Wet or dry? Scientists are closing in on the gene that controls earwax consistency.

Hot on the Trail of the Earwax Gene

That glop on the end of your Q-tip is more than just a sign of questionable hygiene, and now researchers are zeroing in on the gene that determines the consistency of earwax. Pinning down the gene's location could lead to a surprising range of advances--from curtailing body odor to predicting breast cancer.

Earwax is made by apocrine glands that line the ear canal. Caucasians and people of African descent generally have "wet" earwax--a brown sticky goop--whereas Asians and native Americans usually have gray brittle flakes. The same glands in the armpit and genital region ooze an oily compound that ferments and provides a feast for stink-producing bacteria. In addition, breasts are giant modified apocrine glands. Too much apocrine tissue contributes to chronic breast cysts, and some researchers have proposed that a woman's earwax might contain clues about her risk of breast cancer.

Researchers led by Norio Niikawa at the Nagasaki University School of Medicine in Japan first realized that they could pinpoint the earwax gene while studying a form of inherited epilepsy. Japanese families with the disorder had wet earwax--highly unusual in Asians. The team gathered DNA samples from nine families. By figuring out which bits of DNA were shared by those with sticky earwax, the researchers narrowed down the gene to a region on chromosome 16. They report the finding in the 8 June issue of The Lancet. Although that stretch of DNA could hold a couple hundred other genes, team geneticist Hiroaki Tomita predicts they will have the gene in hand within the year. Because wet earwax, body odor, and breast tissue seem to be related, the earwax gene "may control general apocrine gland development," he says.

"I'm delighted they're close to finding the gene," says epidemiologist Nicholas Petrakis of the University of California, San Francisco. He says that the properties of apocrine glands--and therefore variety of earwax--corresponds to the risk of breast cancer. A genetic test could be more accurate than simply looking at earwax, which can be misclassified. Learning how the glands develop by studying the gene will help assess breast cancer risk in women, Petrakis says.

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Posted in Biology