TUBGCP4-related Microcephaly and Chorioretinopathy

👪

Inheritance

1

Autosomal recessive inheritance HP:0000007

The disorder is autosomal recessive. The founding families and later case reports identified two TUBGCP4 variants in affected individuals, including compound-heterozygous or confirmed in-trans variants.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:25817018 SUPPORT Human Clinical

"Whole-exome sequencing performed on one family with two affected siblings and independently on another family with one affected child revealed compound-heterozygous mutations in TUBGCP4."

Establishes biallelic compound-heterozygous inheritance across two independent families.

PMID:37038737 SUPPORT Human Clinical

"Molecular diagnosis using exome sequencing demonstrated two TUBCGP4 variants in trans: c.1669C>T (p.Arg557*) and c.1746 G>T (p.Leu582=)."

Confirms two in-trans variants in a later case; the snippet preserves the source abstract's TUBCGP4 typographical error.

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Pathophysiology

4

Reduced Gamma-Tubulin Ring Complex Level

Mechanism confidence: Established

TUBGCP4 is a gamma-TuRC component. In fibroblasts from affected individuals, the founding study directly measured reduced gamma-TuRC levels. Reported alleles included frameshift variants, a deletion, and a recurrent synonymous allele shown to induce exon skipping; later cases also included nonsense alleles.

TUBGCP4 hgnc:16691

Genetic context allele_type: frameshift, nonsense, deletion, splice-altering synonymous variant_origin: GERMLINE zygosity: COMPOUND_HETEROZYGOUS functional_impact_category: LOSS_OF_FUNCTION

Reported biallelic alleles include truncating variants, a deletion, and a recurrent synonymous allele for which exon skipping was demonstrated. The patient-fibroblast experiment measured reduced gamma-TuRC levels, but the relative contribution of each allele class was not resolved in the cached abstract.

gamma-tubulin ring complex GO:0000930

Downstream

Altered Microtubule Nucleation and Organization in Patient Fibroblasts Gamma-TuRC regulates microtubule nucleation and organization, and both reduced complex levels and altered microtubule behavior were observed in the same patient-fibroblast analysis.

Show evidence (4 references)

PMID:25817018 SUPPORT In Vitro

"Functional analysis of individual fibroblasts disclosed reduced levels of the γ-TuRC, altered nucleation and organization of microtubules, abnormal nuclear shape, and aneuploidy."

Directly reports reduced gamma-TuRC levels in fibroblasts from affected individuals; the other observations are represented in separate nodes.

PMID:25817018 SUPPORT Human Clinical

"TUBGCP4 encodes γ-tubulin complex protein 4, a component belonging to the γ-tubulin ring complex (γ-TuRC) and known to regulate the nucleation and organization of microtubules."

Identifies the gene product's role in the nucleating complex.

PMID:25817018 SUPPORT Human Clinical

"One synonymous variant was common to all three families and was shown to induce exon skipping; the other mutations were frameshift mutations and a deletion."

The allele classes underpinning the LOSS_OF_FUNCTION assignment, including a synonymous variant acting through splicing.

+ 1 more reference

Altered Microtubule Nucleation and Organization in Patient Fibroblasts

Mechanism confidence: Established

Fibroblasts from affected individuals showed altered microtubule nucleation and organization. This is a patient-cell observation; the abstract does not establish the behavior of neural or retinal progenitors.

microtubule nucleation GO:0007020 ↕ DYSREGULATED microtubule cytoskeleton organization GO:0000226 ↕ DYSREGULATED

Downstream

Abnormal Nuclear Shape and Aneuploidy in Patient Fibroblasts Abnormal nuclear shape and aneuploidy accompanied the altered microtubule readouts, but the abstract does not test this edge as a causal sequence.

Show evidence (1 reference)

PMID:25817018 SUPPORT In Vitro

"Functional analysis of individual fibroblasts disclosed reduced levels of the γ-TuRC, altered nucleation and organization of microtubules, abnormal nuclear shape, and aneuploidy."

Directly reports the altered nucleation and organization readouts in patient fibroblasts.

Abnormal Nuclear Shape and Aneuploidy in Patient Fibroblasts

Mechanism confidence: Established

Patient fibroblasts showed abnormal nuclear shape and aneuploidy. These findings are direct cellular observations, but the study abstract does not demonstrate impaired progenitor output in human brain or retina.

Downstream

Hypothesized Impairment of Brain and Eye Development A developmental-progenitor mechanism is plausible but has not been shown in relevant human tissues.

Show evidence (1 reference)

PMID:25817018 SUPPORT In Vitro

"Functional analysis of individual fibroblasts disclosed reduced levels of the γ-TuRC, altered nucleation and organization of microtubules, abnormal nuclear shape, and aneuploidy."

Directly reports both cellular readouts in patient fibroblasts.

Hypothesized Impairment of Brain and Eye Development

Mechanism confidence: Hypothetical

TUBGCP4 morpholino-treated zebrafish had reduced head volume and eye developmental anomalies with chorioretinal dysplasia, while humans with biallelic variants have microcephaly and eye-development abnormalities. The cross-species concordance supports a developmental hypothesis, not a demonstrated human tissue-level causal chain; a later case report states that the syndrome's pathophysiology is not fully understood.

Animal models

tubgcp4 morpholino knockdown zebrafish Zebrafish (Danio rerio) partially recapitulates The model reproduces reduced head volume and eye-development abnormalities that motivate this tissue-level hypothesis, without establishing the proposed developmental route in humans.

Downstream

Microcephaly The human phenotype is established, but the developmental intermediates from the cellular observations are unresolved.

Chorioretinopathy The human phenotype is established, but the retinal cellular mechanism is unresolved.

Show evidence (3 references)

PMID:25817018 SUPPORT Model Organism

"Moreover, zebrafish treated with morpholinos against tubgcp4 were found to have reduced head volume and eye developmental anomalies with chorioretinal dysplasia."

Establishes the zebrafish morphant observations, while the model and its connection to human tissue mechanisms remain indirect.

PMID:25817018 SUPPORT Human Clinical

"the identification of TUBGCP4 mutations in individuals with microcephaly and a spectrum of anomalies in eye development, particularly photoreceptor anomalies, provides evidence of an important role for the γ-TuRC in brain and eye development"

Establishes the human genotype-phenotype association but does not identify the intervening tissue mechanism.

PMID:37038737 SUPPORT Human Clinical

"The pathophysiology of this syndrome is not yet fully understood."

Supports retaining the tissue-level bridge as hypothetical; this statement is a limitation, not positive evidence for a particular causal route.

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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

7

Eye 4

Chorioretinopathy Abnormal chorioretinal morphology HP:0000532

Show evidence (2 references)

PMID:25817018 SUPPORT Human Clinical

"We have identified TUBGCP4 variants in individuals with autosomal-recessive microcephaly and chorioretinopathy."

Establishes chorioretinopathy as a defining human phenotype.

PMID:32270730 SUPPORT Human Clinical

"The clinical phenotype was characterized by microcephaly, microphthalmia, chorioretinopathy, a punched-out retinal appearance, dysmorphic facial features, decreased visual acuity, and learning difficulties."

Directly reports chorioretinopathy with a punched-out retinal appearance in a later molecularly diagnosed proband.

Reduced Visual Acuity HP:0007663

Show evidence (2 references)

PMID:32270730 SUPPORT Human Clinical

"The clinical phenotype was characterized by microcephaly, microphthalmia, chorioretinopathy, a punched-out retinal appearance, dysmorphic facial features, decreased visual acuity, and learning difficulties."

Directly reports decreased visual acuity in one molecularly diagnosed proband.

PMID:37038737 SUPPORT Human Clinical

"Clinical characteristics included microcephaly, microphthalmia, punched-out chorioretinal lesions, vision impairment, nystagmus, Tetralogy of Fallot and neurodevelopmental delay."

Directly reports vision impairment in a second individual case report.

Microphthalmia HP:0000568

Show evidence (2 references)

PMID:32270730 SUPPORT Human Clinical

"The clinical phenotype was characterized by microcephaly, microphthalmia, chorioretinopathy, a punched-out retinal appearance, dysmorphic facial features, decreased visual acuity, and learning difficulties."

Directly reports microphthalmia in one proband.

PMID:37038737 SUPPORT Human Clinical

"Clinical characteristics included microcephaly, microphthalmia, punched-out chorioretinal lesions, vision impairment, nystagmus, Tetralogy of Fallot and neurodevelopmental delay."

Directly reports microphthalmia in a second proband.

Nystagmus HP:0000639

Show evidence (1 reference)

PMID:37038737 SUPPORT Human Clinical

"Clinical characteristics included microcephaly, microphthalmia, punched-out chorioretinal lesions, vision impairment, nystagmus, Tetralogy of Fallot and neurodevelopmental delay."

Directly reports nystagmus in a single proband.

Head and Neck 2

Microcephaly HP:0000252

Show evidence (1 reference)

PMID:25817018 SUPPORT Human Clinical

"We have identified TUBGCP4 variants in individuals with autosomal-recessive microcephaly and chorioretinopathy."

Establishes microcephaly as a defining feature.

Abnormal Facial Shape HP:0001999

Show evidence (1 reference)

PMID:32270730 SUPPORT Human Clinical

"The clinical phenotype was characterized by microcephaly, microphthalmia, chorioretinopathy, a punched-out retinal appearance, dysmorphic facial features, decreased visual acuity, and learning difficulties."

Directly reports dysmorphic facial features in one proband; the broader HPO term avoids inventing a specific facial gestalt.

Nervous System 1

Neurodevelopmental Delay HP:0012758

Show evidence (1 reference)

PMID:37038737 SUPPORT Human Clinical

"Clinical characteristics included microcephaly, microphthalmia, punched-out chorioretinal lesions, vision impairment, nystagmus, Tetralogy of Fallot and neurodevelopmental delay."

Directly reports neurodevelopmental delay in a single proband; no frequency is inferred.

🧬

Genetic Associations

1

TUBGCP4 (Causative)

Gene: TUBGCP4 (gamma-tubulin complex protein 4) hgnc:16691

Show evidence (2 references)

PMID:25817018 SUPPORT Human Clinical

"We have identified TUBGCP4 variants in individuals with autosomal-recessive microcephaly and chorioretinopathy."

Founding evidence for TUBGCP4 as the causative gene.

PMID:37038737 SUPPORT Human Clinical

"Molecular diagnosis using exome sequencing demonstrated two TUBCGP4 variants in trans: c.1669C>T (p.Arg557*) and c.1746 G>T (p.Leu582=)."

A later case independently identified two TUBGCP4 variants in trans; the snippet preserves the source abstract's TUBCGP4 typographical error.

💊

Medical Actions

1

Mixed-cohort ophthalmic-genetics surveillance

Action: supportive care Ontology label: Supportive Care NCIT:C15747

Close monitoring by a team experienced in ophthalmic genetics was recommended for a mixed KIF11/TUBGCP4/TUBGCP6 cohort. This is a pooled-cohort surveillance recommendation, not evidence of TUBGCP4-specific treatment efficacy or a TUBGCP4-specific progression rate.

Show evidence (1 reference)

PMID:33137195 SUPPORT Human Clinical

"Microcephaly due to mutations in KIF11, TUBGCP4, or TUBGCP6 can be associated with retinal disease on a spectrum from chorioretinal atrophy to FEVR-like posterior segment changes. Visually significant disease progression can occur and patients should be monitored closely by a team experienced in..."

Directly supports close ophthalmic-genetics monitoring in the mixed-gene cohort. Only one participant had TUBGCP4 variants, so this does not establish TUBGCP4-specific efficacy or progression.

🔬

Diagnosis

2

Ophthalmic phenotyping

Published phenotyping has used ophthalmologic examination and imaging, electroretinography, and visual-field assessment to characterize retinal structure and function. The supporting natural-history cohort combined KIF11, TUBGCP4, and TUBGCP6 cases, so it does not establish the yield of each modality specifically for TUBGCP4.

eye examination NCIT:C38060

Show evidence (1 reference)

PMID:33137195 SUPPORT Human Clinical

"Data from medical records, ophthalmologic examination and imaging, electroretinography, and visual fields were analyzed for systemic and ophthalmic features and evidence of posterior segment disease progression."

Documents the assessment modalities used in a mixed-gene cohort that included one participant with TUBGCP4 variants; it is not a TUBGCP4-specific diagnostic-accuracy study.

Molecular genetic testing

Founding families were diagnosed through exome sequencing; a later case report separately performed segregation analysis after molecular diagnosis. The recurrent synonymous allele reported across the founding families was shown to induce exon skipping, establishing a splice effect for that allele despite its synonymous coding annotation.

genetic testing NCIT:C15709

Show evidence (3 references)

PMID:25817018 SUPPORT Human Clinical

"Whole-exome sequencing performed on one family with two affected siblings and independently on another family with one affected child revealed compound-heterozygous mutations in TUBGCP4."

Documents exome-based identification of biallelic variants in independent families.

PMID:25817018 SUPPORT Human Clinical

"One synonymous variant was common to all three families and was shown to induce exon skipping"

Directly establishes the splice effect of the recurrent synonymous allele.

PMID:32270730 SUPPORT Human Clinical

"This is a case report of a patient with a molecular diagnosis defined by mutations in the TUBGCP4 gene. Segregation analyses were carried out."

Documents a later molecular diagnosis with segregation analysis.

📈

Progression

1

Long-term ophthalmic course

One TUBGCP4 proband was reported as clinically stable over two decades. A separate mixed KIF11/TUBGCP4/TUBGCP6 cohort, which included only one person with TUBGCP4 variants, found that visually significant posterior-segment progression can occur and recommended close ophthalmic-genetics monitoring. Progression is reported only for the pooled cohort, so the direction and rate of TUBGCP4-specific retinal change remain uncertain.

Show evidence (3 references)

PMID:37038737 SUPPORT Human Clinical

"Clinical characteristics in our proband have remained stable for two decades."

This is a single-proband observation over long follow-up and is not a population natural-history estimate.

PMID:33137195 SUPPORT Human Clinical

"Nine patients had KIF11 variants, two had heterozygous TUBGCP6 variants, and one had heterozygous variants in TUBGCP4."

Establishes that the natural-history source is a mixed-gene cohort with only one TUBGCP4 participant; it does not isolate that participant's course.

PMID:33137195 SUPPORT Human Clinical

"Microcephaly due to mutations in KIF11, TUBGCP4, or TUBGCP6 can be associated with retinal disease on a spectrum from chorioretinal atrophy to FEVR-like posterior segment changes. Visually significant disease progression can occur and patients should be monitored closely by a team experienced in..."

This conclusion comes from a mixed-gene cohort. Only one of the 12 participants had TUBGCP4 variants, and the reported course is pooled; the result supports surveillance context but not a TUBGCP4-specific progression rate.

🐁

Animal Models

1

tubgcp4 morpholino knockdown zebrafish Morpholino knockdown

Morpholino-treated zebrafish had reduced head volume and eye developmental anomalies with chorioretinal dysplasia. This is a transient knockdown model, not a stable patient-variant model, and it does not establish the intervening human developmental mechanism.

Species

Zebrafish (Danio rerio)

Genotype

tubgcp4 morpholino knockdown

Genes

TUBGCP4 hgnc:16691

Pathograph links

Hypothesized Impairment of Brain and Eye Development partially recapitulates fidelity: low The model reproduces reduced head volume and eye-development abnormalities that motivate this tissue-level hypothesis, without establishing the proposed developmental route in humans.

Limitations: This is transient morpholino knockdown in zebrafish rather than a stable patient-variant model. The nonhuman organ-level concordance does not identify neural or retinal intermediates or establish causality for the human phenotypes.

Show evidence (1 reference)

PMID:25817018 SUPPORT Model Organism

"Moreover, zebrafish treated with morpholinos against tubgcp4 were found to have reduced head volume and eye developmental anomalies with chorioretinal dysplasia."

Supports the model as partially informative for the developmental hypothesis while the translational limitations remain explicit.

Show evidence (1 reference)

PMID:25817018 SUPPORT Model Organism

"Moreover, zebrafish treated with morpholinos against tubgcp4 were found to have reduced head volume and eye developmental anomalies with chorioretinal dysplasia."

Directly reports the morpholino model and its observed brain and eye phenotypes; the limitations are recorded in the model description.

{ }

Source YAML

click to show

name: TUBGCP4-related Microcephaly and Chorioretinopathy
creation_date: "2026-08-20T17:30:00Z"
category: Mendelian
disease_term:
  preferred_term: microcephaly and chorioretinopathy 3
  term:
    id: MONDO:0014592
    label: microcephaly and chorioretinopathy 3
description: >-
  TUBGCP4-related microcephaly and chorioretinopathy (MCCRP3) is an
  autosomal recessive neuro-ophthalmic disorder caused by biallelic TUBGCP4
  variants. TUBGCP4 encodes a component of the gamma-tubulin ring complex
  (gamma-TuRC), which regulates microtubule nucleation and organization.

  In the founding study, patient fibroblasts had reduced gamma-TuRC levels,
  altered microtubule nucleation and organization, abnormal nuclear shape, and
  aneuploidy. TUBGCP4 morpholino-treated zebrafish had reduced head volume and
  eye-development abnormalities with chorioretinal dysplasia. These are direct
  experimental observations, but the intervening mechanism that connects them
  to human brain and retinal development has not been established.

  Reported human findings include microcephaly, chorioretinopathy or punched-out
  chorioretinal lesions, microphthalmia, reduced vision, and developmental or
  learning difficulties. Nystagmus and dysmorphic facial features have each
  been described in individual case reports. The small published case base does
  not support population frequency estimates for these findings.
parents:
- hereditary disease
- congenital nervous system disorder
- eye disease
references:
- reference: PMID:25817018
  title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
- reference: PMID:32270730
  title: TUBGCP4 - associated microcephaly and chorioretinopathy.
- reference: PMID:37038737
  title: "Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature."
- reference: PMID:33137195
  title: Genotype Phenotype Correlation and Variability in Microcephaly Associated With Chorioretinopathy or Familial Exudative Vitreoretinopathy.
progression:
- phase: Long-term ophthalmic course
  notes: >-
    One TUBGCP4 proband was reported as clinically stable over two decades. A
    separate mixed KIF11/TUBGCP4/TUBGCP6 cohort, which included only one person
    with TUBGCP4 variants, found that visually significant posterior-segment
    progression can occur and recommended close ophthalmic-genetics monitoring.
    Progression is reported only for the pooled cohort, so the direction and
    rate of TUBGCP4-specific retinal change remain uncertain.
  evidence:
  - reference: PMID:37038737
    reference_title: "Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinical characteristics in our proband have remained stable for two
      decades.
    explanation: >-
      This is a single-proband observation over long follow-up and is not a
      population natural-history estimate.
  - reference: PMID:33137195
    reference_title: Genotype Phenotype Correlation and Variability in Microcephaly Associated With Chorioretinopathy or Familial Exudative Vitreoretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Nine patients had KIF11 variants, two had heterozygous TUBGCP6 variants,
      and one had heterozygous variants in TUBGCP4.
    explanation: >-
      Establishes that the natural-history source is a mixed-gene cohort with
      only one TUBGCP4 participant; it does not isolate that participant's
      course.
  - reference: PMID:33137195
    reference_title: Genotype Phenotype Correlation and Variability in Microcephaly Associated With Chorioretinopathy or Familial Exudative Vitreoretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Microcephaly due to mutations in KIF11, TUBGCP4, or TUBGCP6 can be
      associated with retinal disease on a spectrum from chorioretinal atrophy
      to FEVR-like posterior segment changes. Visually significant disease
      progression can occur and patients should be monitored closely by a team
      experienced in ophthalmic genetics.
    explanation: >-
      This conclusion comes from a mixed-gene cohort. Only one of the 12
      participants had TUBGCP4 variants, and the reported course is pooled; the
      result supports surveillance context but not a TUBGCP4-specific
      progression rate.
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    The disorder is autosomal recessive. The founding families and later case
    reports identified two TUBGCP4 variants in affected individuals, including
    compound-heterozygous or confirmed in-trans variants.
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Whole-exome sequencing performed on one family with two affected siblings
      and independently on another family with one affected child revealed
      compound-heterozygous mutations in TUBGCP4.
    explanation: >-
      Establishes biallelic compound-heterozygous inheritance across two
      independent families.
  - reference: PMID:37038737
    reference_title: "Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Molecular diagnosis using exome sequencing demonstrated two TUBCGP4
      variants in trans: c.1669C>T (p.Arg557*) and c.1746 G>T (p.Leu582=).
    explanation: >-
      Confirms two in-trans variants in a later case; the snippet preserves the
      source abstract's TUBCGP4 typographical error.
pathophysiology:
- name: Reduced Gamma-Tubulin Ring Complex Level
  role: TRIGGER
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    TUBGCP4 is a gamma-TuRC component. In fibroblasts from affected individuals,
    the founding study directly measured reduced gamma-TuRC levels. Reported
    alleles included frameshift variants, a deletion, and a recurrent synonymous
    allele shown to induce exon skipping; later cases also included nonsense
    alleles.
  genetic_context:
    functional_impact_category: LOSS_OF_FUNCTION
    variant_origin: GERMLINE
    zygosity: COMPOUND_HETEROZYGOUS
    allele_type: frameshift, nonsense, deletion, splice-altering synonymous
    description: >-
      Reported biallelic alleles include truncating variants, a deletion, and a
      recurrent synonymous allele for which exon skipping was demonstrated. The
      patient-fibroblast experiment measured reduced gamma-TuRC levels, but the
      relative contribution of each allele class was not resolved in the cached
      abstract.
  genes:
  - preferred_term: TUBGCP4
    term:
      id: hgnc:16691
      label: TUBGCP4
  cellular_components:
  - preferred_term: gamma-tubulin ring complex
    term:
      id: GO:0000930
      label: gamma-tubulin complex
    modifier: DECREASED
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Functional analysis of individual fibroblasts disclosed reduced levels of
      the γ-TuRC, altered nucleation and organization of microtubules, abnormal
      nuclear shape, and aneuploidy.
    explanation: >-
      Directly reports reduced gamma-TuRC levels in fibroblasts from affected
      individuals; the other observations are represented in separate nodes.
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      TUBGCP4 encodes γ-tubulin complex protein 4, a component belonging to the
      γ-tubulin ring complex (γ-TuRC) and known to regulate the nucleation and
      organization of microtubules.
    explanation: >-
      Identifies the gene product's role in the nucleating complex.
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      One synonymous variant was common to all three families and was shown to
      induce exon skipping; the other mutations were frameshift mutations and a
      deletion.
    explanation: >-
      The allele classes underpinning the LOSS_OF_FUNCTION assignment, including
      a synonymous variant acting through splicing.
  - reference: PMID:32270730
    reference_title: TUBGCP4 - associated microcephaly and chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The molecular investigation found two heterozygous variants c.1380 G > A
      (p.Trp460*) a novel nonsense variant, and c.1746 G > T (p Leu582=) a
      synonymous variant in TUBGCP4.
    explanation: >-
      A later case directly reports a nonsense allele paired with a synonymous
      allele, supporting the expanded reported allele spectrum.
  downstream:
  - target: Altered Microtubule Nucleation and Organization in Patient Fibroblasts
    causal_link_type: DIRECT
    description: >-
      Gamma-TuRC regulates microtubule nucleation and organization, and both
      reduced complex levels and altered microtubule behavior were observed in
      the same patient-fibroblast analysis.
    evidence:
    - reference: PMID:25817018
      reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Functional analysis of individual fibroblasts disclosed reduced levels
        of the γ-TuRC, altered nucleation and organization of microtubules,
        abnormal nuclear shape, and aneuploidy.
      explanation: >-
        The same patient-cell analysis measured reduced complex levels and
        altered microtubule nucleation and organization.
- name: Altered Microtubule Nucleation and Organization in Patient Fibroblasts
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Fibroblasts from affected individuals showed altered microtubule nucleation
    and organization. This is a patient-cell observation; the abstract does not
    establish the behavior of neural or retinal progenitors.
  biological_processes:
  - preferred_term: microtubule nucleation
    term:
      id: GO:0007020
      label: microtubule nucleation
    modifier: DYSREGULATED
  - preferred_term: microtubule cytoskeleton organization
    term:
      id: GO:0000226
      label: microtubule cytoskeleton organization
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Functional analysis of individual fibroblasts disclosed reduced levels of
      the γ-TuRC, altered nucleation and organization of microtubules, abnormal
      nuclear shape, and aneuploidy.
    explanation: >-
      Directly reports the altered nucleation and organization readouts in
      patient fibroblasts.
  downstream:
  - target: Abnormal Nuclear Shape and Aneuploidy in Patient Fibroblasts
    causal_link_type: UNKNOWN
    description: >-
      Abnormal nuclear shape and aneuploidy accompanied the altered microtubule
      readouts, but the abstract does not test this edge as a causal sequence.
- name: Abnormal Nuclear Shape and Aneuploidy in Patient Fibroblasts
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Patient fibroblasts showed abnormal nuclear shape and aneuploidy. These
    findings are direct cellular observations, but the study abstract does not
    demonstrate impaired progenitor output in human brain or retina.
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Functional analysis of individual fibroblasts disclosed reduced levels of
      the γ-TuRC, altered nucleation and organization of microtubules, abnormal
      nuclear shape, and aneuploidy.
    explanation: >-
      Directly reports both cellular readouts in patient fibroblasts.
  downstream:
  - target: Hypothesized Impairment of Brain and Eye Development
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Effects in neural and retinal progenitors have not been measured
    - The route from fibroblast aneuploidy to organ-level growth is unresolved
    description: >-
      A developmental-progenitor mechanism is plausible but has not been shown
      in relevant human tissues.
- name: Hypothesized Impairment of Brain and Eye Development
  biological_scale: TISSUE
  mechanism_confidence: HYPOTHETICAL
  description: >-
    TUBGCP4 morpholino-treated zebrafish had reduced head volume and eye
    developmental anomalies with chorioretinal dysplasia, while humans with
    biallelic variants have microcephaly and eye-development abnormalities. The
    cross-species concordance supports a developmental hypothesis, not a
    demonstrated human tissue-level causal chain; a later case report states
    that the syndrome's pathophysiology is not fully understood.
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Moreover, zebrafish treated with morpholinos against tubgcp4 were found to
      have reduced head volume and eye developmental anomalies with chorioretinal
      dysplasia.
    explanation: >-
      Establishes the zebrafish morphant observations, while the model and its
      connection to human tissue mechanisms remain indirect.
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the identification of TUBGCP4 mutations in individuals with microcephaly
      and a spectrum of anomalies in eye development, particularly photoreceptor
      anomalies, provides evidence of an important role for the γ-TuRC in brain
      and eye development
    explanation: >-
      Establishes the human genotype-phenotype association but does not identify
      the intervening tissue mechanism.
  - reference: PMID:37038737
    reference_title: "Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The pathophysiology of this syndrome is not yet fully understood.
    explanation: >-
      Supports retaining the tissue-level bridge as hypothetical; this statement
      is a limitation, not positive evidence for a particular causal route.
  downstream:
  - target: Microcephaly
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The human phenotype is established, but the developmental intermediates
      from the cellular observations are unresolved.
  - target: Chorioretinopathy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The human phenotype is established, but the retinal cellular mechanism is
      unresolved.
phenotypes:
- name: Microcephaly
  description: >-
    Microcephaly is a core reported feature in the founding series and later
    case reports. No population-level frequency is assigned from the small,
    phenotype-ascertained literature.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We have identified TUBGCP4 variants in individuals with autosomal-recessive
      microcephaly and chorioretinopathy.
    explanation: Establishes microcephaly as a defining feature.
- name: Chorioretinopathy
  description: >-
    Chorioretinopathy is a core ocular feature. Published descriptions include
    punched-out chorioretinal lesions and broader eye-development anomalies,
    particularly photoreceptor anomalies.
  phenotype_term:
    preferred_term: Chorioretinopathy
    term:
      id: HP:0000532
      label: Abnormal chorioretinal morphology
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We have identified TUBGCP4 variants in individuals with autosomal-recessive
      microcephaly and chorioretinopathy.
    explanation: >-
      Establishes chorioretinopathy as a defining human phenotype.
  - reference: PMID:32270730
    reference_title: TUBGCP4 - associated microcephaly and chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The clinical phenotype was characterized by microcephaly, microphthalmia,
      chorioretinopathy, a punched-out retinal appearance, dysmorphic facial
      features, decreased visual acuity, and learning difficulties.
    explanation: >-
      Directly reports chorioretinopathy with a punched-out retinal appearance
      in a later molecularly diagnosed proband.
- name: Reduced Visual Acuity
  description: >-
    Reduced visual acuity or vision impairment was reported directly in later
    TUBGCP4 case reports.
  phenotype_term:
    preferred_term: Reduced visual acuity
    term:
      id: HP:0007663
      label: Reduced visual acuity
  evidence:
  - reference: PMID:32270730
    reference_title: TUBGCP4 - associated microcephaly and chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The clinical phenotype was characterized by microcephaly, microphthalmia,
      chorioretinopathy, a punched-out retinal appearance, dysmorphic facial
      features, decreased visual acuity, and learning difficulties.
    explanation: >-
      Directly reports decreased visual acuity in one molecularly diagnosed
      proband.
  - reference: PMID:37038737
    reference_title: "Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinical characteristics included microcephaly, microphthalmia,
      punched-out chorioretinal lesions, vision impairment, nystagmus, Tetralogy
      of Fallot and neurodevelopmental delay.
    explanation: >-
      Directly reports vision impairment in a second individual case report.
- name: Microphthalmia
  description: >-
    Microphthalmia was described in the individual probands of two later case
    reports. These observations do not establish a population frequency.
  phenotype_term:
    preferred_term: Microphthalmia
    term:
      id: HP:0000568
      label: Microphthalmia
  evidence:
  - reference: PMID:32270730
    reference_title: TUBGCP4 - associated microcephaly and chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The clinical phenotype was characterized by microcephaly, microphthalmia,
      chorioretinopathy, a punched-out retinal appearance, dysmorphic facial
      features, decreased visual acuity, and learning difficulties.
    explanation: Directly reports microphthalmia in one proband.
  - reference: PMID:37038737
    reference_title: "Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinical characteristics included microcephaly, microphthalmia,
      punched-out chorioretinal lesions, vision impairment, nystagmus, Tetralogy
      of Fallot and neurodevelopmental delay.
    explanation: Directly reports microphthalmia in a second proband.
- name: Neurodevelopmental Delay
  description: >-
    Neurodevelopmental delay was reported in one long-followed proband. This is
    a case-level description rather than a severity or frequency estimate.
  phenotype_term:
    preferred_term: Neurodevelopmental delay
    term:
      id: HP:0012758
      label: Neurodevelopmental delay
  evidence:
  - reference: PMID:37038737
    reference_title: "Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinical characteristics included microcephaly, microphthalmia,
      punched-out chorioretinal lesions, vision impairment, nystagmus, Tetralogy
      of Fallot and neurodevelopmental delay.
    explanation: >-
      Directly reports neurodevelopmental delay in a single proband; no frequency
      is inferred.
- name: Nystagmus
  description: >-
    Nystagmus was reported in one long-followed proband, so it is represented as
    a case-level feature without a frequency assignment.
  phenotype_term:
    preferred_term: Nystagmus
    term:
      id: HP:0000639
      label: Nystagmus
  evidence:
  - reference: PMID:37038737
    reference_title: "Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinical characteristics included microcephaly, microphthalmia,
      punched-out chorioretinal lesions, vision impairment, nystagmus, Tetralogy
      of Fallot and neurodevelopmental delay.
    explanation: Directly reports nystagmus in a single proband.
- name: Abnormal Facial Shape
  description: >-
    Dysmorphic facial features were reported in one case. The abstract does not
    define a recurrent facial pattern or support a frequency estimate.
  phenotype_term:
    preferred_term: Abnormal facial shape
    term:
      id: HP:0001999
      label: Abnormal facial shape
  evidence:
  - reference: PMID:32270730
    reference_title: TUBGCP4 - associated microcephaly and chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The clinical phenotype was characterized by microcephaly, microphthalmia,
      chorioretinopathy, a punched-out retinal appearance, dysmorphic facial
      features, decreased visual acuity, and learning difficulties.
    explanation: >-
      Directly reports dysmorphic facial features in one proband; the broader HPO
      term avoids inventing a specific facial gestalt.
genetic:
- name: TUBGCP4
  association: Causative
  gene_term:
    preferred_term: TUBGCP4 (gamma-tubulin complex protein 4)
    term:
      id: hgnc:16691
      label: TUBGCP4
  notes: >-
    A gamma-tubulin complex component rather than a tubulin isotype. This is the
    boundary the Tubulinopathies grouping draws: TUBG1 encodes gamma-tubulin
    itself and is a grouping member, whereas TUBGCP4 encodes an associated
    complex protein and is not.
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We have identified TUBGCP4 variants in individuals with autosomal-recessive
      microcephaly and chorioretinopathy.
    explanation: Founding evidence for TUBGCP4 as the causative gene.
  - reference: PMID:37038737
    reference_title: "Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Molecular diagnosis using exome sequencing demonstrated two TUBCGP4
      variants in trans: c.1669C>T (p.Arg557*) and c.1746 G>T (p.Leu582=).
    explanation: >-
      A later case independently identified two TUBGCP4 variants in trans; the
      snippet preserves the source abstract's TUBCGP4 typographical error.
diagnosis:
- name: Ophthalmic phenotyping
  description: >-
    Published phenotyping has used ophthalmologic examination and imaging,
    electroretinography, and visual-field assessment to characterize retinal
    structure and function. The supporting natural-history cohort combined
    KIF11, TUBGCP4, and TUBGCP6 cases, so it does not establish the yield of each
    modality specifically for TUBGCP4.
  diagnosis_term:
    preferred_term: eye examination
    term:
      id: NCIT:C38060
      label: Eye Examination
  evidence:
  - reference: PMID:33137195
    reference_title: Genotype Phenotype Correlation and Variability in Microcephaly Associated With Chorioretinopathy or Familial Exudative Vitreoretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Data from medical records, ophthalmologic examination and imaging,
      electroretinography, and visual fields were analyzed for systemic and
      ophthalmic features and evidence of posterior segment disease progression.
    explanation: >-
      Documents the assessment modalities used in a mixed-gene cohort that
      included one participant with TUBGCP4 variants; it is not a
      TUBGCP4-specific diagnostic-accuracy study.
- name: Molecular genetic testing
  description: >-
    Founding families were diagnosed through exome sequencing; a later case
    report separately performed segregation analysis after molecular diagnosis.
    The recurrent synonymous allele reported across the founding families was
    shown to induce exon skipping, establishing a splice effect for that allele
    despite its synonymous coding annotation.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Whole-exome sequencing performed on one family with two affected siblings
      and independently on another family with one affected child revealed
      compound-heterozygous mutations in TUBGCP4.
    explanation: >-
      Documents exome-based identification of biallelic variants in independent
      families.
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      One synonymous variant was common to all three families and was shown to
      induce exon skipping
    explanation: >-
      Directly establishes the splice effect of the recurrent synonymous allele.
  - reference: PMID:32270730
    reference_title: TUBGCP4 - associated microcephaly and chorioretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This is a case report of a patient with a molecular diagnosis defined by
      mutations in the TUBGCP4 gene. Segregation analyses were carried out.
    explanation: >-
      Documents a later molecular diagnosis with segregation analysis.
treatments:
- name: Mixed-cohort ophthalmic-genetics surveillance
  description: >-
    Close monitoring by a team experienced in ophthalmic genetics was
    recommended for a mixed KIF11/TUBGCP4/TUBGCP6 cohort. This is a pooled-cohort
    surveillance recommendation, not evidence of TUBGCP4-specific treatment
    efficacy or a TUBGCP4-specific progression rate.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:33137195
    reference_title: Genotype Phenotype Correlation and Variability in Microcephaly Associated With Chorioretinopathy or Familial Exudative Vitreoretinopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Microcephaly due to mutations in KIF11, TUBGCP4, or TUBGCP6 can be
      associated with retinal disease on a spectrum from chorioretinal atrophy
      to FEVR-like posterior segment changes. Visually significant disease
      progression can occur and patients should be monitored closely by a team
      experienced in ophthalmic genetics.
    explanation: >-
      Directly supports close ophthalmic-genetics monitoring in the mixed-gene
      cohort. Only one participant had TUBGCP4 variants, so this does not
      establish TUBGCP4-specific efficacy or progression.
animal_models:
- name: tubgcp4 morpholino knockdown zebrafish
  species: Zebrafish (Danio rerio)
  genotype: tubgcp4 morpholino knockdown
  category: Morpholino knockdown
  description: >-
    Morpholino-treated zebrafish had reduced head volume and eye developmental
    anomalies with chorioretinal dysplasia. This is a transient knockdown model,
    not a stable patient-variant model, and it does not establish the intervening
    human developmental mechanism.
  genes:
  - preferred_term: TUBGCP4
    term:
      id: hgnc:16691
      label: TUBGCP4
  associated_phenotypes:
  - Reduced head volume
  - Eye developmental anomalies
  - Chorioretinal dysplasia
  modeled_mechanisms:
  - target: Hypothesized Impairment of Brain and Eye Development
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      The model reproduces reduced head volume and eye-development abnormalities
      that motivate this tissue-level hypothesis, without establishing the
      proposed developmental route in humans.
    limitations: >-
      This is transient morpholino knockdown in zebrafish rather than a stable
      patient-variant model. The nonhuman organ-level concordance does not
      identify neural or retinal intermediates or establish causality for the
      human phenotypes.
    evidence:
    - reference: PMID:25817018
      reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Moreover, zebrafish treated with morpholinos against tubgcp4 were found
        to have reduced head volume and eye developmental anomalies with
        chorioretinal dysplasia.
      explanation: >-
        Supports the model as partially informative for the developmental
        hypothesis while the translational limitations remain explicit.
  evidence:
  - reference: PMID:25817018
    reference_title: Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Moreover, zebrafish treated with morpholinos against tubgcp4 were found to
      have reduced head volume and eye developmental anomalies with
      chorioretinal dysplasia.
    explanation: >-
      Directly reports the morpholino model and its observed brain and eye
      phenotypes; the limitations are recorded in the model description.
notes: >-
  Deliberately NOT a member of the Tubulinopathies grouping. The grouping's notes
  record TUBGCP genes as out of scope: they encode gamma-tubulin COMPLEX proteins
  rather than tubulin isotypes. If the grouping is ever re-scoped to "tubulin and
  tubulin-complex genes", this entry would need reconsideration.

  The LOSS_OF_FUNCTION assignment reflects reported truncating and deletion
  alleles plus a recurrent synonymous allele shown to alter splicing. Reduced
  gamma-TuRC, altered microtubule behavior, abnormal nuclear shape, and
  aneuploidy are direct patient-fibroblast observations. Their causal connection
  to human neural and retinal development remains a hypothesis.

  Reduced visual acuity, microphthalmia, neurodevelopmental delay, nystagmus,
  and abnormal facial shape are intentionally not connected to the
  pathophysiology graph. They are case-level observations, and the reviewed
  sources do not supply a directional mechanistic bridge for those individual
  features.

  All evidence snippets are quoted from cached abstracts. One mixed-cohort
  ophthalmic-surveillance recommendation is included with explicit limits. No
  TUBGCP4-specific treatment-efficacy, disease-modifying-therapy, recurrence-risk
  percentage, or population phenotype-frequency claim is made because the
  reviewed sources do not directly support one.

📚

References & Deep Research

References

4

PMID:25817018

Mutations in TUBGCP4 alter microtubule organization via the γ-tubulin ring complex in autosomal-recessive microcephaly with chorioretinopathy.

No top-level findings curated for this source.

PMID:32270730

TUBGCP4 - associated microcephaly and chorioretinopathy.

No top-level findings curated for this source.

PMID:37038737

Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature.

No top-level findings curated for this source.

PMID:33137195

Genotype Phenotype Correlation and Variability in Microcephaly Associated With Chorioretinopathy or Familial Exudative Vitreoretinopathy.

No top-level findings curated for this source.

TUBGCP4-related Microcephaly and Chorioretinopathy

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