New and far-reaching studies focus on locating the elusive genes and the environmental influences that apparently cause autism
Two twins are born and both babies begin to develop normally. However, on their first birthday, differences between them begin to emerge - when the son makes less eye contact than the daughter and returns less love. He often wears a detached expression and shows a fixation on certain puzzles and patterns. At the age of three, the symptoms lead to a diagnosis that has become alarmingly common in recent years: autism.
What causes a disease that currently affects 1 in every 166 children, and why is the number of boys with it 4 times higher than the number of girls? Genetics researchers from the University of California, Los Angeles are close to solving the mystery. Last spring they announced that they had located the presumed location of the gene that causes autism, on chromosome 17. The proof was found only in families with autistic sons, indicating the genetic basis of the differences between the sexes in the distribution of the disease. After reporting the discovery in the American Journal of Human Genetics, the scientists will try to isolate the gene from among the approximately 50 genes in the relevant cluster - an exhausting process that may take another year.
As if to complicate matters, the researchers believe that the gene located is only one of dozens of genes related to autism, and many of them may cause the disease only if the genetic load is activated by an external factor; How then does the environment fit into the picture? Although the researchers succeeded in cracking the genome, the environmental factors - everything that affects the person carrying the gene, from parenting to air pollution - remains a mystery and the knowledge on the subject is partial and fragmented.
In order to decipher the environmental causes of the disease, William Eaton, a psychiatrist from John Hopkins University, recently participated in a large-scale study of 700 Danish children. A fascinating match was discovered in the study. Based on the trends emerging from a variety of parameters, such as birth weight and socioeconomic status, the scientists discovered that autism is common both among children with a family history of schizophrenia and among children whose birth involved complications, such as premature birth or breech birth.
The researchers from the University of California at Davis conducted an even more extensive study than the Danish study, called CHARGE, and carefully examined every factor - from genes to exposure to mercury. The researchers hope to find certain patterns and are not trying to find a single cause of autism. After sifting through the mountains of data, the researchers located a first pattern: certain proteins, the digestive system and components of the immune system found in the blood of autistic children are significantly different from those of healthy children. The discovery, published in May at an international conference of autism researchers in newborns, will make it possible to start treatment long before external signs appear.
If autism is indeed caused by a complex web of genetic and environmental factors, the researchers believe that, at least in the short term, it will be easier to reduce the environmental problems, than to face the more complex biomolecular challenge of locating and changing the relevant DNA. There is only one other disease that humans suffer from that is as complex as autism: cancer.
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The brain savant
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