Research points to two new genetic links that may predispose people to the developmental disorder that impairs the ability to form normal social relationships.
Autism has recently been implicated as a national public health crisis as one in 150 American children is diagnosed with an autism spectrum disorder. Affecting four times as many boys as girls, the diagnosis of autism has expanded tenfold in the last decade.
The new research stems from a scan of the world’s largest collection of DNA samples from families affected by autism. From the review, scientists discovered two new genetic links that may predispose people to the brain disorder.
The study is reported in the Feb. 18 online editionof Nature Genetics.
The five-year study was led by the Autism Genome Project, an international consortium involving scientists from 50 institutions in 19 countries. Founded in 2002 with funding from the nonprofit Autism Speaks and the National Institutes of Health, the group shared DNA samples, data and expertise in a coordinated effort to identify autism-susceptibility genes.
“This degree of collaboration is an unprecedented effort in autism research and demonstrates that a genetic approach is a powerful way to deepen understanding of the disease,” said Dr. Daniel Geschwind, director of the Neurogenetics Program at the Jane and Terry Semel Institute for Neuroscience and Human Behavior at UCLA, one of the study’s 13 research centers.
“This large-scale study reveals that autism is an extremely diverse condition,” Geschwind noted. “Our findings suggest that autism has numerous genetic origins, rather than a single or few major causes.”
The consortium used gene-chip technology to search for genetic commonality in autistic individuals from nearly 1,200 families. The scientists also scanned DNA from these families for variations in gene copy numbers — tiny genomic insertions and deletions that scientists believe might be involved with autism.
“The large number of families in this study permitted us to organize autistic children with similar features of this disorder into smaller groups, where gene linkages may be more easily detected,” observed Rita Cantor, professor of human genetics at the David Geffen School of Medicine at UCLA.
Results of the two-pronged approach implicated a previously unidentified region of chromosome 11; and neurexin 1, a member of a gene family believed to play a key role in communication between brain cells. The neurexin finding highlighted a group of brain cells called glutamate neurons and the genes affecting their development and function, suggesting that they play a critical role in autism spectrum disorders.
“We are excited by the results from this large-scale study,” said Dr. Stanley Nelson, professor of human genetics at the David Geffen School of Medicine at UCLA, “At the same time, we must greatly increase the number of autistic persons in our genetic analysis in order to fully describe heredity’s role in the disease.”
“We hope that identifying these genes will provide new insights into what underlies autism,” added Geschwind. “We are optimistic that this approach will lead to improved interventions for autistic children and better quality of life for their families.”
In 1997, the citizens’ group Cure Autism Now (CAN) created a gene bank in order to advance genetic research on autism. UCLA partnered with CAN to add more than 400 families to the gene bank, called the Autism Genetic Resource Exchange, which contributed one-third of the clinical data and samples analyzed by the Autism Genome Project in this study.
The UCLA families who participated had more than one member diagnosed with one of three genetically related diseases: autism, pervasive developmental disorder or Asperger’s syndrome. Earlier this month, CAN merged with Autism Speaks to pool their efforts to fund and advance autism research.
Autism is a complex brain disorder that strikes in early childhood, often as young as 2 or 3. The condition disrupts a child’s ability to communicate and develop social relationships, and is often accompanied by acute behavioral challenges. While the cause remains unknown, scientists suspect the disease is highly hereditary.