title: [Screening for mitochondrial DNA mutation in two pedigrees with nonsyndromic inherited sensorineural hearing loss].
abstract: OBJECTIVE
  To investigate the genetic mechanism of maternal nonsyndromic inherited sensorineural hearing loss(SNHL), to identify the incidence of the 7445(G) mutation in such pedigrees and sporadic patients with SNHL, and to provide the theoretical evidence for the diagnosis of this disease.
  
  
  METHODS
  Blood samples were obtained from 2 pedigrees and 14 sporadic patients with SNHL. DNA was extracted from the isolated leukocytes. The mitochondrial DNA (mtDNA) fragments were amplified by PCR. The 1555(G), 3243(G) and 7445(G) mutation was detected by Alw 26 I, Apa I and Xba I restriction endonuclease digestion respectively. The sequence of 12S rRNA, tRNA(Leu(UUR)) and tRNA(Ser(UCN)) was examined.
  
  
  RESULTS
  Restriction endonuclease digestion analysis showed that 12 individuals from 2 pedigrees carried homoplasmic 7445(G) mutation, which was of maternal inheritance. Six individuals from 2 pedigrees and 14 sporadic patients did not have 7445(G) mutation. All individuals did not have 1555(G) and 3243(G) mutation. The sequence analysis further showed that none of them carried homoplasmic 1555(G) and 3243(G) mutation, 12 individuals had (nt)7445 A--> G substitution in tRNA(Ser(UCN)) gene.
  
  
  CONCLUSIONS
  The incidence of 7445(G) mutation in such pedigrees is higher than that in sporadic patients. Screening for mtDNA 7445(G) mutation combined with 1555(G) examination is of much value to clinical use.
authors.affiliation: Department of Otorhinolaryngology, General Hospital of PLA, Beijing, 100853 P. R. China. hdy301@sohu.com
authors.forename: Weimin
authors.initials: W
authors.lastname: Li
authors.forename: Dongyi
authors.initials: D
authors.lastname: Han
authors.forename: Huijun
authors.initials: H
authors.lastname: Yuan
authors.forename: Youqin
authors.initials: Y
authors.lastname: Wang
authors.forename: Juyang
authors.initials: J
authors.lastname: Cao
authors.forename: Weiyan
authors.initials: W
authors.lastname: Yang
authors.forename: Sichang
authors.initials: S
authors.lastname: Jiang
mesh_terms: D004252:DNA Mutational Analysis / Q000379:methods; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000235:genetics*; D006801:Humans; D008297:Male; D010375:Pedigree; D017354:Point Mutation; D012362:RNA, Transfer, Ser / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D012362:RNA, Transfer, Ser