Mitochondrial tRNA mutations associated with deafness

Mitochondrial tRNA mutations are one of the important causes of both syndromic and non–syndromic deafness. Of those, syndromic deafness–associated tRNA mutations such as tRNALeu(UUR) 3243A>G are often present in heteroplasmy, while non–syndromic deafness–associated tRNA mutations including tRNASer(UCN) 7445A>G are often in homplasmy or in high levels of heteroplasmy. These tRNA mutations are the primary mutations leading to hearing loss. However, other tRNA mutations such as tRNAThr 15927G>A and tRNASer(UCN) 7444G>A may act in synergy with the primary mitochondrial DNA mutations, modulating the phenotypic manifestation of the primary mitochondrial DNA mutations. Theses tRNA mutations cause structural and functional alteration. A failure in tRNA metabolism caused by these tRNA mutations impaired mitochondrial translation and respiration, thereby causing mitochondr ial dysfunctions responsible for deafness. These data offer valuable information for the early diagnosis, management and treatment of maternally inherited deafness.