A study, partly funded by the National Institute of Mental Health, and conducted by scientists Jonathan Sebat, Lakshmi Muthuswamy and Michael Wigler, at the Cold Spring Harbor Laboratory has concluded that as many as 100 extremely small and rare gene mutations present greater risks for autism than earlier believed.
These mutations occurred ten times more often in intermittent cases of autism range illnesses than in control subjects who were healthy. However they were found to be only twice as common in autism cases with families having more than one such person.
This suggests that the irregularities are the main causes of autism and do not just contribute toward it. They are not what people usually consider genetic mutations but are missing stretches or extra copies of DNA and are therefore called copy number variations.
In spite of showing similar symptoms, diverse cases of autism were therefore traceable to any of 100, or more genes, whether they occurred in isolation or in combinations.
It is these structural dissimilarities that present an atypical type of genetic risk than the more common sequence changes in letters of the genetic code that the scientists had been looking for
Calling them, "The best evidence yet that such deletions and duplications are linked to the disorder,” Doctor Thomas Insel, M.D. who is director of the National Institute Of Medical Health, states that these findings make the search for autism contributing genes more complex. Rare as these changes are, they are scattered across the genome and point towards autism being the end result for various genetic aberrations.
In their study, the findings of which were detailed in Science Express on Friday, March 16th, Dr. Jonathan Sebat and colleagues in the United States, Britain and Finland relate how they studied the DNA of people in 264 families. They employed new high resolution array technology to detect the changes found in a child but not present in either of the parents.
They also found that families having more than one affected member exhibited much lower rates of mutations than those with only one affected member. This prompted the researchers to consider the contributions of “two different genetic mechanisms”-inheritance and spontaneous mutation.
About one out of every 150 children is affected by autism. Diagnosed by the time a child is three, autism is associated with behavioral problems and trouble with social interaction.
Chairman of the department of psychiatry at New York's Columbia University Medical Center, Dr. Jeffrey Lieberman remarked however, that such work does not present an answer to perhaps the most significant question about autism- How and why are these genetic changes caused in the first place?
