Fruitflies and humans have more in common than might be thought. To start with, we share the same general digestive structures: mouth, esophagus, a stomach-like region, as well as small and large intestines. Recent research has only added to the list of similarities.
Looking at the guts of drosophila, Benjamin Ohlstein and Allan Spradling, of the Department of Embryology at the Carnegie Institute, discovered that fruitflies have stem cells in their intestines. They also observed details of the cells' molecular functioning that give us a greater understanding of stem cells.
Drosophila is a model organism. Its genome is mapped. It's simple enough that turning genes on and off, one by one, can test impacts on stem cell processes.
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The researchers found that fruitflies use Notch signaling, a gene-regulatory pathway, to generate new cells, as well as to regulate the differentiation of cells. This parallels what was known to occur in vertebrates. They observed that the Notch signal was controlling the rate at which the stem cells divided, something that hadn't been observed before.
"Now that it has been seen here, it is something that can be looked for very specifically in vertebrates," said Spradling.
The article, published in a December 7th online paper for Nature included a number of new findings. It was thought that fruitflies had relatively stable cells lining their guts. Ohlstein and Spradling's three-year project discovered that fruitflies, like humans, continually slough the lining of their intestines, replacing it completely every week. And again, like humans, drosophila use stem cells to regulate the replenishing of the cells lining their guts.
In vertebrates we are aware of the presence, and general location, of the few stem cells in the gut; unfortunately, they are indistinguishable from other cells.
"It isn't possible to point to a specific cell and say 'that is a stem cell,'" said Spradling.
In fruitflies, the small intestine alone has 800 to 1,000 stem cells, and they are differentiated in such a way that they can be identified, marked and tracked through generations of the cells. This research on fruitflies is much faster and cheaper than it would be in vertebrates, and may greatly aid investigations into stomach cancers and digestive disorders in humans.
Dr. Spradling points out that there are many diseases of digestion that are barely understood. He added that it is hard to know what the impact of the findings will be. But because stem cells control the production and differentiation of so many cells in the digestive system, understanding them will, likely, prove essential.
"When you learn something this basic there are many ways it can end up influencing human medicine," Spradling said.