DONSON-Related Microcephalic Primordial Dwarfism

Mendelian MONDO:0035534 Pathograph 13 Show in embeddings browser Autosomal recessive disease Primordial dwarfism

Biallelic DONSON variants cause a spectrum of microcephalic primordial dwarfism that the literature has named three times over: microcephaly-micromelia syndrome, microcephaly with short stature and limb abnormalities (MISSLA), and Meier-Gorlin syndrome - reflecting which cohort the patients were ascertained in rather than three distinct diseases. DONSON is a replisome component. Its function was established in two stages: first as a replication fork protection factor whose loss causes nucleolytic cleavage of stalled forks and impaired ATR-dependent replication-stress signalling, and later, unexpectedly, as an essential assembly factor for the CDC45-MCM-GINS (CMG) helicase during S phase. That second finding is what makes DONSON the thirteenth Meier-Gorlin gene: the other twelve encode CMG subunits or established CMG assembly factors, and DONSON turned out to belong to the same process despite having no orthologue in budding yeast, where replication initiation can be reconstituted without it.

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1
Inheritance
4
Pathophys.
10
Phenotypes
1
Gaps
13
Pathograph
1
Genes
4
Subtypes
6
References
1
Deep Research
🏷

Classifications

Harrison's Part
GENETICS ENVIRONMENT DISEASE
ISDS Skeletal Nosology
primordial dwarfism and slender bones
👪

Inheritance

1
Autosomal recessive HP:0000007
Biallelic hypomorphic DONSON variants, homozygous or compound heterozygous. Complete loss would be expected to be lethal, since DONSON is essential for chromosome duplication.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:28191891 SUPPORT Human Clinical
"All variants segregated amongst family members in a manner consistent with an autosomal recessive trait"
Segregation across the discovery families establishes recessive inheritance.
◆

Subtypes

4
Microcephaly-micromelia syndrome (MMS) MONDO:0009619
DONSON hgnc:2993 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in DONSON (hgnc:2993). hgnc:2993 is a gene from the HUGO Gene Nomenclature Committee.
The severe end of the spectrum, named for the limb reduction that distinguishes it. Prenatally lethal or near-lethal in the most affected families. Corresponds to OMIM 251230; it and MISSLA share the single ISDS row NOS 21-0200.
Microcephaly, short stature, and limb abnormalities (MISSLA) MONDO:0060533
DONSON hgnc:2993 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in DONSON (hgnc:2993). hgnc:2993 is a gene from the HUGO Gene Nomenclature Committee.
The survivable presentation, with microcephaly and severe short stature alongside variable and generally milder limb findings - radial ray defects rather than limb reduction. Corresponds to OMIM 617604.
DONSON-related Meier-Gorlin syndrome
DONSON hgnc:2993 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in DONSON (hgnc:2993). hgnc:2993 is a gene from the HUGO Gene Nomenclature Committee.
Neither an OMIM entry nor an ISDS row - a presentation, not a separate entity. Two apparently unrelated families homozygous for c.631C>T p.(Arg211Cys) had clinically typical Meier-Gorlin syndrome, and DONSON's later-established role in CMG helicase assembly explains why. No MONDO leaf exists for the DONSON-specific form, so this subtype carries no subtype_term; dismech also lists DONSON as a Meier-Gorlin gene in kb/disorders/Meier-Gorlin_Syndrome.yaml.
Show evidence (1 reference)
PMID:31407851 SUPPORT Human Clinical
"Two apparently unrelated families with identical homozygous c.631C > T p.(Arg211Cys) variant had clinical features typical of Meier-Gorlin syndrome (MGS), while two siblings with compound heterozygous c.346delG p.(Asp116Ile*62) and c.1349A > G p.(Lys450Arg) variants presented with Seckel-like phenotype."
Establishes that a specific recurrent DONSON genotype produces a clinically typical Meier-Gorlin presentation, distinct from the Seckel-like presentation carried by other alleles in the same series.
DONSON-related Seckel-like phenotype
DONSON hgnc:2993 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in DONSON (hgnc:2993). hgnc:2993 is a gene from the HUGO Gene Nomenclature Committee.
A third recognized presentation, again without its own OMIM or ISDS row. Reported in siblings compound heterozygous for a frameshift and a missense allele. Listed here so that the allele-to-presentation correspondence is recorded rather than collapsed into the spectrum label.
Show evidence (1 reference)
PMID:31407851 SUPPORT Human Clinical
"two siblings with compound heterozygous c.346delG p.(Asp116Ile*62) and c.1349A > G p.(Lys450Arg) variants presented with Seckel-like phenotype"
The Seckel-like arm of the same four-family series.
?

Discussions and Knowledge Gaps

1
Are the CMG-assembly defect and the fork-protection defect two consequences of one molecular role for DONSON, or two separable functions? And which of them accounts for the phenotypic range from Meier-Gorlin syndrome to microcephaly-micromelia?
KNOWLEDGE GAP donson_two_mechanisms
Attached to
pathophysiology#Impaired CMG Helicase Assembly pathophysiology#Replication Fork Instability and Nucleolytic Collapse
The two mechanisms were established six years apart in different systems and have never been reconciled. Both are well evidenced, both would plausibly produce microcephalic dwarfism, and the entry curates them as parallel downstream nodes because nothing in the literature orders them. If the severity range across the DONSON spectrum tracks one mechanism more than the other, that would be the most useful thing to know about this gene, and it is not known.
⚙

Pathophysiology

4
Reduced DONSON Protein Level
Biallelic hypomorphic variants substantially reduce, but do not abolish, DONSON protein. The residual level matters: DONSON is essential for chromosome duplication, so only partial loss is compatible with development.
DONSON hgnc:2993 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves DONSON (hgnc:2993). hgnc:2993 is a gene from the HUGO Gene Nomenclature Committee.
Downstream
Impaired CMG Helicase Assembly
Replication Fork Instability and Nucleolytic Collapse
Show evidence (1 reference)
PMID:28191891 SUPPORT Human Clinical
"Hypomorphic mutations in DONSON substantially reduce DONSON protein levels and impair fork stability in cells from patients, consistent with defective DNA replication underlying the disease phenotype"
Quantifies the primary molecular lesion and links it to the disease.
Impaired CMG Helicase Assembly
DONSON binds directly but transiently to CDC45-MCM-GINS during S phase and is essential for assembling the helicase. It is dispensable for loading the MCM2-7 core onto chromatin in G1 - so the defect is specifically at the conversion of loaded MCM2-7 double hexamers into active CMG, not at licensing. This is the step that places DONSON alongside the twelve other Meier-Gorlin genes.
DNA replication initiation GO:0006270 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased DNA replication initiation (GO:0006270). GO:0006270 is a biological process from the Gene Ontology. ↓ DECREASED
CMG complex GO:0071162 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves CMG complex (GO:0071162). GO:0071162 is a cellular component from the Gene Ontology.
Downstream
Reduced Progenitor Proliferation and Prenatal Growth Failure
Show evidence (3 references)
PMID:37781960 SUPPORT In Vitro
"we show that DONSON binds directly but transiently to CDC45-MCM-GINS during S-phase and is essential for chromosome duplication"
Establishes the direct interaction and the essentiality.
PMID:37781960 SUPPORT In Vitro
"DONSON is dispensable for loading of the MCM2-7 helicase core onto chromatin during G1-phase, but instead is essential for CDC45-MCM-GINS assembly during S-phase"
Localizes the defect to helicase assembly rather than to origin licensing, which is the distinction this node draws.
PMID:37781960 SUPPORT In Vitro
"provide a molecular explanation for why mutations in human DONSON are associated with Meier-Gorlin syndrome"
Connects the assembly role to the Meier-Gorlin phenotype, which is what makes DONSON the thirteenth gene of that disorder.
Replication Fork Instability and Nucleolytic Collapse
The mechanism identified first, and distinct from the assembly defect: DONSON stabilizes forks during replication, and its loss causes severe replication-associated DNA damage arising from nucleolytic cleavage of stalled forks. ATR-dependent replication-stress signalling is also impaired, so checkpoint activity falls and chromosomal instability is potentiated - the cell both accumulates damage and fails to respond to it.
DNA damage checkpoint signaling GO:0000077 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased DNA damage checkpoint signaling (GO:0000077). GO:0000077 is a biological process from the Gene Ontology. ↓ DECREASED DNA replication GO:0006260 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal DNA replication (GO:0006260). GO:0006260 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Reduced Progenitor Proliferation and Prenatal Growth Failure
Show evidence (2 references)
PMID:28191891 SUPPORT In Vitro
"Loss of DONSON leads to severe replication-associated DNA damage arising from nucleolytic cleavage of stalled replication forks."
The fork-collapse mechanism, stated directly.
PMID:28191891 SUPPORT In Vitro
"ATR-dependent signaling in response to replication stress is impaired in DONSON-deficient cells, resulting in decreased checkpoint activity and the potentiation of chromosomal instability"
Documents the second arm - a failed damage response on top of the damage itself.
Reduced Progenitor Proliferation and Prenatal Growth Failure
The organism-level endpoint: prenatal-onset microcephaly with short stature and, at the more severe end, limb reduction. Mouse work supports a progenitor-depletion route to the microcephaly specifically - Donson is essential for progenitors of both cortical glutamatergic and GABAergic neurons.
cell population proliferation GO:0008283 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased cell population proliferation (GO:0008283). GO:0008283 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Microcephaly Cortical progenitor depletion is the demonstrated route in the conditional mouse deletion.
Proportionate short stature Reduced proliferation across tissues gives a proportionate rather than a disproportionate deficit.
Intrauterine growth restriction Prenatal arm of the proliferation deficit.
Slender long bones with delayed bone age Skeletal expression of reduced progenitor proliferation; the slender-bone radiographic pattern is what places the disorder in this nosology group.
Absent patellae Grouped with the Meier-Gorlin-like skeletal features; patellar development is selectively sensitive across the replication-licensing disorders, for reasons that remain unexplained.
Multiple joint dislocations Grouped with the other skeletal findings reported in the Meier-Gorlin-predominant presentation; no specific route is established.
Micromelia Limb reduction is the severe-end expression of the proliferation deficit; it co-segregates with the most extreme presentations.
Radial ray deficiency Radial ray formation is selectively sensitive, as it is across several replication-machinery disorders; the specific route is not established.
Show evidence (1 reference)
PMID:33739968 SUPPORT Model Organism
"Emx1-Cre-mediated Donson deletion in progenitors of cortical glutamatergic neurons caused extensive apoptosis in the early dorsomedial neuroepithelium, thus preventing formation of the neocortex and hippocampus."
A conditional mouse deletion showing that removing Donson from cortical progenitors kills them and prevents neocortex formation - the progenitor-depletion route to microcephaly this node asserts.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for DONSON-Related Microcephalic Primordial Dwarfism Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

10
Head and Neck 1
Microcephaly VERY_FREQUENT HP:0000252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28191891 SUPPORT Human Clinical
"report biallelic DONSON mutations in 29 individuals with microcephalic dwarfism"
Microcephaly is definitional for the cohort in which the gene was found.
Integument 1
Ichthyosis VERY_RARE HP:0008064 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ichthyosis (HP:0008064). HP:0008064 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35298084 SUPPORT Human Clinical
"There was abnormal posture due to spine and peripheral joint deformities, along with ichthyosis, facial, and digital dysmorphism."
A single reported case, presented by the authors as expanding the spectrum - hence PARTIAL and a VERY_RARE frequency.
Limbs 1
Micromelia OCCASIONAL HP:0002983 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Micromelia (HP:0002983). HP:0002983 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28191891 SUPPORT Human Clinical
"In family P21, the most extreme phenotype was observed, with substantial limb shortening/reduction in association with foetal lethality"
Documents limb shortening/reduction in the most severely affected DONSON family, the presentation for which the micromelia name was coined.
Growth 1
Intrauterine growth restriction FREQUENT Intrauterine growth retardation HP:0001511 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intrauterine growth retardation (HP:0001511). HP:0001511 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35298084 SUPPORT Human Clinical
"There was history of intrauterine growth restriction and collodion like skin abnormality at birth."
Prenatal onset in a DONSON-confirmed case.
Other 6
Proportionate short stature VERY_FREQUENT HP:0003508 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Proportionate short stature (HP:0003508). HP:0003508 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35298084 SUPPORT Human Clinical
"anthropometry was suggestive of proportionate short stature and microcephaly"
Documents proportionate short stature with microcephaly in a DONSON-confirmed case.
Slender long bones with delayed bone age FREQUENT HP:0003100 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Slender long bones, annotated with Slender long bone (HP:0003100). HP:0003100 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35298084 SUPPORT Human Clinical
"absent patellae, slender long bones with delayed bone age"
Radiographic findings in a DONSON-confirmed case.
Absent patellae OCCASIONAL Patellar aplasia HP:0006443 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Patellar aplasia (HP:0006443). HP:0006443 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35298084 SUPPORT Human Clinical
"bilateral knee joint dislocation, absent patellae, slender long bones with delayed bone age"
Absent patellae in a DONSON-confirmed Meier-Gorlin-predominant case.
Multiple joint dislocations OCCASIONAL HP:0012095 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Multiple joint dislocation (HP:0012095). HP:0012095 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35298084 SUPPORT Human Clinical
"Skeletal radiographs showed radial subluxation, acetabular dysplasia and hip dislocation, bilateral knee joint dislocation"
Documents the multiple joint dislocations that expanded the reported phenotype.
Radial ray deficiency OCCASIONAL HP:0006433 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Radial ray deficiency (HP:0006433). HP:0006433 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28191891 SUPPORT Human Clinical
"Notably, patient P19 had bilateral hypoplasia of the radius and thumb, which, together with the limb abnormalities displayed by P13-1 and 13-2, established radial ray defects as an uncommon but recurrent phenotype."
States directly that radial ray defects recur across the cohort while remaining uncommon, which is the frequency curated here.
Normal intellect OCCASIONAL
Show evidence (1 reference)
PMID:35298084 SUPPORT Human Clinical
"She had normal developmental milestones and intellect."
States the preserved-intellect finding directly. Curated as SUPPORT for the claim as written; it refutes only the separate assumption that microcephaly in this disorder implies intellectual disability.
🧬

Genetic Associations

1
DONSON
Gene: DONSON hgnc:2993 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is DONSON (hgnc:2993). hgnc:2993 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE variant_origin: GERMLINE
Show evidence (2 references)
PMID:28191891 SUPPORT Human Clinical
"Hypomorphic mutations in DONSON substantially reduce DONSON protein levels and impair fork stability in cells from patients"
Characterizes the disease alleles as hypomorphic and links them to the cellular defect.
PMID:35298084 SUPPORT Human Clinical
"Whole exome sequencing revealed a pathogenic homozygous variant c.C1297T (p.Pro433Ser) in the exon 8 of DONSON gene."
A specific recurrent allele, in a case presenting at the Meier-Gorlin end of the spectrum.
🔬

Diagnosis

1
Molecular genetic testing of DONSON (Biallelic hypomorphic DONSON variants)
There is no clinical criterion set, and there could not usefully be one: the same gene presents as microcephaly-micromelia syndrome, MISSLA, Meier-Gorlin syndrome, a Seckel-like phenotype, and in one instance Femoral-Facial syndrome, so the clinical label a patient arrives with does not predict the gene and the gene does not predict the label. Sequencing reached the diagnosis in every reported case. Two practical points: the variants are hypomorphic rather than null, so a result should not be dismissed for retaining residual protein; and while biallelic inheritance is the rule, a de novo heterozygous variant has been reported.
molecular genetic testing NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (2 references)
PMID:31407851 SUPPORT Human Clinical
"We identified four unrelated families with five affected individuals having biallelic or de novo variants in DONSON presenting with a core phenotype of severe short stature (z score < -3 SD), additional skeletal abnormalities, and microcephaly."
Establishes the core phenotype that prompts testing, and that both biallelic and de novo variants are found.
PMID:31407851 SUPPORT Human Clinical
"Here we describe novel biallelic and de novo variants that are associated with MGS, Seckel-like phenotype and FFS, the last of which has not been associated with any disease gene to date."
The range of clinical labels a DONSON result can sit under, which is why the diagnosis is molecular rather than clinical.
📊

Prevalence

1
Worldwide
Cases In Literature Not yet documented
No population rate published. Twenty-nine individuals with microcephalic dwarfism were reported in the gene-discovery study, drawn from a screen of over 250 patients, which the authors describe as making DONSON a common cause of microcephalic dwarfism relative to other genes in this group.
Show evidence (1 reference)
PMID:28191891 SUPPORT Human Clinical
"we identify downstream neighbor of SON (DONSON) as a novel fork protection factor and report biallelic DONSON mutations in 29 individuals with microcephalic dwarfism"
Gives the cohort size behind the gene discovery.
{ }

Source YAML

click to show 
name: DONSON-Related Microcephalic Primordial Dwarfism
creation_date: "2026-08-27T04:30:00Z"
category: Mendelian
synonyms:
- DONSON-related microcephaly-short stature-limb abnormalities spectrum
- microcephaly-micromelia syndrome
- MIMIS
- microcephaly, short stature, and limb abnormalities
- MISSLA
- DONSON-related Meier-Gorlin syndrome
description: >-
  Biallelic DONSON variants cause a spectrum of microcephalic primordial
  dwarfism that the literature has named three times over:
  microcephaly-micromelia syndrome, microcephaly with short stature and limb
  abnormalities
  (MISSLA), and Meier-Gorlin syndrome - reflecting which cohort the patients
  were ascertained in rather than three distinct diseases. DONSON is a
  replisome component. Its function was established in two stages: first as a
  replication fork protection factor whose loss causes nucleolytic cleavage of
  stalled forks and impaired ATR-dependent replication-stress signalling, and
  later, unexpectedly, as an essential assembly factor for the CDC45-MCM-GINS
  (CMG) helicase during S phase. That second finding is what makes DONSON the
  thirteenth Meier-Gorlin gene: the other twelve encode CMG subunits or
  established CMG assembly factors, and DONSON turned out to belong to the same
  process despite having no orthologue in budding yeast, where replication
  initiation can be reconstituted without it.
disease_term:
  preferred_term: DONSON-related microcephaly-short stature-limb abnormalities spectrum
  term:
    id: MONDO:0035534
    label: DONSON-related microcephaly-short stature-limb abnormalities spectrum
parents:
- Autosomal recessive disease
- Primordial dwarfism
has_subtypes:
- name: MMS
  subtype_term:
    preferred_term: microcephaly-micromelia syndrome
    term:
      id: MONDO:0009619
      label: microcephaly-micromelia syndrome
  display_name: Microcephaly-micromelia syndrome (MMS)
  description: >-
    The severe end of the spectrum, named for the limb reduction that
    distinguishes it. Prenatally lethal or near-lethal in the most affected
    families. Corresponds to OMIM 251230; it and MISSLA share the single ISDS
    row NOS 21-0200.
  genes:
  - preferred_term: DONSON
    term:
      id: hgnc:2993
      label: DONSON
- name: MISSLA
  subtype_term:
    preferred_term: microcephaly, short stature, and limb abnormalities
    term:
      id: MONDO:0060533
      label: microcephaly, short stature, and limb abnormalities
  display_name: Microcephaly, short stature, and limb abnormalities (MISSLA)
  description: >-
    The survivable presentation, with microcephaly and severe short stature
    alongside variable and generally milder limb findings - radial ray defects
    rather than limb reduction. Corresponds to OMIM 617604.
  genes:
  - preferred_term: DONSON
    term:
      id: hgnc:2993
      label: DONSON
- name: MGS-like
  display_name: DONSON-related Meier-Gorlin syndrome
  description: >-
    Neither an OMIM entry nor an ISDS row - a presentation, not a separate
    entity. Two apparently unrelated families homozygous for
    c.631C>T p.(Arg211Cys) had clinically typical Meier-Gorlin syndrome, and
    DONSON's later-established role in CMG helicase assembly explains why. No
    MONDO leaf exists for the DONSON-specific form, so this subtype carries no
    subtype_term; dismech also lists DONSON as a Meier-Gorlin gene in
    kb/disorders/Meier-Gorlin_Syndrome.yaml.
  genes:
  - preferred_term: DONSON
    term:
      id: hgnc:2993
      label: DONSON
  evidence:
  - reference: PMID:31407851
    reference_title: "Biallelic and De Novo Variants in DONSON Reveal a Clinical Spectrum of Cell Cycle-opathies with Microcephaly, Dwarfism and Skeletal Abnormalities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two apparently unrelated families with identical homozygous c.631C > T p.(Arg211Cys) variant had clinical features typical of Meier-Gorlin syndrome (MGS), while two siblings with compound heterozygous c.346delG p.(Asp116Ile*62) and c.1349A > G p.(Lys450Arg) variants presented with Seckel-like phenotype."
    explanation: >-
      Establishes that a specific recurrent DONSON genotype produces a
      clinically typical Meier-Gorlin presentation, distinct from the
      Seckel-like presentation carried by other alleles in the same series.
- name: Seckel-like
  display_name: DONSON-related Seckel-like phenotype
  description: >-
    A third recognized presentation, again without its own OMIM or ISDS row.
    Reported in siblings compound heterozygous for a frameshift and a missense
    allele. Listed here so that the allele-to-presentation correspondence is
    recorded rather than collapsed into the spectrum label.
  genes:
  - preferred_term: DONSON
    term:
      id: hgnc:2993
      label: DONSON
  evidence:
  - reference: PMID:31407851
    reference_title: "Biallelic and De Novo Variants in DONSON Reveal a Clinical Spectrum of Cell Cycle-opathies with Microcephaly, Dwarfism and Skeletal Abnormalities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "two siblings with compound heterozygous c.346delG p.(Asp116Ile*62) and c.1349A > G p.(Lys450Arg) variants presented with Seckel-like phenotype"
    explanation: >-
      The Seckel-like arm of the same four-family series.
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
  isds_skeletal_category:
  - classification_value: primordial_dwarfism_and_slender_bones
    notes: >-
      ISDS Nosology of Genetic Skeletal Disorders, 2023 revision (Unger et al.,
      PMID:36779427), group 21 "Primordial dwarfism and slender bone
      dysplasias", NOS 21-0200 "Microcephalic osteodysplastic primordial
      dwarfism, or microcephaly-short stature-micromelia-limb abnormalities,
      DONSON-related" (AR, OMIM 251230 and 617604). The row itself already lumps
      two published entities under one heading, which is why this entry is bound
      to the MONDO spectrum term rather than to either leaf. Note that the
      DONSON-Meier-Gorlin association is not represented in that row: it
      postdates the table's close, and dismech curates DONSON as a
      Meier-Gorlin gene in kb/disorders/Meier-Gorlin_Syndrome.yaml. Both
      placements sit in group 21, so nothing about the classification turns on
      which name is used.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: NOT_YET_DOCUMENTED
  notes: >-
    No population rate published. Twenty-nine individuals with microcephalic
    dwarfism were reported in the gene-discovery study, drawn from a screen of
    over 250 patients, which the authors describe as making DONSON a common
    cause of microcephalic dwarfism relative to other genes in this group.
  evidence:
  - reference: PMID:28191891
    reference_title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identify downstream neighbor of SON (DONSON) as a novel fork protection factor and report biallelic DONSON mutations in 29 individuals with microcephalic dwarfism"
    explanation: >-
      Gives the cohort size behind the gene discovery.
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Biallelic hypomorphic DONSON variants, homozygous or compound heterozygous.
    Complete loss would be expected to be lethal, since DONSON is essential for
    chromosome duplication.
  evidence:
  - reference: PMID:28191891
    reference_title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All variants segregated amongst family members in a manner consistent with an autosomal recessive trait"
    explanation: >-
      Segregation across the discovery families establishes recessive
      inheritance.
genetic:
- name: DONSON
  gene_term:
    preferred_term: DONSON
    term:
      id: hgnc:2993
      label: DONSON
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    DONSON (21q22.11, "Downstream neighbour of SON") encodes a replisome
    component. Disease alleles are hypomorphic and substantially reduce DONSON
    protein levels rather than abolishing them; a recurrent homozygous
    c.1297C>T (p.Pro433Ser) has been reported in a Meier-Gorlin-predominant
    presentation.
  evidence:
  - reference: PMID:28191891
    reference_title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypomorphic mutations in DONSON substantially reduce DONSON protein levels and impair fork stability in cells from patients"
    explanation: >-
      Characterizes the disease alleles as hypomorphic and links them to the
      cellular defect.
  - reference: PMID:35298084
    reference_title: "Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whole exome sequencing revealed a pathogenic homozygous variant c.C1297T (p.Pro433Ser) in the exon 8 of DONSON gene."
    explanation: >-
      A specific recurrent allele, in a case presenting at the Meier-Gorlin end
      of the spectrum.
pathophysiology:
- name: Reduced DONSON Protein Level
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    Biallelic hypomorphic variants substantially reduce, but do not abolish,
    DONSON protein. The residual level matters: DONSON is essential for
    chromosome duplication, so only partial loss is compatible with development.
  genes:
  - preferred_term: DONSON
    term:
      id: hgnc:2993
      label: DONSON
  downstream:
  - target: Impaired CMG Helicase Assembly
  - target: Replication Fork Instability and Nucleolytic Collapse
  evidence:
  - reference: PMID:28191891
    reference_title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypomorphic mutations in DONSON substantially reduce DONSON protein levels and impair fork stability in cells from patients, consistent with defective DNA replication underlying the disease phenotype"
    explanation: >-
      Quantifies the primary molecular lesion and links it to the disease.
- name: Impaired CMG Helicase Assembly
  biological_scale: MOLECULAR
  description: >-
    DONSON binds directly but transiently to CDC45-MCM-GINS during S phase and
    is essential for assembling the helicase. It is dispensable for loading the
    MCM2-7 core onto chromatin in G1 - so the defect is specifically at the
    conversion of loaded MCM2-7 double hexamers into active CMG, not at
    licensing. This is the step that places DONSON alongside the twelve other
    Meier-Gorlin genes.
  cellular_components:
  - preferred_term: CMG complex
    term:
      id: GO:0071162
      label: CMG complex
  biological_processes:
  - preferred_term: DNA replication initiation
    term:
      id: GO:0006270
      label: DNA replication initiation
    modifier: DECREASED
  downstream:
  - target: Reduced Progenitor Proliferation and Prenatal Growth Failure
  evidence:
  - reference: PMID:37781960
    reference_title: "DONSON is required for CMG helicase assembly in the mammalian cell cycle."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we show that DONSON binds directly but transiently to CDC45-MCM-GINS during S-phase and is essential for chromosome duplication"
    explanation: >-
      Establishes the direct interaction and the essentiality.
  - reference: PMID:37781960
    reference_title: "DONSON is required for CMG helicase assembly in the mammalian cell cycle."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "DONSON is dispensable for loading of the MCM2-7 helicase core onto chromatin during G1-phase, but instead is essential for CDC45-MCM-GINS assembly during S-phase"
    explanation: >-
      Localizes the defect to helicase assembly rather than to origin licensing,
      which is the distinction this node draws.
  - reference: PMID:37781960
    reference_title: "DONSON is required for CMG helicase assembly in the mammalian cell cycle."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "provide a molecular explanation for why mutations in human DONSON are associated with Meier-Gorlin syndrome"
    explanation: >-
      Connects the assembly role to the Meier-Gorlin phenotype, which is what
      makes DONSON the thirteenth gene of that disorder.
- name: Replication Fork Instability and Nucleolytic Collapse
  biological_scale: CELLULAR
  description: >-
    The mechanism identified first, and distinct from the assembly defect:
    DONSON stabilizes forks during replication, and its loss causes severe
    replication-associated DNA damage arising from nucleolytic cleavage of
    stalled forks. ATR-dependent replication-stress signalling is also impaired,
    so checkpoint activity falls and chromosomal instability is potentiated -
    the cell both accumulates damage and fails to respond to it.
  biological_processes:
  - preferred_term: DNA damage checkpoint signaling
    term:
      id: GO:0000077
      label: DNA damage checkpoint signaling
    modifier: DECREASED
  - preferred_term: DNA replication
    term:
      id: GO:0006260
      label: DNA replication
    modifier: ABNORMAL
  downstream:
  - target: Reduced Progenitor Proliferation and Prenatal Growth Failure
  evidence:
  - reference: PMID:28191891
    reference_title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Loss of DONSON leads to severe replication-associated DNA damage arising from nucleolytic cleavage of stalled replication forks."
    explanation: >-
      The fork-collapse mechanism, stated directly.
  - reference: PMID:28191891
    reference_title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "ATR-dependent signaling in response to replication stress is impaired in DONSON-deficient cells, resulting in decreased checkpoint activity and the potentiation of chromosomal instability"
    explanation: >-
      Documents the second arm - a failed damage response on top of the damage
      itself.
- name: Reduced Progenitor Proliferation and Prenatal Growth Failure
  biological_scale: ORGANISM
  role: consequence
  description: >-
    The organism-level endpoint: prenatal-onset microcephaly with short stature
    and, at the more severe end, limb reduction. Mouse work supports a
    progenitor-depletion route to the microcephaly specifically - Donson is
    essential for progenitors of both cortical glutamatergic and GABAergic
    neurons.
  biological_processes:
  - preferred_term: cell population proliferation
    term:
      id: GO:0008283
      label: cell population proliferation
    modifier: DECREASED
  downstream:
  - target: Microcephaly
    description: >-
      Cortical progenitor depletion is the demonstrated route in the
      conditional mouse deletion.
  - target: Proportionate short stature
    description: >-
      Reduced proliferation across tissues gives a proportionate rather than a
      disproportionate deficit.
  - target: Intrauterine growth restriction
    description: >-
      Prenatal arm of the proliferation deficit.
  - target: Slender long bones with delayed bone age
    description: >-
      Skeletal expression of reduced progenitor proliferation; the
      slender-bone radiographic pattern is what places the disorder in this nosology
      group.
  - target: Absent patellae
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Grouped with the Meier-Gorlin-like skeletal features; patellar
      development is selectively sensitive across the replication-licensing
      disorders, for reasons that remain unexplained.
  - target: Multiple joint dislocations
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Grouped with the other skeletal findings reported in the
      Meier-Gorlin-predominant presentation; no specific route is established.
  - target: Micromelia
    description: >-
      Limb reduction is the severe-end expression of the proliferation
      deficit; it co-segregates with the most extreme presentations.
  - target: Radial ray deficiency
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Radial ray formation is selectively sensitive, as it is across several
      replication-machinery disorders; the specific route is not established.
  evidence:
  - reference: PMID:33739968
    reference_title: "The microcephaly gene Donson is essential for progenitors of cortical glutamatergic and GABAergic neurons."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Emx1-Cre-mediated Donson deletion in progenitors of cortical glutamatergic neurons caused extensive apoptosis in the early dorsomedial neuroepithelium, thus preventing formation of the neocortex and hippocampus."
    explanation: >-
      A conditional mouse deletion showing that removing Donson from cortical
      progenitors kills them and prevents neocortex formation - the
      progenitor-depletion route to microcephaly this node asserts.
phenotypes:
- category: Neurological
  name: Microcephaly
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  frequency: VERY_FREQUENT
  diagnostic: true
  evidence:
  - reference: PMID:28191891
    reference_title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "report biallelic DONSON mutations in 29 individuals with microcephalic dwarfism"
    explanation: >-
      Microcephaly is definitional for the cohort in which the gene was found.
- category: Growth
  name: Proportionate short stature
  phenotype_term:
    preferred_term: Proportionate short stature
    term:
      id: HP:0003508
      label: Proportionate short stature
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:35298084
    reference_title: "Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "anthropometry was suggestive of proportionate short stature and microcephaly"
    explanation: >-
      Documents proportionate short stature with microcephaly in a
      DONSON-confirmed case.
- category: Growth
  name: Intrauterine growth restriction
  phenotype_term:
    preferred_term: Intrauterine growth retardation
    term:
      id: HP:0001511
      label: Intrauterine growth retardation
  frequency: FREQUENT
  evidence:
  - reference: PMID:35298084
    reference_title: "Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There was history of intrauterine growth restriction and collodion like skin abnormality at birth."
    explanation: >-
      Prenatal onset in a DONSON-confirmed case.
- category: Skeletal
  name: Slender long bones with delayed bone age
  phenotype_term:
    preferred_term: Slender long bones
    term:
      id: HP:0003100
      label: Slender long bone
  frequency: FREQUENT
  description: >-
    The radiographic feature that places this disorder in the slender-bones half
    of ISDS group 21.
  evidence:
  - reference: PMID:35298084
    reference_title: "Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "absent patellae, slender long bones with delayed bone age"
    explanation: >-
      Radiographic findings in a DONSON-confirmed case.
- category: Skeletal
  name: Absent patellae
  phenotype_term:
    preferred_term: Patellar aplasia
    term:
      id: HP:0006443
      label: Patellar aplasia
  frequency: OCCASIONAL
  description: >-
    Part of what makes some DONSON presentations read as Meier-Gorlin syndrome,
    whose historical name was "ear-patella-short stature syndrome".
  evidence:
  - reference: PMID:35298084
    reference_title: "Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "bilateral knee joint dislocation, absent patellae, slender long bones with delayed bone age"
    explanation: >-
      Absent patellae in a DONSON-confirmed Meier-Gorlin-predominant case.
- category: Skeletal
  name: Multiple joint dislocations
  phenotype_term:
    preferred_term: Multiple joint dislocation
    term:
      id: HP:0012095
      label: Multiple joint dislocation
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:35298084
    reference_title: "Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Skeletal radiographs showed radial subluxation, acetabular dysplasia and hip dislocation, bilateral knee joint dislocation"
    explanation: >-
      Documents the multiple joint dislocations that expanded the reported
      phenotype.
- category: Skeletal
  name: Micromelia
  phenotype_term:
    preferred_term: Micromelia
    term:
      id: HP:0002983
      label: Micromelia
  frequency: OCCASIONAL
  description: >-
    Limb shortening/reduction sits at the severe end of the DONSON spectrum and
    is what the "microcephaly-micromelia syndrome" name refers to. In the
    discovery cohort it was seen in the single most severely affected family,
    where it accompanied fetal lethality; milder presentations carry no
    micromelia at all, which is why the frequency here is occasional across the
    spectrum rather than definitional.
  evidence:
  - reference: PMID:28191891
    reference_title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In family P21, the most extreme phenotype was observed, with substantial limb shortening/reduction in association with foetal lethality"
    explanation: >-
      Documents limb shortening/reduction in the most severely affected
      DONSON family, the presentation for which the micromelia name was coined.
- category: Skeletal
  name: Radial ray deficiency
  phenotype_term:
    preferred_term: Radial ray deficiency
    term:
      id: HP:0006433
      label: Radial ray deficiency
  frequency: OCCASIONAL
  description: >-
    A recurrent but uncommon limb finding, distinct from generalized micromelia:
    the radius and thumb are selectively affected.
  evidence:
  - reference: PMID:28191891
    reference_title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Notably, patient P19 had bilateral hypoplasia of the radius and thumb, which, together with the limb abnormalities displayed by P13-1 and 13-2, established radial ray defects as an uncommon but recurrent phenotype."
    explanation: >-
      States directly that radial ray defects recur across the cohort while
      remaining uncommon, which is the frequency curated here.
- category: Integumentary
  name: Ichthyosis
  phenotype_term:
    preferred_term: Ichthyosis
    term:
      id: HP:0008064
      label: Ichthyosis
  frequency: VERY_RARE
  description: >-
    Reported in a single case as a phenotype expansion; not part of the core
    presentation.
  evidence:
  - reference: PMID:35298084
    reference_title: "Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There was abnormal posture due to spine and peripheral joint deformities, along with ichthyosis, facial, and digital dysmorphism."
    explanation: >-
      A single reported case, presented by the authors as expanding the
      spectrum - hence PARTIAL and a VERY_RARE frequency.
- category: Neurological
  name: Normal intellect
  phenotype_term:
    preferred_term: Normal developmental milestones and intellect
  frequency: OCCASIONAL
  description: >-
    Recorded as a negative finding. Despite the microcephaly, developmental
    milestones and intellect were normal in the reported Meier-Gorlin-predominant
    case - so microcephaly here should not be assumed to imply intellectual
    disability. Deliberately left unbound: HPO has no term for normal intellect,
    and the nearest class term (HP:0012759 Neurodevelopmental abnormality)
    asserts the opposite of the claim, so binding it would make the entry say
    the reverse of its own source. Needs term.
  evidence:
  - reference: PMID:35298084
    reference_title: "Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She had normal developmental milestones and intellect."
    explanation: >-
      States the preserved-intellect finding directly. Curated as SUPPORT for
      the claim as written; it refutes only the separate assumption that
      microcephaly in this disorder implies intellectual disability.
diagnosis:
- name: Molecular genetic testing of DONSON
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  presence: Biallelic hypomorphic DONSON variants
  description: >-
    There is no clinical criterion set, and there could not usefully be one:
    the same gene presents as microcephaly-micromelia syndrome, MISSLA,
    Meier-Gorlin syndrome, a Seckel-like phenotype, and in one instance
    Femoral-Facial syndrome, so the clinical label a patient arrives with does
    not predict the gene and the gene does not predict the label. Sequencing
    reached the diagnosis in every reported case. Two practical points: the
    variants are hypomorphic rather than null, so a result should not be
    dismissed for retaining residual protein; and while biallelic inheritance
    is the rule, a de novo heterozygous variant has been reported.
  evidence:
  - reference: PMID:31407851
    reference_title: "Biallelic and De Novo Variants in DONSON Reveal a Clinical Spectrum of Cell Cycle-opathies with Microcephaly, Dwarfism and Skeletal Abnormalities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified four unrelated families with five affected individuals having biallelic or de novo variants in DONSON presenting with a core phenotype of severe short stature (z score < -3 SD), additional skeletal abnormalities, and microcephaly."
    explanation: >-
      Establishes the core phenotype that prompts testing, and that both
      biallelic and de novo variants are found.
  - reference: PMID:31407851
    reference_title: "Biallelic and De Novo Variants in DONSON Reveal a Clinical Spectrum of Cell Cycle-opathies with Microcephaly, Dwarfism and Skeletal Abnormalities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we describe novel biallelic and de novo variants that are associated with MGS, Seckel-like phenotype and FFS, the last of which has not been associated with any disease gene to date."
    explanation: >-
      The range of clinical labels a DONSON result can sit under, which is why
      the diagnosis is molecular rather than clinical.
discussions:
- discussion_id: donson_two_mechanisms
  kind: KNOWLEDGE_GAP
  attaches_to:
  - pathophysiology#Impaired CMG Helicase Assembly
  - pathophysiology#Replication Fork Instability and Nucleolytic Collapse
  prompt: >-
    Are the CMG-assembly defect and the fork-protection defect two consequences
    of one molecular role for DONSON, or two separable functions? And which of
    them accounts for the phenotypic range from Meier-Gorlin syndrome to
    microcephaly-micromelia?
  rationale: >-
    The two mechanisms were established six years apart in different systems and
    have never been reconciled. Both are well evidenced, both would plausibly
    produce microcephalic dwarfism, and the entry curates them as parallel
    downstream nodes because nothing in the literature orders them. If the
    severity range across the DONSON spectrum tracks one mechanism more than the
    other, that would be the most useful thing to know about this gene, and it
    is not known.
references:
- reference: PMID:28191891
  title: "Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism."
- reference: PMID:37781960
  title: "DONSON is required for CMG helicase assembly in the mammalian cell cycle."
- reference: PMID:37638758
  title: "DONSON facilitates Cdc45 and GINS chromatin association and is essential for DNA replication initiation."
- reference: PMID:33739968
  title: "The microcephaly gene Donson is essential for progenitors of cortical glutamatergic and GABAergic neurons."
- reference: PMID:31407851
  title: "Biallelic and De Novo Variants in DONSON Reveal a Clinical Spectrum of Cell Cycle-opathies with Microcephaly, Dwarfism and Skeletal Abnormalities."
- reference: PMID:35298084
  title: "Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum."
📚

References & Deep Research

References

6
PMID:28191891
Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism.
No top-level findings curated for this source.
PMID:37781960
DONSON is required for CMG helicase assembly in the mammalian cell cycle.
No top-level findings curated for this source.
PMID:37638758
DONSON facilitates Cdc45 and GINS chromatin association and is essential for DNA replication initiation.
No top-level findings curated for this source.
PMID:33739968
The microcephaly gene Donson is essential for progenitors of cortical glutamatergic and GABAergic neurons.
No top-level findings curated for this source.
PMID:31407851
Biallelic and De Novo Variants in DONSON Reveal a Clinical Spectrum of Cell Cycle-opathies with Microcephaly, Dwarfism and Skeletal Abnormalities.
No top-level findings curated for this source.
PMID:35298084
Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum.
No top-level findings curated for this source.

Deep Research

1
Claude Code ▸
DONSON-Related Microcephalic Primordial Dwarfism: Comprehensive Research Report
claude-haiku-4-5-20251001, claude-sonnet-5 22 citations 2026-08-27T04:38:50.384310

DONSON-Related Microcephalic Primordial Dwarfism: Comprehensive Research Report

1. Disease Information

Overview. DONSON-related disorder is a rare, autosomal recessive (with rare de novo cases) microcephalic primordial dwarfism (MPD) caused by biallelic (or, uncommonly, de novo monoallelic) hypomorphic variants in DONSON (Downstream Neighbor Of SON), a gene encoding an essential replisome/replication-initiation factor. Because complete loss of DONSON is embryonic lethal, all disease-causing alleles identified to date are partial loss-of-function ("hypomorphic") — no patient carries a biallelic combination of two complete null (nonsense/frameshift) alleles (PMID:28191891). The disorder spans a clinical continuum rather than a single discrete syndrome, ranging from prenatally/perinatally lethal microcephaly-micromelia syndrome (MIMIS) at the severe end, through Meier-Gorlin syndrome (MGS)-like and Seckel-syndrome-like presentations, to the comparatively milder microcephaly, short stature, and limb abnormalities (MISSLA) phenotype, plus rare femoral-facial syndrome (FFS)-like presentations (PMID:31407851; PMC6528082).

Key identifiers: - Gene: DONSON, HGNC:2993, chromosome 21q22.11, UniProt Q9NYP3, protein "DNA replication fork stabilization factor DONSON" (566 aa, ~62.7 kDa, 10 coding exons; transcript NM_017613) - OMIM gene: 611428 (DOWNSTREAM NEIGHBOR OF SON; DONSON) - OMIM phenotypes: - #617604 — Microcephaly, Short Stature, and Limb Abnormalities (MISSLA) - #251230 — Microcephaly-Micromelia Syndrome (MIMIS) - Additional overlapping entries for Meier-Gorlin syndrome and Seckel-like presentations attributed to DONSON - Orphanet: ORPHA:572768 (Microcephaly-micromelia syndrome); ORPHA:572773 (Microcephaly-short stature-limb abnormalities syndrome); gene page "DONSON — DNA replication fork stabilization factor DONSON" (orpha.net) - MONDO: parent grouping term MONDO:0017950 (microcephalic primordial dwarfism); disease-specific MONDO terms map to the MISSLA/MIMIS/MGS-DONSON entries - GARD/NIH: "DONSON-related microcephaly-short stature-limb abnormalities spectrum" (rarediseases.info.nih.gov/diseases/22314) - Data is derived from aggregated case series and pedigrees* (exome/genome sequencing cohorts of families with microcephalic dwarfism), not large EHR-scale registries — the total published patient count across all DONSON-related phenotypes is on the order of 40–50 individuals as of the most recent literature.

Synonyms: DONSON deficiency; DONSON-related microcephalic primordial dwarfism; DONSON-related cell cycle-opathy; Meier-Gorlin syndrome 8 / DONSON-related MGS; Seckel-like syndrome (DONSON-related); Microcephaly-Micromelia Syndrome (MIMIS); Microcephaly, Short Stature and Limb Abnormalities (MISSLA); DONSON-related femoral-facial syndrome.

2. Etiology

Causal factor: Purely genetic/molecular — biallelic hypomorphic pathogenic variants in DONSON impairing (but not abolishing) its replisome function. A minority of reported cases are compound heterozygous with one de novo allele (PMC6936249).

Genetic risk factors: - Missense, splice-site, small indel/frameshift, and non-coding (deep intronic, promoter/UTR) variants have all been reported. Critically, no patient has two complete null alleles — this genotype is presumed embryonic lethal, consistent with mouse knockout data (see §15) (PMID:28191891). - A recurrent homozygous missense variant, c.631C>T p.(Arg211Cys), has been independently identified in unrelated families with the Meier-Gorlin phenotype, suggesting either a mutational hotspot or a shared ancestral/founder allele in some populations (PMC6936249; recent Turkish-family case report, PMID:41612845). - A recurrent K489T substitution and a noncoding variant disrupting exon 4/5 splicing have also been described as causing exon skipping and nonsense-mediated decay or post-transcriptional destabilization of DONSON protein (PMID:28191891; PMC5538549 — the noncoding "genome-and-transcriptome sequencing" MIMIS discovery). - Genotype–phenotype correlation: variants affecting exon 4 have been associated with the milder MGS/FFS end of the spectrum, whereas frameshift variants and those in exons 5–10 correlate with more severe microcephaly and developmental impairment (PMC6936249). - Variants are rare in population databases (reported at <0.5% frequency in ExAC in the original description; no specific carrier-frequency or founder-population data were identified in this search beyond the shared p.Arg211Cys recurrence).

Environmental/other risk factors: None established; this is a purely monogenic disorder with no known environmental, infectious, or lifestyle contributory factors.

Protective factors: None reported.

Gene-environment interactions: Not applicable/not reported.

3. Phenotypes

The DONSON phenotypic spectrum shares a common "core" triad — profound microcephaly, growth restriction, and skeletal anomalies — of variable severity:

Phenotype HPO term (suggested) Notes
Severe microcephaly (often congenital/prenatal-onset) HP:0000252 (Microcephaly) / HP:0011451 (Congenital microcephaly) Reported mean head circumference −7.5 ± 2.4 SD in the original 29-patient cohort — disproportionately more severe than height deficit (PMID:28191891)
Intrauterine growth restriction / short stature HP:0001511 (IUGR) / HP:0004322 (Short stature) Height −3.2 ± 1.4 SD in the milder cohort; as severe as −6 SD head circumference vs −3 SD height in MISSLA (OMIM:617604)
Reduced cerebral cortical volume / simplified gyration HP:0002506 (Simplified gyral pattern) / HP:0012340 (Abnormal cerebral cortex morphology) Reduced gyral folding on imaging
Hypoplastic/absent corpus callosum (severe end) HP:0002079 / HP:0006989 Reported in MIMIS fetuses (PMC5538549)
Craniosynostosis HP:0001363 Seen in severe MIMIS cases
Triangular facies, micrognathia/microretrognathia, small dysplastic ears HP:0000325 (Triangular face) / HP:0000347 (Micrognathia) / HP:0008551 (Microtia) Classic MGS-like facial gestalt
Small anterior fontanel, high forehead HP:0000267 / HP:0000348 MISSLA-specific dysmorphism
Absent/hypoplastic patellae HP:0003308 (Aplasia/Hypoplasia of the patella) Core MGS feature
Radial ray defects: thumb hypo/aplasia, radial head dislocation, proximally implanted thumbs HP:0009601 / HP:0009775 Recurrent skeletal finding across the spectrum
Clinodactyly, syndactyly, brachydactyly HP:0030084 / HP:0001159 / HP:0009824
Micromelia / limb malformation (severe end, MIMIS) HP:0002983 Prenatal-onset, can be lethal
Femoral hypoplasia (femoral-facial syndrome variant) HP:0005630 First gene association for FFS reported in Kim/Karaca 2019 (PMC6936249)
Mild intellectual disability / poor speech acquisition HP:0001256 / HP:0000750 Present in milder survivors (MISSLA)
Hypopigmented skin lesions HP:0001010 Reported as a novel, previously unreported finding in one MGS patient
Sparse scalp hair/eyebrows, long eyelashes, thick vermilion of lips HP:0002286 / HP:0045075 / HP:0012471 MISSLA facial features

Onset: Prenatal (severe end — detectable IUGR and microcephaly on antenatal ultrasound) through neonatal presentation for milder forms.

Severity/progression: Static/non-progressive congenital malformation and growth pattern once established (not a degenerative disease), but growth deficiency and microcephaly are lifelong. Severity is graded along the described spectrum from perinatally lethal MIMIS to milder, non-lethal MISSLA/MGS-like presentations with survival into childhood/adulthood.

Quality of life: Limited direct QoL data; morbidity relates to short stature, skeletal deformity, and (in a subset) mild intellectual disability affecting educational/functional outcomes. No specific EQ-5D/SF-36 data identified.

4. Genetic / Molecular Information

  • Causal gene: DONSON (HGNC:2993, OMIM *611428), chromosome 21q22.11.
  • Variant classes observed: missense, nonsense, frameshift, canonical and non-canonical splice-site variants, and at least one deep intronic/regulatory noncoding variant causing aberrant splicing (identified via combined genome+transcriptome sequencing in a MIMIS family; PMC5538549).
  • ACMG classification: Reported variants are generally classified pathogenic/likely pathogenic in ClinVar (e.g., NM_017613.4:c.1466A>C p.(Lys489Thr); c.82A>C p.(Ser28Arg)) in the context of biallelic inheritance.
  • Functional consequence: All disease variants are hypomorphic (partial loss of function) rather than complete null — consistent with the embryonic lethality of complete DONSON loss. Mechanisms of hypomorphism include: exon skipping leading to partial nonsense-mediated decay, post-transcriptional protein destabilization (e.g., the K489T variant), subcellular mislocalization, and reduced ability to rescue replication defects in functional assays (e.g., R217C severely impairs function while M463T remains largely functional in complementation assays) (PMID:28191891; academic.oup.com/nar/51/18/9748).
  • Inheritance: Autosomal recessive in the great majority of cases; rare compound heterozygous cases include one de novo allele (e.g., the femoral-facial syndrome patient with de novo c.683G>T p.(Trp228Leu)) (PMC6936249).
  • Modifier genes: None specifically established.
  • Epigenetics: No disease-specific epigenetic (DNA methylation/histone) data identified.
  • Chromosomal abnormalities: Not a copy-number/structural disorder — point mutations and small indels/splice variants predominate; not associated with 21q22 microdeletion/duplication syndromes as a class (though 21q22.11 duplications encompassing DONSON have been studied for partial trisomy 21 phenotypes in an unrelated context; PMC5102301).

5. Environmental Information

Not applicable — this is a purely monogenic Mendelian disorder. No toxin, lifestyle, or infectious contributory factors have been identified in the literature reviewed.

6. Mechanism / Pathophysiology

Core molecular function of DONSON. DONSON is a replisome component essential for both (a) origin firing/replication initiation and (b) replication fork stability during elongation:

  • Replication initiation: DONSON is required for Cdc45 and GINS chromatin association with the MCM2-7 helicase and is essential for assembly of the active CMG (Cdc45-MCM-GINS) replicative helicase at replication origins (PMID:37638758; academic.oup.com/nar/51/18/9748). Recent structural work shows DONSON acts as a dimerization scaffold that synchronizes the delivery of two GINS complexes to the pre-replication complex, even though GINS itself cannot dimerize (PMC10996697; "structural mechanism of dimeric DONSON in replicative helicase activation," PMC7616792/ScienceDirect S109727652300761X). DONSON interacts with the initiation master-regulator TopBP1 in a CDK-dependent manner, and together with RecQL4 transiently docks the pre-replication complex before origin firing, without itself traveling with the elongating fork.
  • Fork stability: During S-phase, DONSON protein levels peak in parallel with Cyclin A and it associates with MCM helicase subunits, the GINS complex, PCNA, Treslin, and RPA to prevent spontaneous replication fork stalling during unperturbed DNA synthesis (PMID:28191891).

Consequence of DONSON hypomorphism: 1. Patient-derived and DONSON-depleted cells show elevated spontaneous replication fork asymmetry and stalling. 2. Stalled forks undergo pathological nucleolytic cleavage by the structure-specific endonucleases MUS81 and XPF, generating severe replication-associated DNA damage. 3. The ATR-dependent intra-S and G2/M checkpoints are impaired — reduced phosphorylation of CHK1 and NBS1 — so cells fail to properly arrest and repair in response to this damage ("Loss of DONSON leads to severe replication-associated DNA damage arising from nucleolytic cleavage of stalled replication forks," PMID:28191891). 4. Separately, DONSON depletion causes premature centriole disengagement during interphase, generating supernumerary centrosomes that drive abnormal mitotic spindle formation and chromosome segregation errors — a distinct centrosome-cycle mechanism proposed to compound the replication-stress phenotype (bioRxiv 2020.05.10.086777; later peer-reviewed).

Cell-type and tissue vulnerability — causal chain to microcephaly: Neural progenitor cells are exquisitely sensitive to replication stress because of their extremely high proliferative demand during cortical neurogenesis. Conditional mouse knockout studies (necessary because germline Donson loss is embryonic lethal) show that: - Cre-mediated Donson deletion in progenitors of both cortical glutamatergic (dorsal telencephalon/neocortex, hippocampus) and GABAergic (subpallial, Nkx2.1+ lineage) neurons causes extensive apoptosis in both the proliferative zones and postmitotic differentiation zones. - Nkx2.1-Cre-mediated deletion ablated ~75% of Nkx2.1-derived cortical GABAergic interneurons, and progenitors generating cortical interneurons and oligodendrocyte precursors were also affected (PLOS Genetics, PMC8011756/PMID via journals.plos.org/plosgenetics/10.1371/journal.pgen.1009441). - This establishes microcephaly in DONSON disease as a progenitor-depletion mechanism: replication-stress-induced apoptosis in rapidly dividing neuroepithelial and interneuron progenitor pools, rather than a primary neuronal degeneration process.

Suggested GO terms: GO:0006260 (DNA replication), GO:0031297 (replication fork processing), GO:0000076 (DNA replication checkpoint signaling), GO:0007099 (centriole replication), GO:0000086 (G2/M transition of mitotic cell cycle). Suggested CL terms: CL:0000047 (neural stem cell) / CL:0002605 (neural progenitor cell), CL:0000617 (GABAergic neuron), CL:0000679 (glutamatergic neuron).

7. Anatomical Structures Affected

  • Organ/system level: Central nervous system (brain — cerebral cortex, corpus callosum), skeletal system (limbs — radial ray, patella, digits; craniofacial skeleton — skull sutures, mandible, ears), growth/endocrine axis (generalized somatic growth failure). No primary cardiac, renal, or hepatic involvement is characteristic of the core phenotype (distinguishing it from some other MPDs).
  • Tissue/cell level: Neuroepithelial progenitors and cortical interneuron progenitors (proliferation and differentiation zones); chondro-osseous tissue of the growth plate and appendicular skeleton.
  • Subcellular level: DNA replication fork/replisome (nuclear, chromatin-associated), centrosome/centriole.
  • UBERON suggestions: UBERON:0000955 (brain), UBERON:0000956 (cerebral cortex), UBERON:0002331 (corpus callosum), UBERON:0002102 (forelimb/radius), UBERON:0002337 (patella).
  • Laterality: Generally bilateral/symmetric (microcephaly, growth restriction); limb involvement can be asymmetric in some case reports.

8. Temporal Development

  • Onset: Prenatal in the severe end of the spectrum (detectable IUGR, microcephaly, and limb anomalies on antenatal ultrasound in MIMIS); congenital/neonatal in milder MISSLA/MGS-like presentations.
  • Course: A static congenital malformation/growth syndrome rather than a progressive neurodegenerative disease — microcephaly and short stature are present from birth and persist, without a described post-natal regression phase.
  • Severity spectrum (disease "stages" in effect): MIMIS (prenatal/perinatal lethal) → Seckel-like/severe microcephaly with developmental delay → MGS-like (short stature, ear/patella anomalies) → FFS-like → MISSLA (mildest, survivable into childhood with mild ID). Authors have proposed these represent "a continuum of the same clinical spectrum of cell cycle-opathies, rather than discrete clinical entities" (PMC6936249).
  • Critical period: Embryonic/fetal neurogenesis and skeletal patterning windows, given the progenitor-depletion mechanism.

9. Inheritance and Population

  • Inheritance pattern: Autosomal recessive (biallelic hypomorphic variants); rare de novo/compound heterozygous cases reported.
  • Penetrance/expressivity: Full penetrance for biallelic hypomorphic genotypes but markedly variable expressivity (phenotype severity is genotype-dependent, per the exon 4 vs exons 5–10 correlation noted above).
  • Prevalence/incidence: Ultra-rare; exact population prevalence is not established. Total published cases across all DONSON-associated phenotypes number in the tens (the founding 2017 series described 29 individuals with biallelic DONSON mutations across multiple families; subsequent series added further families through 2019–2026).
  • Consanguinity: A notable proportion of reported families are consanguineous (homozygous variants identified via autozygosity mapping in several reports), consistent with a rare autosomal recessive disorder.
  • Founder effects: The recurrent p.(Arg211Cys) allele has now been reported in multiple, apparently unrelated families (including a Turkish family, PMID:41612845), raising the possibility of a mutational hotspot or a shared founder haplotype — not conclusively established from available sources.
  • Sex ratio / geographic distribution: No skewed sex ratio reported (consistent with autosomal inheritance); cases have been reported across diverse populations (European, Middle Eastern/Turkish, and others) without a described endemic geographic pattern.

10. Diagnostics

  • Primary diagnostic approach: Clinical suspicion based on the combination of severe (disproportionate) microcephaly, IUGR/short stature, and characteristic skeletal (radial ray, patellar) and craniofacial features, confirmed by molecular genetic testing.
  • Genetic testing:
  • Exome/genome sequencing is the primary diagnostic modality used in essentially all published cases; several diagnoses were made via research-based whole-exome or whole-genome sequencing, including one case solved only by combined genome + transcriptome (RNA) sequencing to detect a noncoding splice-disrupting variant not identifiable by exome alone (PMC5538549).
  • Targeted gene panels for microcephalic primordial dwarfism / Meier-Gorlin syndrome / Seckel syndrome typically now include DONSON alongside ORC1, ORC4, ORC6, CDT1, CDC6, GMNN, CDC45, MCM5, PCNT, ATR, RNU4ATAC, etc.
  • Single-gene sequencing of DONSON is reasonable when the clinical gestalt is highly suggestive (e.g., recurrent p.Arg211Cys hotspot).
  • Chromosomal microarray/karyotype are used to exclude alternative chromosomal causes of microcephalic dwarfism but are not diagnostic for DONSON disease itself.
  • Imaging: Prenatal ultrasound (severe IUGR, microcephaly, limb shortening) and postnatal brain MRI (simplified gyral pattern, reduced cortical volume, hypoplastic/absent corpus callosum in severe cases) and skeletal radiographs (patellar aplasia/hypoplasia, radial ray anomalies).
  • Differential diagnosis: Other microcephalic primordial dwarfisms — MOPD I (RNU4ATAC), MOPD II (PCNT), Seckel syndrome (ATR, CENPJ, CEP152, etc.), other Meier-Gorlin syndrome genes (ORC1/4/6, CDT1, CDC6, GMNN, CDC45, MCM5), 3-M syndrome, and Cornelia de Lange syndrome, need to be distinguished — genetically definitive but clinically overlapping.
  • Screening: No population/newborn screening program exists (ultra-rare Mendelian disorder); prenatal diagnosis via targeted variant testing is possible in families with a known DONSON variant, and preimplantation genetic diagnosis is theoretically applicable for known-carrier couples.

11. Outcome / Prognosis

  • Survival: Bimodal by phenotype severity — the MIMIS end of the spectrum is associated with intrauterine fetal death or perinatal lethality (severe growth restriction, microcephaly, and limb malformation incompatible with survival in the most severe reported fetuses). The MISSLA/MGS-like end of the spectrum is compatible with survival into childhood and beyond, albeit with lifelong short stature, microcephaly, and (in some) mild intellectual disability.
  • Morbidity: Persistent short stature, microcephaly, and skeletal (particularly upper-limb/radial ray) anomalies; mild intellectual disability and speech delay in a subset of survivors.
  • No disease-specific FDA-approved therapy exists — as with the great majority of ultra-rare Mendelian disorders (only ~5% of rare diseases overall have an FDA-approved treatment).
  • Prognostic factors: Variant location/type appears to be the major driver of severity (exon 4 missense variants → milder MGS/FFS phenotype; frameshift and exon 5–10 variants → more severe microcephaly/developmental impairment) (PMC6936249).

12. Treatment

No disease-modifying or curative therapy exists for DONSON-related disease; management is entirely supportive and multidisciplinary, analogous to management approaches used across the microcephalic primordial dwarfism spectrum (e.g., MOPD II):

  • Growth management: Auxological monitoring; growth hormone therapy is sometimes trialed empirically in primordial dwarfism syndromes generally, though no DONSON-specific efficacy data were identified in this search (suggested NCIT term: NCIT:C15986 Pharmacotherapy, generic, if used).
  • Neurodevelopmental support: Early intervention, physical/occupational/speech therapy (NCIT:C15302 Physical Therapy; NCIT:C159273 Speech Therapy; NCIT:C121351 Occupational Therapy) for developmental delay and mild intellectual disability.
  • Orthopedic management: Surgical correction of severe radial ray/thumb anomalies or patellar instability where functionally indicated (NCIT:C15329 Surgical Procedure; NCIT:C16186 Orthopedic Surgical Procedure).
  • Genetic counseling: Essential for affected families given autosomal recessive inheritance and 25% recurrence risk per pregnancy for carrier couples; prenatal diagnosis/PGD offered where a familial variant is known (NCIT:C15240 Genetic Counseling).
  • Multidisciplinary surveillance: As generalized for MPD/MOPD-spectrum disorders, follow-up should monitor for comorbidities described in related MPDs (e.g., MOPD II) such as cerebral vasculopathy, though DONSON-specific vasculopathy risk is not established in the literature reviewed — this should be treated as an extrapolation from the broader MPD category rather than a DONSON-specific finding.
  • Experimental/investigational therapy: None identified in ClinicalTrials.gov or the literature reviewed; no gene therapy, small-molecule, or targeted approach is in development specifically for DONSON disease as of this search.

13. Prevention

  • Primary prevention: Not applicable (Mendelian genetic disorder) beyond genetic counseling and reproductive options (carrier screening, prenatal diagnosis, PGD) in families with a known pathogenic variant.
  • Secondary prevention: Early molecular diagnosis enables anticipatory multidisciplinary surveillance (growth, neurodevelopment, orthopedic) but does not prevent disease onset.
  • Public health measures: None applicable — no environmental or infectious component.

14. Other Species / Natural Disease

No naturally occurring DONSON-related disease has been reported in non-human species in the literature surveyed here (no OMIA entries or veterinary case reports identified). DONSON orthologs exist across vertebrates (used experimentally in mouse and presumably zebrafish/other model systems — see below), but no spontaneous animal disease analog was found.

15. Model Organisms

  • Mouse (Mus musculus):
  • Constitutive/germline Donson knockout is embryonic lethal early in development — directly supporting the inference that all human disease alleles must be hypomorphic, since a complete null is not compatible with life (ResearchGate table, "Donson loss of function is lethal in early embryonic mouse development," referencing PMID:28191891 supplementary data).
  • Conditional (Cre-lox) knockout models were therefore developed to study tissue-specific roles. Donson is widely expressed in proliferative and differentiation zones of the embryonic dorsal and ventral telencephalon, with expression declining postnatally.
    • Emx1-Cre-mediated deletion in the dorsal telencephalic (cortical excitatory/glutamatergic) lineage and Nkx2.1-Cre-mediated deletion in the ventral (GABAergic interneuron) lineage both caused extensive apoptosis in proliferating progenitors and postmitotic differentiating cells, with Nkx2.1-Cre deletion ablating ~75% of Nkx2.1-derived cortical GABAergic interneurons and also affecting oligodendrocyte precursor generation (PLOS Genetics 2021, PMC8011756).
  • This conditional-knockout model recapitulates the human microcephaly phenotype at the cellular/progenitor level (progenitor loss via apoptosis) though it does not model the skeletal/limb component of the human disease.
  • Patient-derived cell lines: Primary fibroblasts and lymphoblastoid lines from affected individuals are the principal human cellular model, showing increased spontaneous replication fork stalling/asymmetry, impaired ATR checkpoint signaling (reduced CHK1/NBS1 phosphorylation), and elevated S-phase DNA damage — used extensively for functional variant characterization (complementation/rescue assays) (PMID:28191891; academic.oup.com/nar/51/18/9748).
  • In vitro/biochemical systems: Cell-free Xenopus egg extract and reconstituted human replication systems have been used to define DONSON's biochemical role in CMG helicase assembly and its dimeric GINS-scaffolding function (single-molecule imaging studies, PMC10996697; PMC7616792).
  • Invertebrate models (Drosophila, zebrafish, C. elegans): No DONSON-specific knockout/mutant phenotype data were identified in this search; general zebrafish microcephaly-modeling methodology exists for other MCPH genes but no DONSON-specific zebrafish study was found.
  • Model limitations: The mouse conditional-knockout system captures the neural progenitor-depletion/microcephaly mechanism well but does not reproduce the skeletal (limb, patellar) phenotype seen in humans, and — because human disease alleles are hypomorphic rather than null — a true knockout may over-represent the severity of pathway disruption relative to the partial-function state present in patients.

Sources

Reference Validation

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Outcome Count
References checked 15
Resolved 15
Unresolved (possible confabulation) 0
Unverifiable 0
Quoted claims checked 1
Quoted claims found in source 0
Quoted claims not found in source 1
References weighed for topical relevance 15
On topic 12
Off topic 0

Quotes not found in the cited source

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  • PMC:PMC6936249 (abstract only): "a continuum of the same clinical spectrum of cell cycle-opathies, rather than discrete clinical entities"
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