Two translocations of chromosome 15q associated with dyslexia

Developmental dyslexia is characterised by difficulties in learning to read . As reading is a complex cognitive process, multiple genes are expected to contribute to the pathogenesis of dyslexia. The genetics of dyslexia has b een a target of molecular studies during recent years, but so far no genes have been identified. However, a locus for dyslexia on chromosome 15q21 (DY X1) has been established in previous Linkage studies. We have identified tw o families with balanced translocations involving the 15q21-q22 region. In one family, the translocation segregates with specific dyslexia in three fa mily members. In the other family, the translocation is associated with dys lexia in one family member. We have performed fluorescence in situ hybridis ation (FISH) studies to refine the position of the putative dyslexia locus further. Our results indicate that both translocation breakpoints on 15q ma p within an interval of approximately 6-8 Mb between markers D15S143 and D1 5S1029, further supporting the presence of a locus for specific dyslexia on 15q21.