J. Appl. Genet. 45(2), 2004, pp. 249-254 Screening for mutations in the GJB3 gene in Brazilian patients with nonsyndromic deafness Fabiana ALEXANDRINO 1 , Camila A. OLIVEIRA 1 , Fernanda C. REIS 1 , Andréa T. MACIEL-GUERRA 2 , Edi L. SARTORATO 1 1 CBMEG/Human Genetics Laboratory and 2 Department of Medical Genetics/FCM, Campinas, SP, Brazil Abstract. Deafness is a complex disorder that is affected by a high number of genes and environmental factors. Recently, enormous progress has been made in nonsyndromic deafness research, with the identification of 90 loci and 33 nuclear and 2 mitochondrial genes involved (http://dnalab-www.uia.ac.be/dnalab/hhh/). Muta- tions in the GJB3 gene, encoding the gap junction protein connexin 31 (Cx31), have been pathogenically linked to erythrokeratodermia variabilis and nonsyndromic autosomal recessive or dominant hereditary hearing impairment. To determine the con- tribution of the GJB3 gene to sporadic deafness, we analysed the GJB3 gene in 67 fami- lies with nonsyndromic hearing impairment. A single coding exon of the GJB3 gene was amplified from genomic DNA and then sequenced. Here we report on three amino acid changes: Y177D (c.529T > G), 49delK (c.1227C > T), and R32W (c.144-146delGAA). The latter substitution has been previously described, but its in- volvement in hearing impairment remains uncertain. We hypothesize that mutations in the GJB3 gene are an infrequent cause of nonsyndromic deafness. Key words: connexin 31, GJB3, gap junctions, hearing impairment, mutations. Introduction Hearing impairment is the most prevalent sensorial deficit in the general popula- tion and its prevalence increases with age (RABIONET et al. 2000). In developed countries, genetic factors are the major cause of hearing loss, accounting for about 60% of cases (COHEN,GORLIN 1995, MORTON 1991). In Brazil, most cases of hearing loss are due to environmental factors, such as congenital infections Received: October 6, 2003. Accepted: February 4, 2004. Corresponding author: E.L. SARTORATO, UNICAMP/CBMEG – Cidade, Universitária Zeferino Vaz, Barno Geraldo, Campinas – Sno Paulo, Zip code: 13083-970, Brazil; e-mail: sartor@unicamp.br