Article Date: 04 May 2006 - 8:00am (PDT)
Researchers at the University of Texas Southwestern Medical Center, Dallas, deleted the PTEN gene in parts of the brain of mice and found they exhibited autistic-like traits.
The researchers deleted the PTEN gene from parts of the hippocampus and the front of the brain. The hippocampus is an important part of the brain for memory, as well as for some other functions.
They found the mice exhibited deficits in social interaction. They were also much more sensitive to some stimuli which most mice would not normally be bothered with.
You can read about this study in the journal Neuron (May 4).
PTEN mutations in humans with autism spectrum disorders (ASD) have also been reported, although a causal link between PTEN and ASD remains unclear.
The author of the study, Dr. Luis F. Parada, said "The exciting thing about these mice is it helps us to zero in on at least one anatomic location of abnormality, because we targeted the gene to very circumscribed regions of the brain. In diseases where virtually nothing is known, any inroad that gets into at least the right cell or the right biochemical pathway is very important."
Physical evidence for the reason for sensory overload, a problem experience by people with autism, was visible in the mice with the PTEN gene deleted. Scientists noticed the nerve cells in their brains were thicker than they should be, they also had more connections to other nerves than would be the case in mice without the deletion of that gene.
The researchers were excited that this discovery, thicker nerve cells and more connections between nerves, may be the first discovery of the anatomical regions where things go wrong in autistic patients.
The scientists plan to try out drugs with these mice. The aim will be to find out whether their condition can be reversed.
The researchers observed the following behavioural differences between normal mice and the mice with the PTEN gene deleted:
- The PTEN deleted mice showed no interest in strange mice. Normal mice did.
- On being presented with both another mouse and an inanimate object, the normal mice would be more interested in the other mouse. The PTEN deleted mice showed equal interest in both.
- The normal mice, on being presented with new nesting material, would team up and start making a nest. The PTEN deleted mice would ignore it.
- Female PTEN deleted mice would not care for their young well, many of their young died.
- When placed in an open area the PTEN deleted mice became very stressed, unlike the normal mice.
- The PTEN deleted mice became very stressed when gently picked up by humans, the normal mice rarely became stressed.
- The PTEN deleted mice were much more stressed by sudden noises than the normal mice.
On the other hand, the PTEN deleted mice did not exhibit repetitive behaviour or movements, common among humans with autism.
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Written by: Christian Nordqvist
Editor: Medical News Today