Mutation in Actin Domain Linked to Hearing Loss

Researchers have found that a mutation occurring in the DFNA 20 gene, which is known to be involved in determining the structure of the inner ear, may be responsible for a type of inherited, age-related hearing loss (presbycusis).

Investigators at Michigan State University (East Lansing, USA) performed gene analysis on four families whose members displayed the onset of hearing-related communication problems as they neared the age of 30. Writing in the November 2003 issue of the American Journal of Human Genetics, they stated that sequence analysis of the gamma-actin gene (ACTG1) showed missense mutations in highly conserved actin domains in all four families. These mutations altered amino acids that are normally conserved in all actins, from protozoa to mammals, and were not found in more than 100 chromosomes from normal-hearing individuals.

Much of the specialized ultrastructural organization of the cells in the cochlea is based on the actin cytoskeleton. The mutations in various binding domains of actin probably mildly interfere with bundling, gelation, polymerization, or myosin movement, and may cause hearing loss by hindering the repair or stability of cochlear cell structures damaged by noise or aging.
"Knowing what the gene is means that you can maybe move toward preventing hearing loss or, possibly, curing it,” said senior author Dr. Karen Friderici, associate professor of microbiology and molecular genetics at Michigan State University.



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