Genetics and Hearing Loss

Genes contain instructions that tell cells how to grow and work. Many genes are involved with hearing. Genetic hearing loss can be either syndromic or nonsyndromic. Syndromic hearing loss can come from malformations of the ear or other systems. Nonsyndromic hearing loss has no visible abnormalities of the ear or medical problems. About 80% of prelingual deafness is genetic. The most common cause of nonsyndromic hearing loss is a mutation of GJB2. (2)

What are GJB2 and Connexin 26? GJB2 is a gene that contains instructions for a protein called Connexin 26. This protein plays an important role in the function of the cochlea (the organ of hearing). Sometimes, a gene does not form in the expected manner. This is called a mutation. There are many mutations in this gene that can cause hearing loss. About 40% of newborns with a genetic hearing loss with no associated syndrome, have a mutation in the GJB2 gene (1).

What Is Genetic Testing? A genetic test involves looking at a person’s DNA to see if certain mutations are present. DNA samples are obtained from either a blood test or a swab from cheek cells. Once a DNA sample is obtained, doctors can look for mutations. 

Further Reading:

• The U.S. Department of Health and Human Services has a guide that explains about genes and genetic testing at http://www.accessexcellence.org/AE/AEPC/NIH/index.html 
• The Genetic Science Learning Center has some information about basic genetics, genetic conditions and genetic counseling at http://learn.genetics.utah.edu/ 
• The Hereditary Hearing loss Homepage gives an up-to-date overview of the genetics of hereditary hearing loss for researchers and clinicians working in the field.  http://hereditaryhearingloss.org/ 
• For more information on Early Hearing Detection and Intervention, see http://www.cdc.gov/ncbddd/hearingloss/index.html

References:

1. Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities
2. Shearer AE, Hildebrand MS, Smith RJH. Hereditary Hearing Loss and Deafness Overview. 1999 Feb 14 [Updated 2017 Jul 27]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews^® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2019. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1434/