Analysis Of Deafness Gene Screening In Nonsyndromic Hearing Impairment Patients In Cangzhou Of Hebei Province

Deafness is one of the most common reasons of dysphonia or dumbness.In 2006,the second China national sample survey on disability revealed that27800000 people are hearing disability,and 1270000 people have speech disorders.It accounts for 27% of the total disabled nationwide,ranking the first place of various disabilities.Congenital deafness is one of the most common birth defects.It is estimated that in children who are less than 7 years of age,there are 30000 new cases with hearing impairment each year.If pooled with children suffering from late onset deafness(post lingual deafness)and ototoxic drug-induced deafness,the annual increase in new hearing impaired children is much bigger.With great progress in etiology study after the completion of human genome project,it is speculated that 2/3 congenital deafness people are associated genomic abnormalities.Eighty percent of deaf patients are free from other systematic symptoms,and are categorized as nonsyndromic hearing impairment(NSHI).Hereditary hearing impairment is related to multiple genes.In China,GJB2,GJB3,SLC26A4,mt DNA and12 SrRNA are the main responsible genes for congenital deafness.As the carrier rate of gene mutation is high,it is likely to increase the deafness at birth.The genetic screening has important significance in reducing local area of the birth rate of children with hearing impairment,and in guiding mating in hereditary hearing loss population.Objectives: To investigate the deafness gene mutations of nonsyndromic hearing impairment NSHI in Cangzhou of Hebei Province.Methods: The etiologic survey,the molecular genetic analysis and hearing loss evaluation of common genes responsible for deafness were performed in 358 hearing impairment patients from the special education school and hearing diagnosis centre in Cangzhou of Hebei Province.Theblood samples of all patients were taken for the extraction of DNA which was amplified by PCR.The common mutational hot spots of GJB2,SLC26A4 mitochondrial DNA 12 SrRNA and GJB3 were examined.Results: Deafness-related gene mutations were detected in 70 out of 358 NSHL patients,accounting for 19.5% of the total.Deafness-related gene detection results demonstrated that there were different kinds of genotypes in this group of patients.There were 39(10.89%)cases of GJB2 gene mutation,including 18 cases of GJB2 235 del C homozygous mutation,9 cases of235 delC heterozygous mutation,3 cases of GJB2 299-300 del AT homozygous mutation,and 4 cases compound heterozygous mutations.There were 28(7.82%)cases of SLC26A4 gene mutation,including 20 cases of SLC26A4IVS7 2A>G heterozygous mutation,4 cases of compound heterozygous mutation and 4 cases of SLC26A4 IVS7 2A>G homozygous mutation.The other 2(0.54%)cases exhibited GJB3 538C>T heterozygous mutation and the rest 1(0.27%)case showed 12 SrRNA c.1 555A>G gene mutation.Conclusions: The incidence of hereditary deafness is high in Cangzhou.Molecular genetic screening for these mutations is an effective method to prevent the deafness and to evaluate the prognosis of hearing loss.