Identification of candidate genes for dyslexia susceptibility on chromosome 18.
BACKGROUND
Six independent studies have identified linkage to chromosome 18 for developmental dyslexia or general reading ability. Until now, no candidate genes have been identified to explain this linkage. Here, we set out to identify the gene(s) conferring susceptibility by a two stage strategy of linkage and association analysis.


RESULTS
Linkage analysis: 264 UK families and 155 US families each containing at least one child diagnosed with dyslexia were genotyped with a dense set of microsatellite markers on chromosome 18. Association analysis: Using a discovery sample of 187 UK families, nearly 3000 SNPs were genotyped across the chromosome 18 dyslexia susceptibility candidate region. Following association analysis, the top ranking SNPs were then genotyped in the remaining samples. The linkage analysis revealed a broad signal that spans approximately 40 Mb from 18p11.2 to 18q12.2. Following the association analysis and subsequent replication attempts, we observed consistent association with the same SNPs in three genes; melanocortin 5 receptor (MC5R), dymeclin (DYM) and neural precursor cell expressed, developmentally down-regulated 4-like (NEDD4L).


CONCLUSIONS
Along with already published biological evidence, MC5R, DYM and NEDD4L make attractive candidates for dyslexia susceptibility genes. However, further replication and functional studies are still required.
Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom.
Thomas S
TS
Scerri
Silvia
S
Paracchini
Andrew
A
Morris
I Laurence
IL
MacPhie
Joel
J
Talcott
John
J
Stein
Shelley D
SD
Smith
Bruce F
BF
Pennington
Richard K
RK
Olson
John C
JC
DeFries
Anthony P
AP
Monaco
Alex J
AJ
Richardson
D002887:Chromosomes, Human, Pair 18; D004410:Dyslexia / Q000235:genetics*; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease; D006801:Humans; D020641:Polymorphism, Single Nucleotide