In an effort to better understand the effect of steroids on the human body, U researchers are finding out about the birds and bees…and fruit flies.
Steroids trigger maturation in all organisms from sixth-graders to fruit flies. There are dozens of steroids in advanced organisms, like human beings, but fruit flies only have one, ecdysone, said Carl Thummel, professor of human genetics and Howard Hughes Medical Institute investigator.
Flies are used in genetic research because they reproduce quickly and have a relatively simple genetic code.
Because they only have one steroid, they are a good model for understanding how steroids work in the human body.
It was previously known by geneticists that ecdysone induced metamorphosis, turning a larva into an adult insect. But the steroid is also present in the fly embryos.
Thummel and Tatiana Kozlova, a Howard Hughes research associate, say they wanted to understand why.
The glands that produce the steroid aren’t yet developed in an embryo. Thummel and Kozlova wanted to understand where the steroid was coming from and what it was doing in the embryo.
These questions have gone unanswered because of the technical difficulty of this kind of research, Thummel said.
Researchers were looking for a clue as to where to start, he said.
It came when they looked at where the steroid was active in the embryo. Because the steroid was everywhere in the embryo, it was assumed that it would be active everywhere. But that was inaccurate.
They found that the steroid molecules were attaching to receptor molecules in a specific area of tissue.
That specific area of tissue, called the amnioserosa, doesn’t actually form into any part of the fly, but it aids in the formation of the fly. It also supports the development of the embryo like a placenta, Thummel said.
Besides being surprised that the steroid was concentrated in that area, they realized that the tissue must be creating the steroid.
This made sense, according to Thummel, because the placenta-which connects the mother to the embryo in other organisms-is also a tissue that doesn’t form a part of the embryo, but aids in development and also produces steroids.
The researchers concluded that if the steroid triggers maturation and it is being produced by this tissue, it might be triggering the maturation of the embryo the same way it triggers metamorphosis.
By disrupting the steroid in the embryo, major development processes that turn the blob of embryo into a larva with segmented parts did not occur, confirming the steroids role, Thummel said.
Previously, researchers had no idea the embryo was dependent upon the steroid to become a larva, he said.
These kinds of studies enlighten genetic researchers about how steroids work in an organism.
The mechanical insights from these studies can be cross-applied to research that directly benefits humans, Thummel said.
But these insights into fruit flies can also aid in the development of better pesticides, Thummel said in a written statement.
The research was posted on the online version of Science magazine on Sept. 4 and will be published in the magazine next month.