New Research Explores the Hereditary Causes of Autism
The exact cause of autism is not yet known, but scientists point out several factors, including genetics. Most studies that show genetic links with ASD however, only showed novo mutations – those that arise spontaneously in the child’s genetic makeup and not passed by the parent to the child.
To further investigate how autism may run in families, two new studies from Broad Institute were conducted. So far, they are the first among those who provided an in-depth research on the hereditability of autism.
What were their findings?
In one study, Broad researchers found that about 5% of autism cases could be linked to inherited recessive mutations that tend to completely disrupt gene function. The team, which was led by Mark Daly, a senior associate member of the Broad and co-director of its Medical and Population Genetics program, looked at the exomes of around 1,800 autism cases and controls, looking on cases when the child inherited two broken copies of the same gene from their parents. They called it ‘double knockouts’ – an autism case that is relatively rare and disease-causing. According to them, approximately 3% of autism risk is linked to double knockouts. The researchers also checked the knockouts on the X-chromosomes in male and found a 1.5-fold increase as compared to the controls. This finding could explain why autism is more likely to develop in males than in females.
The other study, which was headed by Christopher A. Walsh, an associate professor at Harvard Medical School and Massachusetts General Hospital and associate member at Broad, suggest that autism results from only a partial loss of gene function. They argued that many of the partially-disabling mutations that lead to autism occurs in genes in which complete disruption of gene function has been known to cause more severe inherited illnesses. For instance, milder forms of Mendelian diseases usually develop as autism spectrum disorders. Their study involved 200 families in which parents of children with autism were first cousins. While many of the gene mutations they identified only resulted to partial disruption (as opposed to Daly’s findings), Walsh’s team found that most of these mutations took place in genes linked to more severe diseases. Had their function become completely disrupted, these children could have developed more serious health problems.
All the findings of these two studies suggest that autism may have different genetic causes. According to Walsh, mutations in hundreds or thousands of genes could result to autism. Their studies open up the possibility of developing more effective treatments.
The two teams are now joining forces to further investigate the genetic nature of autism. They also plan to collaborate with other centres and pull data from a larger number of patients.
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