Autism and the Genes

Can Autism Run in the Family? Autism Genetics Explained

What causes autism? Does genetic make-up play a role in autism? What is the contribution of environmental factors? How autism can be prevented and what are the available treatments?

There are so many questions and such few answers. Autism has not only frustrated parents in their handling of an autistic child but also baffled scientists in their research on this condition. It has not been easy to understand autism.

What is autism

Autism is one of a group of disorders called autism spectrum disorders (ASDs). A neuro-developmental condition which affects the normal brain functioning of a person, it manifests itself in unusual and abnormal behaviors in day-to-day activities. Autism is said to have its roots in very early brain development and believed to impact growth in the areas of social interaction and verbal and non-verbal communication skills and cause repetitive behavior though the intensity may vary from person to person.

Autism is a developmental disability but its identification is not easy and very often, it is mistaken or confused with other more common disorder. It is present from early childhood and can start showing up as early as two to three years of age.

Is there a gene that causes autism

Autism affects over three million individuals in the US and tens of millions worldwide. It is believed that in autism the brain’s normal functions are disrupted as a result of a neurological disorder. Research suggests that genes are strongly involved. Though this may not always be the case. The risk was far higher in identical twins where one twin had autism, as they share the same DNA. In many instances, there is no family history involved and at best, there are only subtle examples of ASD-like symptoms in a relative. One-off incidences of autism, where only one person is found to be autistic, are referred to as simplex autism. However, even in these cases, there is probably a strong genetic component, but the types of genetic influences are likely to differ.

Many research projects have been launched to identify genes associated with autism and more than 20 years have gone into this study. The purpose behind the studies is to develop tools that can help assess a child's risk and enable earlier diagnosis and intervention to improve outcomes.

In recent years, the emergence of micro-array DNA technology has significantly advanced the search for autism’s missing genetic factors. This expertise is being used by researchers to come up with an answer to this mystery.

Autism genetic risk factors

In one study, researchers found that there are multiple and different risk genes that combine in various ways to cause ASD in any individual. Many of the risk genes seem to have only a small influence and require a specific combination of risk factors to cause ASDs. Researchers have found that small, common gene variations can add up to substantially increase the risk for ASD.

According to experts, if you have one child with autism, the risk for the next child could be only 2-6%. But, if one gene was involved then the risk would be 25% or even 50%. In case of there being two children with autism in one family, the chances that the third one will also be autistic are around 35%. By this they indicated that there is not one gene but lots of different genes involved.

DNA study of autism

In a different study, when a team of researchers compared the DNA of autistic children to their parents, they discovered that autism can happen when big chunks of DNA go missing or get duplicated. And that DNA changes in lots of different places can cause autism. Researchers associated autism with hundreds of gene changes called copy number variants (CNVs). CNVs consist of duplications or deletions of entire sections of DNA. Individually, any one CNV is rare. But as a group, they are relatively common – particularly among individuals with autism.

Another group of genetic researchers discovered a new 24 ‘high impact’ autism gene changes. Each more than doubles the risk that a child will develop autism.

Disruptive CHD8 mutation linked to autism?

In a very recent study dated July 2014, a team of researchers came up with the conclusion that people with a mutation in the CHD8 gene have a very ‘strong likelihood’ that they will have autism marked by gastrointestinal disorders, a larger head and wide set eyes.

The researchers carried out an in-depth study of 6,176 children with ASD. They discovered that 15 of them had a CHD8 mutation. They also found that all these 15 were similar in appearance and had sleep disorders and gastrointestinal problems.

According to the experts, the CHD8 gene mutation is the first to show a very strong penetrance linked to a certain subtype of autism.

Importance of autism research

This study could lead the way to a "genetics-first approach" that could uncover hundreds more genetic mutations and lead to genetic testing. This could provide some direction to families with autistic children and clear their understanding about autism. They will be able to handle children with autism better and with a more pragmatic approach. It can also pave the way for this small minority with CHD8 mutation to get targeted treatment.

All these discoveries bring doctors closer to a practical gene test that can help diagnose autism or spot young ones as being at-risk before the symptoms start to appear. Such tests could help identify infants and toddlers who could benefit from early interventions that promote healthy brain development and improve outcomes.

Autism research has come a long way in the past decade and though, the precise cause may still remain obscure, the picture is far clearer than before.