Searching for genetic links between autism and other disorders

Research published in Scientific Reports this week shows a strong relationship between a specific gene, autism and 22q11.2 deletion syndrome. The findings fling open the doors to new avenues of research.
[Child with autism behind glass]
Genetic changes in autism and other disorders might give new clues to autism’s etiology.

According to the Centers for Disease Control and Prevention (CDC), autism spectrum disorders (ASD) are estimated to affect 1 in 68 children in the US.

Characterized by repetitive actions alongside difficulties in communication and social interaction, autism remains a mysterious disorder.

The causes and mechanisms by which autism impacts the brain are still very much hidden; consequently, they are the subject of much research.

When autism was first officially described in the 1940s, it was widely assumed to be a product of a child’s early environment. However, twin studies proved that ASD showed some inheritability, sparking the search for genetic components.

The full extent of genetic involvement in autism is still not known, but because science knows that there is at least some involvement, and given ASD’s complexity, genetic clues are worth pursuing. Over recent years, a number of potential genes have been implicated in the autistic condition.

Research conducted by Dr. Hakon Hakonarson and his team at the Center for Applied Genomics, Children’s Hospital of Philadelphia, PA, have been investigating potential molecular markers and their role in other diseases.

Autism in other syndromes

One notable aspect of autism is its presence within a number of disparate genetic diseases. For instance, ASD is often associated with 22q11.2 deletion syndrome (also known as DiGeorge syndrome), fragile X syndrome and tuberous sclerosis.

Although the origin of ASD is normally unclear, the mechanisms of diseases that include autistic features – like fragile X syndrome and tuberous sclerosis – are slightly better understood.

Studies have found that signaling through a type of glutamate receptor (mGluR5) appears to be significantly involved in these genetic disorders. For instance, blocking the mGluR5 in mouse models of fragile X syndrome has been shown to reverse the associated ASD symptoms.

The gene that codes for mGluR5 is called RANBP1 and is considered important in a number of neuropsychiatric disorders.

Dr. Hakonarson’s recent endeavor specifically looked into the functioning of mGluR5 within autistic patients compared with those with 22q11.2 deletion syndrome.

22q11.2 deletion syndrome

Although 22q11.2 deletion syndrome occurs in 1 in 2,000-4,000 individuals, it often goes undetected by medical professionals.

The disorder involves errors in certain regions of chromosome 22. These mutations cause a myriad of problems including gut disorders, heart problems, immune system changes, face and palate defects and learning disabilities. Importantly, in regards to this study, ASD is also present in some 22q11.2 deletion syndrome patients.

The research team compared DNA from 539 ASD children with 75 22q11.2 deletion syndrome sufferers (25 of whom showed ASD symptoms). The samples were scrutinized for duplications or deletions within the RANBP1 gene.

Previous work by Dr. Hakonarson showed that RANBP1 genes are more likely to be altered in patients with ASD. For this round of studies, he wanted to uncover whether individuals with 22q11.2 deletion syndrome who also had ASD symptoms showed similar changes in their mGluR genes.

Dr. Hakonarson explains the latest results:

“Based on this study, we propose that the RANBP1 gene is a significant genetic factor in both ASD and 22q.11.2 deletion syndrome. Furthermore, when the mGluR network is disrupted at multiple points, it predisposes individuals to a more severe disease.”

So, not only did mutations in RANBP1 preempt ASD symptoms, the more mutations that were present, the more pronounced the symptoms.

This type of genetic research brings us ever closer to understanding and eventually treating these mysterious and multifaceted disorders. It is only through deep and thorough probing that clues can be glimpsed.

The team believes that the study might add extra fuel to the studies of a number of diseases:

“The gene we investigated may function as an important factor, not only in forms of autism but also in other neuropsychiatric conditions.”

The hunt for solutions continues. Medical News Today recently covered research into another potential genetic marker for ASD.

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