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POU3F4
POU class 3 homeobox 4
The POU3F4 gene provides instructions for a protein crucial for the development of the inner ear, specifically the cochlea, and is associated with certain forms of inherited hearing loss. POU3F4 is a gene encoding a transcription factor that plays a vital role in regulating other genes involved in inner ear development.
POU3F4 is located on the long (q) arm of chromosome X, at band Xq21.1. Arm ratio per GRCh38 - banding schematic.
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Overview
The POU3F4 gene, also known as BRN4, encodes a transcription factor protein that is critical for healthy development. This protein helps control the activity of other genes, particularly those involved in the formation of the central nervous system and the inner ear.
Dysfunction of the POU3F4 protein due to genetic changes can disrupt normal inner ear development, leading to conditions primarily characterised by hearing impairment. Understanding POU3F4's role is key to comprehending the genetic basis of certain types of hereditary hearing loss.
What the gene does
The POU3F4 protein functions as a transcription factor, meaning it regulates the expression of other genes by binding to specific DNA sequences. It is a member of the POU domain gene family, which are known for their roles in cell type determination within the brain and spinal cord during early development.
Specifically within the inner ear, the POU3F4 protein is instrumental in the development of cells within the cochlea, a snail-shaped structure responsible for converting sound waves into electrical nerve impulses that are sent to the brain. This process is fundamental for normal hearing. Proper functioning of the POU3F4 protein ensures the correct formation and operation of the cochlea, supporting sound perception.
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Chromosome location
The POU3F4 gene is located on the X chromosome at position Xq21.1. This genomic location means it is an X-linked gene, which influences its inheritance pattern and how associated conditions are typically passed through families.
Protein structure
The POU3F4 protein is composed of 361 amino acids and contains several distinct regions and domains crucial for its function. It features two Disordered regions, one spanning amino acids 99-131 and another from amino acids 144-192. Key functional domains include the POU-specific domain (amino acids 186-260) and the Homeobox domain (amino acids 278-337), which is responsible for DNA binding. These domains enable the protein to interact with DNA and regulate gene expression.
Key variants
Genetic variations within the POU3F4 gene can range from single nucleotide changes to larger deletions or duplications. Pathogenic variants, which are disease-causing changes, can impair the gene's ability to produce a functional protein, or alter its activity, thereby affecting critical developmental processes, particularly in the inner ear.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.341G>A | p.Trp114Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Rare genetic deafness |
c.607_610del | p.Gln203fs | Pathogenic | ★★☆☆ | Rare genetic deafness |
c.583G>T | p.Glu195Ter | Pathogenic | ★☆☆☆ | Nonsyndromic genetic hearing loss |
c.598C>T | p.Gln200Ter | Pathogenic | ★☆☆☆ | not provided |
c.76C>T | p.Gln26Ter | Pathogenic | ★☆☆☆ | X-linked mixed hearing loss with perilymphatic gusher |
c.893_894del | p.Leu298fs | Pathogenic | ★☆☆☆ | X-linked mixed hearing loss with perilymphatic gusher |
c.922_925dup | p.Ser309fs | Pathogenic | ★☆☆☆ | X-linked mixed hearing loss with perilymphatic gusher |
c.935del | p.Ala312fs | Pathogenic | ★☆☆☆ | X-linked mixed hearing loss with perilymphatic gusher |
c.976T>A | p.Phe326Ile | Pathogenic | ★☆☆☆ | X-linked mixed hearing loss with perilymphatic gusher |
c.991C>T | p.Gln331Ter | Pathogenic | ★☆☆☆ | X-linked mixed hearing loss with perilymphatic gusher |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Pathogenic variants in the POU3F4 gene are known to cause X-linked nonsyndromic hearing loss. This condition involves partial or total hearing impairment that is not accompanied by other signs or symptoms affecting different body systems. The most common form of X-linked nonsyndromic hearing loss linked to this gene is DFNX2.
No disease links recorded for this gene in our reference set.
UK clinical status
The POU3F4 gene is recognised within the UK's NHS Genomic Medicine Service. It is included on the Monogenic hearing loss (R67) Green list in PanelApp, indicating that there is strong evidence for its association with this condition and it is routinely considered in diagnostic testing.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the POU3F4 gene responsible for?
The POU3F4 gene provides instructions for making a protein that acts as a transcription factor. This protein regulates the activity of other genes, particularly those involved in the development of the central nervous system and the cochlea in the inner ear, which is vital for normal hearing.
What health conditions are associated with POU3F4?
Pathogenic variants in the POU3F4 gene are associated with X-linked nonsyndromic hearing loss, specifically a type known as DFNX2. This condition primarily affects hearing without other medical symptoms.
How is POU3F4-related hearing loss inherited?
POU3F4 is located on the X chromosome, meaning POU3F4-related hearing loss follows an X-linked inheritance pattern. This typically means that males are more severely affected than females, as males have only one X chromosome.
References
- Bademci G, Lasisi A, Yariz KO. Novel domain-specific POU3F4 mutations are associated with X-linked deafness: examples from different populations. BMC medical genetics. 2015. PMID: 25928534
- Parzefall T, Shivatzki S, Lenz DR. Cytoplasmic mislocalization of POU3F4 due to novel mutations leads to deafness in humans and mice. Human mutation. 2013. PMID: 23606368
- Song MH, Lee KY, Choi JY. Nonsyndromic X-linked hearing loss. Frontiers in bioscience (Elite edition). 2012. PMID: 22201925
- Lee HK, Song MH, Kang M. Clinical and molecular characterizations of novel POU3F4 mutations reveal that DFN3 is due to null function of POU3F4 protein. Physiological genomics. 2009. PMID: 19671658
- Marlin S, Moizard MP, David A. Phenotype and genotype in females with POU3F4 mutations. Clinical genetics. 2009. PMID: 19930154
- Bitner-Glindzicz M, Turnpenny P, Höglund P. Further mutations in Brain 4 (POU3F4) clarify the phenotype in the X-linked deafness, DFN3. Human molecular genetics. 1995. PMID: 7581392
- de Kok YJ, van der Maarel SM, Bitner-Glindzicz M. Association between X-linked mixed deafness and mutations in the POU domain gene POU3F4. Science (New York, N.Y.). 1995. PMID: 7839145