Autosomal Dominant Nonsyndromic Hearing Loss 2B

Mendelian MONDO:0012976 Pathograph 5 Show in embeddings browser Autosomal Dominant Nonsyndromic Hearing Loss Hereditary Hearing Loss

DFNA2B is the proposition that heterozygous GJB3 variants cause dominant, progressive, high-frequency sensorineural hearing loss. It was named in 1998 from two Chinese families, and the ClinGen Hearing Loss Gene Curation Expert Panel has classified it Disputed since 2018 - the strongest wording the framework offers short of Refuted, and the panel used the phrase "convincing evidence disputing the association". Three things weigh against it and they are of different kinds. Many of the reported variants are common in population databases or have no evidence of pathogenicity; only three scored in the ClinGen review. The most-screened allele, c.538C>T p.Arg180*, was found in 0.40% of 5,700 Chinese hearing-loss patients and 0.24% of 4,600 normal-hearing controls, a difference that is not significant, and all 23 carriers were sporadic with no family history; a second Chinese series of 2,178 subjects found the same allele at a frequency above the gnomAD East Asian average and concluded it may not be disease-causing. And the Cx31-null mouse has no morphological or functional defect of the inner ear at all. What is real is the protein biology. Connexin 31 is expressed in the inner ear - by RT-PCR in rat, and at high levels in adult mouse inner hair cells and spiral ganglion neurons - and hearing-loss-associated Cx31 mutants demonstrably fail to traffic, are retained in the ER, induce ER stress and cannot form functional channels. That is a genuine molecular lesion. What is missing is any demonstration that it causes deafness in a person or an animal. GJB3 does cause a disease: erythrokeratodermia variabilis, which the same expert panel rates Definitive and which dismech curates separately. This entry is that entity's disputed auditory sibling, and it is curated as contested rather than established.

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1
Inheritance
4
Pathophys.
2
Phenotypes
1
Hypotheses
2
Gaps
5
Pathograph
1
Genes
3
Differentials
1
Models
14
References
1
Deep Research
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Inheritance

1
Autosomal dominant HP:0000006
Dominant transmission is what DFNA2B claims and it is also where the claim is weakest. The founding families segregated heterozygous variants with high-frequency hearing loss. But in the largest subsequent series every one of the 23 carriers of the most-screened allele was a sporadic case with no family history of deafness - the opposite of what dominant inheritance predicts, and in a sample far larger than the founding families.
Autosomal dominant inheritance
Show evidence (2 references)
PMID:9843210 SUPPORT Human Clinical
"Mutation analysis revealed that a missense mutation and a nonsense mutation of GJB3 were associated with high-frequency hearing loss in two families."
The family-based observation underlying the dominant claim.
PMID:29106878 REFUTE Human Clinical
"All 23 patients were sporadic cases and had no family history of deafness."
Directly contradicts dominant transmission for the allele that has been screened most widely.
◈

Mechanistic Hypotheses

1
Trafficking-defective connexin 31 disrupts cochlear gap-junction coupling and causes dominant high-frequency hearing loss
cx31_gap_junction_deafness ALTERNATIVE
Evidence balance 1 support 1 refute
The proposed mechanism, and the reason it is a hypothesis group rather than this entry's canonical model. Its molecular half is solid. Connexin 31 is a gap junction subunit expressed in the inner ear, at high levels in adult inner hair cells and spiral ganglion neurons. Two hearing-loss-associated mutants are retained in the ER and in Golgi-like structures, fail to transfer dye between cells, and induce the ER chaperone BiP. Two further variants fail to couple cells even when co-expressed with wild-type Cx31, which is the shape of a dominant-negative effect and is what a dominant disease would need. Its organismal half does not exist. No animal carrying a GJB3 variant has been shown to hear abnormally; the Cx31-null mouse hears normally and has a structurally normal inner ear. No human cochlear pathology has ever been examined. The step from "these channels do not work in transfected cells" to "this person is deaf" has not been made in any system. Every causal edge below opts into this group. None of them is an established step.
Pathograph links
Heterozygous GJB3 Variant -> Connexin 31 Trafficking Failure and ER Retention DIRECT Two hearing-loss-associated variants have been shown to do this directly in transfected cells.
Connexin 31 Trafficking Failure and ER Retention -> Loss of Cochlear Gap-Junction Coupling DIRECT A channel subunit that never reaches the membrane cannot contribute to intercellular coupling.
Loss of Cochlear Gap-Junction Coupling -> Progressive High-Frequency Sensorineural Hearing Loss INDIRECT UNKNOWN INTERMEDIATES The step with no evidence in any organism. The one animal in which it was tested hears normally.
Show evidence (2 references)
PMID:21204020 SUPPORT In Vitro
"Together, the HI-associated C×31 mutants are impaired in trafficking, promote ER stress, and hence lose the ability to assemble functional gap junctions."
The molecular half of the hypothesis, measured in transfected cells.
PMID:11237463 REFUTE Model Organism
"No morphological or functional defects of skin or inner ear were observed in surviving adult Gjb3(-/-) mice."
The organismal test, with a negative result in the ear and, notably, in the skin as well - so the mouse is uninformative about the established GJB3 disease too.
?

Discussions and Knowledge Gaps

2
Does a heterozygous trafficking-defective GJB3 allele cause hearing loss in any organism?
KNOWLEDGE GAP OPEN gap_gjb3_dominant_negative_untested_in_vivo
Attached to
genetic#GJB3 mechanistic_hypotheses#cx31_gap_junction_deafness
The evidence base has a specific shape: everything below the tissue level supports the hypothesis and nothing at the tissue level tests it in the right genotype. Cx31 mutants are retained in the ER, induce BiP, and fail to transfer dye. Two variants fail to couple even alongside wild-type Cx31, which is the dominant-negative behaviour a dominant disease requires. But the only animal ever made is a homozygous null, and it is normal - and a null cannot test a dominant negative, because there is no wild-type protein left for the mutant to poison. So the decisive experiment has not been done. A mouse heterozygous for a human DFNA2B allele - R180X or E183K knocked in - is the direct test, and it is a standard experiment that nobody appears to have run in the twenty-eight years since the association was proposed. Until it is, the human case-control data are the best evidence available, and they are negative.
Proposed experiments
Auditory phenotyping of mice heterozygous for a human DFNA2B GJB3 allele
gjb3_knockin_heterozygote_auditory_phenotype
Knock the human R180X and E183K alleles into the mouse Gjb3 locus, phenotype heterozygotes with auditory brainstem responses and distortion-product otoacoustic emissions across the frequency range and across age, and examine cochlear gap junction plaques for Cx26 and Cx30 as well as Cx31 to test whether the mutant protein disrupts the other connexins.
Would support
mechanistic_hypotheses#cx31_gap_junction_deafness
Supporting outcome
  • Heterozygous knock-in mice develop progressive high-frequency hearing loss where nulls do not, which would establish a dominant-negative mechanism, explain why the null mouse is normal, and warrant revisiting the Disputed classification.
Refuting outcome
  • Heterozygotes hear normally, which together with the case-control data would leave DFNA2B without support in either humans or animals and would make retirement of the entity the right curation outcome.
How much weight should the normal hearing of the Cx31-null mouse carry, given that the same mouse is also normal in skin, where GJB3 causes an established human disease?
HUMAN MODEL MISMATCH OPEN mismatch_gjb3_null_mouse_normal_in_skin_too
Attached to
animal_models#Cx31-deficient (Gjb3 lacZ knock-in) mouse
This is the strongest argument available to the pro-DFNA2B side and it should be recorded as such rather than buried. The single sentence that reports normal hearing in the Gjb3-null mouse reports normal skin in the same breath - and GJB3-erythrokeratodermia variabilis is rated Definitive by the same expert panel that disputes the hearing loss. An animal that fails to model a Definitive human disease is a weak instrument for ruling out a disputed one. There is a coherent reading in which both are explained at once. Human EKV is dominant and the alleles behave as dominant negatives; the mouse is a null; nulls do not model dominant negatives; and connexin redundancy - the authors' own explanation - covers the rest. Under that reading the mouse says nothing about either disease and the DFNA2B question turns entirely on the human data, which is where the case-control study becomes decisive. The alternative reading is that mouse and human connexin biology simply differ enough in both organs that neither negative transfers. Nothing published distinguishes these.
Proposed experiments
Reassessment of the Gjb3-null mouse against the established skin phenotype
gjb3_null_mouse_skin_and_ear_reassessment
Re-phenotype Gjb3-null and heterozygous mice with modern dermatological and auditory assays alongside a Gjb3 EKV-allele knock-in, and determine whether the knock-in reproduces the human skin phenotype. Whether the model can reproduce the Definitive disease sets the ceiling on what its silence about the disputed one is worth.
Would support
animal_models#Cx31-deficient (Gjb3 lacZ knock-in) mouse
Supporting outcome
  • A knock-in reproduces the human skin phenotype while heterozygous ears stay normal, which would show the model is capable of reporting a GJB3 disease and would make its auditory silence substantive evidence against DFNA2B.
Refuting outcome
  • No mouse genotype reproduces the human skin phenotype either, which would establish that mouse Gjb3 does not report human GJB3 disease at all and would remove the strongest animal argument currently cited against DFNA2B.
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Pathophysiology

4
Heterozygous GJB3 Variant
GJB3 encodes connexin 31 and is at 1p34.3; the founding report placed it in the broader 1p33-p35 interval, which is the mapping quoted in the evidence below. The founding report described a missense and a nonsense variant in two families with high-frequency hearing loss; the nonsense allele, c.538C>T p.Arg180*, became the one routinely screened in Chinese deafness panels and is the one that has since failed a case-control test. The variants are heterozygous, which is what makes the claimed inheritance dominant and which sets the mechanistic requirement: a single altered allele has to produce a phenotype, so either haploinsufficiency or a dominant-negative effect on the wild-type protein is needed. Haploinsufficiency is hard to sustain given that homozygous null mice hear normally, so the dominant-negative reading is the live one - and the coupling experiments below were designed to test exactly that.
Trafficking-defective connexin 31 disrupts cochlear gap-junction coupling and causes dominant high-frequency hearing loss
Genetic context GJB3 hgnc:4285 HUGO Gene Nomenclature Committee (hgnc) Relation: this genetic context concerns this gene This genetic context concerns GJB3 (hgnc:4285). hgnc:4285 is a gene from the HUGO Gene Nomenclature Committee. variant_origin: GERMLINE zygosity: HETEROZYGOUS
Heterozygous in the reported families. functional_impact_category is omitted deliberately: the trafficking data show the mutant protein is made and mislocalised rather than absent, and whether that constitutes loss of function or a dominant negative is the open question rather than something the entry can assert.
Downstream
Connexin 31 Trafficking Failure and ER Retention Two hearing-loss-associated variants have been shown to do this directly in transfected cells. Trafficking-defective connexin 31 disrupts cochlear gap-junction coupling and causes dominant high-frequency hearing loss
Show evidence (3 references)
PMID:9843210 SUPPORT Human Clinical
"Mutation analysis revealed that a missense mutation and a nonsense mutation of GJB3 were associated with high-frequency hearing loss in two families."
The founding association, on two families.
PMID:29106878 REFUTE Human Clinical
"Our results showed that the GJB3 c.538C>T variant has a very low incidence in the Chinese population, and there was no clear evidence to support a role of the GJB3 c.538C>T variant in the autosomal dominant form of non-syndromic deafness."
A direct case-control test of the most-screened allele, which found nothing. This is the strongest single human argument against DFNA2B.
PMID:29106878 REFUTE Human Clinical
"All 23 patients were sporadic cases and had no family history of deafness."
Absence of family history in every carrier, which is incompatible with the allele acting as a dominant cause.
Connexin 31 Trafficking Failure and ER Retention
Wild-type Cx31 forms functional gap junctions at cell-cell contacts in transfected cells. Two hearing-impairment-associated mutants, R180X and E183K, do not: they sit in the endoplasmic reticulum and in Golgi-like punctate structures respectively, fail to transfer lucifer yellow between cells, and upregulate and bind the ER chaperone BiP, indicating ER stress. This is the same protein-level lesion that the dismech Erythrokeratodermia Variabilis entry describes for the skin disease - Cx31 that does not reach the membrane and so cannot take part in gap junction formation. The two entries agree about what happens to the protein. They differ in whether the resulting tissue phenotype is established, and only the skin one is.
Trafficking-defective connexin 31 disrupts cochlear gap-junction coupling and causes dominant high-frequency hearing loss
gap junction assembly by connexin 31 GO:0016264 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased gap junction assembly by connexin 31, annotated with gap junction assembly (GO:0016264). GO:0016264 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Loss of Cochlear Gap-Junction Coupling A channel subunit that never reaches the membrane cannot contribute to intercellular coupling. Trafficking-defective connexin 31 disrupts cochlear gap-junction coupling and causes dominant high-frequency hearing loss
Show evidence (2 references)
PMID:21204020 SUPPORT In Vitro
"In contrast, two HI-associated C×31 mutants, C×31R180X and C×31E183K resided primarily in the ER and Golgi-like intracellular punctate structures, respectively, and failed to mediate lucifer yellow transfer."
The retention and dye-transfer failure, in transfected cells.
PMID:21204020 SUPPORT In Vitro
"In transfected cells, wild type C×31 protein (C×31wt) forms functional gap junction at cell-cell-contacts."
The wild-type control that makes the mutant result interpretable.
Loss of Cochlear Gap-Junction Coupling
Connexin 31 is one of three connexins named as core components of inner ear gap junctions, alongside Cx26 (GJB2) and Cx30 (GJB6). Its expression in the ear is real: RT-PCR detected Gjb3 in rat inner ear tissue in the founding study, and it is developmentally regulated in mouse with high levels in adult inner hair cells and spiral ganglion neurons. The dominant-negative question is decided at this node, and it has been tested. Cx31 p.Val27Met and p.Val84Ile each failed to function when expressed as heterozygotes alongside wild-type Cx31 - which is what a dominant allele needs to do, and which is why the hypothesis remains alive despite the mouse. What has never been shown is the effect of any of this on a cochlea.
Trafficking-defective connexin 31 disrupts cochlear gap-junction coupling and causes dominant high-frequency hearing loss
cochlear inner hair cell CL:0000589 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cochlear inner hair cell (CL:0000589). CL:0000589 is a cell type from the Cell Ontology. spiral ganglion neuron CL:0011113 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves spiral ganglion neuron (CL:0011113). CL:0011113 is a cell type from the Cell Ontology.
connexin 31 gap junction channel activity GO:0005243 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased connexin 31 gap junction channel activity, annotated with gap junction channel activity (GO:0005243). GO:0005243 is a molecular function from the Gene Ontology. ↓ DECREASED
Animal models
Cx31-deficient (Gjb3 lacZ knock-in) mouse Mouse fails to recapitulate Complete absence of Cx31 produces no inner ear defect, structural or functional, in the adult mouse. The hypothesis that cochlear Cx31 loss causes deafness predicts otherwise.
Downstream
Progressive High-Frequency Sensorineural Hearing Loss The step with no evidence in any organism. The one animal in which it was tested hears normally. Trafficking-defective connexin 31 disrupts cochlear gap-junction coupling and causes dominant high-frequency hearing loss
Show evidence (4 references)
PMID:21204020 SUPPORT Model Organism
"we show that expression of C×31 in the mouse inner ear is developmentally regulated with a high level in adult inner hair cells and spiral ganglion neurons that are critical for the hearing process."
Localises the protein to auditory cell types. Graded MODEL_ORGANISM because it is mouse inner ear tissue, in the same paper whose transfected-cell work is graded IN_VITRO.
PMID:22617145 SUPPORT In Vitro
"The results of biochemical and ionic coupling tests showed that both the Cx31-p.V27M and Cx31-p.V84I variants did not function normally when each was expressed as a heterozygote with the wild-type Cx31."
The dominant-negative test, performed under heterozygous conditions, which is the configuration a dominant disease requires.
PMID:9843210 SUPPORT INDIRECT Model Organism
"Moreover, expression of Gjb3 was identified in rat inner ear tissue by RT-PCR."
Expression in the inner ear, graded INDIRECT because presence of a transcript is consistent with a role and does not establish one.
+ 1 more reference
Progressive High-Frequency Sensorineural Hearing Loss
The claimed clinical endpoint: bilateral high-frequency hearing impairment, described in the founding report and repeated in reviews as postlingual and progressive. It is worth being precise about what the founding paper actually says, because the strength of the claim has drifted upward in secondary sources. Its own conclusion is that mutations in GJB3 "may be responsible" for bilateral high-frequency hearing impairment - hedged in 1998, and the hedge has not been retired since.
sensory perception of sound GO:0007605 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased sensory perception of sound (GO:0007605). GO:0007605 is a biological process from the Gene Ontology. ↓ DECREASED
Show evidence (2 references)
PMID:9843210 SUPPORT Human Clinical
"These findings suggest that mutations in GJB3 may be responsible for bilateral high-frequency hearing impairment."
The founding claim in the founding paper's own hedged wording. Graded PARTIAL because "may be responsible" is what the source says and is what the evidence has supported ever since.
CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z REFUTE Other
"Association is seen in at least 5 probands in 3 publications"
The total human evidence base for this phenotype, twenty years after the founding report: five probands.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Autosomal Dominant Nonsyndromic Hearing Loss 2B Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

2
High-Frequency Sensorineural Hearing Loss FREQUENT Otologic HP:0005101 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is High-frequency hearing impairment (HP:0005101). HP:0005101 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:9843210 SUPPORT Human Clinical
"Mutation analysis revealed that a missense mutation and a nonsense mutation of GJB3 were associated with high-frequency hearing loss in two families."
The audiometric pattern in the two founding families.
PMID:29106878 REFUTE Human Clinical
"Most patients had moderate to profound hearing loss."
The 23 carriers in the case-control series did not have the high-frequency pattern the founding families had, which weakens the genotype-phenotype correlation this phenotype asserts.
Bilateral Involvement FREQUENT Otologic HP:0008619 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bilateral sensorineural hearing impairment (HP:0008619). HP:0008619 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9843210 SUPPORT Human Clinical
"These findings suggest that mutations in GJB3 may be responsible for bilateral high-frequency hearing impairment."
States bilateral involvement, in the source's own hedged framing.
🧬

Genetic Associations

1
GJB3
Gene: GJB3 hgnc:4285 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is GJB3 (hgnc:4285). hgnc:4285 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: DISPUTED
Show evidence (5 references)
CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z REFUTE Other
"In summary, there is convincing evidence disputing the association between GJB3 and autosomal dominant nonsyndromic hearing loss."
The classification this relationship_type encodes.
CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z SUPPORT Other
"Of note, this gene has also been implicated in Erythrokeratodermia variabilis."
The panel's own separation of the two GJB3 relationships, which is why the Disputed verdict is about this disease and not about the gene.
PMID:29926981 REFUTE Human Clinical
"Putatively causative GJB3 variant underlied 1% (1/100) in this cohort."
A deliberate test of whether screening GJB3 adds diagnostic yield, which found it adds almost none.
+ 2 more references
🗃️

External Assertions

2
ClinGen GJB3-nonsyndromic hearing loss gene-disease validity assertion
ClinGen gene disease validity CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
The ClinGen Hearing Loss Gene Curation Expert Panel classifies the autosomal dominant GJB3-nonsyndromic hearing loss relationship as Disputed, approved 2018-02-27. Its evidence summary is unusually explicit about why: the association rested on case-level data only, many reported variants are present at high frequency in population databases or have no evidence for pathogenicity, and only three variants had enough evidence to score.
The same expert panel classifies GJB3-erythrokeratodermia variabilis as Definitive. One gene, two curations by the same group, opposite verdicts - which is the cleanest possible demonstration that a gene's disease relationships have to be assessed one at a time. The assertion's evidence summary cites PMID 12759707 among the publications in which the association was seen. Looked up at PubMed, that identifier is a 2003 Spanish-language editorial on smoking prevention in Anales del Sistema Sanitario de Navarra, so it is evidently a transcription error in the ClinGen record rather than a hearing-loss report. It is cited nowhere in this entry, and no attempt was made to guess which publication was intended.
Show evidence (6 references)
CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z REFUTE Other
"GJB3 | HGNC:4285 | nonsyndromic genetic hearing loss | MONDO:0019497 | AD | Disputed"
The expert-panel classification row, with the dominant mode of inheritance DFNA2B claims.
CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z REFUTE Other
"In summary, there is convincing evidence disputing the association between GJB3 and autosomal dominant nonsyndromic hearing loss."
The panel's conclusion sentence. Read together with the sentence that follows it and with the framework's published definition, quoted below: Disputed covers insufficient as well as contradictory evidence, and the panel explicitly declines to rule the reported evidence out.
CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z REFUTE Other
"Multiple missense and nonsense variants have been reported in humans, however many of these variants are present in high frequency in population databases and/or have no evidence for pathogenicity."
The specific reason the reported variant count overstates the evidence.
+ 3 more references
ClinGen GJB3-erythrokeratodermia variabilis gene-disease validity assertion
ClinGen gene disease validity CGGV:assertion_1d48c959-31d8-44e2-985c-c48921e8f08a-2023-06-01T160000.000Z
Recorded here for contrast, not because it is this disease. The same Hearing Loss Gene Curation Expert Panel rates GJB3's relationship with erythrokeratodermia variabilis Definitive, on a 2023 SOP v11 review - five years newer than the Disputed hearing-loss curation. dismech curates that disease separately as Erythrokeratodermia Variabilis.
Show evidence (1 reference)
CGGV:assertion_1d48c959-31d8-44e2-985c-c48921e8f08a-2023-06-01T160000.000Z SUPPORT Other
"GJB3 | HGNC:4285 | erythrokeratodermia variabilis | MONDO:0017851 | AD | Definitive"
Establishes the established GJB3 disease, so a reader can see at a glance that the Disputed verdict above is specific to hearing loss and is not a judgement about the gene.
🔬

Diagnosis

1
Interpretation of a GJB3 variant found on a deafness panel
GJB3 is on hereditary hearing loss panels, particularly in China where it has been part of routine deafness screening for two decades, so heterozygous GJB3 variants will continue to be reported in deaf patients regardless of the Disputed classification. What follows is a reporting question rather than a testing one. Four things should be established before a GJB3 variant is offered as an explanation. Whether KCNQ4 has been sequenced, because DFNA2A sits in the same mapped interval, has the same audiogram, and is an established relationship where this one is not. Whether the patient also carries a GJB2 or SLC26A4 variant, because nearly half of the GJB3 carriers in the largest series did. Whether there is a family history consistent with dominant transmission, because none of those 23 carriers had one. And whether the audiogram is high-frequency, because the carriers in that series mostly had moderate to profound loss rather than the founding families' pattern.
Show evidence (3 references)
PMID:29106878 SUPPORT Human Clinical
"Of the 5700 patients, 23 (0.40%) carried a GJB3 c.538C>T heterozygous variant; of these, 11 patients had other gene (GJB2/SLC26A4) mutations simultaneously."
The co-occurrence rate that makes checking for a competing variant the first step.
PMID:29926981 SUPPORT Human Clinical
"GJB3/GJB6 variants account for a low proportion in autosomal recessive GJB2 mutation carriers in our cohort."
A study that asked directly whether GJB3 screening is worth doing and found the yield low.
PMID:20301388 SUPPORT Human Clinical
"The diagnosis of DFNA2 nonsyndromic hearing loss is established in an individual with a characteristic audioprofile, a family history consistent with autosomal dominant inheritance, and identification of a heterozygous pathogenic variant in KCNQ4."
The established alternative at the same locus, and the first thing to exclude before a GJB3 variant is reported as causal.
📊

Prevalence

1
Chinese hearing-loss cohorts
Carrier Frequency Unknown
The number usually quoted for DFNA2B is a variant carrier rate in a deaf cohort, and it does not survive comparison with controls. Among 5,700 Chinese hearing-loss patients, 0.40% carried the heterozygous c.538C>T allele; among 4,600 normal-hearing individuals, 0.24% did, and the difference was not statistically significant. Eleven of the 23 carriers also had GJB2 or SLC26A4 mutations, and all 23 were sporadic with no family history of deafness - which is not what a dominant disease looks like. Other Chinese cohorts point the same way: GJB3 mutations were not common in a 284-patient survey, and a putatively causative GJB3 variant accounted for 1 of 100 GJB2-heterozygous patients in another. No prevalence for DFNA2B as a disease can be stated, and the prevalence_class is UNKNOWN rather than a numeric band for that reason.
Show evidence (4 references)
PMID:29106878 REFUTE Human Clinical
"Of the 5700 patients, 23 (0.40%) carried a GJB3 c.538C>T heterozygous variant; of these, 11 patients had other gene (GJB2/SLC26A4) mutations simultaneously."
The carrier rate in cases, and the confounding: nearly half of the carriers had a competing explanation.
PMID:29106878 REFUTE Human Clinical
"There was no statistical difference in incidence between the two groups."
The case-control comparison that makes the carrier rate uninformative about causation.
PMID:19744334 REFUTE Human Clinical
"Mutations in GJB3, GJB6, and mtDNA tRNAser(UCN) were not common in this Chinese cohort."
An independent cohort reaching the same conclusion about how rarely GJB3 explains hearing loss.
+ 1 more reference
🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Autosomal Dominant Nonsyndromic Hearing Loss 2B:

🐁

Animal Models

1
Cx31-deficient (Gjb3 lacZ knock-in) mouse
The only Gjb3 mouse, and its hearing is normal. Homozygotes are largely lost between embryonic days 10.5 and 13.5 from placental failure - the labyrinth and spongiotrophoblast are severely reduced at E9.5 - but the placenta recovers as connexin 43 comes up, and the survivors reach adulthood with no morphological or functional defect of skin or inner ear. The authors' own explanation is compensation by other connexins in the embryo proper and the adult, which is a live possibility rather than a dismissal: the cochlea expresses Cx26 and Cx30 alongside Cx31, so redundancy there is entirely plausible. Two further caveats matter for reading this animal against DFNA2B. It is a null, and DFNA2B is claimed to be dominant, so a dominant-negative human allele is not modelled by removing the gene. And the mouse is also normal in skin, where GJB3 causes a Definitive human disease - so this animal fails to model the established GJB3 phenotype too, which is a reason to weight its auditory negative carefully rather than treat it as conclusive.
Species
Mouse
Genotype
Gjb3(-/-), targeted replacement of Gjb3 by a lacZ reporter, homozygous
Publication
PMID:11237463
Pathograph links
Loss of Cochlear Gap-Junction Coupling fails to recapitulate fidelity: low Complete absence of Cx31 produces no inner ear defect, structural or functional, in the adult mouse. The hypothesis that cochlear Cx31 loss causes deafness predicts otherwise.
Limitations: Three limitations, and together they are why fidelity is LOW rather than higher. The model is a homozygous null and the human disease is claimed to be dominant, so a dominant-negative allele acting on wild-type Cx31 is not tested here. The authors attribute the normal phenotype to compensation by other connexins, and the cochlea expresses Cx26 and Cx30, so compensation is a specific and untested alternative to "Cx31 does not matter for hearing". Most tellingly, the same mouse is normal in skin, where the human GJB3 relationship is rated Definitive - so this animal demonstrably fails to model an established GJB3 disease, and its auditory negative cannot carry more weight than its dermatological one.
Readouts
Inner ear morphology and auditory function in adult Gjb3-null mice
Direction: UNCHANGED
Interpretation: No structural or functional inner ear abnormality in the complete absence of connexin 31. A deliberate negative result in the only animal that has tested the question.
Show evidence (1 reference)
PMID:11237463 REFUTE Model Organism
"No morphological or functional defects of skin or inner ear were observed in surviving adult Gjb3(-/-) mice."
The measurement behind this readout. It reports skin and inner ear together, which is also the sentence that establishes the model's failure in the established GJB3 disease.
Placental labyrinth and spongiotrophoblast size at E9.5
Direction: DECREASED
Interpretation: The one phenotype the null mouse does have, recorded because it establishes that the targeting worked and the animal is a genuine null - so the auditory negative is not an artefact of a failed knockout.
Show evidence (1 reference)
PMID:11237463 SUPPORT Model Organism
"Placentas of Gjb3(-/-) embryos at ED 9.5 were smaller than controls as a result of severely reduced labyrinth and spongiotrophoblast size."
Demonstrates a real loss-of-function phenotype elsewhere, which is what makes the normal ear meaningful.
Show evidence (1 reference)
PMID:11237463 REFUTE Model Organism
"Mutations in the human GJB3 gene that codes for Connexin31 (Cx31), a protein subunit of gap junction channels, have recently been reported to cause deafness and the skin disorder erythrokeratodermia variabilis."
Establishes that this mouse was built to test the human deafness claim, which is what makes its negative result a failure to recapitulate rather than an unrelated observation.
{ }

Source YAML

click to show 
name: Autosomal Dominant Nonsyndromic Hearing Loss 2B
creation_date: "2026-08-28T22:00:00Z"
category: Mendelian
disease_term:
  preferred_term: autosomal dominant nonsyndromic hearing loss 2B
  term:
    id: MONDO:0012976
    label: autosomal dominant nonsyndromic hearing loss 2B
synonyms:
- DFNA2B
- deafness, autosomal dominant 2B
- GJB3-related autosomal dominant nonsyndromic hearing loss
- autosomal dominant nonsyndromic deafness 2B
description: >-
  DFNA2B is the proposition that heterozygous GJB3 variants cause dominant, progressive,
  high-frequency sensorineural hearing loss. It was named in 1998 from two Chinese families,
  and the ClinGen Hearing Loss Gene Curation Expert Panel has classified it Disputed since
  2018 - the strongest wording the framework offers short of Refuted, and the panel used the
  phrase "convincing evidence disputing the association".

  Three things weigh against it and they are of different kinds. Many of the reported
  variants are common in population databases or have no evidence of pathogenicity; only
  three scored in the ClinGen review. The most-screened allele, c.538C>T p.Arg180*, was found
  in 0.40% of 5,700 Chinese hearing-loss patients and 0.24% of 4,600 normal-hearing controls,
  a difference that is not significant, and all 23 carriers were sporadic with no family
  history; a second Chinese series of 2,178 subjects found the same allele at a frequency
  above the gnomAD East Asian average and concluded it may not be disease-causing. And the
  Cx31-null mouse has no morphological or functional defect of the inner ear at all.

  What is real is the protein biology. Connexin 31 is expressed in the inner ear - by RT-PCR
  in rat, and at high levels in adult mouse inner hair cells and spiral ganglion neurons -
  and hearing-loss-associated Cx31 mutants demonstrably fail to traffic, are retained in the
  ER, induce ER stress and cannot form functional channels. That is a genuine molecular
  lesion. What is missing is any demonstration that it causes deafness in a person or an
  animal.

  GJB3 does cause a disease: erythrokeratodermia variabilis, which the same expert panel
  rates Definitive and which dismech curates separately. This entry is that entity's
  disputed auditory sibling, and it is curated as contested rather than established.

parents:
- Autosomal Dominant Nonsyndromic Hearing Loss
- Hereditary Hearing Loss

external_assertions:
- name: ClinGen GJB3-nonsyndromic hearing loss gene-disease validity assertion
  source: ClinGen
  assertion_type: gene_disease_validity
  external_id: CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
  url: https://search.clinicalgenome.org/kb/gene-validity/CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
  description: >-
    The ClinGen Hearing Loss Gene Curation Expert Panel classifies the autosomal dominant
    GJB3-nonsyndromic hearing loss relationship as Disputed, approved 2018-02-27. Its
    evidence summary is unusually explicit about why: the association rested on case-level
    data only, many reported variants are present at high frequency in population databases
    or have no evidence for pathogenicity, and only three variants had enough evidence to
    score.
  evidence:
  - reference: CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
    reference_title: GJB3 / nonsyndromic genetic hearing loss (Disputed)
    supports: REFUTE
    evidence_source: OTHER
    snippet: "GJB3 | HGNC:4285 | nonsyndromic genetic hearing loss | MONDO:0019497 | AD | Disputed"
    explanation: >-
      The expert-panel classification row, with the dominant mode of inheritance DFNA2B
      claims.
  - reference: CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
    reference_title: GJB3 / nonsyndromic genetic hearing loss (Disputed)
    supports: REFUTE
    evidence_source: OTHER
    snippet: >-
      In summary, there is convincing evidence disputing the association between GJB3 and
      autosomal dominant nonsyndromic hearing loss.
    explanation: >-
      The panel's conclusion sentence. Read together with the sentence that follows it and
      with the framework's published definition, quoted below: Disputed covers insufficient
      as well as contradictory evidence, and the panel explicitly declines to rule the
      reported evidence out.
  - reference: CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
    reference_title: GJB3 / nonsyndromic genetic hearing loss (Disputed)
    supports: REFUTE
    evidence_source: OTHER
    snippet: >-
      Multiple missense and nonsense variants have been reported in humans, however many of
      these variants are present in high frequency in population databases and/or have no
      evidence for pathogenicity.
    explanation: >-
      The specific reason the reported variant count overstates the evidence.
  - reference: CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
    reference_title: GJB3 / nonsyndromic genetic hearing loss (Disputed)
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      More evidence is needed to either support or refute the role GJB3 plays in this disease.
    explanation: >-
      The sentence immediately following the panel's conclusion, and it qualifies it: the
      panel is not asserting the relationship is false, it is saying the question is open and
      currently answered against. Quoted here so the classification is not read as stronger
      than the source supports.
  - reference: PMID:30894701
    reference_title: ClinGen expert clinical validity curation of 164 hearing loss gene-disease pairs.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      However, the Disputed classification indicates that the expert panel reviewed the
      evidence and disputed the claim due to insufficient or contradictory evidence.
    explanation: >-
      The HL GCEP's own published definition of what Disputed means. It covers insufficient
      evidence as well as contradictory evidence, which is why this entry does not gloss the
      classification as a positive assertion that GJB3 is not a deafness gene.
  - reference: PMID:30894701
    reference_title: ClinGen expert clinical validity curation of 164 hearing loss gene-disease pairs.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The final outcome included 82 Definitive (50%), 12 Strong (7%), 25 Moderate (15%), 32
      Limited (20%), 10 Disputed (6%), and 3 Refuted (2%) classifications.
    explanation: >-
      Locates Disputed on the scale and shows how rare it is. Ten of 164 hearing-loss
      gene-disease pairs got it, and GJB3-nonsyndromic hearing loss is one of them - which is
      the sense in which this classification is a substantive finding rather than a shrug.
  notes: >-
    The same expert panel classifies GJB3-erythrokeratodermia variabilis as Definitive. One
    gene, two curations by the same group, opposite verdicts - which is the cleanest possible
    demonstration that a gene's disease relationships have to be assessed one at a time.

    The assertion's evidence summary cites PMID 12759707 among the publications in which the
    association was seen. Looked up at PubMed, that identifier is a 2003 Spanish-language
    editorial on smoking prevention in Anales del Sistema Sanitario de Navarra, so it is
    evidently a transcription error in the ClinGen record rather than a hearing-loss report.
    It is cited nowhere in this entry, and no attempt was made to guess which publication was
    intended.

- name: ClinGen GJB3-erythrokeratodermia variabilis gene-disease validity assertion
  source: ClinGen
  assertion_type: gene_disease_validity
  external_id: CGGV:assertion_1d48c959-31d8-44e2-985c-c48921e8f08a-2023-06-01T160000.000Z
  url: https://search.clinicalgenome.org/kb/gene-validity/CGGV:assertion_1d48c959-31d8-44e2-985c-c48921e8f08a-2023-06-01T160000.000Z
  description: >-
    Recorded here for contrast, not because it is this disease. The same Hearing Loss Gene
    Curation Expert Panel rates GJB3's relationship with erythrokeratodermia variabilis
    Definitive, on a 2023 SOP v11 review - five years newer than the Disputed hearing-loss
    curation. dismech curates that disease separately as Erythrokeratodermia Variabilis.
  evidence:
  - reference: CGGV:assertion_1d48c959-31d8-44e2-985c-c48921e8f08a-2023-06-01T160000.000Z
    reference_title: GJB3 / erythrokeratodermia variabilis (Definitive)
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "GJB3 | HGNC:4285 | erythrokeratodermia variabilis | MONDO:0017851 | AD | Definitive"
    explanation: >-
      Establishes the established GJB3 disease, so a reader can see at a glance that the
      Disputed verdict above is specific to hearing loss and is not a judgement about the
      gene.

prevalence:
- population: Chinese hearing-loss cohorts
  measure_type: CARRIER_FREQUENCY
  prevalence_class: UNKNOWN
  notes: >-
    The number usually quoted for DFNA2B is a variant carrier rate in a deaf cohort, and it
    does not survive comparison with controls. Among 5,700 Chinese hearing-loss patients,
    0.40% carried the heterozygous c.538C>T allele; among 4,600 normal-hearing individuals,
    0.24% did, and the difference was not statistically significant. Eleven of the 23 carriers
    also had GJB2 or SLC26A4 mutations, and all 23 were sporadic with no family history of
    deafness - which is not what a dominant disease looks like.

    Other Chinese cohorts point the same way: GJB3 mutations were not common in a 284-patient
    survey, and a putatively causative GJB3 variant accounted for 1 of 100 GJB2-heterozygous
    patients in another. No prevalence for DFNA2B as a disease can be stated, and the
    prevalence_class is UNKNOWN rather than a numeric band for that reason.
  evidence:
  - reference: PMID:29106878
    reference_title: The relationship between the GJB3 c.538C>T variant and hearing phenotype in the Chinese population.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Of the 5700 patients, 23 (0.40%) carried a GJB3 c.538C>T heterozygous variant; of these,
      11 patients had other gene (GJB2/SLC26A4) mutations simultaneously.
    explanation: >-
      The carrier rate in cases, and the confounding: nearly half of the carriers had a
      competing explanation.
  - reference: PMID:29106878
    reference_title: The relationship between the GJB3 c.538C>T variant and hearing phenotype in the Chinese population.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      There was no statistical difference in incidence between the two groups.
    explanation: >-
      The case-control comparison that makes the carrier rate uninformative about causation.
  - reference: PMID:19744334
    reference_title: Comprehensive molecular etiology analysis of nonsyndromic hearing impairment from typical areas in China.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mutations in GJB3, GJB6, and mtDNA tRNAser(UCN) were not common in this Chinese cohort.
    explanation: >-
      An independent cohort reaching the same conclusion about how rarely GJB3 explains
      hearing loss.
  - reference: PMID:37964827
    reference_title: "Comparative analysis of allele frequencies of 15 deafness gene variants between hearing-loss and normal populations in Henan, China."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "the allele frequencies of GJB2 c.235delC variant, GJB3 c.538C > T variant and SLC26A4 c.919-2A > G variant were significantly higher than those of the East Asian population average in the gnomAD database."
    explanation: >-
      An allele proposed as a rare dominant cause of deafness is instead more common in this
      population than the gnomAD East Asian average - which is the population-genetic form of
      the argument against it.

mechanistic_hypotheses:
- hypothesis_group_id: cx31_gap_junction_deafness
  hypothesis_label: >-
    Trafficking-defective connexin 31 disrupts cochlear gap-junction coupling and causes
    dominant high-frequency hearing loss
  status: ALTERNATIVE
  description: >-
    The proposed mechanism, and the reason it is a hypothesis group rather than this entry's
    canonical model.

    Its molecular half is solid. Connexin 31 is a gap junction subunit expressed in the inner
    ear, at high levels in adult inner hair cells and spiral ganglion neurons. Two
    hearing-loss-associated mutants are retained in the ER and in Golgi-like structures,
    fail to transfer dye between cells, and induce the ER chaperone BiP. Two further variants
    fail to couple cells even when co-expressed with wild-type Cx31, which is the shape of a
    dominant-negative effect and is what a dominant disease would need.

    Its organismal half does not exist. No animal carrying a GJB3 variant has been shown to
    hear abnormally; the Cx31-null mouse hears normally and has a structurally normal inner
    ear. No human cochlear pathology has ever been examined. The step from "these channels do
    not work in transfected cells" to "this person is deaf" has not been made in any system.

    Every causal edge below opts into this group. None of them is an established step.
  evidence:
  - reference: PMID:21204020
    reference_title: Trafficking abnormality and ER stress underlie functional deficiency of hearing impairment-associated connexin-31 mutants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Together, the HI-associated C×31 mutants are impaired in trafficking, promote ER
      stress, and hence lose the ability to assemble functional gap junctions.
    explanation: >-
      The molecular half of the hypothesis, measured in transfected cells.
  - reference: PMID:11237463
    reference_title: Connexin31-deficiency in mice causes transient placental dysmorphogenesis but does not impair hearing and skin differentiation.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: >-
      No morphological or functional defects of skin or inner ear were observed in surviving
      adult Gjb3(-/-) mice.
    explanation: >-
      The organismal test, with a negative result in the ear and, notably, in the skin as
      well - so the mouse is uninformative about the established GJB3 disease too.

pathophysiology:

- name: Heterozygous GJB3 Variant
  role: trigger
  biological_scale: MOLECULAR
  description: >-
    GJB3 encodes connexin 31 and is at 1p34.3; the founding report placed it in the broader
    1p33-p35 interval, which is the mapping quoted in the evidence below. The founding report described a missense
    and a nonsense variant in two families with high-frequency hearing loss; the nonsense
    allele, c.538C>T p.Arg180*, became the one routinely screened in Chinese deafness panels
    and is the one that has since failed a case-control test.

    The variants are heterozygous, which is what makes the claimed inheritance dominant and
    which sets the mechanistic requirement: a single altered allele has to produce a
    phenotype, so either haploinsufficiency or a dominant-negative effect on the wild-type
    protein is needed. Haploinsufficiency is hard to sustain given that homozygous null mice
    hear normally, so the dominant-negative reading is the live one - and the coupling
    experiments below were designed to test exactly that.
  genetic_context:
    gene:
      preferred_term: GJB3
      term:
        id: hgnc:4285
        label: GJB3
    variant_origin: GERMLINE
    zygosity: HETEROZYGOUS
    description: >-
      Heterozygous in the reported families. functional_impact_category is omitted
      deliberately: the trafficking data show the mutant protein is made and mislocalised
      rather than absent, and whether that constitutes loss of function or a dominant
      negative is the open question rather than something the entry can assert.
  downstream:
  - target: Connexin 31 Trafficking Failure and ER Retention
    causal_link_type: DIRECT
    hypothesis_groups:
    - cx31_gap_junction_deafness
    description: >-
      Two hearing-loss-associated variants have been shown to do this directly in transfected
      cells.
  evidence:
  - reference: PMID:9843210
    reference_title: Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mutation analysis revealed that a missense mutation and a nonsense mutation of GJB3 were
      associated with high-frequency hearing loss in two families.
    explanation: >-
      The founding association, on two families.
  - reference: PMID:29106878
    reference_title: The relationship between the GJB3 c.538C>T variant and hearing phenotype in the Chinese population.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our results showed that the GJB3 c.538C>T variant has a very low incidence in the
      Chinese population, and there was no clear evidence to support a role of the GJB3
      c.538C>T variant in the autosomal dominant form of non-syndromic deafness.
    explanation: >-
      A direct case-control test of the most-screened allele, which found nothing. This is
      the strongest single human argument against DFNA2B.
  - reference: PMID:29106878
    reference_title: The relationship between the GJB3 c.538C>T variant and hearing phenotype in the Chinese population.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 23 patients were sporadic cases and had no family history of deafness.
    explanation: >-
      Absence of family history in every carrier, which is incompatible with the allele
      acting as a dominant cause.

- name: Connexin 31 Trafficking Failure and ER Retention
  role: central_effector
  biological_scale: MOLECULAR
  description: >-
    Wild-type Cx31 forms functional gap junctions at cell-cell contacts in transfected cells.
    Two hearing-impairment-associated mutants, R180X and E183K, do not: they sit in the
    endoplasmic reticulum and in Golgi-like punctate structures respectively, fail to transfer
    lucifer yellow between cells, and upregulate and bind the ER chaperone BiP, indicating ER
    stress.

    This is the same protein-level lesion that the dismech Erythrokeratodermia Variabilis
    entry describes for the skin disease - Cx31 that does not reach the membrane and so cannot
    take part in gap junction formation. The two entries agree about what happens to the
    protein. They differ in whether the resulting tissue phenotype is established, and only
    the skin one is.
  biological_processes:
  - preferred_term: gap junction assembly by connexin 31
    term:
      id: GO:0016264
      label: gap junction assembly
    modifier: DECREASED
  downstream:
  - target: Loss of Cochlear Gap-Junction Coupling
    causal_link_type: DIRECT
    hypothesis_groups:
    - cx31_gap_junction_deafness
    description: >-
      A channel subunit that never reaches the membrane cannot contribute to intercellular
      coupling.
  evidence:
  - reference: PMID:21204020
    reference_title: Trafficking abnormality and ER stress underlie functional deficiency of hearing impairment-associated connexin-31 mutants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      In contrast, two HI-associated C×31 mutants, C×31R180X and C×31E183K resided primarily
      in the ER and Golgi-like intracellular punctate structures, respectively, and failed to
      mediate lucifer yellow transfer.
    explanation: >-
      The retention and dye-transfer failure, in transfected cells.
  - reference: PMID:21204020
    reference_title: Trafficking abnormality and ER stress underlie functional deficiency of hearing impairment-associated connexin-31 mutants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      In transfected cells, wild type C×31 protein (C×31wt) forms functional gap junction at
      cell-cell-contacts.
    explanation: >-
      The wild-type control that makes the mutant result interpretable.

- name: Loss of Cochlear Gap-Junction Coupling
  role: central_effector
  biological_scale: CELLULAR
  description: >-
    Connexin 31 is one of three connexins named as core components of inner ear gap junctions,
    alongside Cx26 (GJB2) and Cx30 (GJB6). Its expression in the ear is real: RT-PCR detected
    Gjb3 in rat inner ear tissue in the founding study, and it is developmentally regulated in
    mouse with high levels in adult inner hair cells and spiral ganglion neurons.

    The dominant-negative question is decided at this node, and it has been tested. Cx31
    p.Val27Met and p.Val84Ile each failed to function when expressed as heterozygotes
    alongside wild-type Cx31 - which is what a dominant allele needs to do, and which is why
    the hypothesis remains alive despite the mouse.

    What has never been shown is the effect of any of this on a cochlea.
  cell_types:
  - preferred_term: cochlear inner hair cell
    term:
      id: CL:0000589
      label: cochlear inner hair cell
  - preferred_term: spiral ganglion neuron
    term:
      id: CL:0011113
      label: spiral ganglion neuron
  molecular_functions:
  - preferred_term: connexin 31 gap junction channel activity
    term:
      id: GO:0005243
      label: gap junction channel activity
    modifier: DECREASED
  downstream:
  - target: Progressive High-Frequency Sensorineural Hearing Loss
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - cx31_gap_junction_deafness
    description: >-
      The step with no evidence in any organism. The one animal in which it was tested hears
      normally.
  evidence:
  - reference: PMID:21204020
    reference_title: Trafficking abnormality and ER stress underlie functional deficiency of hearing impairment-associated connexin-31 mutants.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      we show that expression of C×31 in the mouse inner ear is developmentally regulated
      with a high level in adult inner hair cells and spiral ganglion neurons that are
      critical for the hearing process.
    explanation: >-
      Localises the protein to auditory cell types. Graded MODEL_ORGANISM because it is mouse
      inner ear tissue, in the same paper whose transfected-cell work is graded IN_VITRO.
  - reference: PMID:22617145
    reference_title: Evaluation of the pathogenicity of GJB3 and GJB6 variants associated with nonsyndromic hearing loss.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      The results of biochemical and ionic coupling tests showed that both the Cx31-p.V27M and
      Cx31-p.V84I variants did not function normally when each was expressed as a heterozygote
      with the wild-type Cx31.
    explanation: >-
      The dominant-negative test, performed under heterozygous conditions, which is the
      configuration a dominant disease requires.
  - reference: PMID:9843210
    reference_title: Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Moreover, expression of Gjb3 was identified in rat inner ear tissue by RT-PCR.
    explanation: >-
      Expression in the inner ear, graded INDIRECT because presence of a transcript is
      consistent with a role and does not establish one.
  - reference: PMID:11237463
    reference_title: Connexin31-deficiency in mice causes transient placental dysmorphogenesis but does not impair hearing and skin differentiation.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We conclude that Cx31 is essential for early placentation but can be compensated for by
      other connexins in the embryo proper and adult mouse.
    explanation: >-
      Offers the reason the mouse is unaffected - compensation by other connexins - which is
      also the reason the mouse result does not fully settle the human question.

- name: Progressive High-Frequency Sensorineural Hearing Loss
  role: consequence
  biological_scale: ORGANISM
  description: >-
    The claimed clinical endpoint: bilateral high-frequency hearing impairment, described in
    the founding report and repeated in reviews as postlingual and progressive.

    It is worth being precise about what the founding paper actually says, because the
    strength of the claim has drifted upward in secondary sources. Its own conclusion is that
    mutations in GJB3 "may be responsible" for bilateral high-frequency hearing impairment -
    hedged in 1998, and the hedge has not been retired since.
  biological_processes:
  - preferred_term: sensory perception of sound
    term:
      id: GO:0007605
      label: sensory perception of sound
    modifier: DECREASED
  evidence:
  - reference: PMID:9843210
    reference_title: Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These findings suggest that mutations in GJB3 may be responsible for bilateral
      high-frequency hearing impairment.
    explanation: >-
      The founding claim in the founding paper's own hedged wording. Graded PARTIAL because
      "may be responsible" is what the source says and is what the evidence has supported ever
      since.
  - reference: CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
    reference_title: GJB3 / nonsyndromic genetic hearing loss (Disputed)
    supports: REFUTE
    evidence_source: OTHER
    snippet: >-
      Association is seen in at least 5 probands in 3 publications
    explanation: >-
      The total human evidence base for this phenotype, twenty years after the founding
      report: five probands.

phenotypes:

- category: Otologic
  name: High-Frequency Sensorineural Hearing Loss
  frequency: FREQUENT
  description: >-
    The characteristic audiometric pattern of the reported families: bilateral loss worst at
    high frequencies. Frequency is FREQUENT rather than OBLIGATE because the denominator is
    unclear - the reported carriers in the case-control study were sporadic and were not
    consistently affected, so this describes the ascertained families rather than everyone
    with a GJB3 variant.
  phenotype_term:
    preferred_term: High-frequency hearing impairment
    term:
      id: HP:0005101
      label: High-frequency hearing impairment
  evidence:
  - reference: PMID:9843210
    reference_title: Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mutation analysis revealed that a missense mutation and a nonsense mutation of GJB3 were
      associated with high-frequency hearing loss in two families.
    explanation: >-
      The audiometric pattern in the two founding families.
  - reference: PMID:29106878
    reference_title: The relationship between the GJB3 c.538C>T variant and hearing phenotype in the Chinese population.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most patients had moderate to profound hearing loss.
    explanation: >-
      The 23 carriers in the case-control series did not have the high-frequency pattern the
      founding families had, which weakens the genotype-phenotype correlation this phenotype
      asserts.

- category: Otologic
  name: Bilateral Involvement
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Bilateral sensorineural hearing impairment
    term:
      id: HP:0008619
      label: Bilateral sensorineural hearing impairment
  description: >-
    Both ears, in the reported families.
  evidence:
  - reference: PMID:9843210
    reference_title: Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These findings suggest that mutations in GJB3 may be responsible for bilateral
      high-frequency hearing impairment.
    explanation: >-
      States bilateral involvement, in the source's own hedged framing.

genetic:

- name: GJB3
  gene_term:
    preferred_term: GJB3
    term:
      id: hgnc:4285
      label: GJB3
  relationship_type: DISPUTED
  notes: >-
    Typed DISPUTED to match the ClinGen Hearing Loss Gene Curation Expert Panel's own
    classification, which used the phrase "convincing evidence disputing the association".
    This is stronger than the Limited classification the same panel gives MET, and it means a
    heterozygous GJB3 variant found in a deaf patient should not be reported as the cause.

    GJB3 encodes connexin 31, a gap junction subunit expressed in epidermis and inner ear. Its
    established disease is erythrokeratodermia variabilis, which the same panel rates
    Definitive and which dismech curates as its own entry. The gene is not in doubt; this
    particular relationship is.

    A practical note on how the dispute plays out in cohorts. GJB3 remains on Chinese deafness
    screening panels, so heterozygous variants keep being reported in deaf patients. In the
    largest series, nearly half of the carriers also had GJB2 or SLC26A4 mutations. A GJB3
    variant in a patient who also carries a GJB2 variant is not evidence for DFNA2B.
  evidence:
  - reference: CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
    reference_title: GJB3 / nonsyndromic genetic hearing loss (Disputed)
    supports: REFUTE
    evidence_source: OTHER
    snippet: >-
      In summary, there is convincing evidence disputing the association between GJB3 and
      autosomal dominant nonsyndromic hearing loss.
    explanation: >-
      The classification this relationship_type encodes.
  - reference: CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
    reference_title: GJB3 / nonsyndromic genetic hearing loss (Disputed)
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Of note, this gene has also been implicated in Erythrokeratodermia variabilis.
    explanation: >-
      The panel's own separation of the two GJB3 relationships, which is why the Disputed
      verdict is about this disease and not about the gene.
  - reference: PMID:29926981
    reference_title: "GJB3/GJB6 screening in GJB2 carriers with idiopathic hearing loss: Is it necessary?"
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Putatively causative GJB3 variant underlied 1% (1/100) in this cohort.
    explanation: >-
      A deliberate test of whether screening GJB3 adds diagnostic yield, which found it adds
      almost none.
  - reference: PMID:37964827
    reference_title: "Comparative analysis of allele frequencies of 15 deafness gene variants between hearing-loss and normal populations in Henan, China."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "our study confirmed that GJB3 c.538C > T variant may not be the disease-causing variant of hearing loss."
    explanation: >-
      A second, independent Chinese case-control series reaching the same verdict on the
      allele that carries most of the DFNA2B claim. Two such studies from different provinces
      is what makes this a replicated negative rather than one group's result.
  - reference: PMID:9843210
    reference_title: Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      GJB3 was mapped to human chromosome 1p33-p35.
    explanation: >-
      The gene's map position, established in the founding study.

inheritance:

- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    Dominant transmission is what DFNA2B claims and it is also where the claim is weakest.
    The founding families segregated heterozygous variants with high-frequency hearing loss.
    But in the largest subsequent series every one of the 23 carriers of the most-screened
    allele was a sporadic case with no family history of deafness - the opposite of what
    dominant inheritance predicts, and in a sample far larger than the founding families.
  evidence:
  - reference: PMID:9843210
    reference_title: Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mutation analysis revealed that a missense mutation and a nonsense mutation of GJB3 were
      associated with high-frequency hearing loss in two families.
    explanation: >-
      The family-based observation underlying the dominant claim.
  - reference: PMID:29106878
    reference_title: The relationship between the GJB3 c.538C>T variant and hearing phenotype in the Chinese population.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 23 patients were sporadic cases and had no family history of deafness.
    explanation: >-
      Directly contradicts dominant transmission for the allele that has been screened most
      widely.

animal_models:

- name: Cx31-deficient (Gjb3 lacZ knock-in) mouse
  species: Mouse
  genotype: Gjb3(-/-), targeted replacement of Gjb3 by a lacZ reporter, homozygous
  publication: PMID:11237463
  description: >-
    The only Gjb3 mouse, and its hearing is normal. Homozygotes are largely lost between
    embryonic days 10.5 and 13.5 from placental failure - the labyrinth and spongiotrophoblast
    are severely reduced at E9.5 - but the placenta recovers as connexin 43 comes up, and the
    survivors reach adulthood with no morphological or functional defect of skin or inner ear.

    The authors' own explanation is compensation by other connexins in the embryo proper and
    the adult, which is a live possibility rather than a dismissal: the cochlea expresses Cx26
    and Cx30 alongside Cx31, so redundancy there is entirely plausible. Two further caveats
    matter for reading this animal against DFNA2B. It is a null, and DFNA2B is claimed to be
    dominant, so a dominant-negative human allele is not modelled by removing the gene. And
    the mouse is also normal in skin, where GJB3 causes a Definitive human disease - so this
    animal fails to model the established GJB3 phenotype too, which is a reason to weight its
    auditory negative carefully rather than treat it as conclusive.
  modeled_mechanisms:
  - target: Loss of Cochlear Gap-Junction Coupling
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      Complete absence of Cx31 produces no inner ear defect, structural or functional, in the
      adult mouse. The hypothesis that cochlear Cx31 loss causes deafness predicts otherwise.
    limitations: >-
      Three limitations, and together they are why fidelity is LOW rather than higher. The
      model is a homozygous null and the human disease is claimed to be dominant, so a
      dominant-negative allele acting on wild-type Cx31 is not tested here. The authors
      attribute the normal phenotype to compensation by other connexins, and the cochlea
      expresses Cx26 and Cx30, so compensation is a specific and untested alternative to
      "Cx31 does not matter for hearing". Most tellingly, the same mouse is normal in skin,
      where the human GJB3 relationship is rated Definitive - so this animal demonstrably
      fails to model an established GJB3 disease, and its auditory negative cannot carry more
      weight than its dermatological one.
    readouts:
    - name: Inner ear morphology and auditory function in adult Gjb3-null mice
      target: Loss of Cochlear Gap-Junction Coupling
      direction: UNCHANGED
      interpretation: >-
        No structural or functional inner ear abnormality in the complete absence of connexin
        31. A deliberate negative result in the only animal that has tested the question.
      evidence:
      - reference: PMID:11237463
        reference_title: Connexin31-deficiency in mice causes transient placental dysmorphogenesis but does not impair hearing and skin differentiation.
        supports: REFUTE
        evidence_source: MODEL_ORGANISM
        snippet: >-
          No morphological or functional defects of skin or inner ear were observed in
          surviving adult Gjb3(-/-) mice.
        explanation: >-
          The measurement behind this readout. It reports skin and inner ear together, which
          is also the sentence that establishes the model's failure in the established GJB3
          disease.
    - name: Placental labyrinth and spongiotrophoblast size at E9.5
      target: Loss of Cochlear Gap-Junction Coupling
      direction: DECREASED
      interpretation: >-
        The one phenotype the null mouse does have, recorded because it establishes that the
        targeting worked and the animal is a genuine null - so the auditory negative is not an
        artefact of a failed knockout.
      evidence:
      - reference: PMID:11237463
        reference_title: Connexin31-deficiency in mice causes transient placental dysmorphogenesis but does not impair hearing and skin differentiation.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Placentas of Gjb3(-/-) embryos at ED 9.5 were smaller than controls as a result of
          severely reduced labyrinth and spongiotrophoblast size.
        explanation: >-
          Demonstrates a real loss-of-function phenotype elsewhere, which is what makes the
          normal ear meaningful.
    evidence:
    - reference: PMID:11237463
      reference_title: Connexin31-deficiency in mice causes transient placental dysmorphogenesis but does not impair hearing and skin differentiation.
      supports: REFUTE
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Mutations in the human GJB3 gene that codes for Connexin31 (Cx31), a protein subunit of
        gap junction channels, have recently been reported to cause deafness and the skin
        disorder erythrokeratodermia variabilis.
      explanation: >-
        Establishes that this mouse was built to test the human deafness claim, which is what
        makes its negative result a failure to recapitulate rather than an unrelated
        observation.

diagnosis:
- name: Interpretation of a GJB3 variant found on a deafness panel
  description: >-
    GJB3 is on hereditary hearing loss panels, particularly in China where it has been part of
    routine deafness screening for two decades, so heterozygous GJB3 variants will continue to
    be reported in deaf patients regardless of the Disputed classification. What follows is a
    reporting question rather than a testing one.

    Four things should be established before a GJB3 variant is offered as an explanation.
    Whether KCNQ4 has been sequenced, because DFNA2A sits in the same mapped interval, has the
    same audiogram, and is an established relationship where this one is not. Whether the
    patient also carries a GJB2 or SLC26A4 variant, because nearly half of the GJB3 carriers
    in the largest series did. Whether there is a family history consistent with dominant
    transmission, because none of those 23 carriers had one. And whether the audiogram is
    high-frequency, because the carriers in that series mostly had moderate to profound loss
    rather than the founding families' pattern.
  evidence:
  - reference: PMID:29106878
    reference_title: The relationship between the GJB3 c.538C>T variant and hearing phenotype in the Chinese population.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Of the 5700 patients, 23 (0.40%) carried a GJB3 c.538C>T heterozygous variant; of these,
      11 patients had other gene (GJB2/SLC26A4) mutations simultaneously.
    explanation: >-
      The co-occurrence rate that makes checking for a competing variant the first step.
  - reference: PMID:29926981
    reference_title: "GJB3/GJB6 screening in GJB2 carriers with idiopathic hearing loss: Is it necessary?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      GJB3/GJB6 variants account for a low proportion in autosomal recessive GJB2 mutation
      carriers in our cohort.
    explanation: >-
      A study that asked directly whether GJB3 screening is worth doing and found the yield
      low.
  - reference: PMID:20301388
    reference_title: DFNA2 Nonsyndromic Hearing Loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The diagnosis of DFNA2 nonsyndromic hearing loss is established in an individual with a
      characteristic audioprofile, a family history consistent with autosomal dominant
      inheritance, and identification of a heterozygous pathogenic variant in KCNQ4.
    explanation: >-
      The established alternative at the same locus, and the first thing to exclude before a
      GJB3 variant is reported as causal.

differential_diagnoses:
- name: DFNA2A - KCNQ4-related autosomal dominant nonsyndromic hearing loss
  description: >-
    The other half of the DFNA2 locus this entity is named for, and the single most important
    alternative to name. KCNQ4 sits at 1p34, in the same originally mapped interval as GJB3,
    and DFNA2A produces the clinical picture this entry describes: symmetric, dominant,
    progressive, worst at high frequencies. The difference is that the KCNQ4 relationship is
    established, with a characteristic audioprofile specific enough that a machine-learning
    tool prioritises the gene from the audiogram alone.

    For an entry whose practical point is that a heterozygous GJB3 variant should not be
    reported as the cause of a patient's deafness, "was KCNQ4 sequenced" is the first question
    to ask, and it is in the diagnosis section for that reason. Whoever curates DFNA2A next
    will find the stub at stubs/Autosomal_Dominant_Nonsyndromic_Hearing_Loss_2A.yaml.
  evidence:
  - reference: PMID:20301388
    reference_title: DFNA2 Nonsyndromic Hearing Loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      DFNA2 nonsyndromic hearing loss is characterized by symmetric, predominantly
      high-frequency sensorineural hearing loss (SNHL) that is progressive across all
      frequencies.
    explanation: >-
      The DFNA2A phenotype, which is the phenotype DFNA2B is described as having. That two
      loci in one mapped interval carry the same audiogram is why the differential matters.
  - reference: PMID:20301388
    reference_title: DFNA2 Nonsyndromic Hearing Loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The diagnosis of DFNA2 nonsyndromic hearing loss is established in an individual with a
      characteristic audioprofile, a family history consistent with autosomal dominant
      inheritance, and identification of a heterozygous pathogenic variant in KCNQ4.
    explanation: >-
      The established diagnostic criteria for the alternative, against which the DFNA2B claim
      has none.
  - reference: PMID:18941426
    reference_title: Audioprofile-directed screening identifies novel mutations in KCNQ4 causing hearing loss at the DFNA2 locus.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Those families predicted to have a DFNA2 audioprofile by AudioGene v2.0 were screened
      for mutations in the KCNQ4 gene.
    explanation: >-
      Shows the DFNA2 audioprofile is specific enough to direct screening to KCNQ4, which is
      what makes audiogram shape a usable discriminator in this differential.

- name: Erythrokeratodermia variabilis (GJB3-related)
  description: >-
    The established GJB3 disease and the one this entry must not be confused with. It is a
    disorder of cornification - transient figurate erythema with fixed hyperkeratotic plaques
    - and the same ClinGen expert panel rates the GJB3 relationship Definitive. dismech
    curates it as Erythrokeratodermia Variabilis, and the two entries agree about the protein:
    mutant Cx31 fails to reach the membrane and cannot form gap junctions. They differ in
    whether the tissue-level consequence is established.

    The entities can also co-occur in one family, which is the practically difficult case. A
    Chinese pedigree carrying a heterozygous GJB3 c.293G>A had a daughter with EKV, a mother
    with ichthyosis, and a son with nonsyndromic hearing loss - one allele, three phenotypes,
    and no explanation offered beyond genetic, epigenetic and environmental modifiers. A
    single such family is not evidence that GJB3 causes deafness; it is evidence that the
    question is hard to settle by pedigree.
  evidence:
  - reference: CGGV:assertion_1d48c959-31d8-44e2-985c-c48921e8f08a-2023-06-01T160000.000Z
    reference_title: GJB3 / erythrokeratodermia variabilis (Definitive)
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      GJB3 | HGNC:4285 | erythrokeratodermia variabilis | MONDO:0017851 | AD | Definitive
    explanation: >-
      The expert-panel verdict on the differential entity, five years newer than the Disputed
      hearing-loss curation.
  - reference: PMID:35677558
    reference_title: "A Connexin Gene (GJB3) Mutation in a Chinese Family With Erythrokeratodermia Variabilis, Ichthyosis and Nonsyndromic Hearing Loss: Case Report and Mutations Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mutation analysis revealed all of them carried a heterozygous missense mutation c.293G>A
      of GJB3.
    explanation: >-
      The one-allele-three-phenotypes family. Graded PARTIAL because it is compatible with
      both readings of the DFNA2B question and settles neither.
  - reference: PMID:35677558
    reference_title: "A Connexin Gene (GJB3) Mutation in a Chinese Family With Erythrokeratodermia Variabilis, Ichthyosis and Nonsyndromic Hearing Loss: Case Report and Mutations Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The variation of clinical features may involve with genetic, epigenetic and environmental
      factors.
    explanation: >-
      The authors' own account of why one allele gave three phenotypes, which is a statement of
      not knowing.

- name: GJB2-related nonsyndromic hearing loss (DFNB1)
  description: >-
    The commonest genetic cause of nonsyndromic hearing loss and the competing explanation
    that keeps turning up alongside GJB3 variants. In the largest GJB3 series, 11 of 23
    carriers also had a GJB2 or SLC26A4 mutation. Connexin 26 is the other core inner ear
    connexin, so the two are screened together and confused easily.
  evidence:
  - reference: PMID:22617145
    reference_title: Evaluation of the pathogenicity of GJB3 and GJB6 variants associated with nonsyndromic hearing loss.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Connexins (Cx26 encoded by GJB2, Cx31 encoded by GJB3 and Cx30 encoded by GJB6) are core
      components of gap junctions in the inner ear.
    explanation: >-
      Names the three connexins that are screened and interpreted together, which is where the
      confusion arises. Graded OTHER because this sentence is background from the paper's
      introduction and reports no study of its own; the same paper's coupling result is graded
      IN_VITRO elsewhere in this entry.

discussions:

- discussion_id: gap_gjb3_dominant_negative_untested_in_vivo
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - genetic#GJB3
  - mechanistic_hypotheses#cx31_gap_junction_deafness
  prompt: >-
    Does a heterozygous trafficking-defective GJB3 allele cause hearing loss in any organism?
  rationale: >-
    The evidence base has a specific shape: everything below the tissue level supports the
    hypothesis and nothing at the tissue level tests it in the right genotype.

    Cx31 mutants are retained in the ER, induce BiP, and fail to transfer dye. Two variants
    fail to couple even alongside wild-type Cx31, which is the dominant-negative behaviour a
    dominant disease requires. But the only animal ever made is a homozygous null, and it is
    normal - and a null cannot test a dominant negative, because there is no wild-type protein
    left for the mutant to poison.

    So the decisive experiment has not been done. A mouse heterozygous for a human DFNA2B
    allele - R180X or E183K knocked in - is the direct test, and it is a standard experiment
    that nobody appears to have run in the twenty-eight years since the association was
    proposed. Until it is, the human case-control data are the best evidence available, and
    they are negative.
  proposed_experiments:
  - experiment_id: gjb3_knockin_heterozygote_auditory_phenotype
    name: Auditory phenotyping of mice heterozygous for a human DFNA2B GJB3 allele
    description: >-
      Knock the human R180X and E183K alleles into the mouse Gjb3 locus, phenotype
      heterozygotes with auditory brainstem responses and distortion-product otoacoustic
      emissions across the frequency range and across age, and examine cochlear gap junction
      plaques for Cx26 and Cx30 as well as Cx31 to test whether the mutant protein disrupts
      the other connexins.
    would_support:
    - mechanistic_hypotheses#cx31_gap_junction_deafness
    supporting_outcome:
    - >-
      Heterozygous knock-in mice develop progressive high-frequency hearing loss where nulls
      do not, which would establish a dominant-negative mechanism, explain why the null mouse
      is normal, and warrant revisiting the Disputed classification.
    refuting_outcome:
    - >-
      Heterozygotes hear normally, which together with the case-control data would leave
      DFNA2B without support in either humans or animals and would make retirement of the
      entity the right curation outcome.

- discussion_id: mismatch_gjb3_null_mouse_normal_in_skin_too
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - animal_models#Cx31-deficient (Gjb3 lacZ knock-in) mouse
  prompt: >-
    How much weight should the normal hearing of the Cx31-null mouse carry, given that the
    same mouse is also normal in skin, where GJB3 causes an established human disease?
  rationale: >-
    This is the strongest argument available to the pro-DFNA2B side and it should be recorded
    as such rather than buried. The single sentence that reports normal hearing in the
    Gjb3-null mouse reports normal skin in the same breath - and GJB3-erythrokeratodermia
    variabilis is rated Definitive by the same expert panel that disputes the hearing loss.
    An animal that fails to model a Definitive human disease is a weak instrument for ruling
    out a disputed one.

    There is a coherent reading in which both are explained at once. Human EKV is dominant and
    the alleles behave as dominant negatives; the mouse is a null; nulls do not model dominant
    negatives; and connexin redundancy - the authors' own explanation - covers the rest.
    Under that reading the mouse says nothing about either disease and the DFNA2B question
    turns entirely on the human data, which is where the case-control study becomes decisive.

    The alternative reading is that mouse and human connexin biology simply differ enough in
    both organs that neither negative transfers. Nothing published distinguishes these.
  proposed_experiments:
  - experiment_id: gjb3_null_mouse_skin_and_ear_reassessment
    name: Reassessment of the Gjb3-null mouse against the established skin phenotype
    description: >-
      Re-phenotype Gjb3-null and heterozygous mice with modern dermatological and auditory
      assays alongside a Gjb3 EKV-allele knock-in, and determine whether the knock-in
      reproduces the human skin phenotype. Whether the model can reproduce the Definitive
      disease sets the ceiling on what its silence about the disputed one is worth.
    would_support:
    - animal_models#Cx31-deficient (Gjb3 lacZ knock-in) mouse
    supporting_outcome:
    - >-
      A knock-in reproduces the human skin phenotype while heterozygous ears stay normal,
      which would show the model is capable of reporting a GJB3 disease and would make its
      auditory silence substantive evidence against DFNA2B.
    refuting_outcome:
    - >-
      No mouse genotype reproduces the human skin phenotype either, which would establish that
      mouse Gjb3 does not report human GJB3 disease at all and would remove the strongest
      animal argument currently cited against DFNA2B.

notes: >-
  Named entity check. GJB3 causes erythrokeratodermia variabilis, which dismech already
  curates and which the same ClinGen expert panel rates Definitive. That entry was read before
  this one was written, and the two agree about the protein: mutant connexin 31 fails to reach
  the membrane and cannot form gap junctions. They diverge only on whether the tissue-level
  consequence is established, and this entry says plainly that its own is not. Nothing
  dermatological is curated here as a DFNA2B phenotype; EKV appears under differential
  diagnoses, with its own ClinGen assertion cited alongside so the contrast is visible in the
  data rather than only in prose.

  On the questioned association, which the curation issue asked about specifically. The answer
  is that the evidence is weaker than the OMIM entry implies and the entry says so throughout
  rather than curating around it: the gene is typed DISPUTED, the mechanism is a hypothesis
  group with status ALTERNATIVE, the founding claim is graded PARTIAL because the founding
  paper itself says "may be responsible", the case-control study is cited as REFUTE in four
  separate sections, and the mouse is FAILS_TO_RECAPITULATE.

  The strongest counter-argument is recorded too. The Gjb3-null mouse is normal in skin as
  well as in ear, and GJB3-EKV is Definitive - so an animal that cannot report an established
  GJB3 disease is a poor instrument for excluding a disputed one. That is a real weakness in
  the case against DFNA2B and it is written into the animal model's limitations and into its
  own HUMAN_MODEL_MISMATCH discussion, not left out because it cuts against the entry's
  overall direction.

  GeneReviews. PMID:20301607, the Genetic Hearing Loss Overview, is cached and is tagged in
  three sibling hearing-loss entries, but it is not tagged here. Its cached record is
  abstract-only and contains no occurrence of GJB3, DFNA2 or connexin, so tagging it would
  produce a tagged-but-not-mined reference. There is no GJB3-specific GeneReviews chapter.
  There is a DFNA2 chapter, PMID:20301388, and it is about KCNQ4/DFNA2A rather than GJB3 - it
  is cited in the differential diagnoses for exactly that reason. This paragraph records the
  negative so it is auditable rather than looking like an omission.

  A defective source in the ClinGen record. The Disputed assertion's evidence summary lists
  PMID 12759707 among the publications in which the association was seen. Looked up at PubMed,
  that identifier is a 2003 Spanish-language editorial on smoking prevention in Anales del
  Sistema Sanitario de Navarra - so it is a transcription error upstream, not a hearing-loss
  report. It is noted on the external assertion, cited nowhere, and no guess was made at which
  publication was meant.

  Evidence grading. PMID:21204020 is split: its mouse inner ear expression work is graded
  MODEL_ORGANISM and its transfected-cell trafficking work is graded IN_VITRO, because
  evidence_source describes the experiment rather than the publication. The same rule puts the
  founding paper's rat RT-PCR under MODEL_ORGANISM and its family analysis under
  HUMAN_CLINICAL.

  What is deliberately absent. No treatments: management would be generic hearing
  habilitation, there is no DFNA2B-specific evidence for any of it, and curating a treatment
  for a disputed disease would give the entity a clinical solidity the evidence does not
  support. No clinical trials, no datasets, no progression section - progressive, postlingual,
  fourth-decade onset is repeated in reviews but no primary natural-history data was found for
  it, and asserting a clinical course for a disputed entity on review prose would be the
  wrong kind of completeness.

references:
- reference: PMID:9843210
  title: Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.
- reference: PMID:11237463
  title: Connexin31-deficiency in mice causes transient placental dysmorphogenesis but does not impair hearing and skin differentiation.
- reference: PMID:21204020
  title: Trafficking abnormality and ER stress underlie functional deficiency of hearing impairment-associated connexin-31 mutants.
- reference: PMID:22617145
  title: Evaluation of the pathogenicity of GJB3 and GJB6 variants associated with nonsyndromic hearing loss.
- reference: PMID:29106878
  title: The relationship between the GJB3 c.538C>T variant and hearing phenotype in the Chinese population.
- reference: PMID:29926981
  title: "GJB3/GJB6 screening in GJB2 carriers with idiopathic hearing loss: Is it necessary?"
- reference: PMID:37964827
  title: "Comparative analysis of allele frequencies of 15 deafness gene variants between hearing-loss and normal populations in Henan, China."
- reference: PMID:19744334
  title: Comprehensive molecular etiology analysis of nonsyndromic hearing impairment from typical areas in China.
- reference: PMID:35677558
  title: "A Connexin Gene (GJB3) Mutation in a Chinese Family With Erythrokeratodermia Variabilis, Ichthyosis and Nonsyndromic Hearing Loss: Case Report and Mutations Update."
- reference: PMID:30894701
  title: ClinGen expert clinical validity curation of 164 hearing loss gene-disease pairs.
- reference: PMID:20301388
  title: DFNA2 Nonsyndromic Hearing Loss.
  tags:
  - GeneReviews
- reference: PMID:18941426
  title: Audioprofile-directed screening identifies novel mutations in KCNQ4 causing hearing loss at the DFNA2 locus.
- reference: CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
  title: GJB3 / nonsyndromic genetic hearing loss (Disputed)
- reference: CGGV:assertion_1d48c959-31d8-44e2-985c-c48921e8f08a-2023-06-01T160000.000Z
  title: GJB3 / erythrokeratodermia variabilis (Definitive)
📚

References & Deep Research

References

14
PMID:9843210
Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.
No top-level findings curated for this source.
PMID:11237463
Connexin31-deficiency in mice causes transient placental dysmorphogenesis but does not impair hearing and skin differentiation.
No top-level findings curated for this source.
PMID:21204020
Trafficking abnormality and ER stress underlie functional deficiency of hearing impairment-associated connexin-31 mutants.
No top-level findings curated for this source.
PMID:22617145
Evaluation of the pathogenicity of GJB3 and GJB6 variants associated with nonsyndromic hearing loss.
No top-level findings curated for this source.
PMID:29106878
The relationship between the GJB3 c.538C>T variant and hearing phenotype in the Chinese population.
No top-level findings curated for this source.
PMID:29926981
GJB3/GJB6 screening in GJB2 carriers with idiopathic hearing loss: Is it necessary?
No top-level findings curated for this source.
PMID:37964827
Comparative analysis of allele frequencies of 15 deafness gene variants between hearing-loss and normal populations in Henan, China.
No top-level findings curated for this source.
PMID:19744334
Comprehensive molecular etiology analysis of nonsyndromic hearing impairment from typical areas in China.
No top-level findings curated for this source.
PMID:35677558
A Connexin Gene (GJB3) Mutation in a Chinese Family With Erythrokeratodermia Variabilis, Ichthyosis and Nonsyndromic Hearing Loss: Case Report and Mutations Update.
No top-level findings curated for this source.
PMID:30894701
ClinGen expert clinical validity curation of 164 hearing loss gene-disease pairs.
No top-level findings curated for this source.
PMID:20301388
DFNA2 Nonsyndromic Hearing Loss.
No top-level findings curated for this source.
PMID:18941426
Audioprofile-directed screening identifies novel mutations in KCNQ4 causing hearing loss at the DFNA2 locus.
No top-level findings curated for this source.
CGGV:assertion_f83e013a-685f-405b-89d6-a8e80aefaf6e-2018-02-27T170000.000Z
GJB3 / nonsyndromic genetic hearing loss (Disputed)
No top-level findings curated for this source.
CGGV:assertion_1d48c959-31d8-44e2-985c-c48921e8f08a-2023-06-01T160000.000Z
GJB3 / erythrokeratodermia variabilis (Definitive)
No top-level findings curated for this source.

Deep Research

1
Falcon ▸
Disease Characteristics Research Template
Edison Scientific Literature 15 citations 2026-08-28T19:09:06.099808

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

  • Disease Name: Autosomal Dominant Nonsyndromic Hearing Loss 2B (DFNA2B, GJB3-related)
  • MONDO ID: MONDO:0012976 (if available)
  • Category: Genetic

Research Objectives

Please provide a comprehensive research report on Autosomal Dominant Nonsyndromic Hearing Loss 2B (DFNA2B, GJB3-related) covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

  • What is the disease? Provide a concise overview.
  • What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
  • What are the common synonyms and alternative names?
  • Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

  • Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
  • Risk Factors:

    Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases

  • Genetic risk factors (causal variants, susceptibility loci, modifier genes)
  • Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
  • Protective Factors:

    Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases

  • Genetic protective factors (protective variants, modifier alleles)
  • Environmental protective factors (diet, lifestyle, exposures that reduce risk)
  • Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

    Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

  • Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

    Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene

  • Pathogenic Variants:
  • Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
  • Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
  • Variant type/class (missense, frameshift, nonsense, splice-site, structural)
  • Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
  • Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
  • Functional consequences (loss of function, gain of function, dominant negative)
  • Modifier Genes: Genes that modify disease severity or expression
  • Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

    Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth

  • Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

    Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

  • Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

    Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases

  • Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

    Search first: CDC databases, WHO, PubMed, NHANES

  • Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

    Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

  • Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

    Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc

  • Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

    Search first: Gene Ontology (GO), Reactome, KEGG, PubMed

  • Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

    Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold

  • Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

    Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA

  • Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

    Search first: ImmPort, Immunome Database, IEDB, Gene Ontology

  • Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

    Search first: PubMed, Gene Ontology, Reactome

  • Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

    Search first: BRENDA, UniProt, KEGG, OMIM, PubMed

  • Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

    Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth

  • Molecular Profiling (if available):
  • Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
  • Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
  • Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
  • Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
  • Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
  • Advanced Technologies (if applicable):
  • Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
  • Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
  • Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
  • Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

  • Organ Level:
  • Primary organs directly affected
  • Secondary organ involvement (complications, secondary effects)
  • Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

    Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT

  • Tissue and Cell Level:
  • Specific tissue types affected (epithelial, connective, muscle, nervous)
  • Specific cell populations targeted (with Cell Ontology terms)

    Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB

  • Subcellular Level:
  • Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

    Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas

  • Localization:
  • Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
  • Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

  • Onset:
  • Typical age of onset (congenital, pediatric, adult, geriatric)
  • Onset pattern (acute, subacute, chronic, insidious)

    Search first: OMIM, Orphanet, HPO, PubMed

  • Progression:
  • Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
  • Progression rate (rapid, slow, variable)
  • Disease course pattern (episodic, relapsing-remitting, progressive, stable)
  • Disease duration (self-limited, chronic lifelong)

    Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM

  • Patterns:
  • Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
  • Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

  • Epidemiology:
  • Prevalence (cases per 100,000 at given time)
  • Incidence (new cases per 100,000 per year)

    Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries

  • For Genetic Etiology:
  • Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
  • Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
  • Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
  • Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
  • Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
  • Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
  • Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
  • Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
  • Population Demographics:
  • Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
  • Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
  • Geographic distribution of specific variants
  • Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
  • Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

  • Clinical Tests:
  • Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
  • Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
  • Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
  • Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
  • Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
  • Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
  • Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
  • Genetic Testing:

    Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen

  • Overview of recommended genetic testing approach
  • Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
  • Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
  • Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
  • Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
  • Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
  • Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
  • FISH > Search first: ClinVar, cytogenetics databases, PubMed
  • Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
  • Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
  • Omics-Based Diagnostics (if applicable):
  • RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
  • Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
  • Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
  • Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
  • Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
  • Clinical Criteria:
  • Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
  • Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
  • Screening:
  • Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

  • Survival and Mortality:
  • Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
  • Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
  • Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
  • Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
  • Morbidity and Function:
  • Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
  • Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
  • Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
  • Disease Course:
  • Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
  • Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
  • Prediction:
  • Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
  • Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

  • Pharmacotherapy:
  • Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
  • Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
  • Advanced Therapeutics:
  • Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
  • Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
  • RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
  • Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
  • Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
  • Surgical and Interventional:
  • Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
  • Supportive and Rehabilitative:
  • Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
  • Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
  • Experimental:
  • Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
  • Treatment Outcomes:
  • Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
  • Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
  • Treatment Strategy:
  • Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
  • Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
  • Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest NCIT (NCI Thesaurus) clinical-intervention terms where applicable.

13. Prevention

  • Prevention Levels:
  • Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
  • Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
  • Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
  • Immunization: Vaccine strategies (if applicable)

    Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database

  • Screening and Early Detection:
  • Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
  • Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
  • Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
  • Behavioral Interventions: Lifestyle modifications to reduce risk

    Search first: CDC, WHO, behavioral intervention databases, Cochrane Library

  • Counseling: Genetic counseling (risk assessment, family planning guidance)

    Search first: NSGC resources, ACMG guidelines, GeneReviews

  • Public Health:
  • Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
  • Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
  • Prophylaxis: Preventive medications or procedures

    Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

  • Taxonomy: Species affected (with NCBI Taxon identifiers)

    Search first: NCBI Taxonomy

  • Breed: Specific breeds affected (with VBO identifiers if applicable)

    Search first: VBO (Vertebrate Breed Ontology)

  • Gene: Orthologous genes in other species (with NCBI Gene IDs)

    Search first: NCBI Gene

  • Natural Disease:
  • Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
  • Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
  • Comparative Biology:
  • Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
  • Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
  • Transmission (if applicable):
  • Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
  • Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

  • Model Types:
  • Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
  • Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
  • Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
  • Genetic Models:
  • Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
  • Model Characteristics:
  • Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
  • Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
  • Applications:
  • Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
  • Resources:
  • Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

  • Cite primary literature (PMID preferred) for all mechanistic and clinical claims
  • Prioritize recent reviews and landmark papers
  • Include direct quotes from abstracts where possible to support key statements
  • Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, NCIT, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (NCIT terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Autosomal Dominant Nonsyndromic Hearing Loss 2B (DFNA2B; historically GJB3-related)

Executive summary and evidence qualification

DFNA2B is the historical designation for a rare, autosomal-dominant, nonsyndromic sensorineural hearing-loss phenotype attributed to heterozygous variants in GJB3, which encodes connexin-31 (Cx31). The reported phenotype is usually postlingual, bilateral, progressive, and greatest at high frequencies. A 2023 review places typical recognition in the fourth decade and reports milder loss in females. However, the underlying evidence consists principally of a few small families, and several observations weaken a simple monogenic interpretation: some purported variants occur at appreciable population frequencies, later families show multigenic ambiguity, DFNA2 is genetically heterogeneous, and Gjb3-null mice have normal hearing. Accordingly, a GJB3 result should not establish DFNA2B without rigorous ACMG/AMP classification, phenotype matching, segregation, population-frequency review, and exclusion of better-established hearing-loss genes. (dominguez2012geneticsofhearing pages 5-6, alde2023autosomaldominantnonsyndromic pages 2-3, chen2018gjb3gjb6screeningin pages 2-4, petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4, wingard2015cellularanddeafness pages 8-9)

domain strongest finding evidence type confidence/caveat
Historical gene-disease association DFNA2B was historically attributed to GJB3/connexin 31 based on two small Chinese autosomal-dominant families with high-frequency hearing loss; later reviews note the evidence base is limited and DFNA2 is genetically heterogeneous. (petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4, dominguez2012geneticsofhearing pages 5-6) Human family reports summarized in reviews Low-moderate confidence for a historical association; small pedigrees and later contradictory/heterogeneous DFNA2 data limit certainty.
Core phenotype Reported DFNA2B phenotype is adult-onset, progressive, sloping/high-frequency sensorineural hearing loss; a 2023 review states hearing loss may be milder in females. (alde2023autosomaldominantnonsyndromic pages 2-3, laer1999autosomaldominantnonsyndromic pages 2-3, petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4) Human clinical reviews Moderate confidence for the broad audiophenotype; low confidence for sex effect because it is sparsely documented in secondary summaries.
Functional variant evidence In vitro studies summarized in a mechanistic review report V27M, V43M, and V84I can reach the membrane yet show loss of dye/ion coupling, supporting impaired gap-junction function. (wingard2015cellularanddeafness pages 7-8) In vitro cell-based functional assays (secondary summary) Moderate confidence that these variants can disrupt coupling in cells; direct disease causality in humans remains less certain.
Trafficking mechanism V174M was reported to fail plasma-membrane targeting and instead accumulate in lysosomes; it may also disturb wild-type Cx26 trafficking. (wingard2015cellularanddeafness pages 8-9) In vitro transfected-cell study (secondary summary) Moderate confidence for a trafficking-defect mechanism; relevance to penetrance and phenotype in vivo is unresolved.
Animal-model calibration Gjb3/Cx31-null mice do not show hearing impairment, despite human variant-based disease claims. (wingard2015cellularanddeafness pages 8-9) Mouse knockout model Important caveat / lowers confidence in a simple haploinsufficiency model; dominant-negative, species-specific, or developmental-context mechanisms remain possible.
Cohort/population evidence In a 2018 Chinese cohort of 100 unrelated NSHI families, one putatively relevant p.V84I finding was detected; the paper estimated a very low allele frequency and interpreted the case as digenic/tri-allelic GJB2/GJB3 ambiguity, not clean monogenic proof. (chen2018gjb3gjb6screeningin pages 2-4) Human cohort + segregation/NGS follow-up Low-moderate confidence for contribution of p.V84I; the same study emphasizes ambiguity and possible additive rather than standalone causation.
Current therapy landscape No DFNA2B/GJB3-specific approved therapy was identified; management follows general hereditary hearing-loss care (audiology, hearing aids/cochlear implantation as indicated, counseling). Recent precision-diagnostics literature supports broad NGS-based diagnosis rather than gene-specific treatment. (imizcoz2023nextgenerationsequencingimproves pages 1-2, alde2023autosomaldominantnonsyndromic pages 2-3) Recent clinical review + diagnostic cohort High confidence that no disease-specific therapy currently exists; treatment evidence is extrapolated from broader hereditary hearing-loss practice.
Trial/implementation status The only retrieved GJB3-relevant registered study was NCT06133946, an observational newborn deafness-gene screening cohort, not an intervention trial; it includes a single GJB3 variant among screened targets. (NCT06133946 chunk 1) ClinicalTrials.gov observational study High confidence that current registered activity is screening/epidemiologic rather than therapeutic.

Table: This table summarizes the strongest currently retrievable evidence for the historical DFNA2B–GJB3 association, highlighting where support comes from human families, cell studies, mouse models, and modern screening data. It is useful because the evidence is mixed and requires careful confidence calibration rather than a simple yes/no interpretation.

1. Disease information

Definition

DFNA2B describes inherited nonsyndromic sensorineural hearing loss historically linked to GJB3/Cx31 at chromosome 1p34.3. “Nonsyndromic” means that hearing loss is the principal recognized manifestation; skin disease or peripheral neuropathy should prompt consideration of a distinct, syndromic GJB3-associated phenotype rather than DFNA2B. Historical reports also associated biallelic GJB3 variants with recessive hearing loss, but that is not DFNA2B. (petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4, alde2023autosomaldominantnonsyndromic pages 2-3)

Identifiers and synonyms

  • Requested MONDO identifier: MONDO:0012976. This identifier should be independently verified before database ingestion. The retrieved current Open Targets mapping did not reproduce it; instead, it returned GJB3 against “autosomal dominant nonsyndromic hearing loss 58,” MONDO:0014293, with only one low-scoring evidence item. This discordance is a material ontology-quality warning. (OpenTargets Search: autosomal dominant nonsyndromic hearing loss 2B-GJB3)
  • Common names: DFNA2B; deafness, autosomal dominant 2B; autosomal dominant nonsyndromic hearing loss 2B; GJB3-related nonsyndromic hearing loss; connexin-31-related hearing loss.
  • Gene identifiers: GJB3, gap junction protein beta 3; protein Cx31/connexin-31; Ensembl ENSG00000188910. (OpenTargets Search: autosomal dominant nonsyndromic hearing loss 2B-GJB3)
  • Cytogenetic location: 1p34.3 in the 2023 review; older literature used the broader 1p33–p35 interval. (alde2023autosomaldominantnonsyndromic pages 2-3, petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4)
  • OMIM/Orphanet: no disease-specific accession was securely recovered in the searched full text; these should be curated directly from the live databases rather than inferred.
  • ICD-10/ICD-11 and MeSH: there is no established genotype-specific clinical code in the retrieved evidence. Use the appropriate bilateral sensorineural/genetic hearing-loss code plus molecular diagnosis; MeSH concepts include Hearing Loss, Sensorineural and Hearing Loss, Hereditary.

The evidence summarized here is aggregated disease-level literature, family studies, experimental models, and a trial registry—not individual EHR-derived data.

2. Etiology

Causal and genetic factors

The proposed primary cause is a germline heterozygous GJB3 variant affecting connexin-31 gap-junction function. The original 1998 report described one missense and one nonsense change in two small Chinese families with autosomal-dominant high-frequency hearing loss (Xia et al., published December 1998, DOI: https://doi.org/10.1038/3845). Historical reviews subsequently assigned this association to DFNA2B. (petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4)

The association is not uniformly secure. DFNA2 also includes the well-established KCNQ4/DFNA2A disorder, and some pedigrees mapping to the region had no causal change in either GJB3 or KCNQ4. In the five-generation UCSF-99 family, sequence changes in both genes occurred in affected and unaffected relatives, arguing against either as causal in that family. These findings demonstrate locus and allelic heterogeneity and make broad use of “DFNA2” as a synonym for GJB3 disease incorrect. (dominguez2012geneticsofhearing pages 5-6)

Risk factors

  • A genuinely pathogenic germline allele and an affected parent are the principal proposed risks; for an established heterozygous autosomal-dominant allele, each child has a theoretical 50% transmission probability.
  • Family history may appear negative because of late onset, reduced/age-dependent penetrance, mild expression, or a de novo event. These are general DFNA principles rather than quantified GJB3-specific observations. (alde2023autosomaldominantnonsyndromic pages 2-3)
  • One 2018 Chinese cohort found GJB3 p.Val84Ile in 1/100 unrelated families with monoallelic GJB2 findings. The authors estimated a 0.5% cohort allele frequency, cited approximately 0.25% among Chinese NSHI cases and 0.0037 in 1000 Genomes, and interpreted the family as possibly digenic/tri-allelic GJB2/GJB3, not clean GJB3 monogenic disease. (chen2018gjb3gjb6screeningin pages 2-4)

Environmental, protective, and gene–environment factors

No DFNA2B-specific toxin, infection, lifestyle factor, protective allele, diet, or validated modifier gene was identified. Noise and ototoxic drugs can independently damage hearing and plausibly add to inherited cochlear vulnerability, but a GJB3-specific interaction has not been demonstrated. General environmental causes—including congenital infection, postnatal infection, ototoxicity, and prematurity—account for a substantial fraction of pediatric hearing loss and must remain in the differential rather than being attributed to GJB3. (imizcoz2023nextgenerationsequencingimproves pages 1-2)

3. Phenotypes

The best-supported phenotype is sensorineural hearing impairment, initially affecting high frequencies, with a sloping audiogram and progressive postlingual course. Older summaries report similar audiograms among affected individuals and suggest that clinically evident loss occurred particularly in older male carriers; the 2023 review describes onset in adulthood, commonly the fourth decade, and milder loss in females. These sex and onset estimates derive from very small historical datasets and should not be treated as precise frequencies. (alde2023autosomaldominantnonsyndromic pages 2-3, laer1999autosomaldominantnonsyndromic pages 2-3)

Suggested HPO annotations are:

  • Sensorineural hearing impairment — HP:0000407
  • High-frequency hearing impairment — HP:0005101
  • Progressive hearing impairment — HP:0001730
  • Postlingual hearing impairment — use the current HPO postlingual-onset hearing-loss term after terminology validation
  • Adult onset — HP:0003581
  • Bilateral hearing impairment — apply the current HPO bilateral-hearing-loss term; bilateral disease is typical for DFNA generally but was not explicitly quantified in the original GJB3 families.

Severity ranges from mild or subclinical to moderate in the most specific GJB3 summaries. Profound congenital loss reported with p.Val84Ile occurred in a family also carrying biallelic GJB2 changes and therefore should not define monogenic DFNA2B. Peripheral neuropathy occurred with an in-frame three-base deletion in a Spanish family and is a syndromic exclusion/red flag, not a core DFNA2B feature. GJB3 variants also cause erythrokeratodermia variabilis; skin findings likewise argue against a nonsyndromic classification. (chen2018gjb3gjb6screeningin pages 2-4, petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4)

No disease-specific quality-of-life instrument has been reported. Expected burdens include impaired speech perception—especially in noise—communication difficulty, educational or occupational limitations, and social/emotional effects. General pediatric evidence indicates that early etiologic diagnosis and intervention improve language, cognitive, emotional, and social development. (imizcoz2023nextgenerationsequencingimproves pages 1-2)

4. Genetic and molecular information

GJB3 encodes a connexin subunit. Six connexins oligomerize into a connexon/hemichannel; connexons in adjacent cells dock to create a gap-junction channel permitting intercellular passage of ions, metabolites, and second messengers. (laer1999autosomaldominantnonsyndromic pages 2-3)

Reported classes include missense, nonsense, and in-frame deletion variants. Functionally studied candidates include:

  • p.Val27Met, p.Val43Met, p.Val84Ile: reached the plasma membrane and formed plaques in cell systems but showed loss of dye and ion permeability.
  • p.Val174Met: failed normal membrane targeting, accumulated in lysosomes, and interfered with wild-type Cx26 trafficking while reportedly not altering wild-type Cx31 trafficking.
  • p.Val84Ile (c.250G>A; rs145751680): computationally damaging and functionally abnormal in vitro, but sufficiently frequent and observed in a multigenic family, making standalone pathogenicity uncertain. (chen2018gjb3gjb6screeningin pages 2-4, wingard2015cellularanddeafness pages 7-8, wingard2015cellularanddeafness pages 8-9)

These assays support loss of channel coupling or abnormal trafficking but do not by themselves prove a variant causes dominant human hearing loss. A dominant-negative or altered heteromeric-channel mechanism is more compatible with normal hearing in Gjb3-null mice than simple haploinsufficiency, although this remains an inference. (wingard2015cellularanddeafness pages 8-9)

All reported inherited disease variants are germline; no somatic origin is relevant. No reproducible GJB3-specific modifier gene, epigenetic signature, pathogenic copy-number alteration, translocation, inversion, or other chromosomal abnormality was identified. GJB2 is a plausible interacting connexin in selected reports, but evidence for digenic causation is limited. (chen2018gjb3gjb6screeningin pages 2-4)

5. Environmental information

No infectious agent causes DFNA2B, and the disorder is not transmissible. Smoking, alcohol, exercise, diet, pollution, radiation, or occupational exposures have not been shown to determine GJB3 penetrance. Clinically, ordinary hearing-conservation measures remain prudent because noise and ototoxic exposure can independently worsen auditory function. Infection, prematurity, and ototoxicity should be evaluated as alternative or additional etiologies, especially when onset or progression does not fit the family phenotype. (imizcoz2023nextgenerationsequencingimproves pages 1-2)

6. Mechanism and pathophysiology

Proposed causal chain

  1. A GJB3 sequence variant alters Cx31 folding, trafficking, connexon assembly, docking, gating, or molecular permeability.
  2. Gap-junctional transfer of ions and signaling/metabolic molecules among inner-ear nonsensory/supporting cells—or possibly auditory/peripheral nerve cells—is reduced or qualitatively changed.
  3. Cochlear homeostasis and cellular coupling become less robust.
  4. High-frequency auditory function is affected first, producing a sloping audiogram; dysfunction then progresses to lower frequencies.

Steps 1–2 have cell-based support for selected variants; steps 3–4 remain a biologically plausible but incompletely demonstrated bridge in GJB3 disease. Historical chicken data localized Cx31 to cells lining the scala media but not hair cells, while rat inner-ear expression was also reported. Human cochlear localization remains poorly defined. (laer1999autosomaldominantnonsyndromic pages 2-3, petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4, wingard2015cellularanddeafness pages 8-9)

The traditional “potassium recycling” account should not be stated as established for Cx31. Connexin channels also transmit metabolites, ATP/IP3-related signals, and calcium-wave information, and modern connexin work has challenged potassium-recycling failure as a universal explanation. No GJB3-specific immune, inflammatory, metabolic, lipidomic, metabolomic, or oxidative-stress signature has been established. (wingard2015cellularanddeafness pages 7-8, wingard2015cellularanddeafness pages 8-9)

Suggested annotations include:

  • GO: gap junction assembly; gap-junction-mediated intercellular transport; cell–cell signaling; ion transmembrane transport; cellular homeostasis.
  • GO cellular components: gap junction; connexin complex; plasma membrane; lysosome for trafficking-defective p.Val174Met.
  • Candidate cell types: cochlear supporting/nonsensory epithelial cell; auditory-neuron/Schwann-cell populations only where demonstrated. Use exact CL identifiers after ontology validation.

No DFNA2B-specific single-cell, spatial-transcriptomic, multi-omic, CRISPR-screen, proteomic, metabolomic, or lipidomic study was identified through 2024.

7. Anatomical structures affected

The primary organ is the inner ear/cochlea, within the auditory system. Candidate sites include the scala-media-lining epithelium and auditory nerve, but direct human pathology is lacking. Hair cells themselves were excluded from Cx31 expression in the cited chicken work, so direct hair-cell expression should not be asserted. (laer1999autosomaldominantnonsyndromic pages 2-3)

Suggested anatomical terms include UBERON: inner ear; cochlea; scala media; organ of Corti; stria vascularis; spiral ligament; cochlear nerve. These are candidate knowledge-base annotations and not all are proven GJB3-expression sites. The clinical pattern is expected to be bilateral; no consistent asymmetry, vestibular-organ disease, or secondary-organ involvement is established for nonsyndromic DFNA2B. Peripheral nerve or skin involvement changes the classification to a syndromic GJB3 phenotype. (petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4)

8. Temporal development

The disease is chronic and generally insidious. Current secondary synthesis describes onset in the fourth decade, while older DFNA literature broadly places autosomal-dominant nonsyndromic loss in the second or third decade. Initial high-frequency impairment may be mild or subclinical and progressively involves more frequencies. There are no validated clinical stages, quantified annual threshold shifts, remission pattern, or spontaneous recovery. (alde2023autosomaldominantnonsyndromic pages 2-3, laer1999autosomaldominantnonsyndromic pages 2-3)

The practical intervention window begins before communication disability becomes substantial: identify at-risk relatives, establish baseline audiometry, and monitor serially. Childhood-onset or congenital profound hearing loss should trigger aggressive reassessment for other genes or acquired causes rather than automatic attribution to classic DFNA2B.

9. Inheritance and population

The historical model is autosomal dominant, affecting both sexes, with 50% transmission risk from a heterozygous parent. Expression appears variable and may be age- and sex-dependent; neither penetrance nor the male:female ratio has been quantified. Anticipation, germline mosaicism, founder effects, consanguinity effects, and carrier frequency have not been established. (alde2023autosomaldominantnonsyndromic pages 2-3, laer1999autosomaldominantnonsyndromic pages 2-3)

No reliable prevalence or incidence estimate exists for DFNA2B. The original evidence involved two small Chinese families; a Spanish family had hearing loss plus neuropathy. A later Chinese series found only one p.Val84Ile-positive family among 100 selected cases and did not establish monogenic GJB3 causation. Therefore, ethnicity-specific enrichment and geographic prevalence cannot currently be inferred. (chen2018gjb3gjb6screeningin pages 2-4, petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4)

For context only, disabling hearing loss affects over 5% of the global population, and hearing loss occurs in approximately 1–2 per 1,000 European newborns; these are not DFNA2B-specific estimates. (imizcoz2023nextgenerationsequencingimproves pages 1-2)

10. Diagnostics

Diagnosis should combine:

  1. History: age at onset, progression, noise/ototoxic exposure, infections, and a three-generation pedigree.
  2. Examination: otologic assessment plus targeted examination for skin disease and peripheral neuropathy.
  3. Audiology: pure-tone thresholds, speech testing, tympanometry, otoacoustic emissions, and ABR/ASSR where age or phenotype warrants.
  4. Molecular testing: a comprehensive hereditary-hearing-loss NGS panel with SNV/indel and CNV detection is preferable to GJB3-only testing. Confirm candidate variants orthogonally and perform segregation analysis.
  5. Interpretation: ACMG/AMP classification, population-frequency review, phenotype concordance, and analysis of competing genes—especially KCNQ4, GJB2, GJB6, TECTA, WFS1, ACTG1, POU4F3, MYO6, and EYA4.

A 2023 Spanish study of a 171-nuclear/8-mitochondrial-gene panel produced a diagnosis in 52/155 (34%) cases; 45/52 diagnoses were recessive, 6/52 dominant, 1/52 mitochondrial, and 3/52 involved pathogenic CNVs. Its abstract states that NGS panels “reduce the clinical diagnostic odyssey in hearing loss.” Published 22 September 2023; DOI: https://doi.org/10.3389/fgene.2023.1264899. This supports broad genomic testing, not the validity of any particular GJB3 allele. (imizcoz2023nextgenerationsequencingimproves pages 1-2)

WES or WGS is appropriate after a nondiagnostic panel or for complex/atypical families. CMA, karyotype, FISH, mitochondrial testing, and repeat-expansion testing are not routine DFNA2B tests unless another clinical indication exists. RNA-seq and other omics remain research tools.

Differential diagnoses include KCNQ4-related DFNA2A, other dominant nonsyndromic hearing losses, age-related and noise-induced hearing loss, ototoxicity, congenital infection, auditory neuropathy, and GJB3-associated neuropathy or erythrokeratodermia. Cascade testing is appropriate only after a familial variant has been convincingly classified.

11. Outcome and prognosis

DFNA2B is not known to shorten life expectancy or cause disease-specific mortality. Morbidity is auditory and communication-related. Hearing loss is generally permanent and progressive rather than episodic or remitting. Prognosis depends on baseline thresholds, rate of progression, speech discrimination, age, environmental exposures, and timely rehabilitation; no validated GJB3 molecular prognostic biomarker exists. (alde2023autosomaldominantnonsyndromic pages 2-3, laer1999autosomaldominantnonsyndromic pages 2-3)

Untreated loss can impair communication, education, work, and psychosocial well-being. Hearing technology can improve function but does not correct the molecular defect. Disease-specific hearing-aid or cochlear-implant response rates have not been published.

12. Treatment

There is no approved GJB3-directed drug, gene therapy, RNA therapy, cell therapy, or genome-editing treatment. Standard management is phenotype-directed:

  • serial audiologic monitoring;
  • properly fitted hearing aids for aidable loss;
  • assistive listening devices and communication accommodations;
  • auditory rehabilitation and speech/language support;
  • cochlear-implant evaluation for severe-to-profound loss with inadequate aided speech recognition;
  • treatment of unrelated middle-ear disease and avoidance of unnecessary ototoxic exposure.

Suggested NCIT concepts include Hearing Aid, Cochlear Implantation, Audiologic Evaluation, Speech Therapy, Rehabilitation Therapy, and Genetic Counseling; exact codes should be validated against the current NCIt release.

ClinicalTrials.gov NCT06133946 (CODES) is not a therapy trial. It is an observational Nantong newborn cohort enrolling 35,920 participants, screening 15 variants in GJB2, SLC26A4, MT-RNR1, and GJB3 (c.538C>T), with ABR/ASSR and developmental follow-up. Recruitment ran January 2016–December 2020; the record is active but not recruiting, with estimated completion in December 2028. (NCT06133946 chunk 1)

13. Prevention

Primary prevention of a germline disorder is not available. Risk reduction consists of genetic counseling and reproductive options after confirmation of a pathogenic familial allele: prenatal diagnosis or preimplantation genetic testing may be considered according to patient values and local regulations. Because GJB3 pathogenicity is frequently uncertain, reproductive testing should not be based on a VUS.

Secondary prevention includes cascade testing, baseline audiometry, periodic surveillance, newborn hearing screening, and prompt rehabilitation. Tertiary prevention includes hearing conservation, avoidance of unnecessary ototoxic drugs, communication support, and timely hearing aids or implantation. Vaccination does not prevent DFNA2B but routine immunization can reduce selected acquired infectious causes of hearing loss.

14. Other species and natural disease

Orthologous Gjb3 exists in mouse and other vertebrates. No naturally occurring veterinary disorder convincingly equivalent to human DFNA2B was identified, and there is no zoonotic or cross-species transmission. Conserved connexin architecture makes vertebrates useful for comparative channel biology, but species differences are important: complete Cx31 deficiency in mice causes transient placental dysmorphogenesis without hearing impairment. (wingard2015cellularanddeafness pages 8-9)

Suggested taxonomy annotations include Homo sapiens (NCBI Taxon 9606), Mus musculus (10090), Rattus norvegicus (10116), and Gallus gallus (9031) for the expression evidence. No relevant VBO breed term is applicable.

15. Model organisms and experimental systems

Mouse

The Gjb3/Cx31 knockout is the most important calibration model. It does not reproduce human hearing loss, although placental abnormalities occur transiently. Consequently, it argues against uncomplicated loss-of-function/haploinsufficiency as the universal human mechanism and limits its use as a faithful DFNA2B efficacy model. It remains useful for studying redundancy among connexins and extra-auditory biology. (wingard2015cellularanddeafness pages 8-9)

Cellular systems

HEK293 and HeLa transfection systems have assessed localization, plaque formation, dye transfer, ionic coupling, and interactions with Cx26. They demonstrate functional abnormalities for selected variants, including defective permeability and lysosomal retention, but overexpression, noncochlear cellular context, and uncertain connexin stoichiometry limit translation. (chen2018gjb3gjb6screeningin pages 2-4, wingard2015cellularanddeafness pages 7-8, wingard2015cellularanddeafness pages 8-9)

No validated GJB3 patient-derived iPSC cochlear organoid, humanized knock-in mouse, zebrafish disease model, or CRISPR therapeutic model was identified. High-priority future work includes patient-derived cochlear-like cells, variant-specific knock-in models, allele-specific expression studies, direct human inner-ear localization, and large pedigree-based segregation with modern population databases.

Recent-development assessment (2023–2024)

The principal recent advance is diagnostic rather than GJB3-specific: broad NGS/CNV pipelines are increasingly implemented for genetically heterogeneous hearing loss, with a 34% yield in one 2023 Spanish cohort. The 2023 DFNA review still lists GJB3/DFNA2B and describes fourth-decade, progressive, sloping hearing loss, but it does not resolve the sparse primary evidence or normal-hearing knockout contradiction. No 2023–2024 disease-specific natural-history cohort, validated prevalence study, therapy trial, single-cell atlas analysis, or variant-reclassification study was retrieved. (alde2023autosomaldominantnonsyndromic pages 2-3, imizcoz2023nextgenerationsequencingimproves pages 1-2, wingard2015cellularanddeafness pages 8-9)

Knowledge-base recommendation

Represent DFNA2B as a historical/provisional GJB3-associated dominant nonsyndromic hearing-loss entity with limited evidence, not as an unequivocally established diagnosis for every rare GJB3 variant. Store variant-level assertions separately, record the evidence type, and flag p.Val84Ile and other incompletely segregating alleles for expert review. The highest-value missing data are modern ClinGen-style gene–disease curation, current ClinVar/gnomAD variant review, larger pedigrees, human inner-ear expression data, and variant-specific in-vivo models.

References

  1. (dominguez2012geneticsofhearing pages 5-6): L. M. Dominguez and K. Dodson. Genetics of hearing loss: focus on dfna2. The Application of Clinical Genetics, 5:97-104, Oct 2012. URL: https://doi.org/10.2147/tacg.s35525, doi:10.2147/tacg.s35525. This article has 24 citations.

  2. (alde2023autosomaldominantnonsyndromic pages 2-3): Mirko Aldè, Giovanna Cantarella, Diego Zanetti, Lorenzo Pignataro, Ignazio La Mantia, Luigi Maiolino, Salvatore Ferlito, Paola Di Mauro, Salvatore Cocuzza, Jérôme René Lechien, Giannicola Iannella, Francois Simon, and Antonino Maniaci. Autosomal dominant non-syndromic hearing loss (dfna): a comprehensive narrative review. Biomedicines, 11:1616, Jun 2023. URL: https://doi.org/10.3390/biomedicines11061616, doi:10.3390/biomedicines11061616. This article has 65 citations.

  3. (chen2018gjb3gjb6screeningin pages 2-4): Kaitian Chen, Xuan Wu, Ling Zong, and Hongyan Jiang. Gjb3/gjb6 screening in gjb2 carriers with idiopathic hearing loss: is it necessary? Journal of Clinical Laboratory Analysis, Jun 2018. URL: https://doi.org/10.1002/jcla.22592, doi:10.1002/jcla.22592. This article has 12 citations and is from a peer-reviewed journal.

  4. (petersen2002non‐syndromicautosomal‐dominantdeafness pages 2-4): MB Petersen. Non‐syndromic autosomal‐dominant deafness. Clinical Genetics, 62:1-13, Jul 2002. URL: https://doi.org/10.1034/j.1399-0004.2002.620101.x, doi:10.1034/j.1399-0004.2002.620101.x. This article has 117 citations and is from a peer-reviewed journal.

  5. (wingard2015cellularanddeafness pages 8-9): Jeffrey C. Wingard and Hong-Bo Zhao. Cellular and deafness mechanisms underlying connexin mutation-induced hearing loss – a common hereditary deafness. Frontiers in Cellular Neuroscience, May 2015. URL: https://doi.org/10.3389/fncel.2015.00202, doi:10.3389/fncel.2015.00202. This article has 199 citations.

  6. (laer1999autosomaldominantnonsyndromic pages 2-3): Lut Van Laer, Wyman T. McGuirt, Tao Yang, Richard J.H. Smith, and Guy Van Camp. Autosomal dominant nonsyndromic hearing impairment. American journal of medical genetics, 89 3:167-74, Sep 1999. URL: https://doi.org/10.1002/(sici)1096-8628(19990924)89:3<167::aid-ajmg7>3.0.co;2-v, doi:10.1002/(sici)1096-8628(19990924)89:3<167::aid-ajmg7>3.0.co;2-v. This article has 52 citations.

  7. (wingard2015cellularanddeafness pages 7-8): Jeffrey C. Wingard and Hong-Bo Zhao. Cellular and deafness mechanisms underlying connexin mutation-induced hearing loss – a common hereditary deafness. Frontiers in Cellular Neuroscience, May 2015. URL: https://doi.org/10.3389/fncel.2015.00202, doi:10.3389/fncel.2015.00202. This article has 199 citations.

  8. (imizcoz2023nextgenerationsequencingimproves pages 1-2): T. Imizcoz, C. Prieto-Matos, R. Manrique-Huarte, D. Calavia, A. Huarte, P. C. Pruneda, G. R. Ordoñez, E. Cañada-Higueras, A. Patiño-García, G. Alkorta-Aranburu, M. M. Rodríguez, Kelvin Yuen-Kwong, Chan, Sze Wing Cheng, and S. Taiber. Next-generation sequencing improves precision medicine in hearing loss. Frontiers in Genetics, Sep 2023. URL: https://doi.org/10.3389/fgene.2023.1264899, doi:10.3389/fgene.2023.1264899. This article has 15 citations and is from a peer-reviewed journal.

  9. (NCT06133946 chunk 1): Gang Qin, MD, PhD. Cohort Of DEafness-gene Screening. Affiliated Hospital of Nantong University. 2016. ClinicalTrials.gov Identifier: NCT06133946

  10. (OpenTargets Search: autosomal dominant nonsyndromic hearing loss 2B-GJB3): Open Targets Query (autosomal dominant nonsyndromic hearing loss 2B-GJB3, 1 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.

Artifacts

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Unresolved references

These identifiers did not resolve to a record and may be fabricated. A lookup that failed for transport reasons is indistinguishable from one that failed because the record does not exist, so spot-check before acting on them:

  • DOI:10.1002/(sici)1096-8628(19990924)89:3 (2 mentions) - Identifier did not resolve to a record
  • DOI:10.1002/(sici (1 mention) - Identifier did not resolve to a record

Term Validation

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Terms the report names something else

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

  • MONDO:0012976 (2 mentions) - the report calls it "if available"; MONDO calls it autosomal dominant nonsyndromic hearing loss 2B