Table 3

 Summary of association findings in dyslexia

GeneStudy designSample characteristics, countryGenotyped variantsResultsReferences
DCDC2, doublecortin domain containing protein 2gene; SNP, single-nucleotide polymorphism.
*Some cases were extracted from the same families and are related.
†Including the two significantly associated SNPs reported by Taipale et al.83
‡Cases and controls were analysed using a DNA pooling approach.
§Samples represent subsamples selected for severity of the phenotype.
¶Individual genotyping of markers that were associated in the pooled samples (most of the cases and controls are identical).
DYX1C1 Case–control55 cases* vs 113 controls, Finland8 SNPsSignificant association at the single-marker and haplotype levelTaipale et al83
Case–control54 cases* vs 82 controls, Finland8 SNPs†Significant association at the single-marker level
Family based148 nuclear families, Canada6 SNPs†Significant association at the single-marker and haplotype level, association in the opposite direction compared to Taipale et al83Wigg et al84
Family based264 nuclear families, UK8 SNPs†Significant association at the single-marker level, association in the opposite direction compared to Taipale et al83Scerri et al85
Family based150 nuclear families, USA2 SNPs†No associationMeng et al86
Family based158 nuclear families, Italy3 SNPs†No associationMarino et al87
Case–control57 cases vs 96 controls, Italy3 SNPs†No associationBellini et al88
Family based247 nuclear families, UK3 SNPs†No associationCope et al89
DCDC2 Family based114 nuclear families, USA31 SNPs within 680 kb (including VMP, DCDC2, KAAG1, KIAA0319, TTRAP and THEM2)Strongest association at the single-marker and haplotype level within the VMP/DCDC2/KAAG1 locusDeffenbacher et al72
Family based153 nuclear families, USA147 SNPs within 1.5 Mb (including VMP, DCDC2, KAAG1, KIAA0319, TTRAP and THEM2)Strongest association at the single-marker and haplotype level within DCDC2Meng et al74
Case–control240 cases vs 312 controls, UK‡137 SNPs within VMP, DCDC2, KAAG1, KIAA0319, TTRAP and THEM2No association within the VMP/DCDC2/KAAG1locusCope et al71
Family based137 triads, Germany18 SNPs and 4 STRs within the VMP/DCDC2/KAAG1-locusStrongest association at the single-marker and haplotype level within DCDC2, strongest results with severity selectionSchumacher et al75
Family based239 triads, Germany2 SNPs, 1 STR within DCDC2Significant association at the haplotype level, strongest results with severity selection
KIAA0319 Family based114 nuclear families, USA31 SNPs within 680 kb (including VMP, DCDC2, KAAG1, KIAA0319, TTRAP and THEM2)Significant association at the single-marker and haplotype level within the KIAA0319/TTRAP/THEM2 locusDeffenbacher et al72
Family based42 nuclear families, UK§31 SNPs within 680 kb (including the KIAA0319/TTRAP/THEM2 locus)Strongest association at the single-marker and haplotype level within KIAA0319 and TTRAPFrancks et al73
Family based84 nuclear families, UK§20 SNPs within KIAA0319 and TTRAPSignificant association at the single-marker and haplotype level
Family based124 nuclear families, USA§21 SNPs within KIAA0319 and TTRAPSignificant association at the single-marker and haplotype levelCope et al71
Case– control240 cases vs 312 controls, UK‡¶137 SNPs within VMP, DCDC2, KAAG1, KIAA0319, TTRAP and THEM2Strongest association at the single-marker and haplotype level within KIAA0319
Case–control223 cases vs 273 controls, UK‡¶10 SNPs within the KIAA0319/TTRAP/THEM2-locusStrongest association at the single-marker and haplotype level within KIAA0319Schumacher et al75
Family based376 triads, Germany10 SNPs within the KIAA0319/TTRAP/THEM2 locusNominal significant association at the single-marker level for 1 variant within KIAA0319 in the most severely affected subsampleHarold et al90
Family based126 nuclear families, UK§16 SNPs within DCDC2, KIAA0319 and flanking regionStrongest association at the single-marker level within 20 kB in intron1 of KIAA0319
Case–control350 cases vs 273 controls, UK28 SNPs and 1 STR within DCDC2, KIAA0319 and flanking regionsEvidence for gene–gene interaction betweenKIAA0319 and DCDC2
Case–control419 cases vs 273 controls, UK4 SNPs and 1 STR within DCDC2 and 5 SNPS within KIAA0319