Molecular Pathogenesis Study For An Extensive Nonsyndomic Deafness Family Associated With A1555G Mutation

Following establishment of immortal lymphoblastoid cell lines for the Chinese extensive family with nonsyndromic deafness in Huaiyin, Jiangsu Province, the whole mitochondrial genome and two putative nuclear modifier genes were PCR amplified and directly sequenced, and the chromosomal region around marker D8S277, a promising modifier locus on 8p23.1, was fine-mapped, in order to identify whether other variants in the mitochondrial DNA, mutation(s) in Connexion 26 and MTO1, or D8S277, would contribute to the pathophysiological pathway in this Chinese deafness family associated A1555G mutation.I. Based on the clinical characterization, venous blood samples were obtained from 122 family members (including 85 matrilineal relatives, 11 patrilineal relatives and 26 spouse controls ) with informed consent, then 115 immortal lymphoblastoid cell lines were transformed using EB virus mediated by cyclosporin A.II. Clinical characterization showed that 56/85 maternal relatives, in this family, experienced hearing loss, whose severity and age-onset varied distinctly. However, their hearing loss shared some common features, being bilateral, sensorineural, and symmetric. And the pattern of inheritance in this family strongly indicates that the mitochondrial DNA mutation may be the main factor of deafness in this family, and that the nuclear modifier gene(s) may have involved in the development of deafness, which is in an irregular autosomal dominant model.III. PCR-RFLP (PCR-restriction fragment length polymorphism, PCR-RFLP) was used to screen both the nt1555 and the nt7445 of the mitochondrial DNA from 26 matrilineal members in the nuclear family; subsequently, the whole mitochondrial genomes from two matrilineal members (one with severe hearing loss, the other with normal hearing), 12S rRNA genes and tRNASer(UCN) from...