GJB2 and deafness: The c.235delC mutation in the GJB2 gene predominantly occurs in people of East Asian, the incidences of the mutation ranged from 6.7% to 22.5% in several other Chinese deaf cohorts according to previous studies, which were 5.3% and 10.9% in two reported Japanese hearing loss cohorts, 1.5% in a cohort from Mongolia, 5.1% and 6.9% in two cohorts of Korean deafness patients[11,14,24–28].