In a "very exciting finding", researchers at California's Salk Institute have discovered a difference between the way nerve cells develop in people who have autism spectrum disorder (ASD) and those who don't. The researchers hope their study will contribute to a better understanding of why ASD develops, helping to create better diagnostic techniques and treatments.
ASD is a disability that impacts how people communicate and interpret the feelings and behaviors of others, as well as how they experience the world around them. Most commonly diagnosed in children, particularly boys, it impacts one in every 59 kids in the US. There is currently no cure and the exact cause or causes of the condition are still unclear – both genetics and hyperconnectivity within the brain are believed to play a role.
“It’s currently hypothesized that abnormalities in early brain development lead to autism, but the transition from a normally developing brain to an ASD diagnosis is blurred,” said Simon Schafer, a postdoctoral fellow at the Salk Institute, in a statement. “A major challenge in the field has been to determine the critical developmental periods and their associated cellular states. This research could provide a basis for discovering the common pathological traits that emerge during ASD development.”
To look at how nerve cells, aka neurons, develop in people with ASD, the researchers took skin cell samples from eight people with ASD and five people without the condition and transformed them into pluripotent stem cells. These are stem cells with the ability to turn into any type of cell in the body. By exposing the cells to certain chemicals, the team could then direct them to develop into neurons.
They then used molecular "snapshots” to look at genetic activity in the cells at different developmental stages by analyzing their RNA (a molecule mainly involved in protein production that can contain genetic information). They took a look at the cells at five different points and found something interesting early on in their development.
Essentially, at the neural stem cell stage when the cells were about to become nerve cells, a certain group of genes – some of which have previously been linked to autism – switched on earlier, leading to accelerated development. The nerve cells of people with ASD grew faster and ultimately larger than the neurons of people without ASD, as they developed longer, more complex branches than non-ASD cells. The findings are published in the journal Nature Neuroscience.
“Although our work only examined cells in cultures, it may help us understand how early changes in gene expression could lead to altered brain development in individuals with ASD,” said senior author Rusty Gage. As well as the fact that the study was conducted using cell cultures outside the body, it’s important to note that the number of participants from which the cells were taken is small.
One issue with understanding ASD and its causes is that, as its name suggests, ASD is very much a spectrum. The term encompasses a range of disorders, such as autism and Asperger's syndrome. The severity of ASD can vary widely, and those with the condition can be affected in different ways. The new study used cells from people with a specific kind of autism that causes an enlarged brain, so the findings might not apply to everyone with ASD.
“We hope these studies will serve as a framework for developing novel approaches for diagnosis during an early period of child development – long before behavioral symptoms manifest – to have the maximum impact on treatment and intervention,” said Schafer.
“This research could provide a basis for discovering the common pathological traits that emerge during ASD development.”