Eukaryotic messenger RNAs (mRNAs) are extensively chemically modified to create non-canonical bases that can impact their fate and function in cells. The full collection of RNA modifications in cellular mRNAs, the epitranscriptome, represents a previously unappreciated layer of gene regulation. RNA modifications clearly have an important role in health and disease; many RNA modifying enzymes have been associated with a wide range of human diseases, particularly neurodevelopmental disorders and cancer. Why and how these small chemical changes in mRNA lead to those diseases is still largely unknown. Our goal is to connect molecular functions of RNA modifications to normal and disease traits using innovative high-throughput sequencing methods, RNA biochemistry and model systems. We aim to uncover the molecular basis of inherited neurodevelopment disorders and cancer phenotypes resulting from dysregulation RNA modifying enzymes and reveal targets for therapeutic intervention.