Usher Syndrome Type 3

🔗

Mappings

MONDO

MONDO:0010170 Usher syndrome type 3A Not Yet Curated

MONDO:0010170 is the CLRN1 form of Usher syndrome type 3 and is a child of this entry's own term MONDO:0016485. It is recorded as a narrowMatch rather than as a has_subtypes row because CLRN1 is the only gene this entry curates as causative, so a one-row subtype list would restate the whole entry. The sibling child term, MONDO:0013788 Usher syndrome type 3B, is deliberately not mapped: its gene HARS1 is curated below with relationship_type DISPUTED on ClinGen's Refuted assertion, so mapping the term would imply coverage of a relationship this entry rejects. MONDO still records HARS1 as the causal gene of MONDO:0013788, which is an upstream disagreement rather than a gap here.

👪

Inheritance

1

Autosomal Recessive HP:0000007

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:11524702 SUPPORT Human Clinical

"Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterized by progressive hearing loss, severe retinal degeneration, and variably present vestibular dysfunction, assigned to 3q21-q25."

Establishes autosomal recessive inheritance and the defining clinical triad of type 3.

⚙

Pathophysiology

4

Clarin-1 Loss of Function

Biallelic loss of clarin-1, a four-transmembrane protein that belongs to neither the upper tip-link density complex nor the ankle-link complex. Its core experimentally supported cellular role is actin filament organization. Because clarin-1 is in neither Usher complex and has no assigned biochemical activity, this node names the protein's loss rather than the disruption of a named assembly - which is the honest form of the claim and is itself the reason type 3 could not share a root node with types 1 and 2.

CLRN1 hgnc:12605

Downstream

Cochlear Hair Bundle Disorganization Clarin-1 is required for cochlear hair cell development; its loss disorganizes the hair bundle.

Müller Glial Support Failure Clarin-1 is expressed in Müller glia rather than photoreceptors, so its loss acts on the retina through glial support rather than through a photoreceptor-intrinsic defect.

Show evidence (1 reference)

PMID:11524702 SUPPORT Human Clinical

"USH3, the candidate gene that we identified, encodes a 120-amino-acid protein."

Identifies the causative gene subsequently named CLRN1.

Cochlear Hair Bundle Disorganization

Progressive loss of cochlear sensory hair cells and deterioration of the organ of Corti. Unlike types 1 and 2, where the lesion is in a structural complex required from the outset, the clarin-1 deficit produces a progressive postnatal loss - which is the mechanistic correlate of the postlingual, progressive audiogram that clinically defines type 3.

cochlea auditory hair cell CL:4023120

CLRN1 hgnc:12605

sensory perception of sound GO:0007605 ↓ DECREASED

spiral organ of Corti UBERON:0002227

Animal models

Clrn1 knockout mouse Mouse (Mus musculus) recapitulates Progressive cochlear sensory hair cell loss with deterioration of the organ of Corti by four months.

Downstream

Progressive Postlingual Sensorineural Hearing Loss Progressive hair cell loss produces hearing loss that develops after speech acquisition and worsens over time.

Vestibular Dysfunction Vestibular involvement is variable in type 3, unlike the constant areflexia of type 1.

Show evidence (1 reference)

PMID:19680541 SUPPORT Model Organism

"Clrn1 KO mice do not develop a retinal degeneration phenotype, but exhibit progressive loss of sensory hair cells in the cochlea and deterioration of the organ of Corti by 4 months."

Establishes the progressive cochlear hair cell loss that this node describes.

Müller Glial Support Failure

Loss of clarin-1 from Müller glia disorganizes actin-based structures of the Müller glia and the outer retina, and leaves photoreceptors unable to withstand cell stress. The cell-type attribution is supported directly in human tissue, and the causal direction - glia to photoreceptor - is supported by a cell-specific rescue experiment in which Müller glial re-expression prevents photoreceptor death while photoreceptor-specific re-expression does not.

Mueller cell CL:0000636

CLRN1 hgnc:12605

retina UBERON:0000966

Animal models

clrn1 mutant zebrafish with cell-specific rescue Zebrafish (Danio rerio) rescues Müller glial re-expression prevents light-induced photoreceptor death; rod- or cone-specific re-expression does not.

Downstream

Photoreceptor Degeneration Loss of Müller glial support is followed by photoreceptor stress sensitivity and degeneration.

Show evidence (2 references)

PMID:40067805 SUPPORT Model Organism

"Investigation revealed disorganization in the outer retina in clrn1 mutants, including actin-based structures of the Müller glia and photoreceptor cells."

Establishes the outer-retinal and Müller glial disorganization that this node describes.

PMID:31625146 SUPPORT In Vitro

"The pattern of Clrn1 mRNA cellular expression is similar in both mouse and human adult retina, with CLRN1 transcripts being localized in Müller glia, and not photoreceptors."

Establishes the cell-type attribution underlying this node. Graded IN_VITRO: ex vivo retinal tissue, not a patient cohort.

Photoreceptor Degeneration

Progressive photoreceptor degeneration with variable onset, secondary to loss of Müller glial support rather than to a photoreceptor-intrinsic defect.

photoreceptor cell CL:0000210

visual perception GO:0007601 ↓ DECREASED

Animal models

Clrn1 knockout mouse Mouse (Mus musculus) fails to recapitulate The model does not reproduce the human retinal phenotype.

Downstream

Retinitis Pigmentosa Progressive photoreceptor loss manifests clinically as retinitis pigmentosa.

Night Blindness Early rod loss produces nyctalopia, typically the first retinal symptom.

Constricted Visual Fields Mid-peripheral rod loss constricts the visual field.

Show evidence (1 reference)

PMID:40067805 SUPPORT Model Organism

"The retinas of clrn1 mutant larvae exhibited sensitivity to cell stress, along with age-dependent loss of function and degeneration in the photoreceptor layer."

Establishes age-dependent photoreceptor degeneration following clarin-1 loss.

⬡

Pathograph

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

●

Phenotypes

5

Ear 2

Progressive Postlingual Sensorineural Hearing Loss Progressive sensorineural hearing impairment HP:0000408

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:15521980 SUPPORT Human Clinical

"Usher syndrome type III is an autosomal recessive disorder clinically characterized by the association of retinitis pigmentosa (RP), variable presence of vestibular dysfunction and progressive hearing loss, being the progression of the hearing impairment the critical parameter classically used..."

States both the progressive hearing loss and its role as the classical discriminator.

Vestibular Dysfunction Abnormal vestibular function HP:0001751

Show evidence (1 reference)

PMID:11524702 SUPPORT Human Clinical

"Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterized by progressive hearing loss, severe retinal degeneration, and variably present vestibular dysfunction, assigned to 3q21-q25."

Establishes variably present vestibular dysfunction in type 3.

Eye 3

Retinitis Pigmentosa Rod-cone dystrophy HP:0000510

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:15521980 SUPPORT Human Clinical

"Usher syndrome type III is an autosomal recessive disorder clinically characterized by the association of retinitis pigmentosa (RP), variable presence of vestibular dysfunction and progressive hearing loss, being the progression of the hearing impairment the critical parameter classically used..."

Establishes retinitis pigmentosa as a defining type-3 feature.

Night Blindness Nyctalopia HP:0000662

Show evidence (1 reference)

PMID:32995707 SUPPORT Human Clinical

"Typically, the first presenting symptom is night blindness (nyctalopia) with progressive visual field loss beginning in the mid-periphery caused by rod photoreceptor degeneration."

Documents nyctalopia as the first presenting retinal symptom.

Constricted Visual Fields Constriction of peripheral visual field HP:0001133

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:32995707 SUPPORT Human Clinical

"Typically, the first presenting symptom is night blindness (nyctalopia) with progressive visual field loss beginning in the mid-periphery caused by rod photoreceptor degeneration."

Documents progressive mid-peripheral visual field loss.

🧬

Genetic Associations

2

CLRN1 (Causative)

Gene: CLRN1 hgnc:12605 relationship_type: CAUSATIVE

Show evidence (3 references)

PMID:11524702 SUPPORT Human Clinical

"USH3, the candidate gene that we identified, encodes a 120-amino-acid protein."

Identifies the type-3 causative gene subsequently named CLRN1.

PMID:32995707 SUPPORT Human Clinical

"Usher syndrome has three subtypes, each being clinically and genetically heterogeneous characterised by sensorineural hearing loss and retinitis pigmentosa (RP), with or without vestibular dysfunction."

Places type 3 within the Usher family as a genetically distinct subtype.

PMID:12080385 SUPPORT Human Clinical

"The full length USH3A transcript encodes clarin-1, a four-transmembrane-domain protein, which defines a novel vertebrate-specific family of three paralogues."

Establishes that the USH3A transcript encodes clarin-1, which is the gene-to-locus assignment behind the MONDO:0010170 narrowMatch recorded in this entry's mappings block.

HARS1 (Not causative)

Gene: HARS1 hgnc:4816 relationship_type: DISPUTED

Show evidence (3 references)

CGGV:assertion_ca3372fa-f205-44e5-8bd9-6c64c40ebd93-2018-02-27T170000.000Z REFUTE Other

ClinGen refutes HARS1 as a cause of Usher syndrome type 3.

PMID:28632987 SUPPORT BACKGROUND Other

"HARS has been implicated in the human syndromes Charcot-Marie-Tooth (CMT) Type 2W and Type IIIB Usher (USH3B)."

Records that the USH3B proposal existed, which is the part of this record's claim that is true. It is NOT support for HARS1 causing type 3: the sentence restates the gene-disease assignment the paper works from, and ClinGen's Hearing Loss Gene Curation Expert Panel subsequently classified that relationship Refuted, which is the verdict this record follows.

PMID:28632987 SUPPORT In Vitro

"The thermal sensitivity associated with the Y454S mutation represents a biochemical basis for understanding USH3B."

The functional argument the refuted USH3B proposal rested on, recorded so that a later curator can see what was weighed rather than only that a verdict was reached. Again not support for causation: ClinGen assessed the gene-disease relationship after this work and refuted it, and a mechanism proposed for a refuted relationship does not revive it.

💊

Medical Actions

3

Hearing Aids and Cochlear Implantation

Platform: Device

Amplification early, implantation later. The sequencing is specific to this entity and follows from its mechanism: the deficit is a PROGRESSIVE postnatal hair cell loss, so hearing aids are useful while enough hair cells remain and cochlear implantation becomes indicated as the loss advances. Types 1 and 2 do not have this trajectory - type 1 goes to implantation early because the loss is profound from birth, and type 2's sloping loss is usually managed with amplification throughout.

Target Phenotypes: Progressive sensorineural hearing impairment HP:0000408

Show evidence (2 references)

PMID:32995707 SUPPORT Human Clinical

"Hearing aids are of benefit early in the course of disease, but cochlear implants may be required with progressive hearing loss."

States the amplification-then-implantation sequence, in the review's own Usher 3 section rather than as generic Usher management.

PMID:32995707 SUPPORT Human Clinical

"Improved hearing and subjective benefit were demonstrated in Usher 3 patients with implants (mean age at implantation: 41 years) comparable with that observed in implanted patients without visual impairment."

Reports implantation outcomes measured in type-3 patients specifically, including the late mean age at implantation that the progressive course produces.

Genetic Counseling

Action: Genetic Counseling NCIT:C15240

Genetic counseling addresses the autosomal recessive recurrence risk and informs reproductive decision-making.

Show evidence (1 reference)

PMID:33193648 SUPPORT Human Clinical

"Usher syndrome (USH) is an autosomal recessive (AR) disorder that permanently and severely affects the senses of hearing, vision, and balance."

Supports counseling for the autosomal recessive recurrence risk.

Investigational Gene-Directed Therapy

Action: Gene Therapy NCIT:C15238

No approved treatment exists for the retinal degeneration. Gene replacement, gene editing, antisense oligonucleotides and small molecules are in development across the Usher entities. The Müller glial localization of clarin-1 has a direct consequence for this entity that does not apply to types 1 and 2: a retinal gene therapy would need to reach Müller glia, not photoreceptors. The zebrafish rescue experiment cited on the Müller glial node is the evidence for that targeting requirement.

Show evidence (1 reference)

PMID:32995707 SUPPORT Human Clinical

"While there is currently no available approved treatment for the RP, various therapeutic strategies are in development or in clinical trials for Usher syndrome, including gene replacement, gene editing, antisense oligonucleotides and small molecule drugs."

Documents that no approved retinal treatment exists and names the strategies in development.

🔬

Diagnosis

1

Serial audiometry with retinal functional evaluation

Type 3 is distinguished from types 1 and 2 by the COURSE of the hearing loss rather than by its severity at any single time point, so a single audiogram cannot make the distinction and serial testing is required.

Results: Progressive postlingual hearing loss with variable vestibular findings and retinitis pigmentosa. Phenotypic variability means clinical typing does not reliably identify every CLRN1 family.

Show evidence (1 reference)

PMID:15521980 SUPPORT Human Clinical

"Usher syndrome type III is an autosomal recessive disorder clinically characterized by the association of retinitis pigmentosa (RP), variable presence of vestibular dysfunction and progressive hearing loss, being the progression of the hearing impairment the critical parameter classically used..."

Establishes hearing-loss progression as the classical clinical discriminator for type 3.

🐁

Animal Models

2

Clrn1 knockout mouse Constitutive knockout

Reproduces the cochlear arm of type 3 and explicitly fails to reproduce the retinal arm. Both results are informative, and the negative one is the more useful of the two: it is the observation that redirected the field toward Müller glia.

Species

Mouse (Mus musculus)

Genotype

Clrn1 knockout

Pathograph links

Cochlear Hair Bundle Disorganization recapitulates fidelity: moderate observes: tissue Progressive cochlear sensory hair cell loss with deterioration of the organ of Corti by four months.

Show evidence (1 reference)

PMID:19680541 SUPPORT Model Organism

"Clrn1 KO mice do not develop a retinal degeneration phenotype, but exhibit progressive loss of sensory hair cells in the cochlea and deterioration of the organ of Corti by 4 months."

Establishes that the model reproduces the cochlear mechanism.

Photoreceptor Degeneration fails to recapitulate fidelity: low observes: tissue The model does not reproduce the human retinal phenotype.

Limitations: Clrn1-null mice develop no retinal degeneration, so the model cannot report on the retinal arm of this entity and a negative retinal result in it is uninformative about human disease. Mouse Clrn1 mRNA is also developmentally downregulated in the adult retina, detectable only by sensitive assays, which compounds the problem.

Show evidence (1 reference)

PMID:19680541 SUPPORT Model Organism

"Clrn1 KO mice do not develop a retinal degeneration phenotype, but exhibit progressive loss of sensory hair cells in the cochlea and deterioration of the organ of Corti by 4 months."

Directly states the absent retinal phenotype.

Show evidence (1 reference)

PMID:19680541 SUPPORT Model Organism

"In contrast to mouse KO models of USH1 and USH2, our data indicate that Clrn1 expression in the retina is restricted to the Müller glia."

The same study that reports the absent retinal phenotype also reports the cell-type restriction that explains it.

clrn1 mutant zebrafish with cell-specific rescue Knockout with cell-type-specific rescue

The model that establishes the causal direction of the retinal mechanism. Its value is the contrast between the two rescue arms rather than either arm alone.

Species

Zebrafish (Danio rerio)

Genotype

CRISPR/Cas9 deletion of zebrafish clrn1, with Müller-glia-specific or photoreceptor-specific clrn1 re-expression

Pathograph links

Müller Glial Support Failure rescues fidelity: moderate observes: cellular Müller glial re-expression prevents light-induced photoreceptor death; rod- or cone-specific re-expression does not.

Limitations: Larval zebrafish under high-intensity light stress is an acute challenge paradigm, not the decades-long degeneration of human type 3, and the rescue is a re-expression experiment rather than a therapeutic delivery.

Readouts

Light-induced retinal cell death

Direction: RESTORED

Interpretation: Cell death returns toward baseline with glial re-expression, establishing the glial compartment as where clarin-1 acts.

Show evidence (1 reference)

PMID:40067805 SUPPORT Model Organism

"Müller glia re-expression of clrn1 prevented the elevated cell death observed in larval clrn1 mutant zebrafish exposed to high-intensity light."

Reports the measured rescue.

Show evidence (1 reference)

PMID:40067805 SUPPORT Model Organism

"Notably, the degree of phenotypic rescue correlated with the level of Clrn1 re-expression."

The dose-response relationship strengthens the attribution of the rescue to clarin-1 re-expression rather than to the manipulation.

Show evidence (1 reference)

PMID:40067805 SUPPORT Model Organism

"To assess cell-specific contributions to USH3A pathology, we specifically re-expressed clrn1 in either Müller glia or photoreceptor cells."

Describes the cell-specific rescue design that makes this model informative.

{ }

Source YAML

click to show

name: Usher Syndrome Type 3
creation_date: "2026-09-24T00:00:00Z"
category: Mendelian
synonyms:
- USH3
- USH3A
- Usher syndrome type III
- Usher syndrome type 3
description: >
  Usher syndrome type 3 is the mechanism entity caused by biallelic loss of
  clarin-1 (CLRN1), producing progressive postlingual sensorineural hearing loss,
  variable vestibular dysfunction, and variable-onset retinitis pigmentosa.

  Clarin-1 is the outlier of the Usher proteins, and that is the reason this is a
  separate entity rather than a third clinical grade of one disease. It belongs
  to neither the upper tip-link density complex of type 1 nor the ankle-link
  complex of type 2. Its core experimentally supported role is actin filament
  organization, and the in vivo support for it is the disorganized stereocilia of
  Clrn1-null mice.

  The retinal arm diverges even further. Clarin-1 is expressed in MÜLLER GLIA,
  not photoreceptors, in both mouse and human adult retina - so the type-3
  retinal mechanism is a glial support failure that causes photoreceptor loss
  secondarily, rather than a photoreceptor-intrinsic defect. In zebrafish,
  re-expressing clarin-1 in Müller glia rescues light-induced retinal cell death
  while rod- or cone-specific re-expression does not. A single "photoreceptor
  connecting cilium dysfunction" node, as the previously lumped Usher entry
  carried, was simply wrong for this entity: clarin-1 is not in photoreceptors.

  The clinical typing is an imperfect proxy for the mechanism in both directions
  here. A Spanish series reported clarin-1 phenotypic variability such that the
  progression of hearing impairment, the parameter classically used to separate
  type 3 from types 1 and 2, does not cleanly assign every CLRN1 family.
disease_term:
  preferred_term: Usher syndrome type 3
  term:
    id: MONDO:0016485
    label: Usher syndrome type 3
parents:
- Inherited retinal dystrophy
- Sensorineural hearing loss
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0010170
      label: Usher syndrome type 3A
    mapping_predicate: skos:narrowMatch
    mapping_source: MONDO
    mapping_justification: >-
      MONDO:0010170 is the CLRN1 form of Usher syndrome type 3 and is a child of this
      entry's own term MONDO:0016485. It is recorded as a narrowMatch rather than as a
      has_subtypes row because CLRN1 is the only gene this entry curates as causative, so a
      one-row subtype list would restate the whole entry. The sibling child term,
      MONDO:0013788 Usher syndrome type 3B, is deliberately not mapped: its gene HARS1 is
      curated below with relationship_type DISPUTED on ClinGen's Refuted assertion, so
      mapping the term would imply coverage of a relationship this entry rejects. MONDO
      still records HARS1 as the causal gene of MONDO:0013788, which is an upstream
      disagreement rather than a gap here.
references:
- reference: PMID:11524702
  title: Mutations in a novel gene with transmembrane domains underlie Usher syndrome type 3.
- reference: PMID:15521980
  title: "Mutation screening of USH3 gene (clarin-1) in Spanish patients with Usher syndrome: low prevalence and phenotypic variability."
- reference: PMID:19680541
  title: CLRN1 is nonessential in the mouse retina but is required for cochlear hair cell development.
- reference: PMID:31625146
  title: Clarin-1 expression in adult mouse and human retina highlights a role of Müller glia in Usher syndrome.
- reference: PMID:32995707
  title: "Usher syndrome: clinical features, molecular genetics and advancing therapeutics."
- reference: PMID:33193648
  title: "Usher Syndrome: Genetics and Molecular Links of Hearing Loss and Directions for Therapy."
- reference: PMID:40067805
  title: The USH3A causative gene clarin1 functions in Müller glia to maintain retinal photoreceptors.
- reference: CGGV:assertion_ca3372fa-f205-44e5-8bd9-6c64c40ebd93-2018-02-27T170000.000Z
  title: "HARS1 / Usher syndrome type 3 (Refuted)"
- reference: PMID:30531642
  title: "Genetics of Usher Syndrome: New Insights From a Meta-analysis."
- reference: PMID:12080385
  title: "USH3A transcripts encode clarin-1, a four-transmembrane-domain protein with a possible role in sensory synapses."
- reference: PMID:28632987
  title: The Usher Syndrome Type IIIB Histidyl-tRNA Synthetase Mutation Confers Temperature Sensitivity.
inheritance:
- name: Autosomal Recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:11524702
    reference_title: "Mutations in a novel gene with transmembrane domains underlie Usher syndrome type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterized by \nprogressive hearing loss, severe retinal degeneration, and variably present \nvestibular dysfunction, assigned to 3q21-q25."
    explanation: Establishes autosomal recessive inheritance and the defining clinical triad of type 3.
pathophysiology:
- name: Clarin-1 Loss of Function
  genes:
  - preferred_term: CLRN1
    term:
      id: hgnc:12605
      label: CLRN1
  description: >-
    Biallelic loss of clarin-1, a four-transmembrane protein that belongs to
    neither the upper tip-link density complex nor the ankle-link complex. Its
    core experimentally supported cellular role is actin filament organization.

    Because clarin-1 is in neither Usher complex and has no assigned biochemical
    activity, this node names the protein's loss rather than the disruption of a
    named assembly - which is the honest form of the claim and is itself the
    reason type 3 could not share a root node with types 1 and 2.
  biological_scale: MOLECULAR
  downstream:
  - target: Cochlear Hair Bundle Disorganization
    description: >-
      Clarin-1 is required for cochlear hair cell development; its loss
      disorganizes the hair bundle.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:19680541
      reference_title: CLRN1 is nonessential in the mouse retina but is required for cochlear hair cell development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Clrn1 KO mice do not develop a retinal degeneration phenotype, but exhibit progressive loss of sensory hair cells in the cochlea and deterioration of the organ of Corti by 4 months."
      explanation: >-
        Establishes the cochlear requirement for clarin-1. The same sentence is the
        primary evidence that the mouse retina does not model this entity.
  - target: Müller Glial Support Failure
    description: >-
      Clarin-1 is expressed in Müller glia rather than photoreceptors, so its loss
      acts on the retina through glial support rather than through a
      photoreceptor-intrinsic defect.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:31625146
      reference_title: Clarin-1 expression in adult mouse and human retina highlights a role of Müller glia in Usher syndrome.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "The pattern of Clrn1 mRNA cellular expression is similar in both mouse and human adult retina, with CLRN1 transcripts being localized in Müller glia, and not photoreceptors."
      explanation: >-
        Establishes the cell type, by RNAscope in situ hybridization on retinal
        tissue sections plus single-cell RNA-seq. Graded IN_VITRO rather than
        HUMAN_CLINICAL: the human material is post-mortem retinal tissue assayed
        ex vivo, not a patient cohort, and the quoted sentence reports mouse and
        human together.
  evidence:
  - reference: PMID:11524702
    reference_title: "Mutations in a novel gene with transmembrane domains underlie Usher syndrome type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "USH3, the candidate gene that we \nidentified, encodes a 120-amino-acid protein."
    explanation: Identifies the causative gene subsequently named CLRN1.
- name: Cochlear Hair Bundle Disorganization
  genes:
  - preferred_term: CLRN1
    term:
      id: hgnc:12605
      label: CLRN1
  description: >-
    Progressive loss of cochlear sensory hair cells and deterioration of the organ
    of Corti. Unlike types 1 and 2, where the lesion is in a structural complex
    required from the outset, the clarin-1 deficit produces a progressive
    postnatal loss - which is the mechanistic correlate of the postlingual,
    progressive audiogram that clinically defines type 3.
  biological_scale: TISSUE
  conforms_to: "sensorineural_hair_cell_loss#Hair Cell Mechanotransduction Failure and Death"
  cell_types:
  - preferred_term: cochlea auditory hair cell
    term:
      id: CL:4023120
      label: cochlea auditory hair cell
  locations:
  - preferred_term: spiral organ of Corti
    term:
      id: UBERON:0002227
      label: spiral organ of cochlea
  biological_processes:
  - preferred_term: sensory perception of sound
    term:
      id: GO:0007605
      label: sensory perception of sound
    modifier: DECREASED
  downstream:
  - target: Progressive Postlingual Sensorineural Hearing Loss
    description: >-
      Progressive hair cell loss produces hearing loss that develops after speech
      acquisition and worsens over time.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:11524702
      reference_title: "Mutations in a novel gene with transmembrane domains underlie Usher syndrome type 3."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterized by \nprogressive hearing loss, severe retinal degeneration, and variably present \nvestibular dysfunction, assigned to 3q21-q25."
      explanation: Establishes progressive hearing loss as the defining type-3 auditory course.
  - target: Vestibular Dysfunction
    description: >-
      Vestibular involvement is variable in type 3, unlike the constant areflexia
      of type 1.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:11524702
      reference_title: "Mutations in a novel gene with transmembrane domains underlie Usher syndrome type 3."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterized by \nprogressive hearing loss, severe retinal degeneration, and variably present \nvestibular dysfunction, assigned to 3q21-q25."
      explanation: Establishes variable rather than constant vestibular dysfunction in type 3.
  evidence:
  - reference: PMID:19680541
    reference_title: CLRN1 is nonessential in the mouse retina but is required for cochlear hair cell development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Clrn1 KO mice do not develop a retinal degeneration phenotype, but exhibit progressive loss of sensory hair cells in the cochlea and deterioration of the organ of Corti by 4 months."
    explanation: Establishes the progressive cochlear hair cell loss that this node describes.
- name: Müller Glial Support Failure
  genes:
  - preferred_term: CLRN1
    term:
      id: hgnc:12605
      label: CLRN1
  description: >-
    Loss of clarin-1 from Müller glia disorganizes actin-based structures of the
    Müller glia and the outer retina, and leaves photoreceptors unable to
    withstand cell stress. The cell-type attribution is supported directly in
    human tissue, and the causal direction - glia to photoreceptor - is supported
    by a cell-specific rescue experiment in which Müller glial re-expression
    prevents photoreceptor death while photoreceptor-specific re-expression does
    not.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Mueller cell
    term:
      id: CL:0000636
      label: Mueller cell
  locations:
  - preferred_term: retina
    term:
      id: UBERON:0000966
      label: retina
  downstream:
  - target: Photoreceptor Degeneration
    description: >-
      Loss of Müller glial support is followed by photoreceptor stress sensitivity
      and degeneration.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:40067805
      reference_title: The USH3A causative gene clarin1 functions in Müller glia to maintain retinal photoreceptors.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Müller glia re-expression of clrn1 prevented the elevated cell death observed in larval clrn1 mutant zebrafish exposed to high-intensity light."
      explanation: >-
        Cell-specific rescue establishes that the glial compartment is where
        clarin-1 acts to protect photoreceptors.
    - reference: PMID:40067805
      reference_title: The USH3A causative gene clarin1 functions in Müller glia to maintain retinal photoreceptors.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "However, rod- or cone-specific Clrn1 re-expression did not reduce the extent of cell death."
      explanation: >-
        The negative arm of the same rescue experiment rules out a
        photoreceptor-intrinsic requirement, which is what distinguishes this
        retinal mechanism from those of types 1 and 2.
  evidence:
  - reference: PMID:40067805
    reference_title: The USH3A causative gene clarin1 functions in Müller glia to maintain retinal photoreceptors.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Investigation revealed disorganization in the outer retina in clrn1 mutants, including actin-based structures of the Müller glia and photoreceptor cells."
    explanation: Establishes the outer-retinal and Müller glial disorganization that this node describes.
  - reference: PMID:31625146
    reference_title: Clarin-1 expression in adult mouse and human retina highlights a role of Müller glia in Usher syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The pattern of Clrn1 mRNA cellular expression is similar in both mouse and human adult retina, with CLRN1 transcripts being localized in Müller glia, and not photoreceptors."
    explanation: >-
      Establishes the cell-type attribution underlying this node. Graded IN_VITRO:
      ex vivo retinal tissue, not a patient cohort.
- name: Photoreceptor Degeneration
  description: >-
    Progressive photoreceptor degeneration with variable onset, secondary to loss
    of Müller glial support rather than to a photoreceptor-intrinsic defect.
  biological_scale: TISSUE
  conforms_to: "photoreceptor_degeneration#Rod Photoreceptor Apoptosis"
  cell_types:
  - preferred_term: photoreceptor cell
    term:
      id: CL:0000210
      label: photoreceptor cell
  biological_processes:
  - preferred_term: visual perception
    term:
      id: GO:0007601
      label: visual perception
    modifier: DECREASED
  downstream:
  - target: Retinitis Pigmentosa
    description: Progressive photoreceptor loss manifests clinically as retinitis pigmentosa.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:11524702
      reference_title: "Mutations in a novel gene with transmembrane domains underlie Usher syndrome type 3."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterized by \nprogressive hearing loss, severe retinal degeneration, and variably present \nvestibular dysfunction, assigned to 3q21-q25."
      explanation: Establishes severe retinal degeneration as a defining type-3 feature.
  - target: Night Blindness
    description: Early rod loss produces nyctalopia, typically the first retinal symptom.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32995707
      reference_title: "Usher syndrome: clinical features, molecular genetics and advancing therapeutics."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Typically, the first presenting symptom is night blindness (nyctalopia) with progressive visual field loss beginning in the mid-periphery caused by rod photoreceptor degeneration."
      explanation: Attributes nyctalopia to rod photoreceptor degeneration and names it the first symptom.
  - target: Constricted Visual Fields
    description: Mid-peripheral rod loss constricts the visual field.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32995707
      reference_title: "Usher syndrome: clinical features, molecular genetics and advancing therapeutics."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Typically, the first presenting symptom is night blindness (nyctalopia) with progressive visual field loss beginning in the mid-periphery caused by rod photoreceptor degeneration."
      explanation: Attributes progressive mid-peripheral field loss to rod photoreceptor degeneration.
  evidence:
  - reference: PMID:40067805
    reference_title: The USH3A causative gene clarin1 functions in Müller glia to maintain retinal photoreceptors.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The retinas of clrn1 mutant larvae exhibited sensitivity to cell stress, along with age-dependent loss of function and degeneration in the photoreceptor layer."
    explanation: Establishes age-dependent photoreceptor degeneration following clarin-1 loss.
phenotypes:
- category: Auditory
  name: Progressive Postlingual Sensorineural Hearing Loss
  description: >-
    Hearing loss that develops after speech acquisition and worsens over time.
    The progression of the hearing impairment is the parameter classically used to
    separate type 3 from types 1 and 2.
  phenotype_term:
    preferred_term: Progressive sensorineural hearing impairment
    term:
      id: HP:0000408
      label: Progressive sensorineural hearing impairment
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:15521980
    reference_title: "Mutation screening of USH3 gene (clarin-1) in Spanish patients with Usher syndrome: low prevalence and phenotypic variability."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Usher syndrome type III is an autosomal recessive disorder clinically characterized by the association of retinitis pigmentosa (RP), variable presence of vestibular dysfunction and progressive hearing loss, being the progression of the hearing impairment the critical parameter classically used to distinguish this form from Usher syndrome type I and Usher syndrome type II."
    explanation: States both the progressive hearing loss and its role as the classical discriminator.
- category: Vestibular
  name: Vestibular Dysfunction
  description: >-
    Vestibular involvement is variably present, in contrast to the constant
    areflexia of type 1 and the generally intact function of type 2.
  phenotype_term:
    preferred_term: Abnormal vestibular function
    term:
      id: HP:0001751
      label: Abnormal vestibular function
  evidence:
  - reference: PMID:11524702
    reference_title: "Mutations in a novel gene with transmembrane domains underlie Usher syndrome type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterized by \nprogressive hearing loss, severe retinal degeneration, and variably present \nvestibular dysfunction, assigned to 3q21-q25."
    explanation: Establishes variably present vestibular dysfunction in type 3.
- category: Ophthalmologic
  name: Retinitis Pigmentosa
  description: >-
    Progressive rod-cone dystrophy with variable onset.
  phenotype_term:
    preferred_term: Rod-cone dystrophy
    term:
      id: HP:0000510
      label: Rod-cone dystrophy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:15521980
    reference_title: "Mutation screening of USH3 gene (clarin-1) in Spanish patients with Usher syndrome: low prevalence and phenotypic variability."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Usher syndrome type III is an autosomal recessive disorder clinically characterized by the association of retinitis pigmentosa (RP), variable presence of vestibular dysfunction and progressive hearing loss, being the progression of the hearing impairment the critical parameter classically used to distinguish this form from Usher syndrome type I and Usher syndrome type II."
    explanation: Establishes retinitis pigmentosa as a defining type-3 feature.
- category: Ophthalmologic
  name: Night Blindness
  description: >-
    Nyctalopia is typically the first retinal symptom, reflecting the
    rod-predominant onset of the degeneration.
  phenotype_term:
    preferred_term: Nyctalopia
    term:
      id: HP:0000662
      label: Nyctalopia
  evidence:
  - reference: PMID:32995707
    reference_title: "Usher syndrome: clinical features, molecular genetics and advancing therapeutics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typically, the first presenting symptom is night blindness (nyctalopia) with progressive visual field loss beginning in the mid-periphery caused by rod photoreceptor degeneration."
    explanation: Documents nyctalopia as the first presenting retinal symptom.
- category: Ophthalmologic
  name: Constricted Visual Fields
  description: >-
    Progressive visual field loss beginning in the mid-periphery.
  phenotype_term:
    preferred_term: Constriction of peripheral visual field
    term:
      id: HP:0001133
      label: Constriction of peripheral visual field
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:32995707
    reference_title: "Usher syndrome: clinical features, molecular genetics and advancing therapeutics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typically, the first presenting symptom is night blindness (nyctalopia) with progressive visual field loss beginning in the mid-periphery caused by rod photoreceptor degeneration."
    explanation: Documents progressive mid-peripheral visual field loss.
genetic:
- name: CLRN1
  association: Causative
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: CLRN1
    term:
      id: hgnc:12605
      label: CLRN1
  features: >-
    Clarin-1, a four-transmembrane protein belonging to neither Usher complex.
    ClinGen's Hearing Loss Gene Curation Expert Panel classifies the
    CLRN1-Usher-syndrome-type-3 relationship as Definitive; that assertion
    predates the CGGV identifier scheme and is recorded under a CGGCIEX
    identifier, which the repository's ClinGen cache builder does not index, so it
    is not cited as a structured reference here.
  case_fractions:
  - population: >-
      Usher syndrome of all types: 684 patients pooled from 11 next-generation sequencing
      studies
    case_fraction_percent: 2.0
    cohort_size: 684
    notes: >-
      14 of 684 patients carried biallelic variants in this gene. The denominator is
      all Usher syndrome rather than this entry's clinical type, because that is the
      cohort the meta-analysis reports.
    evidence:
    - reference: PMID:30531642
      reference_title: "Genetics of Usher Syndrome: New Insights From a Meta-analysis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "the biallelic disease-causing mutation rate was assessed for each Usher gene to propose a classification by frequency: USH2A: 50% (341/684) of patients, MYO7A: 21% (144/684), CDH23: 6% (39/684), ADGRV1: 5% (35/684), PCDH15: 3% (21/684), USH1C: 2% (17/684), CLRN1: 2% (14/684), USH1G: 1% (9/684), WHRN: 0.4% (3/684), PDZD7 0.1% (1/684), CIB2 (0/684)"
      explanation: Meta-analysis biallelic mutation rate for this gene across all Usher syndrome patients.
  evidence:
  - reference: PMID:11524702
    reference_title: "Mutations in a novel gene with transmembrane domains underlie Usher syndrome type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "USH3, the candidate gene that we \nidentified, encodes a 120-amino-acid protein."
    explanation: Identifies the type-3 causative gene subsequently named CLRN1.
  - reference: PMID:32995707
    reference_title: "Usher syndrome: clinical features, molecular genetics and advancing therapeutics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Usher syndrome has three subtypes, each being clinically and genetically heterogeneous characterised by sensorineural hearing loss and retinitis pigmentosa (RP), with or without vestibular dysfunction."
    explanation: Places type 3 within the Usher family as a genetically distinct subtype.
  - reference: PMID:12080385
    reference_title: "USH3A transcripts encode clarin-1, a four-transmembrane-domain protein with a possible role in sensory synapses."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The full length USH3A transcript encodes clarin-1, a four-transmembrane-domain protein, which defines a novel vertebrate-specific family of three paralogues."
    explanation: >-
      Establishes that the USH3A transcript encodes clarin-1, which is the gene-to-locus
      assignment behind the MONDO:0010170 narrowMatch recorded in this entry's mappings
      block.
- name: HARS1
  association: Not causative
  relationship_type: DISPUTED
  gene_term:
    preferred_term: HARS1
    term:
      id: hgnc:4816
      label: HARS1
  features: >-
    HARS1 was previously proposed as a type-3 gene (USH3B). ClinGen's Hearing Loss
    Gene Curation Expert Panel Refuted the relationship in 2018. Recorded because a
    refuted gene-disease relationship is a curation result worth keeping: it stops
    HARS1 being re-added to a type-3 panel or to this entry.
  evidence:
  - reference: CGGV:assertion_ca3372fa-f205-44e5-8bd9-6c64c40ebd93-2018-02-27T170000.000Z
    reference_title: "HARS1 / Usher syndrome type 3 (Refuted)"
    supports: REFUTE
    evidence_source: OTHER
    snippet: "HARS1 | HGNC:4816 | Usher syndrome type 3 | MONDO:0016485 | AR | Refuted | SOP5 | Hearing Loss Gene Curation Expert Panel"
    explanation: ClinGen refutes HARS1 as a cause of Usher syndrome type 3.
  - reference: PMID:28632987
    reference_title: The Usher Syndrome Type IIIB Histidyl-tRNA Synthetase Mutation Confers Temperature Sensitivity.
    supports: SUPPORT
    quote_role: BACKGROUND
    evidence_source: OTHER
    snippet: "HARS has been implicated in the human syndromes Charcot-Marie-Tooth (CMT) Type 2W and Type IIIB Usher (USH3B)."
    explanation: >-
      Records that the USH3B proposal existed, which is the part of this record's claim that
      is true. It is NOT support for HARS1 causing type 3: the sentence restates the
      gene-disease assignment the paper works from, and ClinGen's Hearing Loss Gene Curation
      Expert Panel subsequently classified that relationship Refuted, which is the verdict
      this record follows.
  - reference: PMID:28632987
    reference_title: The Usher Syndrome Type IIIB Histidyl-tRNA Synthetase Mutation Confers Temperature Sensitivity.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The thermal sensitivity associated with the Y454S mutation represents a biochemical basis for understanding USH3B."
    explanation: >-
      The functional argument the refuted USH3B proposal rested on, recorded so that a later
      curator can see what was weighed rather than only that a verdict was reached. Again
      not support for causation: ClinGen assessed the gene-disease relationship after this
      work and refuted it, and a mechanism proposed for a refuted relationship does not
      revive it.
diagnosis:
- name: Serial audiometry with retinal functional evaluation
  description: >-
    Type 3 is distinguished from types 1 and 2 by the COURSE of the hearing loss
    rather than by its severity at any single time point, so a single audiogram
    cannot make the distinction and serial testing is required.
  results: >-
    Progressive postlingual hearing loss with variable vestibular findings and
    retinitis pigmentosa. Phenotypic variability means clinical typing does not
    reliably identify every CLRN1 family.
  evidence:
  - reference: PMID:15521980
    reference_title: "Mutation screening of USH3 gene (clarin-1) in Spanish patients with Usher syndrome: low prevalence and phenotypic variability."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Usher syndrome type III is an autosomal recessive disorder clinically characterized by the association of retinitis pigmentosa (RP), variable presence of vestibular dysfunction and progressive hearing loss, being the progression of the hearing impairment the critical parameter classically used to distinguish this form from Usher syndrome type I and Usher syndrome type II."
    explanation: Establishes hearing-loss progression as the classical clinical discriminator for type 3.
treatments:
- name: Hearing Aids and Cochlear Implantation
  description: >-
    Amplification early, implantation later. The sequencing is specific to this
    entity and follows from its mechanism: the deficit is a PROGRESSIVE postnatal
    hair cell loss, so hearing aids are useful while enough hair cells remain and
    cochlear implantation becomes indicated as the loss advances. Types 1 and 2
    do not have this trajectory - type 1 goes to implantation early because the
    loss is profound from birth, and type 2's sloping loss is usually managed with
    amplification throughout.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: hearing amplification and cochlear device implantation
  target_phenotypes:
  - preferred_term: Progressive sensorineural hearing impairment
    term:
      id: HP:0000408
      label: Progressive sensorineural hearing impairment
  evidence:
  - reference: PMID:32995707
    reference_title: "Usher syndrome: clinical features, molecular genetics and advancing therapeutics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hearing aids are of benefit early in the course of disease, but cochlear implants may be required with progressive hearing loss."
    explanation: >-
      States the amplification-then-implantation sequence, in the review's own
      Usher 3 section rather than as generic Usher management.
  - reference: PMID:32995707
    reference_title: "Usher syndrome: clinical features, molecular genetics and advancing therapeutics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Improved hearing and subjective benefit were demonstrated in Usher 3 patients with implants (mean age at implantation: 41 years) comparable with that observed in implanted patients without visual impairment."
    explanation: >-
      Reports implantation outcomes measured in type-3 patients specifically,
      including the late mean age at implantation that the progressive course
      produces.
- name: Genetic Counseling
  description: >-
    Genetic counseling addresses the autosomal recessive recurrence risk and
    informs reproductive decision-making.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:33193648
    reference_title: "Usher Syndrome: Genetics and Molecular Links of Hearing Loss and Directions for Therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Usher syndrome (USH) is an autosomal recessive (AR) disorder that permanently and severely affects the senses of hearing, vision, and balance."
    explanation: Supports counseling for the autosomal recessive recurrence risk.
- name: Investigational Gene-Directed Therapy
  description: >-
    No approved treatment exists for the retinal degeneration. Gene replacement,
    gene editing, antisense oligonucleotides and small molecules are in
    development across the Usher entities.

    The Müller glial localization of clarin-1 has a direct consequence for this
    entity that does not apply to types 1 and 2: a retinal gene therapy would need
    to reach Müller glia, not photoreceptors. The zebrafish rescue experiment cited
    on the Müller glial node is the evidence for that targeting requirement.
  treatment_term:
    preferred_term: Gene Therapy
    term:
      id: NCIT:C15238
      label: Gene Therapy
  notes: >-
    The binding is narrower than the row. NCIT:C15238 Gene Therapy covers gene
    replacement and editing but not the antisense oligonucleotides and small
    molecules the description also names, and NCIT has no clinical-action term
    spanning all four. Bound to the narrower accurate term rather than to a vague
    broader one; if the small-molecule or ASO strand becomes a specific named
    therapy for this entity it should be split into its own treatment row with its
    own binding.
  evidence:
  - reference: PMID:32995707
    reference_title: "Usher syndrome: clinical features, molecular genetics and advancing therapeutics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "While there is currently no available approved treatment for the RP, various therapeutic strategies are in development or in clinical trials for Usher syndrome, including gene replacement, gene editing, antisense oligonucleotides and small molecule drugs."
    explanation: Documents that no approved retinal treatment exists and names the strategies in development.
animal_models:
- name: Clrn1 knockout mouse
  species: Mouse (Mus musculus)
  genotype: Clrn1 knockout
  category: Constitutive knockout
  description: >-
    Reproduces the cochlear arm of type 3 and explicitly fails to reproduce the
    retinal arm. Both results are informative, and the negative one is the more
    useful of the two: it is the observation that redirected the field toward
    Müller glia.
  modeled_mechanisms:
  - target: Cochlear Hair Bundle Disorganization
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: TISSUE
    description: >-
      Progressive cochlear sensory hair cell loss with deterioration of the organ
      of Corti by four months.
    evidence:
    - reference: PMID:19680541
      reference_title: CLRN1 is nonessential in the mouse retina but is required for cochlear hair cell development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Clrn1 KO mice do not develop a retinal degeneration phenotype, but exhibit progressive loss of sensory hair cells in the cochlea and deterioration of the organ of Corti by 4 months."
      explanation: Establishes that the model reproduces the cochlear mechanism.
  - target: Photoreceptor Degeneration
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    model_scale: TISSUE
    limitations: >-
      Clrn1-null mice develop no retinal degeneration, so the model cannot report
      on the retinal arm of this entity and a negative retinal result in it is
      uninformative about human disease. Mouse Clrn1 mRNA is also developmentally
      downregulated in the adult retina, detectable only by sensitive assays,
      which compounds the problem.
    description: >-
      The model does not reproduce the human retinal phenotype.
    evidence:
    - reference: PMID:19680541
      reference_title: CLRN1 is nonessential in the mouse retina but is required for cochlear hair cell development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Clrn1 KO mice do not develop a retinal degeneration phenotype, but exhibit progressive loss of sensory hair cells in the cochlea and deterioration of the organ of Corti by 4 months."
      explanation: Directly states the absent retinal phenotype.
  evidence:
  - reference: PMID:19680541
    reference_title: CLRN1 is nonessential in the mouse retina but is required for cochlear hair cell development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In contrast to mouse KO models of USH1 and USH2, our data indicate that Clrn1 expression in the retina is restricted to the Müller glia."
    explanation: >-
      The same study that reports the absent retinal phenotype also reports the
      cell-type restriction that explains it.
- name: clrn1 mutant zebrafish with cell-specific rescue
  species: Zebrafish (Danio rerio)
  genotype: CRISPR/Cas9 deletion of zebrafish clrn1, with Müller-glia-specific or photoreceptor-specific clrn1 re-expression
  category: Knockout with cell-type-specific rescue
  description: >-
    The model that establishes the causal direction of the retinal mechanism. Its
    value is the contrast between the two rescue arms rather than either arm alone.
  modeled_mechanisms:
  - target: Müller Glial Support Failure
    relationship: RESCUES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Müller glial re-expression prevents light-induced photoreceptor death;
      rod- or cone-specific re-expression does not.
    limitations: >-
      Larval zebrafish under high-intensity light stress is an acute challenge
      paradigm, not the decades-long degeneration of human type 3, and the rescue
      is a re-expression experiment rather than a therapeutic delivery.
    readouts:
    - name: Light-induced retinal cell death
      target: Müller Glial Support Failure
      direction: RESTORED
      interpretation: >-
        Cell death returns toward baseline with glial re-expression, establishing
        the glial compartment as where clarin-1 acts.
      evidence:
      - reference: PMID:40067805
        reference_title: The USH3A causative gene clarin1 functions in Müller glia to maintain retinal photoreceptors.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Müller glia re-expression of clrn1 prevented the elevated cell death observed in larval clrn1 mutant zebrafish exposed to high-intensity light."
        explanation: Reports the measured rescue.
    evidence:
    - reference: PMID:40067805
      reference_title: The USH3A causative gene clarin1 functions in Müller glia to maintain retinal photoreceptors.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Notably, the degree of phenotypic rescue correlated with the level of Clrn1 re-expression."
      explanation: >-
        The dose-response relationship strengthens the attribution of the rescue to
        clarin-1 re-expression rather than to the manipulation.
  evidence:
  - reference: PMID:40067805
    reference_title: The USH3A causative gene clarin1 functions in Müller glia to maintain retinal photoreceptors.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "To assess cell-specific contributions to USH3A pathology, we specifically re-expressed clrn1 in either Müller glia or photoreceptor cells."
    explanation: Describes the cell-specific rescue design that makes this model informative.
review_notes: >-
  Created 2026-09-24 by splitting kb/disorders/Usher_Syndrome.yaml into four
  mechanism entities plus a grouping, per the decision recorded on issue #10822.

  This is the entity the lumped entry served worst. Clarin-1 is in neither Usher
  complex, so the shared root node named an assembly it does not belong to; and
  it is expressed in Müller glia rather than photoreceptors, so the shared
  "Photoreceptor Connecting Cilium Dysfunction" node named a compartment it is
  not in. Both nodes have been replaced rather than renamed.

  The root node names the loss of a protein rather than the disruption of a named
  complex, which is deliberate: clarin-1 has no assigned biochemical activity and
  belongs to no Usher assembly, and a node asserting otherwise would be the same
  defect the split was made to fix.

  The retinal causal direction rests on a cell-specific rescue experiment in
  zebrafish, with the human cell-type attribution from RNAscope and single-cell
  RNA-seq on adult human retina. The published PLoS Genetics version is cited
  rather than the bioRxiv preprint.

  The Clrn1 knockout mouse carries a FAILS_TO_RECAPITULATE link for the retinal
  arm. That is a substantive negative claim and it is the observation that
  redirected the field to Müller glia, so it is recorded structurally rather than
  left as prose.

  ClinGen's CLRN1-type 3 Definitive assertion is not cited as a structured
  reference because it predates the CGGV identifier scheme and its CGGCIEX
  identifier is not in the repository's ClinGen index; this was checked rather
  than assumed, and the gene entry says so. The HARS1 Refuted assertion does have
  a CGGV identifier and is cited.

  No GeneReviews chapter exists for Usher syndrome type 3 or CLRN1. This was
  checked rather than assumed: the committed Bookshelf index
  (cache/bookshelf/genereviews.csv, snapshot 2026-09-10, 958 chapters) contains
  exactly two Usher chapters - PMID:20301442 "Usher Syndrome Type I." (NBK1265)
  and PMID:20301515 "Usher Syndrome Type II." (NBK1341) - and neither covers type
  3. `just check-genereviews kb/disorders/Usher_Syndrome_Type_3.yaml` reports
  NO_CHAPTER for the same reason. The mandatory GeneReviews phenotype baseline
  therefore does not apply to this entry, and neither existing chapter is cited,
  since quoting a type I or type II chapter for a type-3 claim would be evidence
  from the wrong disease. This follows the convention Usher_Syndrome_Type_4
  already records for the same situation.

  Not curated here: the CLRN1 isolated-retinopathy branch (retinitis pigmentosa
  61). Like the USH2A branch on the type-2 entry, it is defined by ABSENT hearing
  loss and cannot be stated until issue #10190 lands. No per-entity prevalence is
  asserted: the 4-17 per 100,000 figure the lumped entry carried is for Usher
  syndrome as a whole, and the `Grouping` class has no prevalence slot, so that
  figure is carried in the grouping's prose.

📚

References & Deep Research