Generation of a rhesus macaque harboring a multivalent reporter for assessing gene editing outcomes.

Somatic gene editing therapies offer the potential for lasting treatments for a range of genetic disorders, with a host of therapies at various stages of clinical testing. The development of safe, effective therapies required relevant pre-clinical animal models capable of measuring on-target delivery and detecting off-target editing. Here we present the creation of a transgenic rhesus macaque encoding the Bivalent Enhanced Traffic Light Editing (BETLE) system, a multi-color fluorescent reporter that provides a simple readout for multiple modes of gene editing, including off-target effects. We used zygote microinjection and piggyBac transposase to generate preimplantation embryos that ultimately led to a healthy transgenic macaque. Extensive molecular analyses demonstrated single-copy integration of the intact reporter; however, the animal was mosaic, with only 5-8% of cells encoding the reporter, although all germ layers contained positive cells. The creation of this macaque provides important information to improve future transgenics, and progeny from this macaque could provide a powerful tool to evaluate the delivery and accuracy of gene therapies.