title: Two large Spanish pedigrees with nonsyndromic sensorineural deafness and the mtDNA mutation at nt 1555 in the 12s rRNA gene: evidence of heteroplasmy.
abstract: We describe two unrelated Spanish families with isolated sensorineural hearing loss. In both pedigrees, the deafness was transmitted maternally, which suggested a mitochondrial, DNA (mtDNA) defect. Within the same pedigree, some relatives showed aminoglycoside-induced deafness, whereas others were not exposed to aminoglycosides before the onset of hearing loss. Molecular genetic analysis in both families showed the A-to-G transition at nt 1555 (A1555G) in the mitochondrial 12S rRNA gene. In one pedigree, the mutation was homoplasmic; in the other, it was heteroplasmic. To assess the frequency of this mutation, we screened 42 patients of various ethnic backgrounds with isolated sensorineural hearing loss; none harbored the A1555G mutation. This is the first report of heteroplasmy in a family with isolated sensorineural deafness associated with the A1555G mutation.
authors.affiliation: H. Houston Merritt Clinical Research Center for Muscular Dystrophy and Related Diseases, Department of Neurology, Columbia-Presbyterian Medical Center, New York, NY 10032, USA.
authors.forename: M
authors.initials: M
authors.lastname: el-Schahawi
authors.forename: A
authors.initials: A
authors.lastname: López de Munain
authors.forename: A M
authors.initials: AM
authors.lastname: Sarrazin
authors.forename: A L
authors.initials: AL
authors.lastname: Shanske
authors.forename: M
authors.initials: M
authors.lastname: Basirico
authors.forename: S
authors.initials: S
authors.lastname: Shanske
authors.forename: S
authors.initials: S
authors.lastname: DiMauro
mesh_terms: D000595:Amino Acid Sequence; D004272:DNA, Mitochondrial / Q000235:genetics*; D003638:Deafness / Q000235:genetics*; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D008431:Maternal-Fetal Exchange / Q000235:genetics; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D015345:Oligonucleotide Probes; D010375:Pedigree; D011247:Pregnancy; D012335:RNA, Ribosomal / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D015345:Oligonucleotide Probes; D012335:RNA, Ribosomal; C075526:RNA, ribosomal, 12S