should not be used to argue
      about human flagellar morphogenesis, and the paper itself notes that
      DNAH1 mutations across mouse and human give a diversity of phenotypes.
    evidence:
    - reference: PMID:30734403
      reference_title: "ENU-induced mutant allele of Dnah1, ferf1, causes abnormal sperm behavior and fertilization failure in mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "male mice homozygous for the ethyl-nitroso-urea-induced ferf1 (fertilization failure 1) mutation are infertile, producing apparently normal sperm that does not fertilize oocytes in standard fertilization in vitro fertilization assays"
      explanation: Apparently normal sperm morphology contradicts recapitulation of the human MMAF flagellar phenotype, which is why this link is FAILS_TO_RECAPITULATE.
    readouts:
    - name: Sperm flagellar morphology
      target: Multiple Morphological Abnormalities of the Sperm Flagella
      direction: UNCHANGED
      interpretation: >-
        Sperm appearance is grossly preserved in the mouse, unlike the human
        phenotype. Recorded as a genuine negative result, not a missing
        measurement.
      evidence:
      - reference: PMID:30734403
        reference_title: "ENU-induced mutant allele of Dnah1, ferf1, causes abnormal sperm behavior and fertilization failure in mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "producing apparently normal sperm that does not fertilize oocytes"
        explanation: The morphology readout is explicitly normal in this model.
  - target: Reduced sperm motility
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Motility is abnormal in the model, but as aberrant motility and sperm
      clumping rather than the severe asthenozoospermia or complete immotility
      seen in patients.
    limitations: >-
      Aberrant motility with preserved zona-free fertilizing ability is a milder
      and qualitatively different defect from the human phenotype.
    readouts:
    - name: Sperm motility behaviour
      target: Reduced sperm motility
      direction: ALTERED
      interpretation: Motility is qualitatively abnormal rather than abolished.
      evidence:
      - reference: PMID:30734403
        reference_title: "ENU-induced mutant allele of Dnah1, ferf1, causes abnormal sperm behavior and fertilization failure in mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "leads to abnormal sperm clumping, aberrant sperm motility, and the inability of sperm to penetrate the oocyte's zona pellucida"
        explanation: Documents the altered motility phenotype in the model.
discussions:
- discussion_id: dnah1_mouse_flagellar_mismatch
  kind: HUMAN_MODEL_MISMATCH
  prompt: >-
    Does the Dnah1 ferf1 mouse model the human MMAF flagellar phenotype at all,
    or only the downstream infertility - and is the divergence a species
    difference or an allele-class difference?
  attaches_to:
  - pathophysiology#Multiple Morphological Abnormalities of the Sperm Flagella
  - animal_models#Mouse
  rationale: >-
    The Dnah1 ferf1 allele produces infertility with apparently normal sperm
    morphology and a zona-penetration block, whereas human
    biallelic DNAH1 loss produces gross flagellar malformation with inner
    dynein arm loss. The model therefore reproduces the clinical endpoint by a
    route that may not be the human one. Because ferf1 is a missense allele and
    the best-characterised human genotypes are protein-null, the divergence
    could be allele class rather than species - a distinction that determines
    whether the model is usable for studying human flagellar morphogenesis. The
    missense-versus-null framing is itself not decisive: a separate constitutive
    Dnah1 knockout is described with reduced motility and no TEM-detectable
    axonemal defect, which is also unlike the human ultrastructural phenotype,
    so a null allele does not obviously rescue the comparison. That knockout is
    not cited here because its primary description was not verified in this
    round. The ferf1 source paper makes the general point, noting that DNAH1
    mutations across mouse and human give a diversity of phenotypes with both
    subtle and considerable differences.
  evidence:
  - reference: PMID:30734403
    reference_title: "ENU-induced mutant allele of Dnah1, ferf1, causes abnormal sperm behavior and fertilization failure in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "the various mutations affecting the DNAH1 protein in both mouse and human produce a diversity of phenotypes with both subtle and considerable differences"
    explanation: The authors themselves flag the cross-species and cross-allele phenotypic divergence that this gap records.
differential_diagnoses:
- name: DNAH1-related primary ciliary dyskinesia (CILD37)
  disease_term:
    preferred_term: ciliary dyskinesia, primary, 37
    term:
      id: MONDO:0033204
      label: ciliary dyskinesia, primary, 37
  distinguishing_features:
  - >-
    Same gene, different presentation, and this is the differential that
    matters most for SPGF18. Two sisters from a consanguineous family with
    clinically diagnosed PCD carry a homozygous DNAH1 missense variant
    segregating with the phenotype, and OMIM assigns CILD37 to DNAH1 on that
    basis.
  - >-
    Chronic sinopulmonary disease - recurrent respiratory infection progressing
    to permanent lung damage - is present in CILD37 and absent from every
    reported SPGF18 patient. Respiratory history, not genotype, is what
    separates them.
  - >-
    A DNAH1 result therefore does not settle which entity is present. The
    entities were reached from opposite directions: SPGF18 from male-infertility
    cohorts screened for MMAF, CILD37 from a PCD family in whom all known genes
    had been excluded. Whether they are allele-specific outcomes of one gene or
    an ascertainment artefact is not resolved.
  evidence:
  - reference: PMID:25927852
    reference_title: "Variation in DNAH1 may contribute to primary ciliary dyskinesia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we describe our search to delineate the molecular basis in two affected sisters with clinically diagnosed PCD from a consanguineous Saudi Arabian family, in which all known genes have been excluded."
    explanation: Establishes the PCD presentation attributed to DNAH1 that this differential is about.
diagnosis:
- name: Semen Analysis with Flagellar Morphology Assessment
  description: >-
    The entry point. Standard semen analysis shows severe asthenozoospermia,
    and light microscopy shows the mosaic that defines MMAF - absent, short,
    coiled, bent and irregular-caliber flagella coexisting in one sample. The
    mosaicism is what distinguishes MMAF from uniform flagellar absence, so
    the morphological read is diagnostic rather than merely descriptive.
  diagnosis_term:
    preferred_term: semen analysis with flagellar morphology assessment
    term:
      id: NCIT:C25294
      label: Laboratory Procedure
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a mosaic of multiple morphological abnormalities of the flagella (MMAF) including absent, short, coiled, bent, and irregular flagella"
    explanation: Defines the morphological picture that semen analysis is looking for.
- name: Transmission Electron Microscopy of the Sperm Flagellum
  description: >-
    Establishes the ultrastructural lesion the pathograph is built on - loss of
    the inner dynein arms with mislocalized microtubule doublets, and in other
    patients absent central pair, disorganized fibrous sheath and displaced
    outer dense fibers. This is the step that distinguishes an axonemal defect
    from a purely morphological one.
  diagnosis_term:
    preferred_term: transmission electron microscopy of the sperm flagellum
    term:
      id: NCIT:C25294
      label: Laboratory Procedure
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A general axonemal disorganization including mislocalization of the microtubule doublets and loss of the inner dynein arms was observed."
    explanation: The ultrastructural finding this modality establishes.
- name: Whole-Exome Sequencing or Male-Infertility Gene Panel
  description: >-
    Identifies the causal gene. DNAH1 is among the commonest causes of MMAF, so
    a molecular diagnosis is achievable in a substantial share of men with this
    semen phenotype, and it clarifies recurrence risk for the couple.
  diagnosis_term:
    preferred_term: Genetic Testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:27573432
    reference_title: "Homozygous DNAH1 frameshift mutation causes multiple morphological anomalies of the sperm flagella in Chinese."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "further confirmed the effectiveness of genetic screening in the diagnosis of MMAF"
    explanation: Supports genetic screening as an effective diagnostic route in MMAF.
prevalence:
- population: Men with the MMAF phenotype
  measure_type: UNKNOWN
  prevalence_class: UNKNOWN
  notes: >-
    Recorded as a share of MMAF cases, not a population prevalence: DNAH1
    accounted for 28% of an 18-case North African MMAF series. No
    population-level estimate for SPGF18 exists.
  evidence:
  - reference: PMID:24360805
    reference_title: "Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Five unrelated subjects out of 18 (28%) carried a homozygous variant in DNAH1"
    explanation: The reported DNAH1 yield within an MMAF cohort.
treatments:
- name: Intracytoplasmic Sperm Injection
  description: >-
    ICSI bypasses the defect directly: the lesion is one of flagellar motility
    and form, not of the sperm nucleus, so injecting a single spermatozoon into
    the oocyte circumvents every step the malformed flagellum would have had to
    perform. Reported outcomes for MMAF couples do not differ from other couples
    requiring ICSI, and this holds irrespective of which gene is responsible -
    though the same study notes occasional technical difficulty in handling
    these sperm.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Intracytoplasmic Sperm Injection
    term:
      id: NCIT:C185482
      label: Intracytoplasmic Sperm Injection
  target_mechanisms:
  - target: Multiple Morphological Abnormalities of the Sperm Flagella
    description: >-
      Direct injection makes flagellar propulsion and morphology irrelevant to
      fertilization.
    evidence:
    - reference: PMID:34529793
      reference_title: "Genetic diagnosis, sperm phenotype and ICSI outcome in case of severe asthenozoospermia with multiple morphological abnormalities of the flagellum."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Despite occasional technical difficulties, ICSI outcomes for couples with MMAF do not differ from those of other couples requiring ICSI, irrespective of the genetic defect."
      explanation: Establishes that ICSI overcomes the mechanism, with outcomes equivalent to other ICSI indications.
  evidence:
  - reference: PMID:34529793
    reference_title: "Genetic diagnosis, sperm phenotype and ICSI outcome in case of severe asthenozoospermia with multiple morphological abnormalities of the flagellum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The ICSI results obtained for 20 couples with MMAF were compared to those of 378 men with oligoasthenoteratozoospermia but no MMAF as an ICSI control group."
    explanation: Describes the controlled comparison underlying the equivalent-outcome conclusion.

📚

References & Deep Research

References

1

PMID:24360805

Mutations in DNAH1, which encodes an inner arm heavy chain dynein, lead to male infertility from multiple morphological abnormalities of the sperm flagella.

No top-level findings curated for this source.

Deep Research

1

Claude Code ▸

Spermatogenic Failure 18 (SPGF18) — Comprehensive Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 1 citations 2026-09-04T01:57:36.220515

Spermatogenic Failure 18 (SPGF18) — Comprehensive Research Report

1. Disease Information

Overview. Spermatogenic Failure 18 (SPGF18; OMIM #617576) is a monogenic, autosomal recessive form of male infertility caused by biallelic (homozygous or compound heterozygous) mutation of DNAH1 (Dynein Axonemal Heavy Chain 1; HGNC:2940; chromosome 3p21.1), which encodes an inner dynein arm heavy chain of the sperm flagellar axoneme. SPGF18 is the prototype genetic cause of multiple morphological abnormalities of the sperm flagella (MMAF), a clinical/histological entity first formally defined in the disease-founding paper:

Ben Khelifa M, Coutton C, Zouari R, et al. "Mutations in DNAH1, which Encodes an Inner Arm Heavy Chain Dynein, Lead to Male Infertility from Multiple Morphological Abnormalities of the Sperm Flagella." American Journal of Human Genetics 2014;94(1):95-104. PMID: 24360805.

Affected men are phenotypically normal apart from primary infertility; ejaculated spermatozoa show a heterogeneous ("mosaic") mixture of absent, short, coiled, bent, and irregular-caliber flagella, producing severe asthenozoospermia (near-total or total immotility) combined with teratozoospermia (asthenoteratozoospermia).

Key identifiers: - OMIM: #617576 (SPERMATOGENIC FAILURE 18; SPGF18), part of the Spermatogenic Failure phenotypic series PS258150 - Gene/locus OMIM: 603332 (DNAH1), 3p21.1 - Related but distinct OMIM entry: #617577 — Ciliary Dyskinesia, Primary, 37 (CILD37), also caused by biallelic DNAH1 mutation but presenting as a respiratory ciliopathy rather than isolated infertility (see §5/§9 for the allelic-disorder distinction) - MalaCards: "Spermatogenic Failure 18" (https://www.malacards.org/card/spermatogenic_failure_18) - HGNC: DNAH1, HGNC:2940 - Suggested MONDO/HPO framing: HP:0034424 "Multiple morphological abnormalities of the sperm flagella"; HP:0008734 "Asthenozoospermia"; the disease is best represented in MONDO as a DNAH1-specific subtype within the broader MMAF/spermatogenic-failure disease family - Synonyms:* "DNAH1-related MMAF," "Spermatogenic failure due to multiple morphological abnormalities of the sperm flagella," "MMAF1" (informal literature usage)

Evidence basis. Nearly all published data on SPGF18 derive from aggregated clinical/genetic cohort studies of infertile men (exome/panel sequencing, semen analysis, electron microscopy), not individual case-report EHR data — i.e., disease-level knowledge assembled from multiple consanguineous and sporadic families across North African, Middle Eastern, and East Asian cohorts, supplemented by a mouse (Dnah1) knockout model.

2. Etiology

Primary cause: Biallelic loss-of-function or missense mutation in DNAH1 is necessary and sufficient to cause SPGF18; there is no reported environmental or infectious trigger — this is a purely Mendelian, structural/genetic disease of the sperm flagellar axoneme.

Genetic risk factors: - Consanguinity is a strong risk factor for expression of this autosomal recessive disease: in the founding cohort, 12 of 20 subjects were born to consanguineous parents (Ben Khelifa et al. 2014, PMID: 24360805). - Founder mutations. A recurrent splice-acceptor mutation (c.11788−1G>A) was found in 4/18 index cases in the original North African (Tunisian/Algerian/Libyan) cohort, with haplotype analysis supporting a founder effect (PMID: 24360805). Independently, a distinct frameshift founder allele, c.11726_11727delCT (p.Pro3909ArgfsTer33), linked to the polymorphism rs12163565, was identified as recurrent in East Asian/Chinese cohorts and was absent from non-Asian populations (Chinese cohort study; PMID: 33929677, J Assist Reprod Genet 2021). - No susceptibility loci, GWAS signals, or polygenic risk contributions have been reported; this is a single-gene Mendelian disorder, not a complex trait.

Environmental/lifestyle risk factors: None specifically implicated for SPGF18/DNAH1-MMAF; general male-infertility risk modifiers (smoking, heat exposure, toxins) are not reported as disease modifiers for this specific genetic entity in the literature retrieved.

Protective factors: None identified in the literature; there is no described protective allele or environmental protective factor specific to DNAH1-MMAF.

Gene-environment interaction: Not reported for this gene/phenotype; SPGF18 behaves as a fully genetically-determined trait.

3. Phenotypes

SPGF18 is essentially monosymptomatic at the organismal level (primary infertility) with the defining abnormality confined to sperm cell morphology and motility (laboratory/semen-analysis findings):

Phenotype	Description	Frequency/Severity	Suggested HP term
Primary male infertility	Inability to conceive despite unprotected intercourse; presenting complaint in all reported cases	100% (defining feature)	HP:0003251 (Male infertility)
Multiple morphological abnormalities of the sperm flagella (MMAF)	Mosaic of absent, short, coiled, bent, and irregular-caliber flagella in the same ejaculate	100% (defining feature); "mosaic" pattern rather than a single uniform defect	HP:0034424
Severe/total asthenozoospermia	Near-zero to zero progressive sperm motility. In the founding cohort, 11/18 index cases had 0% motility and 8 had <10% motility (PMID: 24360805)	Severe to complete; variable between families/genotypes	HP:0008734
Teratozoospermia	Abnormal sperm head/midpiece/flagellum morphology co-occurring with flagellar defects	Present in essentially all cases (asthenoteratozoospermia)	HP:0012207 (Teratozoospermia, if available) / free text
Normal secondary sexual characteristics, normal testicular volume, normal hormone profile	Reported as typically normal in DNAH1-MMAF cases, distinguishing it from hypogonadal causes of infertility	Common but not universally documented	—
Absence of respiratory/ciliary symptoms	Ben Khelifa et al. note that DNAH1-MMAF patients reported no primary ciliary dyskinesia (PCD) symptoms despite DNAH1 expression in ciliated respiratory tissue, suggesting tissue-specific compensation (PMID: 24360805)	Notable negative finding	Relevant to differential diagnosis (see §6, §9)

Onset: Adult-onset presentation, essentially always identified at reproductive age during infertility workup; there is no pediatric or congenital extra-reproductive phenotype described for the pure SPGF18 form (contrast with the CILD37 allelic disorder, which can present with neonatal respiratory distress; see §9).

Progression: Non-progressive — this is a static structural/functional defect of gametogenesis rather than a degenerative process; severity (percent motility, proportion of morphologically normal spermatozoa) is stable for a given individual and largely genotype-dependent.

Quality of life impact: The principal burden is reproductive/psychosocial (infertility-related distress) and the need for assisted reproduction; no data indicate impact on other domains of daily functioning, consistent with the tissue-restricted nature of the defect in the isolated SPGF18 form.

4. Genetic/Molecular Information

Causal gene: DNAH1 (Dynein Axonemal Heavy Chain 1) - HGNC: HGNC:2940 - Gene OMIM: 603332 - Cytoband/coordinates: 3p21.1 (GRCh38 chr3:52,310,920–52,400,492) — per GeneCards - Protein: A large (~4,477 amino acid) axonemal inner dynein arm (IDA) heavy chain, an ATPase-based motor protein containing six tandem AAA-ATPase domains* in its motor head plus a microtubule-binding domain (Ben Khelifa et al. 2014, PMID: 24360805; GeneCards). IDA heavy chains are believed to strengthen the mechanical linkage between the radial spokes and the outer doublet microtubules, driving flagellar beat generation and regulation.

Pathogenic variant spectrum (representative, from primary literature): - c.11788−1G>A (splice acceptor) — recurrent/founder in North African patients; 4/18 index cases (PMID: 24360805) - c.5094+1G>A (splice donor) - c.12796T>C (stop-loss) - c.3877G>A, p.Asp1293Asn (missense) - c.11726_11727delCT, p.Pro3909ArgfsTer33 — recurrent founder mutation in East Asian/Chinese cohorts, found in 4/9 patients with severe asthenozoospermia in one series (PMID: 33929677) - Additional hotspot variants reported in Chinese cohorts: p.R868X, p.Q1518X, p.E3284K, p.R4096L (PMID: 33929677) - Both truncating (nonsense, frameshift, splice) and missense variants have been associated with the classical MMAF phenotype, indicating that both complete loss-of-function and specific missense substitutions in functional domains (e.g., AAA-ATPase or microtubule-binding regions) are pathogenic.

Variant classification: Variants are generally classified pathogenic/likely pathogenic under ACMG/AMP criteria (biallelic occurrence, segregation with disease in consanguineous families, loss-of-function mechanism, absence/rarity in population databases such as gnomAD). Exact gnomAD allele-frequency and constraint (pLI/LOEUF) values for DNAH1 could not be retrieved from the sources searched in this session; DNAH1 is a very large gene, which typically yields a high raw count of rare missense/LoF variants in population databases even though biallelic pathogenic combinations remain rare — recommend querying gnomAD directly (gnomad.broadinstitute.org, gene DNAH1) to source these figures for curation.

Inheritance and zygosity: Autosomal recessive; both homozygous (favored in consanguineous pedigrees) and compound heterozygous genotypes are reported. Segregation was confirmed in a three-affected-brother sibship carrying the same homozygous splice mutation (PMID: 24360805).

Modifier genes: None specifically reported for DNAH1/SPGF18; however, MMAF as a phenotypic class is genetically heterogeneous, with distinct genes producing a convergent phenotype (locus heterogeneity, not modifier-gene effect — see §6).

Epigenetic information: No epigenetic (DNA methylation, histone) mechanism has been reported for DNAH1-associated MMAF; this is a structural axonemal-protein deficiency, not an epigenetic dysregulation disorder.

Chromosomal abnormalities: No aneuploidy, translocation, or copy-number mechanism reported; disease arises from small-scale (point/indel/splice) sequence variants within DNAH1.

5. Environmental Information

No environmental toxins, occupational exposures, radiation, infectious agents, or lifestyle factors have been implicated as causal or contributory to SPGF18 in the literature retrieved. This is consistent with SPGF18 being a fully penetrant, structurally determined Mendelian disorder of axonemal assembly rather than an environmentally modulated trait. (General environmental causes of asthenozoospermia — heat, toxins — are documented for male infertility broadly, but none are specifically linked to the DNAH1-MMAF mechanism.)

6. Mechanism / Pathophysiology

Causal chain (numbered, from molecular lesion to clinical manifestation)

Biallelic loss-of-function or damaging missense variants in DNAH1 → loss/reduction of functional DNAH1 protein in developing spermatid flagella (demonstrated directly; PMID: 24360805).
Loss of DNAH1 leads to failure of proper inner dynein arm (IDA) assembly and localization within the axoneme of the elongating sperm tail — TEM in an index case showed mislocalization and loss of inner dynein arms (PMID: 24360805).
Disrupted IDA scaffolding results in secondary structural disorganization of the "9+2" axonemal core: approximately one-third of outer microtubule doublets were malformed or absent, and the central-pair microtubules were entirely missing in 47% of examined cross-sections (a "9+0" configuration) in the founding study (PMID: 24360805).
Axonemal disorganization leads to severe disorganization of the surrounding fibrous sheath (abnormal/absent in ~90% of sections examined) — i.e., the defect is not confined to the dynein motor complex but propagates to the accessory cytoskeletal sheath that normally regulates flagellar beat mechanics (PMID: 24360805). This is presented as a downstream structural consequence, inferred from co-occurrence in the same ultrastructural sections rather than shown as an independent direct DNAH1 interaction.
Combined loss of IDA motor force generation, doublet/central-pair disorganization, and fibrous sheath collapse produces the mosaic gross flagellar phenotype observed by light microscopy — absent, short, coiled, bent, and irregular-caliber flagella coexisting within a single ejaculate (PMID: 24360805).
Structurally defective, motor-deficient flagella cause severe-to-total asthenozoospermia (0–<10% motility in most index cases) and teratozoospermia, jointly producing the clinical endpoint of primary male infertility by preventing normal sperm progression to and penetration of the oocyte (PMID: 24360805).
Branch — tissue-restricted expression/compensation: Despite DNAH1 also being expressed in respiratory motile cilia, DNAH1-MMAF patients characteristically lack primary ciliary dyskinesia (PCD) respiratory symptoms, suggesting a compensatory mechanism (e.g., partial redundancy with paralogous axonemal dyneins) operative in respiratory cilia but not in the sperm-specific flagellar axoneme (PMID: 24360805 — explicitly flagged by the authors as an inferred, not directly demonstrated, mechanism). A separate allelic disorder (CILD37, OMIM #617577) shows that sufficiently severe DNAH1 loss-of-function can produce a respiratory ciliopathy phenotype in some patients/pedigrees (PMID for the DNAH1-PCD family: 25927852), indicating this compensation is incomplete/variant-dependent rather than absolute.

Detail by category

Molecular pathway: Not a signaling cascade but a cytoskeletal motor-protein assembly pathway — dynein arm docking onto the axonemal doublet microtubules (relevant Reactome/GO context: "cilium organization," "axoneme assembly," "microtubule-based movement"). Suggested GO terms: GO:0036126 (sperm flagellum assembly), GO:0003777 (microtubule motor activity), GO:0005858 (axonemal dynein complex), GO:0030317 (flagellated sperm motility).
Cellular process: Spermiogenesis-stage flagellar morphogenesis defect (failure of proper axonemal/accessory-structure assembly during spermatid elongation), not apoptosis or classic degenerative cell death.
Protein dysfunction: Loss-of-function (absent/truncated protein from nonsense, frameshift, and splice variants) or presumed hypomorphic/structural missense dysfunction (e.g., p.Asp1293Asn) impairing motor-domain (AAA-ATPase) or microtubule-binding function, causing failure of stable dynein-arm docking (PMID: 24360805).
Species divergence (important translational caveat): The murine Dnah1 (Mdhc7) knockout is infertile via reduced sperm motility only, with no observable axonemal ultrastructural defect by electron microscopy — a materially milder phenotype than the severe human axonemal disorganization/MMAF seen with human DNAH1 loss. This is a documented human–model discordance (species/paralog redundancy differences), relevant to any HUMAN_MODEL_MISMATCH-type curation flag: the mouse model recapitulates the motility/infertility endpoint but fails to recapitulate the structural axonemal lesion.
Immune system involvement: None reported.
Tissue damage mechanism: Not classic tissue injury (oxidative stress, ischemia, fibrosis) — a developmental/structural assembly failure specific to a specialized cytoskeletal organelle (the flagellar axoneme) in a single, terminally differentiating cell type (the spermatid/spermatozoon).
Biochemical abnormality: Failure of a specific ATPase motor complex (inner dynein arm) to assemble/function normally within the axoneme.
Omics/advanced technologies: No dedicated transcriptomic, proteomic, metabolomic, single-cell, or spatial-transcriptomic dataset specific to DNAH1-MMAF spermatids was retrieved in this search; characterization to date rests principally on exome/targeted sequencing plus transmission electron microscopy (TEM) ultrastructural phenotyping, which remains the primary diagnostic and mechanistic tool in this literature.

Suggested cell type: CL:0000019 (sperm), or more specifically the elongating spermatid (developing flagellum) as the affected cell population; UBERON:0000995 / UBERON:0001301 (testis / spermatid) for anatomical/cellular context.

7. Anatomical Structures Affected

Organ level (primary): Testis — specifically the process of spermiogenesis (post-meiotic sperm maturation); UBERON:0000473 (testis).
Organ level (secondary/systemic): None — SPGF18 is not reported to involve other organ systems in its isolated form (contrast with the CILD37 allelic phenotype, which affects the respiratory tract; see §9).
Body system: Male reproductive system only (isolated form).
Tissue/cell level: Germ-cell lineage, specifically spermatids/spermatozoa during flagellar morphogenesis; Cell Ontology term CL:0000019 (sperm) or CL:0000018/CL:0000216 (spermatid stages) as appropriate.
Subcellular level: The sperm flagellum/axoneme is the principal subcellular structure affected — GO:0036126 (sperm flagellum assembly, cellular component), GO:0005858 (axonemal dynein complex), GO:0031514 (motile cilium), and the accessory fibrous sheath of the principal piece of the flagellum.
Localization: Bilateral/systemic within the reproductive tract (affects all developing spermatozoa, not a focal lesion); no lateralization concept applies.

8. Temporal Development

Onset: Adult, reproductive-age onset of clinical recognition (infertility investigation); the underlying structural defect is present from spermiogenesis onset but is asymptomatic until fertility is attempted.
Onset pattern: Not applicable in the acute/subacute/chronic sense — a stable, lifelong structural gametogenic defect.
Disease stages: Not applicable; MMAF/SPGF18 does not have formal staging.
Progression rate/course: Stable/non-progressive — repeat semen analyses in affected men are expected to show a consistently severe phenotype rather than worsening or fluctuating motility, since the defect is intrinsic to axonemal assembly rather than an ongoing degenerative process.
Duration: Lifelong (the underlying genetic lesion does not resolve), though the reproductive consequence is addressable via assisted reproduction (see §12).
Remission: None spontaneously; assisted reproduction (ICSI) can achieve pregnancy despite the underlying sperm defect (see §12), which functions as a bypass rather than a disease remission.
Critical periods: The relevant "critical period" is embryological/spermatogenic — spermiogenesis (the post-meiotic differentiation phase during which the flagellum is assembled) is the developmental window in which the DNAH1 defect is manifested.

9. Inheritance and Population

Inheritance pattern: Autosomal recessive (established via consanguineous pedigrees, sibling recurrence, and biallelic variant segregation; PMID: 24360805).
Penetrance: Appears complete for the infertility phenotype in biallelic carriers reported to date (all reported homozygotes/compound heterozygotes are infertile), though ascertainment bias (patients identified through infertility clinics) should be considered.
Expressivity: Variable in severity of motility/morphology defect and in extra-reproductive manifestation — most patients show isolated infertility, but rare DNAH1-biallelic patients present instead with the primary ciliary dyskinesia phenotype (CILD37, OMIM #617577; PMID: 25927852, describing a homozygous missense p.Lys1154Gln DNAH1 variant in a consanguineous Saudi Arabian PCD family with chronic wet cough, sinusitis, bronchiectasis, and neonatal respiratory distress). This indicates that DNAH1 is an allelic-disorder gene: different biallelic genotypes (and possibly genetic background) determine whether the clinical presentation is isolated MMAF/infertility (SPGF18) or a systemic ciliopathy (CILD37) — an important curation distinction to keep the two OMIM phenotypes (#617576 vs #617577) separate rather than conflated.
Genetic anticipation: Not reported/applicable (not a repeat-expansion disorder).
Germline mosaicism: Not specifically reported.
Founder effects: Documented — the c.11788−1G>A splice mutation is a founder allele in North African populations (Tunisia/Algeria/Libya; PMID: 24360805), and c.11726_11727delCT (p.Pro3909ArgfsTer33) is a distinct founder allele reported specifically in East Asian (Chinese) cohorts and linked to marker rs12163565 (PMID: 33929677) — evidence of independent founder events in geographically distinct populations rather than a single global founder mutation.
Consanguinity: A strong ascertainment/risk factor; 12/20 subjects in the founding cohort were from consanguineous unions (PMID: 24360805).
Carrier frequency: Not established/reported in the retrieved literature; DNAH1's large coding size likely yields population-level rare-variant carriage, but a validated carrier frequency figure was not found in this search and should be sourced from gnomAD directly for curation purposes.

Epidemiology: - DNAH1 is consistently identified as the most frequently mutated single gene in MMAF cohorts, accounting for roughly 28–29% of MMAF cases in the two largest reported series (28% in the founding North African cohort of 18 index cases, PMID: 24360805; 29% [12/41] in a Chinese NGS-panel cohort, PMID: 33929677), making DNAH1/SPGF18 the single largest identifiable genetic subgroup within the broader ~40-gene MMAF genetic landscape, within which "identified variants could account for about 60.0%–75.0% of infertile men diagnosed with MMAF," leaving 25–40% of MMAF cases genetically unsolved (review literature retrieved via search). - MMAF as a phenotypic class is a rare cause of male infertility overall; asthenozoospermia broadly accounts for a substantial fraction of male-factor infertility (~19–80% of cases depending on definition used across sources retrieved), but MMAF itself is a much narrower, severe subset. A precise population prevalence figure (cases per 100,000) specific to MMAF or SPGF18 was not found in the sources searched and is likely to be reported (if at all) via Orphanet, which should be queried directly for curation (Orphanet entry not successfully retrieved in this session due to a tool access limitation). - Population/geographic distribution: Cohorts studied span North Africa (Tunisia, Algeria, Libya), China/East Asia, Iran (Amiri-Yekta et al., Royan Institute), and Pakistan, with population-specific founder alleles identified in North African and East Asian groups — indicating DNAH1-MMAF is globally distributed but shaped by locally private founder mutations rather than one worldwide recurrent allele. - Sex ratio: Not applicable — by definition this is a male-limited spermatogenic phenotype (though female carriers of heterozygous variants are, as expected for autosomal recessive disease, unaffected and can transmit the allele). - Age distribution: Reproductive-age men presenting for infertility evaluation (typically 20s–40s), consistent with standard fertility-clinic ascertainment.

10. Diagnostics

Clinical/laboratory tests:
Semen analysis (WHO criteria) is the first-line test, showing severe asthenozoospermia (frequently 0–<10% motility) with concurrent teratozoospermia.
Light microscopy of sperm morphology reveals the characteristic mosaic of absent, short, coiled, bent, and irregular-caliber flagella that defines the MMAF phenotype.
Transmission electron microscopy (TEM) of sperm flagella is a key diagnostic/mechanistic tool, revealing inner dynein arm loss/mislocalization, disorganized/missing microtubule doublets (including 9+0 configurations from central-pair loss), and fibrous sheath disorganization (PMID: 24360805). Suggested SNOMED CT/pathology-relevant term: sperm axonemal ultrastructural abnormality.
Genetic testing:
Whole-exome sequencing (WES) and targeted MMAF gene panels (encompassing DNAH1 plus the ~40 other known MMAF genes: CFAP43, CFAP44, CFAP69, AK7, ARMC2, QRICH2, TTC29, DNAH8, DNAH17, DNAH2, FSIP2, CFAP91/WDR66, SPEF2, CFAP65, CEP135, TTC21A, AKAP4, CFAP47, CFAP57, CFAP70, DNHD1, TTC12, DNAH6, DNAH3, DNAH12, BRWD1, among others) are the standard diagnostic approach, since MMAF is genetically highly heterogeneous and clinically indistinguishable across causal genes by light microscopy alone.
NCBI GTR lists commercial "Spermatogenic failure: Full gene sequencing panel" tests covering DNAH1 and related genes.
Homozygosity mapping (SNP arrays) has historically been used in consanguineous pedigrees to localize the causal gene, as in the original DNAH1 discovery study.
Differential diagnosis: Other MMAF-causing genes (listed above) are the primary differential, since phenotype at the light-microscopy level is convergent/non-specific across genes; genetic testing is required to distinguish DNAH1-MMAF (SPGF18) from other genetic MMAF subtypes and from the related-but-distinct DNAH1-associated primary ciliary dyskinesia (CILD37) phenotype, which additionally requires assessment for respiratory ciliary dysfunction (nasal nitric oxide, ciliary beat pattern analysis, respiratory TEM) if extra-reproductive symptoms are present.
Screening: No population/newborn screening applies (adult-onset ascertainment via infertility); genetic counseling and carrier testing are relevant for consanguineous families or when a proband's biallelic genotype is known, to inform recurrence risk and family planning (including preimplantation genetic testing where infertility is overcome via ICSI).

11. Outcome/Prognosis

Survival/mortality: Not applicable — SPGF18 is not a life-limiting or morbid systemic condition in its isolated form; there is no reported mortality or shortened life expectancy directly attributable to DNAH1-MMAF.
Morbidity: The morbidity is essentially confined to infertility itself and its downstream psychosocial and reproductive-treatment burden.
Fertility-specific outcomes (the disease's core outcome measure):
DNAH1-mutated MMAF patients are reported to have a comparatively favorable prognosis with intracytoplasmic sperm injection (ICSI) relative to some other MMAF genotypes — this is a recurring theme across the literature retrieved (e.g., "Patients with multiple morphological abnormalities of the sperm flagella due to DNAH1 mutations have a good prognosis following intracytoplasmic sperm injection," Human Reproduction 2016;31(6):1164-1172).
One cohort reported a pregnancy rate of 61.90% among DNAH1-variant patients undergoing ICSI (Zhuang et al., cited in secondary literature retrieved).
Outcomes are nonetheless variable and genotype-dependent: not all DNAH1-mutation-positive patients succeed, and "failed cases still occur," attributed to variability in residual sperm structural/functional integrity and to specific variant effects on embryonic development potential (2022 literature review, Frontiers in Genetics, and related MMAF/ICSI outcome literature).
Broader MMAF literature (not DNAH1-specific) reports decreased embryo developmental potential and lower cumulative pregnancy rate in MMAF patients generally compared with non-MMAF infertile controls, underscoring that while DNAH1 has a relatively favorable reputation among MMAF genes, ICSI outcomes in MMAF as a class remain inferior to normospermic controls.
Complications: None specific to the disease beyond the infertility itself and standard ICSI-related risks (procedural, not disease-related).
Recovery potential: The underlying gametogenic/structural defect is not reversible, but fertility can be achieved via assisted reproduction bypassing the natural motility requirement (ICSI directly injects an immotile/structurally abnormal but genetically intact spermatozoon into the oocyte).
Prognostic factors: Genotype (specific DNAH1 variant/domain affected) appears to influence the degree of residual sperm structural integrity and thus ICSI/embryonic outcome, though granular genotype-outcome correlation data were not comprehensively retrievable in this search session.

12. Treatment

There is no curative or disease-modifying pharmacotherapy for SPGF18 — the mainstay of management is assisted reproductive technology bypassing the natural motility/morphology defect.

Primary therapeutic approach — Intracytoplasmic Sperm Injection (ICSI):
ICSI is the standard and effective treatment strategy, as DNAH1-mutation-positive men have consistently favorable reported ICSI outcomes relative to many other MMAF genotypes (Human Reproduction 2016;31(6):1164-1172, and subsequent cohort/review literature).
Clinical guidance explicitly states: "DNAH1 mutation positive patients can thus be encouraged to initiate an IVF/ICSI procedure" (2022 literature-review synthesis, Frontiers in Genetics, "Clinical detection, diagnosis and treatment of morphological abnormalities of sperm flagella: A review of literature").
NCIT clinical-intervention terms: Assisted reproductive procedures such as ICSI do not map to a discrete standard NCIT term set in the dismech treatment vocabulary excerpted; the closest general clinical-action term would be a fertility/reproductive procedure category — curators should verify against NCIT for an ICSI-specific term (e.g., search NCIT for "intracytoplasmic sperm injection") rather than assuming coverage under a generic surgical-procedure term.
Testicular sperm extraction (in cases of very low ejaculated sperm availability/quality) combined with ICSI has also been reported as a successful route in severe MMAF/total-immotility cases in the broader literature (e.g., successful birth after ICSI with testicular immotile spermatozoa in total-MMAF patients).
Sperm selection adjuncts: Techniques such as intracytoplasmic morphologically selected sperm injection (IMSI) have been studied in general severe male-factor infertility, though evidence specifically isolating DNAH1-MMAF benefit was not found in this search.
Genetic counseling: Recommended for affected men and their partners given the autosomal recessive inheritance and (in consanguineous populations) elevated recurrence risk; relevant for informed reproductive decision-making, including consideration of preimplantation genetic testing for offspring once pregnancy is achieved via ICSI, if the couple wishes to know/avoid transmission (though offspring would typically only be carriers unless the partner is also a carrier, given the rarity of the allele outside of consanguineous or founder populations).
No pharmacotherapy, gene therapy, or targeted molecular therapy has been reported or is in clinical development specifically for DNAH1/SPGF18 in the literature retrieved; this remains a structural/mechanical fertility problem managed via reproductive technology rather than molecular correction.
Experimental treatments: No DNAH1-specific clinical trials were identified in this search (search focused on general ICSI trials, not DNAH1-specific interventional trials); a targeted ClinicalTrials.gov / WHO ICTRP search for "DNAH1" or "MMAF" trials is recommended for curation completeness but did not surface a specific NCT identifier in the sources retrieved here.

13. Prevention

Primary prevention: Not applicable in the traditional sense (this is a fixed germline genetic disease, not preventable by exposure/behavior modification); the only "prevention" lever is reproductive — genetic counseling and carrier testing in consanguineous families or populations with known founder alleles (North African, East Asian) to inform reproductive planning.
Secondary prevention/early detection: Genetic testing of infertile men with the MMAF semen phenotype allows early, specific molecular diagnosis, which informs prognosis (see §11) and avoids unnecessary repeated empiric fertility interventions.
Screening: No population-level newborn or carrier screening program specific to DNAH1/MMAF was identified; carrier screening would be most relevant in a targeted fashion within consanguineous or founder-mutation-enriched populations, analogous to other autosomal recessive disease carrier-screening paradigms, but no such formal program was found in the literature searched.
Genetic counseling: The principal "preventive" clinical service applicable here — counseling affected men (and, where relevant, their reproductive partners) about autosomal recessive inheritance, recurrence risk for future pregnancies (particularly relevant if using a sperm donor is not desired and the couple pursues ICSI with the affected man's own testicular/ejaculated sperm), and reproductive options.
Public health/behavioral/immunization: Not applicable — no infectious, immunization-preventable, or public-health-environmental dimension to this disease.

14. Other Species / Natural Disease

Mouse (Mus musculus, NCBI Taxon:10090): The orthologous gene is Dnah1 (also referenced historically as Mdhc7*; MGI:107721). Dnah1-knockout mice are infertile due to markedly reduced sperm motility (dramatically reduced straight-line velocity and progressive movement, preventing sperm transit from the uterus into the oviduct), recapitulating the motility/infertility endpoint of the human disease. However, the mouse model critically fails to recapitulate the human structural phenotype: knockout sperm show no observable axonemal ultrastructural defect by electron microscopy, in clear contrast to the severe axonemal disorganization (doublet loss, missing central pair, fibrous sheath disruption) documented in DNAH1-deficient human spermatozoa (PMID: 24360805 and subsequent literature, e.g., PMC8635859 "Novel Loss-of-Function Mutations in DNAH1 Displayed Different Phenotypic Spectrum in Humans and Mice"). This is a well-documented, citable human/model fidelity gap — of direct relevance to curation using the HUMAN_MODEL_MISMATCH framework: the mouse model is informative for the infertility/motility endpoint (moderate-to-high fidelity) but has low fidelity for the axonemal ultrastructural mechanism* specifically, likely reflecting species differences in dynein-arm paralog redundancy or compensatory motor proteins.
Natural/veterinary disease: No naturally occurring companion-animal or livestock DNAH1-associated MMAF disease was retrieved in this session, though the broader MMAF-associated gene family has been studied in goats in the context of litter size and reproductive genetics (ScienceDirect: "Multiple morphological abnormalities of the sperm flagella (MMAF)-associated genes: The relationships between genetic variation and litter size in goats") — indicating comparative/agricultural relevance of the MMAF gene family (not confirmed DNAH1-specific) to livestock reproductive traits, worth checking OMIA for a DNAH1-specific animal entry during formal curation.
Comparative biology: DNAH1 is a member of a large, evolutionarily conserved axonemal dynein heavy chain gene family (paralogs include DNAH2, DNAH3, DNAH6, DNAH8, DNAH11, DNAH12, DNAH17, among others), each associated with distinct but phenotypically overlapping MMAF and/or PCD presentations in humans and, in several cases, validated in mouse knockout models (e.g., DNAH2, DNAH3, DNAH8, DNAH12), reflecting deep evolutionary conservation of axonemal dynein-based ciliary/flagellar motility across metazoans.
Transmission/zoonotic potential: Not applicable — this is a non-communicable, structural/genetic reproductive disorder.

15. Model Organisms

Primary genetic model: Dnah1 knockout mouse (constitutive knockout; historically referenced as Mdhc7−/−).
Phenotype recapitulation: Faithfully reproduces male infertility via severely impaired sperm motility (failure of sperm transit from uterus to oviduct due to reduced straight-line velocity/progressive movement).
Model limitation: Does not reproduce the defining human axonemal ultrastructural disorganization (no TEM-detectable doublet/central-pair/fibrous-sheath defects), making it a good model for the functional (motility) endpoint but a poor model for the structural (MMAF) mechanism — an important caveat for any computational or translational inference drawn from the mouse data.
Resource: MGI:107721 (Mouse Genome Informatics, Dnah1 gene page) for allele/phenotype records.
No invertebrate (Drosophila, C. elegans), zebrafish, yeast, or iPSC/organoid model specific to DNAH1/SPGF18 was identified in the literature retrieved during this session; given that flagellar/ciliary axonemal biology is broadly conserved, related invertebrate ciliary-motility models likely exist for the dynein gene family generally, but a DNAH1-specific citation was not found and should be checked directly in FlyBase/WormBase/ZFIN if needed for curation completeness.
Applications: The mouse model is primarily useful for studying motility mechanics and fertilization competence downstream of dynein-arm loss, but is not suited to modeling the axonemal structural assembly defect that is the histopathological hallmark of the human disease — human sperm TEM (from patient semen samples) therefore remains the indispensable source of mechanistic/structural data for SPGF18, rather than the mouse model.

Summary of Key Citations

Citation	Contribution
Ben Khelifa M, et al. Am J Hum Genet 2014;94(1):95-104. PMID: 24360805	Disease-founding paper: DNAH1 mutations cause MMAF/SPGF18; defines phenotype, mechanism, mouse-human discordance
Hum Reprod 2016;31(6):1164-1172 (Amiri-Yekta/Wambergue et al.)	DNAH1-MMAF ICSI prognosis is favorable
Hum Reprod 2016;31(12):2872-2880	Whole-exome sequencing of familial MMAF cases, new DNAH1 mutations
Chinese cohort study, J Assist Reprod Genet 2021. PMID: 33929677	Mutational landscape of DNAH1 in Chinese patients; East Asian founder allele
OMIM #617576 (SPGF18), *603332 (DNAH1), #617577 (CILD37)	Clinical synopsis, molecular genetics, allelic-disorder cross-reference
DNAH1-PCD family report. PMID: 25927852	DNAH1 as a cause of the allelic ciliopathy CILD37
GeneCards (DNAH1)	Gene structure, chromosomal location, protein domain architecture

Notable gaps for follow-up curation: exact Orphanet ORPHA code and formal prevalence class for MMAF/SPGF18 (WebFetch access to Orphanet was blocked this session — retry directly); gnomAD allele frequency/constraint (pLI, LOEUF) metrics for DNAH1; a DNAH1-specific ClinicalTrials.gov/WHO ICTRP entry, if any; and confirmation of whether an OMIA veterinary entry exists for DNAH1 specifically (distinct from the general goat MMAF-gene-family study identified).

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	4
Resolved	4
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	4
On topic	4
Off topic	0

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome	Count
Terms checked	18
Resolved	15
Unresolved (possible confabulation)	0
Obsolete	0
Unverifiable	3
Terms whose name was checked	5
Terms named correctly	2
Terms named as a different term	2
Terms whose name is worth a second look	1

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

HP:0034424 (2 mentions) - the report calls it "100% (defining feature); "mosaic" pattern rather than a single uniform defect"; HP calls it Clicking tinnitus
HP:0008734 (2 mentions) - the report calls it "Severe to complete; variable between families/genotypes"; HP calls it Decreased testicular size

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

HP:0012207 (1 mention) - the report calls it "Teratozoospermia, if available"; HP calls it Reduced sperm motility, and lists "Asthenozoospermia" among its other names

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: Taxon, MGI.

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References & Deep Research

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Spermatogenic Failure 18 (SPGF18) — Comprehensive Research Report

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

Causal chain (numbered, from molecular lesion to clinical manifestation)

Detail by category

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Summary of Key Citations

Reference Validation

Term Validation

Terms the report names something else

Terms whose name is worth a second look

Prefixes with no resolver