title: Genetic analysis of the connexin-26 M34T variant: identification of genotype M34T/M34T segregating with mild-moderate non-syndromic sensorineural hearing loss.
abstract: Mutations in the human gap junction beta-2 gene (GJB2) that encodes connexin-26 have been shown to cause non-syndromic sensorineural hearing loss (NSSNHL) at the DFNB1 locus on 13q11. Functional and genetic data regarding the disease causing potential of one particular GJB2 sequence variant, 101 T-->C (M34T), have proven contradictory. In this study, we found the prevalence of the M34T allele in a cohort of white sib pairs and sporadic cases with NSSNHL from the United Kingdom and Ireland to be 3.179% of chromosomes screened. Significantly, we identified the first M34T/M34T genotype cosegregating in a single family with mid to high frequency NSSNHL. Screening a control population of 630 subjects we identified 25 M34T heterozygotes; however, no M34T homozygotes were detected. Surprisingly, the majority of M34T alleles (88%) were in cis with a 10 bp deletion in the 5' non-coding sequence. This non-coding deletion was also homozygous in the homozygous M34T subjects. Microsatellite analysis of flanking loci in M34T heterozygotes and controls does not define an extensive ancestral haplotype but preliminary data suggest two common alleles in subjects with the M34T allele. In summary, we provide data that support M34T acting as a recessive GJB2 allele associated with mild-moderate prelingual hearing impairment.
authors.affiliation: Molecular Medicine Unit, St James's University Hospital, Leeds LS9 7TF, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Houseman
authors.forename: L A
authors.initials: LA
authors.lastname: Ellis
authors.forename: A
authors.initials: A
authors.lastname: Pagnamenta
authors.forename: W L
authors.initials: WL
authors.lastname: Di
authors.forename: S
authors.initials: S
authors.lastname: Rickard
authors.forename: A H
authors.initials: AH
authors.lastname: Osborn
authors.forename: H H
authors.initials: HH
authors.lastname: Dahl
authors.forename: G R
authors.initials: GR
authors.lastname: Taylor
authors.forename: M
authors.initials: M
authors.lastname: Bitner-Glindzicz
authors.forename: W
authors.initials: W
authors.lastname: Reardon
authors.forename: R F
authors.initials: RF
authors.lastname: Mueller
authors.forename: D P
authors.initials: DP
authors.lastname: Kelsell
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution; D001483:Base Sequence; D020090:Chromosome Segregation; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004252:DNA Mutational Analysis; D005192:Family Health; D005260:Female; D005787:Gene Frequency; D005820:Genetic Testing; D014644:Genetic Variation; D005838:Genotype; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis / Q000235:genetics*; D006720:Homozygote; D006801:Humans; D008297:Male; D009154:Mutation; D010375:Pedigree; D017384:Sequence Deletion
chemical_list: D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26; D004247:DNA