Genetics in Solving Dyslexia Puzzles

Developmental dyslexia, or specific learning difficulties, is the most common neurobehavioral disorder affecting school-aged children, with a prevalence rate of 5-17.5%. Family and twin studies have pointed to a genetic component in the etiology of dyslexia. However, dyslexia is a complex disorder at both the genetic and environmental levels, and its nature so far remains unclear. Dyslexia is thought to be a ”complex trait” determined by a number of genes, each with small to moderate effects on the specific phenotype, involving various factors such as heterogeneity, incomplete penetrance, phenocopy, or oligogenic inheritance. Based on combined linkage and association analyses using both qualitative and quantitative phenotypes, multiple regions (DYX1-DYX9) on chromosomes 1, 2, 3, 6, 11, 13, 15 and 18 have been reported likely to contain genes contributing to dyslexia. Most recently four candidate genes (DYX1C1, KIAA0319, DCDC2, ROBO1) have been identified as associated with dyslexia. In this review, we focus on the genetic basis of dyslexia and provide an overview of several of the most susceptible loci on chromosomes and prominent candidate genes currently suspected of conditioning dyslexia.