World’s Largest DNA Scan For Familial Autism Points to Two Genetic Links

Lisa C. Routh, M.D.

2007

Preliminary results from the world’s largest collection of DNA samples from families that are affected by autism have given researchers insight into two genetic links they believe might predispose individuals to the brain disorder.

Researchers believe a previously unidentified region of chromosome 11, along with neurexin 1, a member of a gene family believed to play a key role in communication between brain cells, is linked to autism. They noted that the neurexin finding highlighted a group of brain cells called glutamate neurons and the genes affecting its development and function, suggesting that they play a critical role in autism spectrum disorders.

The results came after a five-year study led by the Autism Genome Project, an international consortium that included scientists from 50 institutions in 19 constries who gathered to share DNA samples, data, and expertise in an effort to identify autism-susceptibility genes in families. The consortium was founded in 2002 and is funded by the nonprofit organization Austism Speaks, as well as the NIH. Their findings were reported in the March Nature Genetics.

“This degree of collaboration is an unprecedented effort in autism research and demonstrates that a genetic approach is a powerful way to deepen the understanding of the disease,” said Daniel Geschwind, MDS, PhD, Director of the Neurogenetics Program at the Semel Institute for Neuroscience and Human Behavior at the University of California, Los Angeles (UCLA), which served as one of the study’s 13 research centers. “This large-scale study reveals that sutism is an extremely diverse condition. Our findings suggest that sutism has numerous genetic origins, rather than a single or few major causes, “ said Dr. Geschwind.

Relying on gene-chip technology, the researchers were able to search for genetic commonality in people with autism in nearly 1,200 families. The researchers also scanned DNA from these families for variations in gene copy numbers, which are tiny genomic insertions and deletions that scientists believe are linked with autism.

Efforts to assemble families began in 1997 when the citizens’ group Cure Autism Now (CAN) created a gene bank to advance genetic research on autism. Soon thereafter, UCLA partnered with CAN to add more than 400 families to the gene bank, known as the Autism Genetic Resource Exchange, which contributed one third of the clinical data and samples analyzed by the Autism Genome Project for this study.

Researchers said the next step will be to increase the number of autistic persons in the genetic analysis to trace heredity’s role in the disease.

Reference: NeuroPsychiatric Reviews March 2007