Scientists can't make puberty any less bewildering for teenagers -- cracking voices, acne and the growth of hair in peculiar places remain facts of life -- but at least they know a little bit more about what sets it off.

A research team headed by University of Pittsburgh physiologist Tony Plant has identified the gene that initiates the cascade of hormones that transforms young girls and boys into young women and men.

The gene is called KiSS-1, but don't let the name mislead you. The folks who named the gene years ago didn't have anything romantic or sexual in mind. Rather, KiSS genes produce kisspeptin proteins, some of which are known to fight tumors.

In research published in this week's online edition of the journal Proceedings of the National Academy of Sciences, Plant and his colleagues focused on KiSS-1 genes that reside in nerve cells found in the brain's hypothalamus. The kisspeptin proteins produced by these cells go on to bind to the surfaces of other neurons in the brain, causing those cells to produce gonadotropin-releasing hormone.

That hormone in turn stimulates the pituitary gland to release its own hormonal messengers, which ultimately kick sex hormone production into high gear.

Plant said he and his colleagues began to look at KiSS-1 after researchers in Paris and Boston -- including one of Plant's co-authors, William Crowley of Massachusetts General Hospital -- reported in late 2003 that children suffering from delayed or missing puberty had a defective gene known as GPR54.

That gene produces the cell surface proteins that are known to bind with the kisspeptin proteins. So Plant, Crowley and researchers at the Oregon National Primate Research Center had reason to focus on those proteins.

When injected into prepubescent, 15-month-old monkeys -- equivalent to 4- or 5-year-old boys -- kisspeptin proteins from the hypothalmus were able to stimulate pubescent changes. And the researchers also were able to visualize the neurons containing KiSS-1 gene in prepubescent and pubescent monkeys, noting whether the gene was activated or not.

Plant acknowledges that a significant piece of the pubescent puzzle is still missing: What turns on the KiSS-1 gene?

"That really is the $64,000 mystery," said Plant, director of the Pitt Center for Research in Reproductive Physiology. Perhaps it's some sort of time-keeping mechanism in the brain, or maybe it's something that tracks growth of the body.

Plant said his team hopes to find the answer, or at least another clue, by identifying which neurons actually produce kisspeptins and how they are controlled.