The genetics of developmental dyslexia

Abstract

Reading reflects the complex integration of several cognitive processes and proves more difficult to achieve for a significant proportion of the population. Developmental dyslexia (DD), or specific reading disability, is influenced by genes, a fact that has led several research groups to attempt to identify susceptibility genes through the sequential analysis of genetic linkage and association. Strong evidence has now emerged for the presence of genes influencing DD at several chromosomal loci and for at least one of these, there is evidence implicating specific genes. In this review, we present the evidence for a genetic contribution to DD and its component processes and review the current status of molecular genetic research aimed at identifying susceptibility genes for this common, complex disorder.

Investigation of interaction between DCDC2 and KIAA0319 in a large German dyslexia sample

“…This region harbours two independent gene clusters in close proximity to one another, namely VMP/DCDC2/ KAAG1 and KIAA0319/TTRAP/THEM2. Both regions have received support from different independent samples (Cope et al 2005;Deffenbacher et al 2004;Francks et al 2004;Meng et al 2005;Schumacher et al 2006) and it has been concluded that of the candidate genes discussed to date, the evidence for DCDC2 and KIAA0319 is the most convincing (Fisher Francks 2006;McGrath et al 2006;Schumacher et al 2007;Williams O'Donovan 2006). Their involvement in the development of dyslexia has been further strengthened by functional analyses which showed that inhibition of each of the two genes, DCDC2 and KIAA0319, leads to poorer neuronal migration in the neocortex of fetal rats through RNA interference methods (Meng et al 2005;Paracchini et al 2006).…”

Further evidence that the KIAA0319 gene confers susceptibility to developmental dyslexia

“…1 The disorder is characterized by an impairment of reading performance despite adequate motivational, educational and intellectual opportunities. Although the pathophysiology of DD is unknown, there is strong evidence that genes make a substantial contribution to individual variation in risk of DD, with twin studies reporting heritability estimates of up to 0.71.…”

“…Although the pathophysiology of DD is unknown, there is strong evidence that genes make a substantial contribution to individual variation in risk of DD, with twin studies reporting heritability estimates of up to 0.71. [1][2][3][4][5][6][7][8] Linkage studies have identified several genomic regions that may harbor susceptibility quantitative trait loci (QTL) for DD, and the most consistently replicated of these is DYX2, which lies on chromosome 6p22.2. 1,[9][10][11][12][13][14][15][16] A number of association studies have now been performed attempting to identify the DYX2 susceptibility locus.…”

Colorado longitudinal twin study of reading disability

“…For example, results obtained from recent studies have provided compelling evidence regarding their genetic and environmental etiologies (e.g., Fisher & DeFries, 2002;Schumacher et al, 2007;Williams & O'Donovan, 2006), subtypes or dimensions (e.g., Bailey, Manis, Pedersen & Seidenberg, 2004;Griffiths & Snowling, 2002;Olson, Datta, Gayán & DeFries, 1999;Vukovic & Siegel, 2006), gender differences (e.g., Harlaar, Spinath, Dale & Plomin, 2005;Rutter et al, 2004;Wadsworth & DeFries, 2005), and comorbidity with other conditions such as attention-deficit/hyperactivity disorder (ADHD) (e.g., Gayán et al, 2005;McGee, Prior, Williams, Smart & Sanson, 2002;Stevenson et al, 2005;Willcutt et al, 2002Willcutt et al, , 2003 and antisocial behavior (e.g., Trzesniewski, Moffitt, Caspi, Taylor & Maughan, 2006;Willcutt & Pennington, 2000). In addition, recent longitudinal studies have addressed the stability of RD and rates of change for disabled vs nondisabled readers (e.g., Badian, 1999;Bast & Reitsma, 1998;Raskind et al, 1998;Raskind, Higgins, Goldberg & Herman, 1999;Shaywitz et al, 2003).…”