|| > 2x risk of dyslexia and poor reading performance
|| increased risk of dyslexia and poor reading performance
|?|| (C;C) (C;T) (T;T) ||28|
] genetic risk for poor reading performance.
Rs2143340, a SNP in the TTRAP gene, is in a region that crops up in several independent studies as likely to associated with dyslexia. The risk allele in the US/UK Caucasian populations studied is (C), and it is indicative of a risk haplotype found in ~18% of the general population but up to ~28% of severely dyslexic individuals. [PMID 15514892]
It is not thought that rs2143340 is a functional SNP; instead, it marks the haplotype known as rs4504469-rs2038137-rs2143340 "1-1-2" since the other two SNPs are the common forms whereas the significant form for rs2143340 is the rare form. The functional effect of this haplotype appears to be on the KIAA0319 gene, in that KIAA0319 gene activity associated with the 1-1-2 risk haplotype is 40% lower than for other haplotypes, and other genes aren't noticeably affected. [PMID 16600991] [PMID 18829873]
] Strong evidence that KIAA0319 on chromosome 6p is a susceptibility gene for developmental dyslexia.
[PMID 16385449] Strong genetic evidence of DCDC2 as a susceptibility gene for dyslexia.
[PMID 17597587] A haplotype spanning KIAA0319 and TTRAP is associated with normal variation in reading and spelling ability.
[PMID 19325871] A common variant associated with dyslexia reduces expression of the KIAA0319 gene.