Liu, H. et al. Cell Stem Cell 14, 323–328 (2014).

Models of human disease in nonhuman primates are of high interest in biomedicine, and targeted genome-editing technologies offer a way to realize this goal. In recent work, Liu et al. demonstrated the use of transcription activator–like effector nucleases (TALENs) to mutate the MECP2 gene in rhesus and cynomolgus macaques and thus to generate a primate model of Rett syndrome, an X-linked neurodevelopmental disease. The researchers used three TALEN pairs targeting the gene at different positions and delivered the nucleases to one-cell zygotes as plasmid DNA. They were able to efficiently modify the gene in embryos and did not detect any off-target effects. After implantation, male fetuses carrying MECP2 mutations were miscarried, as in humans. Female mutant monkeys were carried to term and, at the time of publication, had not yet presented a phenotype.