[Frequency of the Connexin26/35delG mutation and its characteristic phenotype in patients with hearing impairment and controls in Northeastern Hungary].
BACKGROUND
Hereditary hearing impairment is a heterogeneous disorder showing different pattern of inheritance and involving a multitude of different genes. Mutations in the GJB2 gene, especially the 35delG mutation, have been established as a major cause of inherited and sporadic non-syndromic deafness in different populations. Mutations in GJB2 gene, encoding gap junction protein (Connexin 26), may be responsible for up to 50% of cases of autosomal recessive non-syndromic hearing impairment and in 15-30% of sporadic cases.


METHODS
The authors analyzed 15 north east Hungarian families and 30 sporadic cases with nonsyndromic hearing impairment for the 35delG mutation.


METHODS
DNA were tested for the common 35delG mutation by a polymerase chain reaction based restriction enzyme assay (BsiYl).


RESULTS
Fifty two patients showing a homozygous 35delG mutation were audiological examined. Ordinarily these patients showed a prelingual, sensorineural, bilateral, symmetric hearing loss without progression. The audiograms were characterized by sloping or flat patterns. The carrier frequency of the 35delG mutation among control group was 5.1%.


CONCLUSIONS
The phenotypic manifestation varied in 30% of all analyzed patients, making genetic counseling extremely difficult. Due to this knowledge mutation analysis of GJB2 cannot distinctly predict the degree of hearing impairment.
Tóth
Tímea
T
Debreceni Egyetem Orvos- és Egészségtudományi Centrum, Altalános Orvostudományi Kar Fül-orr-gégeklinika, Debrecen.
Kupka
Susan
S
Blin
Nicolaus
N
Pfister
Markus
M
Sziklai
István
I
D000328:Adult; D016022:Case-Control Studies; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D004252:DNA Mutational Analysis; D004200:Diseases in Twins / Q000235:genetics; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000453:epidemiology / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D006814:Hungary / Q000453:epidemiology; D015994:Incidence; D008297:Male; D009154:Mutation; D010641:Phenotype; D011237:Predictive Value of Tests; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012720:Severity of Illness Index; D018433:Twin Studies as Topic
D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26