Aberrant chromosomes uncovered in autistic children

The children in the study had Asperger’s syndrome, infantile autism, ADHD, and Rett’s syndrome. These are so-called autism spectrum disorders that all involve some form of contact disturbance. The cause of these diseases is not known.

“Both heredity and environment play a role. I believe it’s a matter of several genes working together, and if one chromosome is damaged, there may be genes in that chromosome that have been damaged or are missing,” says research Tonnie Johannesson.

It is not known precisely which genes cause the disorders, but the dissertation provides an indication of where these genes might be situated.

“It’s as if we haven’t found the needle in the haystack yet, but now we know what haystack to look in,” says Tonnie Johannesson.

The study shows that two boys with Asperger’s syndrome had nearly identical aberrations in a chromosome. On chromosome 17, both had a break in almost exactly the same place.

“It is remarkable to find such a similarity between two unrelated patients with the same disorder,” says Tonnie Johannesson.

Following in-depth analysis, Tonnie Johannesson managed to find the faulty gene in one of the boys. The study shows that the damaged gene is of importance to the brain, but it is unclear precisely what role it plays in brain development.

Infantile autism is a form of disease that expresses itself during the child’s first year. The dissertation shows that four unrelated boys who have the disorder all had a small extra chromosome. The fifteenth pair consisted of three chromosomes instead of two.

“Genes are presumably the cause of this disorder, but we still don’t know which ones they are,” says Tonnie Johannesson.

In a mildly mentally retarded boy diagnosed with ADHD the chromosomes had changed places with each other. Three of the chromosomes had been switched around, but all the chromosome pieces seemed to be there. On the other hand, a girl with a disease resembling Rett’s syndrome proved to be lacking a piece of a chromosome in the third pair.

Dissertation for the degree of doctor of medicine at the Sahlgrenska Academy, Department of Biomedicine, Section for Clinical Genetics.

Title of dissertation: Structural chromosomal aberrations and neuropsychiatric diseases