Finding new treatment options for pediatric high-grade gliomas is important because most children with glioblastomas die within a year of being diagnosed. Despite over 30 years of clinical research, little progress has been made, suggesting that we need to better understand the basic processes by which these tumors form to find more effective strategies for treatment. This project will investigate if the p53 gene has an elevated mutation rate during the development of pediatric high-grade gliomas. Inactivation of p53 by somatic mutation is an important step in the progression of many cancers, including glioblastomas. If p53 has a locally elevated mutation rate, it may explain why some children acquire cancer-causing mutations at a young age. Therefore, we will prove or disprove the p53 hypermutability hypothesis by directly measuring rare polymorphism in the p53 gene. The pooled-sample polony sequencing technology developed for this purpose could have a significant impact beyond the immediate goals of this project. The role of rare variants in common diseases is largely unknown. Pooled-sample polony sequencing should allow detection and quantification of rare deleterious alleles present in the human population. Furthermore, by sequencing large pools of cases and controls, it will allow the identification of disease-causing rare alleles, even those with low penetrance. Population-based sequencing will also allow us to find regions of the genome that are under selection without the need for alignment to the genomes of other species. Ultimately, this could enable the identification of sequences that are functionally constrained in humans, but not in other mammals. This would be particularly exciting because it would help us understand what features in the genome make us unique from other species.
The investigators have successfully used pooled sample sequencing to identify and quantify rare variants from a pool of 1111 individuals. They have validated their results using the "gold standard", Sanger sequencing and found excellent agreement. They will now begin to use this technology to understand the role of rare variants in disease.