Connexin 26 mutations and nonsyndromic hearing impairment in northern Finland.
OBJECTIVE
The aims of the present study were to evaluate the role of the gap junction protein beta-2 gene (GJB2), encoding connexin 26 (Cx26), in children with moderate to profound prelingual nonsyndromic sensorineural hearing impairment (HI) and to investigate the carrier frequencies of the GJB2 gene mutations in a control population in Northern Finland.


METHODS
Mutation analysis was performed by direct sequencing and carrier detection by conformation sensitive gel electrophoresis further confirmed by direct sequencing.


RESULTS
Cx26 mutations were found in 15 of 71 (21.1%) (67 families) children with HI. Homozygosity for the mutation 35delG was shown to be the cause of HI in 13 of 15 (86.7%) children. Homozygosity for the M34T genotype was found in one child, and compound heterozygosity for the M34T/V37I genotype was found in another. Five families of those with suspected familial HI (29.4%) and six families out of those with sporadic HI (12.0%) had a homozygous or compound heterozygous mutation. The carrier frequency for the mutation 35delG was 1 of 78 (4 of 313) and that for the M34T was 1 of 26 (12 of 313).


CONCLUSIONS
35delG/35delG genotype was found to be a significant cause of moderate to profound prelingual nonsyndromic sensorineural HI in Northern Finland. M34T/M34T genotype was seen in only one child, but the carrier frequency of the M34T allele was about three times higher than that of the 35delG mutation.
Löppönen
Tuija
T
Department of Clinical Genetics, Oulu University Hospital, Kajaanintie 50, FIN-90220 Oulu, Finland. tuija.lopponen@oulu.fi
Väisänen
Marja-Leena
ML
Luotonen
Mirja
M
Allinen
Minna
M
Uusimaa
Johanna
J
Lindholm
Päivi
P
Mäki-Torkko
Elina
E
Väyrynen
Mirja
M
Löppönen
Heikki
H
Leisti
Jaakko
J
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D005387:Finland; D005787:Gene Frequency; D006319:Hearing Loss, Sensorineural / Q000235:genetics*; D006801:Humans; D008297:Male; D020539:Sequence Analysis, Protein
D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26