title: Searching for digenic inheritance in deaf Brazilian individuals using the multiplex ligation-dependent probe amplification technique.
abstract: Mutations in the genes coding for connexin 26 (Cx26), connexin 30 (Cx30), and connexin 31 (Cx31) are the main cause of autosomal recessive nonsyndromic sensorineural hearing loss (AR-NSNHL). The 35delG mutation is the most frequent in the majority of Caucasian populations and may account for up to 70% of all GJB2 mutations. As a large number of affected individuals (10%-40%) with GJB2 mutations carry only one mutant allele, it has been postulated that the presence of additional mutations in the GJB6 gene (Cx30) explains the deafness condition found in these patients. In the present study, we screened the c.35delG mutation in ~600 unrelated Brazilian patients, with moderate to profound AR-NSNHL. Other point mutations in the coding region of the GJB2 gene were screened by sequencing analysis as well as the IVS 1+1 G>A splice site mutation in the same gene. Digenic mutations including large deletions and duplications were investigated in the Cx26, 30, and 31 genes in monoallelic individuals for mutations in the GJB2 gene. Large deletions and duplications were assessed by multiplex ligation-dependent probe amplification. We found 46 patients with mutations in only one GJB2 allele. Different pathogenic mutations associated with c.35delG were found in 13 patients. Two patients were identified with digenic heterozygous mutations. Our findings contributed to more accurate diagnosis and more appropriate genetic counseling in 28% of patients studied (13/46).
authors: Centro de Biologia Molecular e Engenharia Genética, Universidade Estadual de Campinas, Cidade Universitária Zeferino Vaz s/n, Barão Geraldo, Campinas, Brazil.
authors: Sueli M
authors: SM
authors: da Silva-Costa
authors: Fábio Tadeu Arrojo
authors: FT
authors: Martins
authors: Tânia
authors: T
authors: Pereira
authors: Mariza C A
authors: MC
authors: Pomilio
authors: Antonia Paula
authors: AP
authors: Marques-de-Faria
authors: Edi Lúcia
authors: EL
authors: Sartorato
mesh_terms: D001938:Brazil; D000072259:Connexin 26; D000075302:Connexin 30; D017630:Connexins / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D020440:Gene Duplication; D005817:Genetic Counseling; D020022:Genetic Predisposition to Disease; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods; D015335:Molecular Probes; D017354:Point Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D044465:White People
chemical_list: D000075302:Connexin 30; D017630:Connexins; C000607042:GJB2 protein, human; C491020:GJB6 protein, human; D015335:Molecular Probes; D000072259:Connexin 26; C068044:GJB3 protein, human