June 9, 2011

Genetic Abnormalities Contribute To Autism

Three papers being published on June 9 in the journal Neuron provide new insight into the diversity of genetic abnormalities that contribute to autism.

Two separate research groups searched for "copy number variants" in genetic samples from over 1,000 autism spectrum disorder (ASD) families that were recruited as part of the Simons Simplex Collection project. 

The researchers compared DNA from affected and unaffected siblings using distinct versions of a sensitive and powerful genetic screening technique.

"We observed a higher incidence of de novo (new) CNVs in children with ASD than their unaffected siblings," Dr. Michael Wigler from Cold Spring Harbor Laboratory who led one of the studies said in a press release.

"The functions of the genes in the regions of de novo variation point to a great diversity of genetic causes, but also suggest functional convergence. In addition, our results show that, relative to males, females have a greater resistance to autism from genetic causes, which raises the question of the fate of female carriers."

Dr. Dennis Vitkup of Columbia University headed up a companion study.  The CNVs identified in Dr. Wigler's study were analyzed using a new method, which revealed that the affected genes are part of a large network involved in the development of synapses.

Another collaborative study led by Dr. Matthew W. State from Yale University identified six rare recurrent de novo CNVs and found a significant association of ASD with de novo duplications of a chromosomal region that causes Williams-Beuren syndrome. 

"Finding strong evidence that at one position in the genome increases in the genetic material lead to ASD, while losses at precisely the same region lead to a highly social personality, was particularly exciting. This relatively small genomic interval clearly holds important clues to understanding the social brain," Dr. State said in a press release.

Identifying these mutations in individuals affected by autism may eventually allow researchers to design customized drug therapies that can take on the roles of the damaged genes.

"These studies are the culmination of a several-year effort to understand the role of genetic variants in autism," Gerald Fischbach, scientific director at the Simons Foundation, which funded the State and Wigler studies, said in a statement. "The microarray studies have shown beyond doubt that there are indeed rare genetic variants that account for a significant fraction of autism."


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