A Genetic Clue to Why Autism Affects Boys More [TIME.com]

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A Genetic Clue to Why Autism Affects Boys More
By ALICE PARK Tuesday, May. 19, 2009



Among the many mysteries that befuddle autism researchers: why the disorder affects boys four times more often than girls. But in new findings reported online today by the journal Molecular Psychiatry, researchers say they have found a genetic clue that may help explain the disparity.


The newly discovered autism-risk gene, identified by authors as CACNA1G, is more common in boys than in girls (why that's so is still not clear), and the authors suggest it plays a role in boys' increased risk of the developmental disorder. CACNA1G, which sits on chromosome 17, amid other genes that have been previously linked to autism, is responsible for regulating the flow of calcium into and out of cells. Nerve cells in the brain rely on calcium to become activated, and research suggests that imbalances in the mineral can result in the overstimulation of neural connections and create developmental problems, such as autism and even epilepsy, which is also a common feature of autism. (See pictures of inside a school for autistic children.)

"Our current theories about autism suggest that the disorder is related to overexcitability at nerve endings," says Geri Dawson, chief science officer of Autism Speaks, an advocacy group that provided the genetic data used by the study's authors. "It's interesting to see that the gene they identified appears to modulate excitability of neurons."

For the new study, researchers at the University of California, Los Angeles (UCLA), combed the genetic database of the Autism Genetic Resource Exchange (AGRE), a resource of DNA from 2,000 families with at least one autistic child. The scientists focused on the more than 1,000 genetic samples of families in which at least one son was affected by the disorder, prompted by the results of an earlier study using the same database, which identified a rich autism-related genetic region on chromosome 17 that contained genetic variants more common in boys than in girls. While nearly 40% of the general population has the most common form of CACNA1G, one variant of the gene was more prevalent in autistic boys, researchers found. "There is a strong genetic signal in this region," says Dr. Daniel Geschwind, director of UCLA's Center for Autism Research and Treatment and one of the study's co-authors. "But this gene doesn't explain all of that signal or even half of it. What that means is that there are many more genes in this region contributing to autism."

That's not surprising for a disorder as complex as autism — actually, a spectrum of developmental disorders involving impairment in language, social behavior and certain physical behaviors — with symptoms that range widely in number and severity. So far, studies have linked a handful of genes, all of which play a role in the way nerve cells connect and communicate, with autism spectrum disorders. It's likely not only that a large number of genes contribute to the disorder, but also that a different combination of genes — as well as unique interactions between genes and environment — are responsible for each individual case of autism.

So it's certainly a daunting challenge to begin teasing out the individual genes that may contribute to autism, as the UCLA team has with CACNA1G, but databases like AGRE make the job slightly easier. The next step will be to try to use known autism genes to help develop screening tools or early interventions. "We are going to have a much better understanding of the causes of autism over the next five to 10 years," says Dawson. "We're in a period of great discovery."

The newly discovered autism-risk gene, identified by authors as CACNA1G, is more common in boys than in girls (why that's so is still not clear)

I'm trying to figure out how this could possibly work, how a gene on chromosome 17 could be more common in males. I can only think of two possible explanations.

It would be more productive to understand what causes autism.

Autism has exploded in the USA. So, either the autism gene is being spread at an epidemic rate (not likely) or environmental changes are triggering more autism cases (very likely). Girls have a "blood barrier" factor that filters out more contaminants and lets them endure certain toxins better than boys do. If autism is being triggered by an environmental factor, this explains why so many more boys than girls develop autism.

We're literally poisoning the population. We've got so many hormones in the drinking water (as waste treatment plants don't remove them in the filtration process) that it is considered a major cause behind the growing number of infertility issues couples suffer from.

It would be more productive to understand what causes autism.

Autism has exploded in the USA. So, either the autism gene is being spread at an epidemic rate (not likely) or environmental changes are triggering more autism cases (very likely). Girls have a "blood barrier" factor that filters out more contaminants and lets them endure certain toxins better than boys do. If autism is being triggered by an environmental factor, this explains why so many more boys than girls develop autism.

We're literally poisoning the population. We've got so many hormones in the drinking water (as waste treatment plants don't remove them in the filtration process) that it is considered a major cause behind the growing number of infertility issues couples suffer from.

They're known simply as the "blue people" in the hills and hollows around Troublesome and Ball Creeks. Most lived to their 80s and 90s without serious illness associated with the skin discoloration. For some, though, there was a pain not seen in lab tests. That was the pain of being blue in a world that is mostly shades of white to black.