Next generation transposon vectors for genome engineering

Non-viral gene delivery systems are limited by their activity and targeted integration capability. Efficient and targeted integration of DNA into mammalian and human genomes remains a major challenge and its success would have wide impact for biotechnology and therapeutic applications. The piggyBac (PB) transposon system is the most active integrating non-viral gene delivery system and is a cut-and-paste DNA transposon that has been used for genome engineering of mammalian and human cells for more than 15 years. We have re-engineered the PB-transpososome (transposase with transposon DNA) based on the first- ever three-dimensional structure of the PB transpososome that we recently published with our collaborator Dr. Fred Dyda (Chen et al., Nature Communications, 2020). Our next-generation PB transpososome (ngPB) demonstrates greater activity and potential for targeted integration than was previously achievable. In specific aim 1, we will engineer and test ngPB for genome engineering of human cells. We will evaluate the integration site profile and copy number of transposon integrations per human cell. We will modify primary human T cells ex vivio and test their ability for cell therapy, and we will enable transposase protein transfection. In specific aim 2, we will engineer and test ngPB for gene delivery in vivo. We will evaluate gene delivery of reporter and therapeutic transgenes to mouse liver, test for efficiency in development of transgenic mice, and evaluate hybrid adeno-associated viral (AAV)-ngPB mediated gene delivery to difficult to reach organs. In specific aim 3, we will engineer and test ngPB for targeted integration in human cells. We will also map the protein-protein interaction domain of PB known to affect its target site selection in human cells and test PB protein modifications to allow greater flexibility in manipulating PB genomic target site selection. The proposed studies will be transformative for genome engineering and have broad impact for biotechnology and therapeutic applications.