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 , 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.
鈥淚t鈥檚 almost as if you were studying a neuron in the human brain,鈥� says , a neurobiologist at the University of California, Irvine, who developed the approach and has previously used Xenopus eggs to study epilepsy.
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Miledi鈥檚 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鈥檚 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鈥檚 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. 鈥淎utism spectrum disorder is a very broad range of maladies, with many different sources and many different problems,鈥� he says.
, 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鈥檚, 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: (DOI: 10.1073/pnas.0804386105)
