Genetic link to dyslexia

About five million Germans have serious learning difficulties when it comes to reading and writing. It is frequently the case that several members of the same family are affected. So hereditary disposition seems to play an important role in the occurrence of Dyslexia.

Scientists at the universities of Marburg, W?g and Bonn have been working on this question together with Swedish colleagues from the Karolinska Institute in Stockholm. In examinations of German children with serious reading and writing difficulties they have now succeeded in demonstrating for the first time the contribution of a specific gene. Precisely how it contributes to the disorder remains unclear. It is thought that the genes may affect the migration of nerve cells in the brain as it evolves. The results will be published in the January edition of the American Journal of Human Genetics, but have already been made available online.

For several years child and youth psychologists at the universities of Marburg and Wg searched for families in which at least one child was considered dyslexic. "We then analysed blood samples taken from the families to identify candidate genes - and in the end we found the right one," explains the scientist who headed this part of the study from Marburg, Privatdozent Dr. Gerd Schulte-Ko"rne.

Dyslexia Definition
Developmental reading disorder, also called dyslexia, is a reading disability resulting from the inability to process graphic symbols.

Causes, incidence, and risk factors

Between 2 and 8% of elementary-age children have some degree of reading disability. Developmental reading disorder (DRD) is not caused by vision problems, but rather is a problem involving higher cortical (brain) processing of symbols. Children with DRD may have trouble rhyming and separating the sounds in spoken words. These abilities appear to be critical in the process of learning to read.

A child's initial reading skills are based on word recognition, which involves being able to separate out the sounds in words and associate them with letters and groups of letters. More developed reading skills require the linking of words into a coherent sentence. Because DRD children have difficulty connecting the sounds of language to the letters of words, they may consequently have difficulty understanding sentences.

The gene is located in the region of Chromosome 6, which had already been indicated by scientists from the USA and England in connection with reading and spelling disabilities. But the German-Swedish team has gone further and identified within this region a single gene which, as found among German children, is apparently an important factor in the emergence of . "Known as the DCDC2 gene, it appears to affect the migration of nerve cells in the developing brain," says Professor Dr. Markus No"then from the Life and Brain Centre at Bonn University. Professor No"then and his team are in charge of the molecular work within the project.