Prevalence of the GJB2 mutations and the del(GJB6-D13S1830) mutation in Brazilian patients with deafness V^ ania Belintani Piatto a, * , Eny Maria Goloni Bertollo a,1 , Edi L ucia Sartorato b,2 , Jos  e Victor Maniglia a,3 a Medical School of S~ ao Jos e do Rio Preto (FAMERP), Rua Frei Baltazar, No. 415, Boa Vista, S~ ao Jos e do Rio Preto, S~ ao Paulo 15025-390, Brazil b Molecular Biology Center and Genetics Engineering (CBMEG) of State University of Campinas (UNICAMP), Cidade Universit aria Zeferino Vaz s/no., Bar~ ao Geraldo, Campinos, S~ ao Paulo 13083-970, Brazil Received 27 December 2003; accepted 25 May 2004 Available online 19 July 2004 Abstract Mutations in the GJB2 gene are the most common cause of sensorineural non-syndromic deafness in different populations. One specific mutation, 35delG, has accounted for the majority of the mutations detected in the GJB2 gene in many countries. The aim of this study was to determine the prevalence of GJB2 mutations and the del(GJB6-D13S1830) mutation in non-syndromic deaf Brazilians. The 33 unrelated probands were examined by clinical evaluation to exclude syndromic forms of deafness. Mutation analysis in the GJB2 gene and the testing for the del(GJB6-D13S1830) were performed in both the patients and their family members. The 35delG mutation was found in nine of the probands or in 14 of the mutated alleles. The V37I mutation and the del(GJB6-D13S1830) mutation were also found in two patients, both are compound heterozygote with 35delG mutation. These findings strengthen the importance of genetic diagnosis, providing early treatment, and genetic counseling of deaf patients. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Hearing loss; Molecular analysis; Connexin 26; 35delG mutation, del(GJB6-D13S1830) mutation 1. Introduction Surveys show that more than 70 million people worldwide have hearing loss that affects normal com- munication. In developed countries, the incidence of congenital severe hearing impairment is 1 in 1000 births, half of which can be attributed to genetic factors (Marazita et al., 1993). Genetic heterogeneity and en- vironmental factors have impaired identification of the genes causing deafness until recently (Mustapha et al., 2001). In Brazil, most cases of hearing loss are due to environmental factors, such as congenital infections (mainly rubella), perinatal anoxia and meningitis (Sim~ oes and Maciel-Guerra, 1992). About 70% of cases of hereditary pre-lingual deafness belong to the non-syndromic form and are believed to result from a sensorineural (cochlear) defect. Within the non-syndromic hearing loss category, 75–80% of cases of congenital pre-lingual deafness are inherited in an * Corresponding author. Tel.: +55-17-231-0874; fax: +55-17-222- 6894. E-mail addresses: vabp@bol.com.br, vabp@ig.com.br (V. Belintani Piatto), eny.goloni@famerp.br (E. Maria Goloni Bertollo), sartor@ unicamp.br (E. L ucia Sartorato), diretoriageral@famerp.br (J. Victor Maniglia). 1 Present address: Av. Brigadeiro Faria Lima, No. 5416, Vila S~ ao Pedro, S~ ao Jos e do Rio Preto, SP 15090-000, Brazil. Tel.: +55-17- 2105700. 2 Tel.: +55-19-3788-1147; fax: +55-19-3788-1089. 3 Present address: Rua Ondina, No. 45, Redentora, S~ ao Jos e do Rio Preto, S~ ao Paulo 15015-205, Brazil. Tel.: +55-17-235-3366; fax: +55- 17-222-6894. Abbreviations: AS-PCR, allele-specific polimerase chain reaction; bp, base pairs; Cx26, connexin 26; Cx30, connexin 30; Cx32, connexin 32; DB, decibel; del, deletion; DFNB, prefix to recessive non-syndromic deafness; GJB2, gap junction b2; GJB6, gap junction b6; Kb, kilobases; PCR, polimerase chain reaction 0378-5955/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.heares.2004.05.007 Hearing Research 196 (2004) 87–93 www.elsevier.com/locate/heares