A Chinese laboratory has created genetically modified monkeys that show symptoms of autism.
The researchers say they are the closest animal model of the condition so far and should allow scientists to study the brain networks involved in autism as well as trial treatments, such as deep-brain stimulation.
'The monkeys show very similar behavior to human autism patients,' said Dr Zilong Qiu of the Institute of Neuroscience at the Shanghai Institute for Biological Sciences, co-author of the paper published in Nature. 'We think it provides a very unique model.'
There are thought to be at least 100 genes related to autism – a spectrum of disorders that involve difficulties interacting and communicating with other people. In this study, researchers focused on a gene called MECP2, which is associated with autism and a related neurodevelopmental disorder called Rett's syndrome.
The researchers created transgenic monkeys that could express this gene by infecting egg cells with a virus carrying the gene. They used these eggs to create embryos and transplanted into female monkeys, resulting in eight live births.
By studying the brains of stillborn monkeys, the researchers confirmed that they were expressing the MECP2 protein in their brains. Then, within a year, they observed behaviours among the genetically modified monkeys similar to autism in humans. The monkeys were running repetitively in circles and had less social interaction with their peers than wild-type monkeys. They also became stressed when the researchers stared them in the eyes.
Previously, animal models of autism have been mostly limited to mice, but have produced little insight into possible treatments because rodent brain structure is not sufficiently complex to mimic the human brain.
Scientists have also genetically modified monkeys to express genes associated with autism, but this is the first time they have been able to link these genetic changes to behaviour in the animals.
The research team says that the model is not intended to replace mice models but should help overcome some of the limitations of studying brain disorders in mice. They plan to carry out brain scans on the monkeys and to trial deep brain stimulation, like that used in Parkinson's disease. It could also be used to trial gene therapy, they suggest.
However, not all researchers are convinced that the model is a close representation of autism in humans, and this type of research raises issues more generally around animal welfare.
Professor Huda Zoghbi, whose lab at the Baylor College of Medicine discovered the MECP2 gene's link to Rett's syndrome, noted that the monkeys did not display all of the characteristic features of autism, such as seizures. 'I think we need to be cautious calling this a model … it does not quite accomplish that,' she told the MIT Technology Review.
But Dr James Cusack, research director at the UK charity Autistica, told the Guardian that developing animal models of autism has been a major challenge.
'It should always be remembered that people with autism vary in a number of ways, and autism itself is linked to a number of other conditions. With this in mind, developing a single animal model of autism may be difficult to achieve.'