Four New Autism Subtypes Link Genes to Children’s Traits

Researchers identify four autism subtypes with distinct genes and features

By Allison Parshall Published by Jeanna Bryner

Stephen Shore, special teacher of special education at the University of Adelphi, said: “If you have met an autistic person, you have met an autistic person.” This quote is popular in the community of autism and among researchers because it reflects something with which they attack all the time: the really incredible diversity of experiences which are the diagnosis of the autism spectrum disorder (TSA).

“The beauty of the spectrum of autism is: it talks about this heterogeneity. And the disadvantage [is that] It covers the differences, ”explains Fred Volkmar, psychiatrist and emeritus professor at the University of Yale. At the moment, individuals are placed on the spectrum according to the level of gravity, level 1 at level 3, of two different criteria: social communication difficulties and restricted behaviors. Characteristics to divide the spectrum into significant subtypes.

Now in a study published Wednesday in Genetics of nature, The researchers have filled a significant gap by connecting different clusters of behavioral features and development with underlying genetic differences. By analyzing the data of a group of 5,392 autistic children, they identified four distinct autism subtypes, each with different types of challenges, which are linked to specific types of genetic variations.

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“For families who sail on autism, understanding the specific subtype of their child can provide greater clarity and open the door to more personalized care, support and connection,” explains Natalie Sauerwald, co-leader of the article, which studies genomics at the Flather Institute in New York. But it is not yet clear if these four subtypes, which have been identified with statistics in a non-representative and largely white group of autistic children, will be useful to help diagnose and take care of autistic people in real clinical environments.

When the genetic sequencing of the human genome began seriously in the 1990s, the researchers of autism hoped to identify the genetic cause – or more likely, the causes – of the condition. “Twenty years ago, geneticists said:” We are not even going to need autism [as a diagnosis]; We are just going to have genetically defined disorders ”, explains Catherine Lord, a psychologist specializing in autism at the University of California in Los Angeles.

It did not happen. “Genetic autism is very complex,” explains Aviya Litman, a student of the new study, a student graduate in genomics at Princeton University. Although autism is between 60 and 80%, it is difficult to identify a specific genetic cause for an individual – the cause is only clear for around 20% of people with the testists, explains Litman. The researchers have now identified hundreds of genes associated with autism, which means that if an individual has certain genes, they have much higher chances of being diagnosed as autistic. But even with this knowledge, scientists have not been able to reliably connect the way these genes result in specific autistic features and development trajectories.

To fill this gap, Litman, Sauerwald and their colleagues turned to data from a major study which followed the genetic information, the features and the development of 5,392 autistic children aged four to 18. The researchers assessed young participants on social communication capacities, restrictive and repetitive behavior, development milestones, and more. By using a computer model, statistical tests and clinical judgment, the team separated participants into four robust groups based on models of their features and their development.

• Social and behavioral challenges: These children, 37% of participants, had more difficulty in social communication and restrictive and repetitive behavior than other autistic children. They also had more challenges with disruptive behavior, attention and anxiety. These children, however, have not undergone significant development delays.

• Mixed ASD with development delay: These children, 19% of the participants, were more varied in their social communication and their restrictive and repetitive behaviors, and they showed delays in development compared to non -autotete children.

• Moderate challenges: These children, 34% of participants, always had less difficulty in social communication, restrictive and repetitive behaviors and other basic autistic features compared to other autistic children, although they have still had more difficulty in them than non-self-auto-auto-auto-autochton children. They had no development delays.

• Largely affected: These children, 10% of participants, had more serious and large -scale difficulties with social communication, restrictive and repetitive behavior and other basic autistic features, including development delays, compared to other autistic children.

These groups still contained many variations within them, but the participants in each were more similar to each other than for the participants in other groups. The four groups were also reproduced in another smaller population of autistic children.

The researchers then analyzed the genetic differences between the four groups and found that, remarkably, they had very distinct genetic profiles. “For me, the biggest surprise has been to know how different the four subtypes proved to be different. The underlying genetics and biology are very different, ”explains Olga Troyanskaya, a genomic researcher at Princeton and the main author of the study. For example, different genes become active at different times of development – some become relevant before birth; Others do it afterwards. The group of social and behavioral challenges had more mutations in the genes that have become active after birth, say Litman and Troyanskaya, which could explain why these participants had no development delays and tended to be diagnosed later than those of the other three groups.

“I expected these subtypes to have differences in their biological foundations,” said Sauerwald, but the differences were even more pronounced than she expected, with a very little biological overlap.

These four groups are not entirely unknown to Volkmar and Lord, none of which has been involved in the study. “Groups have a meaning and follow a lot of results by other researchers,” says Lord. In this regard, the subtypes “have a” rediscover the appearance of the wheel “, says Volkmar – it is the link with genetics that makes these results most remarkable.

These sub-groups almost certainly do not cover the whole spectrum of autism, since the results were based on a sample which did not represent the autistic population in general. The sample was 77% white, and certain parts of genetics could only be carried out for people with European ancestry due to limitations of available data. In addition, certain features related to autism are rare and may not have been sufficiently present in the sample to be captured by the statistical measures of researchers. “This classification is not a final and complete group,” explains Troyanskaya. “With additional data, more precise definitions of the subtypes could emerge.”

For Volkmar, the study “talks about the need to be a little more with a fine grain in our approaches to the diagnosis,” he said. “It leads us to think about new approaches” in the way of diagnosing and understanding autism – with subtypes rather than one condition.