GJB2 and hearing loss disorder: Thus we began to collect and test all available nonsyndromic hearing loss patients with only one monoallelic pathogenic mutation in the coding part of GJB2. By sequencing exon 1 and the basal promoter region of the GJB2 gene in 212 Chinese patients with GJB2 monoallelic mutation, we identified four patients carrying the IVS1+1G>A mutation.