GJB2 and deafness: In the present study, we performed a comprehensive analysis of 6 prominent deafness-related genes, GJB2, GJB3, GJB6, SLC26A4, mtDNA 12S rRNA, and mtDNA tRNAser(UCN), in 284 patients with early-onset, nonsyndromic hearing impairment from unrelated families from two typical Chinese areas, Chifeng City in northern China and Nantong City in southern China, to investigate the molecular etiology in order to provide effective risk assessment and genetic counseling for hearing loss patients and their families in China.