RESUMO
Mutations in the SLC26A4 gene encoding pendrin, an anion transporter, are responsible for non-syndromic hearing loss (HL) (DFNB4) and Pendred syndrome (PS). PS is a genetic disorder that causes early HL and affects the thyroid gland. Here, we report eight Tunisian families affected with profound HL. Clinical investigations revealed goiter in few patients. Genotyping using microsatellite makers showed linkage to SLC26A4, and missense mutations p.L445W and p.M147T were identified by sequencing and polymerase chain reaction-restriction fragment length polymorphism. The p.L445W mutation segregated in seven families and haplotype analysis suggested its founder effect. In order to understand the molecular pathogenic mechanisms of p.L445W and p.M147T mutations, SLC26A4 wild-type and mutant cDNA constructs were transiently expressed in COS7 cells and several human cell lines including Thyroid 8305C cells. Reverse transcription-PCR, western blot and immunofluorescence demonstrated that these two mutations abolished complex glycosylation of pendrin and prevented its targeting to the plasma membrane.
Assuntos
Efeito Fundador , Proteínas de Membrana Transportadoras/genética , Mutação de Sentido Incorreto , Animais , Linhagem Celular , DNA Complementar , Família , Ligação Genética , Genótipo , Glicosilação , Haplótipos , Perda Auditiva/genética , Humanos , Proteínas de Membrana/genética , Transportadores de Sulfato , Transfecção , TunísiaRESUMO
Hereditary hearing impairment is the most genetically heterogeneous trait known in humans. So far, 50 published autosomal recessive non-syndromic hearing impairment (ARNSHI) loci have been mapped, and 23 ARNSHI genes have been identified. Here, we report the mapping of a novel ARNSHI locus, DFNB63, to chromosome 11q13.3-q13.4 in a large consanguineous Tunisian family. A maximum LOD score of 5.33 was obtained with microsatellite markers D11S916 and D11S4207. Haplotype analysis defined a 5.55 Mb critical region between microsatellite markers D11S4136 and D11S4081. DFNB63 represents the sixth ARNSHI locus mapped to chromosome 11. We positionally excluded MYO7A from being the DFNB63-causative gene. In addition, the screening of two candidate genes, SHANK2 and KCNE3, failed to reveal any disease-causing mutations.
