Prevalence of c.35delG and p.M34T mutations in the GJB2 gene in Estonia.
OBJECTIVE
The purpose of this study was to determine the prevalence of c.35delG and p.M34T mutations in the GJB2 gene among children with early onset hearing loss and within a general population of Estonia.


METHODS
Using an arrayed primer extension assay, we screened 233 probands with early childhood onset hearing loss for 107 different mutations in the GJB2 gene. We then looked for the two most common mutations, c.35delG and p.M34T, in a population of 998 consecutively born Estonian neonates to determine the frequency of these mutations in the general population.


RESULTS
In 115 (49%) of the patients with early onset hearing loss, we found a mutation in at least one allele of the GJB2 gene. Seventy-three (31%) were homozygous for the c.35delG mutation, seven (3%) were homozygous for the p.M34T mutation, and five (2%) had c35delG/p.M34T compound heterozygosity. Other six identified mutations in GJB2 gene occurred rarely. Among the 998 anonymous newborn samples, we detected 45 who were heterozygous for c.35delG, 2 individuals homozygous for c.35delG, and 58 who were heterozygous for p.M34T. Additionally, we detected two c.35delG/p.M34T compound heterozygotes.


CONCLUSIONS
The most common GJB2 gene mutations in Estonian children with early onset hearing loss were c.35delG and p.M34T, with c.35delG accounting for 75% of GJB2 alleles. The carrier frequency for c.35delG and p.M34T in a general population of Estonia was 1 in 22 and 1 in 17, respectively, and was higher than in most other countries.
Teek
Rita
R
Department of Genetics, United Laboratories, Tartu University Hospital, Tartu, Estonia.
Kruustük
Katrin
K
Zordania
Riina
R
Joost
Kairit
K
Reimand
Tiia
T
Möls
Tõnu
T
Oitmaa
Eneli
E
Kahre
Tiina
T
Tõnisson
Neeme
N
Ounap
Katrin
K
D000293:Adolescent; D017668:Age of Onset; D002648:Child; D002675:Child, Preschool; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D004957:Estonia; D005060:Europe; D005828:Genetics, Population; D005838:Genotype; D006319:Hearing Loss, Sensorineural / Q000235:genetics*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D009154:Mutation; D017384:Sequence Deletion
D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26