New Pieces in Autism’s Genetic Puzzle Discovered

An international group of scientists identified a chromosomal region that may provide new leads towards a better understanding of the genetic basis of autism - a severe neurodevelopmental disorder afflicting as many as 1 in 165 Canadian children. Although it is generally agreed that a strong genetic basis underlies the condition, the causes of autism are still unknown. The completion of this study is a milestone event in furthering our understanding of autism. It builds on existing autism genetics research, brings scientists much closer to identifying susceptibility genes for the most common forms of autistic disorder, potentially providing improved treatment and even diagnostic tools.

 CAMH’s Dr. John Vincent worked with a team of 136 researchers from nine countries as part of the Autism Genome Project.  This group shared their resources, making it possible for the team to analyze DNA from approximately 1,600 families, performing the largest autism linkage scan (i.e. tested enough genetic markersto query the entire genome) to date. The team also analyzed variations of large pieces of DNA, or copy number variations (CNVs), in these families.

This linkage analysis enabled the team to implicate a previously unidentified region of chromosome 11, while the CNV analysis identified neurexin 1 (a member of a family of genes believed to be important in neuronal contact and communication), among other regions and genes in the genome. The neurexin finding highlights a group of neurons - glutamate neurons – and the genes affecting the neuron’s development and function.  This finding suggests that neurexins play a critical role in autism spectrum disorders, in some individuals.

Dr. Vincent will continue to play a role in the Autism Genome Project, as researchers work on this global scientific effort to map the genes responsible for causing autism.

Through his work at CAMH, Dr. Vincent is also taking a different approach to understanding autism. In a preliminary study using large families with autism in Pakistan, Dr. Vincent and colleagues are treating autism as a single gene disorder in each separate family.

They hope to learn from unique features of the population they are studying. In many families in Pakistan intra-family marriages are very common. This means that if there is a genetic abnormality, it may be present in both mother and father, and then inherited twice, i.e. one copy of the abnormality inherited from the mother and one from the father, in some of their children. As a consequence, rare recessive diseases can recur with high frequency within the family.

Dr. Vincent hopes that by studying this genetically unique population, his team will find enough evidence to identify a specific autism gene or genes, or to narrow down the region of investigation to a small part of one chromosome. They could then combine this family data with existing information from other lines of research to identify a new gene in a specific region.

Visit Using Genetics to Unlock Autism's Mysteries for more information on Dr. Vincent’s work at CAMH.

More information on the recent work from the Autism Genome Project is available from Nature Genetics at: Mapping autism risk loci using genetic linkage and chromosomal rearrangements

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