[Diagnostic methods and clinic application for mtDNA A1555G and GJB2 and SLC26A4 genes in deaf patients]

To establish the method of clinic genetic testing for common deaf genes such as mtDNA nt1555, GJB2 gene and SLC26A4 (Pendrin's syndrome gene, PDS) gene.

Three hundred and sixty seven sporadic patients with hearing loss from out-patient department of General Hospital of Chinese People's Liberation Army, 60 patients with history of maternal inherited hearing loss from 27 family, 20 congenital deaf patients from special educational school for deaf and dumb, 3 deaf patients with enlarged vestibular aqueduct (EVA) confirmed by CT scan, 50 control individuals with normal bone conductive hearing were analyzed. The genetic testing kit for mtDNA A1555G mutation was used to detect mtDNA A1555G mutation. The whole gene sequencing were accomplished in 20 congenital deaf patients. In 3 patients with EVA, fragments covering all exons of PDS gene were analyzed by denatured high productive liquid chromatogram and special exons were sequenced when DHPLC showed abnormal wave patterns of amplicons covering these exons.

Fifty nine patients from 26 family and 5 sporadic patients were found to carry mtDNA A1555G mutation. Among 20 congenital deaf patients, 2 cases were found to have homozygous GJB2 235 del C mutation, 1 case had compound 235del C and 299-300 del AT mutation. Other 2 cases carried heterozygous 109 A-G mutation. Among 3 patients with EVA, 1 case was found to have heterozygous PDS G316X mutation and other 2 cases had homozygous 919-2 A-G mutation. CONCLUSIONS Genetic testing for deafness is feasible procedure with remarkable clinic significance.