Zebrafish enable scientists to study the migration of neurons that enable sexua...( Scientists are watching a small grou...),Health

Scientists are watching a small group of neurons that enable sexual maturity and fertility make a critical journey: from where they form, near the developing nose, to deep inside the brain.

They believe their studies in the transparent embryo of the zebrafish will help explain why some neurons don't make it and enable better ways to help children who don't sexually mature as a result.

"They can go to the right place but take too long; delayed puberty suggests they got there late," says Dr. David J. Kozlowski, developmental geneticist in the Medical College of Georgia Schools of Medicine and Graduate Studies. "They can go to the wrong place. They can go to the right place and make the wrong connections, or not enough of them go to the right place. All sorts of things can go wrong and result in clinical defects."

Fortunately puberty problems due to central nervous system abnormalities are relatively rare, affecting about 1 in 40,000 females and 1 in 10,000 males, but they can be traumatic, says Dr. Lawrence C. Layman, an expert on delayed puberty who follows about 350 of these patients. Improved understanding and treatment could help scores of others as well by improving birth control and fertility treatments, he says.

To study one of the first things that can go wrong, Dr. Kozlowski, director of the Transgenic Zebrafish Core Laboratory, has teamed with Dr. Layman, chief of the Section of Reproductive Endocrinology, Infertility and Genetics in the MCG School of Medicine, and Dr. Nancy L. Wayne, reproductive neuroendocrinologist at the University of California, Los Angeles.

Boys typically begin puberty by age 10 or 11 and girls by age 8 or 9, when the hypothalamus in the brain begins releasing more gonadotropin releasing hormone, or GnRH, Dr. Layman explains. GnRH stimulates the pituitary gland to make follicle stimulating hormone and luteinizing hormone, which prompt ovaries to produce estrogen and eggs and
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