There are a lot of bigger questions that can come out of studying one particular system in one particular animal.

Transforming a fruit fly from a crawling, eating-machine of a larva into a flying, reproducing adult might be like converting a VW Bug into the space shuttle. To support the dramatic differences in form and function, an enormous amount of re-engineering must take place under the hood, so to speak.

Some of that re-shuffling takes place in the fly's control center, its nervous system.

"In higher insects like Drosophila that undergo complete metamorphosis, you have completely different behaviors in the two stages, so you do have to have this massive reorganization and it needs to be timed correctly," said Lisa Marin, assistant professor of biology.

One example of this nervous system reorganization is the type of nerve cells produced in a brain structure called the mushroom body. Stem cells create three different types of neurons, depending on a fly's developmental stage.

In her research, Marin asks the question, "How does the mushroom body know when to switch from making the larval type of neurons to these later born types? Does it 'count' the number of stem cell divisions or neurons produced, or does it coordinate with the fly's developmental stage?" So far, she has demonstrated that a cue coming from outside the mushroom body triggers the switch when the larva has reached the appropriate stage. Marin's next step is to identify that hormonal signal.

Her work has implications for understanding both the evolution of insect nervous systems and general mechanisms of development.

"The work touches on a lot of interesting developmental questions, in addition to neuroscience questions, in terms of how cells control division, proliferation and specification," Marin said. "There are a lot of bigger questions that can come out of studying one particular system in one particular animal."

Posted Sept. 22, 2008

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