1 December 1999
The Autism Gene?
by Kate Melville
In an exciting new development researchers from the University of North Carolina at Chapel Hill have reported evidence for a possible gene on chromosome 13 that causes autism.
Autism is a severe neuro-developmental disorder defined by social and communication deficits and ritualistic-repetitive behaviors. These problems are generally detected during early childhood and persist throughout life.
"For a long time autism was not viewed as being a genetic disorder," says Dr. Joseph Piven, UNC-CH professor of psychiatry. "It has a high degree of heritability, confirmed by twin studies that show a substantially higher rate in identical twins - so much so that heritability is over 90%."
Child psychiatrists believe that families with one autistic child have about a 5% risk of having a second child with autism. Dr. Piven commented that, "while that percentage is not so high, it's substantially higher than the rate of autism in the general population, which is approximately five in 10,000 kids. The data is pretty overwhelming that autism is strongly genetic, more so than schizophrenia or diabetes."
Whilst there has been epidemiological evidence of a genetic influence in autism, the search for autism genes has only recently begun in earnest. This new study is one of a small number internationally that are genetically screening the DNA of families of who have an autistic sibling.
The UCH study involved 75 families with at least two autistic children, including three families who have three autistic children. All participants had their DNA assessed from blood samples where 416 nucleotide markers were examined on selected chromosome regions in each individual. These markers help identify regions in an individuals that containing similar clusters of nucleotide sequences. Researchers than statistically analysed the results to determined if the presence of these regions was significantly greater than chance. For a region of chromosome 13, the answer was yes.
While this is vey interesting by iteslf what makes this research even more important is that it also highlighted several other possible DNA hot spots for autism genes, particularly a region on chromosome 7. This new evidence also links with the findings of another group of researchers who are looking at a location in the same region of chromosome 7. Chromosome 7 may be implicated in some forms of speech and language impairment, disorders that have characteristics which seem to overlap that of autism.
Professor Piven believes that, "there must be more than one gene involved in autism. As in all complex behavioral disorders, there's no clear evidence when looking at family pedigrees or family trees that suggests a single-gene may underlie this disorder."
After the breakthroughs in this first stage of the project a second stage now been funded by the US National Institutes of Health, for another 100 new families to be added for detailed follow-up of the results from stage one.
We shall keep you posted when the results of this research become available,