There are more than 6,000 rare diseases caused by mutations in a single gene; together they affect more than 500,000 Canadian children. Exactly what gene is causing a disease is unknown in more than half the cases. RNAseq may provide a strategy for discovering novel genetic mutations that cause rare diseases – but can’t be used without obtaining the specific tissues in which the disease is present. Drs. James Dowling and Michael Brudno, of The Hospital for Sick Children will use ex vivo disease models created at Sick Kids in place of tissue biopsies to perform RNAseq for gene mutation discovery. By combining recent advances in cell biology, genomics and bioinformatics, the lab will develop a new diagnostic methodology, fundamentally transforming the clinical diagnostics process.