A new gene (DYX3) for dyslexia is located on chromosome 2

Developmental dyslexia is a specific reading disability affecting children and adults who otherwise possess normal intelligence, cognitive skills, and adequate schooling. Difficulties in spelling and reading may persist throu gh adult life. Possible localisations of genes for dyslexia have been repor ted on chromosomes 15 (DYX1), 6p21.3-23 (DYX2), and Ip over the last 15 yea rs. Only the localisation to 6p21.3-23 has been clearly confirmed and a gen ome search has not previously been carried out. We have investigated a larg e Norwegian family in which dyslexia is inherited as an autosomal dominant trait. A genome wide search for linkage with an average 20 cM marker densit y was initiated in 36 of the 80 family members. The linkage analysis was pe rformed under three different diagnostic models. Linkage analysis in the fa mily identified a region in 2p15-p16 which cosegregated with dyslexia. Maxi mum lod scores of 3.54, 2.92, and 4.32 for the three different diagnostic m odels were obtained. These results were confirmed by a non-parametric multi point GENEHUNTER analysis in which the most Likely placement of the gene wa s in a 4 cM interval between markers D2S2352 and D2S1337. Localisation of a gene for dyslexia to 2p15-16, together with the confirmed linkage to 6p21. 3-23, constitute strong evidence for genetic heterogeneity in dyslexia. Sin ce no gene for dyslexia has been isolated, little is known about the molecu lar processes involved. The isolation and molecular characterisation of thi s newly reported gene on chromosome 2 (DYX3) and DYX1 will thus provide new and exciting insights into the processes involved in reading and spelling.