The research team, led by Hakon Hakonarson, MD, PhD, explained in the journal PLOS ONE that they identified 25 additional copy number variants (CNVs) that occur in some people with autism. CNVs are duplicate or missing stretches of DNA.
They describe these copy number variants as individually rare, but of "high impact", meaning that each one has a strong effect in increasing a person's risk for autism.
Dr. Hakonarson said:
"Many of these gene variants may serve as valuable predictive markers. If so, they may become part of a clinical test that will help evaluate whether a child has an autism spectrum disorder."
Scientists from the Seaver Autism Center at Icahn School of Medicine at Mount Sinai said that there are hundreds of mutated genes linked to ASDs.
Study builds on previous genetic research on ASDThe authors wrote that their latest study had built on and extended previous gene research carried out by Dr. Hakonarson and other scientists who specialize in ASDs.
In this study, the team initially analyzed the DNA of 55 people from families in Utah with multiple members who had been diagnosed with ASDs. The data from high-risk families had been collected by Mark Leppert, PhD. They identified 153 CNVs as potentially linked to autism.
The team wanted to look at these CNVs in a broader ASD population. They custom-designed a DNA array with probes for all 153 CNVs, as well as an additional 185 CNVs which had been linked to autism in previous studies. They gathered and examined all the data to determine how common all the CNVs were in 3,000 people with an ASD and 6,000 control subjects previously gathered in studies carried out at The Children's Hospital of Philadelphia.
The researchers found that:
- Fifteen of the CNVs that were identified in the family studies, plus nine more CNVs found by their custom array all had an odds ratio of over more than two. This means that people with those variants are at least twice as likely to develop an ASD, compared to the general population.
- Another 31 CNVs that had previously been found to be linked to autism had an odds ratio of at least two.
"These high-impact variants could be most useful in advising parents who already have one child with an ASD. If a second child has delays in reaching developmental milestones, testing for these CNVs could help predict whether that child is also likely to develop an ASD."
The newly identified CNVs need to be added to the ones already in existence in commercially available diagnostic arrays.
Hakonarson said that the CNVs identified in this study occur in genes that are involved in signaling pathways and neuronal development. This reinforces similar findings by Hakonarson and team in their genomic research that was published in 2009.
Hakonarson said "Many of these gene pathways active in ASDs overlap with those in other nervous system disorders, such as schizophrenia and epilepsy. At the same time, our results are consistent with other studies suggesting that many different biological pathways, when disrupted, can lead to ASDs."
The authors concluded:
"Taken together, these data provide strong support for the existence and application of high-impact CNVs in the clinical genetic evaluation of children with ASD."
What is Autism? What is Autism Spectrum Disorder (ASD)?ASD stands for Autism Spectrum Disorder or Autistic Spectrum Disorder. Autism and ASD are commonly used interchangeably. ASDs are a number of developmental disabilities which are the result of a brain abnormality. An individual with an ASD generally has problems with social interaction and communication skills.
Autism is referred to as a complex developmental disability. According to experts, Autism signs and symptoms appear during the first three years of life.
An individual with ASD prefers to stick to a set of behaviors and does not welcome any major (and some minor) changes to their daily routine. Friends and relatives often find that if the person knows in advance that a change is coming, and they have time to prepare or adjust for it, their resistance is much less.
Autism is a wide-spectrum disorder - in other words, each person with an ASD will be affected in a unique way, no two people with autism have exactly the same symptoms. Apart from experiencing a wide combination of signs, some will have mild symptoms while others have more severe ones.
Below are some of the signs and symptoms that exist in people with ASD:
- Social skills - people with autism interact with those around them differently, compared to how the rest of the population does. In less severe cases, for example Asperger's syndrome, the individual may appear to be socially clumsy, occasionally offensive in their comments, or out of synch with the people around them. They may miss subtle cues that humans give each other, and find it hard to interact socially because of this. In severe cases, the person appears to have absolutely no interest in other people. There may be very little eye contact.
- Empathy - a person with an ASD often finds it harder to understand what other people are feeling or thinking. Their ability to instinctively empathize is usually poor.
- Physical contact - a significant number of people with ASD do not like cuddling or being touched. However, many are tactile and enjoy hugs and physical forms of affection, especially with family members. Some say that if a child with autism is hugged and touched regularly from an early age, they are more likely to accept and even enjoy physical contact.
- Oversensitivity to light, noises, temperatures and smells - people with an ASD may be overly sensitive to sudden loud noises, certain smells and unusual light patterns (flashing, bright lights, strobe lights, etc). Sudden temperature changes may also affect a person with autism more than other people.
- Speech - even people with Asperger's syndrome (mild symptoms) speak in a very formal way. Their intonation may sound flat. Children and teenagers may sound like "little adults". In severe cases the person might not speak at all. Echolalia (repeating words or phrases one hears) is common in people with autism.
- Repetitive behaviors - predictability is important for most people with autism. There is a love routine, even to the point of engaging in repetitive behaviors which for others may seem excessive and sometimes bizarre. Some repetitive behaviors may be quite intricate, and are commonly done again and again.
- Milestones reached at different moments - a person without autism develops in several areas at a relatively harmonious rate; this may not be the case for many children with autism. Cognitive skills may develop rapidly, while social and language skills trail behind. Coordination may take longer to develop.
- Physical tics - a much greater proportion of people with autism have motor tics compared to the general population.
- Obsessions and compulsions - these are common among people with autism.
An article published in the Journal of Child Psychology and Psychiatry found that some children outgrow their autism.