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Deafness gene has health benefit

May 8, 2006 By Alison Abbott This article courtesy of Nature News.

Protein from genetic mutation helps wounds to heal.

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Researchers have concluded that a gene responsible for most cases of hereditary deafness may have an unexpected benefit: it may protect you from infection.

Stella Man, a member of David Kelsell's team at Queen Mary, University of London, spoke at the European Society of Human Genetics meeting in Amsterdam today, 8 May. She announced that the Cx26 protein encoded by a deafness gene might help wounds to heal.

Faster healing should help to prevent infection, for example by limiting bacteria's access to the blood after surgery, she says. "It's speculation, but maybe the Cx26 deafness mutations have been selected owing to their beneficial effects on wounds."

Local trade-off

Kelsell identified the link between the Cx26 gene and deafness almost a decade ago1. Mutations of the gene are surprisingly common in all populations, from Africa to Europe and Asia, he says, but cause deafness only in those who inherit a mutated gene from both parents.

A high frequency of mutation in any gene implies that there may be an evolutionary benefit for carriers. "It is well known that various genetic mutations that cause sickness in particular geographical areas sometimes also protect against local diseases, so there is a trade-off," says Kelsell.

The genetic mutation associated with sickle-cell anaemia in people of African descent, for example, gives some protection against malaria, which is endemic in the continent.

But to find a mutation that has penetrated so deeply into all populations is unusual, says Kelsell. "We reasoned that if it has a beneficial effect at all it must be a very general one — it must to protect against all sorts of diseases, not just local ones."

On the surface

The team suspected the mutation might benefit the skin, in part because the skin is a very general protector against all sorts of pathogens, and also because mutant Cx26 protein sometimes causes skin disease.

In addition, a team of German and Ghanaian researchers had reported that the skins of people with one or two mutated copies of Cx26 are thicker than those of people with normal genes2. This probably presents a stronger mechanical barrier to pathogens. Kelsell's team decided to investigate in more detail.

More than skin deep

Cx26 is a member of the connexin family of proteins. These proteins are the main components of special channels called gap junctions that link cells and allow them to communicate.

The researchers looked at the Cx26 protein in skin cells grown in the laboratory, to which they were able to add a mutated version of Cx26. When they added the aggressive bacteria Shigella to the cultures, cells containing the mutant gene were invaded by fewer bacteria.

They also found that, compared with normal cells, cells containing the mutant gene moved more rapidly around a Petri dish; such movement is a characteristic feature of cells involved in rapid wound healing.

The discovery is interesting not just for its insight into the preservation of the Cx26 mutation; it may also have pharmaceutical benefits. Man told the meeting that a drug developed to temporarily knock out normal Cx26 could be useful in improving wound healing.

The scientists now plan to test the effect of Cx26 mutation in other cell types, such as those in the lining of the gut, where defence against infection is also important.

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References

  1. Kelsell D. P., et al. Nature, 387. 80 - 83 (1997).
  2. Meyer C. G., et al. Nature Medicine, 8. 1332 - 1333 (2002).

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