Although the link with paternal age jives with some epidemiological studies that have found higher rates of autism among children of older parents, it probably only plays a part in a modest 10 percent or so of patients, Eichler said.
From the three studies, mutations in two genes, called CHD8 and KATNAL2, emerged as likely autism risk factors because they were found in more than one patient. "Almost never did we see lightning strike the same place twice," Eichler said.
Unlike the myriad mutations identified in genes involved in neuronal development, these mutations could have more universal effects on regulating gene expression, cell growth and differentiation.
These two genes were also among the 49 genes that fell into the same biological pathway, Eichler's team found. "This one is a monster pathway," Eichler said, because it involves the largest number of identified de novo mutations.
The gene mutations identified in this research "underscores that autism is a complex interplay between genes and the environment," Shih said. For example, CHD8 can control the expression of other genes in response to environmental stimuli.
This research is also a reminder that autism is a group of related disorders involving many genes in different pathways, he added. "Each of the genes [in these studies] seem to confer only a small risk, and are only readily found in a small percentage of individuals with autism," he noted.
However, Shih said, these studies show that with more genetic analyses involving more patients, "there could be some unifying principles revealed that could allow identification of individuals at risk of autism and guide therapeutics."
To learn more about autism, visit the Autism Society of America.
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