Autism is one of those conditions where it's believed that a genetic component lies at the root of the brain abnormality responsible. That's been the view for the last 20 years, but despite research efforts, the cause hasn't been determined. So where are we in our hunt for the genetic mechanisms?
Autism was first described in 1943 by Leo Kanner who identified the features that we now know are characteristic autistic behavior; for example difficulty with social interactions, learning and communication problems, and making repetitive actions. Although the range of behaviors and symptoms is vast.
Kanner believed that autism was due to an inborn birth defect because the condition was seen in children from a very young age. The symptoms that he described had existed for years, but prior to his work, children were labeled as mentally retarded.
For years it was thought that there wasn't a genetic component because families tended to have only one autistic child. However in the last 2 decades the consensus has changed, largely because of family and twin studies. About 3% of siblings of a child with autism also develop autism according to research carried out by Piven and Polstein in 1994.
So an incredible amount of research time and effort has been invested in trying to find the genes responsible for autism. But genes may not be the only answer, there could also be environmental factors at play.
Autism Causes - Genetics
What are the causes of autism? Is it genetics? At the time of writing there is no clear cut answer, but many possible candidate genes have been located and are being studied. To find the answers scientists look at groups of people with autism and see if there is a common factor in the DNA of genes linked to communication in the brain for example. What they are looking for is a common variation in a gene that is shared by autistic people but not by the general population.
Finding such genetic variations won't give scientists the full picture but it will provide them with a good target for further exploration.
Several genes have been linked with autism; here are just a few that researchers have found in recent years.
In 2006 mutations in the MET gene, which is known to be involved in brain development, regulation of the immune system and repair of the gastrointestinal system was implicated.
- Neurexin 1 on chromosome 11. Pinpointed in 2007. The gene belongs to a family of genes that help nerve cells communicate.
- In January 2008 it was reported that variation in the CNTNAP2 gene (it makes a protein that enables brain cells to communicate with each other) was linked to autism.
There are also candidate regions on several chromosomes - 2q, 7q, 6q and 15q, and the sex chromosomes.
As with all scientific research, findings have to be replicated by other teams; a useful cross-check to ensure that what was originally detected was not a random effect or error, but is actually the real picture.
Autism Research - Treatments for Autism?
While this article has been looking at understanding the genetics that underpin autism, there is also a considerable research effort looking into environmental causes, such as exposure to heavy metals, vaccinations, and the activity of gut flora.
No definitive cause has been elucidated yet, and it's likely of course with such a complex condition, that there will be some interplay between the environment and genes. That could be the cellular environment and/or the external physical environment.
For geneticists, the next stage is to study the function of candidate genes to see how they could possibly cause autism. What is it about these genes that leads to the multifarious symptoms that we see? Only then will a clear picture of autism begin to emerge, and perhaps some possible treatments?