New Genetic Studies Suggest Why Autism Is More Common In Boys Than Girls
Three new studies in Neuron reports that hundreds of spontaneous genetic mutations have been linked to autism. Such CBS News describes the findings as a “shocker,” previous research has indicated that de novo or spontaneous gene mutations can be linked to the neurodevelopmental disorder. As Time magazine says, the new studies differ from previous genetic studies, which looked at families with at least two autistic children; such families “may represent cases in which inherited genetic mutations may play a more prominent role in the disorder.” The researchers chose to focus on families in which only one child is autistic and other family members are unaffected.
The new research is ground-breaking because it is, according to the journal Nature, the “most comprehensive search yet for spontaneous genetic mutations” associated with autism spectrum disorders. Further, the new studies contribute to our understanding of why autism is currently diagnosed in four times as many boys as girls. As Nature notes, the researchers found that girls on the autism spectrum tend to have “many more mutated genes” than do boys, a finding that suggests “it generally takes a larger genomic change to cause autism in girls.” That is, for a girl to develop autism, a higher number of genetic changes have to occur.
Some background about work on autism and spontaneous genetic mutations, in which the genome is either duplicated or deleted:
In 2007, Michael Wigler, a geneticist at Cold Spring Harbor Laboratory in New York, and his colleagues showed that spontaneous mutations — those that arise for the first time in an individual, rather than being inherited — are important in about half of all cases of autism (see New mutations implicated in half of autism cases). A follow-up study in 2010, of 996 autistic individuals, found that people with autism carry a heavy load of rare duplications or deletions in regions of the genome that contain genes.
Now Wigler and his group, as well as a team headed up by Matthew State, a geneticist at the Yale University School of Medicine in New Haven, Connecticut, have expanded on that search, using higher-resolution techniques to trawl through the genome. The researchers searched the DNA of more than 1,000 individuals with autism and their unaffected family members, looking for rare mutations that duplicate or delete segments of the genetic code. The teams focused largely on spontaneous mutations.
Their results indicate that spontaneous duplications or deletions of at least 130 sites in the genome could contribute to the risk of autism. Wigler believes that in total there are closer to 400 such sites.
As Wigler says, such a large number of sites makes it difficult to develop therapies that might help more than a few patients. Still, like many parents and families taking care of an autistic individual, the promise of treatments (new types of medications, for instance) is heartening.
My own teenage son Charlie has benefited from newer types of anti-seizure and other medications which have fewer harsh side-effects than their earlier predecessors. Such medications are far from a cure and must always be combined with education by trained and compassionate teachers and therapists. But they can make a huge difference in helping a child with multiple neurological challenges learn, communicate and — by helping to manage difficult behaviors — live at home and in the community.
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