Issue date: 10/26/07 Section: News

Media Credit: Liz Rohde Professor Erik Jorgensen, professor of biology and scientific director of the Brain Institute, works in his lab in the Aline Wilmot Skaggs Biology Research Building on Oct. 19. Jorgensen worked with U biologists to manipulate worms to be attracted to worms of the same sex.

A new study on sexual orientation in worms suggests human sexual orientation might be controlled by mechanisms in the brain.

By manipulating circuits in a worm's brain that control behavior, U biologists were able to alter the sexual preferences of male and female worms to mirror the opposite gender. The females became attracted to their own sex. However, male worms that took on female characteristics were not attracted to other males, because the female worms in the species are not drawn to males either.

If a worm's sexual preference can be altered by adjusting circuits in the brain, is human sexual preference controlled solely by the brain as well?

U biology professor Erik Jorgensen led the study investigating worm sexual orientation. "When we started this, we thought there were specific cells in males only that were responsible for male behavior -- it's simply not true," he said.

The study found that cells existing in both male and female worms can be rewired to activate certain modes of behavior.

"You can take a female and activate the male genetic program -- if you do it in the entire female, it will even begin to look like a male," said Jamie White, a postdoctoral researcher in Jorgensen's lab.

The C. elegans nematodes used in Jorgensen's lab are transparent millimeter-long soil worms. Although male worms require females to reproduce, the "female" worms are actually hermaphrodites that produce both sperm and eggs. Jorgensen and White refer to the hermaphrodites as "females" because they reproduce independently.

Mating with males produces more offspring than when the hermaphrodites reproduce by themselves. The researchers took the hermaphrodites and altered neurons in their brains to give them male characteristics. The females became attracted to female pheromones, a scent female worms give off to attract male worms. C. elegans worms are blind and use their sense of smell as a way to find their mate.

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