Despite decades of research, there’s still so much we don’t know about autism, especially in regards to what causes it. An incredibly complex condition, research has been and continues to be challenging, and a lack of a decent primate model to study has been a major hurdle. But it looks like researchers could be getting somewhere, as a group at the Chinese Academy of Sciences has managed to engineer monkeys that display autism-like behaviors.
Not only were the monkeys less sociable and more anxious than normal, but their offspring even showed these traits, demonstrating that the social impairment was also heritable. According to the team, this study not only tells us that using primate models to research autism is indeed feasible – it could also help scientists towards an efficient way to study other brain disorders too.
Described in the journal Nature, the Beijing team created their transgenic monkeys by using a virus to transfer a human gene called MECP2 into egg cells of cynomolgus monkeys, or the crab-eating macaque. The idea was to model a disease called MECP2 duplication syndrome, a rare neurodevelopmental condition that shares symptoms with autism spectrum disorders. As the name suggests, it’s caused by a DNA duplication event on part of the X chromosome that carries the MECP2 gene, which is thought to play a key role in facilitating brain cell communication by maintaining the connections across which information flows.
After infecting the eggs, they were artificially inseminated and transferred to surrogate mothers, and all of the successful pregnancies resulted in offspring with the human gene. The team then observed the animals as they grew up, monitoring for any abnormalities and testing their cognitive and social abilities. Although in general they didn’t show impairments in cognitive function when compared with unmodified counterparts, marked differences in their behavior was observed.
Reminiscent of autism, the monkeys showed elevated levels of anxiety and spent less time interacting with peers. And by mapping out their movements within their cages, the researchers were able to see that they also displayed repetitive behaviors, repeatedly walking around in circles. Humans with autism often engage in repetitive behaviors and routines like rocking and head banging as a way to cope with life.
Last but not least, five offspring were produced from one of the male transgenic monkeys, all of which had the human MECP2 gene and showed increased levels of the protein it codes for in their brains. But most importantly, this generation also showed social defects, spending less time interacting with one another when placed in pairs as compared with controls. This tells us that the transgene is transmissible and ultimately affects the behavior of offspring in a similar way to that of the parent.
Hopefully, this pioneering study will not only lead to a greater understanding of autism and other neurodevelopmental disorders, but also help scientists develop and evaluate therapeutic strategies for these complex conditions.
