Neuroscientists at the Shanghai Institutes for Biological Sciences attempted to copy Rett syndrome, a disorder in humans who have too many copies of the MECP2 gene, by using a virus to inject copies of the gene into monkey eggs during fertilization. Using this method, they were able to breed over a dozen monkeys with the disorder. The monkeys that have gone through this process experience a range of health and psychiatric issues — some of them pace in circles and avoid interacting with other monkeys, some become visibly stressed when researchers stare them in the eyes, and some have even developed severe illnesses associated with their particular gene defect.
While the lead researcher, Zilong Qiu, is calling the results a victory, he admits that the monkeys aren’t a perfect model for humans with Rett syndrome. Some of the behaviors they exhibit, like pacing, aren’t found in humans with this form of autism, and some of the more serious complications patients can experience, like seizures, haven’t appeared in the monkeys at all. It’s hard to see how these monkeys would work as test subjects for human therapies when the disorder manifests in such different ways in each species.