GJB2 and Hearing impairment: For there is higher frequency of single heterozygous GJB2 mutation detected in the deaf population than in the normal population in this study, the further more extensive study of sequence change in GJB2 Exon1 or promoter area and 3'-UTR, fragment deletion neighboring GJB2 ORF region and digenic inheritance with other genes are already considered in this large Chinese deaf cohort for elucidating complex pathogenesis of GJB2 gene to hearing impairment.