GJB1 and hereditary disease: 7 Mutations in the 3′ UTR region are a rare cause of hereditary diseases overall; however, as this region often contains mRNA regulatory elements, mutations in the 3′ UTR may affect normal translation.8 In this study, we sought to determine the frequency and phenotype of CMTX1 due to mutations in the 5′ and 3′ UTR noncoding regions of GJB1.