|http://ghr.nlm.nih.gov/ A service of the U.S. National Library of Medicine®|
The official name of this gene is “gap junction protein, beta 3, 31kDa.”
GJB3 is the gene's official symbol. The GJB3 gene is also known by other names, listed below.
The GJB3 gene provides instructions for making a protein called gap junction beta 3, more commonly known as connexin 31. Connexin 31 is a member of the connexin protein family. Connexin proteins form channels called gap junctions that permit the transport of nutrients, charged atoms (ions), and signaling molecules between neighboring cells.
Connexin 31 is found in several different tissues throughout the body, including the skin, the inner ear, and the nerve that connects the inner ear with the brain (the auditory nerve). Connexin 31 plays a role in the growth and maturation of the outermost layer of skin (the epidermis). The presence of this protein in the inner ear and auditory nerve suggests that it may be involved in hearing. Hearing requires the conversion of sound waves to electrical nerve impulses, which travel along the auditory nerve to the brain. The exact role of connexin 31 in the inner ear and auditory nerve is unclear.
The GJB3 gene belongs to a family of genes called GJ (gap junction proteins (connexins)).
A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genefamilies) in the Handbook.
Researchers have identified a few GJB3 gene mutations in people with a form of nonsyndromic deafness (hearing loss without related signs and symptoms affecting other parts of the body) called DFNA2. DFNA2 deafness is inherited in an autosomal dominant manner, which means that one copy of the GJB3 gene in each cell is altered. A few GJB3 mutations have also been identified in people with autosomal recessive nonsyndromic deafness. This type of inheritance means that two copies of the GJB3 gene in each cell are altered. It is unclear, however, whether GJB3 gene mutations are the direct cause of hearing loss in individuals with either of these types of deafness.
GJB3 gene mutations related to hearing loss alter the sequence of protein building blocks (amino acids) in connexin 31. Some mutations lead to missing amino acids in connexin 31, and other mutations replace one amino acid with an incorrect amino acid. These changes likely alter the 3-dimensional shape or size of connexin 31, which could disrupt the assembly or function of gap junctions. It is unclear how GJB3 gene mutations contribute to hearing loss.
Several GJB3 gene mutations have been identified in people with erythrokeratodermia variabilis (EKV), a skin disorder characterized by areas of abnormally thickened skin and temporarily reddened patches. These mutations replace one of the protein building blocks (amino acids) used to make connexin 31 with an incorrect amino acid. The altered protein probably interferes with the assembly of gap junctions, or it disturbs the normal function of the gap junction by leaving the channel continuously open. It is unclear how GJB3 gene mutations disrupt the growth and maturation of skin cells and cause erythrokeratodermia variabilis.
Cytogenetic Location: 1p34
Molecular Location on chromosome 1: base pairs 35,246,789 to 35,251,966
The GJB3 gene is located on the short (p) arm of chromosome 1 at position 34.
More precisely, the GJB3 gene is located from base pair 35,246,789 to base pair 35,251,966 on chromosome 1.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
You and your healthcare professional may find the following resources about GJB3 helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
acids ; amino acid ; auditory ; auditory nerve ; autosomal ; autosomal dominant ; autosomal recessive ; cell ; channel ; connexin ; epidermis ; gap junctions ; gene ; inheritance ; ions ; protein ; recessive
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.