Discovery of a Major Cause of Genetic Deafness in East and South Asians
Background: Genetic abnormalities cause about 50% of severe childhood hearing loss, with 80 to 85% caused by autosomal recessive mutations. An autosomal recessive mutation causes hearing loss when each parent passes down an abnormal copy of the gene. The majority of autosomal recessive genetic, or hereditary, deafness is non-syndromic (not associated with any other problem). Further, approximately 10% of autosomal recessive hereditary deafness is caused by mutations in SLC26A4 (formerly known as PDS ), the Pendred Syndrome Gene. Pendred Syndrome is characterized by varying degrees of congenital deafness and thyroid goiter. Pendrin, the protein produced by SLC26A4, is found in the thyroid gland, kidney, and inner ear. Scientists have discovered more than 50 different deafness-causing SLC26A4 mutations.
Advance: The prevalence of genetic deafness can also vary according to the ethnic background. For instance, recessive mutations of SLC26A4 are a common cause of Pendred syndrome and non-syndromic deafness in western populations. However, since not much is known about the frequency of SLC26A4 mutations in Eastern populations, NIDCD-supported scientists have begun to investigate the frequency of SLC26A4 mutations in southern and eastern Asia, a region which comprises nearly one-half of the world ’s population. The scientists have discovered nine different SLC26A4 mutations, including five new mutations never seen before in any population and four already identified but rarely observed outside of East Asia. In addition, each ethnic group within East and South Asia had its own unique SLC26A4 mutations. In some groups, such as in Koreans, SLC26A4 mutations are the most common known cause of deafness.
Implications: These results suggest that the frequency of deafness caused by SLC26A4 mutations is relatively common and constant among all global populations. Thus, ethnic background is quite important and it should be noted when genetic testing is performed, since different mutations in a spectrum of genes are more likely to cause deafness in a given population.
Read more about the research of NIDCD scientist Dr. Andrew Griffith
Park HJ, Shaukat S, Liu XZ, Hahn SH, Naz S, Ghosh M, Kim HN, Moon SK, Abe S, Tukamoto K, Riazuddin S, Kabra M, Erdenetungalag R, Radnaabazar J, Khan S, Pandya A, Usami SI, Nance WE, Wilcox ER, Riazuddin S, Griffith AJ. Origins and Frequencies of SLC26A4 (PDS ) Mutations in East and South Asians: Global Implications for the Epidemiology of Deafness. J Med Genet 40:242-248, 2003.