Our Improving Understanding of the Genetic Causes of Autism

2011-01-27 | |
Last updated: 2011-01-27

To those with insufficient background, the mental condition Autism often brings to mind stereotypical depictions such as Dustin Hoffman’s portrayal of an Autistic man in the late 1980’s movie “Rain Man”. However, the realities of this developmental disorder are far more varied and usually much more mundane. Only a fraction of those with Autism possess the special intellectual gifts depicted in that movie. The vast majority of those with Autism live lives affected to various degrees by diminished skills in communication, perception and social interaction.

Although commonly known as Autism, the condition is now better described as one of a number of Autism Spectrum Disorders (ASD) because of the variability in behavioral abnormalities experienced by those with the condition. Individuals with the disorder can be classified anywhere along a spectrum from low to high functioning. Individuals who are low functioning are mentally limited and incapable of speech while those who are high functioning often exhibit odd styles of communication and limited interests but can sometimes even live independently.

Until relatively recently, the causes of Autism Spectrum Disorder were largely unknown and much of the commonly available information regarding the causes of the condition was based on pseudo-science. Members of the public and some members of the medical community alike frequently blamed vaccines and some specific chemical agents within many of the vaccines for causing the condition. To some degree, the attempt at association was understandable because vaccinations are given at around the age that many symptoms of Autism appear.

Despite strong and repeated medical studies indicating that Autism is not the result of vaccination, many people continue to cling to this notion. In part, a lack of medical answers regarding the real causes of the condition has helped to perpetuate such theories. At the same time, Autism’s role as the fastest growing developmental disorder with roughly 1 in 110 children affected has likely helped to promote these unsupported theories. Fortunately, in the last couple of years, medical research has made strides in determining some of the contributing factors for the condition.

At the broadest level, Autism has a strong link to genetics. Studies between twins have found that the odds of a child having Autism are 25 times higher if their twin has the condition. However, in terms of specifics, no single gene has been identified as a common cause of Autism and studies to date have so far found that most genetic mutations only contribute slightly to the risk of having the condition. No specific genetic defect has been found to be involved in for more than 1 to 2% of Autism cases.

That said, recent research has managed to find a region within our genes that is commonly affected in those with Autism Spectrum Disorders. Researchers from the University of Miami, Vanderbilt University and 10 other institutions performed large scale genetic analysis of more than 10,000 people to try to find commonalities amongst those with Autism. Their analysis determined that an area in the chromosomes responsible for connecting nerve cells in the developing brain was commonly affected in those with the disorder. The finding is important because it suggests one root cause for the condition and a direction for future research.

Other genetic study has also found additional mutations that dramatically increase the risks for developing Autism. Researchers from Heidelberg University Hospital found a mutation in a gene that is involved in linking nerve cells together. Individuals with mutations in this gene all had some level of Autism while those without the mutation did not.

In yet other research, scientists from the University of Oxford found that mutations in another pair of genes also increased the risk of developing Autism. The genes in this case contribute to the organization of nerve connections.

Lastly, research from the University of California at Los Angeles found that mutations in a gene involved in learning and the ongoing connection of nerves in the brain were common amongst many individuals with Autism. These researchers even used brain scans to analyze how signals in the brain travelled differently amongst those with the Autism.

The commonality amongst these various genetic findings is that they all involve alterations to the way in which the nerve cells in the brain connect to one another and organize as the brain is developing. In terms of gaining an understanding of Autism, these findings are very promising because they all tend to be pointing in a similar direction that agrees with direct observation of Autism patients. That observation is that those with Autism do not seem to have strong connections between more distant parts of the brain that are involved in different aspects of thought. For those with Autism, different parts of the brain seem to be more isolated from another than in the brains of those without the disorder.

Although it will likely take some time for old ideas regarding the causes of Autism to be replaced with science-based views, medical science is uncovering the causes of the disorder. Genetic research is successfully linking knowledge gained from observations of Autism patients to knowledge gained regarding the roles of specific genes.  As genetic analysis continues to becomes less expensive and faster, more of these contributing factors will be identified, painting a clearer picture of Autism so we can eventually work towards treatments.

A future article will discuss efforts to improve the diagnosis of those with Autism and treatments to improve the lives of these individuals. If you or a loved one is affected by the condition, please consider sharing your thoughts in the support forums.

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