Phenotypic variability of patients homozygous for the GJB2 mutation 35delG cannot be explained by the influence of one major modifier gene.
Hereditary hearing loss (HL) is a very heterogeneous trait, with 46 gene identifications for non-syndromic HL. Mutations in GJB2 cause up to half of all cases of severe-to-profound congenital autosomal recessive non-syndromic HL, with 35delG being the most frequent mutation in Caucasians. Although a genotype-phenotype correlation has been established for most GJB2 genotypes, the HL of 35delG homozygous patients is mild to profound. We hypothesise that this phenotypic variability is at least partly caused by the influence of modifier genes. By performing a whole-genome association (WGA) study on 35delG homozygotes, we sought to identify modifier genes. The association study was performed by comparing the genotypes of mild/moderate cases and profound cases. The first analysis included a pooling-based WGA study of a first set of 255 samples by using both the Illumina 550K and Affymetrix 500K chips. This analysis resulted in a ranking of all analysed single-nucleotide polymorphisms (SNPs) according to their P-values. The top 250 most significantly associated SNPs were genotyped individually in the same sample set. All 192 SNPs that still had significant P-values were genotyped in a second independent set of 297 samples for replication. The significant P-values were replicated in nine SNPs, with combined P-values between 3 x 10(-3) and 1 x 10(-4). This study suggests that the phenotypic variability in 35delG homozygous patients cannot be explained by the effect of one major modifier gene. Significantly associated SNPs may reflect a small modifying effect on the phenotype. Increasing the power of the study will be of greatest importance to confirm these results.
Hilgert
Nele
N
Department of Medical Genetics, University of Antwerp, Antwerp, Belgium.
Huentelman
Matthew J
MJ
Thorburn
Ashley Q
AQ
Fransen
Erik
E
Dieltjens
Nele
N
Mueller-Malesinska
Malgorzata
M
Pollak
Agnieszka
A
Skorka
Agata
A
Waligora
Jaroslaw
J
Ploski
Rafal
R
Castorina
Pierangela
P
Primignani
Paola
P
Ambrosetti
Umberto
U
Murgia
Alessandra
A
Orzan
Eva
E
Pandya
Arti
A
Arnos
Kathleen
K
Norris
Virginia
V
Seeman
Pavel
P
Janousek
Petr
P
Feldmann
Delphine
D
Marlin
Sandrine
S
Denoyelle
Françoise
F
Nishimura
Carla J
CJ
Janecke
Andreas
A
Nekahm-Heis
Doris
D
Martini
Alessandro
A
Mennucci
Elena
E
Tóth
Timea
T
Sziklai
Istvan
I
Del Castillo
Ignacio
I
Moreno
Felipe
F
Petersen
Michael B
MB
Iliadou
Vasiliki
V
Tekin
Mustafa
M
Incesulu
Armagan
A
Nowakowska
Ewa
E
Bal
Jerzy
J
Van de Heyning
Paul
P
Roux
Anne-Françoise
AF
Blanchet
Catherine
C
Goizet
Cyril
C
Lancelot
Guenaëlle
G
Fialho
Graça
G
Caria
Helena
H
Liu
Xue Zhong
XZ
Xiaomei
Ouyang
O
Govaerts
Paul
P
Grønskov
Karen
K
Hostmark
Karianne
K
Frei
Klemens
K
Dhooge
Ingeborg
I
Vlaeminck
Stephen
S
Kunstmann
Erdmute
E
Van Laer
Lut
L
Smith
Richard J H
RJ
Van Camp
Guy
G
D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D014644:Genetic Variation; D055106:Genome-Wide Association Study; D034381:Hearing Loss / Q000235:genetics; D006720:Homozygote; D006801:Humans; D009154:Mutation; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide
D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26