The environment also causes autism in some cases

(A study conducted by scientists at Albert Einstein College of Medicine at Yeshiva University) may help explain why in some autism spectrum disorder (autism spectrum disorder - ASD) may be the result of more environmental effects than gene mutations.

These findings were presented online in PLOS Genetics, shedding light on cases in which older mothers are at higher risk of having children with autism spectrum disorders. The study also paved the way for further research on the role of the environment in autism spectrum disorder.

The US Centers for Disease Control and Prevention announced in March that one in 68 American children with ASD - an increase of 30% from the rate of 1/88 two years ago .

A significant number of people with autism spectrum disorders have genetic mutations that cause this disease. But some studies - particularly those involving identical twins, in which one person has ASD and the other does not - shows that not all cases of ASD catch. Source from gene mutations.

In fact, a large study of more than 14,000 children with ASD presented earlier this month in the Journal of the American Medical Association concluded that genetic abnormalities were only May explain half the risk of developing autism . Half of that risk was due to 'having no nongenetic influences' , meaning environmental factors, which could include the mother's uterine environment or the woman's stress level. pregnant women, or diet.

The media said that the causes of ASD autism spectrum disorder mainly focus on the fact that older men (aged 40 and over) seem to have more autistic children than For younger men, it is possible that genetic mutations have accumulated over the years in sperm-producing cells.

However, older women (35 years and older) facing the same risk are completely independent of their husbands' ages. But for older women, scientists are not sure why this risk exists. Einstein researchers have looked for genetic effects, as well as the effects of the environment that may increase the risk of older women giving birth to autistic children.

Their study, led by Esther Berko, a doctoral student in the laboratory of John Greally, a doctor, studied the development of 47 autistic children and 48 normally developing children (typically developing - TD of women aged 35 and over 35. Unlike other ASD studies, this study includes a large number of Hispanic and African-American children from the Bronx.

Brain cells - cells previously used to test for evidence of genetic and environmental differences between children with autism spectrum disorders and children with normal development - are not used. Instead, researchers have found that if these differences exist, they can also occur in an existing cell type: the lining epithelial cells in the cheek.

'We hypothesized that anything that affects the autism spectrum disorder in children of older women can be present in reproductive cells that produce embryos or in the earliest stages. of embryonic development - in cells that produce both the oral and brain epithelium, "said Dr. Greally. Greally is the senior author of this research. 'That means that anything unusual that we found in children with autism compared to normal developing children must also exist in their brain cells.'

Small brushes are used by researchers to remove cheek cells from children with autism and normal babies without causing them pain. The children were sampled living in the Bronx and other areas throughout the United States, as well as in Chile and Israel. Since the eggs of older women tend to have abnormal chromosome numbers, the researchers have for the first time analyzed cells with abnormal numbers of chromosomes as well as defects. Other chromosomes may also cause ASD. Such errors are not detected in the cells of children with ASD or children with TD.

Next, the researchers examined the cells of these children to find evidence of environmental impact.'If the impact of the environment has occurred during embryonic development, effects can encode a' memory 'in the cells that we can detect as chemical changes. of genes' , Dr. Greally said. 'Most of these changes are called epigenetic changes in the formation of methyl groups , chemical bonds with DNA. Such methyl groups are important for the control of gene activity, but changes in metylation can cause cell dysfunction by altering gene expression or by resting genes. full '.

Dr. Greally and colleagues conducted several types of gene-wide metylation analysis on cheek lining cells of ASD children and children with TD, to look for epigenetic differences that may show effects. on the impacting environment (the term 'genome') is defined as the genetic material of an organism, the 'epigenome' that includes the types of methyl groups attached to the whole set. genes of an organism).

This is one of the largest studies on the extrapolation relationship of ASD performed on a single cell type. Using only one type of cell - in this case, cheek epithelial cells - helps prevent erroneous results that may occur when epigenetic studies combine different neighborhood populations of cell.

"We were very careful when doing this research, to ensure that any results achieved were of the most scientific value possible," Dr. Greally said.

Researchers have found two genetically engineered gene groups especially in children with ASD compared to TD children. Furthermore, genes known to be expressed in the brain and encoded for proteins involved in previous neurotransmission function have been shown to be weakened in ASD. (Interestingly, these two special genomic groups were not present in all the cells of children with ASD but only in a subset of cells - a phenomenon called mosaic ). In addition, two groups of genes tend to interact with genes known to have mutations in individuals with autism spectrum disorders.

'Genes interact with other genes to create molecular entrances that perform important functions , ' said Dr. Greally. 'Our research results show that at least for some individuals with ASD, similar pathways in the brain seem to be affected by both mutations and epigenetic changes . Therefore, the severity of a person's ASD may depend on whether or not there is a genetic mutation associated with epigenetic changes with related genes. "

What are the environmental effects responsible for epigenetic changes that degrade these genes? 'We have been able to rule out some other causes that can cause autism spectrum disorders such as chromosomal abnormalities, so our results are consistent with that view,' Dr. Greally said. "In the case of an elderly mother at risk of having ASDs, one possibility is that the environmental impact can cause aging itself, affecting the types of epigenetics in the eggs of these women, but Of course there are other possibilities too. " Although more research is needed, our research has shown that the effects of the environment - which we know are important for ASD - may be influencing.