The genetics of autism
One recent estimate is that genetic factors may contribute about 90% to autism, while environmental factors contribute no more than 10%.
Abnormalities of chromosomes, in many cases visible under the microscope, are thought to account for about 10-20% of autism cases, with the remainder caused by combinations of different genes acting in combination.
This means that autism is a complex genetic disorder.
While single gene (Mendelian) disorders, such as Huntington's disease, are caused by mutations on just one gene, complex disorders are caused by a number of different susceptibility genes, which combine and interact with environmental factors to produce an overall risk factor for developing autism.
Over the past 15 years or so, there has been remarkable success tracking down genes for single-gene disorders. Unfortunately, such approaches are not usually powerful enough for complex genetic disorders such as autism. Recently, however, novel strategies have been developed that are more appropriate for finding genes influencing complex disorders. We are using these techniques in our research to track down the specific genes implicated in autism.
The Autism research team has focused on identifying autism susceptibility regions (i.e. regions of interest that may contain genes that increase the risk of developing autism).
A number of candidate autism susceptibility genes have also been identified.
In complex genetic disorders, each susceptibility gene confers an increased risk of developing the disorder, but by itself may have only a weak to moderate effect, and alone is insufficient to cause the full clinical phenotype. Other factors, such as an individual's sex and environmental influences, may also affect the severity of the disorder.
It is thought likely that between 2 and 15 different genes may be involved in autism.
(1) Autism: the quest for the genes. [PubMed record]
Autism's cause may reside in abnormalities at the Synapse [News Focus in Science]
The International Molecular Genetic Study of Autism Consortium (IMGSAC) was established in 1994. It is a leading international autism consortium that includes scientific researchers and clinicians from a number of European countries, as well as from Canada and the United States. Researchers from the Autism research team have collaborated with IMGSAC on a number of autism research projects.
Autism Genome Project (AGP) Phase 1:
The Autism Research Project (AGP) is an international collaboration that brings together research institutions, clinicians and scientists from across Europe, Canada and the USA. The first phase of the AGP was successfully completed in early 2007.
The Autism research team is currently engaged in research on autism in the framework of the following three projects:
Autism Genome Project (AGP) Phase II:
The Autism Research Project (AGP) is an international collaboration that brings together a large number of research institutions, clinicians and scientists from across Europe, Canada and the USA. The second phase of the AGP was initiated in April 2007 and will run for three years.
EU Cordis Project - Autism Molgen: