Prototype mouse models for researching SEND-based mRNA delivery and gene therapy

One of the major challenges of gene therapy—an approach to treat diseases caused by faulty genes—is a lack of technologies that deliver healthy gene copies to target tissues and cells. Some commonly used approaches include viral vectors or coating therapeutic nucleic acids with lipid-based nanoparticles to pass through cell membranes, but these technologies have had limited success. A revolutionary tool, the CRISPR–Cas gene-editing system, offers tremendous promise, but it too suffers from problems with delivery. Another tool, called ‘SEND’ (for ‘selective endogenous encapsidation for cellular delivery’), seems to offer a better solution. The SEND system uses endogenous genetic components to package mRNA cargoes to deliver them to other cells via virus-like particles (VLPs). The SEND-VLP tool has enormous potential as a gene-therapy tool, if the endogenous components of SEND can be repurposed to produce VLPs containing therapeutic cargoes. However, several aspects of this newly identified phenomenon are not yet fully understood. Genetically engineered mouse (GEM) models, expressing different combinations of SEND components in a controllable and inducible fashion, could serve as valuable tools to understand more about this tool and to repurpose it for gene-therapy applications. In this Perspective, we discuss how GEM models and mouse molecular genetics tools could be used for SEND-VLP research.