Researchers at Albert Einstein College of Medicine of Yeshiva University found that some cases of autism can be due to environmental factors rather than genetics in children born to mothers over 35 years of age.
A recent study involving 14,000 children with Autism Spectrum Disorder showed that gene abnormalities could explain only half the risk for developing autism. Following this, a research team led by John Greally, M.B, B.Ch, Ph.D aimed to find out why older women have higher chances of giving birth to autistic children.
For the study, the researchers enrolled 47 children with autism and 48 typically developing (TD) children of women over the age of 35. The researchers first examined the cheek cells (epithelial cells)from each of the children for any chromosomal defects or abnormal numbers that might account for autism as the eggs of older mothers are vulnerable to abnormal numbers of chromosomes. However, they found no such problems in the cells of any of the children, including those with autism.
The team also looked for environmental influences in the epithelial cells of both the ASD and TD children.
In the autistic children, two groups of genes that were epigenetically distinctive were found. "Epigenetics concerns the many, choreographed chemical reactions that activate and deactivate parts of our genes as we develop, even in the womb," explains Medical Daily.
The findings showed that the two distinctive groups had genes that were expressed in the brain and code for proteins that were involved in nerve transmission functions. Moreover, the two gene groups had chances of interaction with genes known to be mutated in children with autism.
"Although much more work is needed, our study reveals a plausible way that environmental influences - which we know are important in [autism] - might be exerting their effects," said Greally in a press release.
"Our findings suggest that, at least in some individuals with an [autism spectrum disorder], the same pathways in the brain seem to hit by both mutations and epigenetic changes," Greally said.
"So the severity of someone's [autism] may depend on whether or not a gene mutation is accompanied by epigenetic alterations to related genes." Overall, the team concluded that, in all likelihood, environmental influences are responsible for the epigenetic changes that dysregulate these genes.
"In the case of older mothers at risk for having children with ASDs, one possible environmental influence might be the aging process itself, which could disturb epigenetic patterns in their eggs," Greally said. "But there are other possibilities as well."
The study was published in 'PLOS Genetics.'
