Many studies have traced the history of families with more than one autistic member, but few scientists have attempted to crack the code of sporadic autism —which arises unexpectedly in a formerly unaffected lineage and is more common than inherited autism. Now a group at Cold Spring Harbor Laboratory believes it has found a distinct mechanism by which autism can strike sporadically.
Led by Jonathan Sebat and Michael Wigler, the team examined the entire genomes of more than 150 families with at least one autistic member. They scanned for new genetic mutations, comparing any findings with parental DNA to assure the variation was not inherited and therefore truly sporadic.
They found that sporadic autism sufferers had a higher incidence of copy number deletions —regions where segments of DNA had been spontaneously deleted —than healthy subjects or people who inherited autism.
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The researchers estimate that these random DNA deletions, ranging from one to 69 genes in size, most likely contribute to mental illness in at least 15 percent of all autism patients. That proportion could rise as developing technology allows the group to find previously undetectable genetic alterations.
Now that these large-scale mutations have been identified, the Cold Spring Harbor group and other researchers can begin investigating individual genes within the target region.
Having already used this method to pinpoint cancer genes, the team is currently turning its eye to schizophrenia. Ultimately, the findings may elucidate how these afflictions arise and provide early detection tools so that treatment can begin sooner and be more effective.
