Chromosome 6p influences on different dyslexia-related cognitive processes: further confirmation.

In this study, which is a continuation and an extension of an earlier study, we enrolled two new families (N=31) and recruited more individuals from the previously ascertained families (N=56). The eight multiplex families (N=171) presented in this study were ascertained from a sample of adult probands whose childhood reading history is well documented through archival information. Six phenotypes were constructed to span a range of dyslexia-related cognitive processes. These phenotypes were (1) phonemic awareness (of spoken words); (2) phonological decoding (of printed nonwords); (3) rapid automatized naming (of colored squares or object drawings); (4) single-word reading (orally, of printed real words); (5) vocabulary; and (6) spelling (of dictated words). In addition, the diagnosis of lifelong dyslexia was established by clinical means. Genotyping was done with nine highly polymorphic markers from the 6p22.3-6p21.3 region. The results of two- and multipoint identity-by-descent and identity-by-state analyses supported the importance of a putative locus in the D6S464-D6S273 region for a number of dyslexia-related cognitive deficits.