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Monkeys exhibiting symptoms linked to Rett syndrome have been genetically engineered by Chinese scientists, with the ultimate aim of gaining a deeper understanding of autism, in order to address it more effectively.
The controversial endeavor, presented on Tuesday, January 26 in the journal Nature, was led by neuroscientists at the Shanghai Institutes for Biological Sciences, and it involved breeding genetically modified macaques, suffering from MECP2-duplication syndrome, which is closely associated with another disease known as Rett’s syndrome.
That brain disorder, which predominantly affects female patients, manifests itself through stereotypical, purposeless movements, such as repetitive hand wringing, or other similar compulsive gestures involving mostly the upper limbs.
In addition, Rett syndrome results in gastrointestinal issues, seizures, impaired bowel movement, stunted growth, speech disorders, scoliosis and inability to walk (in around half the cases).
People who suffer from this disease also tend to have tinier feet and hands, and even microcephaly (smaller sized heads and brains).
Rett syndrome was previously considered a pervasive developmental disorder, according to the Diagnostic and Statistical Manual of Mental Disorders, due to similarities it shares with autism spectrum disorders.
Some of the manifestations the two neurological diseases have in common include: trouble making eye contact, difficulty reciprocating emotions and connecting with others, impaired body language, screaming tantrums, speech impediments, inconsolable weeping, urinary incontinence etc.
In 2013 Rett syndrome had its classification altered, but some researchers still believe that further insight into this condition could bring us closer to combating autism spectrum disorders more easily.
That is why Chinese scientists decided to replicate symptoms of this disease in laboratory conditions, starting from the premise that human beings suffering from Rett syndrome have mutations of the MECP2 gene.
They managed to breed more than a dozen macaques affected by MECP2-duplication syndrome, by using a lentivirus in order to inject monkey embryos with extra copies of that MECP2 gene.
The experiment proved to be a success, since by the time they turned 11 months, the animal subjects exhibited several obvious signs and manifestations associated with Rett syndrome.
For instance, they engaged in stereotypical compulsive behavior, such as moving around in circles, and also showed higher levels of anxiety, responding more strongly to stressors.
Furthermore, they had significant trouble maintaining eye contact, or interacting with their peers, preferring to spend more time on their own.
Appearance-wise, the macaques tended to suffer from developmental problems, experiencing difficulties when it came to reaching normal a normal weight, due to impaired fatty acid metabolism.
Given the fact that the monkeys had a wide array of symptoms linked to Rett syndrome, researchers are confident that their trial worked, although they do acknowledge that the disease may have different effects on these primates than on human beings.
For instance, the animals showed no signs of seizures, even though this is one of the most prevalent manifestations that Rett syndrome has.
Therefore, it may be that even treatment methods that are shown fruitful among macaques may not yield such promising results when tested on humans.
Even so, study authors are still hoping that scientists will now move away from experiments involving mice, and instead conduct other trials of this kind on monkeys, so that neurological disorders can be more carefully examined, and addressed more successfully, possibly by using CRISPR/Cas9 genome editing.
On the other hand, animal rights advocates have been criticizing this latest study, deeming it as overly cruel and of no value whatsoever.
Given that autism spectrum disorders are influenced by up to 100 genes and have just a few things in common with Rett syndrome, even if progress is achieved, it will only be of benefit to those suffering from this latter disease.
In addition, as opponents emphasize, some autistic people don’t even seek an actual cure for their condition, considering an integral part of their identity.
Allegedly, what these patients wish for is to be more easily accepted by their peers, and maybe more efforts should be concentrated in this area instead.
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