Now Human-Frog Hybrids to Study Autism

by Rajashri on Jul 23 2008 3:07 PM

The interaction of brain cells of among autistic people is being studied by fusing cells from the preserved brains of deceased patients with the eggs of a carnivorous African frog called Xenopus by scientists at the University of California, Irvine.

The researchers say that frog eggs work a little like human neurons, and that the hybrid cells act as a surrogate of a living brain with the condition.

"It's almost as if you were studying a neuron in the human brain," New Scientist magazine quoted Ricardo Miledi, a neurobiologist who developed the approach and has previously used Xenopus eggs to study epilepsy, as saying.

A previous study led by Miledi suggested that some brain cells of epilepsy patients have trouble sensing a molecule that helps damp down neuron activity.

Miledi said that the proteins called neurotransmitter receptors sense the chemicals that neurons use to communicate.

With a view to determining whether abnormalities in neurotransmitter signalling also underlie autism, the researchers collected brain samples from six deceases autistic patients, aged eight to 39.

The brain-cell membranes, which house neurotransmitter receptors, were fused with Xenopus egg membranes.

The researchers also did the same with brain cells from the people who were not mentally ill.

Miledi's team then doused the frog eggs in neurotransmitter chemicals, and measured the voltage generated within each egg.

They observed that the neurotransmitter chemicals tell brain cells to pump charged molecules in and out the membrane, creating a voltage across the membrane.

Since Xenopus eggs do not respond to the neurotransmitters, the human proteins are completely responsible for any electric current generated.

Four of six autistic brains responded to neurotransmitters chemicals less vigorously than the controls.

Miledi, however, cautions that further study on additional samples would be required to firm up any conclusions.

"Autism spectrum disorder is a very broad range of maladies, with many different sources and many different problems," he says.

Jonathan Pevsner, a neurobiologist at Kennedy-Krieger Institute in Baltimore, Maryland, also believes that using frog eggs for studies may be helpful in understanding autism in a better manner, and in uncovering new treatments for the mental disorder.

Pointing out that other mental illnesses like depression and Parkinson's could be treated by turning the activity of neurotransmitters up or down, he said that hybrid frog eggs could perhaps hint at which neurotransmitters to tweak.

A report describing the new study has been published in the journal PNAS.