Dr. Stephen Scherer

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When the Human Genome Project came to an end in 2004, many believed the effort to map humanity's genetic information was complete. Armed with this new information, some researchers concluded that human beings were 99.9% DNA identical. However, later in 2004, another research team, looking at human DNA for a different purpose released findings suggesting we could be at least ten times more different than previously thought. Further research suggested links between these variations and disease.

The team that made the finding about genetic variation was studying chromosomes, tightly coiled groups of genes. Traditional thinking held that the chromosome pairs would contain only two copies of each gene, one on the maternally-inherited and one from the paternally-inherited chromosomes. But, newly-discovered variations in the structure of chromosomes revealed that all of us could inherit sometimes one, zero, or three or more copies of genes, a phenomenon called Copy Number Variation (CNV).

"There were some new technological advances that allowed us to look at DNA in a different (dimensional) way. Instead of there being only two copies, one from Mom and one from Dad, you might have variations on that number" comments Dr. Stephen Scherer of the Hospital for Sick Children's Center for Applied Genomics in Toronto who co-discovered the presence of genome-wide CNVs with international colleagues.

The insight turned genetic thinking on its head and sent researchers scrambling to understand the impact of CNV on the human genome. This fundamental discovery also led Dr. Scherer in another research direction to determine how variation in gene copies is linked to disease. One area of focus is autism spectrum disorders.

Using a powerful technology that allows detailed study of the interactions and activities of numerous genes and genetic sequences, Dr. Scherer's team has found that about 7% of autism cases they have examined are related to CNV differences not found in the general population.

Dr. Scherer is now working with collaborators across Canada to gather DNA from children who are developmentally delayed. The genetic information is stored in a database and checked for CNVs. "The early results are that in upwards of 20% of these cases we can actually ascribe a new CNV in the children not found in parents to be a likely cause of the developmental problems in that individual. It's quite a high yield and we're quite excited by the data."

In the future, Dr. Scherer says, an individual patient's genes could be scanned to check for CNVs and then customize their drug therapy.

"We need to understand the natural variation in all of our genomes," says Dr. Scherer, "but then also in some cases these variants will also be involved in disease and that's what we're searching for in our CIHR-funded studies."

This study by Dr. Scherer's team is funded by a partnership involving the Canadian Institutes of Health Research, GlaxoSmithKline Inc., and Rx&D, a national association of Canada's Research-Based Pharmaceutical Companies.

"There were some new technological advances that allowed us to look at DNA in a different (dimensional) way. Instead of there being only two copies, one from Mom and one from Dad, you might have variations on that number"