Autism spectrum disorders (ASDs) aren’t just about genetic abnormalities, and a new research project focusing on including more minorities indicates that some cases of ASD can be completely attributed to environmental influences.
According to a team of researchers from the Albert Einstein College of Medicine, though the majority of individuals with ASD have a genetic mutation, there are instances where environmental factors are the primary cause. An example of this is often seen in identical twins where one has ASD and the other does not.
What sets this study apart say researchers, is not just that it examines what happens during pregnancy to a fetus that eventually develops ASD, it is one of the only studies to include a “significant number” of minority children, including Hispanic and African-American, from the Bronx.
Overall, more than 14,000 children were included in the study, and researchers were able to look at the genetic differences between typically developing children (TD) and those with ASD.
The question the team was hoping to answer is why ASD appears to be more common in children who have mothers over the age of 35.
Studies of Autism Spectrum Disorder
Previous studies have attributed ASD to the genetic faults in sperm of older fathers, but little investigation has been done into why older women have the same issues.
Unlike men who produce sperm continually as they age, women are born with their total number of eggs and therefore the chromosomal changes as a woman ages are more minimal. This suggests environmental factors play a larger part in older women who have children with ASD.
Experts hoped that by comparing the genetic markers in cheek cells they would be able to identify if environmental stress was really to blame in this situation.
The cells of the inner cheek, like the cells of the brain, are some of the earliest produced in a fetus’s development and therefore can be used as accurate markers for similar abnormalities that may be found in brain cells.
“If environmental influences were exerted during embryonic development, they would encode a “memory” in cells that we can detect as chemical alterations of genes,” said study author Dr. John Greally in a press release. “Most of these so-called epigenetic alterations are in the form of methyl groups that chemically bind to DNA. Such methyl groups are vital for controlling gene activity, but changes in methylation patterns can dysregulate cell function by altering gene expression or by silencing genes entirely.”
Using this method of detection the research team was able to eliminate the chance that chromosomal abnormalities were at the root of ASD issues from older mothers. This left only environmental factors as the possible cause.
“Our findings suggest that, at least in some individuals with an ASD, the same pathways in the brain seem to hit by both mutations and epigenetic changes. So the severity of someone’s ASD may depend on whether or not a gene mutation is accompanied by epigenetic alterations to related genes,” said Greally. “We were able to eliminate some other possible causes of ASD such as chromosomal abnormalities, so our findings are consistent with that notion,” said Dr. Greally.
“In the case of older mothers at risk for having children with ASDs, one possible environmental influence might the aging process itself, which could disturb epigenetic patterns in their eggs, but there are other possibilities as well. Although much more work is needed, our study reveals a plausible way that environmental influences—which we know are important in ASD—might be exerting their effects.”