Friday, November 18, 2016

New study finds common link across autism spectrum disorders

TheConversation: There have been a multitude of studies attempting to find causes, both genetic and environmental, for autism. One of the big questions in autism research is whether autism is a single disorder or many different disorders that happen to present in the same way. Although recent genetic research has indicated hundreds of different genes contribute to autism, a new discovery has found there could also be commonality among most patients with autism. Autism is characterised by a certain pattern of social communication and social interaction skills and repetitive and restricted behaviours that differ from the rest of the population. Symptoms can range from mild to severe.

We know from studies of twins, and observations within families, autism has a large genetic component.
However, despite there being hundreds of autism-associated genes known to us, most have a very small effect on whether or not someone will have autism. There are also no genetic tests that can diagnose autism.
Recently, researchers started studying the environmental contributions to autism: the other side of the nature-nurture coin. They looked to events as far back as the womb.
Looking beyond the DNA sequence, we know both genetic factors and environmental factors such as diet, stress and pollution can change the switches that switch our genes on and off.
We call these switches “epigenetics,” and when we study them, we are measuring the molecules that change these switches.

Epigenetics and autism

In autism, we can study the pattern of these epigenetic switches (which are turned on and off) and compare the pattern to that seen in people without autism. In this way we can better understand the causes of autism, and may one day be able to diagnose autism much earlier or pinpoint environmental factors that can be avoided.
Ultimately, we want to improve the quality of life for people living with autism and provide their families with timely assistance.
In 2015 my colleagues and I reviewed recent studies that had searched for the epigenetic switches specific to autism. Although the field was in its infancy, there was a small number of switches that had been identified as being closely linked to autism. However, this knowledge was not yet ready for use in the clinic.
This area of research has just received a large boost from a group of investigators based in Singapore, USA and the UK. The researchers have looked deep inside the brains of people with autism after they had died.

Finding a molecule to link to autism

The researchers looked at a specific epigenetic switch called “acetylation”. The acetylation switch causes a gene to increase in activity.
The researchers looked at the patterns of acetylation at different locations in the brains of people who had been affected by autism and compared the pattern to that seen in the brains of people who had not been affected by autism.

Further reading: What causes autism? What we know, don’t know and suspect

They found hundreds of genes that had a different “switch pattern” in autism brains compared to non-autism brains. The list of genes makes interesting reading, including genes important for the transmission of electrical messages in the brain, as well as genes involved in epilepsy (which affects some people with autism), behaviour, gut function and immunity. Each of these genetic pathways had previously been associated with autism.

Commonality across the spectrum

Most interestingly, the investigators identified a specific “switch pattern” that was shared by most (but not all) of the autism brains. They concluded they had discovered an “epigenetic signature” of autism.
In a nutshell, this research tells us even though autism may have many different underlying causes, including genetic and non genetic factors, at the level of epigenetics, these causes converge to have a similar effect on the brain. Autism is both one disorder and many.

What does this all mean?

The fact autism brains have so much in common is positive news for families affected by autism and for researchers in the field. It means despite there being many causes for autism, it may be possible to develop single diagnostic tests and therapies that target the single common epigenetic pathway.
Researchers will also be able to examine environmental factors such as diet, pollution and illnesses, and determine what affect these early life factors have on the epigenetic signature of autism.
Studies like this go a long way to helping researchers understand autism better and in the long term, improve quality of life for people living with the condition.
We would like to strike a note of caution, though. This is the first study of its kind and needs to be repeated on more individuals from different locations to see which findings hold up.
We also must not forget many people with autism don’t want to be “cured”. They often want nothing more than to be understood and respected by the rest of us.