Rodent of the Week: The magic of ovulation

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Four decades of research on infertility has yielded a lot of knowledge about the basics of human reproduction. But many mysteries still remain about this most fundamental aspect of biology. In a study published this week in the journal Science, researchers have moved a little closer to understanding how ovulation takes place.

During ovulation, an egg (or sometimes two or more eggs) are released from the ovary. But before this can occur, a series of finely tuned chemical actions must take place, according to the researchers from Baylor College of Medicine and UC San Diego. Working with mice, the scientists found that two proteins, called ERK1 and ERK2, are critical in fostering the maturation and release of the egg from the ovary. The mice used in the study lacked genes needed to produce ERK1 and ERK2 and were compared with mice that produced the proteins.

‘Ovulation results from a complex interplay of chemical sequences,’ Dr. Duane Alexander, director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, said in a news release. ‘The researchers have identified a crucial biochemical intermediary controlling the release of the egg.’ The study was funded by NICHD and the National Cancer Institute.

Here are the gory details: An immature egg is contained in a layer of cells, called granulosa cells. Each month, the brain releases follicle-stimulating hormone and luteinizing hormone that cause the egg and the granulosa cells to grow and mature. Later, the brain releases more luteinizing hormone that signals the follicle to rupture and release the egg. The new research shows that luteinizing hormone actually signals the release of ERK1 and ERK2. Those molecules direct the chain of events that allows the egg to be released.

In the big picture, this means that these two proteins can perhaps be manipulated to facilitate ovulation in women with infertility or to prevent ovulation as birth control. But researchers still need to identify other components in the intricate chemical sequence that makes up ovulation, said the study’s project officer, Louis V. De Paolo, chief of the NICHD Reproductive Sciences Branch.

-- Shari Roan