Genetic causes of hearing loss

In the past year, genes involved in the branchio-oto-renal and Treacher-Collins syndromes were cloned. Myosin 7A, a gene previously implicated in Usher syndrome type 1B, was also found to be mutated in nonsyndromic hearing loss. Likewise, linkage studies in Pendred syndrome and Usher syndrome type 1D suggest that allelic mutations can cause syndromic and non-syndromic forms of deafness. In patients with X-linked deafness type 3, a hotspot for deletions was found 900 kb proximal to the causal gene POU3F4. Most importantly, the connexin 26 gene is mutated in approximately 50% of all recessive deafness families, enabling early diagnosis and carrier detection. (C) 1998 Rapid Science Ltd.