Genetic linkage analysis with dyslexia: Evidence for linkage of spelling disability to chromosome 15

Dyslexia (reading and spelling disability) is one of the most frequently di agnosed disorders in childhood. Twin studies of dyslexia have indicated tha t deficits in spelling are substantially heritable and that the heritabilit y of spelling deficits is higher than the heritability of reading deficits. We conducted a linkage study for spelling disability in seven multiplex fa milies from Germany. Following previously reported linkage findings of comp onents of dyslexia to chromosome 6p21-p22 and 15q21, we genotyped 26 micros atellite markers covering all of chromosome 6, and 13 microsatellite marker s covering all of chromosome 15. While the chromosome 6 data were negative, results from chromosome 15 markers supported a locus on 15q21. The highest two-point LOD score was 1.26 with marker D15S143 at theta = 0. A multipoin t LOD score of 1.78 (p = 0.0042) was achieved with a maximum at D15S132. Th us, our results provide independent support for a dyslexia gene on the long arm of chromosome 15.