The research is published this week in the online early edition of Proceedings of the National Academy of Sciences.
Simcox began the analysis on a fruit fly larva that had recently hatched from the egg. She identified a tiny sac of cells representing where a future wing would be that was attached to the body cavity through tubing that runs the length of the larval body. Simcox dissected those sacs away from the body to study them specifically.
By staining the cell sacs with substances that light up target genes, the researchers then made images of the sequence of genetic events they observed. It all started with Dpp, part of a family of genes known as bone morphogenetic protein genes that are well understood in developmental biology.
The analysis showed that Dpp sent its signal from one cell layer to the other across the gap in the middle of the sac to activate the vn gene. The mechanism allowing the genes to talk to each other across that gap remains a mystery, Simcox noted.
"But it's the only explanation because if we took away the function of Dpp, vn doesn't get turned on," she said.
Dpp's activation of vn is the critical step in turning on its target, the Egfr signaling pathway, which sets off a series of gene activations that drive wing development specifically, activating genes called ap and iro-C. But vn also has the ability to regulate itself through a feedback loop so it stays on for longer in some cells where it is also needed for making the body of the fly at the location of the wing's attachment.
In addition to imaging the genes' activity, the researchers zoomed in on the gene structure to identify the binding sites that enabled the gene signaling to occur. When they mutated the binding sites, the signals were disabled.
"We had genetic evidence linking the events, tracing it back earlier th
|Contact: Amanda Simcox|
Ohio State University