Human-frog hybrids might reveal the neurological secrets of autism. By fusing cells from the preserved brains of deceased autistic patients with the eggs of a carnivorous African frog called Xenopus, scientists have started investigating the way the brain cells of people with autism behave.

The frog eggs work a little like human neurons and 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,” says Ricardo Miledi, a neurobiologist at the University of California, Irvine, who developed the approach and has previously used Xenopus eggs to study epilepsy.

Miledi’s earlier work has suggested that some brain cells of epilepsy patients have trouble sensing a molecule that helps damp down neuron activity. The proteins in question, called neurotransmitter receptors, sense the chemicals that neurons use to communicate, and Miledi thinks that problems with these proteins underlie epilepsy and other disorders


Some researchers blame autism on a malfunction in mirror neurons, cells that play a vital role in understanding the actions of others people.

To see if abnormalities in neurotransmitter signalling also underlie autism, Miledi’s team collected brain samples from six deceased autistic patients, aged eight to 39. They fused brain-cell membranes, which house neurotransmitter receptors, together with Xenopus egg membranes. As a control, they did the same thing with brain cells from patients with no history of mental disorder.

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

However, Miledi cautions that more research with additional samples will be needed 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, agrees that frog eggs could be useful for studying certain properties of autism, and perhaps uncovering new treatments.

He notes that other brain illnesses, such as depression and Parkinson’s, can be treated by turning the activity of neurotransmitters up or down. Hybrid frog eggs could perhaps hint at which neurotransmitters to tweak, he says.

Journal reference: PNAS (DOI: 10.1073/pnas.0804386105)