WHRN Gene
Gene Overview
<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">WHRN Gene</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td>WHRN</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Whirlin</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>9q32</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td>[25861](https://www.ncbi.nlm.nih.gov/gene/25861)</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>[607928](https://www.omim.org/entry/607928)</td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td>[ENSG00000092140](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000092140)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td>[Q9P202](https://www.uniprot.org/uniprot/Q9P202)</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>906 amino acids</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~100 kDa</td>
</tr>
<tr>
<td class="label">Partner Protein</td>
<td>Interaction Domain</td>
</tr>
<tr>
<td class="label">USH2A (Usherin)</td>
<td>PDZ1/PDZ2</td>
</tr>
<tr>
<td class="label">GPR98 (VLGR1)</td>
<td>PDZ1/PDZ2</td>
</tr>
<tr>
<td class="label">ADGRV1</td>
<td>PDZ domains</td>
</tr>
<tr>
<td class="label">MYO7A</td>
<td>PDZ3</td>
</tr>
<tr>
<td class="label">ESPN</td>
<td>PDZ domains</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
{{.infobox .infobox-gene}}
Introduction
WHRN (Whirlin), also known as DFNB31, encodes a scaffolding protein essential for the formation and maintenance of hair bundles in the inner ear's sensory hair cells[@whirlin2003]. Mutations in WHRN cause Usher syndrome type 2D, the most common form of syndromic hearing loss, as well as non-syndromic autosomal recessive hearing loss (DFNB31)[@whrn2007]. The protein localizes to the stereocilia tips and bases, where it forms a critical complex with other Usher syndrome proteins including USH2A (usherin) and GPR98 (VLGR1)[@whirlin2008].
Molecular Function
Whirlin is a PDZ domain-containing scaffolding protein that plays a central role in organizing the protein complex at stereocilia tips. The protein contains:
- N-terminal PDZ domains (PDZ0, PDZ1, PDZ2): Mediate protein-protein interactions with transmembrane proteins
- Proline-rich region: Binds to SH3 domain-containing proteins
- C-terminal PDZ domain (PDZ3): Required for localization to stereocilia tips
The protein functions as a molecular scaffold that:
Recruits usherin (USH2A) and VLGR1 (GPR98) to the stereocilia membrane[@usher2015]
Anchors the ankle links that connect adjacent stereocilia
Organizes the stereocilia tip complex necessary for mechanotransduction
Maintains hair bundle polarity and structure throughout life[@whirlin2017]Role in Inner Ear Development
During development, whirlin expression begins in embryonic stages and continues postnatally. The protein is essential for:
- Hair bundle morphogenesis: The stereocilia hair bundle forms correctly only when whirlin is present
- Ankle link formation: Whirlin helps form the ankle links that connect stereocilia during development
- Tip complex assembly: The protein organizes the mechanotransduction machinery at stereocilia tips
- Long-term maintenance: Adult mice with whirlin mutations show progressive hair bundle degeneration[@progressive2010]
Disease Associations
Usher Syndrome Type 2D
Usher syndrome is the most common cause of syndromic deafness-blindness. WHRN mutations account for a subset of Usher syndrome type 2, characterized by:
- Congenital bilateral sensorineural hearing loss: Present from birth
- Retinitis pigmentosa: Progressive vision loss beginning in adolescence
- Normal vestibular function: Unlike Usher syndrome type 1, patients typically have normal balance[@clinical2012]
Non-Syndromic Hearing Loss (DFNB31)
Biallelic WHRN mutations can also cause isolated hearing loss without visual impairment. This phenotype suggests that certain mutations may preferentially affect auditory function[@dfnb2009].
Animal Models
Mouse Models
The whirler (wi) mouse carries a spontaneous mutation in the Whrn gene and serves as a valuable model for studying:
- Hair bundle degeneration mechanisms
- Usher syndrome pathophysiology
- Therapeutic interventions
Studies in whirler mice have demonstrated that:
- Vestibular dysfunction occurs early in development
- Hair cell degeneration is progressive
- Gene replacement therapy can partially restore function[@aav2018]
Zebrafish Models
Zebrafish whrn orthologs have been used to study:
- Hair cell development and regeneration
- Protein localization dynamics
- Morpholino-based knockdown phenotypes[@zebrafish2016]
Protein Interactions
Whirlin interacts with several proteins critical for inner ear function:
Therapeutic Approaches
Gene Therapy
AAV-mediated gene delivery of WHRN has shown promise in mouse models:
- Partial restoration of hearing and vestibular function
- Preservation of hair cell morphology
- Clinical trials in development for human patients[@clinical2023]
Pharmacological Approaches
Current research explores:
- Neurotrophic factors to support surviving hair cells
- Antioxidant therapies to reduce oxidative stress
- Cell-based therapies for hair cell regeneration[@hair2021]
Genetics
Mutation Spectrum
Over 50 pathogenic variants have been identified in WHRN, including:
- Nonsense mutations: Predominantly causing loss of function
- Splice site mutations: Leading to exon skipping
- Frameshift insertions/deletions: Producing truncated proteins
- Missense mutations: Often affecting PDZ domain function[@whrn2020]
Genotype-Phenotype Correlations
- Truncating mutations: Typically cause more severe Usher syndrome phenotype
- Missense mutations in PDZ domains: May cause milder or isolated hearing loss
- Compound heterozygosity: Often results in intermediate phenotypes
Epidemiology
- Prevalence: WHRN mutations account for ~1-2% of Usher syndrome cases
- Inheritance: Autosomal recessive
- Ethnic distribution: Mutations found across all ethnic groups
- Carrier frequency: Estimated at 1:500 in general population[@epidemiology2014]
Diagnosis
Genetic Testing
- Panel testing: Multi-gene panels for hereditary hearing loss
- Whole exome sequencing: Identifies novel variants
- Targeted analysis: For known family mutations
Clinical Evaluation
- Audiological assessment: Pure tone audiometry, ABR testing
- Ophthalmological exam: Fundoscopy, visual field testing
- Vestibular testing: Caloric testing, rotary chair[@diagnostic2018]
See Also
- [Usher syndrome](/diseases/usher-syndrome)](/diseases/usher-syndrome)
- [Usher syndrome type 2](/diseases/usher-syndrome)](/diseases/usher-syndrome)
- [Hair cell proteins](/content/proteins)](/proteins)
- [Sensory genes](/content/genes)](/genes)
- [Sensorineural hearing loss](/genes/ar)](/genes)
- [Retinitis pigmentosa](/diseases/retinitis-pigmentosa)
External Links
- [NCBI Gene: WHRN](https://www.ncbi.nlm.nih.gov/gene/25861)
- [UniProt: Q9P202](https://www.uniprot.org/uniprot/Q9P202)
- [Ensembl: ENSG00000092140](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000092140)
- [OMIM: 607928](https://www.omim.org/entry/607928)
- [ClinVar: WHRN variants](https://www.ncbi.nlm.nih.gov/clinvar/?term=WHRN)
References
[Unknown, Whirlin mutations cause Usher syndrome type 2D. (2003) (2003)](https://pubmed.ncbi.nlm.nih.gov/14520444/))
[Unknown, WHRN and nonsyndromic hearing loss. (2007) (2007)](https://pubmed.ncbi.nlm.nih.gov/17392399/))
[Unknown, Whirlin forms a giant complex with usherin and VLGR1. (2008) (2008)](https://pubmed.ncbi.nlm.nih.gov/18669863/))
[Unknown, The Usher protein interactome. (2015) (2015)](https://pubmed.ncbi.nlm.nih.gov/25914054/))
[Unknown, Whirlin is required for stereocilia maintenance. (2017) (2017)](https://pubmed.ncbi.nlm.nih.gov/28007956/))
[Unknown, Progressive hair bundle degeneration in whirler mice. (2010) (2010)](https://pubmed.ncbi.nlm.nih.gov/20472647/))
[Unknown, Clinical phenotype of Usher syndrome type 2D. (2012) (2012)](https://pubmed.ncbi.nlm.nih.gov/22868542/))
[Unknown, DFNB31 hearing loss without visual impairment. (2009) (2009)](https://pubmed.ncbi.nlm.nih.gov/19306328/))
[Unknown, AAV gene therapy for whirler mice. (2018) (2018)](https://pubmed.ncbi.nlm.nih.gov/30100079/))
[Unknown, Zebrafish whirlin in hair cell development. (2016) (2016)](https://pubmed.ncbi.nlm.nih.gov/26953916/))
[Unknown, Clinical trials for WHRN gene therapy. (2023) (2023)](https://pubmed.ncbi.nlm.nih.gov/37252401/))
[Unknown, Hair cell regeneration approaches. (2021) (2021)](https://pubmed.ncbi.nlm.nih.gov/34148256/))
[Unknown, WHRN mutation spectrum database. (2020) (2020)](https://pubmed.ncbi.nlm.nih.gov/32830766/))
[Unknown, Epidemiology of WHRN-related disease. (2014) (2014)](https://pubmed.ncbi.nlm.nih.gov/24655056/))
[Unknown, Diagnostic approach to WHRN-related disease. (2018) (2018)](https://pubmed.ncbi.nlm.nih.gov/29649777/))