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USM students Jasmin Rocray (left) and Steven MacWhinnie survey various stages of caterpillar development. MacWhinnie is one of the coauthors in the Science paper. Behind them is their USM biological sciences Professor David Champlin, Ph.D.

USM Research Published in Science; New Growth Hormone Identified

June 2, 2006

Science, a widely-respected, international scientific journal of the American Association for the Advancement of Science, has just published an article describing research done at USM on insect hormones that can help in our understanding of human and animal growth, and help battle agricultural pests as well as insect-borne diseases.

The research may even help control caterpillars that eat your tomato plants.

The findings are also relevant in helping the medical community toward a better understanding of the role of hormones in normal development, stem cell research, cancer and other diseases.

In brief terms, the researchers have identified a hormone never before known that is responsible for initiating metamorphosis in caterpillars. The article in Science focuses on this new “starter hormone” and new roles for other well-characterized insect hormones.

The research was done, and the article authored, by USM assistant professor of biological sciences David Champlin, two of his students (Paul Allee of Portland, Maine, and Steven MacWhinnie of Gray, Maine) and three colleagues of Champlin’s who are professors from the University of Washington and Hirosaki University in Japan.  The research done at USM was funded by the National Science Foundation and the Bioscience Research Institute of Southern Maine.

Champlin says, “Imagine starting your car in the morning. Is it the gas that starts it? No. It’s a process beginning with the starter motor. The gas merely keeps the car running once it has started. And the brakes stop the car’s progress. These processes are all different, but related. With the caterpillar, many scientists have studied a hormone that causes metamorphosis to advance and another hormone that represses metamorphosis but have never really asked what starts metamorphosis.  When we did we found a new role for the repressor hormone and in the process identified a hormone never before known that starts metamorphosis.”

An important piece of the new study is that this “starter hormone” is regulated by nutritional cues in the caterpillar’s food.  Recent publications from Champlin’s research group complement the Science article and show in more detail how nutrition regulates the initiation of metamorphosis. 

The USM researchers found that by manipulating what the caterpillar eats they could create strange chimeras that were part caterpillar and part pupa.  For example, the chimeras had caterpillar mouths for plant chomping and also the nectar sipping mouth tubes of the moth.  Development of the antennae, legs, and eyes were also caught midway between what the caterpillar needs to survive to what a moth needs.  Although the chimeras didn’t survive because they couldn’t eat properly, they revealed yet another intriguing piece of this new story.  The relationship between the cells that form the caterpillar and those that will form the moth has not been described in detail before.  For example, the USM researchers found the cells that form the moth’s eye are actually skin cells in the caterpillar!  

Champlin says, “All of this is leading us to a better understanding of how hormones control growth in animals, including humans. This is also related to stem cell research and regenerative medicine – how to coax cells to change their fates.”

Champlin emphasizes that, “While the new results are fascinating, more rewarding for me are the research training and educational successes of the students who participated in the research, not only the co-authors on the current paper, but also a number of other USM students who did the important experiments leading up to the Science publication and also those who are continuing the work today.” Among those students are: Ben Smith, from Waterford, Maine, graduated from USM in May, 2004, and is now pursuing a Ph.D. in the Functional Genomics Program, University of Washington, Seattle; Sarah Hunter, from Caribou, Maine, graduated from USM in May, 2005, and is now a registered nurse in Portland, Maine; Chris Pelletier, from Clinton, Maine, graduated from USM in December, 2004, and is now pursuing a Ph.D. in the Vertebrate Organogenesis Program, University of Michigan, Ann Arbor; Elizabeth Fergusson, from Whitefield, Maine, graduated from USM in December 2005, and is now a research technician at Bates College, Lewiston, Maine; Matt Harris, from Biddeford, Maine, graduated from USM in August, 2005, and is now in medical school at the University of New England; Eric Cobbs, from Brunswick, Maine, graduated from USM in May, 2005, and is now working for a biotechnology firm in southern California.

The article in Science was published today, on June 2nd; it may be found at http://www.sciencemag.org/current.dtl#twis.

Prof. Champlin and the USM student researchers may be contacted for interviews, photos, tours of the laboratory where the work was done, as well as copies of the Science article and related publications from the USM research group. He may be reached at 207-228-8349 or champlin@maine.edu. Or you may contact the USM Public Affairs office at 207-780-4200.

ADDENDUM FOR SCIENCE EDITORS:

JUVENILE HORMONE IS REQUIRED TO COUPLE IMAGINAL DISC FORMATION WITH NUTRITION IN INSECTS

Abstract:

In starved larvae of the moth Manduca sexta, larval tissues stop growing because they lack nutrient-dependent signals but imaginal tissues cease growth because of suppression by juvenile hormone. Without juvenile hormone, imaginal discs form and grow despite severe starvation.   This hormone inhibits the intrinsic signaling needed for disc morphogenesis and does so independent of ecdysteroid action.  Manipulation of starvation and juvenile hormone treatments allowed the separation of intrinsic and nutrient-dependent aspects of disc growth and showed that both must be present during the early phases of disc morphogenesis for normal growth leading to typical sized adults.

Hormones involved in this research:

1) ecdysteroid

This is a steroid hormone that has been known for fifty years and is studied very heavily because it is an excellent model for how steroid hormones work in humans.  Ecdysteroid causes metamorphosis to advance but we found that this hormone has no role at the start of metamorphosis.

2) juvenile hormone

This is also been known for fifty years and is heavily studied.  This hormone modulates responses to ecdysteroid.  The Science paper reports a new function for this hormone in repressing the start of metamorphosis.

3) Metamorphosis Initiating Factor (MIF).  This is the new "starter" hormone we have identified.

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