Thanks to the analysis of simple blood samples, American researchers have identified a new genetic network linked to the development of the fetus. The more the latter is altered, the more the child will suffer from severe autism, according to their study.
Worldwide, approximately one in every hundred births is affected by Autism Spectrum Disorder (ASD). This developmental disorder is manifested by disturbances in the areas of reciprocal social interactions, communication and by behaviors, interests and activities of a restricted and repetitive nature. But what are the root causes of this disorder? If we still ignore it, we are almost sure that everything is decided before birth. Several studies have notably evoked the role of hormone levels and genes as potential risk factors.
And according to a new study published Monday, September 23 in the journal Nature Neuroscience and conducted by researchers at the University of California in San Diego (United States), in addition to certain genes identified as risk factors, a mutation must significantly disrupt the cerebral development of the fetus to develop the disease. The more a certain network of genes is altered, the more autism would be important, assure the researchers who discovered this thanks to a simple blood test. Ultimately, these results could help to diagnose the disease and its extent earlier, thus ensuring better care.
In ASD research, “hundreds of genes have been implicated, but the underlying mechanisms remain obscure,” says Nathan E. Lewis, co-author of this study. “Growing evidence indicates that ASD is a progressive disorder that, at the prenatal and early postnatal stages, involves a cascade of molecular and cellular changes,” adds Eric Courchesne, co-author of the paper.
A new gene network linked to fetal development
To detect them, the researchers had the idea of studying white blood cells. “Unlike living neurons which have a limited time window for proliferation and maturation, other cell types are constantly regenerating, such as blood cells. Given the strong genetic basis of ASDs, some signals of dysregulated development can reproduce continuously in blood cells and therefore be studied after birth,” they explain.
They therefore studied the blood samples of 226 boys aged 1 to 4 years, with and without a diagnosis of ASD. From their white blood cells, they analyzed the expression data of unusually active or, on the contrary, extinct genes. They were then able to identify a new network of genes linked to fetal development. The function of this network also corresponds with certain genes previously identified as risk factors for the disease.
“We found that many of the known risk genes linked to ASDs regulate this main network and therefore their mutations can disrupt this developmentally essential network”, summarizes Vahid H. Gazestani, first author of the study. According to the researchers, these genes could send signals to this network. The latter would then emit signals in turn, modifying the formation of the fetal brain. Moreover, the more the network is affected, the more autism is severe, also noted the researchers.
Diagnose ASD earlier for better care
“The study shows that, through gene expression analyzes from ordinary blood samples, it is possible to study aspects of the fetal molecular origins of ASDs, uncover the functional impact of hundreds of genes from risk of ASDs discovered over the years and to develop clinical tests for diagnosis and prognosis of severity”, says Nathan E. Lewis.
These results therefore open up new avenues for diagnosing ASD as early as possible and thus being able to better manage the disease. If the diagnosis is possible from the age of 18 months, it is currently quite complicated. Indeed, it is based on unstable behavioral symptoms when the child is still very young, such as atypical facial expressions or inappropriate social interactions.
“There is an urgent need for robust tests that can identify the disorder and its expected severity at an early age so that treatment can begin early, allowing every child to achieve better outcomes,” concludes Eric Courchesne.
In August, other American researchers, from the University of Darthmouth, had also published a study aimed at facilitating the early diagnosis of autism. They thus succeeded in identifying a neurological marker of the disease, non-verbal and objective, showing that the patients were slower to pass from one image to another.
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