Episomes and Transposases—Utilities to Maintain Transgene Expression from Nonviral Vectors

Abstract

The efficient delivery and stable transgene expression are critical for applications in gene therapy. While carefully selected and engineered viral vectors allowed for remarkable clinical successes, they still bear significant safety risks. Thus, nonviral vectors are a sound alternative and avoid genotoxicity and adverse immunological reactions. Nonviral vector systems have been extensively studied and refined during the last decades. Emerging knowledge of the epigenetic regulation of replication and spatial chromatin organisation, as well as new technologies, such as Crispr/Cas, were employed to enhance the performance of different nonviral vector systems. Thus, nonviral vectors are in focus and hold some promising perspectives for future applications in gene therapy. This review addresses three prominent nonviral vector systems: the Sleeping Beauty transposase, S/MAR-based episomes, and viral plasmid replicon-based EBV vectors. Exemplarily, we review different utilities, modifications, and new concepts that were pursued to overcome limitations regarding stable transgene expression and mitotic stability. New insights into the nuclear localisation of nonviral vector molecules and the potential consequences thereof are highlighted. Finally, we discuss the remaining limitations and provide an outlook on possible future developments in nonviral vector technology

A Simple Nonviral Method to Generate Human Induced Pluripotent Stem Cells Using SMAR DNA Vectors

“…S/MARs coordinate both transcription and genomic replication [25]. Adding an S/MAR sequence to a plasmid vector can keep the vector episomal, leading to stable and inheritable transgene expression without genomic integration (reviewed in this Special Issue by Kreppel and Hagedorn,[26]). We refer to genetic constructs harbouring an S/MAR sequence as SMAR vectors.…”