no need to get e x cited, but in a major step towards understanding human baldness, American scientists have discovered a gene that appears to activate hair follicles in humans. They say that this will help them work out all the biochemical processes that lead to hair production. And ultimately, they hope, this new discovery will result in more effective remedies for hair loss.

Scientists know very little about hair growth in humans, and whatever they know comes mainly from studies conducted on animals. For instance, scientists know that sheep have more than 100 different genes of keratin, the structural proteins in their wool. And in mice and rats, genes such as the one called hairless are thought to make proteins that coordinate hair production. However, geneticists and biologists are still quite clueless as to how these genes work. "We have absolutely no clue on how the hair follicle functions,' confesses Andrew Leask, a biologist at a biotechnology company called FibroGen near San Francisco, usa .

In humans, the most common form of hair loss is male pattern baldness, which is thought to result from imbalances of hormones such as testosterone. Levels of the hormone appear to rise in balding men. Therefore, all drugs currently available to reduce hair loss operate by countering the effects of these hormones.

A much rarer genetic condition is one in which all body hair drops out. Called alopecia universalis , this disorder can strike men or women at any age. Angela Christiano and her colleagues at Columbia University in New York, usa , hoped to track down the genes responsible for this particular condition while trying to find a universal mechanism underlying baldness. "We were hoping that by focusing on the genes themselves, we could find out how hair is produced,' she explains.

In collaboration with Leask, Christiano's team set about trying to find the genes by studying a family in which 11 members lost all their hair. Those affected were born without eyebrows or lashes, and never developed pubic hair. Although the children had been born with a normal headful of baby hair, no new hair grew in to replace it.

The researchers report that they traced several common genetic markers in the bald members of the family. Coincidentally, Christiano had isolated the human version of the hairless gene that is found in mice and rats, and she noticed that it lies in the same region of the chromosomes as the markers she traced in her bald subjects. The team later found that each bald subject had a single mutation in the hairless gene.

Based on the sequence of the hairless protein, Christiano believes it is possibly a regulator of other genes