Scientists find 'itch gene'

Scientists have identified the first "itch gene", ending years of head scratching over what causes the maddening sensation.

The discovery of the gene within the spinal cord is expected to lead to new treatments for chronic and severe itching.

Non-stop itching is a severe problem which can be caused by skin disorders like eczema, or deeper problems such as kidney failure or liver disease.

It can also be a side effect of cancer therapies, or powerful painkillers. Some sufferers are so badly affected they cannot sleep, or scar themselves by scratching. Historically, scientists have regarded an itch as merely a less intense version of pain.

Study leader Professor Zhou-Feng Chen, from Washington University School of Medicine in St Louis, US, said: "Many genes have been identified in the pain pathway, but itch research has lived in the shadow of pain research, and no-one knew which gene was responsible for itching in the brain or spinal cord until now."

The culprit was identified as GRPR (gastrin-releasing peptide receptor). The gene provides the manufacturing instructions for a receptor protein on the surface of spinal cord nerve cells which responds to itch signals from the brain.

Originally the scientists were looking for pain genes. They were disappointed to find that removing the GRPR gene from laboratory mice did not alter their reaction to pain. But when normal mice were injected with a chemical that stimulates the GRPR protein, they started frantically scratching themselves.

"That's when we thought the gene might be involved in the itch sensation," said Prof Chen.

The researchers went on to study the behaviour of both normal mice and "knockout" animals genetically bred to lack a functioning GRPR gene.

Normal mice scratched vigorously when exposed to a variety of itch-producing substances, while knockout mice scratched much less. "The fact that the knockout mice still scratched a little suggests there are additional itch receptors," said Prof Chen. "We know of some proteins that are similar to GRPR, so now we're trying to determine if there is functional redundancy in the itching pathway."

Share this article

Send this article to a friend »

• Del.icio.us
• Digg
• Reddit
• Facebook
• StumbleUpon

What are these?