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Study of candidate genes for dyslexia in Brazilian individuals

Author(s): M.C.C.M. Svidnicki1, C.A. Salgado2, R.F. Lima2, S.M. Ciasca2, R. Secolin3, M.C.A. Pomilio4, P.A. Junqueira4, M.S. Pinto4, M.M. Pereira4 and E.L. Sartorato1

Dyslexia or reading disability (RD) is the most common childhood learning disorder and a significantly heritable trait. Many recent studies have investigated the genetic basis of dyslexia, and several candidate genes have been proposed. Among these, DCDC2 and KIAA0319 have emerged as the strongest candidate genes for dyslexia; however studies have not provided uniformly supportive results. The aim of this study was to assess the contribution of proposed candidate genes to the molecular etiology of dyslexia in a Brazilian sample. Large deletions and duplications in the candidate genes DCDC2, KIAA0319, and ROBO1 were investigated in 51 dyslexic subjects. Furthermore, a family-based association study was performed to investigate whether associations observed in other populations with variants in the DCDC2 and KIAA0319 genes were reproducible in Brazilian dyslexic individuals. Our analysis did not detect any deletions or duplications in the genes studied, and we found no evidence that the allelic variants in the two candidate genes were significantly associated with RD in our sample. Our data do not support a role of the DCDC2/KIAA0319 locus in influencing dyslexia as a categorical trait. Given the genetic complexity of dyslexia, it is plausible that both genes contribute to an increased risk, but the relative influence of these 2 genes on RD varies in different study samples, and/or depends on analytical approaches.